For Official Use
NEA/NSC/WPNCS/DOC(2003)3
Organisation de Coopération et de Développement Economiques
Organisation for Economic Co-operation and Development
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NUCLEAR ENERGY AGENCY
NUCLEAR SCIENCE COMMITTEE
NEA/NSC/WPNCS/DOC(2003)3
For Official Use
Working Party on Nuclear Criticality Safety
Expert Group on Burnup Credit Criticality
Summary Record of the Eleventh Meeting
9 September 2002
NEA Headquarters, Issy-les-Moulineaux, France
English - Or. English
Document complet disponible sur OLIS dans son format d'origine
Complete document available on OLIS in its original format
NEA/NSC/WPNCS/DOC(2003)3
Working Party on Nuclear Criticality Safety
Eleventh Meeting of the Expert Group on
Burnup Credit Criticality
9 September, 2002
NEA Headquarters, Issy-les-Moulineaux, France
SUMMARY RECORD
1
Welcome
The meeting was attended by twenty-seven participants (see the list of participants in Annex 1). Mikey
Brady Raap opened the meeting and welcomed the participants.
2
Approval of the agenda (All)
The agenda was approved after adding two presentations (Mikey Brady Raap on burnup credit experiments
and Roger Blomquist on source convergence issues).
3
Review of actions from the previous meeting
Ali Nouri reviewed the status of the actions agreed upon at the previous meeting which concerned mainly
the completion of on-going benchmarks. Phases IV-A and IV-B are almost completed. The progress of
Phase II-C is reviewed in the next paragraph.
4
a)
Status of the benchmarks
Phase II-C results (J-C. Neuber)
The objective of this phase is to study the effect of axial burnup profile asymmetry on the calculated keff
and fission distributions. Jim Gulliford presented a paper prepared by Jens-Christian Neuber who could not
attend the meeting. The aim of the presentation was to propose a methodology for the analysis of Phase IIC results. In his study, Jens-Christian Neuber first tried to define synthetic characteristics of the axial
profiles and of the calculated fission distributions. He then tried to correlate the characteristics of these two
groups of functions (the fission distributions on the one hand and the axial burnup profiles on the other
hand). Expectation, variance, skewness and kurtosis were considered as good quantities to characterise
fission distributions (or the ratio of these distributions to the fission distribution obtained when assuming a
uniform burnup profile). Other parameters, including the profile asymmetry coefficient introduced last year
by Hiroshi Okuno, were considered as appropriate characteristics for the axial burnup profile. JensChristian Neuber then applied this methodology to the results he obtained at Framatome ANP and derived
some trends which, however, contained some fluctuations. He discussed the limitation of this methodology
and proposed to apply it to the bulk of results.
Mark DeHart commented that he was not sure whether the latest results he had submitted were
incorporated in the analysis. Other participants expressed their wish to see the latest compilation of results
in order to check their entries. An action was set on Jim Gulliford to ask Jens-Christian Neuber to make the
data available and to check with him on the way the analysis will be performed.
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b)
Source convergence issues in burnup credit
Roger Blomquist presented an overview of the activity of the Expert Group on source convergence
analysis. He also investigated source convergence issues in typical burnup credit configurations. To this
aim, he considered two typical configurations from the BUC Phase II-C benchmark, namely case 2 where
the axial profile is the most asymmetric and case 13 with regular asymmetry, and tried several source
guesses. In both cases, it is necessary to skip several hundred generations in order to converge the sources.
Following this presentation, a discussion took place on whether the convergence of sources is important for
criticality calculations or should the focus be put on the convergence of the eigen value. Several opinions
were expressed without a consensus on the subject being reached.
c)
Additional safety related cases related to PWR and BWR BUC
Dennis Mennerdahl presented a paper entitled “A simple nuclear criticality safety concept that can be very
difficult to implement”. The presentation covered several burnup credit issues including the mixing of
PWR and BWR spent fuel assemblies, the effect of horizontal burnup profile (within the fuel assembly).
The general conclusion of the paper is that the use of burnup credit in criticality safety might add
complications to the safety demonstrations and consequently particular care should be taken in the use of
approximations. In fact, the combination of conservative approximations might become non-conservative.
d)
Phase IV-A final report (G. O'Connor and reviewers)
Greg O’Connor provided an update on the preparation of Phase IV-A report. The report is almost finalised
with the reviewers’ comments being taken into account. The report will be published in the beginning of
2003.
f)
Phase IV-B final report
Liem Peng Hong presented the final draft of the Phase IV-B report. Additional results were received from
PSI, GRS and ORNL and were incorporated. Some information on ORNL results is still missing and Mark
De Hart was asked to provide them as soon as possible. The structure of the report was presented. The
reviewers have sent their comments, and the benchmark co-ordinator is considering them. The final report
will be published in early 2003.
