7/29/2019 te_1100_prn

1/103

IAEA-TECDOC-1100 XA9952141

Survey of wet and dryspent fuel storage

INTERNATIONAL ATOMIC ENERGY AGENCY /A>July 1999

3 0 - 3 8

7/29/2019 te_1100_prn

2/103

The originating Section of this publication in the IAEA w a s :Nuclear Fuel Cycle and Materials SectionInternationalAtomic Energy AgencyWagramer Strasse 5

P . O . Box 100A-1400 Vienna, Austria

The IAEA does not normally maintain stocks of reports in this series.However, copies of these reports on microfiche or in electronic form can be obtained fromIMS ClearinghouseInternational Atomic Energy AgencyWagramer Strasse 5P.O.Box 100A-1400 Vienna, AustriaE-mail: CHOUSE@IAEA.ORGU R L : http://www.iaea.org/programmes/inis/inis.htm

Orders should be accompanied by prepayment of Austrian Schillings 100-in the form of a cheque or in the form of IAEA microfiche service couponswhich may be ordered separately from the INIS Clearinghouse.

SURVEY OF WET AND DRY SPENT FUEL STORAGEIAEA, VIENNA, 1999IAEA-TECDOC-1100ISSN 1011-4289

IAEA, 1999Printed by the IAEA in AustriaJuly 1999

7/29/2019 te_1100_prn

3/103

FOREWORDSpent fue l storage is one of the important stages in the nuclear f ue l cycle an d stands amongth e most vital challenges for countries operating nuclear power plants. Cont inuous attention isbeing given by the IAEA to the collection, analysis an d exchange of information on spent fue lmanagement. Its role in this area is to provide a for um for exchanging information and for co-ordinating an d encouraging closer co-operation among Member States. Spent f u e lmanagement is recognized as a high priority IAEA activity.In 1 9 9 7 , the annual spent f ue l arising from al l types of p ow er reactors worldwide amounted toabout 10 500 tonnes heavy metal (t H M ) . T he total amount of spent f u e l accumulatedworldwide at the end of 1 9 9 7 was about 200 000 t HM of which about 130 000 t HM of spentf u e l is presently being stored in at-reactor ( A R ) or away-from-reactor ( A P R ) storage facilitiesawaiting either reprocessing or final disposal and 70 000 t HM has been reprocessed.Projections indicate that the cumu lative amount generated by 2 0 1 0 may surpass 340 0 0 0 1 H Man d by the year 2 0 1 5 395 000 t HM. Part of the spent f ue l will be reprocessed and somecountries took the option to dispose their spent f u e l in a repository. Most countries withnuclear programmes are us ing the deferral of a decision approach, a 'wait an d s e e ' strategywith interim storage, which provides th e ability to monitor th e storage continuously and toretrieve the spent f u e l later for either direct disposal or reprocessing. Some countries u sedifferent approaches for different types of fue l . Today th e worldwide reprocessing capacity isonly a fraction of the total spent fue l arising an d since no final repository has yet beenconstructed, there will be an increasing d eman d for interim storage.The present survey contains information on the basic storage technologies an d facil ity types,experience with wet and dry storage of s p e n t f u e l and internat ional experience in spent f u e ltransport. The main aim is to provide spent f u e l man agemen t policy making organizations,designers, scientists an d spent fuel storage facili ty operators with the latest information onspent f ue l storage technology un der wet and dry conditions.The IAEA wishes to thank th e working group w hich prepared this publication and all thosewho contributed to its preparation through their comments and participation in discussions.T he IAEA officer responsibl e for this publ ica t ion was P. Dyck of the Division of N u c l e a r Fuel Cyclean d Waste Technology.

7/29/2019 te_1100_prn

4/103

EDITORIAL NO T EIn preparing this publication for press, s t a f f of the IAEA have made up the pages from th eoriginal manuscript(s). The views expressed do not necessarily reflect those of the IAEA, th egovernments of th e nominat ing Member States or the nominating organizations.Throughout th e text n a m e s of Member States are retained as they were when the text wascompiled.The us e of particular designations of countries or territories does not imply an y judgement byth e publisher, th e IAEA, as to the legal status of such countries or territories, of their authorities andinstitutions or of th e delimitation of their boundaries.The ment ion of n a m e s of specific companies or products (whether or not indicated asregistered) does n ot imply any intention to infringe proprietary rights, n or should it be construed asan endorsement or recommendation on the part of th e IAEA.

7/29/2019 te_1100_prn

5/103

CONTENTS1 . INTRODUCTION...............................................................................................................1

1.1. Backgrovmd.................................................................................................................!1.2. Scope...........................................................................................................................!2. BASIC STORAGE TECHNOLOGIES A N D FACILITY TYPES.....................................2

2.1. Introduction.................................................................................................................22.2. W et storage.................................................................................................................22.3. Dry storage..................................................................................................................42.3.LVaults.................................................................................................................52.3.2. Container (cask and silo) systems.....................................................................6

3. EXPERIENCE WITH W ET STORAGE OF S PE NT FUEL..............................................83.1. Introduction.................................................................................................................83.2. At-reactor (AR) storage pools.....................................................................................83.2.1. Canada.............................................................................................................93.2.2. France.............................................................................................................113.2.3. Germany.........................................................................................................113.2.4. Japan.............................................................................................................. 113.2.5. Russian Federation.........................................................................................123.2.6. United Kingdom............................................................................................ 123.2.7. USA...............................................................................................................133.3. Away-from-reactor (AFR) storage pools.................................................................. 13

3.3.1. Bulgaria.......................................................................................................... 133.3.2. Finland...........................................................................................................143.3.3. France............................................................................................................. 153.3.4. Germany.........................................................................................................173.3.5. India...............................................................................................................173.3.6. Japan.............................................................................................................. 183.3.7. Russian Federation.........................................................................................193.3.8. Slovakia.........................................................................................................233.3.9. Sweden...........................................................................................................243.3. lO.United Kingdom ............................................................................................263.3.ILUkraine...........................................................................................................283.3.12.USA...............................................................................................................28

4. EXPERIENCE WITH DRY STORAGE OF SPENT FUEL ............................................294.1. Introduction...............................................................................................................294.2. V a u l t facilities...........................................................................................................30

4.2.1. Ca na da ............................................................................................................304.2.2. France.............................................................................................................324.2.3. Hungary...........................................................................................................344.2.4. United Kingdom ............................................................................................364.2.5. USA...............................................................................................................37

4.3. Cask facilities............................................................................................................394.3.1. Cask facilities in operation ............................................................................39

7/29/2019 te_1100_prn

6/103

4.3.2. Cask facilities under l icensing and construction............................................504.4. Silo facilities.............................................................................................................534.4.1. Silo facilit ies in operation..............................................................................534.4.2. Silo facilities under licensing and construction in the USA ..........................62

5. TR ANS POR TATION OF SPENT FUEL .........................................................................635.1. Introduction...............................................................................................................635.2. Interim storage location ............................................................................................635.3. Recent developments................................................................................................635.4. International experience in spent f u e l transport........................................................63

APPENDICES A-CAppendix A : Mul t i -e lemen t bottles ........................................................................................69Appendix B: Rod consolidation at BNFL...............................................................................71A ppendi x C: Container descriptions.......................................................................................72REFERENCES.........................................................................................................................95DEFINITIONS......................................................................................................................... ?CONTRIBUTORS TO DRAFTING AND REVIEW ............................................................ 101

7/29/2019 te_1100_prn

7/103

1. INTRODUCTION1.1. BackgroundThe IAEA conducted a survey between 1978an d 1980 to collect an d summarise informationon extended water pool storage in which there was increasing interest. M a n y uti l i t ies couldperceive a shortage of storage capacity an d only a limited amount of reprocessing capacity.The resul ts of this survey were published in 1982 in Ref. [1].hi 1986, th e IAEA considered it was timely to conduct a survey on the emerging f ield of drystorage and to update the data on wet storage. A considerable amount of R&D was being con-ducted in the field of dry storage. The results of the survey were pu blished in 1988 in Ref. [2 ]and gave a detailed assessment of dry storage technology and the associated R&D.hi the period since 1986very significant progress has been made in dry storage technologyan d a n umber of commercial facilities have been commissioned. There have also been an u m b e r of large pools constructed but these have largely been central facilities associated withreprocessing facilities or as interim storage for disposal.The purpose of this report is to collect and describe the worldwide experience that ha s beengained over th e last decade with th e storage of spent nuclear fue l . There is no intention to giveguidelines regarding the selection of technologies for storage of spent nuclear fue l , as dif ferentproven technologies are now available. The selection process has to take into account differentcriteria (e.g. quantity of fue l , cost of the technology, fue l management options, an d individualcircumstances) resul t ing in an optimum system in terms of technology, econom ics, t imetableetc.International experience with the storage of spent f u e l is described in Sections 3 and 4 for wetand dry storage, respectively. Section 5 covers th e subject of transportation of spent fue l as theSurvey is considered to be a convenient way of incorporating expe rience in transport.

1.2. ScopeT he scope of this report is to review th e current technology f or storage of spent f ue l frompower reactors. Storage of fuel from research reactors is not considered. The information anddata included has been derived directly from M e m b e r States where possible, from a review ofprevious d ocume n ta t ion an d from published documents from various sources ma de a va i la bleto the IAEA.Comprehensive information is not available on the storage of spent nuclear f u e l in at-reactor(AR) operational pools. Many of these are now designed for plant lifetime arisings at newN P P s and can be considered as a form of interim storage. T he spent f ue l pool inventory can beobtained by inference from total f ue l arisings and the quantity sent for reprocessing. Ro dconsolidation, as a means of increasing spent fuel storage capacity, is referred to briefly as thistechnique has not been taken up in spite of intense interest in the 1980s. Information on thistechnique can be f o u n d in An n ex G of Ref. [2].Away-from-reactor (APR)spent fuel storage is dealt with in some detail and a distinction ismade between storage on the re actor site (RS)and storage off site (OS).T he survey was conducted by a group of international consultants an d presented to a largeradvisory committee for review. Three consultants worked to finish th e draft report inDecember 1997.In 1998 some additional data and information were included.

