Nuclear energy materials Energy FINAL.pdf · 2007-12-05 · Materials UK Energy Review 2007 Nuclear Energy Materials Research 3 2.0 Introduction There are currently about 440 commercial

Nuclear energy materials

Materials UK Energy Review 2007Report 3 - Nuclear Energy Materials

Materials UK Energy Review 2007Nuclear Energy Materials Research

Contents

1.0 Executive summary

2.0 Introduction

3.0 Key socio-economic drivers

4.0 Technological drivers for research

5.0 Research opportunities and challenges5.1 Approach5.2 Detailed research issues

6.0 Key barriers to progress

7.0 Recommendations

References

AuthorsI Cook UKAEA Culham

C English Nexia Solutions

P Flewitt Magnox Electric Limited and Bristol University

G Smith University of Oxford


1

Executive summary1.0

Focussed, integrated andwell-coordinated materialsresearch will make a majorcontribution to promotingUK strategic objectives forsupporting existing fissionpower plants and developingand supporting new powerplants - in the short termfission and, later, fusion.

Such a materials researchprogramme, together with theexpertise and infrastructure that itwill generate, will benefit andinvolve a wide range of governmentagencies concerned with energy andenvironmental issues, as well asmajor industrial and supply-chaincompanies.

Key factors driving the need for researchThe key socio-economic drivers areenvironmental (especially reducingCO2 impact); economic (obtainingmaximum value for money fromboth existing and new plant);improving security and diversity ofelectricity supply; ensuring socialacceptability; exploiting fission-fusion synergies; and exploitingsynergies with the nuclear marinepropulsion programme. Technically,most of the items in the resultingResearch Agenda can be expressed interms of the value of extending, andreliably predicting, the lifetimes ofmaterials and components indemanding and potentiallydamaging environments.

Accordingly, for fission, research isneeded in the areas of fuels, fuelcladding, pressure vessels, corecomponents and cooling systems;containment systems; componentsin reprocessing plant and wasterepository materials. For fusion,although most of the systems aredifferent, many of the materialsissues, and most of the researchmethods, are very similar.

UK focus for the agendaThe focus of the Strategic ResearchAgenda should be confined to areasspecifically addressing UK needs andopportunities, using UK strengths,but effectively linked to Europeanand global research and informationnetworks and experimental facilities(Recommendation 1). Analysis showsthat the key UK problems for studyinclude corrosion and erosion;environmentally assisted cracking;radiolytically-induced mechanismsof embrittlement, crack initiationand crack propagation; creep-fatigueinteractions; irradiation creep andswelling; thermal cycling; joiningand interface technologies; effects ofhelium; very long term degradationof storage materials; and non-destructive examination methods.

Improved materialsare crucial toinnovation in theenergy sector,including fission andfusion. Majoradvances are beingmade in materialsscience - in bothunderstanding andtechniques.

The key infrastructure and facilitiesrequired in order to carry out suchwork are access to irradiationfacilities and/or proxy irradiationsources; “hot” working laboratories;autoclaves for environmental testingat plant operating temperatures;creep-fatigue testing equipment;advanced materials characterisationinstrumentation; large-scalecomputer modelling facilities; acomprehensive set of archivedmaterial from decommissionedfission reactors for study; andresources for a “knowledge captureexercise” to capture the wealth ofexperimental data and personalknowledge which is rapidlydisappearing from this U.K.industrial sector.

Priorities for UK applied researchFour immediate promisingopportunities have been identifiedthat play to UK strengths and wouldyield substantial progress on keycross-cutting issues. Theseopportunities arise because of theexistence of synergies inexperimental and modellingtechniques. Accordingly, it isrecommended that new or enhancedmulti-disciplinary research


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programmes, integrated across thewhole of the supply chain, should belaunched into: mechanisms of in-service and in-repository corrosionand degradation of materials;predicting the behaviour of weldedstructures subjected to hightemperatures and complex loadings;predicting irradiation damage effectsin fission and fusion materials; andthe development of new andimproved methods for non-destructive monitoring andevaluation of materials in service.

(Recommendation 2). This appliedresearch needs to be integrated withthe enabling research summarisedbelow.

Underpinning research needsSubstantial new opportunities existfor productive research in theabove priority areas, enabled byutilising and developing the recentand continuing major advances inexperimental methods formaterials characterisation andunderstanding-based multi-scalemodelling of materials behaviour.

Materials which need to be studiedinclude austenitic, ferritic and oxide-dispersion strengthened steels;zirconium; graphite; fission fuelmaterials; refractory metals such astungsten; and repository materials.

Effective implementationThe key barriers to research progressare lack of financial and humanresources; the greatly reducedphysical infrastructure and facilitieswithin the UK for nuclear research;and lack of stability of the regulatoryand financial regimes. Stability infunding is essential, as is ‘ownership’of the Strategic Research Agenda by aconsortium of key institutions,accompanied by clear leadership anddirection, and drawing in theexpertise and resources of industry,research institutes, universities,regional development agencies, andthe proposed National NuclearLaboratory (Recommendation 3).

