Japan’s Fukushima: Explosion and fire at reactor #4

Japan’s news agency Kyodo has reported a fire at reactor #4 probably started by a similar hydrogen explosion. Businessweek has stated that Hidehiko Nishiyama, deputy director-general of Japan’s Nuclear and Industrial Safety Agency, said in Tokyo that the building housing #4 has two holes in it; water in the spent fuel pool may be boiling; and that there is the threat water levels will drop and hydrogen will be released. He did not say whether or not more hydrogen could lead to another explosion.

The CBC as of 8:45am EST has reported on a nationally televised statement by Prime Minister Naoto Kan in which he said radiation has spread from the four stricken reactors of the Fukushima Dai-ichi nuclear plant along Japan’s northeastern coast. Officials at the Fukushima plant have stated that due to the fire at reactor #4, radioactivity is being released directly into the atmosphere and authorities have ordered 140,000 to seal themselves indoors.

Yukio Edano, chief cabinet secretary, was quoted as saying, “Now we are talking about levels that can damage human health. These are readings taken near the area where we believe the releases are happening. Far away, the levels should be lower. Please do not go outside. Please stay indoors. Please close windows and make your homes airtight. Don’t turn on ventilators. Please hang your laundry indoors. These are figures that potentially affect health, there is no mistake about that.”

Reuters (8:15am EST) reports that the control room for reactor #4 has such high levels of radiation, that it is no longer safe to work there. Employees are monitoring the situation from a different locale.

Chief Cabinet Secretary Yukio Edano was quoted as saying that levels at the plant were between 100 and 400 millisieverts, that is, 160 times higher than the average dose of radiation a typical person receives from natural sources in a year. The word microsievert refers to a unit measuring radiation dosage. People are typically exposed to a total of about 1,000 microsieverts during an entire year.

A no fly zone has been declared for 30 km around the Fukushima I plant.

Kyodo states that the cores of those three reactors at the plant have probably partially melted.

Kyodo news agency gave the current status of the various reactors:

Fukushima No. 1

— Reactor No. 1 – Cooling failure, partial melting of core, vapor vented, hydrogen explosion, seawater pumped in.

— Reactor No. 2 – Cooling failure, seawater pumped in, fuel rods fully exposed temporarily, damage to containment system, potential meltdown feared.

— Reactor No. 3 – Cooling failure, partial melting of core feared, vapor vented, seawater pumped in, hydrogen explosion, high-level radiation measured nearby.

— Reactor No. 4 – Under maintenance when quake struck, fire caused possibly by hydrogen explosion at pool holding spent fuel rods, pool water levels feared receding.

— Reactor No. 5 – Under maintenance when quake struck.

— Reactor No. 6 – Under maintenance when quake struck.

Fukushima No. 2

— Reactor No. 1 – Cooling failure, then cold shutdown.

— Reactor No. 2 – Cooling failure, then cold shutdown.

— Reactor No. 3 – Cold shutdown.

— Reactor No. 4 – Cooling failure, then cold shutdown.

Fukushima I Nuclear Power Plant

The Fukushima I Nuclear Power Plant, often referred to as Fukushima Dai-ichi (Dai-ichi simply means first or number 1), is a nuclear power plant located in the town of Okuma in the Futaba District of Fukushima Prefecture, Japan. The plant consists of six boiling water reactors. These light water reactors have a combined power of 4.7 GW, making Fukushima I one of the 25 largest nuclear power stations in the world. Fukushima I was the first nuclear plant to be constructed and run entirely by the Tokyo Electric Power Company (TEPCO). (Wikipedia)

Fukushima II Nuclear Power Plant, 11.5 kilometres (7.1 mi) to the south, is also run by TEPCO.

Fukushima II Nuclear Power Plant

The Fukushima II Nuclear Power Plant, or Fukushima Daini (Daini simply means second or number 2), is a nuclear power plant located in the town of Naraha and Tomioka in the Futaba District of Fukushima Prefecture, Japan. Like the Fukushima I, 11.5 kilometres (7.1 mi) to the north, it is run by the Tokyo Electric Power Company. (Wikipedia) There are 4 reactors at this site.

BBC: Q & A: Radiation fears after Japan blast

The BBC provided a question and answer overview of the problems facing Japan at the moment. While the overall assessment seems to be that this situation is not going to turn into another Chernobyl, that doesn’t mean there are not concerns and that Japanese authorities must act quickly. What seems to be tricky in determining what the risks are is that over time, the incidence of cancer may rise. In the short-term, officials may do all they can for the public’s safety but understanding how the risks posed by the exposure to small doses of radiation may affect anybody over the span of their life is difficult.

References

Wikipedia: 2011 Sendai earthquake and tsunami

Wikipedia: Timeline of the Fukushima nuclear accidents

Wikipedia: Fukushima I nuclear accidents

Wikipedia: Sievert

The sievert (symbol: Sv) is the SI derived unit of dose equivalent. It attempts to quantitatively evaluate the biological effects of radiation as opposed to the physical aspects, which are characterised by the absorbed dose, measured in gray. It is named after Rolf Sievert, a Swedish medical physicist renowned for work on radiation dosage measurement and research into the biological effects of radiation.

Wikipedia: Gray (unit)

The gray (symbol: Gy) is the SI unit of absorbed radiation dose of ionizing radiation (for example, X-rays), and is defined as the absorption of one joule of ionizing radiation by one kilogram of matter (usually human tissue). It is named after the British physicist Louis Harold Gray. It supersedes the old cgs unit, the rad (10 mGy), which is now “strongly discouraged” by the author style guide of the United States National Institute of Standards and Technology, though still commonly used within the US.

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