The health ministry is investigating allegations that a construction company ordered its workers at the crippled Fukushima No. 1 nuclear power plant to cover their dosimeters with lead to indicate lower exposure levels, according to sources.
The Health, Labor and Welfare Ministry searched several sites in Fukushima Prefecture on Saturday and confirmed working conditions at the nuclear plant operated by Tokyo Electric Power Co.
According to the ministry, the construction company that issued the illegal instruction is Build-up, which is based in Namie, Fukushima Prefecture.
Build-up was a subcontractor of Tokyo Energy & Systems Inc., a Tokyo-based group firm of TEPCO entrusted with restoring the plant, according to sources.
In December, a Build-up executive allegedly instructed nine onsite workers to place lead covers over their dosimeters so they would record lower radiation exposure levels.
Under the Industrial Safety and Health Law, such workers are permitted to receive a maximum exposure of 50 millisieverts a year. Employers are required to accurately measure workers' exposure levels.
If the executive ordered the workers to cover their meters to manipulate exposure readings, it would constitute a violation of the law that is punishable by up to six months in prison or a fine of up 500,000 yen.
TEPCO said Tokyo Energy & Systems reported Thursday that lead covers for the radiation meters had been produced. However, Tokyo Energy & Systems also said the covers had not been used during work at the stricken plant.
TEPCO said it instructed Tokyo Energy & Systems to further investigate the matter and report its findings.
On Saturday, the Fukushima Labor Bureau and the Tomioka Labor Standards Inspection Office inspected Tokyo Energy & Systems' office in Fukushima Prefecture.