Working Party on Nuclear Criticality Safety
Second Meeting of the Expert Group on
Criticality Excursion Analyses
11 September 2002
NEA Headquarters, Issy-les-Moulineaux, France
Cassiano de Oliveira opened the meeting and welcomed the participants to the second meeting of the Expert Group on Criticality Excursion Analyses. Twenty-five participants from twenty different organisations attended the meeting (see the list of participants in Annex 1).
Approval of the agenda
The agenda was approved without changes.
Yuichi Yamane presented a paper entitled “Evaluation of Criticality Accident Analysis Code – TRACY experiments – Benchmrk Program”. He first presented an overview of the Nuclear Fuel Cycle Safety Engineering Research Facility (NUCEF) in the JAERI site of Tokai-Mura (Japan). The Transient Experiment Critical Facility (TRACY) is an annular cylinder with a central absorber rod. The experiments use a 10% enriched uranyl nitrate solution. The core can be operated in various modes depending on the reactivity insertion method and speed. The reactivity can be inserted by either removing the control rod or by the fuel solution feed into the tank. During the experiment, the power, temperature and pressure are monitored. Yuich Yamane showed a curve of power variation with time during a step reactivity insertion (reactivity ranging between 0.3 $ and 1$). He also showed the configuration of the facility for dosimetry experiments where 9 detectors are displayed at various locations around the core. He also informed the participants that JAERI has recently published a documentation of the whole series of TRACY transient experiments (Reports JAERI-Data/code 2002-005 to 2002-007). Finally, examples of what could later represent a calculation benchmark were discussed.
Mike Westfall asked three questions. The first one was “How is the variation of density with temperature and time monitored?”. Yuich Yamane answered that the density is measured at the initial state and at the end of the experiment. An interpolation with temperature is then performed. The second question concerned the order of magnitude of the total number of fissions per litter. Yuichi Yamane answered that it is about 10e+15 fissions per litter of solution. The last question was whether the temperature reactivity feedback coefficient is measured or calculated. The answer was both.
Pascal Grivot presented a paper entitled “A Selection of SILENE and CRAC Experiments for Criticality Accident Codes Comparison”. He first presented the main features of the SILENE reactor (an annular cylinder with an absorber rod in the center) which has been in operation since 1974. The fuel is a highly enriched (~93 wt%) uranyl nitrate solution with a concentration varying from 71 g/l to 218 g/l. A typical SILENE run was then presented and examples of the pulse, free evolution and steady state modes were discussed. The first mode (quick removal of the control rod) is the standard one for transient experiment purposes. The free evolution mode (slow removal of the control rod, about 1 cm/s) is often used for training purposes and for the testing of criticality alarms. The steady state mode (very slow removal of the control rod, about 1 mm/s) is essentially used for irradiation and dosimetry purposes. Other applications of the SILENE reactor include the irradiation of reactor fuel samples under transient conditions. Pascal Grivot then presented the CRAC program carried out in Valduc between 1967 and 1972. The core is a full cylindrical tank (two diameters were used, namely 30 cm and 80 cm) and the reactivity insertion is made through the addition of solution (a highly enriched uranyl solution with a uranium concentration between 20 g/l and 340 g/l) into the tank. The flow rate varied from 100 to 1800 l/h. The maximum inserted reactivity was 10 $. Typical CRAC results were showed. Finally, Pascal Grivot informed the participants of the publication of a recent IPSN report compiling both programs.
Yuichi Yamane asked Pascal Grivot to comment on heterogeneous experiments. These experiments were made with a two-layer media: a highly concentrated uranyl nitrate above which a nitrate acid is added. The two-phase media is sub-critical. Injecting air under pressure does the mixing of the two phases and triggers the excursion.
Suzumu Mitake presented a paper entitled: “INCTAC: a criticality Accident Analysis Code for Liquid Fuel Systems - Development status in 2002”. The code is composed of several modules for simulation of thermal- and hydro-dynamics, reactor dynamics and the evaluation of important parameters including fission products release. Several TRACY experiments were used for the validation of the code. There seems to be a systematic difference between the calculation results and experiments at the beginning of the transient which might suggest a problem in the determination of the transient start-up. Improvements to the code and to its users’ interface were made in 2002. This includes the development of analytical models for the simulation of radioactive material and fission products transfer from fuel liquid phase to upper gaseous phase.
Discussion of calculation benchmarks based on experimental data
Pascal Grivot and Yuichi Yamane led a discussion on suitable benchmarks for code comparisons. It was suggested to start with simple configurations (the pulse mode seems to be the most appropriate at this stage). Experiments where the boiling of the solution did not occur were believed to be a good staring point. It was however agreed to vary the enrichment and the inserted reactivity. Pascal Grivot and Yuichi Yamane will draft specifications and circulate them for comments. Anderson was asked about the availability of the SHEBA experimental data. He commented that he will investigate the issue and informed that most of the configurations were below prompt critical.
Web-based information resources on criticality excursions
Ali Nouri suggested designing a web site where information is provided on experimental programs, accidents and calculation tools. Participants will be solicited to provide electronic versions of the documentation and to comment on the content of the web site. An item of particular interest concerns the description of available computer codes and of their validation status.