7/29/2019 te_1100_prn

8/103

2. BAS IC S TOR AG E TE C HNOLOG IE S AND FACILITY TYPES2 . 1 . IntroductionVirtual ly all power reactors have some form of spent f ue l pools associated with th e reactoroperations. AR has, in recent years, been used to f u l l capacity in some cases, threatening th econtinued operation of the power plant . Recent designs of reactors have in fact nowincorporated pools that ca n accommodate l i fetime arisings over periods of up to 40 years.However, most older operational plants , due to their l imited AR capacity have necessitated th ed e v e lop me n t of APR storage.T wo technologies have been developed for APR storage. Initially th e storage method was wetbu t in recent decades dry storage techniques of varying types h av e been deve loped. A FRstorage can be considered in two categories. T he first is w here additional interim storagecapacity is constructed at the reactor site (RS) bu t largely or entirely independent of thereactor and its AR pool. This AFR (RS) storage can be wet in the form of secondary oradditional pools or most often in the form of dry storage facilities whic h may or may not havecapabili ty for off-site transport. It has been suggested that some of these A FR (RS) facil it iesmay stay operational well beyond th e l ife of the power p lan t (up to 50 or 100 years).The second category of AFR storage is off the reactor site (OS) at an in dep en den t location. Alarge proportion of this AFR (OS) capacity is in the form of pools at reprocessing plantsparticularly in France, the UK and T he Russian Federation. AFR (OS) interim storage ca n alsobe centrally located at a selected power plant complex an d receive f u e l from other powerplants. So far there are no AFR (OS) facilit ies at proposed repository sites. By far the majorityof AFR storage capacity is wet (approx. 9 2 % ) with only the remaining 8% in dry storage.Both wet and dry storage technologies hav e to address the fol lowing requirements:(1) Fuel c ladding integrity should be maintained during ha ndl ing an d exposure to corrosioneffects of the storage environment(2 ) Fuel degradation during storage should be prevented through providing adequatecooling in order not to exceed f u e l temperature l imits.(3) Subcri t icali ty of the spent f u e l is to be maintained u n d e r n or mal and accidenta lconditions.(4 ) Radiological shielding of the spent f u e l should protect p lan t operators, th e publ ic an dth e environment from receiving radiation doses in excess of regulatory limits.(5) Environmental protection should be assured by minim ising the release of radioisotopes.(6 ) F u e l retrievability must a lways be avai lable .2 . 2 . W et storageA s already discussed, w et storage is implemented in AR and AFR storage facilities.AR facilities are essentially storage pools in which spent f u e l is kept u n d e r water fol lowingdischarge from th e reactor. Most AR storage pools have been bu i l t at the same t ime as thereactor and are f u l ly integrated with th e reactor operation. Thus experience with AR wetstorage is available for more than 30 years and is not described in this section.There is a variety of AFR wet storage facilities in use. Some provide extended operationalcapacity to reactors once their AR pool is f u l l of spent fue l , and may or may not be bui l t atreactor site.

7/29/2019 te_1100_prn

9/103

A typical APR wet storage facility may have the following features: Cask reception, decontamination, unloading, maintenance and dispatch; Underwater spent f u e l storage (pool); Auxil iary services (radiation monitoring, water cooling and purification, solidradioactive waste handling, ventilation, power supply etc.).Spent f u e l is received (either wet or d r y ) at the ARF facili ty contained in a transport cask. Fuelm ay be removed either assembly by assembly or in a mul t i -e lemen t canister. Two types ofcask unloading method are in operation: wet and d r y . The wet unloading, being th e initiallydeveloped type for LWR spent fue l , is performed u n d e r water. A hot cell type facility is usedfor dry unloading.The storage pool is a reinforced concrete structure u s u a l l y buil t above ground or at least atground elevation, however, one wholly underground facility is in operation. Some early poolswere open to the atmosphere, but operational experience and the need to control pool waterpurity has resulted in all pools now being covered. The reinforced concrete structure of thepool, including th e covering building, needs to be seismically quali f ied dep en din g u p o nnational requirements.Most pools are stainless steel lined, some are coated with epoxy resin based paint. However,there has been experience with degradation of the latter after a n u m b e r of years. A furtheroption is for the pond to be u nlined and untreated. In some situations th e pool may be stainlesssteel lined or epoxy treated only at the water line or at other locations.Regarding unl ined and untreated pools, properly selected an d applied concrete proved to havenegligible corrosive ion leaching and permeability to water.T he pools are fi l led with deionized water with or without additive addit ion depending on thetype of f ue l to be stored and the adopted method of treatment. The water is either a fixedquantity or a once through pond purge. Water activity levels are maintained ALARA (as lowas reasonably achievable) by either in-pool or external ion exchange systems or by limitingactivity release to the bulk pool water.Leakage from th e pool is monitored, either by means of an integrated leakage collectionsystem or via the interspace in pools with two walls. In both cases an y recovered pool waterm ay be cleaned up an d returned to the main pool .In addition to the control of activity by ion exchange or purge, some pools are operated withan imposed chemical regime. This is for pH control, maintaining boron levels for criticalitycontrol where necessary, and the maintenance of acceptably low levels of aggressive anionssuch as chloride and sulphate to minimise f u e l degradation. Maintenance of good waterchemistry provides good water clarity and usual ly prevents th e occurrence of micro-biologicalorganisms. If these do occur, they are treated with specific chemical dosing.There are also tw o methods in regular u se allowing f u e l to be isolated from th e b ulk poolwater; namely by using single or mult i-element bottles, or storage containers.Subcriticaliry was originally maintained for LWR spent fue l (assumed to be fresh) by spacingwithin th e storage racks or baskets. However with th e need to store greater quantities of fuel ,higher storage density has been achieved by the introduction of neutron absorbing materials instorage racks and baskets such as boronated stainless steel, boral or boraflex.The period of t ime that spent f u e l resides in a pool varies between pools (AR and A P R ) an dth e requirements of the overall spent f u e l management system. Some Zircaloy clad f ue l hasbeen wet stored satisfactorily for over 40 years.

7/29/2019 te_1100_prn

10/103

The survey results of the AFR wet storage experience are given in Table I. The n u m b e r offacilities an d total design capacities are given along with th e approximate current inventoriesas of 1997.TABLE I. SUMMARY OF WORLDWIDE AWAY-FROM-REACTOR (AFR) W ET SPENTFUEL STORAGE

M e m b e r State

ArgentinaBelgiumBul gariaFinlandFranceGermanyIndiaJapanRussian FederationSlovakiaSwedenUkraineUnited KingdomUnited States of AmericaTOTAL

N u m b e r offacil i t ies11124113611141

28

AFR pools in operationDesign capacity

t H M1 1 0 01 0 0 0600

1 4 5 01 4 5 0 0

560274300

1 2 9 6 060 0

50002000

1 0 3 5 0780

5 5 2 2 7

C u r r e n t i nventorytHM

76635

356700

915952 627

350060465 23

270316957031700

33767

2.3. Dry storageDevelopment work and progress on a variety of dry storage technologies has been intensiveover th e last decade. Fo r practical and economic reasons, various dry spent f ue l storagetechnologies were developed to m e e t specific requirements of different reactor fue ls; e.g.max imum allowable cladding t empera t ure , cover gas environment (air, COz, or helium). Drystorage facilities operating or u n d e r construction in the M e m b e r States are listed in Table n, asof end of 1997.Initially dry storage were single purpose systems. They only provided AFR (RS) storage (withon e exception represented by Wy lfa Dry Stores, which is also an AR facility) without th ecapability or authorisation for eventu al t ransport off site (without rehandling and reloading thefue l into transport casks). Vaults, silos and non-transportable casks are single purposesystems. With con t in u in g d e v e l o p m e n t of dry storage technology, it was recognised that casksan d containers f or enc a psula t ing th e f u e l c o u l d perform multiple functions. Dual purposecasks were developed (e.g. CASTOR cask in Germany, TN 24 in Belgium and the NAC-STCin USA) which allowed storage an d transport to and from a storage facility without rehandlingof fuel assemblies. T he f u e l containers of some storage systems may be used for transportand/or final disposal. These are often referred to as dual- or multi-purpose systems,respectively.

7/29/2019 te_1100_prn

11/103

TABLE H. S UM M A R Y OF WORLDWIDE DRY SP ENT FUEL STORAGEMe m b e r StateArgent i naBelgiumCanada

OperatingConstruct ion

Czech R e p u b l i cFranceGermany

OperatingConstruction

H u n g a r yJapanRepubl ic of Korea

OperatingConstruction

Li th ua ni aUkraineUnited KingdomUS A

operatingconstruction

TOTAL

N u m b e r offaci l i t ies

]1

71I1

3111

11111

10639

Design capacityt H M200800

85671 4 5 0 0

60 0180

7768585162'73

60981 241950

958

47002155

43 138

Current inventoryt H M

64142

1930-

232180

58-

5473

60 9000

68 0

12705292

2.3.1. Vaul tsVaults consist of above- or below-ground reinforced concrete buildings containing arrays ofstorage cavities suitable for containment of one or more f u e l units. Shielding is provided byth e exterior structure. Heat removal is nor ma l l y accomplished by forced or natural convectionof air or gas over the exterior of the f u e l containing units or storage cavities, and subsequentlyexhausting this ai r directly to the outside atmosphere or dissipating the heat via a secondaryheat removal system.Typical features of vau l t s are their modularity, which facilitates incremental capacityextension, separated shielding and containment functions, capability for containmentmonitoring, and a vertical fuel loading methodology.

