Long-Term Criticality Control in Radioactive Waste Disposal Facilities Using Depleted Uranium

Conference · Sun Sep 07 04:00:00 EDT 1997

OSTI ID:515995

Forsberg, C. W. ^[1]

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1. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

Plant photosynthesis has created a unique planetary-wide geochemistry - an oxidizing atmosphere with oxidizing surface waters on a planetary body with chemically reducing conditions near or at some distance below the surface. Uranium is four orders of magnitude more soluble under chemically oxidizing conditions than it is under chemically reducing conditions. Thus, uranium tends to leach from surface rock and disposal sites, move with groundwater, and concentrate where chemically reducing conditions appear. Earth`s geochemistry concentrates uranium and can separate uranium from all other elements except oxygen, hydrogen (in water), and silicon (silicates, etc). Fissile isotopes include ²³⁵U, ²³³U, and many higher actinides that eventually decay to one of these two uranium isotopes. The potential for nuclear criticality exists if the precipitated uranium from disposal sites has a significant fissile enrichment, mass, and volume. The earth's geochemistry suggests that isotopic dilution of fissile materials in waste with ²³⁸U is a preferred strategy to prevent long-term nuclear criticality in and beyond the boundaries of waste disposal facilities because the ²³⁸U does not separate from the fissile uranium isotopes. Geological, laboratory, and theoretical data indicate that the potential for nuclear criticality can be minimized by diluting fissile materials with-²³⁸U to 1 wt % ²³⁵U equivalent.

• Research Organization: Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
• Sponsoring Organization: USDOE National Nuclear Security Administration (NNSA), Nuclear Criticality Safety Program (NCSP)
• DOE Contract Number: AC05-96OR22464
• OSTI ID: 515995
• Report Number(s): CONF-970926--3; ON: DE97003492
• Country of Publication: United States
• Language: English

Related Subjects

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE WASTES FROM NUCLEAR FACILITIES
CRITICALITY
Depleted Uranium (DU)
Fissile Materials
ISOTOPE DILUTION
Light-Water Reactor (LWR)
Low-Level Waste (LLW)
Nuclear Criticality Safety Program (NCSP)
RADIOACTIVE WASTE DISPOSAL
Spent Nuclear Fuel (SNF)
UNDERGROUND DISPOSAL
URANIUM 238
Ultimately Waste Packages (WPs)