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.

Procedure

The procedure of entombment is a very time extensive process. The simplest of the procedures is entombing the Radioactive waste source at the site itself. The waste is encased in a concrete barrier and is then surrounded by a clay mixture, sand/gravel and then the soil in the area of the site. The use of many layers help reduces and prevent the concern of nuclear leakage. A waste disposal facility in El Cabril Spain uses a multi-concrete barrier concept. The concept includes placing the radioactive waste drums inside concrete boxes and placing those boxes inside a reinforced concrete vault. The Vault is then sealed with a waterproof coating to prevent any hazardous liquid from escaping the drums.

Concerns

Much of the concern using nuclear entombment is the worry of nuclear leakage. Nuclear leakage occurs when there is a slight crack in the cementitious material or the clay for any radiation to seep through. Entombment does not solve the problem for every type of isotope of waste. Many different types of nuclides outlive the lifetime of the materials containing it by a thousand years or more. There are some disagreements among state governments on nuclear entombment, as it does not uphold the polluter pays principle. It is often not possible to make an exact estimate of total decommissioning costs, leaving a certain financial liability for a future generation. It is also difficult to guarantee that the necessary expertise for final decommissioning will be available in due time, or that the decommissioning fund has earned sufficient interest. The main concern for many of the infrastructures being used to entomb the waste, is that the facilities being used to entomb the radioactive waste were built for operations and not for disposal and burial of the waste. Some of the facilities may be too small for nuclear waste to be entombed because of the financial aspect going into all the materials needed to build safe housing for the hazardous material. The only other option in the case of the facility being too small is for the nuclear waste to be transferred to another disposing facility or the facility will have to be reinforced. Many U.S. state governments chose to steer clear of entombment because of its potential hazards of not being properly contained. If any of the nuclear waste were to come in contact with any water source, it has the potential to spread through rivers and lakes into highly populated cities to radioactively contaminate it and anyone who drinks from it.

Benefits

The surveillance cost will be lower than the surveillance cost for SAFSTOR (safe storage) option. For example, Yankee Rowe Nuclear Power Station was finally decommissioned in 1960 at the cost of 39 million with the idea of making it to a safe storage. The cost to surveillance the power plant will add up to 8 million every year. In 2007 The Yankee Nuclear Power Station in Rowe was fully dismantled. The cost for entombment is less than the cost or dismantling which rends it to be more of a financial choice. By using the facility in which the waste came from helps the entombment process cost to be less. The use of entombment requires fewer workers and prevents them from being in major contact with the nuclear waste. In addition to using the same facility to reduces cost, it also reduce public interaction with the project and amount of nuclear radiation emitted from the waste. By disposing the nuclear waste in the same facility it will allow engineers to reinforce the facility to ensure safety for the public and the environment. By using the entombment method nuclear waste will be able to decompose, which will then be allowed to be transferred and the facility will be able to get dismantled.

USNRC (United States Nuclear Regulatory Commission)

The USNRC provides licensing for the entombment process, as well as providing license they research and develop programs to help decommission nuclear power plants. USNRC will continue the development of rule making for entombment. NRC will ask the company that are running power plants to set some money aside while the power plant is being run for future shut down cost. The NRC has decided that in order for nuclear entombment to be a possible, a long-term structure must be created specifically for the encasing of the radioactive waste. If the structures are not correctly built water can seep into them and come out with radioactive waste that can infect the public. The NRC itself imposes acts such as the Nuclear Waste Policy Act of 1982 and the Low-level radioactive waste policy to help regulate state governments on the procedures and precautions needed to dispose of the nuclear waste. The Nuclear Waste Policy of 1982 states that both the federal government's are responsible to provide a permanent disposal facility for high-level radioactive waste and spent nuclear fuel. As well with the Nuclear Waste Policy Act of 1982, which gives states the responsibility to dispose of low-level waste and provides facilities to the states that will be regulated by the NRC or by states who have agreed to follow §274 of the Atomic Energy Act.

Examples

• Lucens, Switzerland - initially entombed in a cavern and later decontaminated.
• Dodewaard, the Netherlands - entombed for 40 years, awaiting final decommissioning. Also referred to as 'safe enclosure'.
• Boiling Nuclear Superheater (BONUS) Reactor Facility, Rincón, Puerto Rico
• Hallam Nuclear Power Facility, Hallam, NE, USA
• Piqua Nuclear Generating Station, Piqua, OH, USA

See also

• Decommissioning
• Nuclear Decommissioning Authority
• SAFSTOR