Category Archives: Uranium

Plutonium Inventories at Fukushima Dai-ichi Nuclear Power Plant and Mixed Oxide (MOX) Fuel at Unit 3

By Jay T. Cullen

The purpose of this post is to provide estimates of the plutonium (Pu) isotopes present at the Fukushima Dai-ichi nuclear power plant (NPP) at the beginning of the disaster in March 2011. The post is part of an ongoing effort to communicate facts about Fukushima obtained through scientific study of the impact of the meltdowns on the environment. Comments on this site and in other public forums highlight the fact that Unit 3 at the NPP was burning mixed oxide (MOX) fuel at the time of the accident which, because it is enriched in Pu, suggests that these releases are potentially more harmful. Here I report estimates of Pu present in the reactors (Units 1, 2 and 3) and spent fuel pools (Units 1-4) at the site based on burnup calculations. Because fission of low enriched uranium (LEU) fuel produces Pu isotopes during operation there was a significant amount of Pu on site in Units 1-4. During extended operation a MOX fuel burning reactor can produce multiple times the Pu of LEU but this was not so at the time of the Fukushima meltdowns. The amount of additional Pu present due to Unit 3’s MOX fuel is small compared to the other reactor cores and the inventory of the spent fuel pools. The differences between environmental impact of MOX versus LEU reactor core meltdown in this case are small. Estimates of the release of Pu isotopes from Fukushima, based on measurements of air, soil and water suggest 100,000 fold less was broadcast to the environment compared to Chernobyl and 5,000,000 fold lower than releases from nuclear weapons testing in the 20th century. Continue reading Plutonium Inventories at Fukushima Dai-ichi Nuclear Power Plant and Mixed Oxide (MOX) Fuel at Unit 3