1 Phase 1.

7/29/2019 te_1100_prn

12/103

Spent fue l is received (either dry or wet) at a vault facility us i ng transfer or transportationcasks. S p e n t f ue l is removed from th e transfer or transportation casks, prepared for storage ifneeded, an d placed in a metal storage tube (single fue l element) or a storage cylinder (singleor multi-e lement canister) which is housed within a concrete storage cavity in the vaul tstructure. The storage t ube s o r storage cyl inders are sealed and may be backfi l led wit h an inertgas to i m prove hea t t ransfer f rom th e f u e l and prevent oxidat ion of spent f u e l w h i l e in storage.Th e y are u s u a l l y f i t ted with connections to a c o n t i n u o u s or periodic mo n i t o r in g system.I n va u l t s u s i n g metal storage t u b e s th e t ransfer of uncontainerised f u e l assemblies is carriedout, f o l l o w i n g drying if r e quir e d , one by one directly in to their storage locat ion . T ypi c a lc omponent s of this type of storage facility are the v a u l t mod ule s , th e fue l h a n d l i n g ma c hineoperating in the charge hall, the cask receiving area and the auxil iary facilities (areas for pla ntcontro l , maintenance, services, offices etc. ) . Examples are the M V D S fac i l i ty at Paks inH u n g a r y and the M a g n o x Dry Storage Facili ty at the W y l f a reactor in the UK.Vaul ts u s i n g storage cylinders receive th e f u e l already sealed in containers (the M A C S T O Rsystem CA NST OR a ppl i c a t i on at Genti l ly 2 NPP in Can ad a, th e C A S C A D fac i l i ty in France,or Fort S t. Vrain M V D S in the USA). T hes e types of v a u l t facili ties use a t r an s fe r caskhandled by crane. T he container transfer into th e storage cylinder is either performed remotely(CASCAD) or with operator assistance (Fort S t. Vrain an d Genti l ly 2).2.3.2. Container (cask and si lo) systemsA c onta i ner is a receptacle to hold spent f u e l to facil itate m o v e m e n t and storage or e v e n t u a ldisposal, according to the IAEA glossary of spent f u e l terms [3]. M et a l casks, c onc re te casksan d silos are variations of the container storage systems. T here is a large variety of c o n t a i n e rsystem designs used for storage of spent f ue l .T he fol lowing features are common to all cask and silo designs:Casks or silos ar e m o d u l a r in nature. These systems ar e sealed systems wit h no radioactiverelease f rom th e casks or silos d ur i n g storage. A storage cask or silo provides s h i e l d i n g an dco n t a in me n t of the spent f u e l by physical barriers which m ay inc l u de th e m eta l or concreteb ody an d metal l iner or me t a l canister and lids. T h e y ar e usua l l y circu lar in cross-section, witht he l ong axis being ei ther ver t ical or hor izontal . Fuel posi t ion is maintained inside a storagebasket which may or may not be an integral part of the container. Heat is removed from th estored f ue l by conduction or natural convection to the s urroundi ng e n v i r on me n t . Casks orsilos may be enclosed in b u i l d i n g s or stored in an open area.A cask or silo storage facil ity m ay include cask h an d l in g eq ui pm ent , fue l h a n d l i n g equipment,decontamination e quip me n t , radiation protection, and leak tightness mon i tor in g e q u i p m e n t .Cask or silo storage facili ties may not be independent of reactor services and may dep en d oncask handling, f ue l handling and decontamination e quip me n t from th e reactor.Some features that m ay vary between the technologies are structural material , transportability(dual or m ul t i - purpos e) , f u e l loading orientation, s torage orientat ion (horizontal or vertical).I ndiv idu a l systems may or may not be monitored f or leak tightness.2.3.2.1. Metal casksMeta l casks are m a s s i ve c on ta iners used in transport, storage and eventual disposal of s pentf ue l . T he structural materials for metal casks may be forged steel, n odu lar cast iron, or asteel/lead sandwich structure. They are fitted with an internal basket or sealed metal canisterwhic h provi des st ructural s trength as wel l as assures sub crit ical i ty . Metal casks u s u a l l y h a v e a

7/29/2019 te_1100_prn

13/103

doub le lid closure system that may be bolted or seal welded and may be mon i tor e d for leakt ightness.Metal casks ar e u su al ly t ransferred direct ly from th e f u e l loading area to the storage site. S omemetal casks ar e licensed for both storage and off-site transportation. Fuel is loaded vertical lyinto th e casks which are u s u a l l y stored in a vertical position.Metal casks used in a n u m b e r of countr ies such as Germany, th e USA, th e Czech R e p u b l i c an dS w it z e r l an d ; Transnucleaire 's TN-40 metal casks used in the USA;West inghouse MC-10caskus ed in the USA;a nd Nuc lea r Assurance Corporation's metal cask designs used in the USAan d S p ain .2.3.2.2. Concrete casksConcrete casks ar e mov e able st ructures with one storage cavity. Th e y ar e u s e d in storage, an din some cases, t ransport of spent f u e l . Structural s t rength an d radiological s hi e ld i ng areprovided by reinforced regular or high density concrete .Concrete cask systems may use sealed metal canisters housed inside th e concrete storage caskto contain spent f ue l . T he metal canister may be cooled by natural convect ion of the ambientair and use a double lid closure system.Sealed metal canisters may be contained in an on-site transfer cask for loa ding spent f u e l fromth e f ue l loading station and for transfer to the concrete storage cask.S p e n t f u e l may also be loaded directly into a concrete cask in the fue l load in g station and theconcrete cask w o u l d be transferred directly to the storage site. Some sealed metal canis tersmay be l icensed for transportation as part of an off-site transportation package.Alternat ively, concrete cask systems m ay use a m etal l iner in the cask cavity to contain spentfue l and a single l id closure system. H eat transfer m ay take place sole ly by conduction throughth e concrete s tructure.Concrete casks that re ly on conduct ive heat transfer have more thermal l imitat ions th an thoseu s ing n at ur a l convection air passages.F uel is loaded vertically into the concrete casks and the concrete cask systems are stored in avertical orientat ion.Concrete casks u se single or d o ubl e l id closure systems, are welded c lose d , an d tested for leaktightness. Concrete cask systems may or may not be monitored for leak t ightness.E x amp le s of vertical concrete casks inc lude Sierra Nuclear 's V S C cask; and Ontario Hydro'sPickering concrete dry storage container which is also designed for off site transport.2.3.2.3. SilosSilo systems are mon ol i th ic or m o d u l a r concrete reinforced s tructures . T he concrete p r ov id e sshie lding w h i l e c onta i nm ent is provided by either an integral i n n e r metal vessel ( l i ner ) , w h ichcan be sealed after fuel loading, or by a separate sealed metal canister. In si los, s pent f u e l m aybe stored in vertical or horizontal orientation. Fuel loading in to silos always takes pla c e at thestorage site.A typical exa m ple of a silo system is AECL's concrete canister, whic h is b u i l t on-si te u s i n gregular reinforced concrete and is f i tted with a steel inner l iner. Spent f u e l is transferred inincrements within sealed baskets us in g a shielded transfer cask and loaded vert ical ly. Once

7/29/2019 te_1100_prn

14/103

loading operations are complete, a closure shield p l u g is placed an d welded to the inner linerto provide additional containm ent.The NUH OMS storage system is an example of a horizontal concrete silo system. Fuel isloaded vertically into metal canisters which are stored in a horizontal orientation insideconcrete storage modules. The sealed metal canister is contained in an on-site transfer cask forloading spent f u e l from th e fue l loading station and for transfer to the horizontal concretestorage module . The metal canisters are fitted with a double l id closure system, whichfollowing welding is tested for leak tightness. Some sealed metal canisters may be l icensed fortransportation as part of a transportation package. The system is not monitored for leaktightness.3. EXPERIENCE WITH WET STORAGE OF S P E N T FUEL3.1 . IntroductionThis section ou tlines and docum ents the experience on wet storage.Storage pool experience exists for both A R a nd A PR technologies. Wh ile A R p ool storage iscommon to all reactors in order to provide cooling fol lowing discharge from th e reactor, AP Rpool storage is an option for additional spent f u e l storage prior to disposal or reprocessing.The information on AR pools is not complete bu t some representative examples from someMember States have been included. The quantity of fue l storage in AR pools is difficult todetermine because the inventory varies with reactor refue l l ing cycles and the amounttransferred to AFR storage an d reprocessing. In general, AR pools are never operated to f u l ldesign capacity because of a need to provide some b u f f e r storage capacity for operationalreasons. Since th e last survey completed in 1988, a pproxi m a te ly 4 0 pow er reactors withrelated AR storage pools have been commissioned. The variety of solutions for AFR poolstorage gives a wide range of experience. AFR pool facili ties are subdivided into pools inoperation, under licensing and construction.Positive experience on the storage of spent f u e l in pools has been collected over more than 30years. It can now b e predicted that Zircaloy clad fue l integrity w ill be maintained even after 50years of wet storage. Monitoring an d survei l lance have confirmed that adherence to thespecified pool water chemistry is essential to prevent f u e l cladding degradation during p oolstorage for all types of spent fue l . Even if the fue l assembly contains defects incurred duringirradiation, it can be stored in pools for extended periods. It may even be that a poolcomponent could, in some cases, be more l i fe limiting than the f ue l assembly itself.In conclusion it can b e stated, that wet storage of spent fue l is a proven technology, which ca nme e t all storage requirements through proper engineering. The experience, which has beenreported using different facilities, is described in this section.3.2. At-reactor (AR) storage poolsAt-reactor spent f ue l storage pools are either within th e reactor building or in an adjacentspent fue l bui ld ing which is linked to the reactor by a transfer t un n el . Access to the f u e l in thestorage pool is usua l ly by means of immersing a cask in the pool, loading it with fue l and thenremoving th e cask for l id closure, decontamination an d transport. A recent development,un ique to France, is a cask loading concept with bottom access ports from the pool for fue ltransfer into th e cask. The advantages of this design are that contamination of the externalsurface of the flask by immersion in the pool is avoided, an d also th e requirement to l if t th e

