The Fukushima nuclear plant's slow recovery offers lessons to the US

http://www.guardian.co.uk/commentisfree/cifamerica/2012/may/07/japan-fukushima-nuclear-power-earthquakes?INTCMP=SRCH

Despite the Japanese PM's optimistic assessment of Fukushima, experts have new worries about the plant's recovery
Richard Schiffman
guardian.co.uk, Monday 7 May 2012 17.16 EDT

"A report released in February by the Independent Investigation Commission on the nuclear accident called this pool "the weakest link" at Fukushima. Robert Alvarez, former senior policy adviser at the US department of energy said: "If an earthquake or other event were to cause this pool to drain it could result in a catastrophic radiological fire involving nearly 10 times the amount of Cs-137 released by the Chernobyl accident.

How likely is this? While the structure of Reactor 4 is stable for the moment, the Dai-ichi plant lies miles from a big earthquake fault – as large as the one that caused last year's quake, but much closer to Fukushima. According to a study published in February (pdf) in the European Geosciences Union's journal Solid Earth, that fault is now overdue for a quake.

Whether or not the critical pool at Reactor 4 would survive another major quake intact, Edwin Lyman, a physicist with the Union of Concerned Scientists, told me in a phone interview that a failure of the jury-rigged inadequate piping installed after the disaster could knock the cooling system out of commission."


Except it's worse than that. If the structure fails, the rods in Reactor 4 storage pool are dangerously close to rods from the common spent rod pool, so could potentially include them in the radiological fire. And the entire site has over 11,000 rods that could be brought into play.



http://akiomatsumura.com/2012/04/682.html
Fukushima Daiichi Site: Cesium-137 is 85 times greater than at Chernobyl Accident

"Ambassador Murata strongly stated that if the crippled building of reactor unit 4—with 1,535 fuel assemblies in the spent fuel pool 100 feet (30 meters) above the ground—collapses, not only will it cause a shutdown of all six reactors but will also affect the common spent fuel pool containing 6,375 fuel assemblies, located some 50 meters from reactor 4. In both cases the radioactive assemblies are not protected by a containment vessel; dangerously, they are open to the air. This would certainly cause a global catastrophe like we have never before experienced."

"....assuming a total of 11,138 spent fuel assemblies are being stored at the Dai-Ichi site, nearly all, which is in pools. They contain roughly 336 million curies (~1.2 E+19 Bq) of long-lived radioactivity. About 134 million curies is Cesium-137 — roughly 85 times the amount of Cs-137 released at the Chernobyl accident as estimated by the U.S. National Council on Radiation Protection (NCRP). The total spent reactor fuel inventory at the Fukushima-Daichi site contains nearly half of the total amount of Cs-137 estimated by the NCRP to have been released by all atmospheric nuclear weapons testing, Chernobyl, and world-wide reprocessing plants (~270 million curies or ~9.9 E+18 Becquerel)."