Decommissioning Nuclear Reactors

Background Before a company decides to close it’s power reactors the facility must be put in to a state that no longer has a residual radioactive level, clean up of all radioactive contaminated systems and structures, and remove the radioactive fuel.

When to decommission? Most nuclear power plants are designed to last for about 30 years. (Newer plants are designed to last for about years.) Companies have been attempting to have longer operating periods in order to help balance the amount of money required to make the plants with the amount of money made while operating. Georgia Tech decided t decommission its research reactor after thirty years because it was only designed to really last that long and because it had begun to cause adverse financial effects.

Georgia Tech’s Research Reactor(GTRR) The GTRR was a 5MW Heavy Water Thermal Reactor licensed in 1964 for only 1MW(converted to 5MW in 1974) Its core contained up to 19 MTR type fuel elements with a biological shield composed of Boral, Steel, Lead, and High Density Concrete

Decommissioning Strategies There are three main strategies to decommission a nuclear facility. DECON (Immediate Dismantling), SAFSTOR (Safe Enclosure), and Entombment. The first, being the fastest, is known as DECON (Decommission). This is the immediate dismantlement of the facility and all parts of said facility are decontaminated to a safe level.

Safe Storage The second type is SAFSTOR, it takes longer than DECON and in this a nuclear facility is monitored until the radioactivity decreases to a level that allows the facility to be dismantled without decontamination requirements Essentially storing the materials until deemed safe enough for removal.

Entombing The final type is ENTOMB. As the word suggests, this is where the structure becomes permanently encased by a material that would prevent the leaking of radioactive materials. Usually involves reducing the size of the area the radioactive material is taking and encasing the entire structure to a degree that it will ensure the radioactivity is longer a concern.

Decommissioning the GTRR In order to dismantle the plant, the fuel must first be removed. The HEU(Highly Enriched Uranium) was removed from the reactor’s core and moved to the Hot Cell Area where the fuel section was removed The fuel was then put into a BMI Cask and the fuel was shipped back to Savannah River

Decommissioning the GTRR (cont.) After the fuel was removed, the heavy water had to be shipped off-site and returned to the DOE Additional piping was added onto existing overflow pumps in order to channel the water into the shipping drums

Decommissioning the GTRR (cont.) After the heavy water was removed, the rest of the reactor was disassembled The radioactive waste was then packaged and disposed of The plant was successfully decommissioned without any off-site contamination The entire process cost 8 million dollars

Final Result? After decommissioning a reactor there should be no danger of a radioactive accident occurring to anyone going anywhere on the property. Essentially the entire site is put under a radioactive ‘clean-up’ and decommissioning is not entirely complete until the plot land is deemed harmless.

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