Initially, the strategic researchprogramme should be developed byexploiting existing CoreCompetencies in the UK and

harnessing them in multi-disciplinary Flexible Teams that canbe focussed on the critical problemsand issues (Recommendation 4). Theresearch should be reciprocallylinked to skill base refreshment todevelop and retain expertise andknowledge: research that uses the UKinventory of pertinent skills and datais one of the most effective ways -perhaps the most effective way - tomaintain/refresh such UK assets(Recommendation 5). A nationalknowledge management capability isrequired to ensure that maximumbenefit is obtained, both fromexisting knowledge and from thatgenerated during future research (Recommendation 6).

The fission and fusion materials R&Dneeds to be linked to other areas ofmaterials R&D where there aresignificant synergies to be exploited -especially materials for advancedfossil-fuel power plants (Recommendation 7).


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Introduction2.0

There are currently about 440commercial power-generatingnuclear reactors operating in30 different countries.Between them, these plantshave a total capacity of372,000 MWe, and supply16% of the world’s electricityrequirements. The USA hasthe largest number ofoperational reactors (104).France is in second place,with 59 reactors, and relieson nuclear power for a largershare of its electricity supplythan any other country(78%).

An additional 30 reactors arecurrently under construction invarious parts of the world, and morethan 80 further reactors are atvarious stages of planning anddevelopment, notably in China,Japan, Korea, India and Russia. Inaddition to power-generating units,there are about 280 research reactorsin 56 different countries. A further220 reactors are used in marinepropulsion systems.

Construction of new power-generating nuclear reactors in NorthAmerica and Western Europe cameto an almost complete halt after theaccidents at Three Mile Island (1979)and Chernobyl (1986). However,since that time there have beensubstantial advances in reactortechnology, and in particular thedesign of safety systems. The so-

called “Generation III” advancedlight water reactor designs, which arecurrently available, incorporatepassive safety systems that aretriggered automatically in the case ofan emergency, and do not requireauxiliary power sources for theiroperation. “Generation III+” and“Generation IV” designs are alsounder development, which promisecleaner and more economicalnuclear power towards the middle ofthe present century. One of theadded advantages of nuclear reactorsis that they can be used to producehydrogen via electrolysis or thermalreactions, and can thus play a part ina future hydrogen economy, as wellas in the direct production ofelectrical power.

There is also a major internationaleffort to develop nuclear fusion as anew source of power. If successful,this would remove many of thelong-lived nuclear waste problemsassociated with fission reactors. Aninternational reactor-scale fusiondevice (ITER), is beginningconstruction at Cadarache, in theSouth of France. However, even withoptimistic assumptions, it is likely tobe several decades before fusionpower plants become availablecommercially.

In the U.K., there are currently 19operational power-generatingnuclear reactors, which produce 18%of the nation’s electricity. Most ofthese reactors are old, andapproaching the end of their usefulworking lives. No nuclear reactorshave been commissioned in the U.K.since 1995 (Sizewell B), and none are

Nuclear power is ofcrucial importance tothe future globalenvironment, becauseit permits large-scale,reliable electricitygeneration withnegligibly small CO2

emissions.

currently under construction. As aresult, the contribution of nuclearpower to U.K. electricity supply ispredicted to drop to 7% by 2020,and to zero by 2035, unless newconstruction is undertaken.

Improved materials are crucial toinnovation in the energy sector,including fission and fusion. Majoradvances are being made inMaterials Science - in bothunderstanding and techniques.Accordingly, focussed, integrated andwell-coordinated materials research,planned to take maximumadvantage of the existing knowledgebase together with newly emergingexperimental and theoreticalmethods, would make majorcontributions to promoting UKstrategic objectives [1, 2, 3] for:

• Supporting existing fission powerplants - especially the economicoperation of these, and the safeextension of their lifetimes;

• Decommissioning these plants(and plants now closed) andmanaging the waste materialsarising;

• Developing and supporting newpower plants (in the short termfission and, later, fusion) andadvanced fuel cycles - aiming atimproved economics, safety andsecurity, environmental impacts oroperational characteristics;

• Ensuring public confidence in theabove;

• Exploiting synergies with researchfor marine propulsion plant.

Introduction2.0


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The delivery of these strategicobjectibes and the expertise andinfrastructure that it would generatewould benefit (and involve) a widerange of agencies serving the publicinterest, notably: the governmentdepartments, agencies and researchorganisations concerned with energy,environmental and defence issues;organisations responsible for safety,Health & Safety Executive and theNuclear Industry Inspectorate(HSE/NII), waste immobilisation,storage and cleanup (NuclearDecomissioning Authority (NDA)and the Environment Agency). Inaddition, such a programme wouldbenefit and involve major industrialcompanies (such as British Energy,Rolls Royce and BNFL), supply-chaincompanies (such as Serco Assuranceand Nexia Solutions), and leadingmaterials-related universitydepartments and researchorganisations such as TWI.

