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Nuclear Crisis in Japan: What We Know

The massive earthquake off the northeast coast of Japan has caused a potentially catastrophic situation at one of Japan’s nuclear power plants.  The situation is still evolving, but below is a preliminary assessment based on the facts as experts at the Union of Concerned Scientists currently understand them.

The plant’s owner, Tokyo Electric Power Company (TEPCO), reported that at 2:46 p.m. local time (12:46 a.m. EST) “turbines and reactors of Tokyo Electric Power Company’s Fukushima Daiichi Nuclear Power Station Unit 1 . . . and Units 2 and 3 . . . automatically shut down due to the Miyagiken-oki Earthquake.”

These reactors are three of the six operating reactors at the Fukushima I nuclear facility.  All are boiling water reactors.  Unit 1 has a rated output of 460 megawatts, and Units 2 and 3 each have a rated output of 784 megawatts.

TEPCO went on to state the shutdowns were caused by the loss of off-site power “due to malfunction of one out of two off-site power systems.”  This loss of power triggered emergency diesel generators, which automatically started to provide backup power to the reactors.

However, at 3:41 p.m. local time (1:46 a.m. EST), the emergency diesel generators shut down “due to malfunction, resulting in the complete loss of alternating current for all three units,” according to TEPCO.  The failure of the diesel generators was most likely due to the arrival of the tsunami, which caused flooding in the area.  The earthquake was centered 240 kilometers from Japan, and it would have taken the tsunami approximately an hour to reach the Japanese islands.

This power failure resulted in one of the most serious conditions that can affect a nuclear plant — a “station blackout” — during which off-site power and on-site emergency alternating current (AC) power is lost.  Nuclear plants generally need AC power to operate the motors, valves and instruments that control the systems that provide cooling water to the radioactive core.  If all AC power is lost, the options to cool the core are limited.

The boiling water reactors at Fukushima are protected by a Reactor Core Isolation Cooling (RCIC) system, which can operate without AC power because it is steam-driven and therefore does not require electric pumps.  However, it does require DC power from batteries for its valves and controls to function.

If battery power is depleted before AC power is restored, however, the RCIC will stop supplying water to the core and the water level in the reactor core could drop.  If it drops far enough, the core would overheat and the fuel would become damaged.  Ultimately, a “meltdown” could occur: the core could become so hot that it forms a molten mass that melts through the steel reactor vessel.  This would release a large amount of radioactivity from the vessel into the containment building that surrounds the vessel.

The containment building’s main purpose is to keep radioactivity from being released into the environment.  A meltdown would build up pressure in the containment building.  At this point we do not know if the earthquake damaged the containment building enough to undermine its ability to contain the pressure and allow radioactivity to leak out.

According to technical documents translated by Aileen Mioko Smith of Green Action in Japan, if the coolant level dropped to the top of the active fuel rods in the core, damage to the core would begin about 40 minutes later, and damage to the reactor vessel would occur 90 minutes after that.

Concern about a serious accident is high enough that while TEPCO is trying to restore cooling the government has evacuated a 3-km (2-mile) radius area around the reactor.

Bloomberg News reported that the battery life for the RCIC system is eight hours.  This means that the batteries would have been depleted before 10 a.m. EST today.  It is unclear if this report is accurate, since it suggests that several hours have elapsed without any core cooling.  Bloomberg also reported that Japan had secured six backup batteries and planned to transport them to the site, possibly by military helicopter.  It is unclear how long this operation would take.

There also have been news reports that Fukushima I Unit 2 has lost its core cooling, suggesting its RCIC stopped working, but that the situation “has been stabilized,” although it is not publicly known what the situation is.  TEPCO reportedly plans to release steam from the reactor to reduce the pressure, which had risen 50 percent higher than normal.  This venting will release some radioactivity.

UCS will issue updates as more information becomes available.

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MRZine Editor’s Notes

Update 1

The evacuation area around the Fukushima 1 Nuclear Power Plant has now been expanded to a 10 km radius from the plant.  The Japanese media are reporting that a level of radiation 1,000 times the normal level has been detected at the central control room of its troubled Unit 1 reactor and a level 20 times the normal level near the gates of the plant.