g)
Note on MOX Inventory Prediction Calculations
Greg O’Connor reported on the analysis of Pu-239 composition results. He showed that the spread of the
results was independent of the geometry. He then investigated the origin of Pu-239 discrepancies using the
simplest pincell model. The calculation method used in his analysis is a step-wise combination of a MonteCarlo calculation (for flux calculation) followed by a depletion calculation. He showed that the calculated
Pu-239 composition was sensitive to the following parameters: standard deviation of the Monte-Carlo
calculation, number of burnup steps per calculation, number of fuel pin shells at which the flux is scored in
the Monte-Carlo calculation and then used in the depletion calculation. However, these findings were
considered as being code-specific. Kenya Suyama agreed to perform similar sensitivity studies using the
MVP code.
Kenya Suyama questioned the results obtained by JNC using the CASMO code and wondered whether the
approximations used in this code are valid. Susumu Mitake agreed to have a closer look to the way the
calculations were run.
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h)
AER benchmark: Final Evaluation of CB4 VVER Benchmark (L. Markova)
Lida Markova presented the analysis of the CB4 benchmark. A transport cask similar to the CASTOR
440/84 was considered. This cask contained VVER-400 spent fuel originating from the KOLA nuclear
power plant in Russia. The fuel has an initial enrichment of 4.4% and an asymmetric axial burnup profile.
The aim of the benchmark was to study the effect of the axial burnup profile on criticality calculations.
Both keff and fission distributions were considered. Ten solutions to this exercise were submitted and the
results were fairly consistent (about 0.5% difference in the calculated keff values). Taking the axial burnup
profile into account resulted in an increase of keff for high burnups (about 1.5% for 40 GWd/t burnup and 5
year cooling time). For lower burnups, the uniform burnup distribution lead to more reactive
configurations.
5
Activities of the OECD/NEA/CSNI on burnup credit (B. Kaufer)
Barry Kaufer (NEA Nuclear Safety Division) presented an overview of the activities of the Committee on
the Safety of Nuclear Installation (CSNI). He informed the participants that the Working Group on
Operating Experience is carrying out a survey on burnup credit implementation among member countries.
This compilation will help identifying needs for the standardisation of practices in this area. Mikey Brady
Raap commented that the outcome of this survey is of interest to the Expert Group as it might help
identifying areas of mutual interest. Barry Kaufer agreed to report on the outcome of the survey at the next
meeting.
6
a)
BUC national programs
US/NRC PIRT: Process Identification and Ranking Tables (M. DeHart)
Mark DeHart presented a summary of the Phenomena Identification and Ranking Table (PIRT) process
sponsored by US Nuclear Regulatory Commission (Office of Regulatory Research for Spent Fuel Project).
This process has been implemented to help NRC research in identifying areas that need most attention in
terms of methods development and data. The NRC Nuclear Material Safety and Safeguards division,
responsible for transportation licensing, is the customer of the research efforts. The panel consists of 16
technical experts in criticality safety and/or burnup credit, from industry, research and academia.
Additionally, seven international participants are on the panel. The NRC invited some panelists, while the
Nuclear Energy Institute, a nuclear industry advocacy organisation in the US, recommended others. ORNL
was responsible for organising PIRT meetings and presenting technical information, although is not
represented on the panel. PIRT I, held in May 2000, focused on: (1) ranking of issues related to the physics
of neutron multiplication in a PWR and (2) four areas of ISG-8r1 for which a more firm technical basis is
desired: cooling time, enrichment offset, axial burnup profiles, and burnable poisons. Panelists were asked
to provide written recommendations to the NRC on these four topics after the meeting. The panelists
endorsed the value of removing the restriction on the aforementioned areas and provided input to initial
recommendations from research activities. The result of the process is available as a NUREG report. A
second revision of ISG-8 is under preparation
b)
BUC Critical Experiment at Sandia National Laboratory
Mikey Brady Raap described the NERI brunup credit experiments recently performed at Sandia National
Laboratory. The experiments configuration includes a driver core composed of water moderated UO2 rods
(4.31% enriched uranium) and other fuel elements in which foils can be added. Rhodium was inserted in
these elements as foils. Different experimental configurations were obtained according to the thickness of
the foils which varied from 0 mm (no Rh) to 0.1 mm.
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c)
Update on the BUC activities in KOREA (Hae Ryong Hwang)
Hae Ryong Hwang presented an update on burnup credit activities in Korea. On fuel storage issues, he
informed that the re-racking of the storage pool in the KORI-3 plant was achieved in 2002. The KN-12
cask is now designed for in-site transport which was previously restricted to four assemblies. On waste
issues, the decision is still pending for the construction of a low-level waste storage site.
d)
Burnup Credit in Japan
Yasushi Nomura presented the status of burnup credit activities in Japan. He informed the meeting that the
implementation of burnup credit in Japan faces resistance. The only plant where burnup credit was
accounted for is the reprocessing plant of Rokkasho (storage and dissolver). There is no practical plan for
the implementation of burnup credit in other storage or transport configurations. Experiments to support
the validation of the burnup credit in the dissolver configuration are planned at STACY by the end of this
fiscal year.
