Radiation Protection during Decommissioning of … tue boisdale Kaulard TS6b.1.pdf · Radiation Protection during Decommissioning of Nuclear Facilities – Experiences and Challenges

Radiation Protection during Decommissioning of

Nuclear Facilities –

Experiences and Challenges

IRPA Glasgow

13th International Congress of the

International Radiation Protection Association

13 – 18 May 2012

Technical Session TS6b: Decommissioning

Joerg Kaulard, Boris Brendeback

Gesellschaft fuer Anlagen- und Reaktorsicherheit (GRS) mbH

Germany

Content

Overview on Occupational Exposure during Decommissioning of NPPs

“Daily” Radiation Protection Challenges during Decommissioning

Selected Experiences from Past and Current Projects

Conclusions and “Future” Radiation Protection Challenges

13th IRPA Congress 2012, TS6b, RP Experiences & Challenges, J. Kaulard / B. Brendebach 2


Evolution of average annual collective effective dose, based on data of a majority of

worldwide NPPs


0

50

100

150

200

250

300

350

400

450

0,00

2,00

4,00

6,00

8,00

10,00

12,00

1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 2010

No

. NP

P u

nit

s

Ave

rage

an

nu

al c

olle

ctiv

e d

ose

pe

r N

PP

un

itin

man

.Sv/

a

Year

Average collective dose of NPP in operation

Average collective dose of NPP in cold shutdown / underdecommissioning

No. of NPPs in operation

No. of NPPs in cold shutdown / under decommissioning


Evolution of average annual collective effective dose for German NPPs


0

5

10

15

20

25

0

1

2

3

4

5

6

7

8

9

10

1969 1971 1973 1975 1977 1979 1981 1983 1985 1987 1989 1991 1993 1995 1997 1999 2001 2003 2005 2007 2009

No

. of

NP

P u

nit

s

Ave

rage

an

nu

al c

olle

ctiv

e d

ose

pe

r N

PP

un

itin

man

.Sv/

a

Year

Average annual collective dose for NPP under decommissioning

Average annual collective dose for NPP in operation

No. of nuclear power plants under decommissioning

No. of nuclear power plants in operation



0

5

10

15

20

25

30

35

1971 1973 1975 1977 1979 1981 1983 1985 1987 1989 1991 1993 1995 1997 1999 2001 2003 2005 2007 2009

An

nu

al c

olle

ctiv

e d

ose

in m

an.S

v/a

Year

Total annual collective dose

Year of post-operational phase /decommissioning

Post-operational phase /

decommissioningOperational phase

Example on the evolution of the annual collective effective dose during life cycle of

a NPP in operation and decommissioning


Some key observations

• (Average) Annual collective effective dose for NPPs in operation higher than

for NPPs under decommissioning

depends inter alia on the reactor type and decommissioning concept /

approach used

open question, whether this will change for modern reactor designs

• Annual collective effective dose of a NPP under decommissioning varies from

year to year and depends inter alia from

annual work load and project plan (structure & schedule) and progress of work

radiological conditions (e.g. contaminations, quality of system

decontaminations)

• Both, utility and contracted personnel involved

typically large number of contracted personnel active during whole year


“Daily” Radiation Protection Challenges during Decommissioning

From a far distance – “Decommissioning” = “extended Outage”

no other “daily” challenges than during outage

But from a closer distance – aspects more relevant / new now requiring

• flexible planning, preparation & work control and establishment of oversight on all

processes under conduct

• early involvement of RP professionals

• well RP trained personnel to appropriately respond

new “daily” challenges other than during outage, inter alia

continuous change of the facility status (technical, radiological relevant)

increased number of (long-lasting) work activities with interdependencies

access to workplaces, inaccessible during operation

new / improved techniques to conduct / speedup decommissioning activities

(need for) deviations from plans on the conduct of work

high volume of radioactive / non-radioactive material flow

replacement of technical barriers by administrative ones (incl. PPE)

but: Decommissioning RP measures are mainly the same as for operation



Experience in general shows: radiation protection during decommissioning depends

inter alia on

• radiological situation of the nuclear facility

• complexity of the nuclear facility

• conceptual decisions as e.g.

