Workers on Friday were preparing to spray resin on the rubble of the blast-hit reactor.
Most of the company’s dosimeters, which measure exposure to radiation, were lost in last month’s tsunami. Japan’s Nuclear and Industrial Safety Agency said in the immediate aftermath of the disaster, emergency crews had to work in groups, sharing dosimeters.
A spokesperson for the agency declined to clarify when it had become aware of the shortage of radiation meters, but said Tepco has since sourced enough for all workers, and would no longer workers to go into the plant without a detector.
Since the start of the crisis, a total of 21 workers have been exposed to radiation exceeding 100 millisieverts, the lowest level at which an increase in cancer risk is evident, according to the safety agency.
The maximum level of radiation to which emergency workers should be exposed is 100 millisieverts, under agency rules, but the limit has been raised to 250 millisieverts specifically for work at Fukushima.
Tepco is one of the world’s largest utilities and could face huge costs and compensation claims, but it might end up receiving taxpayer money because of the need to maintain a stable power supply.