Susumu Mitake made a short presentation on the comparison of different burnup credit assumptions.
Starting with fresh fuel he studied the reactivity change due to heavy nuclide depletion (uranium only, then
with plutonium isotopes) and to the formation of fission products. The reactivity decreases by 12.6% when
considering the depletion of uranium and plutonium isotopes (7 isotopes). With the fission products
contribution (42 isotopes contributing to 99% of the total absorption) the reactivity decrease is limited to
7.5%. He concluded that the evaluation of isotopic compositions of uranium and plutonium isotopes in
spent fuel is of key importance in burnup credit issues.
e)
Burnup credit in the UK
Jim Gulliford informed the Group that the regulatory body in the UK is assessing a transport cask
configuration where the use of burnup credit (15 GWd/t) was claimed. When only fresh fuel is placed in
the transport cask, the multiplication factor of the configuration will exceed the allowed limit although the
cask will still be sub-critical.
7
Status of the transfer of SFCOMPO to the NEA
Kenya Suyama presented the status of the Spent Fuel Composition database SFCOMPO, a database
developed at JAERI for the storage and retrieval of spent fuel composition data originating from
commercial PWR and BWR reactors. The transfer of the database to the NEA web site was completed and
the database can be accessed at: http://www.nea.fr/html/science/wpncs/sfcompo. No password is required
for the retrieval of data. Plans for the development of a management interface to the database are being
discussed by the NEA and JAERI. This would allow the continuation of the compilation effort started at
JAERI. Kenya Suyama informed the participants that he will suggest the organisation of a special session
within the ICNC’2003 conference in order to encourage spent fuel composition data holders to submit
them to the NEA for compilation in SFCOMPO.
8
Follow-up of the activities of the Expert Group
Mikey Brady Raap led a discussion on possible new activities to be carried out by the Expert Group. In
particular, she proposed the compilation of a document summarising the findings of the benchmark
activities and addressing important burnup credit issues such as: the physics of BUC and the related
calculation and validation problems, safety consideration, bias and uncertainties, risk assessment, margins.
A proposal was put forward to define a further benchmark to study the effect of absorbers on burnup credit.
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Caroline Lavarenne, Jim Gulliford and Mark DeHart volunteered to discuss the proposal and to prepare
with a draft benchmark description before the next meeting.
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NEA/NSC/WPNCS/DOC(2003)3
Annex 1
List of participants
CZECH REPUBLIC
MARKOVA, Ludmila
Ustav jaderneho vyzkumu Rez
Theoretical Reactor Physics
Nuclear Research Institute
25068 REZ
+420 (2) 6617 2291
mar@nri.cz
FRANCE
BERGE, Ludovic
ludovic.berge@edf.fr
EDF - Recherche et Développement,
92141 Clamart Cédex,
+33 1 47 65 29 31
1, av. du Général de Gaulle,
LAVARENNE, Caroline
IRSN/DPEA/SEC
B.P. 17
F-92265 FONTENAY AUX ROSES CEDEX
+33 1 58 35 78 67
caroline.lavarenne@irsn.fr
Jérôme RABY
+33 (0) 1 58 35 99 25 jerome.raby@irsn.fr
IRSN/DPEA/SEC
Institut de Protection et de Surete Nucleaire
60-68, avenue du Général Leclerc
BP 6
92265 FONTENAY AUX ROSES
GERMANY
GMAL, Bernhard
+49 (0)89 32004 494gma@grs.de
Gesellschaft fuer Anlagen- und Reaktorsicherheit
Postfach 1328
D-85739 GARCHING
WEBER, Wolf-Juergen
+49 89 / 3 20 04 – 4 web@grs.de
Gesellschaft fuer Anlagenund Reaktorsicherheit
Forschungsgelaende
Postfach 1328
D-85739 GARCHING
JAPAN
LIEM, Peng Hong
NAIS Co., Inc.
416 Muramatsu
Tokai-mura, Naka-gun
Ibaraki-ken 319-1112
+81 29 270 5000
liemph@nais.ne.jp
MITAKE, Susumu
NUPEC
Institute of Nuclear Safety
Fuel Cycle Facility Safety Analysis ec.
17-1 Toranomon 3-chome
Minato-ku, TOKYO 105-0001
+81 (3) 4512 2773
mitake@nupec.or.jp
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NEA/NSC/WPNCS/DOC(2003)3
NAITO, Yoshitaka
President
NAIS co. inc.