7/29/2019 te_1100_prn

15/103

f lask (empty and loaded) between th e inlet/outlet location and the p ool and a heavy duty craneis no longer needed. There are some cases, for example at gas cooled reactors and at Sel l a f ie l din the UK, w here spent f u e l is loaded into casks in a dry shielded cave and the cask is neverimmersed in water.The capacity of AR wet storage pools varies between countries and is a fun ct io n of the overallf u e l ma na gement strategy at the t ime th e faci li ty w as b u i l t . T h e e x tr e me s are modest s toragecapacity for short term b u f f e r storage before transport off-si te, to capacity s u f f i c i e n t to store asignificant proport ion of the reactor l ifetime arisings. T he lat ter is genera l ly th e r es u l t of thedeferral by a c ou nt r y on decisions for reprocessing or disposal. In a ddi t ion there wil l be ar eq u i r ement to reserve space f or f u l l or part core inventory. This capacity for wh ole cor edischarge would be separately identified as part of p l an t operations and is not considered partof AR interim spent f ue l storage. In addition, new fue l or partly uti l ised f u e l c ould betemporar i ly stored in the pool as part of plant operat ing inventory an d w o u l d r e d uce the netcapacity avai lable for AR storage.All A R storage p ools require some form of water pu r i t y an d chemical control to m i n i m i s e th eef fects of corrosion a nd t he b u i l d u p o f activity in the water . Th is is pot ent ia l l y impor t a nt f orlong periods of storage and w o u l d be augmented by data from research and inspect ion. T hemajority of f u e l in wet storage is from water cooled reactors and is clad in zirconium basedalloy. The experience has been good and potential mechanisms for corrosion or degradationar e understood. With water reactor fue l , removal from th e transport f lask or other containercan some t ime s r es u l t in release of active particulate material (crud) i n to th e pool water . T hi sdepends largely on the f u e l history in the reactor.AR w et storage summarised in Table III.3.2.1. CanadaExperience with w et storage of s pent f u e l goes back to the early 1950s. Canadian in-pool w etstorage t ec hnology w a s ini t ia l ly developed at Chalk River Laboratories. T he same technologyis applied to store f u e l f rom C A N D U prototype an d p o w e r reactors.In Ca na da neither recycling n or reprocessing are pla nned for spent C A N D U f u e l . A p e r m a n e n tdisposal system is current ly b eing deve loped. C ons eq u ent l y , A R interim w et storage facil it iesare expected to remain operational un t i l fue l shipment to the disposal centre is complete(around 2035).C ANDU reactors have a variety of pool designs and storage capacity. Single u n i t stations areu s u a l l y provi ded with a single pool. T he storage capacity is based on 10 years of reactoroperation.Ontario Hydro's mu l t i - u ni t s t a t ions u s u a l l y have pr imary an d secondary storage pools. T hewater fi l led, reinforced concrete pools are b u i l t in and out of g r o u n d and are f i t ted with epoxyor stainless steel liners.Spent f u e l b u n d l e s are horizontal ly stored in the pool in receptacles of di f f er ent designs.Storage trays accommodate up to 24 b u ndl es in a single layer. Trays ar e stackedapproximately 19 high in groups of two to four. Each group of stacks is provided with a coverthat is held in place by vertical rods that retain the stacks together to resist seismic loads an dfor safeguards reasons.At Ontario Hydro's Picker ing an d Darlington reactor sites, spent f u e l is stored in rec ta ngula rmod ule s containing 96 f u e l bun d le s . Th e modules ar e equipped with wire mesh along th esides and are stored in frames for seismic restraint an d safeguards purposes.

7/29/2019 te_1100_prn

16/103

TABLE HI. INTERNATIONAL AR W ET STORAGE EXPERIENCEC o u n t r y

ArgentinaBulgariaCanadaC h i n aC ze ch Rep.FinlandFranceGermany

HungaryItalyJapan

Korea, Rep.LithuaniaMexicoRoma ni aRussianFederation

SlovakiaSl oveniaSouth AfricaSpainSwedenSwitzerlandUkraine

UK

US A

Type of reactorsP H W RWWER-440WWER-1000CANDUP W RW W E RB W R / W W E R9 0 0 M W P W R1300 MW P W ROperat ing P W ROperating BW RS h u t downW W E RLW RP W RBW ROthersPWR/PHWRR B M KBW RC A N D UWWER-440WWER-1000R B M KW W E RP W RP W RP W R / B W RPWR/BWRPWR/BWRWWER-440W W E R - 1 0 0 0R B MKMagnoxAGRPW ROperat ing LW RShutdown LW R

N u m b e r ofpools24210344

3420136843

2023212221671141291252113

20141

1 108

Capaci ty,tHM145048052031 40 748066 6

5870542031761385526480253

64608410280

587520939849404801200356048041 067 0382015007052 40

21 7060 0150023093 6

5 9 0 0 01700

Inventory,t H M120012 12662 2 5 5 517 73062 51

41871608201182 1

-350253

20703050

12 03 0 7 21380

8010 0320460

2 7 0 015 020539220007 3015 092

115638033015 430

383439 5 7

Operatingperiods1 975 -1 974 -1988-1971 -1 9 9 1 -19 85-1 978 -1 979-1 9 8 5 -1 9 7 5 -1 9 7 7 -1968-1 9 8 2 -1981 -1 9 7 0 -1 9 7 0 -1966-1 9 7 8 -1 9 8 4 -1991 -1 9 9 6 -1 9 6 6 -1978-1 9 7 5 -1 9 8 1 -1 98 4 -1 98 4 -1969-1 973-1 9 7 0 -1980-1982-1 9 7 7 -1 9 5 6 -1 9 7 6 -1 9 9 5 -1 9 5 7 -1 9 5 7 -

10

7/29/2019 te_1100_prn

17/103

Fuel handling is currently a manual operation in most instances. Fuel loading into th e storagemodules is performed remotely underwater. Special tools are used to manipulate bundles andtrays from a travelling bridge over th e pool .Three CANDU prototype reactors are decommissioned including th e pool facilities. AtDouglas Point, the stainless steel lined pool has been completely decontaminated. Allauxiliary systems are kept operational. At Gentil ly-1, the epoxy lined pool is completely cleanfollowing drainage an d removal of contaminated concrete surfaces. The entire area isconverted into office space. The NPD reactor pool (stainless steel l ined) is drained, partiallydecontaminated and kept u n d e r surveillance.3.2.2. FranceThe back end of f u e l cycle policy implemented in France (based on reprocessing, plu t oniuman d uranium recycl ing through MOX and RepU fue ls) , has resulted in the French utility EDFestablishing a management practice to reprocess the U02 fue ls first (after a suitable coolingperiod) while storing the MOX and RepU spent fue l s for a period of t ime not defined yet.AR storage capacities are needed at each reactor site in order to secure a cooling period fordischarged f ue l awaiting transportation to the reprocessing plant.3.2.3. GermanyThe German spent fue l management policy was primarily based on reprocessing unti l 1994.Reprocessing was mandatory by German atomic law. Exceptions were permitted ifreprocessing was not available or not economically feasible e.g. in the case of the HTR pebblebed spent f ue l .A law was passed in 1994 by parl iament which allowed direct disposal as an equivalentoption. The choice is left to the utilities operating th e NPPs.A H NPPs are equipped with AR storage pools. The technical design is in accordance withproven international standards. The capacity an d geometry vary from plant to plant. Morerecent plants tend to have larger storage capacity in order to improve the f lexibi l i ty of spentfue l man age me n t .3.2.4. JapanMost of the spent f u e l in Japan is stored in AR pools an d amounts to 5200 t H M . This is onlyabout 1/3 of the total AR design capacity. Some of the fue l , amounting to over68001 HM in cludin g PWR,BWR and Magnox, has been sent for reprocessing in the UK andFrance. 1000 t HM has been sent to the Tokai facility. A small amount has been put into anew cask storage at Fukushima and amounts to 73 t HM. Some AR facilities currently havevery small qu antities of f u e l in storage or n on e.Experience with wet storage of spent fue l has been good an d extends over about 31 years(1966-1997). N o defected f ue l has been reported nor any serious incidents with storagefacilities.Breeder reactor f u e l has also been stored since 1996 and no problems have been reported.Currently 88 t HM of fast reactor f u e l is in AR storage.

1 1

7/29/2019 te_1100_prn

18/103

3.2.5. R us s i an FederationFollowing is a brief description of standard AR facility constructions an d operation.T he WWER-440 AR storage period is normally up to 3 years. T he storage pool is situated inthe main hall of the reactor unit in the vicinity of the reactor.T he storage capacity of standard AR pools at WWER-440 reactors is designed for 2 fu l l cores.On e half (about 350 assemblies) was originally designed for normal reloads and the u p p e rracks are us e d for emergency discharge from th e reactor. Fuel is stored in racks at a spacing of225 mm in a triangular arrangement. (Some WWER-440 pools in other countries wentthrough a reracking which resulted in doubling th e capacity).The construction of the AR storage pool for WWER-1000 fue l is somewhat dif ferent than forWWER-440 reactors. T he storage pool with a total v o l u m e o f 1100m 3 consists of 3 bays. Thefirst bay and one half of the second bay are occupied by the rack for spent fuel , while th e otherhalf of the second bay is used for storing new (unirradiated) f ue l . The third bay is a reserve foremergency core discharge. The total capacity of the pool is designed on the requirement toaccommodate 2.5 f u l l cores (three yearly discharges in a 2 year f u e l cycle plus on e emergencycore discharge totalling 165 t HM). Fuel is stored in racks with a spacing of 400 mm in atriangular arrangement.T h e A R storage pool f or RBM K - 1 00 0 f u e l is situated in the m ain reactor hall in the vicinity ofth e reactor. The p ool consists of 2 independent bays, each hav ing the volume of 750 m 3. Thedesign capacity of each bay is for 850 fuel assemblies stored in separate cans filed withdemineralised water. Reloading operations are performed by a special reloading mach in e atth e operating reactor. Spent f u e l placement in a storage position is by means of a It hoistwhich has a restricted lifting height to ensure that th e f ue l remains u n d e r a shielding waterlayer at all times. The loaded cans are hung between beams spaced at 250 mm at the level ofth e metal deck of the pool hall. Fuel assemblies are spaced at 160 mm.The BN-600 f ue l is also stored in water pools. Reloading operations are performed at the shut- down reactor during planned maintenance and repair works. A dry reloading mode is us e d ,with the reloading equipment located in the reactor vessel and in reloading boxes orcontainers. Inert gas atmosphere in the containers provides safe reloading of f u e l with tracesof sodium coolant.

