nuclear-news

The standard decommissioning process entails six major steps: 1. Remove spent fuel rods, 2. Remove radioactive materials that have become affixed to reactor pipes and containers, 3. Wait for radiation levels to go down with time, 4. Dismantle reactors and other internal vessels and pipes, 5. Dismantle the reactor buildings, and 6. Make the site into a vacant lot.

“Cleaning,” “waiting,” and “dismantling” are the three key actions in this process. Needless to say, this all needs to be done while simultaneously containing radioactive materials…..

Hitachi Ltd., which manufactures nuclear reactors, says that it “generally takes about 30 years” to decommission a reactor. The Hamaoka Nuclear Power Plant’s No. 1 and No. 2 reactors operated by Chubu Electric Power Co. are also expected to take about 30 years before they are decommissioned.

In the case of the Fukushima No. 1 Nuclear Power Plant, meanwhile, the biggest challenge lies in how to remove the fuel, says Tadashi Inoue, a research advisor at the Central Research Institute of Electric Power Industry (CRIEPI), ……

“But,” Inoue continues, “we must deal with rubble contaminated with radioactive materials that were scattered in the hydrogen blasts and treat the radiation-tainted water being used to cool nuclear fuel before we can go on to fuel removal.”

Currently, the Fukushima plant’s operator, Tokyo Electric Power Co. (TEPCO), is desperately trying to treat the contaminated water. Huge challenges remain with regards to the contaminated rubble, as radiation levels of over 10 sieverts per hour were found near outdoor pipes on the plant grounds just the other day. Exposure to such high levels would mean death for most people.

Each step in the process toward decommissioning is complicated and requires great numbers of people. It’s a race against time because the maximum amount of radiation that workers can be exposed to is 250 millisieverts….

http://mdn.mainichi.jp/mdnnews/news/20110828p2a00m0na002000c.html