Critical Configuration and Physics Measurements for Assemblies of U(93.15)O2 Fuel Rods [report]

Margaret Marshall
2013 unpublished
A series of small, compact critical assembly (SCCA) experiments were completed from 1962-1965 at Oak Ridge National Laboratory's (ORNL's) Critical Experiments Facility (CEF) in support of the Medium-Power Reactor Experiments (MPRE) program. In the late 1950s, efforts were made to study "power plants for the production of electrical power in space vehicles." ( a) The MPRE program was a part of those efforts and studied the feasibility of a stainless-steel system, boiling potassium 1 MW(t), or
more » ... sium 1 MW(t), or about 140 kW(e), reactor. The program was carried out in [fiscal years] 1964, 1965, and 1966. A summary of the program's effort was compiled in 1967. a The delayed critical experiments were a mockup of a small, potassium-cooled space power reactor for validation of reactor calculations and reactor physics methods. Initial experiments, performed in November and December of 1962, consisted of a core of unmoderated stainless-steel tubes, each containing 26 UO 2 fuel pellets, surrounded by a graphite reflector. Measurements were performed to determine critical reflector arrangements, fission-rate distributions, and cadmium ratio distributions. Subsequent experiments used beryllium reflectors and also measured the reactivity for various materials placed in the core. "The [assemblies were built] on [a] vertical assembly machine so that the movable part was the core and bottom reflector" (see Reference 1). The experiment studied in this evaluation was the first of the series and had the fuel tubes packed tightly into a 22.87-cm outside diameter (OD) core tank. Two critical configurations were found by varying the amount of graphite reflector (see References 1 and 2). Once the critical configurations had been achieved, various measurements of reactivity, relative axial fission and radial activation of 235 U rates, b,c and cadmium ratios were performed. The cadmium ratio, reactivity, and activation rate measurements performed on the critical configurations are described in Sections 1.3, 1.4, and 1.7, respectively. a A. P. Fraas, "Summary of the MPRE Design and Development Program," ORNL-4048, Oak Ridge National Laboratory (1967). b What was referred to as the fission rates in References 1 and 2 are fissions in a uranium fission counter for the axial measurements and relative activation of 235 U fission foils for the radial measurements (see Section 1.7.1).
doi:10.2172/1129114 fatcat:7yxa7lutzbcnlauenmihcik5fm