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For Official Use NEA/NSC/WPNCS/DOC(2015)13 Organisation de Coopération et de Développement Économiques Organisation for Economic Co-operation and Development
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_____________ English - Or. English NUCLEAR ENERGY AGENCY
NUCLEAR SCIENCE COMMITTEE
Working Party on Nuclear Criticality Safety
NINETEENTH MEETING OF THE WORKING PARTY
ON NUCLEAR CRITICALITY SAFETY
SUMMARY RECORD
10 July 2015
NEA Headquarters
Issy-les-Moulineaux, France
Mr Franco Michel-Sendis
franco.michel-sendis@oecd.org
+33 1 45 24 10 99
Complete document available on OLIS in its original format
This document and any map included herein are without prejudice to the status of or sovereignty over any territory, to the delimitation of
international frontiers and boundaries and to the name of any territory, city or area.
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NEA/NSC/WPNCS/DOC(2015)13
2
THE NINETEENTH MEETING OF THE WORKING PARTY
ON NUCLEAR CRITICALITY SAFETY
10 July 2015
NEA Headquarters
12 boulevard des Iles, 92130 Issy-les-Moulineaux, France
SUMMARY RECORD
The Working Party on Nuclear Criticality Safety (WPNCS) was held on July 10, 2015 after five associated
Expert Groups had met during the week of July 6-10, 2015 at NEA Headquarters. The meetings that took
place were:
Monday July 6, morning : The Expert Group on Criticality Excursions Analyses (EGCEA)
Monday, July 6, afternoon : The Expert Group on Used Nuclear Fuel (EGUNF)
Tuesday, July 7: The Expert Group on Advance Monte Carlo Techniques (EGAMCT)
Wednesday, July 8: The Expert Group on Uncertainty Analyses for Criticality Safety Assessments
(EGUACSA)
Thursday, July 9: The Expert Group on Assay Data of Spent Nuclear Fuel (EGADSNF)
1. Introduction & Welcome
The WPNCS Chair, Ms. Michaele Brady-Raap (USA) presided over the meeting.
Brady-Raap opened the meeting and welcomed the participants who briefly introduced themselves. 21
delegates representing 13 countries attended the meeting (see participants list in Annex A). All EG Chairs
were present.
2. Review of actions from previous meeting
There were no outstanding actions to review.
3. Approval of the summary record and agenda
The summary record of the past meeting was approved with inclusion of past country reports that had not
been submitted.
The agenda (Annex B) was approved with modifications in the order of agenda items as proposed by the
Chair.
4. Feedback from Nuclear Science Committee
F. Michel-Sendis, on behalf of J. Gulliford, gave brief highlights of the NSC meeting of June 10-11 2015
relevant to the WPNCS. These highlights include:
The approval of the new EGUNF mandate for 2015-2017;
NEA/NSC/WPNCS/DOC(2015)13
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The approved change in structure of NEA divisions, with the Data Bank becoming an
independent division from the Nuclear Science Committee.;
The now confirmed change of office facilities for the NEA to take place in December 2015
to a new facility in Boulogne-Billancourt;
5. Nuclear Criticality Safety National Programmes
Before the meeting, delegates are kindly requested to submit a written country report providing an
overview of criticality safety related programmes or issues to report from their home countries. National
Activities Reports at Working Party meetings aim to:
Provide convenient formats for disseminating information on national programmes/
incidents/policies.
Identify items of common interest for consideration by WPNCS as potential collaborative
activities within NSC programmes of work.
Highlight significant changes in national programmes at subsequent meetings.
Help NEA identify items of common/special interest.
The reports are received in written form and are included in Annex A.
ICNC-2019
To be highlighted is the consensus given by the committee, during the French National Report, to accept
the formal proposal by France to organise the next ICNC international conference in 2019, probably in
Paris. The last ICNC held in France was in Versailles, 1999, this corresponds therefore to the regularly
observed rotation of ICNC country hosts.
6. Reports from the WPNCS Expert Groups
Individual progress of all the WPNCS Expert Groups was presented by their respective Chairs and is
summarised below.
All Expert Groups (EGAMCT, EGADNSF, EGUACSA, EGCEA) that had their mandate coming to an end
in June 2015 had their mandate extended without revision of the scope, pending the finalisation of ongoing
deliverables.
Individual progress of all the WPNCS Expert Groups is summarised below.
Expert Group on Used Nuclear Fuel (EGUNF)
The EGUNF held its 1st meeting on 7 July 2015. It is currently carrying work on Phase I Benchmark, on
Reflector Effect of SiO2 for direct disposal of used nuclear fuel. The report is expected to be finished in
2016. Potential new activities which have been discussed include:
• Criticality safety during storage – degradation (non-intact fuel);
• Re-criticality problem after SA (Severe Accident);
• Evaluation of Residual Gadolinium in UO2-Gd2O3 BWR rods;
• Analysis of Assay Data from BWR fuel (focusing on Gadolinium isotopes);
A new benchmark proposal by US members will be prepared before the next meeting.
NEA/NSC/WPNCS/DOC(2015)13
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Expert Group on Assay Data for Spent Nuclear Fuel (EGADSNF)
The EGADSNF held its 8th meeting on 9 July 2015. The capture and verification of publicly available
experimental assay data into SFCOMPO-2.0 continues with support from ORNL and the Data Bank (DB).
After significant changes, the Guidance Report on the Evaluation of Assay Data has undergone another
revision by the Expert Group and has will soon been submitted for publication.
The SFCOMPO-2.0 database more than doubles the amount of assay data sets as compared to the first
version. An internal review process of the data in SFCOMPO application is ongoing, with volunteer
reviewers from the EGADNSF. This review is expected to be completed in 2015. Plans to distribute the
new SFCOMPO through the DB and RSICC when released have been discussed.
During the meeting participants made clear it was a priority to release SFCOMPO-2.0 after sufficient
verification of the data was achieved.
Expert Group on Criticality Excursions (EGCEA)
The Expert Group held its 15th meeting on 6 July 2015. The main items of business covered update on the
status of the report for Phase II which is based on solution experiments at the TRACY facility in Japan.
