Long-term criticality safety concerns associated with surplus fissile material disposition

Conference · Sun Dec 31 00:00:00 EST 1995

OSTI ID:182999

Choi, J S ^[1]

---

1. Lawrence Livermore National Lab., CA (United States)

A substantial inventory of surplus fissile material would result from ongoing and planned dismantlement of US and Russian nuclear weapons. This surplus fissile material could be dispositioned by irradiation in nuclear reactors, and the resulting spent MOx fuel would be similar in radiation characteristics to regular LWR spent UO2 fuel. The surplus fissile material could also be immobilized into high-level waste forms, such as borosilicate glass, synroc, or metal-alloy matrix. The MOx spent fuel, or the immobilized waste forms, could then be directly disposed of in a geologic repository. Long-term criticality safety concerns arise because the fissile contents (i.e., Pu-239 and its decay daughter U-235) in these waste forms are higher than in LWR spent UO2 fuel. MOx spent fuel could contain 3 to 4 wt% of reactor-grade plutonium, compared to only 0.9 wt% of plutonium in LWR spent UO2 fuel. At some future time (tens of thousand of years), when the waste forms had deteriorated due to intruding groundwater, the water could mix with the long-lived fissile materials to form into a critical system. If the critical system is self-sustaining, somewhat like the natural-occurring reactor in OKLO, fission products produced could readily be available for dissolution and release out to the accessible environment, adversely affecting public health and safety. This paper will address ongoing activities to evaluate long-term criticality safety concerns associated with disposition of fissile material in a geologic setting. Issues to be addressed include the identification of a worst-case water-intrusion scenario and waste-form geometries which present the most concern for long-term criticality safety; and suggests of technical solutions for such concerns.

• OSTI ID: 182999
• Report Number(s): CONF-950917-; ISBN 0-7918-1219-7; TRN: IM9608%%368
• Resource Relation: Conference: 5. international conference on radioactive waste management and environmental remediation, Berlin (Germany), 3-9 Sep 1995; Other Information: PBD: 1995; Related Information: Is Part Of Fifth international conference on radioactive waste management and environmental remediation -- ICEM `95: Proceedings. Volume 1: Cross-cutting issues and management of high-level waste and spent fuel; Slate, S.; Feizollahi, F.; Creer, J. [eds.]; PB: 900 p.
• Country of Publication: United States
• Language: English

Related Subjects

42 ENGINEERING NOT INCLUDED IN OTHER CATEGORIES
21 NUCLEAR POWER REACTORS AND ASSOCIATED PLANTS
45 MILITARY TECHNOLOGY, WEAPONRY, AND NATIONAL DEFENSE
05 NUCLEAR FUELS
RADIOACTIVE WASTE FACILITIES
CRITICALITY
SAFETY ANALYSIS
SPENT FUELS
RADIOACTIVE WASTE DISPOSAL
MIXED OXIDE FUELS
NUCLEAR WEAPONS DISMANTLEMENT
PLUTONIUM RECYCLE