The discussion in this reportillustrates how such materialsresearch can effectively beundertaken. The focus is on the UK-specific opportunities, needs,challenges and strengths, togetherwith the importance of makingeffective use of links to Europeanand global research, informationnetworks and experimental facilities.

Certain broad themes predominatein this discussion, namely:-

• The need to predict withconfidence the behaviour andproperties of materials indemanding environments.

• The value of accelerating thedesign and characterisation ofimproved materials.

• The great opportunities affordedby new scientific developments tomore effectively achieve the aboveobjectives.

• The need to refresh, develop andsustain key UK expertise andfacilities in all elements of thesupply chain (academia,government R&D, industrial R&D,plant operators and regulators) ina cost-effective way.

These themes are also characteristicof many of the materials researchissues for fossil fuel plant whichhave been highlighted separately inFossil-fuelled Energy MaterialsReport.

The crucial factors driving the needfor materials research in this sectorcan be classified into two groups, thebroad socio-economic drivers, andthose arising from technologyrequirements. Each of these will bediscussed in turn.

The focus is on the UK-specific

opportunities, needs,challenges and

strengths...

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Key socio-economic drivers3.0

EnvironmentalThe imperative need is to mitigateclimate change without inhibitingworld economic development.Recent publications, such as theStern Review [4] (by the former Vice-President and Chief Economist ofthe World Bank) and theIntergovernmental Panel on ClimateChange [5] have removed most ofthe residual uncertainties about thecost, reality, causation and pace ofclimate change. Typicalenergy/environment/economicscenarios [4, 5] have projectedcontinued economic development(especially of currently less-developed or developing countries),and associated growing energyconsumption, throughout thiscentury, accompanied:

• during roughly the first third ofthis century, by a levelling-off ofcarbon emissions; and

• during the subsequent two thirdsof the century, by the reduction ofcarbon emissions to levelsapproaching - or lower than -current levels.

Extending the lifetimes of existingfission power plants; building a newgeneration of fission power plants,aiming at features likely to maximisesocial acceptance; and bringingfusion power to practical fruition -will all make major contributions tosolving the global environmentaland economic [2] problems. As willbe shown, materials research is at theheart of the resulting developmentneeds [6, 7]. Furthermore, even fornext generation ‘turn-key’ plantsthat do not require significantmaterials development, expertise isrequired in the UK to ensureappropriate assessment of detaileddesigns [8] and subsequentregulation of operations.

EconomicsViable economics remains a keyrequirement. This is a furthermotivation for lifetime extensions ofexisting fission plants - as extendedplants have by far the lowestavoidable costs of all powergeneration methods - and forobtaining and maintaining assuranceof predicted long lifetimes of newlydesigned and built plants. Moregenerally, materials performance iskey to maintaining confidence in thetotal engineering system. For fusionpower plants economics motivatesthe development of materials forhigh temperature operation andprolonged component lifetimes, inorder to secure high availability.

The regulatory environmentIntegral to the economic andenvironmental drivers is properattention to plant safety andregulation. The non-prescriptiveregulatory regime in the UK, wherethe plant operator has todemonstrate the safety of the plantrather than comply with externallyprescribed design/operating codes,imposes significant requirements onthe level of expertise in all elementsof the supply chain [9]. The operatormust be both an intelligent customerfor, and an intelligent owner of, theentire system. A continuing supplyof appropriately trained personnel istherefore essential.

The crucial factorsdriving the need formaterials research anddevelopment in thissector can be broadlyclassified as follows...

CRUCIAL FACTORS

• Environmental• Economics• The regulatory

environment• Security and diversity

of supply• Maximising Social

Acceptability

Security and diversity of supplyThis provides an obviousjustification of new build fissionand, in the longer term, fusion, andfor lifetime extension of existingplants, but with no materialsresearch implications further to theearlier points.

Maximising Social AcceptabilityThe successful demonstration ofgood solutions to decommissioningand waste management issues isessential for maximising publicacceptance. It is important to be ableto show the reliability of the newmaterials and systems involved.Research to forward a variety ofmaterials developments, innovativesolutions and predictability would behelpful to support this debate [10].


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Technological drivers for research4.0

Specific material challenges applyalso to facilities associated withreprocessing, and wasteimmobilisation and management. It is clear that materialsresearch/expertise is required onseveral timescales.

• During the next 5 years: to maintain and most effectivelyexploit the existing fleet of fissionpower stations (gas-cooled Magnoxand AGRs, and a water-cooledPWR); to address issues associatedwith the operation of re-processingplant and short-term wastestorage; to assess and regulate newbuild power stations; and todevelop optimised materials andcomponents for testing in a fusionmaterials irradiation facility.

• Over a 5-10 year time span:increased focus on the new buildand fusion issues, which placesincreasing emphasis on developingmaterials to withstand hightemperatures and high levels ofirradiation damage; together withthe need to address re-processingand de-commissioning issues andbe able to predict the long-termevolution of the behaviour ofrepository wastes.