List of actions
Description of the action
Briggs and Nouri
Define a format for benchmark
Collect the material and set-up the web-based information resources on criticality excursions including experimental
programs, criticality accidents and
summaries of computer codes.
Check whether the SHEBA experiments can be used as benchmarks.
Yamane and Grivot
Propose a first set of benchmarks with U solutions varying the enrichment, inserted reactivity…
Calculation of these benchmarks.
Advertise the activity of this group.
ICNC'2003 might be a good opportunity.
Draft a format for an evaluation of accident Experiment
List of participants
MARKOVA, Ludmila +420 (2) 6617 2291
Ustav jaderneho vyzkumu Rez email@example.com
Theoretical Reactor Physics
Nuclear Research Institute
BERGE, Ludovic +33 1 47 65 29 31
EDF - Recherche et Développement, firstname.lastname@example.org
1, av. du Général de Gaulle,
92141 Clamart Cédex,
LAVARENNE, Caroline +33 1 58 35 78 67
F-92265 FONTENAY AUX ROSES CEDEX
Pascal GRIVOT +33 3 8023 4053
Centre de Valduc
GMAL, Bernhard +49 (0)89 32004 494
Gesellschaft fuer Anlagen- und Reaktorsicherheit email@example.com
LIEM, Peng Hong +81 29 270 5000
NAIS Co., Inc. firstname.lastname@example.org
MITAKE, Susumu +81 (3) 4512 2773
Institute of Nuclear Safety
Fuel Cycle Facility Safety Analysis ec.
17-1 Toranomon 3-chome
Minato-ku, TOKYO 105-0001
NAITO, Yoshitaka +81 29 270 5000
NAIS co. inc.
416 Muramatsu, Tokai-mura
Naka-gun, Ibaraki-ken 319-1112
NOMURA, Yasushi +81 (0)29 282 5834
Fuel Cycle Safety Evaluation Lab. email@example.com
YAMANE, Yuichi firstname.lastname@example.org
Criticality Safety Laboratory,
2-4 Shirakata Shirane,
Tokai-mura Naka-gun Ibaraki-ken,
KOREA (REPUBLIC OF)
HWANG, Hae Ryong +82 (42) 868 2214
Radiation Safety Analysis Group email@example.com
Korea Power Engr. Co., Inc.
P.O. Box 148
MENNERDAHL, Dennis +46 (0) 8 756 58 12
E. Mennerdahl Systems firstname.lastname@example.org
S-183 57 TAEBY
GRIMM, Peter +41 (56) 310 2071
Paul Scherrer Institute email@example.com
CH-5232 VILLIGEN PSI
BROOME, Peter E. +44 (0)1925 833 022
British Nuclear Fuels plc firstname.lastname@example.org
R101, Rutherford House
Warrington WA3 6AS
DE OLIVEIRA, Cassiano R.E. +44 (207) 594 9319
Imperial College of Science, email@example.com
Technology and Medicine
T.H. Huxley School
Prince Consort Road
LONDON SW7 2BP
GULLIFORD, Jim +44 1925 83 3450
BNFL plc firstname.lastname@example.org
R101 Rutherford House
Risley WA3 6AS
UNITED STATES OF AMERICA
ANDERSON, Richard E. +1 (505) 667 6912
Los Alamos National Laboratory email@example.com
NIS-6, MS J562
P.O. Box 1663
LOS ALAMOS, NM 87545
BRADY RAAP, Michaele C. +1 (509) 375-3781
Pacific Northwest National Laboratory (PNNL) firstname.lastname@example.org
902 Battelle Blvd
P.O. Box 999, MSIN: K8-34
Richland, Washington 99352
BRIGGS, J. Blair +1 (208) 526 7628
Idaho National Engineering email@example.com
& Environmental Laboratory
P.O. Box 1625, MS-3860
2525 North Fremont
IDAHO FALLS, ID 83415-3860
DEHART, Mark D. +1 (865) 576 3468
Building 6011, MS 6370 firstname.lastname@example.org
Oak Ridge National Laboratory
Post Office Box 2008
Oak Ridge, TN 37831-6370
FUJITA, Edward K. +1 630 252 4866
Reactor Analysis & Engineering Division email@example.com
Argonne National Laboratory
9700 South Cass Avenue, Bldg. 208
ARGONNE, IL 60439-4842
HOPPER, Calvin M. +1 865 576 8617
Oak Ridge National Laboratory HopperCM@ornl.gov
Building 6011, MS-6370
1 Bethel Valley Road
Oak Ridge, TN 37831-6370
WESTFALL, R. Michael +1 (865) 574 5269/80
Oak Ridge National Laboratory firstname.lastname@example.org
Building 6011, MS 6370
P.O. Box 2008
Oak Ridge, TN 37831-6370
WITHEE, Carl J. +1 (301) 415 8534
U.S. NRC email@example.com
Office of Nuclear Material
Safety & Safeguards /SFPO
Mail Stop O-13-D13
WASHINGTON, DC 20555
NOURI, Ali +33 (0)1 45 24 10 84
OECD Nuclear Energy Agency firstname.lastname@example.org
Le Seine St-Germain
12, Boulevard des Iles
SUYAMA, Kenya +33 (0) 1 4524 1152
Le Seine St-Germain
12, Boulevard des Iles