Polycube oxidation and factors affecting the concentrations of gaseous products
The polycubes stored at the Hanford Plutonium Finishing Plant (PFP) have been identified in a Vulnerability Assessment as material that requires a stabilization process in support of the Defense Nuclear Facility Safety Board Recommendation 94-1. The baseline plan involves a pyrolysis process to separate out the plutonium and uranium oxides before the remaining material is packaged for interim storage, in accordance with the Record of Decision (ROD), issued June 25, 1996, for the Plutonium Finishing Plant Stabilization Final Environmental Impact Statement, DOE/EIS-0244-F. The polycubes were manufactured at Hanford in the 1960s for use in criticality studies to determine the hydrogen-to-fissile atom ratios for neutron moderation. A mixture of plutonium and/or uranium oxides and a polystyrene (vinyl benzene) matrix, cast into the shape of cubes, the polycubes simulated solutions containing high concentrations of fissile materials. The polycubes varied in size, typically 1/2 x 2 x 2 in. up to 2 x 2 x 2 in., and were sealed with a coating of aluminum paint and/or tape (PVC or Shurtape). The estimated 1,600 polycubes (calculated 179,165 grams net weight) stored at PFP were packed in vented food cans with five to eight cubes per can to accommodate gas generation by radiolysis. Some polycube containers are suspected to contain loose material as well, left over from the forming process. With a fairly high {sup 240}Pu content, polycubes present a challenge for handling, as a result of the 7 to 8 R contact dose rate. Significant hazards linked to unstabilized polycubes are associated with the polystyrene matrix, which generates hydrogen gas due to radiolysis. In addition, some cans of polycubes may contain fines. Because of insufficient data, hazards associated with the fines have not been assessed.
- Research Organization:
- Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
- Sponsoring Organization:
- US Department of Energy (US)
- DOE Contract Number:
- AC06-76RL01830
- OSTI ID:
- 754519
- Report Number(s):
- PNNL-13166; R&D Project: 40199; 820201000; TRN: US0301386
- Resource Relation:
- Other Information: Supercedes report DE00754519; PBD: 4 May 2000; PBD: 4 May 2000
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
12 MANAGEMENT OF RADIOACTIVE WASTES, AND NON-RADIOACTIVE WASTES FROM NUCLEAR FACILITIES
29 ENERGY PLANNING
POLICY AND ECONOMY
ALUMINIUM
COATINGS
CONTAINERS
DOSE RATES
ENVIRONMENTAL IMPACT STATEMENTS
FISSILE MATERIALS
OXIDATION
PLUTONIUM
POLYSTYRENE
PYROLYSIS
STABILIZATION
URANIUM OXIDES
WASTE STORAGE