• Over a 10-20 year horizon: to exploit with optimum efficiencythe operation of the fleet of newbuild fission power plants; todevelop emerging/advanced fissionreactors; to predict withconfidence the behaviour ofrepository material over periods ofmany centuries; and to finalise theselection of materials for a fusiondemonstration power plant.

The main components which areincorporated in the activities whichcomprise the fission fuel cycle areshown in Figure 1. This figureillustrates the wide range ofcomponents involved. Theenvironment to which materials aresubject depends on the componentbut may involve exposure to hightemperatures, neutron irradiation,external (and internal) stresses, andcorrosive liquids.

For existing plant the primary driverfor materials research is the need topredict reliably the through-lifeproperties of components such asthe reactor pressure vessel or certaincore components that experiencehigh temperatures and/or areexposed to high fluxes of neutrons.In addition, advanced materials withimproved corrosion or oxidationperformance are still beingdeveloped for components such asfuel cladding. Similarly, the need tominimise the cost of re-processing,decommissioning and wastemanagement is leading to increasedmaterials research into specificmaterials degradation mechanismsrelevant to immobilisation materials,such as glasses and ceramics, andcontainment vessels in chemicalplant supporting re-processing.

The research agenda isdriven by the need toreliably predictoperating plantservice life andoperate plantoptimally.

Key considerations are thedegradation of materialsproperties, and timedependent failure processesfor structures andcomponents, including jointsand welds. In the case of newand more advanced powerplants, it is necessary tooptimise new materials toextend those lifetimes, basedon understanding of themechanisms of specific time-dependent phenomena suchas irradiation damage, creep,corrosion, and sub-criticalcrack growth, and themechanisms of theinteractions between them.

Figure 1. Main activities and components of thefission fuel cycle


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Cut-away view of an intermediatelevel waste container

For advanced fission reactor systemsthe main driver is for materialsresearch to develop new materialswhich are resistant to deleteriousdimensional and mechanicalproperty changes caused by exposureto high temperatures and highfluences of neutrons.

Overall, R and D is needed in theareas of: fuels; fuel cladding; pressurevessels; core components includinggraphite moderators and coolingsystems; containment systems;components in reprocessing plant;decommissioning and wasteimmobilisation and repositorymaterials.

An illustration of the power and utility of modern materials modelling methods. This shows a computationalsimulation of about a million atoms of iron in a distorted configuration of the crystal lattice such as can beproduced by bombardment by neutrons. Such distortions are ultimately responsible for creep, swelling, etc. Theforces between the atoms have been calculated by a new approach that takes into account the magnetism ofiron at the atomic level. The colouring of the atoms reflects the strength of their magnetic moments

For fusion, most of the systems aredifferent. However, there is a widerange of commonalities in thematerials issues. There is an overlapin the classes of materials employedand in the effects responsible formaterial and componentdegradation, and the researchmethods - experiments andmodelling - are similar for a broadrange of issues. Specific additionalproblems arise in the case of plasma-facing components, due to damagecaused by the impacts of high-energyions.

For existing plant the primary driverfor materials research is the need to

predict reliably the through-lifeproperties of components...

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Interior of a remote handling cave. [Courtesy of Nexia Solutions]


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Research opportunities and challenges5.0

5.1 Approach

The researchopportunities andchallenges are not justrelated to identifyingkey research issuesassociated withcurrent and futureplant. It is importantalso to reverse thedecline in the UKcapability in this area.

Well-focussed materials researchprogrammes must play their part inhelping to promote the developmentof individuals who can enter allelements of the supply chain toensure the creation and execution ofprogrammes to address crucial issues,and lead the assessment andregulation of both new designs andplant life extension of existing plant.To be truly effective an enhancedindustry/government/academicpartnership is needed, whichaddresses both the short termcommercial and the strategicimperatives - it is critical for successthat an organisation, or consortiumof organisations, ‘owns’ this strategy.

We address these needs bydeveloping a strategic researchagenda. This is initially based onanalysing existing UK CoreCompetencies (in research institutes,academia and industry with itsassociated supply chain) andexploiting these in Flexible Teamsthat can be focussed on the criticalproblems and issues. The nature ofthe research opportunities is suchthat the flexible teams need to bemultidisciplinary in character. In asecond phase, a case for furtherdevelopment of these corecompetencies will be made.

A strategic, and broadly common,research approach to most of thecrucial materials problems andunderlying phenomena is required.The approach proposed here ispredicated upon four majorconsiderations:

1 Bombardment by neutrons,characteristic of fission and fusionpower plants, gives rise initially toatomic scale changes in theinternal microstructure of amaterial, primarily throughdisplacing atoms and generatinghelium and hydrogen atoms bytransmutation reactions. Theeffects then propagate up throughthe length scales to generate aseries of further changes. The primary research challenge isthat of passing reliably, viaunderstanding and modelling,from observations at the smalltemporal and spatial scalescharacteristic of such changes tothe large scales characteristic ofthe in-service environment. It isimportant to maximise theamount of information which canbe inferred from small samples andmodelling.

