U.S. Experience with Greater Confinement Borehole Disposal

Security experts are very concerned that a sealed radioactive source (SRS) could be used in a radiological dispersion device to terrorize and disrupt society. The most vulnerable SRSs are the hundreds of thousands of unwanted SRSs that owners must hold indefinitely because there are no disposal facilities. Near-surface facilities are not safe for long-lived wastes and deep geologic repositories will never be available in the majority of the World’s countries. Sandia National Laboratories (Sandia) recently demonstrated intermediate-depth Greater Confinement Disposal (GCD) boreholes sited in thick arid alluvium in the United States safely isolates long-lived radioactive wastes The GCD boreholes were used to dispose of classified, long-lived transuranic wastes that could not be disposed of elsewhere. The GCD boreholes were about 36 m deep; in which the bottom 15 m was used for waste disposal and the upper 21 m was backfilled with native alluvium. In 2002, after an independent peer review, Sandia’s Safety Assessment was accepted – thus demonstrating that intermediate-depth disposal in thick arid alluvium provides geologic isolation similar to that provide by a mined geologic repository, but at a faction of the cost. Utilizing more than a decade of experience with the GCD boreholes, Sandia is assisting the International Atomic Energy Agency (IAEA) in their development of IAEA guidance for disposing of small volumes of unwanted, highly radioactive material. When properly cited and constructed, such intermediate-depth boreholes are conceptually simple, relatively low cost, proven safe, and permanently eliminate the security risk posed by unwanted radioactive materials.