Migration paths for Oklo reactor products and applications to the problem of geological storage of nuclear wastes

Conference · Sat Jan 01 04:00:00 EST 1977

OSTI ID:5235644

Cowan, G A

Escape of the products from the Oklo reactor proceeds, first, by escape from the uraninite (UO/sub 2/) grains and, second, by transport out of the gangue. Escape from the grain by fission recoil accounts for prompt deposition in the gangue of 5 to 10 percent of the products. Escape by volume diffusion is very slow. The rate of loss by diffusion was highest during the operating period of the reactor and may have been of the order of 10/sup -6/ fraction/a for the most volatile elements. The least volatile elements have been retained in the grains. Their diffusion rates are less than 5 x 10/sup -10//a. If similar loss rates can be achieved in synthetic uraninite (or thorianite), the overall rate of transport of most reactor products would be sufficiently limited by diffusion to insure that essentially all of the radioactive species would decay in situ. The principal geochemical requirements for a suitable storage site are those that insure the survival of the UO/sub 2/ matrix, particularly that the pH and Eh are similar to the values at Oklo. Previous work has demonstrated wide variations in the rates of transport of Oklo products out of the reactor zones. Quantitative or semiquantitative estimates of these rates can be made for those elements which were retained in significant amounts but the estimates become qualitative for the very mobile elements. On a relative scale the losses are lowest in a group of elements including Zr, Nb, Ru, Pd, Ag, Te, the rare earths, Bi, Th, U, and Pu, and are high in a group including Sr, Mo, Ba, Kr, Xe, Rb, and Cs. Retention of the various reactor products varied from greater than or equal to 90 percent down to approximately 0.01 percent.

• Research Organization: Los Alamos Scientific Lab., N.Mex. (USA)
• DOE Contract Number: W-7405-ENG-36
• OSTI ID: 5235644
• Report Number(s): LA-UR-77-2787; CONF-771222-1
• Country of Publication: United States
• Language: English

Related Subjects

050100* -- Nuclear Fuels-- Reserves
Exploration
& Mining
052002 -- Nuclear Fuels-- Waste Disposal & Storage
11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS
12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE WASTES FROM NUCLEAR FACILITIES
DIFFUSION
ENVIRONMENTAL TRANSPORT
FISSION
FISSION PRODUCTS
ISOTOPES
MANAGEMENT
MASS TRANSFER
MINERALS
NUCLEAR REACTIONS
OKLO PHENOMENON
RADIOACTIVE MATERIALS
RADIOACTIVE MINERALS
RADIOACTIVE WASTE STORAGE
RADIONUCLIDE MIGRATION
RECOILS
STORAGE
UNDERGROUND STORAGE
URANINITES
URANIUM MINERALS
WASTE MANAGEMENT
WASTE STORAGE