This file includes three abstracts for the same merged paper 7)
BENCHMARK EXPERIMENTS ON THE ROMB FACILITY –
RESULTS AND PROSPECTS
A. Vasiliev
International Center for Environmental Safety of Minatom of Russia, Moscow, Russia
Yu. Sokolov, V. Teryokhin, Yu. Chernukhin,
V. Lyutov, E. Kuropatenko, V. Shmakov
Russian Federal Nuclear Center – VNIITF, Snezhinsk, Russia
The ROMB facility designed in VNIITF in 1981 allows carrying out benchmark experiments
for specifying nuclear data on the neutron spectra from thermal neutrons to 14 MeV. The
ROMB is a nearly gapless cylinder (ρ = 18,75 g/cm3) made from depleted U-238 (70 cm in
diameter, 90 cm height). It consists of rings with 70/40 and 40/20 diameters and discs with 20
cm diameter. There is a set of discs made from different materials (U-235, Pu-239, Pb, Be,
BeO, Fe, Ti, CH2, LiH, LiD, etc). The discs thickness changes from 0,5 to 5 cm. It allows
assembling various heterogeneous critical assemblies that is extremely important for
investigating assemblies with neutron spectra in the area of unresolved resonances). Different
neutron detectors may be located in vertical channels.
A unique feature of the ROMB is a capability to work with FKBM-M critical test bench and
14 MeV neutrons source at the same time. The latter may be inserted to a horizontal channel
and be positioned at an assembly axis.
There were more than 250 critical experiments carried out at the ROMB facility. A part of
them (approx. 50) were described in ICSBEP publications.
But a lot of interesting experiments are waiting to be described. For instance, 6 series of
experiments with 65 assemblies. In 4 series only uranium or plutonium discs were used; in
two series uranium and plutonium discs were placed in the core simultaneously.
For eight breeding systems, besides critical gap alteration, spectral reaction rate
measurements were also carried out for various activation and tracking detectors in different
parts of the assemblies.
These benchmarks are of highly importance for verifying nuclear data, including in the
neutron energy resonance area.
The ROMB may be used for carrying out experiments on investigations in the field of lowenrichment uranium critical systems, as well as anomality of criticality.
The ROMB is suitable for investigation of subcritical accelerator driven systems.
We hope this facility to be actively used in the international collaboration.
VNIITF Critical Assemblies and Features of Their Evaluations.
Authors: A.P.Vasiliev, V.D.Lyutov, Yu.A.Sokolov, V.A.Teryokhin, V.M.Shmakov
Annotation: Historical background. VNIITF participation in ICSBEP. Since 1958 in RFNCVNIITF were investigated characteristics more, than 400 Critical Assemblies. Design features
of VNIITF assemblies: two-dimensionality, axial symmetry. Division of the critical
assemblies into two parts with an empty gap between them. Merits and demerits of these
systems as benchmarks. Critical assemblies built from spherical or cylindrical details.
Influence of technological gaps between contiguous details on critical assembly description
uncertainties.
The fissile materials, reflector and moderator materials.
Candidates for future evaluations: critical assemblies with lead reflector and moderator (for
development of reactors with lead coolant); critical assemblies having much resonance
neutrons (intermediated) in spectra (for data libraries verification in this area difficult for
description).
References:
1. A.P. Vasilyev, V.D. Lyutov, A. I. Orlov, V. D. Perezhogin. Choise of Benchmark
Experiments on Criticality Safety and their Calculational Models for VNIITF Critical
Assemblies. The Fifth International Conference on Nuclear Criticality Safety, Albuquerque,
NM, USA, September 17-21, 1995, pp 13.22-13.26
2. V.A.Teryokhin, J.A.Sokolov, E.P.Magda, J.I.Chernukhin, A.V.Lukin. _ “Criticality
Measurements in RFNC-VNIITF. The Review.“, The News of the Chelyabinsk Centre of
Science, Communicating And Technical Physics, Vol. 4, 2000.
Neutron and Photon Leakage Spectra Measurement from Spherical and Hemispherical
Samples with a Central Neutron Source as a Possible Benchmark Type.
Authors: A.I.Saukov, V.D.Lyutov, E.N.Lipilina, V.M.Shmakov.
Annotation: Necessity to extend benchmark types (gamma-production, significant
inconsistence between calculations and experiments for some materials, ….) A new
benchmark type different from critical assembly is proposed: spherical samples from different
materials with a central neutron source. Source types: DD, DT, fission et al. Neutrons and
photons leakage spectra measurements. Detectors. Pulsed source. Time of Flight method.
Uncertainty analysis. Such measurements have been performed in the USA ( Pulsed Spheres
Program at Livermore), in Russia (VNIITF, authors A.I.Saukov et al.), Japan (Octavian,
Osaka University) and in others countries.
References
1. A. I. Saukov, V. D. Lyutov et al. "Neutron and Photon Leakage from Spherical and
Hemispherical Samples with a Central 14-MeV Source", VANT, series "Nuclear Constants",
1998, issue 2, page 3, Moscow
2. A. I. Saukov, B. I. Sukhanov, A. M. Ryabinin, V. D. Lyutov, and V. M. Shmakov, A. P. Vasilyev.
PHOTON LEAKAGE FROM SPHERICAL AND HEMISPHERICAL SAMPLES WITH A CENTRAL 14MeV NEUTRON SOURCE, sent to NSE, to be printed in October 2002
3. J. Yamamoto, T. Kanaoka, I. Murata, A. Takahashi and K. Sumita Gamma-ray
Energy Spectra Emitted from Spheres with 14 MeV Neutron Source, Department of Nuclear
Engineering, Faculty of Engineering, Osaka University, 2-1 Yamada-oka, Suita, Osaka 565,
Japan, OKTAVIAN, Osaka University, From June, 1987 to September, 1989
4. A. Marchetti UCRL-ID-131461, New Monte Carlo Simulations of the LLNL PulsedSphere Experiments, A. (July 1, 1998).
5. Luisa F. Hansen, Calvin Wong, Ted T. Komoto, Bertram A. Pohl, Eugene Goldberg,
Robert J. Howerton, and Walter M. Webster. Nucl.Sci.Eng.,72,35-51(1979)
6. F. Maekawa, Y. Kasugai, C. Konno, I. Murata, Kokooo, M. Wada, Y. Oyama,
Y. Ikeda and A. Takahashi)
Benchmark Experiment on Vanadium with D-T Neutrons and Validation of Evaluated
Nuclear Data Libraries by Analysis and Experiment, J.Nucl.Sci.Tech.,36(3)242-249(1999),