An analysis by the Japan Nuclear Energy Safety Organization has shown that the level of the water filling the crippled No. 1 reactor at the Fukushima Daiichi nuclear power plant may be far lower than estimated by plant operator Tokyo Electric Power Co., officials of the organization said Tuesday.
The organization of nuclear experts estimated that the water in the primary containment vessel is only 40 centimeters deep. The utility known as TEPCO has estimated the water level to be about 1.9 meters.
Not disputed is the fact coolant water injected into the reactor is leaking as a result of the accident at the plant. JNES officials noted there are “uncertainties” in their analysis.
TEPCO spokesman Junichi Matsumoto said Tuesday the company hopes to insert an endoscope into the reactor by the end of the year to determine the actual water level.
Matsumoto declined to comment about the analysis by JNES, but said that what is important is that the nuclear fuel, which has melted through the pressure vessel and accumulated at the bottom of the outer primary container, is covered with water and kept cool.
“We believe that the fuel inside is being cooled,” he added, referring to the reactor’s temperature data.
JNES analyzed the water level based on the assumption that the primary container is filled with steam, which is created when water cools the fuel, and nitrogen, which is inserted to prevent hydrogen explosions. It assumed gas is leaking from the container’s upper part and the coolant water from the lower part.
JNES thinks that the water injected into the reactor may be leaking from a hole located in a section connecting the primary container and the suppression pool, leaving the container with water just 40 cm in depth.
The hole is believed to be about 2 cm in diameter. TEPCO has already inserted an endoscope into the crippled No. 2 reactor and found the water level at a lower-than-expected 60 cm deep.
The Nos. 1 to 3 reactors have suffered meltdowns in the wake of the accident, triggered by a magnitude 9.0 earthquake and tsunami on March 11, 2011.(Kyodo)