Results for phase III (long-duration solution criticality event) benchmark are expected to be completed in
2015. A criticality excursion exercise in plutonium nitrate solutions with positive temperature coefficients
is also included.
Miyoshi-san highlighted that all present deliverables could be finalized within 2 years and that upon
delivery of these deliverables (Phase II and III reports, with the plutonium exercises) he would be stepping
down as chairman of the EG, by the 2017 meeting.
He noted that, if no other activities were proposed by participants, the EG should then consider closing
down activities.
Expert Group on Uncertainty analyses for Criticality Safety Assessment (EGUACSA)
The Expert Group held its 9th meeting on 8 July 2015. The EG is focusing on completion of two
benchmarks:
Phase IV Benchmark, on the establishment of correlations in experimental uncertainties is
ongoing with a revision of the specifications aimed at reducing the scope of the requested
calculations.
Phase V blind benchmark on MOX damp powders aimed at providing a realistic test of
consistency of various methods has also been started.
Expert Group on Advanced Monte Carlo Methods (EGAMCT)
Preliminary results of the Phase I benchmark on “Quantifying the Effect of Under-sampling Biases in
Monte Carlo Reaction Rate Tallies” were reviewed. Completion of a first draft report associated to this
benchmark is expected by 2016.
NEA/NSC/WPNCS/DOC(2015)13
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Discussion on the future of WPNCS
Brady-Raap highlighted that the WPNCS Mandate was to be renewed in June 2016. A brief discussion
was held on the future of WPNCS and potential new activitites to be identified, knowing that most of the
EGs are coming to completion of their pending reports and deliverables. This discussion ties to similar
discussions held in previous meetings, where delegates where asked to propose new activities for the
WPNCS that answer today’s real industry issues or needs.
Increase Horizontality of activities, transversality in support of ICSBEP were proposed.
Try to perform follow-up on work done previously by the WPNCS. For example, a question was
raised on how to measure the impact of reports.
Permanent storage, BWR Gd burn-up credit , recriticality in final fuel disposal were potential
topics, identified as today real needs, were mentioned as candidates for future topics to consider
within WPNCS.
This is a discussion to continue during the year to come and ahead of the definition of the 2016-2019
WPNCS Mandate.
Change of WPNCS Chairmanship.
Brady-Raap announced that she would be stepping down as Chair of the WPNCS and retiring. On behalf
of the NEA, Michel-Sendis thanked Brady-Raap for her work, leadership and contributions to the WPNCS,
during more than 25 years of collaboration with the NEA, in particular in the Burn-up Credit criticality
area.
With the approval of all, Mr. Eric Letang from IRSN, France, who had sent apologies for his absence
during that day, was proposed as the next WPNCS chairman. It was agreed that the WPNCS chairmanship
would formally change hands at the end of ICNC-2019, in September 2015, allowing for the present
WPNCS chairman to be the closing ICNC chairman as well.
Any Other Business and Date of Next Meeting
It was proposed to keep the week of July 4-8, 2016 for the next WPNCS meetings, with further details to
be announced in due course.
With no other business to discuss, the meeting was adjourned.
List of Actions
1. Action on all delegates - To confirm with NEA the name of official representatives of each
member country to the WPNCS
2. Action on all delegates - To submit to NEA if not already done the written National Report for
inclusion in the minutes.
NEA/NSC/WPNCS/DOC(2015)13
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ORGANISATION FOR ECONOMIC COOPERATION AND DEVELOPMENT
Nuclear Energy Agency
Nuclear Science Committee
Working Party on Nuclear Criticality Safety
ANNEX A
2015 WPNCS Country Reports on Nuclear Criticality Safety National Programmes
1. Czech Republic
Development of nuclear: after cancellation of tender for Temelin NPP units 3,4
construction the discussions concerning new build are ongoing. This year, the government
approved an update to the State energy policy (former document from 2004). The
document foresees that the nuclear should provide in long term over 50% of electricity
(currently 33%) - new power plants should be put into operation in years 2030-35.
The operation license of Dukovany NPP unit 1 ends this year, utility currently completes
the documentation for license renewal for additional 20 years. Units 2-4 will follow.
New fuel has been licensed for Dukovany NPP (fuel pellet without central hole, reduced
cladding thickness)
1.1. R&D Programmes
UJV has an ongoing project on uncertainties propagation to core calculations. In 2015 we
work on material and mechanical uncertainties (fuel mass, pin diameter etc.), next year we will
continue with the cross section data. We work with HELIOS – ANDREA system, we would
like to use SAMPLER from SCALE package for comparison.
1.2. International Collaborations
UJV Řež joined the project ESSANUF (European Supply of Safe Nuclear Fuel) focused on
licensing alternative nuclear fuel supplies for Russian-designed pressurized water reactors
(VVERs) operating in the EU. The project is lead by Westinghouse.
The benchmark “VVER-1000 Mock-up Physics Experiments Hexagonal Lattices (1.275 cm
Pitch) of Low Enriched U(2.0, 3.0, 3.3 wt.% 235U)O2 Fuel Assemblies in Light Water with
H3BO3” has been approved by Technical Review Group and it is included in IRPhEP
handbook 2015 (LR0-VVER-RESR-002 CRIT“/ NEA/NSC/DOC(2006). The benchmark is
based on measurements done in Research Center Řež, and describes critical experiment of
VVER-1000 Mock-up on LR-0 reactor with six different concentrations of boron acid in
moderator.
1.3. Future Challenges
Licensing process Temelin NPP new fuel type of Russian vendor TVEL: changes in fuel pin
type (pellets without hole, decreased cladding thickness), number of spacer grids will increase.
The fuel is to be loaded in 2018.
NEA/NSC/WPNCS/DOC(2015)13
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2. France
2.1. French Context
• The EPR build-up of the 59th French PWR (GEN-3 1700MWe) is going on at Flamanville plant.
• ASTRID will be the French GEN-4-SFR 600MWe industrial demonstrator, which construction is
planned by 2020. CFV core, axially heterogeneous, allows negative Na void worth. Associated fuel
cycle facilities are under study, such as the AFC fuel fabrication facility and the TCP spent fuel
treatment facility.
