The Nuclear and Industrial Safety Agency said faulty thermometer measurements were likely responsible for the alarming spikes in temperature readings at the Fukushima No. 1 nuclear power plant's damaged No. 2 reactor.
The Nuclear and Industrial Safety Agency said faulty thermometer measurements were likely responsible for the alarming spikes in temperature readings at the Fukushima No. 1 nuclear power plant's damaged No. 2 reactor.
NISA officials told a news conference on Feb. 12 that there are apparently no safety problems and that a state of cold shutdown has probably been maintained at the plant.
However, the officials said NISA will monitor the results of measures taken by Tokyo Electric Power Co., the plant’s operator, to inject more water into the reactor because they could not totally rule out the possibility the temperature at the base of the reactor’s pressure vessel is actually rising.
Under current safety regulations, the temperature at the base of the No. 2 reactor's pressure vessel should be kept at 80 degrees or less.
From around midday on Feb. 12, the thermometer showed temperatures ranging between 73 and 88 degrees. But NISA said such violent fluctuations indicate the likelihood of a glitch in the measuring system.
Three other thermometers—two at the base of the same pressure vessel and another 1.5 meters below—have shown no rise in the temperature, NISA said.
In addition, there have been no anomalies in the concentration of radioactive substances in the gas inside the nuclear reactor, NISA said.
NISA called on TEPCO to discuss a possible review of the methods to estimate temperatures in the pressure vessel and to file a report within the coming days.