The Fukushima 2 Nuclear Power Plant is also now reportedly in trouble, failing to cool three (Units 1, 2, and 4) out of its four reactors properly.  This plant, too, has been declared to be in “nuclear emergency.”  Japanese officials are now debating whether to evacuate residents of its surrounding area.

Update 2

One thing about the MSM in Japan: I don’t have access to Japan’s TV and print media and can only look at what’s on the Internet, so I can’t be 100% sure, but it appears to me that the J MSM may be instructed by the government not to bring up the subject of the “worst case scenario” which has been clearly raised in English-language and other international media: the meltdown of some or all of the troubled reactor cores at Fukushima 1 and 2.  I searched Google News by both メルトダウン (the transliteration of “meltdown”) and 炉心溶融 (that’s what it’s called in Japanese), and I couldn’t find anything.

Meanwhile, NHK says that 80,000 are now to be evacuated from the areas potentially subject to exposure to radioactive material; that the Ministry of Land, Infrastructure, Transport, and Tourism has chartered so far only 60 buses for that purpose and will have to arrange for many more; and moreover that there are people in the potentially threatened areas for whom refuges have yet to be found by the government, and the government is just telling them to stay indoors until their refuges are ready!

Death to the Japanese ruling class!

Update 3

NHK reports that the venting of pressure from Fukushima 1’s Unit 1 has been interrupted because the degree of radiation around one of the two container vents, which were being manually opened, is too high.  Officials are now “debating what to do”(!).  The container is under great pressure.  Officials are just now getting around to “considering” frequent shift changes to minimize workers’ exposure or employing devices to remote-control the vent.  Officials are still claiming that it’s “safe” if you are more than 10 km away from the plant, according to NHK.

Update 4

Finally the Mainichi mentions the word “meltdown” (炉心溶融) but only to suggest to the reader that the possibility of a meltdown feared in the initial moments of the Fukushima 1 shutdown has now disappeared.

Update 5

12 March 2011, 12:03 (Japan Time): “As of 11:20 AM, a part of the “fuel assembly” of fuel rods is now exposed above water.  The maximum exposure as of now is about 90 cm.  If the fuel rods remain exposed, they will be damaged, releasing radioactivity” (NHK).

Update 6

12 March 2011, 14:00 (Japan Time): “The Nuclear and Industrial Safety Agency (NISA) of the Ministry of Economy and Industry (MITI) has just announced that near Unit 1 of the Fukushima 1 Nuclear Power Plant, a radioactive element called ‘cesium,’ which results from nuclear fission, has been detected, so it believes that a part of the nuclear fuel at the reactor core of Unit 1 has melted down” (NHK).

Update 7

12 March 2011, 13:26 (Japan Time): “[R]egarding the evacuation of residents within the 10 km radius of the Fukushima 1 Nuclear Power Plant, as of 11:30 AM, about 30% of 2,000-2,100 residents of Okuma-machi in Fukushima Province, which is located in the aforementioned danger zone, are yet to be evacuated, based on a report from Okuma-machi.  Futaba-machi has also reported that about 20% of the 2,000 residents in danger are yet to be evacuated.  There is a possibility that some of them have left on their own, without the knowledge of the municipal officials” (NHK).

Update 8

At last Japanese mass media have begun to speak of the possibility of a Chernobyl-style disaster: “福島原発、炉心溶融の可能性” [Fukushima Nuclear Power: Core Meltdown Possible] (Nikkei, 12 Mach 2011).  Too late.  I charge the Japanese government, and the mass media which have obeyed it and minimized the extent of the danger till now, with an intent to commit genocide.


The Union of Concerned Scientists is the leading U.S. science-based nonprofit organization working for a healthy environment and a safer world.  Founded in 1969, UCS is headquartered in Cambridge, Massachusetts, and also has offices in Berkeley, Chicago and Washington, D.C.  Cf. David Biello, “How to Cool a Nuclear Reactor” (Scientific American, 11 March 2011); Jonathan Soble and James Blitz, “Japan Declares Emergency at Quake-hit Reactor” (Financial Times, 11 March 2011).


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