The IAEA has shared that as of 05:15 UTC, Japanese authorities reported the following about the conditions of the six reactors:
Unit 1: Workers have restored lighting in the control room, and recovered the ability to use some instrumentation. As of March 25, fresh water is being pumped into the pressure vessel instead of seawater, in an effort to minimize corrosion.
Unit 2: Seawater injection continues and pressure in the reactor vessel is stable.
Unit 3: Workers are pumping fresh water into the reactor vessel, and seawater into the spent fuel pool. Fire fighters sprayed water into the building from outside yesterday.
Unit 4: Workers used a concrete truck to pour water into the spent fuel pool, while simultaneously pumping seawater through the spent fuel pool’s own coolant system.
Units 5 and 6: Both reactors are in cold shutdown, with fuel pool temperatures stabilized at acceptable levels.
Effects on Health and Safety
A TEPCO press release (http://www.tepco.co.jp/en/press/corp-com/release/11032503-e.html) dated March 25 estimated that three workers, who were laying electrical cable, received doses of around 170 milliSievert to the legs. Doses of these levels, when caused by beta radiation, often cause burns to the skin. The workers were transferred to the hospital, and decontaminated. TEPCO maintains that the workers did not heed the alarms of their radiation dosimeters, believing radiation levels to be low in the area. It has been speculated that rising radiation levels in water surrounding Unit 3 is the result of a leak; updates about this leak will be made as information becomes available. Much has been made of this leak in the media, as Reactor 3 is fueled by a mixture of uranium and plutonium. However, measurements taken of the water in the plant (the water to which workers were exposed) did not detect the presence of either uranium or plutonium—just fission products.
On March 25, Japanese authorities reported to the IAEA that they had recorded the radiation doses to the thyroids of 66 children living just outside the perimeter of the evacuation zone. These measurements are important because the thyroid tends to accumulate iodine, and radioactive isotopes of iodine make up much of the radiation field being measured far from the reactor site. In addition, children are especially sensitive. The measurements showed no significant deviations from background radiation levels in these children, 14 of whom were infants.
Seawater 30 km offshore from the facility has been tested for the presence of radioactive species. Measurements revealed the level of iodine-131 to be at their legal limits, and cesium-137 to be well below their legal limits. Because these levels dilute with increased distance, it would take months or years for cesium-137 to be detected on other Pacific shores, predicts the IAEA’s Marine Environmental Laboratory. The tiny quantities of radionuclides already being measured on foreign shores are as a result of atmospheric transport, not dispersion in seawater.