• JEFF3.1.1 library is used by CEA, EdF (future ANDROMEDE package) and AREVA (new
ARCADIA package) in Reactor Physics codes and Criticality-Safety code CRISTAL-V2.
• The assessment of the first periodic safety review of UP3 unit (La Hague Reprocessing plant) was
launched by IRSN in 2011 at the request of French Safety Authority and ended in the beginning of
2015.
• The assessment of the periodic review of the Fuel fabrication facility FBFC has been launched in
June of this year and should be completed in 2016.
• The nuclear criticality resolution n° 2014-DC-0462 was issued in October 2014 after many reviews
and consultation of the public. It will be completed by a guide. Main Issues of the Resolution and
the Guide are:
- To clarify the scope of NCS for reactor cores and for Fissile material packages in the
facilities,
- To make the connection with the Defence in depth principle defined in the “Nuclear
facilities” Order of 7 February 2012 setting the general rules relative to nuclear
installations,
- To reaffirm the Double contingency principle (DCP) for criticality safety,
- To lay down the minimum information required in the safety cases for control of criticality
hazards (Criticality control modes and Reference Fissile Medium, Acceptability
criterion, …),
- Reinforced the role of criticality engineers by the regulations,
- To reaffirm the necessity of adequate periodic trainings.
With some exceptions, the NCS resolution is applicable since 1 July 2015.
2.2. R&D Programmes, in particular
• AREVA TN BUC transport cask application (9 actinides + 6 FPs) has been approved by the
German Safety authority (TN® 24 E) and also by French authority (TN
® 17/2): PHYSOR2014.
• Analysis of specific SFCOMPO experiments to extend the French experimental validation of
BUC calculation to BU < 15 GWd/t (C. Riffard, A. Santamarina, ICNC2015).
• Implementation of Burnup Credit in RNR fuels is studied, particularly for Phenix assemblies (C.
Carmouze, ICNC2015).
• The IRPhE evaluation of the ‘separated-FP worth’ experiment in MINERVE is completed (NSE
178, pp562-581, December 2014).
• CRISTAL-V2 new package, based on JEFF3.1.1 library and SHEM-281g for the multigroup
route, will be available at the NEA Databank in the 2nd
half-year 2015. The experimental
validation by CEA and IRSN is summarized in ICNC2015 paper (E. Gagnier, N. Leclaire et
al.). Extension of RIB automated tool (calculation bias and uncertainty) to CRISTAL-V2 is
ongoing and the new release of the MACSENS tool from IRSN allow filtering experiments of
the CRISTAL validation database using the OECD/DICE database and API (see the common
paper about the MACSENS filtering tool at ICNC).
NEA/NSC/WPNCS/DOC(2015)13
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• The IFP method was implemented in a development version of TRIPOLI4. 3D continuous-
energy adjoint fluxes are computed. Reactivity worths are accurately calculated using Exact
Perturbation Theory, and Sensitivity profiles can also be produced (G. Truchet, ICNC2015).
• A paper of the French working group on Burnup Credit has been accepted for publication by
NSE. This paper deals with the work of the Working Group concerning the Burnup Credit of
PWR UOX fuels.
• The IRSN continuous energy Monte Carlo code MORET 5.B.2 will be available soon for OECD
distribution.
• Sensitivities calculation capability was implemented in the next release of the MORET
Continuous Monte Carlo code (5.C.1) (A. Jinaphanh, ICNC 2015).
• Statistical learning algorithm for determination of multi-dimensionnal criticality limit. Practical
tests on mass-geometry control, with support for nuisance fissile density (Caplin, ICNC2015).
Implementation within Promethee workbench.
1. International Collaborations
• Writing and Edition of the final Report of the OECD/BUC-PhaseVIII Benchmark.
• In the framework of CHANDA European programme, a new experiment AMSTRAMGRAM devoted
to nuclear data and burnup credit will start in September 2015 in MINERVE : oscillation of 241
Am and 99
Tc samples, in collaboration with IRMM.
• Contributions to the ORACS (Operational and Regulatory Aspects of Criticality Safety) workshop held
by NEA and hosted in Albuquerque by US NRC and the US DOE
• Participation in the ISO working group on NCS (ISO TC85/SC5/WG8 standards)
• Development of the IRSN/DOE-NCSP collaboration: following NCSP structure, technical exchanges
are based on the five following program elements: Analytical Methods (AM), Information
Preservation and Dissemination (IP&D), Integral Experiments (IE), Nuclear Data (ND) and Training
and Education (T&E)
• IRSN/JAEA collaboration in the frame of the STACY criticality facility modification and fuel debris
experiments with a JAEA staff secondment at IRSN.
1. Future Challenges
• Safety-Criticality of GEN-4 SFR cycle.
• A Criticality Safety Guide, supplementing the Criticality Resolution of the French Safety Authority, is
expected in 2016
• Contribution to the organization of the ICNC’2019 in France
3. Input to/from NEA/NSC Programmes of Work
• Realistic correlations are needed in ICSBEP experiments, particularly for LCT benchmarks.
• One issue raised during the ORACS Workshop is the importance of maintaining a close
relationship between research and assessment in Nuclear criticality safety. NEA could contribute
to this issue.
4. Germany
4.1. National Context
NPP Grafenrheinfeld applied for disconnection from the grid and final shutdown for spring 2015,
following the 2002/2011 phase out decision;
NEA/NSC/WPNCS/DOC(2015)13
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Repository Site Selection Act (“StandAG”) to coordinate the search for a site for heat generating
waste is currently under review of the “commission responsible for preparing the selection
procedure” (“repository committee”);
“Federal Office for the Regulation of Nuclear Waste Management” commenced operation
September 1, 2014;
Graphite fuel elements from AVR high temperature test reactor in interim storage at Research
Center Juelich: Storage has to be ended September 30, 2014; no final decision about repatriation or
transport to central storage facility Ahaus yet;
Licence (1996 IAEA regulation) for BWR SNF transport and storage cask CASTOR® V/52
granted in September 2014;
Recent DIN standard updates/reviews;
DIN 25403-7:1996-08 “Criticality safety in processing and handling fissile materials - Part 7:
Criticality data for low enriched UO2 rod lattices in water” withdrawn in January 2014 (outdated
data);
DIN 25474:2014-06 “Measures of administrative character for conservation of criticality safety in
nuclear facilities excluding reactors”;
DIN 25478:2014-06 “Application of computer codes for the assessment of criticality safety”;
DIN 25712:2007-07 “Criticality safety taking into account the burnup of fuel for transport and
storage of irradiated light water reactor fuel assemblies in casks” currently under review, nearly
completion.
