SUB-LEU-METAL-THERM-001 Subcritical Measurements of Low Enriched Tubular Uranium Metal Fuel Elements Before & After Irradiation
- Hanford Site (HNF), Richland, WA (United States)
With the shutdown of the Hanford PUREX (Plutonium-Uranium Extraction Plant) reprocessing plant in the 1970s, adequate storage capacity for spent Hanford N Reactor fuel elements in the K and N Reactor pools became a concern. To maximize space utilization in the pools, accounting for fuel burnup was considered. Calculations indicated that at typical fuel exposures for N Reactor, the spent-fuel critical mass would be twice the critical mass for green fuel. A decision was reached to test the calculational result with a definitive experiment. If the results proved positive, storage capacity could be increased, and N Reactor operation could be prolonged. An experiment to be conducted in the N Reactor spent-fuel storage pool was designed and assembled and the services of the Battelle Northwest Laboratories (BNWL) (now Pacific Northwest National Laboratory [PNNL]) critical mass laboratory were procured for the measurements. The experiments were performed in April 1975 in the Hanford N Reactor fuel storage pool. The fuel elements were MKIA fuel assemblies, comprising two concentric tubes of low-enriched metallic uranium. Two separate sets of measurements were performed: one with ''green'' (fresh) fuel and one with spent fuel. Both the green and spent fuel, were measured in the same geometry. The spent-fuel MKIA assemblies had an average burnup of 2865 MWd (megawatt days)/t. A constraint was imposed restricting the measurements to a subcritical limit of keff = 0.97. Subcritical count rate data was obtained with pulsed-neutron and approach-to-critical measurements. Ten (10) configurations with green fuel and nine (9) configurations with spent fuel are described and evaluated. Of these, 3 green fuel and 4 spent fuel loading configurations were considered to serve as benchmark models. However, shortcomings in experimental data failed to meet the high standards for a benchmark problem. Nevertheless, the data provided by these subcritical measurements can supply useful information to analysts evaluating spent fuel subcriticality. The original purpose of the subcritical measurements was to validate computer model predictions that spent N Reactor fuel of a particular, typical exposure (2740 MWd/t) had a critical mass equal to twice that of unexposed fuel of the same type. The motivation for performing this work was driven by the need to increase spent fuel storage limits. These subcritical measurements confirmed the computer model predictions.
- Research Organization:
- Hanford Site (HNF), Richland, WA (United States)
- Sponsoring Organization:
- USDOE National Nuclear Security Administration (NNSA), Nuclear Criticality Safety Program (NCSP); USDOE Office of Environmental Management (EM)
- DOE Contract Number:
- DE-AC06-96RL13200
- OSTI ID:
- 882316
- Report Number(s):
- HNF-29648 Rev 0; TRN: US0603282
- Resource Relation:
- Conference: Annual International Criticality Safety Benchmark Evaluation Working Group Meeting Sponsored by National Nuclear Security Administration (NNSA), Rio de Janeiro (Brazil), 15-19 May 2006
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE WASTES FROM NUCLEAR FACILITIES
BENCHMARKS
CRITICAL MASS
CRITICALITY
EVALUATION
FUEL ASSEMBLIES
FUEL ELEMENTS
FUEL STORAGE POOLS
IRRADIATION
N-REACTOR
SAFETY
SECURITY
SPENT FUEL STORAGE
SPENT FUELS
URANIUM
Nuclear Criticality Safety Program (NCSP)
Benchmarks
Critical Mass
Criticality
Evaluation
Fuel Assemblies
Fuel Elements
Fuel Storage Pools
Irradiation
N-Reactor
Safety
Security
Spent Fuel Storage
Spent Fuels
Uranium