A major Columbia Generating Station (CGS) hazard event has been determined to have a Low likelihood of occurrence in Benton County within the five-year planning cycle of this Plan. Therefore, although some hazard characterization information is presented below, no further risk assessment has been performed for this hazard. Additional analyses to further characterize the risks of this hazard and the development of suitable mitigation action items will be conducted in the future based on periodic reviews of this hazard mitigation plan and available resources

Nature of the Hazard

CGS is owned and operated by Energy Northwest on land leased from the U.S. Department of Energy on the Hanford Site, about twelve miles northwest of Richland. CGS is an 1175-megawatt nuclear power plant that began commercial power generation in 1984. CGS is licensed by the Washington State Energy Facility Site Evaluation Council (EFSEC) and regulated by the federal Nuclear Regulatory Commission (NRC).

Historical Events

The accident at Three Mile Island in Pennsylvania in 1979 has been the only major accident at a commercial nuclear power plant in the U.S. A minor mechanical malfunction compounded by operator error damaged the nuclear reactor core and threatened to release radioactive materials into the environment. A serious release of radiation was avoided, although some radiation was detected up to 20 miles from the site.

Characteristics of the Hazard

Radioactive materials are composed of unstable atoms. These unstable atoms give off excess energy until they become stable – the energy emitted is radiation. The process by which an atom changes from an unstable state to a stable state by emitting radiation is called radioactive decay, or radioactivity. Certain types of radiation are harmful to the cells of the body. The longer a body is exposed to radiation, the greater the risk. Radiation cannot be detected by sight, smell, or any other sense. There are three types of radiation of primary concern: alpha, beta, and gamma (e.g. electromagnetic).

• Alpha radiation is produced when a radioactive substance, such as radium, decomposes to produce radon and an alpha particle. Such material is not usually of concern unless ingested. Alpha particles do not travel far in air, and can be stopped relatively easily (e.g. by a piece of paper).

• Beta radiation is a fast-moving electron produced by radioactive decay. It requires approximately 1,000 times more mass to stop than an alpha particle. Water provides a good shield against beta radiation.

• Gamma radiation includes visible light, ultraviolet light, X-rays and gamma rays. The wave lengths of X-rays and gamma rays are much shorter however, and therefore, the energy is much greater. The greater energy increases the likelihood of damage if the energy is absorbed.

All three types of radiation are dangerous, but gamma radiation poses the greatest threat to human life. Alpha radiation is stopped by the outer skin layers and does not usually present an external hazard. However, if contaminated air, food or water enters the body in sufficient quantity, by ingestion, inhalation or through skin abrasions, considerable internal damage can occur. Beta radiation is more penetrating and may cause burns where fallout particles have deposited on the skin. Gamma radiation is capable of penetrating the entire body and causing damage to organs, blood and bones. Large doses of gamma radiation can cause sickness or death, depending on the amount of the dose received and victim susceptibility. Small doses incurred over a long period of time may have no immediate effect, but could cause various forms of illness later in life. Genetic damage in subsequent generations may also result.

Effects of an incident at a facility utilizing radioactive materials could range from no radioactive release to a radioactive release requiring public evacuation within some radius from the source of the release. Accidents at nuclear power plants are not likely to cause the widespread destruction associated with a nuclear weapon. An accident at a nuclear power plant could cause an environmental radiation hazard by releasing radiation into the air. Contamination could affect areas as far as 50 miles from the accident site, impacting Grant County.