3.2.6. United KingdomIn the UK no problems have been experienced with interim storage of AGR stainless steelclad f u e l in station spent fuel storage pools. Fuel is stored in open topped skips and as it iscurrently al l committed to reprocessing, th e storage period is not long usual ly less than a yearbu t cooled for about 120 days before transport. The pools have reserve capacity for a wholecore discharge. T he pools have th e u s u a l capability for recirculation, cooling and filtration.Magn ox f u e l storage in AR pools is also satisfactory with th e f ue l elements stored in opentopped skips. M a gnox c la ddi ng c a nnot dw el l in water f or long periods and the f u e l is u s u a l l yshipped for reprocessing after a cooling period of a b o u t 120 days.A s with it s American counter parts of more recent design, Sizewell B has been designed tominimise th e stations dependency on the back end of the nuclear fue l cycle. Initially designedto accommodate up to a thousand f ue l assemblies approximately 18 years of operation,capacity is currently being reviewed by investigation of fuel densification systems. Sizewell Bwas commissioned in 1995 and has discharged its first f u e l to the AR pool.

12

7/29/2019 te_1100_prn

19/103

3.2.7. US AThe majority of spent nuclear f u e l arisings in the USA are stored in at-reactor spent fue lstorage po ols. At the end of 1 9 9 7 , 110 operating and 9 shutdown reactors had approximately35 500 MTU of spent nuclear f u e l in storage in operating reactor AR pools an d 1 0 0 0 MTU inshutdown reactor pools. Approximately 1 3 0 0 MTU of spent f u e l is stored in dry storagefacilities.The current licensed AR wet storage capacity in the USA is approximately210 0 00 spent f u e l assemblies, corresponding to approximate ly 61 000 M T U . However, th eexcess of tota l maximu m capacity over current total inv entory does not reflect th e shortage ofpool storage capacity that occurs in individual reactor cases. For example, shutdown reactorpools had a capacity of 5800 assemblies or approximately 1 7 0 0 M T U . T he majority of reactorspent fue l storage pools have been reracked once, and some several times, to increase in-poolstorage capacity. Reracking of spent f ue l storage pools is now only available to a smallremaining n u m b e r of US reactors as a mea ns of increasing storage capacity [ 4 ] .Currently, 14 reactors have exhausted A R pool capacity and have had to construct dry storagefacilities. Of the 110 operating reactors in the U S A , approximately 27 reactors are projected torun out of in-pool spent fue l storage capacity by 1 9 9 8 .3 . 3 . Away-from-reactor ( A P R ) storage poolsAway-from-reactor pools constitute the largest volume of interim spent f u e l storage. They aredivided into pools at the reactor site ( R S ) an d pools away from th e reactor site or off site ( O S ) .The distinction between the RS and OS categories is clear but this is not always as clear inclassifying At-reactor an d Away-from-reactor storage pools. True AFR(RS) pools ar eindependent of the reactor and all its services and can continue to operate after th e reactor hasbeen f inally shut down and decommissioned. There are pools, however, that are truly APRtypes but rely extensively on reactor services such as cooling water and water treatment,ventilation an d electrical supplies ( e . g . Loviisa, Pickering). In fact, nearly al l AFR(RS) poolsare dependent on the reactor systems to some extent and certainly for staff and operatingm a na gem ent . When reactors are shut down, special arrangements wil l ha ve to be takenbecause it could be impractical or uneconomic to continue to operate costly reactor derivedservices if the f ue l must remain in storage for long periods. Man y of the AFR(RS) facilit ieshave been provided at older power plants because these AR pools are often not large nor sizedfor lifetime arisings.AFR(OS) interim storage facilities on the other hand are most often associated withreprocessing plants (La Hague, Sellafield, Cheljabinsk an d Rokkasho M u r a in the future) bu tsometimes for direct disposal ( e . g . CLAB in Sweden).3.3.1. BulgariaBulgaria has one AFR(RS) facility located at Kozloduy N P P .Proposed in 1 9 7 4 as an alternative to spent f u e l transportation to the USSR, construction ofKozloduy AFR(RS) facility did not began un t i l 1 9 8 2 . The first f ue l receipts to this facilityw ere mad e on the 28 th February 1 9 9 0 .T he facility was the first of a proposed common design for an APR at the Soviet b u i l t reactorsto store WWER fuel and it comprises of f u e l receipt, u nloading an d storage areas. The currentdesign is slightly different from th e other facilities in that respect that this was m e a n t for the

13

7/29/2019 te_1100_prn

20/103

long-term storage of 168 baskets (4920 assemblies, -600 t H M) of spent f u e l from the sitesfour WWER-440 and two WWER-1000 reactors; to be loaded over a period of ten y ears.After cooling for 3 years in the AR storage pools, th e assemblies ar e transported to theAFR(RS) by an on-site transport container and a specialised trailer unit. Yearly receipts are atth e rate of 25 transport baskets comprised of 4 baskets or 120 f u e l assemblies per WWER-440reactor and 9 baskets or 108 f ue l assemblies from the two WWER-1000 units.T he storage area is mad e u p o f three operational water bays and a contingency bay to allow forprevent ive maintenance/provision against major in-bay fa i lure. T o afford this storage bays canbe isolated from the one another by hydraulic seals/gates, an d leak monitoring e quip me n t isprovided at the pool l ining inter space. All pools are d o u b l e d l ined with carbon an d stainlesssteel.Spent f u e l from th e WWER-440 reactors is stored in transport baskets (containing 30 f u e lassemblies (FA) with intact fue l cladding or 18 bottled f ue l assemblies where the cladding isleaking). WWER-1000 spent fue l is stored in transport baskets. T he capacity of the b askets is:12 intact f ue l assemblies, or 6 bottles of failed f ue l .Storage temperature is maintained below 45C in the spent f u e l compartments which areprovided with automatic cont inuous monitoring of feedwater, overflow, and permissible highand low water levels.3.3.2. FinlandFinland has two AFR(RS) facilities located at Loviisa an d Olkiluoto NPPs.3.3.2.1. Loviisa AFR(RS)Phase 1 of the Loviisa AFR(RS) was b rought into operation in 1980 increasing th e storagecapacity of the un i t 1 NPP t o take account of a need for increased f u e l cooling from 3-5 yearsprior to transport/reprocessing in the Soviet Union. The APR was later extended to 1984(phase 2) to provide additional storage cap acity f or u n i t 2 of th e NPP (see Fig. 1).T he tw o phases of the AFR were b u i l t alongside on e another three metres below ground. Theservices f or each phase are provided by the associated u nit of the NPP.Phase 1 comprises tw o paral le l storage bays, a loa ding bay,a decontaminat ion we l l for casks,a dry burial ground for control rods, and a lid deck u n d e r which the cask transport vehicles arelocated. The storage bays are connected to the loading bay by gates and each bay has acapacity for up to eight f ue l baskets. A f ue l basket ca n accommodate 30 f u e l assemblies with ahexagonal spacing of 2 25 m m. Thu s the total storage capacity is 480 assemblies (57.6M g U ).Phase 2 comprises three storage bays in a row,a loading bay,a decontamination well for thecask and lid deck under which th e cask transporter vehicle is located. T he storage regime inphase 2 differs from pha s e 1 in that each bay a c c ommoda t es f o u r f u e l racks of 130 assemblycapacity (total 187.2M g U ).The storage bays in both phases are connected with gates an d covered by lids wh e n there areno fuel handling operations.3.3.2.2. T VO - KPA AFR(RS) (Olkiluoto)A cross-section and detailed description of the KPA Store at Olkiluoto Power Plant is givenon page 107 of Ref. [2] and will not be repeated here.

1 4

7/29/2019 te_1100_prn

21/103

3.3.2.2.1. Operational experienceLong stored fue l undergoes a programme of condition survei l lance, this includes visualinspections and oxide layer thickness measurements. Over th e past f ive to ten years ofmonitoring n o abnormal events have been observed.The time required to transfer an d place fue l into storage is 4-5 days. Collective dose for eachfue l loading is not separately registered, bu t estimated to be about 0.06 mSv. T he collectivedose during storage maintenance and operation is about 1 mSv/a. Dose rate at site boundary isnot directly measurable but is less than th e background level of the site:0.15 uSv/h. Abnorma loccurrences have not been reported.3.3.3. FranceFrance has 6 AFR(OS) facilities operated by C O G E M A at La H a g u e in support ofreprocessing activities (See Table IV).

TABLE IV . FRENCH APR STORAGE FACILITIES AT LA HAGUEStorage pools

UP2 800pools

UPS

Total

Storage HA ON P HP o o I CP o o I DP o o l E

Nominal capacityt H M

4002 0 0 03 6 0 03 5 0 04 9 0 01 4 4 0 0

InventorytHM

1841 13 324172 1963 2 5 69 1 5 9

Commissioningdate19761981198419861988-

3.3.3.1. TOThe TO dry unloading facility commissioned in 1986 has a design throughput of 800 t HM/aprocesses individual dry casks. The internal arrangement of the facility is based on a cross, th epoints of the cross making u p process areas, i.e. cask receipt/export, preparation, unloadingand decontamination. Each cell is isolated form one another by shield doors.On receipt th e cask is placed on a trolley which is remotely m o v e d around th e facility, caskpreparation includes the f i tting of the special col lar for making a seal with th e unloading hotcell. Fuel unloading involves engaging th e cask into th e base of the hot cell by hydraulicallyraising th e cask. Once a seal is attained, the hot cell shield plug is removed, the cask lid isremoved and individual f ue l transfers ca n take place. Prior to loading th e f u e l into th e storagefue l basket, located on a ramp at one end of the hot cell, th e f ue l is checked for integrity usinga krypton monitor an d then cooled to pool water temperature in a water circulating pit.Spent fuel receipt an d storage at La Hagu e is achieved by a collection of independent facilitiesserved by a common fue l shipping cask storage pad. Fuel storage facilities are interconnectedto achieve optimum availability of nuclear materials for reprocessing.

