WASTE DISPOSAL
Storage of spent fuel and problem waste
The volume of nuclear waste produced by the nuclear industry is very small compared with other wastes generated. In the OECD some 300 million tones of toxic wastes are produced each year, but conditioned radioactive wastes amount to only 81,000 m3 per year. However; nuclear waste represents a major challenge for all countries. Some countries are storing their waste directly and some after reprocessing which reduce the amount quite a bit.
Uniquely, with NPPs dry cask storage containers, the waste can be disposed directly and retrieved for reprocessing in the future. This will represent a huge advantage for countries that have decided for direct disposal but may reconsider later.
Waste Management for Used Fuel from Nuclear Power Reactors
Country, Policy, Facilities and progress towards final repositories:
Sources:
OECD NEA, 1996, Radioacvtive waste Management in Perspective
IAEA ,1992, Radioactive Waste Management An IAEA Source Book, & IAEA Bulletin 40,1; 1998
OECD NEA 1999, Geological Disposal of Radioactive Waste - review of developments in the last decade.
Dry Cask Storage in the US
In the late 1970s and early 1980s, the need for alternative storage began to grow when pools at many nuclear reactors began to fill up with stored spent fuel. Utilities began looking at options such as dry cask storage for increasing spent fuel storage capacity. See the graph of nuclear fuel storage pool capacity.
Dry cask storage allows spent fuel that has already been cooled in the spent fuel pool for at least one year to be surrounded by inert gas inside a container called a cask. The casks are typically steel cylinders that are either welded or bolted closed. The steel cylinder provides a leak-tight containment of the spent fuel. Each cylinder is surrounded by additional steel, concrete, or other material to provide radiation shielding to workers and members of the public. Some of the cask designs can be used for both storage and transportation. There are various dry storage cask system designs. With some designs, the steel cylinders containing the fuel are placed vertically in a concrete vault; other designs orient the cylinders horizontally. The concrete vaults provide the radiation shielding. Other cask designs orient the steel cylinder vertically on a concrete pad at a dry cask storage site and use both metal and concrete outer cylinders for radiation shielding.
The first dry storage installation was licensed by the NRC in 1986 at the Surry Nuclear Power Plant in Virginia.
Spent fuel is currently stored in dry cask systems at a growing number of power plant sites, and at an interim facility located at the Idaho National Environmental and Engineering Laboratory near Idaho Falls, Idaho. See the map showing the location of existing independent spent fuel storage installations. (vedlagt kap. 10)
Source: Nuclear Regulatory Commission (www.nrc.gov)
US Safety requirements
Each shipping container must be designed to maintain its integrity under normal transportation conditions and during hypothetical accident conditions. The designs must demonstrate protection against radiological release to the environment under the following hypothetical accident conditions:
A 9 meter (30-foot) free fall on to an unyielding surface
A puncture test allowing the container to free-fall 1 meter (40 inches) onto a steel rod 15 centimeters (6 inches) in diameter
A 30-minute, all-engulfing fire at 800 degrees Celsius (1475 degrees Fahrenheit)
An 8-hour immersion under 0.9 meter (3 feet) of water.
Compliance with this sequential series of tests may be demonstrated by computer modeling, scale-model or full-scale tests. An additional hypothetical accident condition is required for spent fuel in which an undamaged package must be subjected to a one-hour immersion under 200 meters (655 feet) of water.