Figure 2. Elements of a strategic, and broadlycommon, research approach to most of the crucialmaterials problems and underlying phenomena.


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2 It is essential to develop andvalidate mechanisticunderstanding, which enables dataobtained in an experimentalsimulation of certain aspects of thein-service environment to be usedto predict the performance ofmaterials over the lifetime of acomponent. Indeed, central to thisapproach is the value of amechanistic understanding of themicroscopic effects in order tounderstand change in bulkproperties and the need to buildpredictive models of componentperformance.

3 Material properties have to bepredicted for components incomplex situations involvingexposure to different combinationsof high temperature, stress, fluxesof neutrons and gamma radiation,and gaseous, aqueous or othercorrosive environments. Therequirements include a fullerunderstanding of the behaviour ofcomplex welded engineeringstructures.

4 Repository materials, whichinclude cements, ceramics, glassesand metal alloys, will be storedover very long periods. As aconsequence, it is necessary todevelop innovative solutions andunderwrite safe storage over thesetimescales. Therefore materialshave to be selected, and propertiespredicted, based upon dataobtained from shorter term teststhat are representative of theappropriate geological conditions.

These considerations demonstratethe need for a combined modelling-validation-understanding approachto meet the engineering challengesof the industry at large. Theelements of such an approach areshown in Figure 2.It should be noted that there aremany common features in methodsof experimental and theoreticalinvestigation between fission andfusion materials issues, andsubstantial overlaps in the types ofmaterial and challengingphenomena. In addition, dependenton plant design, there are a widerange of materials ranging fromthose of general industrial usagesuch as ferritic and austenitic steelsto those more particular to thenuclear industry such as zirconiumalloys, graphite, ceramics and oxidefuels.

Although the issue of irradiationdamage is exclusive to the fissionand fusion sectors, similarconsiderations to those summarisedabove apply more widely: topredicting the response of materialsto other challenges such as hightemperature operation - where thereare significant synergies with workneeded for advanced fossil-fuelpower plants - and to the design ofimproved materials.

These considerations allow us tobroadly classify the corecompetencies and facilities that arerequired namely:

• Experimental techniques fordetermining the changes in (bulk)physical, dimensional, mechanicaland corrosion properties ofmaterials occurring either duringservice, or during simulation tests.

• Experimental characterisationtechniques to determine themicrostructural changes in in-service or simulation tests. Thesetechniques include methods suchas tomographic microscopy, in-situtime-resolved (as well asconventional) electron microscopy,scanning probe, three-dimensionalatom probe, focussed ion-beamsfor imaging and milling, highresolution energy loss electronspectroscopy, extended X-rayabsorption fine structuremeasurement, X-ray magneticdichroism, neutron scattering andspectroscopy, and electronspectroscopy for chemical analysis.

• A toolbox of theoretical modellingtechniques that enable simulationof materials behaviour across awide range of scales. Suchtechniques include densityfunctional theory, atomisticdynamics, kinetic Monte Carlomethods, and dislocationdynamics, validated by theexperimental observations.

• Proxy irradiation facilities, such asion-beams, focussed particularlyon model validation.Unfortunately, only minimalfacilities of this kind are nowavailable within the UK. This putsa considerable premium on accessto European and global facilities. Itshould be noted that importantion-beam facilities that arededicated to materials research arebeing developed by the Universityof Manchester at the DaltonCumbria Facility and at theUniversity of Salford.

• Assured access to irradiationfacilities in materials test reactors(MTRs). This is particularlyimportant for carrying out longterm tests to validateextrapolations based on short termtest data or proxy irradiation andmodelling. There are no MTRs inthe UK and it is currently difficultto get access elsewhere in theworld for the right kind ofirradiation, or for sufficient lengthof time (for example, to enable theinteraction of irradiation withcorrosion to be studied).

High level waste containers. [Courtesy of Nexia Solutions].


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Figure 4. Identification of cost-effective and productive research programmes.

It is important to note that there arenow major opportunities to beexploited from the new advances inmaterials characterisation methodsand in modelling. Achievements thatwould have been thought impossiblea decade ago are becoming routine.

The process for determining theissues to focus on initially isillustrated in Figure 3.

The final step is to identify cost-effective and productive researchprogrammes that will energiseexisting and potential teams, asillustrated in Figure 4.

Figure 3. Outline of the process for determination of the initial research programme

Studies of pertinent materials havebeen widely undertaken over thepast sixty years, and it is importantto maximise the benefit of thesestudies to future programmes ofresearch by appropriate data miningand knowledge capture exercises.Similarly, it is vital to identify long-term exposed materials fromsurveillance programmes ordecommissioned plants/componentsthat should be retained forexamination and may be used forfuture validation of models.