1 5

7/29/2019 te_1100_prn

22/103

O 125 TONCASKCRANEO 15 TONCRANEG UNLOADINGPOOLO DECONTAMINA-TION POOLSTORAGE POOLTRANSPORT CASK

OTRANSPORTCANISTERO FUELHANDLINGMACHINEOGATE

FUEL STORAGERACKQ COOLING CIRCUITHEAT EXCHANGERO EXHAUST AIR

FILTER

FIG 1. Lov i isa pool.

3.3.3.2. H AO (High Activity Oxide) NordCommissioned in 1976 the HAO facility has a cask unloa ding throughput of 400 t HM/a isconnected to a pool with a storage capacity of 4001 HM. It is designed as a fue l storage b u f f erto the UP2 400 plant unti l i ts reprocessing capacity is doubled by commissioning new unitswhich will make i t the UP2 800 p lant . The HA O Nor d facility will then cease to operate.3.3.3.3. NP H (New pools Hague)NPH facility commissioned in 1981 comprises of a single cask wet unloa ding l ine with adesign throughput of 800 t HM/a. T he line which is capable of handling all types of shippingcasks (standard, non-standard, dry or wet) is connected to a pool with a storage capacity of2000 t HM an d is current ly used to s upply spent f u e l to the UP2 800 reprocessing plant.3.3.3.4. Storage facilitiesIn addition to the faci l i t ies mentioned above, th e un d e r wate r storage capacity at La H a g u eplant is ensured by a set of three other facilities. Pool C was commissioned in 1984, its storagecapacity is 3600 t H M . Pool D was commissioned in 1986 along with the TO facility, itsstorage capacity is 3500 t HM and is used to supply the UP3 plant. Pool E facility wascommissioned in 1988, its storage capacity is 49001 HM.Spent fuel is stored in 9 compartment PWR and 16 compartment BW R baskets equipped withlocked lids to prevent accidental modification of the f u e l arrangement. Where spent f u e l of

16

7/29/2019 te_1100_prn

23/103

greater than 3.75% U235 initial enrichment is received th e f u e l b u m u p is meas ured us in g asystem "PYTHON" to allow storage at the same capacity.Pool temperature is maintained below 40C an d water activity below a bout. T "35 x 1 0 Ci/m(18.5M B q / m ) during normal operat ion.One feature which differs from most A P R pools are the d e p loy me n t of in-pond heatexchanger/ion exchange units ( N Y M P H E A ) in pools C, D and E. This design has theadvantage of prec luding th e siting of radioactive portions of the cooling network outside thepool. Movement of f u e l between pools is performed by conveyors between pools C, D, and E,an d a dry transfer corridor betwee n pool C and NPH.

3.3.4. GermanyGermany has l imited APR wet storage facili ties located at Greifswald NPP.The Greifswald power plant now shut down consisted of five Russian WW ER-440 u n i ts eachwith associated AR pools and a central AP R pool of standard design for W W E R plants. It issimilar in design and capacity to the APR pool at Kozloduy (see section on Bulgarian AP Rpools).All pools are currently being cleared of f u e l to allow decommissioning activities tocommence. Some of the f ue l of low b u r n u p was sent to the Paks power plant in Hun gary ( forre-irradiation), but the remainder is p lan n ed even tua l ly to go into dry cask storage.

3.3.5. IndiaIndia has a single AFR(RS) facility located at Tarapur.3.3.5.1. TarapurThe 2 8 0 1 H M (2000 assemblies) Tarapur AFR(RS) facility, which w as commissioned in 1991with a 25 year design l i fe , w as provided to service the two Ta ra pur B W R reactors whilst theback-end policy was derived. The facility now also accommodates f ue l from th e RajasthanP H W R N PP (Kota) as an interim measure wh i ls t addi t ional storage faci l i t ies ar e beingprovided at that plant.T he seismically designed facility measures 7 3 m x 35.5 m x 22.3m high an d comprises ofspent fuel , services an d waste man agemen t bu i ldin gs . A more detailed description of thefacility is provided in Ref. [5].Receipts into the facility are made in a storage cask, originally intended for dry storage atother locations, with a capacity f or 37 fue l assemblies (5.2t H M) a nd is normal ly loaded with10 year cooled f u e l .The pool is stainless steel lined, measures 9 m x 1 3 m x 1 3 m deep, is buil t partly belowground and has 1.5 m thick walls . Fue l is loaded into high density f u e l racks of 12 x 12 arrayby using a 1 t bridge crane. Fuel racks are designed to me e t both criticality and seismicrequirements.

17

7/29/2019 te_1100_prn

24/103

Because th e e qui l ibrium te mp e r atur e of the long cooled f u e l has been calculated not to exceed60C (when th e facility is fu l l y loaded) no emergency cooling system is provided. However, aheat exchanger has been provided to keep water temperature below 42C u n d e r normaloperating conditions.3.3.5.1.1. Operational experienceT he faci l i ty has operated satisfactorily since it was commissioned in 1991. Visibili ty, pondwater activity an d temperatures are all well within limits. Radiation levels over the ponds isalso wel l within l imits.

3.3.6. JapanJapan has three A PR w et storage facilities, tw o AFR(OS) facilit ies at the reprocessing sites ofTokai Mura an d Rokka sho M ura , a nd a new AFR(RS) located at the Fu ku shima Daiichi NPP.3.3.6.1. Tokai MuraThis rela t ively small 100 t HM capacity AFR(OS) facility acts as a b u f f er for the Tokai M u r aprototype 0.7 t H M / d a y capacity reprocessing plant. The facility comprises of casksreceipt/preparation areas, unloading pool, s torage pool and intermediate pool f or f u e l feedingto th e head end of the reprocessing plant. Fuel is stored in baskets.3.3.6.2. Rokkasho MuraThe facility consists of 3 bays each having 3 compartments. T he compartments at one endc ommunic a t e with th e other bays by means of a transfer channel and an un der wa ter transfertrolley f or baskets. There is a spent f u e l handling machine provided for each bay. A n o ut l in eof th e facility is shown in Figure 2.T he total capacity of the Rokkasho M u r a pool is 3 0001 H M distributed as fo l lows: 1000 t H M f o r B W R f u e l 10001 H M f o r P W R f ue l 10001 HM s hared betw een BW R & PWR.A l though the storage p ool w as f i l led with water a t the end of 1996, a decision is stil l awaitedwith respect to the l icence to operate. When operable storage capacity, however, will bel imited to 60% of the total capacity until reprocessing is available.3.3.6.3. Fukushim a D ai ichiThe AFR(RS) facility, completed October 1997,has been added to the Fukus hima Daiichireactor site to ov e r come a short-fall in on-site storage capacity.T he facility comprises of a 29 m x 11 m pool with a storage capacity of around12001 H M equivalent to about 6 800 f ue l assemblies.

1 8

7/29/2019 te_1100_prn

25/103

FIG. 2. Storage pool at Rokk asho reprocessing plant.

3.3.7. R us s i an FederationT he Russian Federat ion has 6 AFR facil it ies as detailed in Table V T h e development/designcriteria for Russian APR facilities is given in detail in A nnex B of Ref. [6].Twe n ty years operational experience of spent f u e l storage m water pools has demonstratedhigh corrosion resistance of intact fue l during long term storage In addition, no seriousdeterioration of defective f u e l occurred after several years of storage m water pools. W etstorage m T h e Russian Federation is p r o ve n technology. H o w e v e r , c ont inu ed improvement ofwet storage technology is sought through th e continued study of the beha viour of spent f u e lduring long-term storage (damaged fue l m particular) and through rerackmg m the storagepools in the operating plant .Fol lowing are typical examples of Russian RMB K an d WWER AFR facilities.3.3.7.1. LeningradLocated at the Leningrad NPP site the AFR (RS)storage facility was designed to hold 2000 tH M o f RMBK spent fue l . The storage area consists of f ive water pools (one is a reserve)designed for storing spent fuel in cans, each pool ca n accommodate up t o 4380 cans. Thecapacity of each can is one spent f u e l assembly.R M B K spent f u e l storage differs from the norm in that individual f u e l assemblies ar e sealedinto cans which are stored suspended j u s t above th e pool f loor m a f ixed slot, at a spacing of110 x 230 mm, in a metal beam placed across the pool This design of storage provides af ixed storage l a yout to ens ure su b cnticahty is maintained Th e be ams also provide th e

19

7/29/2019 te_1100_prn

26/103

necessary support for the pool lids to minimise water evaporation, an d operator access formanual fue l placement operations.

TABLE V. APR STORAGE FACILITIES IN THE R US S IAN FEDERATION

Location of the facil i tyLeningrad NPPSmolenskayaNPPKurskayaNPPNovo-Voronezh N PPKrasnoyarsk Mining an dChemical PlantAssociation Mayak

Fuel stored Design capacity Current( t HM ) inventory( t H M )RBMK-1000a

RBMK-1000RBMK-1000

WWER-1000bWWER-1000WWER-440BN-600

20002000200040 0

600056 0

2500 (with thestand-by b a y )400

1 7 0 011

20004 3 5

Operating period1 9 8 4 to present1 9 9 6 to present1 9 8 6 to present1 9 8 6 to present1 9 8 4 to present1 9 7 5 to present

1 B urn up 2 5 M S d /t H M ; 2 . 4 % enrichment; maximum cladding temperature 50C; 3 years ageing priorto storage.b Bu rnu p 50 MW d/t HM; 4 . 4 % enrichment; maximum cladding temperature 50oC; 3 years ageing priorto storage.

