Original URL: http://www.theregister.co.uk/2011/03/16/fukushima_workers_evacuated/

Site-saving workers evacuated from Japanese reactor disaster

If radiation drops, they will return. If not...

By Rik Myslewski

Posted in Science, 16th March 2011 05:07 GMT

Updated The Japanese government has ordered the evacuation of the 50 remaining workers at the Fukushima Daiichi (No. 1) plant, thus bringing at minimum a temporary halt to the efforts to cool the distressed reactors at that increasingly troubled nuclear power plant.

"Chief Cabinet Secretary Yukio Edano said work on dousing reactors with water was disrupted by the need to withdraw," reported New Delhi Television and other news outlets.

NDTV quoted Edano as saying: "So the workers cannot carry out even minimal work at the plant now. Because of the radiation risk, we are on standby." Although the workers have been withdrawn, Edano also said that the radiation levels were now falling "from 1,000 millisieverts on Wednesday morning to 600-800," according to the BBC.

The "standby" status follows a second fire at the plant's No. 4 reactor, which broke out on Wednesday, Japan time. The International Business Times reported that that fire had extinguished itself within a half an hour, but other reports note that it is impossible to tell if the fire is extinguished, due to the inability to get close enough to the radioactive site to effectively inspect it.

If the pool in which reactor No. 4's fuel rods are currently boiling away their protective water can be somehow refilled – perhaps from helicopters, although the roof of the building housing that reactor unfortunately wasn't blown away in previous mishaps, which would have allowed for water drops – there's a good chance that the reactor's fuel rods' ziconium tubes won't burst.

If those tubes are not cooled, however, and do catch fire and burst, they'd release the radioactive materials inside them, which would engender a release of radioactivity "thousands of times higher than the levels currently measured at the site," according to The Washington Post.

At this point in time, there's no way of knowing the pool's condition. If the pool at reactor No. 4 is damaged and leaking, it may be impossible to pour enough cooling water into it to keep the fuel rods covered and cooled.

At reactors Nos. 5 and 6, to make matters worse, the water level is also dropping: the International Atomic Energy Agency reported at 3:55 UTC on Wednesday (11:55pm Tuesday in New York) that the water level in the containment pool in reactor No. 5 was "201 cm above the top of the fuel. This was a 40 cm decrease since 07:00 UTC of 15 March."

In addition, according to the Los Angeles Times, "Japan's Nuclear and Industrial Safety Agency said an estimated 70% of the nuclear fuel rods have been damaged at the No. 1 reactor and 33% at the No. 2 reactor." ®

Update

Reuters now reports that Kyodo News has said that the evacuated workers are being allowed back into Fukushima Daiichi, as radiation levels there have subsided to tolerable amounts. Although we have no reason to doubt the Reuters report, as of 11:30pm Pacific Daylight Time The Reg has as yet been unable to turn up the Kyodo News report upon which it is based.