by Pierre-Henri Lab
Translated Monday 21 March 2011, by Henry Crapoand reviewed by
Workers at the Nuclear power plant in Fukushima attempt, surely at the peril of their own lives, to prevent the situation from getting worse. Some quantities of water have been successfully dropped on the reactors and fuel rod storage basins.
In order to prevent the catastrophe from becoming even more serious. Yesterday, the employees of the Tokyo Electric Power company (Tepco) and soldiers of the Japanese self-defense forces attempted to stabilize the situation at the Hukushima Dai-ichi nuclear power plant, which remains, even according to the Japanese Agency for Nuclear Security, "extremely preoccupying". The United States provided aid to the Japanese authorities. France is also mobilized to help. In addition to teams to back up the Japanese, the EDF  has announced sending 100 metric tons of boric acid, of which the particularity is its ability to slow down the radioactivity.
To Reduce the Heating of the Used Fuel Rods
The efforts of the employees of the power plant are directed mainly toward the pools for storage of used fuel rods from reactors 3 and 4, which are in the most critical state. According to information published on the web site of the French Institute for Radiological Protection and Nuclear Security  water in the two pools started boiling yesterday  morning, due to the failure of the cooling system. During the morning, four helicopters took turns dropping water on the basin for reactor 3, in order to prevent it from drying up completely. Now a substantial level of water is crucial in order to limit the heating of the fuel rods, and to avoid their degradation, which would imply the release of large amounts of radioactivity into the atmosphere. It seems that two of the deliveries of water missed their mark. Two special trucks provided by the Japanese army joined the operation to "wet down" the basin, the Japanese television channel NHK reported. Some air-droppings of water were successful, it seems, in the basin of reactor 4, which one had feared for a while had become completely dry. The success of this operation constitutes, according to the director of the IRSN, Thierry Charles, quoted by Agence France Presse, "a glimmer of hope". This permits a gain in time for the teams on the site to reestablish the electrical supply for the power plant, in order to restart an emergency cooling system that would be longer lasting and more efficient.
Expected to be in place yesterday afternoon, the reestablishment of electric power, which should now be in place Friday, is also vital in order to improve the situations for reactors 1,2,3, and 4, which remain critical. According to information furnished by Tepco and forwarded by the IRSN, the cores of reactors 1, 2, and 3 are partially damaged. In an attempt to reestablish a more efficient cooling system, employees of Tepco have taken steps to inject sea water, as a way to prevent any new degradation. On a regular basis, decompression of the perimeter confinement chambers take place for the four reactors, in order to maintain their integrity, this implying a release of radioactivity into the atmosphere.
The Command Centers for the Plant are "Highly Radioactive"
The impact on workers who intervene in the interior of the plant is a matter of the utmost concern. Despite the use of protective suits, no one has any doubt that they act in peril for their lives, or certainly in peril for their health. "On the site, working conditions are frightful," explains Thierry Charles. The IRSN reports that the command centers for reactors 1,2,3, and 4 are "highly radioactive", so all interventions are limited in duration. Around the storage basins for used fuel rods from reactors 3 and 4, the levels of radioactivity recorded are also very high. The workers were forced to interrupt for some hours their spraying of water into the basin of reactor 3.
The extent of effects on the Japanese population remains uncertain. The zone for evacuation of the population near the power plant was raised to 30 kilometers. Experts estimate that at the present time the volume of radioactivity released from the Fukushima plant is about 10% of that released at Tchernobyl in 1986. In Tokyo, levels of radioactivity at 0.809 microsieverts  were measured. This, according to experts, represents no danger to the population, but it does remain 20 times higher than the normal radiation level.
 Électricité de France
 Becquerel versus Millisievert? While the Japanese authorities announced, yesterday afternoon, doses of radiation not exceeding 0.809 microsieverts (0.08 millisieverts) per hour in Tokyo — ten times higher than that received by a patient undergoing a dental x-ray, according to experts, the Commission for research and independent information on radioactivity (CRIIRAD) sounded an alert: the measures recorded in the Japanese capital are "worrisome results". For a period of 42 hours the activity of Iodine 131 climbed to an average of 14.9 becquerels per cubic meter, that of Iodine 132 to 14.5 Bq/m3, that of cesium 134 to 3.4 Bq/m3, and that of cesium 137 to 3.2 Bq/m3, reports the CRIIRAD. But, "in a normal situation, the only radionucleide to be measured in the atmosphere is cesium 137, but at a level about a million times less", emphasizes the Association. Contradictory or not? To figure this out, bear in mind that the becquerel measures radioactivity, while the sievert measures its impact on the human body.