A typical f ue l receipt involves a loaded T K - 8 cask which after preparation has been placedinto th e unloading pool . The transport basket with 9 f ue l assemblies is then removed from th ecask and set on a intermediate shelf in the u nloading pool. These operations are performed byusing a 15 t cable trolley with a 5 t capstan and are remotely controlled from the operators'room.A 2 0 / 5 t bridge crane transfers th e transport basket to the deep section of the unloading poolwhere in d iv id ua l f u e l assemblies are removed and placed in cans. T he loaded can istransferred to the ma in pool hall where it is initially parked at the end of a c ha nne l where thepool cover has been removedFuel handling/placement in storage is performed by a 1 t-hoist which is height limited an dcontrolled from th e pool hall deck. Once th e loaded cans have been suspended on the beamsof th e metal deck of the pool hall th e opened portion in the deck is covered again to preventwater evaporation.3.3.7.2. O perating Ex perienceT he t ime required to transfer an d place f ue l into storage is approximately 12-18 hours. Thisincludes the return of the T K - 8 container from the AFR(RS) to the reactor unit, loading T K - 8with fue l , transport to the storage building and basket unloading from T K - 8 . A b o u t 8 hoursare required for all f u e l unloading from th e transport basket (with 9 fue l assemblies) into cansan d placing th e cans into storage. The collective dose for each f u e l loading operation isapproximately 1.9 mSv (as was predicted). The collective dose during ma int ena nc e an doperation is no more than 50 p.Sv/a (a specified value). T he pool water activity is very low a t3.3 Bq/kg.

20

7/29/2019 te_1100_prn

27/103

3.3,7.3. Krasnoyarsk A P R (OS) storage facilityThe storage facility is located at Krasnoyarsk RT-2reprocessing pla nt site. T he facility wasdesigned to hold up to 6000 t(U) of spent WWER-1000 n uclear f u e l in baskets in readinessfo r f u e l reprocessing in the RT-2 reprocessing p lan t ; yet to be commissioned (Fig. 3.).

C e n t r a l s t o r a g e f a c i l i t y a t t h e m i n i n g a n d c h e m i c a l p l a n tR e c e p t i o n a r e aS t o r a g e a r e aT r a n s p o r t h a l lR e l o a d i n g b a yC a s k w a g o n r e c e p t i o n s e c t i o nS t o r a g e b a y160/32 t c r a n e1 6 t c r a n e

9 . S p e c i a l 1 6 t c r a n e1 0 . R e l o a d i n g m a c h i n e1 1 . C a s k w a g o n1 2 . C a s k1 3 . G u a r d f e n c e1 4. Y o k e1 5 . H y d r a u l i c l o c k1 6 . S t o r a g e b a s k e t

FIG. 3. RT-2 pool.The facility comprises a reception, storage, an d process engineering areas.Transport cask receipt is not more than two casks per day and can be either TK-10's orTK-13's of 6 or 1 2 assembly capacity.T he storage pool consists of 15 bays, with on e reserve bay. The bays are connected with on eanother an d with th e unloading pool via a transport corridor. Each section can be separated bya removable hydraul ic lock and emptied independently f or maintenance an d repair. Basketswith fue l assemblies ar e placed on the pool floor. T he pool is a rectangular shaped structuremeasuring 11 300 x 3450 x 8400 mm and lined with stainless steel. It is separated from thetransport hall by a m etal deck with slots which ar e closed with f lap covers. T he slot openingsfacilitate the work of operating personnel an d affords a fixed pitch for rows of baskets sinceth e basket is carried on a rod by a 16-tcrane along the open slot in the deck. T he fixed pitch is1600 x 1600 x 1600 m m and,with a basket diameter of 1460m m , prevents the possiblecollision of baskets. The pool can accommodate between 69 to 84 baskets, however, capacityca n be increased if the central transport channel is also f i l led u p .

21

7/29/2019 te_1100_prn

28/103

Pool water temperature is maintained at 40C by an automatic water cooling system an dactivity levels controlled by a water purification system which is usu al ly operated once a weekp er pool.

Operating experienceTime required for unloading a cask of spent f u e l is 4 hrs. T he time for the basket loading andplacing into storage is 12 hrs. Permissible occupational dose l imit does not exceed thespecified va lue o f 50 ^Sv/a.

3.3.7.4. Novo- Voronezh NPPThe AFR (RS) W W E R - 1 0 0 0 facility is located at the Nov o-Vor on e zh N P P site. The designcapacity is 400 t HM. F u e l assemblies are stored in racks at a space of 400 mm in a t r iangulararrangement u nder the shielding water.The storage bays are located in a row on either side of the cask reception room. T hedecontamination area accommodates a facility for cask decontamination and painting. Thecask reception room has a stepwise configuration with tw o locations. In the u p p e r location th ecask lid is removed and in the lower location th e cask is un loaded. The storage baysc om m uni c a te w i th each other through op e n in gs with s luice gates. The storage bays arerectangular ferro-concrete structures with dimensions of 6200 x 4400 x 16 400 mm withdouble l ining an d leakage collection from behind the liner.F uel arrives by rail in TK-10 transport casks (capacity: 2.6 t HM or 6 WWE R -1000 f u e lassemblies) an d CASTOR casks (capacity 5.2 t HM or 12 W W E R - 1 0 0 0 f u e l assemblies) .Transport operations with casks are performed by a 160/32 t crane in the main hall. Caskloading/unloading operations are performed by a special f u e l handling machine. T he facility isin operation f or loading/unloading operat ions 24 hou rs per day for 20 days per year.T he facility is e q u i p p e d with cladding leak testing and gamma scanning for b u m u pdetermination. The cooling system is brough t into operation when th e pool water temperature rises to

45-50C. T he c lea ning system operates periodical ly; on average 24 hou rs/week/bay. The water qual ity is controlled to the fol lowing specifications: pH-no mor e than 4.3; HsBOs concentrat ion - no more than 13 g/kg; C l - ion content - n o more than 150 mg/kg; NHU - content - n o more than 50 mg/kg; The water activi ty is control led and does n ot exceed 10 Bq/kg.

The AFR ( O S ) storage facility at MayakT he interim AFR(OS) w et storage facility is located at the site of the Mayak ReprocessingPlant. This facility reprocesses WWER-440 an d research reactor (submarine) f u e l .The facility comprises a reception, storage, and process engineering areas. Fuel is stored inbaskets. A cross-section of the reception area is shown in Fig.4.

22

7/29/2019 te_1100_prn

29/103

Crane Q = l 5 l L = 9 m ^ Crane Q = 1 5 t L = 2 5 m

v > C a m s l e r b a s ke t

F I G . 4. Mayak reception pool.

3.3.8. SlovakiaThe interim AFR(RS) wet storage facility in Slovakia is located at the site of the JaslovskeB o h un ice NPP.3.3.8.1. BohuniceIn 1983construction started on an interim AFR(RS) storage pool at Bohuni c e NPP and i t wascommissioned in 1987. T he design capacity of the faci li ty is 6001HM (5000 f u e l assemblies) .It is expected that th e storage wil l be completely f u l l by the end of 1998.T he facil ity consists of three working bays and one reserve bay all interconnected by a waterc ha nnel . Th e s t r uc t ur e i n c l u d i n g all the service areas occupies a space of about45 m x 66 m. The pools ar e located at ground level an d there is a substantial sized receptionbay for transport containers. An overhead crane of 125/20 t capacity l i f ts th e casks into anun l o ad in g wel l and the f u e l is rem oved by a 15 t bridge crane into an assembly washing areabefore transferring to the storage bays.The facility is of standard USSR WWER design (see Kozloduy, Bulgaria), an d storesW W ER- 4 4 0 f u e l only .Operating experienceAl t hou gh th e design m a x i m u m wa t er temperature is 50 C, u n d e r normal operat ing con dit ionsobserved water te mp e r atur e s h a v e been in the 20-30 C range. T he facility only stores non-leakers. T he f u e l is stored in open baskets, 30 assemblies p er basket . No abnormal

23

7/29/2019 te_1100_prn

30/103

occurrences h av e been observed. T he specified l imits on w at e r activity an d t e m p e r a t u r e werenot exceeded. No water leakage has been observed.

Oth er relevant informationT he official pol icy is not to c o m m i t an y f u r t he r f u e l f or reprocessing. Preparation is b e i n gm a d e to e x t e n d th e exis t ing storage capacity (600 t H M ) an d t o consider h i g h e r d e n s i t yracking. This approach w o u l d replace th e exist ing 3 0 f u e l assembly baskets wit h basketscontaining approximately 50 assemblies. Analysis is being made of the pool f loor pad loadingand the cooling capabili ty for higher density racking. T he additional space cou ld exten d th estorage capacity to 2005.A n alternative is to investigate the dry storage option in the event that the extended poolcapacity is not achieved. There wil l also be a need for storage capacity for the second NPP atM o c h o v c e w h ich is expected to start up i n 1998.

3.3.9. SwedenS w e d e n has a single APR (OS) interim storage faci li ty (CLAB) located on the S i m p e v a r pp e n i n s u l a nea r th e Oskarshamn n ucl e ar p o w e r plant . T h e faci li ty dif fers from an y oth e r A P Rin that th e storage pool is ent irely located u nder gr ou nd in rock to overcome safety issues s u c has i m pa c t from aircraft .