The maintenance in the UK of anadequate base of skills andknowledge is essential for the mosteffective prosecution of the strategicresearch. This is not by any meansan exclusively UK problem, it isfairly general throughout Europe andthe world. In this connection, itshould be noted that:

• Research that uses the UKinventory of pertinent skills anddata is one of the most effectiveways - perhaps the most effectiveway - to maintain/refresh such UKassets.

• The strategic research needs to beeffectively linked to European andglobal research and informationnetworks and experimentalfacilities. Currently, only thefusion materials researchprogramme has achieved this levelof integration. Similar integrationis required for the other areasidentified in this report.

• A national knowledgemanagement capability is requiredto ensure that maximum benefit isobtained, both from existingknowledge and from thatgenerated during future research.

• Facilities that allow theexamination of activated orcontaminated material. Such acapability may be provided by theproposed National NuclearLaboratory (NNL), based onfacilities at Sellafield. In thecontext of research to be proposed,it is important that these facilitiesbe made available, through NNL,for research carried out byresearchers other than NNL staff.


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5.2 Detailed research issues

The critical materialsproblems and issuesassociated with UK presentand future plant are classifiedinto three broad categories,namely behaviour at hightemperature, irradiationdamage and behaviour(including stability) atambient - or near ambient -temperatures. The mostimmediate challenges andopportunities associated withthe materials of main interestare identified in the Tableopposite. The key methodsfor solution of materialsproblems and key gaps in UKcapabilities are alsosummarised.

In addition the safe and economicoperation of nuclear power plantstructures and components over thecomplete life cycle is reliant oneffective and reliable non-destructive examination and plantmonitoring. Over the service lifethere is a need to monitor anydegradation of the structures andcomponents, including materialsproperties that can underminecontinued safe performance. Thedevelopment of improved non-destructive methods for monitoringthe behaviour of materials duringservice is a further area of keyimportance. Within the fuel cycleshown in Section 4 these span short(fuel manufacture) to geologicaltime-scales for the storage of waste.

Behaviour at hightemperature

Austenitic, ferritic andODS steels.High-nickel alloysZirconium Alloys.Tungsten.Graphite

Creep-fatigueinteractions.Thermal cycling.Joining and interfacetechnology.

Modelling and itsvalidation.Advanced materialscharacterisation.Advancedmeasurement andtesting techniques.Advanced plantmonitoring techniques

Modelling validated bymicroscopiccharacterisation, plantservice data and long-term experiments.Exploit researchsynergies for fission,fusion and fossil-fuelplant materials.

Lack of creep-fatiguetesting facilities.Lack of irradiationfacilities

Primary and secondarycircuit in LWRs,advanced reactors andfusion. Near corecomponents in AGRs.Divertors and blanketsin fusion.

Irradiation damage

Austenitic, ferritic andODS steels.Zirconium alloys.Graphite.Fission fuels.Tungsten.

Irradiation Creep.Swelling. Irradiationenhanced segregation,crack propagation andembrittlement.Irradiation assistedcorrosion andenvironmentaldegradation.Effects of helium.Joining and interfacetechnology.

Modelling and itsvalidation.Advanced materialscharacterisation.Proxy irradiation (e.g.ion beams).Advancedmeasurement andtesting techniques.Advanced plantmonitoring techniques

Modelling validated bymicroscopiccharacterisation, proxyirradiations, plantservice data and long-term experiments.Exploit researchsynergies for fissionand fusion plantmaterials.

Lack of irradiationfacilities.

In core components inAGRs, LWRs, advancedreactors. Blankets anddivertors in fusion

Behaviour/stabilityat near-ambienttemperatures

Repository materials,including cements,glasses and polymers.Austenitic, ferritic andODS steels.High-nickel alloysZirconium alloys.Graphite.

Corrosion-oxidation.Irradiation damage.Joining and interfacetechnology.Environmentallyassisted crackingRadiolytically induceddegradation

Modelling and itsvalidation.Advanced materialscharacterisation.Advancedmeasurement andtesting techniques.Advanced plantmonitoring techniques

Modelling validated bymicroscopiccharacterisation, plantservice data and long-term experiments.

Autoclaves forcorrosion testing andthe study ofenvironmentallyassisted crack growth.Archived materialsfrom surveillance anddecommissioning.Lack of irradiationfacilities

Components withinchemical plantsMaterials/componentsin storage beforereprocessing.Waste packagesCabling and sensors

Main materialsof interest

Main problems

Key methods forsolution ofproblems

Most promisingimmediateopportunities

Key gaps incapabilities

Components



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It clearly makes no sense to mount aUK programme to address all theseissues. The existing CoreCompetencies in the UK areparticularly strong in the areas ofmaterials characterisation,mechanistic understanding of failureprocesses, and materials modelling.Four critical issues are identified asNext Steps that can be addressedeffectively by UK researchers. Thesecritical issues have been selectedbecause their resolution will advanceimmediate UK strategic interests, andplay to UK strengths. Although eachof these programmes is primarilyfocussed on a sub-set of issues andmaterials, they would contribute toall three of the columns in thepreceding Table.

