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UPDATE 8: Water on Fukushima fuel/ radiation levels remain elevated

Fukushima 16 March.jpgThis morning Japan time, two CH 47 Chinook helicopters began dropping tons of water onto the used nuclear fuel stored in pools at the unit 3 and unit 4 reactor. The helicopters made four passes, and have claimed some success, though footage on NHK television shows most of the water dispersing before it reaches the reactor building. Fire trucks from the military and civil authorities have also arrived to douse the fuel pools using high-power water cannons.

So far the efforts have done little to reduce radiation levels around the plant: NHK reports that Tokyo Electric Power Company (TEPCO), which operates the plant, has seen no change in radiation levels 100 m from unit 3 (the broadcaster does not give a number). The Nuclear Industrial Safety Agency reports that radioactivity forced workers to temporarily evacuate the unit 3 control room yesterday.

NHK also reports elevated radiation levels around Fukushima prefecture. At Fukushima City, 65 km northwest of the plant and well outside the evacuation zone, authorities reported levels as high as 13.9 μSv/hr (0.0139 mSv/hr), according to the broadcaster. That is well above the background, and equivalent to 120 mSv/yr in rough terms, but it will only pose a threat to human health if it continues for a long period of time (see this post for more about the numbers).

Meanwhile, recent updates from the International Atomic Energy Agency and the Japan Atomic Industrial Forum have shed light on why the spent fuel pool at unit 4 was particularly vulnerable to an accident. According to the IAEA, plant operators removed fuel from unit 4 on 30 November of last year and transferred it to the pool as part of routine maintenance. When the quake struck, the pool’s cooling system was knocked out, and it began to heat up.

Under normal conditions, the spent fuel would have been too cool to cause much trouble (temperatures have been very slowly rising in the unit 5 and 6 fuel pools , which are in a similar situation). But in unit 4, the fuel was much fresher, and hence more radioactive. This may explain why the pool lost its water, and why the release of radiation has been particularly severe.

The always helpful JAIF chart shows that little else has changed since yesterday. Some instrumentation has been lost on the unit 2 reactor and sea water continues to flood all three of the stricken cores. A NISA spokesman that efforts are now underway to restore power to the site, which could improve instrumentation and allow for cooling to be restored to the spent fuel pools.

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

Image: Digital Globe, 16 March 2011


  1. Report this comment

    Dr Kingsley Jones said:

    I estimated from Union of Concerned Scientists Data that the pond was about 10m by 10 m by 15 m and that the lower third contained fuel rods. Given that the rods need to be exposed to generate hydrogen that says 2/3 of the pool needed to evaporate from fri afternoon to tuesday morning. Doing the math (about 1,500 cubic metres with 1,000 evaporated over four days) I estimate they need 200 liters per minute of pumping capacity into the pond. That is doable with a firehose, but represents about 20 chinook loads per day at 100% delivery. In short, this is a real problem.

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    Prasad said:

    If radiation increases Japan & Japan’s Neighbouring countries will also face many problems

  3. Report this comment

    Q said:

    What happened when the M9.0 earthquake occurred undersea? I suspect there was a nuclear explosion experiment at the same place. I know it’s not a good time to say that, but there are many suspensions I cannot understand well if following a normal course of thinking:

    First, why Japan only uses the first and second generations of nuclear technology in almost all 55 nuclear plants in Japan while its companies instantly export the more safer and high-efficient third generation of nuclear plant tech to other countries? If you know some nuclear tech knowledge you will find that the third generation of nuclear tech using oxide-Uranium which cannot be used to make nuclear weapon, while the first and second G of nuclear tech use Plutonium-Uranium alloy which can be purified to make nuclear bombs! It is possible that Japan is purifying nuclear weapon materials under the veil of feeding its nuclear plants in the same nuclear factories.

    Second, if you have checked the recent earthquake record around northeast of Japan you will find that there are a series of slight earthquakes, almost all of them, ranging from M5 to M6 under the sea within ten years, which is the same magnitude of typical nuclear explosion experiment under ground or under sea. This phenomenon is unique around areas around Japan. And what’s more, this area has a very low density of population, which is very rare in the country with very high population density in average. If I have a right to choose a place to do nuclear weapon experiment for Japan, I will definitely vote this place.

    Third, why the US military ship detected a strong radiation dose hundreds miles away from the crippled nuclear plant in the sea while the government disclaimed that there was only small amount of radiation detected near the plant? Remember that the US navi force and residents also observed big whirlpool raised close to the beach of epicenter which looks like some undersea tunnel collapsed thereafter …

    Fourth, why the government refuse any international experts, especially experts from IAEA, help them check the crippled plant by disclaiming yesterday that only Japanese experts can approach to the plant? Is there any secret in the plant? …

    So, it is possible that when this time Japan did the nuclear bomb experiment, unfortunately, a devastation happened…

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    Yohak said:

    The decision to drop water over the spent fuel pools with CH 47 Chinook helicopters is probably inefficient because is really difficult hit in the middle of so little target.

    Even without radioactivity, it is a very challenging task to a pilot. I have seen firefighters in my country trying to extinguish a forest fire with with light aircraft, helicopters and hydroplanes, and they needed a lot of flights (and we are talking now of a more fierce radioactive fire).

    At first, maybe a chopper with a hose could have poured water directly into the pools, but now radiaction levels make impossible that kind of task.

    TEPCO and the Japanese government are reacting again too late, and in a matter of time the unique solution is going to be sealing the whole plant.

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    Kiumars Lalezarzadeh, Ph.D. said:

    Kiumars Lalezarzadeh, Ph.D.

    March 16, 2011

    There may be available alternatives to cool or control the radiations.

    a) Use blue cool lighting all around

    b) Drop dry ice or ice on plant

    c) Use snow machines to shoot snow over / into the plants from ground, air or sea

    d) Deploy ships that would pump and shoot water on / into the plants

    e) Use sub-water pumps and pipes off shore to shoot water from the ocean on to / into the nuclear plants

    f) Place aluminum / lead walls all around the perimeter as close as possible

    g) Place rods and generate snow, rain and/or hail over / about the plants

    h) Create clouds of rain / hail / snow

    i) Place cooling walls all around as close as possible

    j) Create heaps of snow all around the area

    k) Reel down the water / ice / dry ice into the plant

    l) Reel down a robotic arm to move the element out

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