3rd explosion at Daiichi Nuclear Reactor

By Hiroku Tabuchi, Keith Bradsher and Matthew L. Wald, New York Times, March 14, 2011
TOKYO — An explosion early Tuesday morning damaged the No. 2 reactor at Japan’s Fukushima Daiichi Nuclear Power Station, the third in a series of blasts that have now hit each of the three crippled reactors at the plant, plant officials said.
It was not immediately clear if the blast was caused by the buildup of hydrogen, as occurred at the two other reactors at Daiichi — one on Saturday and the most recent one on Monday, when there was also a large explosion at the No. 3 reactor. Some early reports in the Japanese press suggested the latest explosion amounted to a different and more critical problem than the previous two.
This explosion, reported to have occurred at 6:14 a.m., happened in the “pressure suppression room” in the cooling area of the reactor and inflicted some degree of damage on the pool of water used to cool the reactor, officials of Tokyo Electric Power said. But they did not say whether or not the incident had impacted the integrity of the steel containment structure that shields the nuclear fuel.
Radiation levels around plant spiked after the explosion to 8,217 microsieverts an hour from 1,941 about 40 minutes earlier, the company said. Some emergency workers there were evacuated, though the levels would have to rise far higher to pose an immediate threat to health, officials said.
Any damage to the steel containment vessel of a nuclear reactor is considered critical because it raises the prospect of an uncontrolled release of radioactive material and full meltdown of the nuclear fuel inside. To date, even during the four-day crisis in Japan that amounts to the worst nuclear accident since Chernobyl, workers had managed to avoid a breach of a containment vessel and had limited releases of radioactive steam to relatively low levels.
Naturally, everyone around the world is watching and waiting to see how serious the exposure of the nuclear rods has been, and how likely is the potential for a full meltdown. There seems to be a significant difference between the structure of these reactors and the one in Chernobyl, especially with respect to the containment structure...something missing in Chernobyl, according to reports from various sources.
While the world is rivetted to the streaming video of the tsunami, and the impact of the earthquake, it seems that the nuclear scare is what is really frightening many people, both in Japan and in other countries.
Experts in Canada, on the west coast, have indicated that there is little danger of significant radiation reaching North America even in a worse case scenario.
However, reports also point to the nuclear reactor located on a similar fault line in California, where the potential for earthquakes is also high, and where the danger to the reactor is also elevated. When asked about the safety of the California reactor, one spokesman, appearing on ABC World News, assured the interviewer that the facility was safe even in the event of a substantial quake.
The calm, stoic dignity of the Japanese people, in the face of such monumental tragedy is, at least to this observer, quite remarkable. The preparations, the orderliness, the complete absence of looting, and the diligence of the people to both remain vigilant to public announcements and to follow their instructions are all testament to the pride and the honour and the discipline of this island empire that lies today in ruins.