One Japanese expat blogger reports that life is beginning to return to normal away from the devastated northern coast, with the Shinkansen train running again between Kyoto and Tokyo. But as rescuers continue seeking tens of thousands of missing people and delivering aid to stranded victims, news in the northern prefecture (state) of Fukushima worsens. A small radioactive leak led to an explosion at the nuclear plant located there, and now experts are operating on the assumption that a partial nuclear meltdown has or will soon occur. Our thoughts of strength and courage must be with the responders as they put themselves in danger trying to prevent further deterioration. And we will try to put some perspective on what has and could happen at the Fukushima Nuclear Plant, as Japanese residents are experiencing an escalating range of disasters.
Evacuations
As of our last update on the serious issues reported at Japanese nuclear reactors, evacuations had been extended, affecting 170,000 people from a 20-km (12.4 mile) radius around Fukushima Daiichi and another 30,000 people from a 10-km (6.2 mile) radius around Fukushima Daini. Initial evacuations cleared a 3-km range around both sites.
Minor, and Controlled, Radiation Releases
The evacuations were primarly a precaution as nuclear plant operators began controlled releases of pressure, undertaken with the approval of international and Japanese nuclear safety authorities. Japanese nuclear representatives offered reassurances that radiation releases remained minor, estimating the exposures as approximately the same as one year of natural radiation (or about 35-40 chest x-rays). Residents were given iodine to reduce their absorption of radioactive iodine.
Explosion, Nuclear Fuel not Affected
At mid-day on Saturday 12 March, an explosion shook Unit 1 at the Fukushima Daiichi plant. Four power plant operators were reported taken to hospital with injuries, but the damage was reported as restricted to the building housing the unit, not affecting primary containment around the nuclear fuel rods. Early reports were not clear but seemed to suggest that radioactive elements detected around the plant did not yet indicate releases from the nuclear fuel rods, and that radiation levels dropped after the explosion, consistent with a discontinuation of controlled pressure releases.
The Japanese Nuclear and Industrial Safety Agency (NISA), ranked the explosion at Unit 1 as 4 on a scale of 7 -- indicating an 'Accident with Local Consequences.' A decision was made to begin pumping seawater enriched with boron into the core at the damaged unit. Boron further aids cooling by interrupting the nuclear fission reaction chain. The decision most probably means that Unit 1 has been sacrificed and cannot be restored to operation.
Partial Nuclear Meltdown
Today, the news has worsened yet again. The international press cites an unnamed "top Japanese official" as saying that a partial meltdown is likely already underway at one reactor.
Local press, however, is reporting that Chief Cabinet Secretary Yukio Edano denies that a meltdown has occurred, although the core at Unit 3 may be deformed due to overheating. The same source cites Hidehiko Nishiyama, a senior official of the Economy, Trade and Industry Ministry, as saying that the core of reactor 3 has also melted partially, stating, ''I don't think the fuel rods themselves have been spared damage,'' which could be the source of the international reports allegedly confirming a partial meltdown.
Official news at the International Atomic Energy Association website indicate that no official report of an escalation of the incident at Fukushima has been filed. But experts indicate reports of cesium-137 being detected in the radioactive releases indicate with certainty that the nuclear fuel is compromised.
Hope for a Quick Cooldown
Nonetheless, experts reacting to the escalating state of affairs at Fukushima are responding with the expectation that nuclear fuel is or could soon be involved in the incident. The decision to sacrifice reactors with extreme measures is not taken lightly. The cooling operations will most likely continue for days before an all-clear can be issued.
Meanwhile, the operators that remain on site fighting for a controlled shut down are themselves heroes, working under terrible conditions with great risk to themselves. Our thoughts are with them, and with the many residents of Japan recovering from disaster, as we await further news, hopefully confirming a safe shutdown at Fukushima.
http://www.treehugger.com/files/2011/03/japan-nuclear-response-earthquake-tsunami.php
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