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Fukushima nuclear crisis: new setbacks hit control efforts

Two weeks into the Fukushima reactor crisis – and after a week of growing optimism during which authorities seemed to be gaining the upper-hand in getting the plant under control – today brought renewed concern after a series of setbacks. Naoto Kan, the prime minister, told a press conference today that the situation at the plant ’’still does not warrant optimism" and was not near to being resolved.

Here’s today’s highlights:

Core of reactor 3 possibly breached. Japan’s Nuclear and Industrial Safety Agency today said this was highly likely, NHK TV reported, and that the highly-contaminated water at the plant seems likely to have come from the core, not spent fuel ponds. Reactor 3 is where three workers were injured yesterday by exposure to high levels of radiation, when water overtopped their boots while wading through floodwater – now known to be highly contaminated – in a basement floor.

Reactor 3 also is the only reactor at the plant to use plutonium as part of a mixed oxide fuel with uranium, increasing the hazards of leaked radiation. The mix of radionuclides found in the water and published today by TEPCO, the plant operator, are novel compared to other escapes over the past two weeks (see image). Fission products so far detected in escaped radiation have been volatiles such as Cs-137 and I-131 released during ventings to reduce reactor pressure. The new mix contains elements that are not volatile, and so must have leaked from broken fuel rods into the water.

<IMG SRC=“https://www.tepco.co.jp/en/press/corp-com/release/betu11_e/images/110325_01.gif” width=300

Highly contaminated water pool found today at reactor 1, and pools of contaminated water also found at reactors 2 and 4, Kyodo news reports. The water in underground parts of the buildings is thought to have come from either the cores or spent fuel pools – reactor 4 contained no fuel at the time of the accident, and its fuel rods were being stored in the pools.

Evacuation zones around plant extended. People living in the 10km radius beyond the current 20 km evacuation zone, were today encouraged by the government to leave voluntarily.

TEPCO, the plant operator, is starting to switch from seawater to freshwater to cool the reactors as salt crusts on the rods were hampering flow. The New York Times had an interesting piece earlier this week on the risk of salt crusts resulting in fuel melt.

Japan’s science ministry has started posting data from radiation monitoring of coastal waters. The first samples from 30 km off-shore had surface seawater concentrations of 24.9 to 76.8 Bq/l of I-131, and 11.2 to 24.1 Bq/l of Cs-137. For a discussion of what these units mean, see here, and here.

A dilute radioactive cloud has already crossed much of the Northern Hemisphere. Austria’s weather service, the Central Institute for Meteorology and Geodynamics in Vienna, reported today that 24 radionuclide detecting stations worldwide run by the Comprehensive Nuclear-Test-Ban Treaty Organization are now detecting Fukushima fallout as far away as Western Europe. See report in English here, and the maps here.

Since the Fukushima accident, the CTBTO network, designed to pick up nuclear tests, has also proven itself to be the key (and indeed unique) system for detecting worldwide fallout from nuclear accidents, as it emphasized tonight. For my recent article on its role here see “”https://www.nature.com/news/2011/110317/full/news.2011.168.html">Radiation data from Japanese disaster starts to filter out." Meanwhile, the German Federal Office for Radiation Protection has followed Austria’s lead in making its findings from the CTBTO’s classified data public.

For full coverage of the Fukushima disaster, go to Nature’s news special.

Comments

  1. Report this comment

    Neil Kitson said:

    You describe “a week of growing optimism during which authorities seemed to be gaining the upper-hand in getting the plant under control” but provide no data. Growing optimism based on what?

    Nature seems as susceptible as CNN to moods based on nothing more than public relations.

  2. Report this comment

    Finley Overbey said:

    @Neil Kitson

    It is not feasible to provide sources for a demographic other than public relations. Unless, of course, we’re in Bhutan. But in the wake of a tsunami, optimism is a word that should be used tentatively at best when describing the population’s feelings.

  3. Report this comment

    Jorge Stolfi said:

    One of the most puzzling/irritating/worrying thing in this event is that, eighteen days after the accident, there is still so little information about the state of the reactors.

    Basically we have at most three pressure readings, two temperatures, and a water level from each reactor, with several day-long gaps and “off-scale” readings. Moreover, we have no information on how these quantities are measured.

    I suspect that the pressure readings are taken at the ends of the fire-control water pipes, outside the building. The “core” temperature may be measured on the outer surface of the RPV. Is that so?

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