Fukushima situation as of Wednesday, 2011-03-16

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Do, 2011-03-17 07:25 by Hans-Georg

Situation worsens - still no cause for alarm

By Lewis Page

Posted in Physics, 16th March 2011 14:14 GMT

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See also: Fukushima status

The situation at the Fukushima Daiichi powerplant has worsened significantly as it becomes clear that one and possibly two reactors there have suffered a breach in primary containment, making the incident definitely the second worst nuclear accident yet seen.

Nonetheless its human consequences seem certain to remain insignificant against the horrifying backdrop of the earthquake tragedy elsewhere in Japan: and there remain no grounds for anyone to fear for their health.

Nuclear experts at MIT confirm [1] that leaks from the suppression chamber at Daiichi No 2 reactor reported yesterday do in fact amount to a breach in primary containment, contradicting a statement supplied to World Nuclear News at the time by plant operator TEPCO. The doughnut-shaped suppression chamber is believed to have been damaged by a hydrogen-oxygen explosion like those which have wracked the site since the weekend, but this time occurring inside the primary containment shell rather than outside as previously seen.

It now appears that a similar breach may have taken place at the plant's No 3 reactor: Japanese chief cabinet secretary Edano raised the possibility [2] in a briefing during the early hours of today (UK time). There was no loud blast as at No 2, but a brief burst of intense radiation emissions similar to that following the No 2 rupture has been seen at No 3.

The original radiation surge following the No 2 breach prompted withdrawal of most of the hundreds of workers then on site. A small team remained. The initial rise in radiation then declined, but the further surge early this morning led to a brief total evacuation. However, as this is written a small team is back on site. Plant personnel are reportedly spending most of their time in heavily protected control rooms.

According to the MIT experts, these rises in radiation will have been caused mostly by short-lived radioactive isotopes within the cloud of steam and gases emitted from reactor No 2 and possibly from No 3: the bulk of these decay to small levels within minutes. Most of them are isotopes of noble gases such as argon, meaning that they are chemically unreactive and can't be absorbed by human bodies, the ground, plants or animals etc.

As of latest reports, the Nos 1, 2 and 3 reactor cores are still being cooled using seawater pumped by the site's firefighting systems. Their residual heat has now dropped to …

Read the complete article in The Register

See also: Fukushima status