Japanese authorities are continuing water spraying operations at unit 3 of the Fukushima Daiichi nuclear power station as the immediate concern remains for spent fuel storage conditions.

The temperature of the spent fuel pool at unit 3 had reached 84°C on 16 March and has not been measured since. Typical temperatures are around 30°C.

In response to the situation yesterday morning (17 March) military helicopters dropped seawater over unit 3. Four drops took place between 09:48 and 10:01, each dispatching 7.5tons of water. Lead plates were installed at the bottom of the helicopters to shield radiation and crew members wore radiation protection suits.

On Thursday afternoon riot police arrived at the Fukushima Daiichi site to pump water into reactor 3 from the ground. Water spraying operations took place between around 19:00, but they were unsuccessful according to NHK news as the water cannons were unable to get close enough to the unit due to high radiation levels.

Shortly afterwards (19:35-20:09) the Japan Self-Defence Forces sprayed 30 tons of water into unit 3 from the ground using five special military fire trucks. The effect of this operation is still being evaluated.

As of 06:30 this morning, 18 March, the Tokyo Fire Department was continuing to spray water into reactor 3, the Nuclear and Industrial Safety Agency reported.

Meanwhile engineers have successfully begun laying an external grid power line cable between the transmission line and unit 2. They plan to reconnect power to unit 2 once the spraying of water on the unit 3 reactor building is completed.

Radiation Monitoring

The International Atomic Energy Agency said 17 March that it is regularly receiving dose rate information from 47 Japanese cities. In Tokyo, there had been no significant change in radiation levels it said, confirming that levels remain well below those that are dangerous to human health.

In some locations at around 30km from the Fukushima plant, the dose rates rose significantly between 16 and 17 March (in one location from 80 to 170 microsievert per hour and in another from 26 to 95 microsievert per hour). But this was not the case at all locations at this distance from the plants.

Dose rates in the range 3 to 170 microsievert per hour to the north-west of the power plant were observed, with the higher levels observed around 30 km from the plant. Dose rates in other directions were in the 1 to 5 microsievert per hour range.

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