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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

[email protected]

+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

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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;


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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.


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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.


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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.


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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.


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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).


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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;


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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.


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.


Criticality safety research for final disposal – site / host rock comparison;


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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.


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).


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.


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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).


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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


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.


15


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.


16


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.


17

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.


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:

http://www.nda.gov.uk/publications/


18

“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.


Funding for UK activities. The WPC is investigating the availability of UK strategic funding

for important issues.


19

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


20

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: [email protected]

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: [email protected]

PO Box 1000

FI 02044 VTT Espoo

FRANCE

Stephane EVO Tel: +33 01 58 35 70 14

IRSN/DSU/SEC Eml: [email protected]

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: [email protected]

BP 17

92262 Fontenay aux Roses cedex

Alain SANTAMARINA Tel: +33 4 42 25 70 46

CEA Cadarache Eml: [email protected]

DEN/DER/SPRC

Bat. 230

F-13108 ST. Paul-Lez-Durance Cedex

GERMANY

Axel HOEFER Tel: +49 69 2557 31250

AREVA GmbH Eml: [email protected]

Kaiserleistr.29

D-63067 Offenbach

Maik STUKE Tel: +49 89 32004 486

GRSmbH Eml: [email protected]

Forschungsinstitut

Boltzmannstr. 2

85748 Garching n.Munich

HUNGARY

Gabor HORDOSY Tel: +36 1 392 2222 ext. 3442

Centre for Energy Research, Eml: [email protected]

Hungarian Academy of Sciences

P.O. Box 49

1525 Budapest 114.


21

ITALY

Kenneth William BURN Tel: +39 051 6098 417

ENEA Eml: [email protected]

Via Martiri di Monte Sole, 4

I-40129 BOLOGNA

JAPAN

Yoshinori MIYOSHI Tel: +81 29 282 6020

Japan Atomic Energy Agency Eml: [email protected]

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: [email protected]

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: [email protected]

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: [email protected]

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: [email protected]

Okruzna 5

918 64 TRNAVA

SPAIN

Pedro ORTEGO SAIZ Tel: +34 91 6317 807

SEA Ingenieria y Analisis de Blindajes S. Eml: [email protected]

Av. Atenas 75 Locales 106-107

28232 Las Rozas (Madrid)

SWEDEN

Dennis MENNERDAHL Tel: +46 8 756 58 12

E. Mennerdahl Systems Eml: [email protected]

Starvägen 12

SE-183 57 TÄBY

SWITZERLAND

Alexander VASILIEV Tel: +41 56310 2702

Laboratory for Reactor Physics Eml: [email protected]

and Systems Behaviour

Paul Scherrer Institut, OHSA/D01


22

CH 5232 Villigen PSI

UNITED KINGDOM

Gregory O'CONNOR Tel: +44 (0) 207 556 3474

Criticality & Radiological Protection Eml: greg.o'[email protected]

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: [email protected]

2525 Fremont Avenue

Idaho Falls, ID 83415-3855

Michaele C. BRADY RAAP Tel: +1 509 375 3781

Pacific Northwest National Lab(PNNL) Eml: [email protected]

902 Battelle Blvd

P.O. Box 999, MSIN K8-34

Richland, WA 99352

Ian C. GAULD Tel: +1 (865) 574 5257

ORNL Eml: [email protected]

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: [email protected]

Office of Nuclear Material

Safety & Safeguards

6003 Executive Blvd

Rockville, 20854

Bradley T. REARDEN Tel: +1 865 574 6085

Oak Ridge National Laboratory Eml: [email protected]

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 [email protected]

12 boulevard des Iles

F-92130 Issy-les-Moulineaux

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