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Title: Benchmark Evaluation of Fuel Effect and Material Worth Measurements for a Beryllium-Reflected Space Reactor Mockup

The critical configuration of the small, compact critical assembly (SCCA) experiments performed at the Oak Ridge Critical Experiments Facility (ORCEF) in 1962-1965 have been evaluated as acceptable benchmark experiments for inclusion in the International Handbook of Evaluated Criticality Safety Benchmark Experiments. The initial intent of these experiments was to support the design of the Medium Power Reactor Experiment (MPRE) program, whose purpose was to study “power plants for the production of electrical power in space vehicles.” The third configuration in this series of experiments was a beryllium-reflected assembly of stainless-steel-clad, highly enriched uranium (HEU)-O2 fuel mockup of a potassium-cooled space power reactor. Reactivity measurements cadmium ratio spectral measurements and fission rate measurements were measured through the core and top reflector. Fuel effect worth measurements and neutron moderating and absorbing material worths were also measured in the assembly fuel region. The cadmium ratios, fission rate, and worth measurements were evaluated for inclusion in the International Handbook of Evaluated Criticality Safety Benchmark Experiments. The fuel tube effect and neutron moderating and absorbing material worth measurements are the focus of this paper. Additionally, a measurement of the worth of potassium filling the core region was performed but has not yet been evaluated Pelletsmore » of 93.15 wt.% enriched uranium dioxide (UO2) were stacked in 30.48 cm tall stainless steel fuel tubes (0.3 cm tall end caps). Each fuel tube had 26 pellets with a total mass of 295.8 g UO2 per tube. 253 tubes were arranged in 1.506-cm triangular lattice. An additional 7-tube cluster critical configuration was also measured but not used for any physics measurements. The core was surrounded on all side by a beryllium reflector. The fuel effect worths were measured by removing fuel tubes at various radius. An accident scenario was also simulated by moving outward twenty fuel rods from the periphery of the core so they were touching the core tank. The change in the system reactivity when the fuel tube(s) were removed/moved compared with the base configuration was the worth of the fuel tubes or accident scenario. The worth of neutron absorbing and moderating materials was measured by inserting material rods into the core at regular intervals or placing lids at the top of the core tank. Stainless steel 347, tungsten, niobium, polyethylene, graphite, boron carbide, aluminum and cadmium rods and/or lid worths were all measured. The change in the system reactivity when a material was inserted into the core is the worth of the material.« less
Authors:
 [1] ;  [2]
  1. Idaho National Lab. (INL), Idaho Falls, ID (United States). Center for Space Nuclear Research
  2. Idaho National Lab. (INL), Idaho Falls, ID (United States)
Publication Date:
OSTI Identifier:
1179380
Report Number(s):
INL/CON--14-33627
TRN: US1500167
DOE Contract Number:
AC07-05ID14517
Resource Type:
Conference
Resource Relation:
Conference: Nuclear and Emerging Technologies for Space 2015, Albuquerque, NM (United States), 22-27 Feb 2015
Research Org:
Idaho National Laboratory (INL), Idaho Falls, ID (United States)
Sponsoring Org:
USDOE Office of Nuclear Energy (NE)
Country of Publication:
United States
Language:
English
Subject:
22 GENERAL STUDIES OF NUCLEAR REACTORS; STAINLESS STEEL-347; HIGHLY ENRICHED URANIUM; SPACE POWER REACTORS; BERYLLIUM; COMPARATIVE EVALUATIONS; OR-CEF REACTOR; URANIUM DIOXIDE; CADMIUM; TUBES; MOCKUP; BENCHMARKS; CONFIGURATION; GRAPHITE; NIOBIUM; POLYETHYLENES; TUNGSTEN; BORON CARBIDES; FISSION; FUEL RODS; ALUMINIUM; REACTIVITY; REACTOR ACCIDENTS; CRITICALITY; NEUTRON REFLECTORS; SPACECRAFT POWER SUPPLIES; FUEL PELLETS; SIMULATION; POTASSIUM COOLED REACTORS; REACTIVITY WORTHS; MODERATORS; CONTROL ROD WORTHS; NEUTRON ABSORBERS NESDPS Office of Nuclear Energy Space and Defense Power Systems; Critical experiment; reactivity measurements; uranium dioxide beryllium reflected