|
About 100 miles northwest of Las Vegas, Nev., on Nellis Air
Force Range,
the U.S. Department of Energy is planning to build
an underground
disposal site for the nation's commercial,
research and defense
spent nuclear fuel and high-level
radioactive waste.
1. DELIVERING
Canisters of nuclear waste, sealed in special casks, are shipped
to the site by truck or train and inspected at the security
gate. The casks containing the spent nuclear fuel or high-level
nuclear waste will be separated and moved into the Carrier
Preparation Building to be sealed in permanent containers.
2. PROCESSING
Shipping casks are removed and the inner tube with the waste is
placed in a steel multilayered storage container. Any last
decontamination and measurement of the cask's internal
temperature is taken before it is welded shut and placed on a
cart for storage in the mountain.
3. SUBMERGING
An automated system sends the storage containers underground to
the tunnel. Two electric locomotives, one on each end of the
waste package transporter, would move the waste package down a
10,000-foot railed ramp into the mountain.
4. STORING
The containers are stored on their sides along several parallel
tunnels deep in the earth. The proposed depth of the dump is
about 1,200 feet below the surface, but still about 800 feet
above the water table in a very hard rock called volcanic tuff.
A titanium drip shield will be placed over the containers before
the repository is closed. The shield protects from falling rocks
and dripping water
5. CONTAINING
Five different types of vessels will be used to permanently
store spent nuclear fuel from commercial power reactors, spent
nuclear fuel owned by the U.S. Department of Energy - including
naval fuel - and canisters of solidified high-level radioactive
waste from prior commercial and defense fuel reprocessing
operations, some of which would contain cans of immobilized
plutonium.
Up to 63,000 metric tons of commercial spent nuclear fuel and
7,000 metric tons of high-level radioactive waste and DOE spent
nuclear fuel will be packed into hundreds of double lined drums
- the outside is made of a corrosion-resistant nickel-based
alloy and the inside is a stainless steel cylinder. The drums -
once loaded with the nuclear material - are filled with helium
gas to prevent oxidation and help dissipate heat, capped on both
ends with two lids and welded shut.
Depending on what kind of nuclear waste is being stored in them,
canisters can vary in length from almost 12 feet to almost 20
feet and vary in diameter from 6 feet to 7 feet. They each can
hold from 84,000 pounds to 159,000 pounds of nuclear waste.
Sources: Department of Energy; Nuclear Energy Institute |