4.2. Code Validation and Development
GRS: Current depletion calculation code KENOREST is now validated against publicly available
PIE data from PWR UO2 for actinide-only burnup credit, using both bounding and statistical
approaches, to distinguish different levels of conservatism. Version is now frozen, no further
development foreseen, probably besides minor bug fixes. New development of modular depletion
calculation code MOTIVE has started, to replace KENOREST in the mid-term, including the new
development of “Ventina” inventory calculation code in cooperation with PSI/Switzerland, for
alternative use within MOTIVE framework.
The statistical analysis tool on technical parameters SUnCISTT now features full burnup credit
calculation chain, including axial burnup profiles. It is currently being extended to BWR burnup
credit analysis, then including axial and horizontal assembly heterogeneities as well as consistent
power, temperature and void profiles.
AREVA: The nuclear data uncertainty analysis code NUDUNA has been extended by routines to
process decay data uncertainties. The NUDUNA/MOCABA procedure for improved predictions of
integral functions of nuclear data has been validated for application in criticality safety analysis.
Next step is to apply NUDUNA/MOCABA to reactor core simulations.
4.3. International Collaborations
Many bilateral and multilateral cooperations, e.g. with PSI/Switzerland, ORNL/US, and others;
also international research project proposals submitted to EURATOM Horizon 2020 Nugenia, e.g.
“ACUOS” (Assessment of Core Uncertainties and Operational Safety Margin, 2016-2020) F, D, E,
NL, SLO, CZ.
4.4. Future Challenges
Criticality safety research for final disposal – site / host rock comparison;
NEA/NSC/WPNCS/DOC(2015)13
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Degraded fuel configurations (destructed assembly structures) under accident (SFP, transport) or
disposal conditions;
Transport licence application (GNS/WTI);
Burnup (gadolinium) credit on BWR fuel;
Quivers for damaged fuel rods (PWR, BWR) to load into T+S casks.
5. Sweden
5.1. National Context
A few years ago Vattenfall submitted plans for a new reactor in Sweden. During the last year it has become
clear that there will be no such reactor. Several older reactors (at the Ringhals and Oskarshamn sites) have
also been identified by their owners to plan shutdown for economic reasons. Maintenance of the older
plants is a heavy burden considering the very low electricity price (almost negative).
5.2. Nuclear criticality safety
The application for a nuclear fuel encapsulation plant (copper canisters) and final disposal solution and site
preparation is under review by the licensing authority. Nuclear crlticality safety control for PWR fuel will
apply burnup credit while that for BWR fuel will rely on burnable absorber credit (unlike previous plans
including burnup credit also for BWR fuel).
5.3. International collaboration in nuclear criticality safety activities
For the first time in the 35 years of OECD/NEA collaboration on nuclear criticality safety, the Swedish
licensing authority has declared that there will be no financial support for participation in OECD/NEA
WPNCS activities.
6. Switzerland (Vasiliev)
6.1. R&D Programmes
R&D on criticality safety and burnup credit aspects specific to the final geological repository is continuing
at PSI in collaboration with NAGRA (Swiss National Technical Competence Centre in the field of deep
geological disposal of radioactive waste). Some results of the on-going studies were presented at the EG
UNF meeting.
At PSI the major current objective in relation to the criticality safety methodology development remains
the establishment of a complete chain of uncertainties propagations through burnup/decay to criticality
calculations. In addition the validation basis for criticality and depletion/decay calculations is being
maintained and occasionally enhanced.
The recent progress includes setting up two methods called MTUQ and NUSS to respectively propagate
the technological and nuclear data related uncertainties in Monte-Carlo (MCNPX2.7.0/MCNP6) criticality
calculations and general-purpose neutron data libraries. An important feature of the PSI methods is that
both types of uncertainties can be propagated in a single set of stochastic calculations with randomly
sampled input technological parameters and nuclear data, thus increasing the calculations’ efficiency and
allowing accurate accounting for eventual non-linear combined effects from different sources of
uncertainties. These new methods are even used to consolidate techniques for uncertainty propagation in
burnup calculations.
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In addition, verification studies with alternative approaches (e.g. using the TMC method involving the
TENDL library and the TALYS code, or using the uncertainty propagation estimates obtained with
sensitivity coefficients computed with MCNP6) complement the PSI developments.
The main tool for routine depletion calculations at PSI is the CASMO-5 code, which is currently used
together with SIMULATE-3 for Swiss reactor operation simulations. A methodology for writing the
CASMO-5 spent fuel composition results into the MCNP(X) models used for criticality calculations is
being developed and verified for the burnup credit related studies. The SHARK-X tool, developed at PSI,
is devoted to the propagation of nuclear data uncertainties in depletion/decay calculations (including that
on fission product yields and decay constants). Furthermore, the tool was extended (SHARK-RMB) for
taking into account the uncertainties associated with the reactor operation and the impact of the
manufacturing tolerances on the reactor operation, as well as on the burnup induced design changes.
For decay calculations, the SERPENT depletion module has been selected at PSI so far as the preferable
option.
Verification and validation studies for all codes constituting the PSI CSE+BUC methodology calculation
sequences are continuously performed and updated using the PSI and Swiss industrial partners PIE
databases and data from experimental programs performed in the past at the PROTEUS research reactor.
The Gas-Cooled Fast Reactor and High Conversion Light Water Reactor experimental programs are
currently reanalyzed with modern calculation tools and cross-sections; uncertainty quantification and
sensitivity analysis methods are applied to assert the interest of these experiments to improve the nuclear
data files.
