Nuclear entombment

Entombment (also referred to as safe enclosure) 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. Entombment is part of one of three various ways to decommission a nuclear power plant including: dismantling, safe enclosure and entombment. Nuclear entombment is the least used of the three options. The use of nuclear entombment is more practical for larger nuclear power plants that are in need of both long and short term burials. Entombment is used as a case by case basis because of its major commitment with years of surveillance and complexity until the radioactivity is no longer a major concern, permitting decommissioning and ultimate unrestricted release of the property.

The first procedure is to properly shutdown the site and stow any spent fuel/waste. The waste and reactors are often at extremely high temperatures due to the fission reaction that occurs. The waste is often placed in cooling pools filled with treated water where they await to cool to handling temperatures. Once the waste is cool enough it will often be stored in radioactive resistant containers to await being disposed of. The reactors are shutdown using special control rods to deter the fission reaction and allow for the cooling of the reactor and fuel inside. Once cool the fuel is taken out and dealt with like the waste, while the reactor is sealed in order to allow no escape of radioactive particles or gases. Lastly the heating water is then pumped out and put in containers to await proper decontamination; the coolant is also removed and stored for proper disposal. This procedure is often performed by the company that owned the plant, and if the company is unable to then properly qualified contractors are brought in. After this procedure comes the next one which deals with the radioactivity and radioactive waste.

The second procedure is the dismantling of the site. First, the radioactive fuel is removed, some of which can be recycled, basically the old fuel can be refined and put back into another reactor to be used as more fuel. The most dangerous waste, is placed inside a radioactive resistant container for long term storage, these containers are then taken to storage facilities for long term stowage such as Yucca Mountain nuclear waste repository. Then the rest of the site can be decontaminated through means of cleaning. The site is then checked thoroughly for any sign of radiation. Most of the remaining parts of the site can be disposed of normal as they are not contaminated or radioactivity levels have dropped to within the safe limits. This process is often completed using robots. The robots are able to access difficult to reach areas that may contain radioactive elements that would pose a threat to a human worker.

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Wikipedia