via Bellona.org / July 3, 2012 /
A collapse of the already tilting reactor No 4 building at the stricken Fukushima Daiichi plant, ¬atop which sits a spent nuclear fuel storage pool containing 1,535 fuel assemblies – including 204 unused ones – would lead to a “significant global impact,”– by far topping last year’s triple meltdown at the plant, a new report says.
According to the report (available here) released by Holpchi CH, a Swiss-based industrial analytics think-tank, even a 10 percent release of the storage pool’s inventory of radioactive cesium and strontium would “represent 3 to 10 times the March 11, 2011 release amounts, substantially increasing risk levels in Japan and marine life.”
“This is an acute example that we will have to live with the threats emanating from Fukushima for years to come,” said Nils Bøhmer, Bellona’s nuclear physicist and general manager.
The spent fuel pool was singled out by Bellona early in the Fukushima crisis as a possible source of catastrophic radiation releases due to water loss, which took a back seat to the chaos of trying to restore cooling water to reactor Nos 1, 2 and 3 with fire trucks, water cannons and seawater dropped from helicopters.
A tsunami following a 9.0 magnitude earthquake devastated primary and back up cooling to Fukushima Daiichi, causing three reactor meltdowns within three days of the March 11, 2011 disaster. All of Fukushima Daiichi’s reactors are currently in cold shutdown.
But water loss or collapse of the structure housing the spent fuel storage pool continues to pose a cataclysmic threat.
If cooling water for the pool is lost, said the report, “a major release of radioactive material could result,” adding that, “Given the large amounts of heat generated by the fuel rods, the temperature would rise quickly. These rods are surrounded by zirconium cladding and at high temperatures, this cladding catalyzes hydrogen production, can generate additional heat and even explode and burn.”