decommissioning strategy

project structure / multiple phase approach

sequence of decommissioning activities

conduct of measures to reduce the

radioactive inventory

(e.g. full system decontamination)

cutting of component in-situ or ex-situ,

especially removal of large components

pre-selection of techniques

waste management concept


Operation

Post-Operation

Dismantling SE Preparation

Safe Enclosure

Dismantling

Construction

Final State

© E.ON Kernkraft GmbH


Multiple Phase Approach

Multiple phase approach

• serves to divide large projects into smaller parts and to reduce complexity

• allows stepwise planning of phases

first to be detailed

following less detailed until they will be commenced (and approved by

regulatory body)

• helps to stage the process of radiological characterization

information for later phases can be evaluated during current phases

• requires a clear adjustment of the individual phases


12-5 -4 -3 -2 -1 0 1 2 3 4 5 6 7 8 9 10 11

year of decommissioning

operational phase residual operationstrans.

phase

phase 1

phase 2

phase 3

phase 4

release from regulatory control

conventionaldismantling dismantling of non-nuclear facilities

construction and operation of an interim storage facility for radioactive waste

decommissioning and dismantling

phases


Multiple Phase Approach

Example for a multiple phase approach


© E.ON Kernkraft GmbH

Phase 1Phase 2 Phase 3

Phase 4

generator hall support buildingreactor building


Removal of Large Components

As an alternative to in-situ dismantling and cutting of

large components

• removal of the whole component as one piece

• dismantling at a different position then the build-in

position (ex-situ)

within the nuclear facility

at the site in a specific facility

off-site, e.g. by a service provider

• advantages

optimization of the schedule

improvement of radiological conditions

(not necessarily resulting in lower doses!!)

• closely related to waste management strategies

Special form of removal of large component

• removal and long term storage before dismantling

“decay storage” to take benefit from radioactive decay


© GNS

© EWN

© B. Jünger

© B. Jünger


RP & Selection of Dismantling & Decontamination Techniques

Generic selection process


project strategies

( RP aspects on high level)

available techniques

pre-selected techniques

pre-selection

set of techniques to be considered

during detail work planning

assessment and comparison

of techniques

Potential decision factors, inter alia

• decommissioning strategy

• release of radioactive material

• radiological / conventional worker protection

• radiological conditions at the working place

• regulatory requirements

• know-how on the nuclear facility

• own experiences on the use of the technique

• technical work specification

• applicability / type of the technique, incl.

• dismantling capacity

• safety aspects

• infrastructure / workspace needed

• (de-) installation / maintenance time

• aspects of costs

• rad. waste generation and disposal roots

• aspects of clearance

More strategic factors and considerations

Detailed RP consideration as part

of the detailed work planning

Conclusions and ...

In the past decommissioning of nuclear facilities was performed successfully (and

safely) to reach defined end states

“Daily” challenges require flexible planning & work control, management of many

processes and an early involvement of RP professionals

Recent experiences show inter alia

• A multiple phase approach helps

to manage large and complex decommissioning projects and

to solve the problem of radiological characterizations during planning

• Large component removal is a way to optimize project plans and to improve the

radiological conditions for dismantling (but leads not necessarily to lower doses)

• RP is considered on a high level in project strategies and in detail during work

planning on base of selected techniques

worker protection will become ALARA during the detailed work planning

Today, for (mostly) any technical question related to decommissioning

• either standard solutions exist or can be adapted, or

• can be individually developed for the specific situation


... and “Future Radiation Protection Challenges”

In general terms, RP challenges seem to be under control for most situations,

except for accident situations ( special challenge to remove spent fuel)

“Future Radiation Protection Challenges” may relate to

• the radiological characterization (before approval by regulatory bodies) which

sets the base for the preparation of decommissioning plans and

forms the basis the waste and material management strategies

as

it’s difficult to decide on the appropriate level of detail

to gain the information needed

• the final radiological survey, which demonstrates that the final end state was

reached as

especially in case of sites remaining contamination either of natural origin

strongly vary or of artificial origin exist, both resulting in practical problems for

a background identification and reduction

further need on experience feedback among RP experts, e.g. by means of

ISOE, IAEA / NEA


Thank You for Your Attention!

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Radiation Protection during Decommissioning of … tue boisdale Kaulard TS6b.1.pdf · Radiation Protection during Decommissioning of Nuclear Facilities – Experiences and Challenges