CLABCLAB (first operation 1985) with a planned operational l i fe of around 60 years comprises on eabov e ground (site services, cask ha ndl ing an d f u e l preparat ion operations) and oneunderground s ec t i on ( fuel storage). A detailed description of the facili ty in c l ud in g t ec hni c a ldata an d design criteria is given in Annex A of Ref. [6].T h e receipt bui l d in g h as three receiving pool l ines, two of whic h are specially e q u i p p e d forreceiving th e TN17 M k2 cask. T he third pool which accommodates f u e l leakage detectione q u i p m e n t i s primari ly provided f or receipt of casks other than TN17 Mk2. T he receipt poolsare arranged so that cask immersion is into non-contaminated water prior to f ue l t r an s fe roperations into high den si ty f u e l canisters; capacity 25 BWR or 9 PWR f u e l assemblies.T he conversion to higher density f u e l canisters has increased th e total storage capacity for thefacility from 30001HM (as given in Reference 6) to 50001H M .Transfer of individual storage canisters to the un d e r g r o un d storage complex is by a f u e lelevator containing a water fil led cage; th e whole process being controlled remote ly . Onpassing from th e pools of the receiving section to the elevator shaft, th e elevator cage goesthrough a water trap. T he elevator shaft itself is not water-f i l led.T he storage complex is in a rock cavern 25-30 metres below the surface. It is 120 met reslon g, 21 metres wide and 27 metres high. It contains f o u r storage pools and one s mal lercentral pool connected to a t ransport channel . Each storage pool ca n hold u p t o 1250 t H M o fspent n ucle ar f ue l , giving a total storage capacity for the facility of 50001H M .T he storage pools have very thick concrete walls with extremely strong reinforcement. Loss ofwater from th e pools ca n only occur by evaporation in case of total loss of electricity s u p p l y

24

7/29/2019 te_1100_prn

31/103

an d cooling. T he pool wa t er will heat u p t o close to 100C. in about one we e k. If no feedwateris supplied, th e water level will drop to the top at the f u e l after about one month.The f u e l transport cask cooling system, where the greatest accumulation of radioactivity couldbe expected, has been equipped with a comprehensive system permitting remote removal ofcomponents by m e a n s of shielded casks.In order to reduce th e impact of possible airborne contamination in the receiving hall, th enormal air change rate is as high as five t imes per hour in the floor zone where th e operatorswork. If necessary, this ai r exchange rate can be extended to the total v o l u m e of the receivinghall by use of an extra vent i la t ion system.Operational experienceTo August 1997 CLAB had received approximately 900 transport casks, 840 containing f u e lan d th e remainder highly active core components (control rods etc.). T he f u e l inventorycorresponds to around 2 700 t HM comp r ise d of : B W R f u e l assemblies P W R f u e l assemblies M O X f u e l assemblies Agesta f ue l assemblies (PHWR) Canisters with f u e l debris.Part of the f u e l assemblies have b een reloaded from the original storage canisters to the newhigh density storage canister.Uncertainties such as crud release during dry cask cooling operations have been f ound to be50-100 t imes less than was assumed in the Final Safety Analysis Report (FSAR). This factm ay to a great extent be attributed to the good water che mistry in the Swedish reactors and thecorrosion resistant material in the turbine and feedwater systems resulting in relatively smallquan tities of crud.During th e first month of operation prob lem s with th e slot f i l ter an d backwash fi l ter arose. Bydeveloping a new backwash f i l ter an d changing the slot fi l ter to a sintered me ta l fil ter th eproblem w as resolved.A surprising fact is that the activity release to the storage pool water is more than 95% ionic.In the Final Safety Report, th e opposite was assumed predicting 90% to be in panicu late form.The activity released is 90-95% 60C o, the remainder being mainly 54 M n. Less than 1% is13 7Caesium.The activi ty concentration a t 2000 t H M is low,7 M B q / m 3, which however is higher thanexpected. The reason for this is the above mentioned high proportion of ionic release.Particles would have settled down on the pool bottom and would not have been observed inth e water samples taken f rom th e pools. Instead th e activity now remains in the water .The inf luence of pool water temperature on activity release rate was measured in 1988 byallowing th e pool temperature to rise from 28C to 36C. The resultant effect was a 2.1 foldincrease in activity concentration.3.3.9.1. Rad iation d osesDuring th e years 1986-1993, th e collective dose to CLAB staff an d contractors was between65 and 135 person mSv, which was about 25% of expected values in the FSAR. In the years

25

7/29/2019 te_1100_prn

32/103

1993-1994, th e yearly dose w as 100-115 person mSv. T he rising tendency can be explainedby a bui ld -up of activity in plant systems, increased maintenance work an d more staffmembers passing the dose detection limit. T he deve lopment is closely watched and measuresar e being taken and planned to break th e tendency.3.3.10. United KingdomThe UK has four operational AFR(OS) facilit ies al l located at the Sellafield reprocessing site.Pool operation differs from th e world wide practice in that the pools are purged by a once-through water f low with discharge to the sea; after conditioning. A summary of the APRstorage facil it ies in the UK is given in Table VI.TABLE VI. SUMMARY OF CURRENT APR FUEL HOLDINGS IN UK [8]

FacilityOFSPA BSPFH PT R & S

Fuel typeLW RAGRMagn ox /AG RLWR/AGR

Design capacityt H M2300144526503800

Inventoryt H M111914459442969

Commissioned/first operation1964198119851988/9

OFSP: oxide f u e l storage poolABSP: AGR buf fer storage poolFHP: Fuel handling poolTR&S: Thorp receipt and storage3.3.10.1. Oxide fuel storage pool (OFSP)This is now the oldest of the operational storage pools at Sellafield an d dates from 1964 wh e nit comprised a wet receipt bui lding an d f our open topped storage bays. T he facility wasextended to meet business needs in the late 1970s, with th e addition of a new receipt bui ldingand a f if th storage bay (1980).Early receipts were in basketed wet and dry transport flasks where th e f u e l was transferredu p o n receipt into open topped pond storage skips.Owing to problems associated with ' c rud ' migration during storage and within transportflasks, which in turn led to excessive radiation doses being detected at pool an d flask surfaces,methods of fue l containment have been developed. These u lt imately led to the introduction ofmulti-e lement bottles (MEBs) for transport an d storage. (For details se e Appendix A.)LW R fue l has now been stored in this facility for in excess of 20 years. Monitoring of longstored f u e l has con clud e d it to be in good condition.3.3.10.2. A GR bujfer storage pool (ABSP)This store was b u i l t as a b u f f e r for AGR f u e l whilst th e THORP reprocessing facilities werebeing built . It was the last of the open topped storage ponds to be bui l t at Sellafie ld an dbecame operational in 1981. T he facility has a single dry receipt cell where f u e l housed in atransport/storage skip is transferred from a shielded wet transport flask into a pool storagecontainer. Containers are stored f looded stacked u p t o three high in the single pool with acapacity for up to 600 containers.

26

7/29/2019 te_1100_prn

33/103

Major operational changes since commissioning of this pond have been th e receipt ofdismantled f u e l , increasing storage capacity from 500 t HM to a round 1500 t HM, and theint roduct ion of the f u e l cladding corrosion inhibi tor sodium hydroxi de b y d osin g th e poolwa t er to pHll.5. T he suscept ibi l i ty o f AGR fue l to cladding corrosion has be e n reported aspart of the Co-ordinated Research Programme on Behaviour of s pent f u e l d u r i n g long-termstorage (BEFAST) [7].Since the introduction of corrosion inhibitors and stringent control of water chemistry, nofur ther pin perforations have been discovered over a thirteen year period.

3.3.10.3. Fuel handling plant ( F H P )Com m i s s i oned in 1985, th e facility comprises three dry receipt cav e s , three m a i n storageponds for the storage of Ma gnox and AGR f u e l s , three su b p o n d s , dec a nni ng c e l l s f or M a g n o xfue l and AGR dismantl ing l ines. All ponds and sub ponds ar e interconnected in a b u i l d i n g 150metres long by 25 metres wide raised above ground level .Fuel receipt an d storage is similar to the ABSP, the main dif ferences ar e that th e pool storagecontainers are predosed in the receipt cell to (pH13, (Cl" + SO42" ) < 0 . 5 p p m ) . A GR f u e l isreceived from reactor stations in fifteen e l e me n t f u e l skips . M agnox con ta in e r s are sealed andul la ged with ni trogen gas prior to storage to min imise th e release of activity a nd c la ddi ngcorrosion products to the b u l k p o n d water.Pool water within th e facility is predosed to pHl 1.4 and cooled to 15 C by refrigeration u n i t sto minimise activity leach rates.Ma gnox f u e l is stored for up to 18 mont hs . Prior to reprocessing, Magnox c onta i ners aretransferred to a s ub pond containing a skip washer. Here, th e co n t a in e r is p u r g e d to removes o lub le act ivity, and tumble washed to remove cladding corrosion p r od ucts . E f f l u e n t s f romthese processes are directed to the Site Io n Exchange E f f l u e n t Plant (SDCEP). The f u e l is thendecanned (c ladding removed) before cask transfer to the Magnox Reprocessing P lant .Unlike Magnox receipts, AGR containers ar e stored f looded for up to 180 days to allow forheat decay to me e t th e f u e l dis ma nt l er heat loading l imits . A 3:1 f u e l consolidation is achievedb y d is ma nt l ing , th e rods being placed into 285 mm diameter by 1 me tr e s tainless steel slottedcans. (A more detai led description of the rod consolidation process at BNFL is given inAppendix B.) The cans are transferred into twenty compartment skips and either returned tostorage in FHP, t ransferred to the ABSP or transferred directly to THORP receipt an d storagefor reprocessing.

3.3.10.4. T H O R P receipt and storage (TR&S)Commissioned in 1988, THOR P Receipt an d Storage (TR&S) is the latest APR to be b u i l t atSel lafie ld . Cons truc ted to the latest internat ional bui lding standards the design of the faci l i ty isbased around BNFL's practice of f u e l containerisation for both t ransport and storage.TR& S is primarily used for the receipt and intermediate storage of LWR f u e l prior toreprocessing, but it is also used to store a reprocessing b u f f er , up to 166 containers, of AGRf u e l . T he fac i l i ty comprises tw o main b u i l d ings , th e receipt bui l d in g an d t h e p on d hal lb u i l d i n g . T he tw o b u i l d i n g s ar e interconnected by an access ch an n e l , and since 1995 th e P o n dH al l B ui l d in g has been connected to TH