6.2. International Collaborations
Validation studies for the IRSN VESTA code and also assessment of the results against MCNPX/CINDER
and SERPENT have been done at PSI based on the PIE data available from the LWR-PROTEUS Phase-II
experimental program. PSI is preparing a publication on the performed analyses.
In collaboration with GRS, further developments and verification studies towards the establishment of
nuclear data uncertainty propagation methods are foreseen.
PSI plans to participate in the ICNC-2015 conference in which the recent progress in the national R&D
activities will be presented in details.
PSI is also a regular member of the OECD NEA WPRS, and since recently a new member of the WPEC
and EGMPEBV (Expert Group on Multi-physics Experimental Data, Benchmarks and Validation). Of
relevance to the WPNCS related activities, PSI is an active participant in the WPRS UAM benchmark. PSI
also participates in the EU project NURESAFE and in IAEA TWG‐LWR (Technical Working Group on
Light Water Reactors).
6.3. Future Challenges
The planned gradual reduction of the electricity production by the nuclear sector because of the nuclear
energy phase out will obviously imply a reduction of the industry financial support for scientific researches
and developments, while at the same time the need for research support for reactor aging and operation
safety assessments, decommissioning planning and spent fuel handling / disposal - repository strategies
development will most probably increase. Maintenance of competence in these areas at national level and
despite the market conditions thus looks of highest priority.
NEA/NSC/WPNCS/DOC(2015)13
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6.4. Input to/from NEA/NSC Programs of Work
PSI would be interested to know if the assessment of the calculation uncertainties due to the nuclear data is
of relevance for the ICSBEP project and for the associated DICE DATABASE. If such activity is planned
or seen as relevant by the WPNCS, PSI could contribute to the work by applying the NUSS and TMC
stochastic sampling based methodologies, eventually with additional verifications against alternative
options.
7. Japan(Miyoshi, Suyama, Yamamoto)
7.1. Overview of National Context
Based on new Regulatory Requirements commercial nuclear power reactors, safety reviews of
nuclear power plants and research reactors are ongoing. About 30 commercial nuclear reactors are
applying the safety review for New Regulation Requirement, and 5 commercial reactors obtained
the licenses (in Takahama, Shimane and Sendai Power Station). Reactor No.3 in Sendai Power
Station which had first licensing is schedule to restart operation August 2015.
In reference to the new Regulatory Requirements for research reactors by Nuclear Regulatory
Authority of Japan, safety reviews of research reactors ( HTTR, JMTR, JRR-3 in JAEA, KUR in
Kyoto Univ. and so on) started since October 2014.
Critical assembly KUCA in Kyoto Univ. is also applying the licensing procedure by NRA.
7.2. R & D program
JAEA are designing low-enriched heterogeneous cores moderated by the light water. This is
designed for the modified STACY. The main nuclear characteristics of the cores are evaluated
including the feasibility study of reactivity measurement for small fuel samples. Mockup tests of
safety devices for emergency situation were performed. The licensing procedure of STACY
modification by NRA started in March 2015.
Study on reactivity temperature coefficients of low concentration plutonium nitrate solution for
accident analysis has been carrying out.
7.3. International Collaboration
Information exchange in the nuclear criticality safety field between JAEA and IRSN were
conducted by the contract. (Cooperation of uncertainty analyses of STACY modified core
composed of low enriched UO2 fuel rod array with water moderator)
Participation in ICSBEP by providing the criticality data for low enriched uranyl solution system
continues.
4. Future Challenges
Research on criticality control for fuel debris under the program of Nuclear Regulatory Authority
of Japan.(Critical mass computation, Risk analysis).
Research program concerning the direct disposal of used nuclear fuels (Criticality calculation,
Detail evaluation of long term spent fuel composition).
NEA/NSC/WPNCS/DOC(2015)13
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8. United States
The United States has fissile material operations involving all portions of the nuclear fuel
cycle. Although advanced reactor concepts continue to investigate use of fuel with >5wt%
enrichments, the focus of industrial and government activities is on production and fabrication
of reactor fuel with enrichments <5wt%. Delays in the MOX fuel fabrication plant (caused by
funding and design/construction challenges) have limited the need for attention to criticality
safety issues involving transport or storage of MOX fuel.
After the government decision to terminate further work on the repository site at Yucca
Mountain, both the Department of Energy (DOE) and the Nuclear Regulatory Commission
(NRC) are working to assure the technical information and regulatory framework is in place to
support long-term safe storage and subsequent transport of spent fuel. The NRC has recently
issued their draft of a new “waste confidence rule” which expresses confidence in the safety of
current approaches for long term storage of spent fuel. Also, following the events at
Fukushima Dai-ichi, the NRC staff reviewed spent fuel pool storage risks and recently issued a
draft paper that does not recommend expedited transfer of spent fuel from pools to dry cask
storage. Final repository options and overall storage, transport, and disposal systems are being
studied by DOE to provide the technical information for future decisions regarding the back
end of the fuel cycle.
The DOE, including its autonomous National Nuclear Security Administration (NNSA), and
the NRC each have responsibility for providing regulatory oversight on criticality safety –
DOE for operations within the DOE complex and NRC for industry operations. The American
Nuclear Society (ANS) is the US professional organization that works to develop consensus
standards for criticality safety and organize technical meetings on criticality safety. (The ANS
will be the US organization hosting ICNC2015.) Each of these organizations develops,
sponsors, or supports training classes and workshops to support education and knowledge
exchange in the field of criticality safety. The number of universities offering classes and
degree certificates focused on criticality safety has risen over the last few years.
8.1. R&D Programmes
The DOE and NRC both support research activities in the area of nuclear criticality safety.
The DOE Nuclear Criticality Safety Program (NCSP) has provided a central focus for research
and technology development for over 15 years. The DOE NCSP (see http://ncsp.llnl.gov/) has
five elements: Integral Experiments, Analytical Methods, Nuclear Data, Information
Preservation and Dissemination, and Training and Education. Integral experiments (and
hands-on training classes) are conducted at the Nuclear Criticality Experiments Research
Center (NCERC) and at Sandia National Laboratories (SNL). Experiments at NCERC are
conducted by Los Alamos National Laboratory (LANL) and Lawrence Livermore National
Laboratory (LLNL).
