1. Chemical Decontamination during Decommissioning of Nuclear Power Plants
An increasing number of nuclear power plants have reached the stage of decommissioning over recent years. Because worker exposure to radioactive material that has built up on piping and other equipment is a concern during decommissioning, planning for the initial stages of this work includes decontamination to remove this material.
Hitachi developed a decontamination technique that uses hydrazine, oxalic acid, and potassium permanganate (HOP) in 1999. The technique has already been used more than 90 times both in Japan and overseas to reduce worker exposure in operating plants by decontaminating equipment such as external reactor piping that connects to the reactor and is subject to high levels of radiation.
Hitachi has been awarded a contract for chemical decontamination of the inside of the reactor pressure vessel and the reactor internals at Hamaoka Nuclear Power Station Unit 1 of Chubu Electric Power Company, which is currently being decommissioned. Before commencing, fluid dynamics simulation, mockup trials, and other measures were first used to verify that the technique would be able to decontaminate all of the complex reactor internals, in place and simultaneously, while also doing the work without being able to use the existing reactor recirculation pumps, technical challenges not previously faced in Japan. The work was successfully completed, achieving the target level of decontamination.
Hitachi intends to continue to develop this technology in response to customer needs and to deploy it in Japan and overseas.