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NRC proposes changes to its rules on nuclear materials
In response to Executive Order 14300, “Ordering the Reform of the Nuclear Regulatory Commission,” the NRC is proposing sweeping changes to its rules governing the use of nuclear materials that are widely used in industry, medicine, and research. The changes would amend NRC regulations for the licensing of nuclear byproduct material, some source material, and some special nuclear material.
As published in the May 18 Federal Register, the NRC is seeking public comment on this proposed rule and draft interim guidance until July 2.
Michelle Pitts, Farzad Rahnema
Nuclear Science and Engineering | Volume 140 | Number 3 | March 2002 | Pages 241-266
Technical Paper | doi.org/10.13182/NSE02-A2259
Articles are hosted by Taylor and Francis Online.
The number of spent nuclear fuel assemblies taken from nuclear power plants and to be stored in existing storage pools is increasing. Therefore, there is a need to optimize the storage configurations. The computer codes and cross sections used to analyze proposed storage configurations must be validated through comparison with experimental data. Restrictive values of ksafe, caused by limited data, can prevent optimal storage utilization. As a collaborative effort between Westinghouse Safety Management Solutions, Oak Ridge National Laboratory (ORNL), Georgia Institute of Technology, and the University of Missouri Research Reactor (MURR), more than 120 experiments were performed using four highly enriched MURR fuel assemblies. The 252Cf-source-driven noise analysis technique developed at ORNL was used as the measurement method for these experiments. This method is based on calculating a specific ratio of measured auto-power and cross-power spectral densities. Twenty-two unique configurations from the MURR experimental program were analyzed for benchmarking purposes.These subcritical experiments were described and analyzed in this paper to provide new measurements to increase the amount of data available for benchmarking criticality codes and cross sections for systems that are far from critical (keff < 0.9).All aspects of the experimental apparatus designed for the experiment program are thoroughly described to enable calculational modeling. Measured and calculated results for the 22 configurations of interest are given. Thorough perturbation studies on measurement uncertainties (e.g., fuel spacing and composition) were performed to determine the uncertainty on the ratio and keff values. Inferred keff values ranged from 0.648 ± 0.005 to 0.860 ± 0.006. A simplified benchmark model is described that consists of the four fuel assemblies, four 3He detectors, detector drywells, and the water reflector. For these measurements, the calculated ratio and keff values agreed with the measurement results within the measurement uncertainty. All of the analyzed configurations were considered acceptable for validation of computer codes and cross sections.