All four critical experiment machines at NCERC (Planet, Godiva, Comet, and Flattop) are
available, and the facility operates as a user facility to help meet national and international
program needs. During the past year, NCERC efforts have largely focused on restart efforts
for Godiva following a uranium uptake event in 2014. Godiva restart is expected by the end
NEA/NSC/WPNCS/DOC(2015)13
14
of the calendar year with resumption of critical experiments using Godiva in 2016. The NCSP
has conducted “hands-on” critical experiment training classes at NCERC during the past year.
Specifically, the NCSP conducted 2-week training classes for NCS practitioners in January
and June 2015. The 2-week classes include one week of classroom training at LANL followed
by one week of hands-on critical experiment training at either SNL or NCERC. In addition,
the NCSP conducted 1-week hands-on critical experiment training classes for managers and
operations professionals who need to understand the fundamentals of criticality safety. A 1-
week manager’s course was conducted at SNL in February 2015, and a 1-week class will be
held in August 2015 at NCERC. During the past year, the NCSP has conducted critical
experiments at SNL using the U(7%)O2 lattice assembly. In addition, a new epi-thermal
critical experiment design is in execution phase at SNL, and the new experiment design is
expected to provide epi-thermal benchmark experiment data to support NCS operations. The
multi-laboratory Critical/Subcritical Experiment Design Team works to assess experiment
needs and assure the experiments are designed and performed to achieve stated technical
objectives. Most of the experiments are evaluated as benchmarks for dissemination as part of
the Information Preservation and Dissemination program element.
NRC continues its support for research focused on use of Burnup Credit in designing
criticality control systems for BWR spent fuel storage casks and transportation packages. The
first phase of research which was focused on BWR peak reactivity was completed by issuing a
NUREG report. The second phase of the research, which is examining beyond peak reactivity,
is currently underway and is planned to be completed in the next year or two. BWR research is
being driven primarily by loss of geometry concerns of storing high burnup fuels and the
planned extension of fuel storage time limits beyond 20 years.
With regard to Analytical Methods, MCNP, SCALE, and COG are key codes used for
criticality safety within the DOE complex and are supported by the NCSP. A key area of
development has been sensitivity/uncertainty methods using continuous energy data. The
multi-laboratory Nuclear Data Advisory Group (NDAG) prioritizes nuclear data
measurements and evaluations supported by the NCSP and coordinates NCSP activities with
the US National Nuclear Data Center to assure inclusion in the Evaluated Nuclear Data Files
(ENDF). Funding to help support processing of ENDF data for the criticality safety codes is
also provided by the NCSP and ENDF/B-VII.1 libraries are available for the key NCS
analyses code packages.
In the Nuclear Data program element, prioritized nuclear data measurements and evaluations
continue to be performed to support NCS operations in the US. During the past year, new
differential measurements have been performed on Ca, Ce, and Fe. Also, substantial progress
has been made to expand the RPI linear accelerator neutron capture measurement capabilities
into the keV range that is important for many nuclei pertinent to criticality safety.
Furthermore, the NCSP has partnered with NNSA Naval Reactors to invest in an accelerator
refurbishment effort at RPI to ensure the US has a differential data measurement capability for
performing needed cross-section measurements. With regard to new cross-section evaluation
work, the NCSP has completed new resonance region evaluations for 63,65
Cu, 56
Fe, 16
O, and 182,183,184,186
W. These new evaluations are undergoing testing and are expected to be available
with the next release of the ENDF data library.
NEA/NSC/WPNCS/DOC(2015)13
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8.2. International Collaborations
The NNSA continues to interact with AWE in the UK and CEA and IRSN in France to
identify and collaborate on nuclear criticality safety issues of mutual interest, such as integral
experiments, computational methods, and improved nuclear data. During the past year, the
collaborations have resulted in personnel from the US performing collaborative work at IRSN,
CEA, and AWE. Likewise personnel from AWE and IRSN have visited the US to perform
collaborative work tasks at NCSP sites. Within the DOE NCSP, ORNL and IRMM collaborate
to perform neutron cross-section measurements in the resonance region to address differential
data needs identified as important to improvement of nuclear criticality safety analyses.
Under OCED/NEA WPEC, US national laboratories are working with other international
partners to the CIELO (Collaborative International Evaluated Library Organization) to
improve nuclear evaluations, many of which support improved evaluations for nuclear
criticality safety. Specifically, the CIELO collaboration has focused efforts on completing new
evaluations for 235
U, 238
U, 239
Pu, 56
Fe, and 16
O.
In addition, the NCSP provides support for the US participation in the ICSBEP. With NCSP
support, new benchmark evaluations have been submitted for inclusion in the next release of
the ICSBEP Handbook. The new evaluations include the first of three pulsed experiments
using the SILENE solution assembly for CAAS benchmark calculations and an evaluation of
the SNL 7uPCX 0.800 cm pitch with variable depth in pure water experiment.
NEA/NSC/WPNCS/DOC(2015)13
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8.3. Future Challenges
Organizations face a continuing challenge to maintain a fully compliant criticality safety
program with qualified personnel experienced in both the principles of criticality safety and
the fissile material operations. In addition, a challenge is related to succession planning for
key staff expertise needed to support NCS. To meet this challenge, the NCSP is continuing to
invest in succession planning for key NCS technology capabilities that include specialists in
integral experiments, nuclear data, and analytical methods.
Holdup residues can contribute significantly to the inventory of nuclear material within
process equipment and, at any time, can represent the largest portion of inventory uncertainty.
As such, these residues can challenge assumptions and limits needed for nuclear criticality
safety. The NNSA has initiated work to establish a safety-related in situ nondestructive assay
(NDA) program to manage and direct research and development (R&D) tasks needed to
improve NDA capabilities for quantifying nuclear material holdup. A mission and vision
document for the NDA technology program is in development and should be published in the
coming year.
8.4. Input to/from NEA NSC Programmes of Work
The U.S. continues to engage in each of the Expert Groups of the Working Party on Nuclear
Criticality Safety. These engagements are sponsored by numerous agencies, but the
DOE/NNSA or NRC are the primary sponsors of the participants and their contributions.