A Understanding the mechanisms ofin-service and in-repositorycorrosion and degradation ofmaterials such as austenitic andferritic steels, cements, glasses andpolymers, taking account of thetotal environment. This wouldcombine expertise and interests inacademia, industry andgovernment researchorganisations.

B Fabrication techniques (such aswelding or pre-service surfacetreatments) may have an impacton in-service performance that isnot well understood. A researchprogramme should be focussed onpredicting the behaviour of weldedstructures subjected to hightemperatures and complex loadingduring service. There is apotentially valuable link tomaterials for advanced fossil-fuelplants.

C A fission-fusion materials researchprogramme aimed at irradiationdamage issues, to underwritelonger term operation of plants.This would exploit synergiesarising from the commonproblems, common experimentaland theoretical methods ofinvestigation and the overlap ofkey materials, and would takeadvantage of recent majoradvances in research methods.

D Non-destructive methods are usedto underwrite installed plantintegrity by ensuring that anyflaws are within the designspecification. Inspections are alsoundertaken at regular intervalsover the service life via prescribedmaintenance schedules. Researchis required on these technologiesas greater demand is placed uponinspections. Many other potentialchanges to material performancearise from the total serviceenvironment. Traditionally, toolssuch as installed surveillancesamples, selective removal ofmaterial for examination andtesting, corrosion monitoring, etc.have been used. There is a need todevelop the ability to monitorchanges on-line and define safelimits. Requirements range fromimproved quantitativemeasurement of microstructuralchange, to enhanced imageanalysis and information recovery,and the use of smart materials thatcan be installed within criticalregions.

It should be noted that theseprogrammes are multidisciplinary innature, requiring the investigation ofa wide variety of issues, ranging fromstress analysis in large scalestructures to the effects of coolantchemistry on corrosion behaviour. Itwill be necessary to link togetheracademia, research organisations andindustry in order to achievemaximum benefits from thisresearch.

SiliconManganeseNickelCopper

2nm

Atom map showing the presence of a 3nmirradiation induced cluster containingcopper, manganese, nickel and silicon atomsin a reactor pressure vessel steel.[Courtesy of Nexia Solutions Ltd]


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Key barriers to progress6.0

In the fission industry, lack ofconfidence in the stability of futureregulatory regimes (licensing andplanning; and fiscal/financialinstruments designed to suppressclimate changing emissions fromother sources) has producedartificially high risk premiums forthe construction of new fissionpower plants and extensions of theoperations of existing plants, and sohas severely suppressed (to very low

Currently, in the UK,the prime barriers tothe successfulexecution ofproductive research inthe fission field relateto resources; financial,human and physical.

levels) the commercially-fundedresearch that might otherwise havedeveloped in response to financialsignals such as the price of carbon.This perception is not likely tochange rapidly. Publicly-fundedresearch has not filled the gap left bythis market failure, being also at verylow levels with little continuity orstability.

The UK skills base in these areas is inurgent need of refreshment. Thevolume of available expertise hasbeen declining for many years, andis dispersed among manyinstitutions. There is little effectivecontact with global research andinformation networks, whichthemselves have generally sufferedcomparable declines. The availability of facilities in the UKfor irradiating and examiningmaterials for the experimentalvalidation of understanding andmodelling has been in steep decline,in parallel with similar declinesthroughout much of the world. Onlylimited arrangements have been putin place for the effective sharing ofaccess to the world’s limited facilitiesor for pooling of related research

A cutaway drawing of the core of a 600 Megawatt fusion device, ITER, which is beginning construction in France. The partners in ITER are Europe, Japan, China,India, Russia, Korea and USA. Although fusion and fission power plants are different in many respects, there is a large overlap in the classes of materials theyemploy, the effects that limit the lifetime of materials, and the research methods used to gain the understanding needed to optimise materials performance.

programmes. In particular, it isdifficult to arrange for material to beirradiated in facilities outside theU.K., especially when longer-termstudies of properties such asradiation-assisted creep and creep-fatigue interactions are required.Assured access to such facilities(including materials test reactors)and to equipment for theexamination of radioactive samples,is essential. Any future strategy mustalso make the best possible use ofthe capabilities within front-lineuniversity material departments.Organisations such as the proposedNational Nuclear Laboratory have akey role to play, and it is importantthat their facilities should be madeavailable to outside researchers. Theexploitation of synergies with thefusion materials researchprogrammes is also essential (seebelow).

The situation is rather different forfusion materials research. Thoughthere is no commercially-fundedresearch, and the UK publicly-fundedresearch programme is small, inother respects it is in better shape.Funding is stable, and there is aunifying core of research activities inone institution (Culham), in closeinteraction with a penumbra ofrelated work in leading UKuniversities and RTOs, and formingan integral part of a coordinatedEuropean programme whichincludes access to irradiationfacilities. A major projectedinternational fusion materialsirradiation facility - IFMIF - would beof wide benefit if located in the UK.Though fusion and fission are verydifferent in many respects, there arevery substantial commonalities inthe materials areas, and majorpotential benefits could be obtainedin both fields from the exploitationof common research programmes.

