Fukushima I: Water Level Falling at #5, Second Fire at #4, #1 has 43% of Fuel Rods Damaged; Japanese Gov’t Raises Permissible Radiation Level;

Image of Fukushima I #4 Reactor Building, from NHK.

At a news conference Wednesday Japanese Time, Tokyo Electric Power Company (Tepco), the company that runs the Fukishima I site, released the photograph at right of the #4 reactor building. IT shows a hole on the fourth floor about 8 meters across.

Which is to say, it doesn’t show anything. The damage to the building, while far from irrelevant, is not the point. Tepco is pulling a CYA again, stalling for time, releasing a photo that doesn’t show anything significant, while the water level has been reported falling at #5 reactor, there’s been a second fire at either #4 reactor or the spent fuel pool there — it’s not clear which — Tepco confirmed that 43% of the fuel rods are damaged in reactor #1, and the Japanese Government raised by 150% the total radiation that workers remaining behind at the plant could legally be exposed to. Those workers are, clearly, at significant risk at this point. I still hope, though I certainly don’t trust, that the claims from American nuclear bloggers that the workers are surely following adequate protection procedures. But if they were, I imagine the number of millisieverts allowed wouldn’t have been more than doubled.

The important questions, of course, are about the containment vessels on all four reactors, and the spent fuel pool at #4. The information on that count coming from Tepco and the Japanese government is still stunningly vague. In that context, releasing this photo is a way to put out information without putting out any information. Thanks, guys.

BBC was reporting there had been “four explosions” total, so I guess I missed one. I thought it had been “three explosions and a fire,” the fire being at he spent fuel pool by reactor #4, not the reactor itself — but then, here’s #4 with a hole blown in the side of the building. Hey, an explosion here, an explosion there; sooner or later you’re talking real damage.

But there’s also been a second fire at the #4 reactor — one that went out on its own — and NHK, as far as I can tell, appears to be reporting a second 8-meter hole in the outer wall. .

Another 8-meter square hole was also confirmed on the outer wall of the building. Both appeared after an explosion early on Tuesday.

An ensuing fire near the 4th floor reportedly later went out on its own.

Flames were also found spewing from the building early Wednesday, but the utility company said they were no longer visible half-an-hour later.


NHK also reported about two hours ago (7 p.m. California time Tuesday night, 3 a.m. Wednesday GMT):

At the quake-stricken Fukushima Daiichi nuclear power plant, it is feared that the fuel rods in two of its reactors are being rapidly damaged as they remain exposed due to the failed injection of coolant.

Tokyo Electric Power has estimated the extent of small holes or cracks in the fuel rods, based on the amount of radioactive material in the coolant.

It says 43 percent of the fuel rods in the No.1 reactor were possibly damaged at 1 PM on Tuesday, but the ratio had increased to 70 percent by 3:25 PM.

At the No.2 reactor, the ratio rose to 33 percent from 14.

In both reactors, the coolant levels are low, exposing the fuel rods. Sea water is being pumped into the reactors to cool them down, but the coolant level remains low, creating the risk of a meltdown.
Damaged fuel rods would leak radioactive material.

The pressure inside the reactors is sinking and Tokyo Electric Power is monitoring the data carefully while continuing to pump more sea water.


Meanwhile, the water is falling at #5 reactor — which had reportedly been stopped before the earthquake, for a routine inspection. However, it is still experiencing significant decay heat, and its coolant levels are falling. Importantly, the fuel rods at #5 are still under water. Here’s NHK:

At the time of the quake, nuclear fuel rods were already in the reactor and workers had to circulate water to cool them down.

But the tsunami damaged a diesel generator for circulating the coolant, allowing the pressure in the reactor to rise.

Workers opened a valve to reduce the pressure.

But the procedure allowed water to evaporate from the valve.

As of 9 PM on Tuesday, the water level was 2 meters above the fuel rods. That was 40 centimeters lower than 5 hours earlier.

The Agency says it can adjust the water levels by using the No.6 reactor’s generator, which wasn’t damaged by the tsunami. Workers are currently pumping water into the No.5 and No.6 reactors.


Meanwhile, the government has lifted the level of radiation that workers can be exposed to. It was apparently previously 100 millisieverts:

The health and labor ministry says that it raised the limit by a factor of 2.5, to 250 millisieverts, in cases of emergency.

The measure was adopted to secure enough time for workers at the power plant to engage in operations such as cooling down of the reactors.

Radiation above 250 millisieverts is said to cause health problems such as a temporary reduction in the number of white blood cells….

…The ministry explains that the measure was necessary to prevent a nuclear disaster. It says the international radiation limit is set at 500 millisieverts. It adds that medical experts have no clear knowledge about whether radiation of 250 millisieverts or lower will cause health damage.

The sievert is a dose-equivalent measurement that attempts to measure the radiation dose to human tissue. It is a measure of actual dose, not dose-per-time.

The sievert is different and considered more biologically significant than the absorbed dose, which is measured in units called grays. The “roentgen equivalent man” is still what tends to be used in the United States, though everyone’s supposed to be switching to sieverts. The rem measures the same thing as the sievert and is what the U.S. used throughout the Cold War, so some people may be more familiar with rems. One sievert is 100 rems; a millisievert is therefore a tenth of a rem.

The lowest clearly-carcinogenic dose is 100 millisieverts. 1000 millisieverts in one hour is enough to cause acute radiation sickness.

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