Disposing of the spent nuclear fuel from the nation's commercial nuclear reactors is a highly technical activity as well as a challenging environmental issue. While nuclear power provides a valuable, alternative source of energy and allows utility companies to keep up with ever increasing energy demands, its by-product, used or "spent" nuclear fuel, must be disposed of safely.

The Office of Civilian Radioactive Waste Management within the Department of Energy has the responsibility for planning, constructing, and managing a national system to dispose of spent nuclear fuel. The system has four elements: waste acceptance, storage, transportation, and disposal. A principal component stressed at every level of the program is the importance of containing radioactive material until the radioactivity decreases.

Temporary Storage

Utility companies have been storing spent nuclear fuel safely since the 1950s when nuclear energy was first used. After spent nuclear fuel is removed from a reactor, it is stored at reactor sites most often in specially treated water pools lined with concrete and steel. Water not only cools the spent nuclear fuel but acts as a natural barrier to shield workers from radiation. Although this storage method has been proven safe, it is not intended to be a permanent storage solution.

In some cases, utilities have decided to use dry storage systems. Fuel assemblies are loaded into heavy stainless steel or concrete casks and are stored either upright on a concrete pad or horizontally in concrete bunkers. Like pool storage, dry storage has been proven safe but is not intended to be a permanent solution for waste disposal.

Permanent Disposal

Many possibilities for permanent disposal have been studied in depth. Options included leaving the waste at the reactor site, burying it in the ocean floor, putting it in polar ice sheets, and rocketing it into outer space. Based on a final Environmental Impact Statement prepared in 1980, and recommendations from groups such as the National Academy of Sciences, the U.S. Geological Survey, and several professional scientific organizations, deep underground disposal was chosen as the best option.

In 1982, Congress enacted legislation regarding high-level radioactive waste disposal, called the Nuclear Waste Policy Act. The Act established within the Department of Energy the Office of Civilian Radioactive Waste Management to develop, construct, and operate a system for spent nuclear fuel and high-level radioactive waste disposal. The system will include elements for waste acceptance, storage, transportation, and a permanent geologic repository.

Mined Geologic Disposal System

The repository, or a mined geologic disposal system, will be a system of tunnels built deep beneath the surface, and surface facilities. Many natural barriers will enhance the safety of an underground facility. The characteristics of the rock layers in which spent nuclear fuel could be placed are studied very carefully by teams of geologists. Other teams of scientists study important factors such as the likelihood of volcanic or earthquake activity or the way water moves within the rock.

In an amendment to the Nuclear Waste Policy Act in 1987, Congress directed the Department of Energy to concentrate site characterization studies on one site, Yucca Mountain, Nevada, located about 161 kilometers (100 miles) northwest of Las Vegas. Detailed geologic and hydrologic site characterization studies will continue for many more years. A system of tunnels and underground laboratories is planned to allow scientists access to the level of the proposed repository about 300 meters (1,000 feet) below the surface. This level is still about 240 meters (800 feet) above the region's water table.

The Nuclear Waste Policy Act, as amended, stressed that if at any time Yucca Mountain is found unsuitable, studies will be stopped immediately, the site will be restored, and DOE will report to Congress within six months on a recommended course of action.

In addition to the many natural barriers a repository site will provide, several man-made barriers will enhance protection of the environment from radiation. Within the repository, fuel assemblies are inside sealed canisters surrounded with additional layers of steel, concrete, or other metals. Highly trained engineers and scientists will monitor the repository's condition and radiation levels from a network of surface facilities.

Transporting Spent Nuclear Fuel: Decades Of Success

Spent nuclear fuel and other radioactive materials are moved around the country almost every day. Shipments go to and from research institutions, nuclear power plants, government research facilities and storage facilities. The safety record for spent nuclear fuel transport is excellent. In over three decades, there has not been a single death or injury due to the release of the radioactive contents of the specially designed casks during transportation.

The specialized casks used to ship nuclear waste are the primary transportation safety feature. Each is carefully designed and built to withstand rigorous conditions before it is certified by the Nuclear Regulatory Commission. A cask design must be able to withstand a 9 meter (30-foot) drop onto an unyielding surface, a drop onto a 15 centimeter (6-inch) pin, immersion in water for eight hours, and being engulfed in flame for 30 minutes. NRC certification is to ensure that cask designs will withstand credible transportation accidents.

To complement the technical safety characteristics built into casks, the Department of Energy was directed by the Nuclear Waste Policy Act, as amended, to provide funds for training for affected State, local, and Tribal officials. Training will cover both safe, routine transportation practices and emergency response procedures.