It is worth noting that the SternReview [4] concluded that theeconomics of climate change and itsmitigation mandate at least adoubling of rates of expenditure onenergy research, specifically citing(on page 363) energy materials asone of four priorities for scientificprogress.


16

Recommendations7.0

1 The focus of the research agendashould be confined to areasspecifically addressing UK needsand opportunities, using UKstrengths, but effectively linkedto European and global researchand information networks andexperimental facilities.

2 Four immediate promisingopportunities have beenidentified that play to thestrengths of UK CoreCompetencies and would yieldsubstantial progress on key cross-cutting issues. Theseopportunities arise because of theexistence of synergies inexperimental and modellingtechniques. Accordingly, it isrecommended that new orenhanced multi-disciplinaryresearch programmes, integratedacross the whole of the supplychain, should be launched into:

• mechanisms of in-service and in-repository corrosion anddegradation of materials;

• predicting the behaviour of weldedstructures subjected to hightemperatures and complexloadings;

• predicting irradiation damageeffects in fission and fusionmaterials;

• development of new and improvedmethods for non-destructivemonitoring and evaluation ofmaterials in service.

3 Stability in funding is essential,as is ‘ownership’ of the StrategicResearch Agenda by a consortiumof key institutions, accompaniedby clear leadership and direction,and drawing in the expertise andresources of industry, researchinstitutes, universities, regionaldevelopment agencies, theproposed National NuclearLaboratory, etc..

4 Initially, the strategic researchprogramme should be developedby exploiting existing CoreCompetencies in the UK andharnessing them in multi-disciplinary Flexible Teams thatcan be focussed on the criticalproblems and issues. At a laterstage, a case for furtherdevelopment of CoreCompetencies can be made.

5 The research should bereciprocally linked to skill baserefreshment to develop andretain expertise and knowledge.Research that uses the UKinventory of pertinent skills anddata is one of the most effectiveways - perhaps the most effectiveway - to maintain/refresh suchUK assets.

6 A national knowledgemanagement capability isrequired to ensure thatmaximum benefit is obtained,both from existing knowledgeand from that generated duringfuture research

7 The fission and fusion materialsresearch needs to be linked toother areas where synergy can beexploited, especially to materialsfor advanced fossil-fuel powerplants. There would be majorbenefits to the UK if the plannedinternational fusion materialsirradiation facility (IFMIF) werelocated here, and every effortshould be made to bid for it ifthe opportunity arises.

References

1 UK DTI, ‘The Energy Challenge: Energy Review Report 2006’, July 2006.

2 UK DTI, Energy White Paper 2007, ‘Meeting the Energy Challenge’, May 2007, www.dti.gov.uk/energy/whitepaper

3 UK DTI, ‘The Future of Nuclear Power: the Role of Nuclear Power in a Low Carbon UK Economy’, May 2007

4 Sir Nicholas Stern, ‘Stern Review: the Economics of Climate Change’, UK Govt. report, CUP January 2007 andwww.sternreview.org.uk

5 Intergovernmental Panel on Climate Change, Reports: ‘The Physical Science Basis’; ‘Impacts, Adaptation and Vulnerability;‘Mitigation of Climate Change’, 2007, www.ipcc.ch

6 (i) ‘A Technology Roadmap for Generation IV Nuclear Energy Systems’, US DoE, Nuclear Energy Research AdvisoryCommittee and the Generation IV International Forum, December 2002. (ii) R.E. Stoller et al., ‘Workshop on AdvancedComputational Materials Science: Application to Fusion and Generation IV Fission Reactors’, US DoE, 2004.

7 I. Cook, ‘Materials Research for Fusion Energy’, Nature Materials, vol. 5, no. 2, p. 77, February 2006, and references citedtherein.

8 An Essential Programme to Underpin Government Policy on Nuclear Power, P. Ruffles (ed.), BNFL Publication, July 2003

9 HSE Safety Assessment Principles for Nuclear Facilities 2006 Edition Redgrave Court Bootle Merseyside L20 7HS.

10 NDA Research & Development - Needs, Risks, and Opportunities - Issued April 2006 Version 1


Acknowledgements

Many of the topics developed hereare based on themes that emergedfrom a workshop meeting on“Materials for Nuclear Energy in the21st Century”, which was held atWolfson College, Oxford in October2005, and on later discussionsinvolving UKAEA Culham, BNFL andManchester University. Subsequentinput from many colleagues inuniversity, industry and publicinstitutions is gratefullyacknowledged.

The views and judgements expressed in this report reflect the concensus reached by the authors and contributors and do not necessarily reflect thoseof the organisations to which they are affiliated. Whilst every care has been taken in compiling the information in this report, neither the authors orMatUK can be held responsible for any errors, omissions, or subsequent use of this information.

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Cover photo: Sizewell B Power Station. [Courtesy of British Energy]

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