17 March 2011

Yokota Air Base, Japan - U.S. Air Force Airmen and members of the Japan Ground Self-Defense force load high-capacity pumps provided by the U.S. Navy onto a truck.

Photo credit: U.S. Air Force photo by Airman 1st Class Andrea Salazar/Released

French nuclear agency warns of significant long term contamination, as workers race to cover overheating nuclear fuel with water before the wind shifts.

Our fears of the radioactive releases being very significant have been supported by the French radiation safety agency's (IRSN) recent statements. They estimate that the radioactive releases so far are around a tenth of what was released at Chernobyl. Per unit of radioactivity, the releases from Fukushima are capable of causing more contamination, due to their much large share of long lived radionuclides, such as Cesium-137, which has a half-life of about 30 years.

Media, with its focus on action and explosions, is paying less attention to the radioactive releases from overheating and failing nuclear fuel rods, which will continue at least until the rods are fully submerged.

If IRSN's estimates are correct, only favorable wind directions have spared Japan from more widespread contamination. This might change as winds are expected to turn inland for at least some hours during Sunday, and possibly towards Tokyo Monday through Tuesday. This puts an immensely demanding deadline on bringing the radioactive releases, in particular from fuel pools in units 3 under control

Cooling efforts

In order to try and restore water levels in the spent fuel pool, and prevent drastically increased radiation releases and fires, enormous amounts of water are being sprayed onto the spent fuel pools. Some 60 tons of water was sprayed into building 3 around 0100am in a 20 minute operation by fire trucks and Tokyo fire department is aiming to spray water on unit 3 continuously for 7 hours. This could well be enough to fully submerge the fuel rods. Spraying was reported by Kyodo to have started at 14:05. Japan’s Defence minister said spraying is also being organized for unit 4 using military trucks. Spraying on unit 4 is more challenging than unit 3, because a lot of the heavily damaged ceiling and wall structures remain over and around the pool.

Also useful

Japan Industrial Atomic Forum updates: http://www.jaif.or.jp/english/index.php

Latest updates via our Twitter stream.

Our Q and A on the Fukushima nuclear crisis (lots of answers).

Main Fukushima nuclear crisis page.