Title: Takahashi_FUKUSHIMA_REPORT, The Fukushima Nuclear Power Plant Disaster: What Happened in March 2011
Source: World Federation of Science Journalists
Author: Mariko Takahashi, Asahi Shimbun, senior staff writer (science correspondent)
Fire at Shutdown Unit 4
The series of accidents continued. At Unit 4, which had been out of service for regular inspection at the time of the quake, an explosion was heard in the early morning on March 15, and at 9:38 a.m. a fire was reported. Flames broke out on the fourth level of the building; the fire died down on its own by 11:00 a.m. but it created a 8 square meter hole in the wall. Why would a fire break out at the shut down Unit 4? Presumably, it originated in the fuel storage pool.
The nuclear reactor buildings each contain a deep pool where the fuel rods are kept temporarily. All of the fuel rods in Unit 4 had been moved to this pool. Including spent fuel, the pool contained about 1,300 rods, the largest number at any of the six Fukushima No. 1 units. Spent fuel continues to generate decay heat, so a cooling system is ordinarily in operation to stabilize the temperature in the pool. Because of the electricity blackout, however, that system had ceased to function.
The water in the pool, which is usually 40 degrees, had risen to 85 degrees by the evening of the 14th. It is most likely that the water had evaporated, leaving the fuel rods exposed, and that the interaction of steam with the alloy covering the rods had been producing hydrogen. With hydrogen forming, conditions must have been ripe for either an explosion or fire. The level of radiation on the grounds of the power plant mounted sharply from the morning of March 15. The highest level was recorded on the inland side of Unit 3 soon after 10:00 a.m., reaching 400 millisieverts (mSv) per hour at its highest. That figure, if expressed by the microsievert unit used thus far, would be 400,000 μSv.
Read the report here
The author has an article today in Asahi’s AJW: Reality check on the consequences of Fukushima nuclear accident
Takahashi’s previous articles for Asahi have also reinforced the nuclear industry’s point of view:
- Concentrations of radioactive substances in the air falling quickly
- Radiation levels to drop to 3/4 in 1 year, 1/2 in 3 years
- POINT OF VIEW/ Mariko Takahashi: Hatoyama’s questionable Nature article
Published: March 16th, 2012 at 12:00 am ET