9. UK (O’Connor)
9.1. Government Policies (related to issues discussed)
The UK Government provides central regulation of the UK nuclear industry via its Office of
Nuclear Regulation (ONR), who regulate day-to-day operations, and its various environment
agencies, who regulate waste disposals.
The UK Government also funds the central co-ordination and management of nuclear legacies,
via the Nuclear Decommissioning Authority (NDA) and Radioactive Waste Management
Limited (RWM).
Most of the operations in the rest of the UK industry are now either privatised (e.g. in the case
of civil nuclear fuel manufacture and power stations) or contracted out, to consortia employed
by the NDA to manage former BNFL and UKAEA nuclear sites.
From this background, the UK government owned National Nuclear Laboratory (NNL) is now
beginning to receive some government funding to assist with issues that are (or will be) of
strategic importance to the future of the UK nuclear industry.
In the past, the ONR has also been used to provide funding to allow the UK industry to
participate in activities such as JEFF, ICSPBEP and IRPhE. However, the ONR is no longer
able to fund these activities. Hence continued UK involvement now requires any such
activities to be directly funded by UK industry.
NEA/NSC/WPNCS/DOC(2015)13
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9.2. Industry Requirements (skills capability, training, etc.)
In March 2013, the UK government set out its Nuclear Industrial Strategy allowing a
coordinated approach to the UK’s future nuclear research and development demands. The
Nuclear Innovation Research Advisory Board (NIRAB) and the Nuclear Innovation and
Research Office (NIRO) are now operational although it is too early yet for any impact to be
made.
9.3. R&D Programmes, Code development
RWM have been sponsoring the development of post-closure criticality consequences codes,
to answer “what-if” questions relating to the potential local effects of a criticality excursion on
the multiple engineered barriers that comprise a geological disposal facility. This approach is
required to satisfy UK regulatory requirements; applications for waste disposal permits require
safety cases to show that the risks of criticality accidents have been minimised and any
potential consequences of criticality to be assessed. Much of the work carried out by RWM is
subsequently published via the NDA website (see http://www.nda.gov.uk/publications/).
Commercial code developments are also carried out by the ANSWERS team within AMEC
Foster Wheeler. The details are commercially sensitive and are not reported in detail here.
However, ANSWERS have submitted a number of papers to ICNC 2015 which will provide a
good overview of their latest work.
9.4. Experiments, Facilities, Skills/Staff requirements
There are currently no experimental criticality facilities in the UK. Various UK organisations
may be collaborating with other international organisations but the details are commercially
sensitive and are not reported here.
9.5. International Collaborations
Until recently, UK government funding, via ONR, provided for the participation of
ANSWERS in the ICSBEP, JEFF and IRPhE. As noted above, this funding has now ceased
and UK industry may need to come up with alternative ways for funding future participation in
these activities.
Many UK industrial and governmental organisations are actively involved in the work to
deliver ICNC 2015. According to a recent count, 33 papers from UK authors have been
(provisionally) accepted into the conference programme.
Sellafield Ltd and the NNL are also leading UK work, to propose and develop new ISO
standards for fissile waste management and criticality training for plant operators. These
efforts are being carried out in conjunction with the UK Working Party on Criticality (WPC).
The WPC is a national non-executive body that seeks to bring together UK regulators and
industry to share best practices in criticality safety management.
ANSWERS have recently reported their participation in a number of OECD/NEA expert
group benchmarks, including:
NEA/NSC/WPNCS/DOC(2015)13
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“Expert Group on Advanced Monte Carlo Techniques”, (AMCT), Benchmark on
Quantifying the Effect of Undersampling Biases in Monte Carlo Reaction Rate Tallies.
“Expert Group on Uncertainty Analysis in Criticality Safety Assessment” (UACSA),
Benchmarks II and IV.
“Expert Group on Criticality Excursion Analysis” (CEA), Benchmark II.
EDF Energy have also submitted some benchmark results for the EGUNF benchmark on used
PWR fuel in the presence of SiO2.
A general UK industry view would be that continued participation in ICSBEP (etc.) would be
worthwhile. At the time of writing, it is not clear how this might be funded.
9.6. Future Challenges
Funding for UK activities. The WPC is investigating the availability of UK strategic funding
for important issues.
NEA/NSC/WPNCS/DOC(2015)13
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ANNEX B
ORGANISATION FOR ECONOMIC COOPERATION AND DEVELOPMENT
Nuclear Energy Agency
Nuclear Science Committee
19th
Meeting of the Working Party on Nuclear Criticality Safety (WPNCS)