416 Muramatsu, Tokai-mura
Naka-gun, Ibaraki-ken 319-1112
+81 29 270 5000
ynaito@nais.ne.jp
NOMURA, Yasushi
Fuel Cycle Safety Evaluation Lab.
JAERI
2-4 Shirakata-Shirane,Tokai-mura,
Naka-gun,Ibaraki-ken 319-1195
+81 (0)29 282 5834
nomura@popsvr.tokai.jaeri.go.jp
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NEA/NSC/WPNCS/DOC(2003)3
KOREA (REPUBLIC OF)
HWANG, Hae Ryong
Radiation Safety Analysis Group
Korea Power Engr. Co., Inc.
P.O. Box 148
Yusong
DAEJEON 305-353
+82 (42) 868 2214
hae@ns.kopec.co.kr
RUSSIAN FEDERATION
TSIBOULIA, Anatoli
+7 08439 98938
tsiboulia@ippe.rssi.ru
Institute of Physics and Power Engineering (IPPE)
Fiziko-Energiticheskij Inst.
1, Bondarenko Square
249020 OBNINSK
SWEDEN
MENNERDAHL, Dennis
E. Mennerdahl Systems
Starvägen 12
S-183 57 TAEBY
+46 (0) 8 756 58 12
dennis.mennerdahl@ems.se
SWITZERLAND
GRIMM, Peter
Paul Scherrer Institute
CH-5232 VILLIGEN PSI
+41 (56) 310 2071
peter.grimm@psi.ch
UNITED KINGDOM
BROOME, Peter E.
British Nuclear Fuels plc
R101, Rutherford House
BNFL Risley
Warrington WA3 6AS
+44 (0)1925 833 022
peter.broome@bnfl.com
GULLIFORD, Jim
BNFL plc
R101 Rutherford House
Risley WA3 6AS
EDGE, Jane
+44 19467 79007
BNFL
B170, Sellafield,
Cumbria,
+44 1925 83 3450
jim.gulliford@bnfl.com
jane.a.edge@bnfl.com
NUTTAL, Michelle
+44 1925 83 5917
michelle.nuttall@bnfl.com
BNFL
R101, Rutherford House,
Risley
Greg O'CONNOR
+44 (0) 20 7944 5167 Greg.O'Connor@dft.gsi.gov.uk
Criticality and Radiological Protection,
Radioactive Materials Transport Division (RMTD),
Department for Transport (DfT),
2/33, Great Minster House,
76, Marsham Street,
LONDON.
SW1P 4DR
UNITED STATES OF AMERICA
ANDERSON, Richard E.
+1 (505) 667 6912
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Los Alamos National Laboratory
NIS-6, MS J562
P.O. Box 1663
LOS ALAMOS, NM 87545
randerson@lanl.gov
BLOMQUIST, Roger N.
RNBlomquist@anl.gov
Reactor Analysis Division
Argonne National Laboratory
9700 South Cass Avenue (RA-208)
ARGONNE, IL 60439
+1 630-252-8423
BRADY RAAP, Michaele C.
Pacific Northwest National Laboratory (PNNL)
902 Battelle Blvd
P.O. Box 999, MSIN: K8-34
Richland, Washington 99352
+1 (509) 375-3781
michaele.bradyraap@pnl.gov
BRIGGS, J. Blair
Idaho National Engineering
& Environmental Laboratory
P.O. Box 1625, MS-3860
2525 North Fremont
IDAHO FALLS, ID 83415-3860
+1 (208) 526 7628
bbb@inel.gov
DEHART, Mark D.
Building 6011, MS 6370
Oak Ridge National Laboratory
Post Office Box 2008
Oak Ridge, TN 37831-6370
+1 (865) 576 3468
dehartmd@ornl.gov
FUJITA, Edward K.
Reactor Analysis & Engineering Division
Argonne National Laboratory
9700 South Cass Avenue, Bldg. 208
ARGONNE, IL 60439-4842
+1 630 252 4866
ekfujita@anl.gov
HOPPER, Calvin M.
Oak Ridge National Laboratory
Building 6011, MS-6370
1 Bethel Valley Road
Oak Ridge, TN 37831-6370
+1 865 576 8617
HopperCM@ornl.gov
WITHEE, Carl J.
U.S. NRC
Office of Nuclear Material
Safety & Safeguards /SFPO
Mail Stop O-13-D13
WASHINGTON, DC 20555
+1 (301) 415 8534
cjw@nrc.gov
International Organisations
NOURI, Ali
OECD Nuclear Energy Agency
Le Seine St-Germain
12, Boulevard des Iles
92130 Issy-les-Moulineaux
+33 (0)1 45 24 10 84
ali.nouri@oecd.org
SUYAMA, Kenya
OECD/NEA
Le Seine St-Germain
12, Boulevard des Iles
F-92130 Issy-les-Moulineaux
+33 (0) 1 4524 1152
suyama@nea.fr
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