Damage to spent fuel rods stored in the pool of the No. 4 reactor of the crippled Fukushima No. 1 nuclear power plant is limited, according to plant operator Tokyo Electric Power Co.
Damage to spent fuel rods stored in the pool of the No. 4 reactor of the crippled Fukushima No. 1 nuclear power plant is limited, according to plant operator Tokyo Electric Power Co.
TEPCO on Wednesday released the results of its analysis of the first batch of water collected from the storage pool.
The concentration of radioactive substances in the sample water is higher than that in cooling water in a reactor during normal operations. But it is not high enough to raise the possibility of fuel melting. Based on the results, TEPCO presumes that damage to the nuclear fuel, if any, has been limited.
The results also indicate that the water level of the storage pool was about 2 meters above the upper end of the fuel rods, with all the fuel submerged. On Wednesday, the water level rose by about 1 meter after water was sprayed in.
Before the March 11 earthquake, all the fuel rods in the No. 4 reactor were moved to the storage pool for regular inspection. After the reactor building was demolished in a hydrogen explosion after the tsunami, there was growing concern that the fuel in the pool had been severely damaged.
On Tuesday, TEPCO collected about 400cc of water from the fuel storage pool of the No. 4 reactor, using concrete pumping trucks, and analyzed the radioactivity level of the collected water. The results show that radioactivity levels of iodine 131, cesium 134 and cesium 137 stood at 220 becquerels, 88 becquerels and 93 becquerels per cubic centimeter, respectively.
In normal situations, those figures are either below detection limits or below 1 becquerel, TEPCO officials said.
The radioactivity levels of the sample water are lower than the contaminated water in the turbine buildings at the plant. With these results, TEPCO officials said that nuclear fuel in the No. 4 reactor has been only partially damaged.
The utility hinted at the possibility that damage to the fuel was caused by falling objects when the explosion occurred, as well as the possibility that radioactive substances flowing near the reactor were mixed into the pool water.
On Tuesday, 660 tons of contaminated water inside a tunnel outside the turbine building of the No. 2 reactor was moved into a condenser in the building. The water level in a shaft in the tunnel dropped by 6 centimeters. The water level in the basement of the turbine building has also decreased, raising the possibility of the water in these two locations being connected.