Proposed Meeting Schedule: 9h00 – 17h00
1. Welcome and administrative items- M. Brady-Raap
2. Review of actions from the previous meetings – Secretariat
3. Approval of the summary records of the previous meeting- All
4. Feedback from the Nuclear Science Committee Meeting- J. Gulliford
5. Reports from the WPNCS Expert Groups and Extension of Mandates
5.1. Advanced Monte Carlo Techniques Expert Group (EGAMCT) – J. Miss
5.2. Assay Data for Spent Nuclear Fuel Expert Group (EGADSNF)- I.Gauld
5.3. Criticality Excursions Analyses Expert Group (EGCEA) – Y. Miyoshi
5.4. Uncertainty Analyses for Criticality Safety Assessment (EGUACSA)- B. Rearden
5.5. Used Nuclear Fuel Criticality (EGUNF) – K. Suyama
5.6. International Criticality Safety Benchmark Evaluation Project (ICSBEP) – J. Bess
6. Discussion : The future of WPNCS, preparing 2016-2019 Mandate.
7. Updates on Nuclear Criticality Safety National Programmes -All
8. Status of WPNCS Chairmanship – NEA Secretariat
9. Any other business - All
10. Date and place of the next meeting - Secretariat
11. Adjourn
NEA/NSC/WPNCS/DOC(2015)13
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ANNEX C
Attendees to the 2015 Working Party on Nuclear Criticality Safety meetings
Friday July 10, 2015
CZECH REPUBLIC
Radim VOCKA Tel: +420 266 172 478
Theoretical Reactor Physics Department Eml: vor@ujv.cz
Nuclear Research Institute Rez plc
Husinec - Rez C.P. 130
250 68 Rez u Prahy
FINLAND
Karin RANTAMÄKI Tel: +358 40 549 3212
VTT Technical Research Centre of Finland Eml: karin.rantamaki@vtt.fi
PO Box 1000
FI 02044 VTT Espoo
FRANCE
Stephane EVO Tel: +33 01 58 35 70 14
IRSN/DSU/SEC Eml: stephane.evo@irsn.fr
Institut de Radioprotection
et de Surete Nucleaire
BP 17
92262 FONTENAY-AUX-ROSES CEDEX
Joachim MISS Tel: +33 1 58 35 89 15
IRSN-PSN-EXP/SNC Eml: joachim.miss@irsn.fr
BP 17
92262 Fontenay aux Roses cedex
Alain SANTAMARINA Tel: +33 4 42 25 70 46
CEA Cadarache Eml: alain.santamarina@cea.fr
DEN/DER/SPRC
Bat. 230
F-13108 ST. Paul-Lez-Durance Cedex
GERMANY
Axel HOEFER Tel: +49 69 2557 31250
AREVA GmbH Eml: axel.hoefer@areva.com
Kaiserleistr.29
D-63067 Offenbach
Maik STUKE Tel: +49 89 32004 486
GRSmbH Eml: maik.stuke@grs.de
Forschungsinstitut
Boltzmannstr. 2
85748 Garching n.Munich
HUNGARY
Gabor HORDOSY Tel: +36 1 392 2222 ext. 3442
Centre for Energy Research, Eml: hordosy.gabor@energia.mta.hu
Hungarian Academy of Sciences
P.O. Box 49
1525 Budapest 114.
NEA/NSC/WPNCS/DOC(2015)13
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ITALY
Kenneth William BURN Tel: +39 051 6098 417
ENEA Eml: kburn@enea.it
Via Martiri di Monte Sole, 4
I-40129 BOLOGNA
JAPAN
Yoshinori MIYOSHI Tel: +81 29 282 6020
Japan Atomic Energy Agency Eml: miyoshi.yoshinori@jaea.go.jp
Shirakata Shirane 2-4, Naka-gun, Ibaraki
319-1195 Tokai-mura
Kenya SUYAMA Tel: +81 29 282 5827
Group Leader, Research Group for Reactor Eml: suyama.kenya@jaea.go.jp
Physics & Standard Nuclear Code System
JAEA
2-4 Shirataka,Tokai-mura
Naka-gun,Ibaraki-ken 319-1195
Toshihisa YAMAMOTO Tel: +81 3 5114 2113
Nuclear Regulation Authority Eml: toshihisa_yamamoto@nsr.go.jp
Roppongi-First Bldg., 9-9 Roppongi 1-chom
106-8450 Minato-ku, Tokyo
RUSSIA
Anatoly A. DUDNIKOV Tel: +7 495 196 73 77
Kurchatov Institute Eml: dudnikov_aa@nrcki.ru
Institute of Nuclear Reactors
Dep. Research of Advanced Reactors
Kurchatov Sq. 1,
123182 Moscow
SLOVAK REPUBLIC
Vladimir CHRAPCIAK Tel: +421 33 599 1312
VUJE Trnava a.s Eml: vladimir.chrapciak@vuje.sk
Okruzna 5
918 64 TRNAVA
SPAIN
Pedro ORTEGO SAIZ Tel: +34 91 6317 807
SEA Ingenieria y Analisis de Blindajes S. Eml: p.ortego@seaingenieria.es
Av. Atenas 75 Locales 106-107
28232 Las Rozas (Madrid)
SWEDEN
Dennis MENNERDAHL Tel: +46 8 756 58 12
E. Mennerdahl Systems Eml: dennis.mennerdahl@ems.se
Starvägen 12
SE-183 57 TÄBY
SWITZERLAND
Alexander VASILIEV Tel: +41 56310 2702
Laboratory for Reactor Physics Eml: alexander.vasiliev@psi.ch
and Systems Behaviour
Paul Scherrer Institut, OHSA/D01
NEA/NSC/WPNCS/DOC(2015)13
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CH 5232 Villigen PSI
UNITED KINGDOM
Gregory O'CONNOR Tel: +44 (0) 207 556 3474
Criticality & Radiological Protection Eml: greg.o'connor@onr.gsi.gov.uk
ONR - RMT
Desk 3, GSW Rose Court,
2 Southwark Bridge
London SE1 9HS
UNITED STATES
John BESS Tel: +1 208 526 4375
Idaho National Laboratory Eml: john.bess@inl.gov
2525 Fremont Avenue
Idaho Falls, ID 83415-3855
Michaele C. BRADY RAAP Tel: +1 509 375 3781
Pacific Northwest National Lab(PNNL) Eml: michaele.bradyraap@pnnl.gov
902 Battelle Blvd
P.O. Box 999, MSIN K8-34
Richland, WA 99352
Ian C. GAULD Tel: +1 (865) 574 5257
ORNL Eml: gauldi@ornl.gov
Bldg. 6011, MS-6370
P.O. Box 2008
Oak Ridge, TN 37831-6170
Meraj RAHIMI Tel: +1 301 492 3338
U.S. NRC/NMSS/SFSD Eml: meraj.rahimi@nrc.gov
Office of Nuclear Material
Safety & Safeguards
6003 Executive Blvd
Rockville, 20854
Bradley T. REARDEN Tel: +1 865 574 6085
Oak Ridge National Laboratory Eml: reardenb@ornl.gov
Radiation Transport and Criticality Group
Nuclear Science and Technology Division
P.O. Box 2008, M.S. 6170
Oak Ridge, TN 37831-6170
OECD Nuclear Energy Agency Data Bank, Issy-les-Moulineaux
Franco MICHEL-SENDIS Tel: +33 (0) 1 45 24 10 99
OECD/NEA Data Bank franco.michel-sendis@oecd.org
12 boulevard des Iles
F-92130 Issy-les-Moulineaux
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