336 ENVIRONMENTALENGINEEIUNGInvestigations for a mined geologic repository began in the United States in 1972
with Project Salt Vault, a study of a mined-out salt mine near Lyons, KS. Salt mines
are still under investigation as HLW repositories; two German sites, at Gorleben and
Asse, are being investigated (or, in the terminology of the nuclear waste industry,
characretized). Granite, frozen clay, and basalt have been investigated as repository
sites in various parts of the world. In the United States, investigations have shifted
to hard rock formations. The U.S. Nuclear Waste Policy Act, as amended in 1987,
mandates that only the volcanic tuff at Yucca Mountain, NV (about 100 miles NNW
of Las Vegas, NV) be characterized, and that no other site be considered unless the
Yucca Mountain is found unsuitable.
The U.S. HLW repository was scheduled to begin receiving waste in 1998 and to
close, sealing the waste permanently and irretrievably, in 2098. Delays in character-
ization have delayed the opening of the repository, which is now projected to occur
in 2010. A temporary storage site for commercial spent fuel, from which the spent
fuel could be retrieved at some future time for placement in a repository, is also being
considered.
Transuranic (TRU) Waste
A salt formation in Southeastern New Mexico, under investigation since 1978 as a
possible radioactive waste repository, began receiving TRU waste during the spring
of 1999. The Waste Isolation Pilot Project (WIPP) was found to be better suited as
a repository for TRU defense waste than for the more thermally stressful HLW. The
WIPP was completed and certified by the U.S. Environmental Protection Agency and
received its first shipment of TRU waste in March 1999. The facility - the only
operating geologic radioactive waste repository in the world - is now receiving about
100 shipments of TRU waste each month.
Low-Level Radioactive WasteUnlike HLW, commercial LLW has been the responsibility of the private sector since- It has been disposed of, without any treatment at all, in shallow burial trenches
about 60 ft long with a floor area of about 25,000 ft2. Three of the existing commercial
sites were shut down between 1975 and 1978 because of leaks of radionuclides into
surface water and drinking water. Three of the original sites remain open today, at
Hanford, WA, Barnwell, SC, and Beatty, NV. The last two of these are nearing capacity
and are due to be closed. An additional commercial site in north-central Utah is now
also receiving waste.
Before 1980 there were no uniform disposal regulations or practices for handling
LLW in fact, there was no regulatory definition of LLW. Passage of the Low-Level
Radioactive Waste Policy Act of 1980 (and its subsequent amendments) and the pro-
mulgation of 10 CFR Part 61 of the U.S. Code of Federal Regulations, the regulations
for shallow land disposal of LLW, have improved both the method of selecting LLW
disposal sites and the environmental safety of LLW handling.