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
Overview on Occupational Exposure during Decommissioning of NPPs
Evolution of average annual collective effective dose, based on data of a majority of
worldwide NPPs
13th IRPA Congress 2012, TS6b, RP Experiences & Challenges, J. Kaulard / B. Brendebach 3
0
50
100
150
200
250
300
350
400
450
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2,00
4,00
6,00
8,00
10,00
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1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 2010
No
. NP
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Ave
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ose
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r N
PP
un
itin
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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
Overview on Occupational Exposure during Decommissioning of NPPs
Evolution of average annual collective effective dose for German NPPs
13th IRPA Congress 2012, TS6b, RP Experiences & Challenges, J. Kaulard / B. Brendebach 4
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
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Ave
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an
nu
al c
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ose
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r N
PP
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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
Overview on Occupational Exposure during Decommissioning of NPPs
13th IRPA Congress 2012, TS6b, RP Experiences & Challenges, J. Kaulard / B. Brendebach 5
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
Overview on Occupational Exposure during Decommissioning of NPPs
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
13th IRPA Congress 2012, TS6b, RP Experiences & Challenges, J. Kaulard / B. Brendebach 6
“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
13th IRPA Congress 2012, TS6b, RP Experiences & Challenges, J. Kaulard / B. Brendebach 7
Selected Experiences from Past and Current Projects
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
13th IRPA Congress 2012, TS6b, RP Experiences & Challenges, J. Kaulard / B. Brendebach 8
Operation
Post-Operation
Dismantling SE Preparation
Safe Enclosure
Dismantling
Construction
Final State
© E.ON Kernkraft GmbH
Selected Experiences from Past and Current Projects
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
13th IRPA Congress 2012, TS6b, RP Experiences & Challenges, J. Kaulard / B. Brendebach 9
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
Selected Experiences from Past and Current Projects
Multiple Phase Approach
Example for a multiple phase approach
13th IRPA Congress 2012, TS6b, RP Experiences & Challenges, J. Kaulard / B. Brendebach 10
© E.ON Kernkraft GmbH
Phase 1Phase 2 Phase 3
Phase 4
generator hall support buildingreactor building
Selected Experiences from Past and Current Projects
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
13th IRPA Congress 2012, TS6b, RP Experiences & Challenges, J. Kaulard / B. Brendebach 11
© GNS
© EWN
© B. Jünger
© B. Jünger
Selected Experiences from Past and Current Projects
RP & Selection of Dismantling & Decontamination Techniques
Generic selection process
13th IRPA Congress 2012, TS6b, RP Experiences & Challenges, J. Kaulard / B. Brendebach 12
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
13th IRPA Congress 2012, TS6b, RP Experiences & Challenges, J. Kaulard / B. Brendebach 13
... 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
13th IRPA Congress 2012, TS6b, RP Experiences & Challenges, J. Kaulard / B. Brendebach 14
Thank You for Your Attention!