For nuclear power plant
A nuclear power plant is a thermal power station in which the heat source is one or more nuclear reactors. As in a conventional thermal power station the heat is used to generate steam which drives a steam turbine connected to a generator which produces electricity.Nuclear power plants are usually...
s governed by the United States Nuclear Regulatory Commission
The Nuclear Regulatory Commission is an independent agency of the United States government that was established by the Energy Reorganization Act of 1974 from the United States Atomic Energy Commission, and was first opened January 19, 1975...
(SAFe STORage) is one of the options for nuclear decommissioning
Nuclear decommissioning is the dismantling of a nuclear power plant and decontamination of the site to a state no longer requiring protection from radiation for the general public...
of a shut down plant. During SAFSTOR the de-fuelled plant is monitored for up to sixty years before complete decontamination and dismantling of the site, to a condition where nuclear licensing is no longer required. During the storage interval, some of the radioactive contaminants of the reactor and power plant will decay, which will reduce the quantity of radioactive material to be removed during the final decontamination phase.
The other options set by the NRC are DECON
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which is immediate dismantling of the plant and remediation of the site, and ENTOMB
Entombment of a nuclear reactor is a method of nuclear decommissioning in which radioactive contaminants are encased in a structurally long-lived material, such as concrete, that will last for a period of time to ensure the remaining radioactivity is no longer of significant concern...
which is the enclosure of contaminated parts of the plant in a permanent layer of concrete. Mixtures of options may be used, for example, immediate removal of steam turbine components and condensors, and SAFSTOR for the more heavily radioactive containment vessel. Since NRC requires decommissioning to be completed within 60 years, ENTOMB is not usually chosen since not all activity will have decayed to an unregulated background level in that time.
Decommissioning options for a retired nuclear plant may be chosen based on availability of decommissioning funds, operation of other reactors at the same site, or availability of waste disposal facilities. In 2004, 11 reactors were planned for DECON and 9 for SAFSTOR. In 2008, 14 shutdown commercial power reactors were planned for or had completed DECON, 11 were in SAFSTOR, 3 were in ENTOMB and Three Mile Island unit 2 was defuelled and will be decontaminated when Unit 1 ceases operation.
Different sub-levels of SAFSTOR are recognized, which vary in the type of activity and monitoring required.
In "hot/cold standby" the plant is kept in operating condition but not actively delivering power; monitoring and maintenance is similar to that during a long outage. This may be the first step to allow planning of further shutdown and decommissioning.
In "custodial SAFSTOR" systems such as radiation monitoring and ventilation are kept in operation, along with continuous site security and maintenance. Minimal initial decontamination is done.
"Passive SAFSTOR" requires a more thorough initial clean up, but allows only intermittent inspection of the site and shutdown of active systems such as radiation monitoring.
"Hardened SAFSTOR" prevents intrusion on contaminated parts of the plant by substantial barriers.
All varieties of SAFSTOR require positive action to decontaminate the site at the end of the storage period.