A monitoring system at Japan's damaged nuclear plant failed in the power outage which took out the plant's cooling systems after the March quake and tsunami, depriving authorities of vital data to predict contamination, a news report said Tuesday.
The loss of data from the Emergency Response Support System (ERSS) probably delayed the evacuation order around the Fukushima Daiichi nuclear power plant around 250 kilometres north-east of Tokyo, Kyodo News agency quoted an anonymous source as saying.
The ERSS monitors pressures and temperatures in and around the reactors, and runs predictions to assess how much radioactive material might be released in various failure scenarios, dpa reported.
Is is meant to provide that data to another system, which then calculates how that radioactive material might spread to contaminate the surrounding area in the event of an accident.
The government drew criticism last week for not implementing that second system, known as the System for Prediction of Environmental Emergency Dose Information (SPEEDI), quickly or thoroughly enough.
The plant has been leaking radioactive materials into the air and sea since it was hit by the March 11 quake and tsunami.
Critics have said information on the likely contamination from several fires and explosions at the plant was not available until April. And when the government did calculate models for the radioactive material's spread, it sent that data to the United Nations weeks without informing the Japanese public, reports said.
The accident response headquarters, formed jointly by the government and the plant's operator Tokyo Electric Power Co, said Monday that roughly 5,000 estimates of how radioactive substances would disperse had been made since the beginning but they had not been made public, Kyodo said.
The secrecy was to avoid "panic in the whole of society," lawmaker Goshi Hosono, head of the secretariat of the ruling Democratic Party of Japan, was quoted by Kyodo as saying.
The failure of the two systems, which cost a total of 28 billion yen (345 million dollars) to install and maintain, has prompted questions over the disaster readiness of Japan's nuclear sector.
The ERSS had never been used since it was installed in 1987, as there had been no accident serious enough to trigger its activation until March, Kyodo's Tuesday report said.
The system was overwhelmed by the March 11 events, which were "larger than initially envisioned," Kyodo reported. The ERSS remains unable to collect data from any of the plant's troubled reactors.