Lead radiation shields forced on workers at the stricken Fukushima No. 1 nuclear power plant to cover their dosimeters masked radiation readings by about 30 percent.
Lead radiation shields forced on workers at the stricken Fukushima No. 1 nuclear power plant to cover their dosimeters masked radiation readings by about 30 percent.
Tokyo Electric Power Co., operator of the plant, and Tokyo Energy and Systems Inc., a TEPCO group company, made the admission Aug. 8 after a test.
TES also acknowledged that when lead dosimeter covers were used on Dec. 1, eight of the subcontractor employees on the premises were working under illegal temporary staffing arrangements.
The falsification of dosimeter readings was revealed by The Asahi Shimbun in July.
TES, conceding it was lax about dosimeter control and employment contract oversight, vowed to take steps to prevent any recurrence.
Officials said the dosimeter covers were created from a 3-millimeter-thick lead plate and used to shield readings among workers trying to contain the threat of leaking radiation following the Great East Japan Earthquake and tsunami last year.
The two companies have amended the radiation dose records for five employees who worked with their dosimeters covered by the lead shield.
A senior executive of Build-Up, a construction firm that subcontracted part of the work assigned to TES by TEPCO, instructed the workers to wear the lead covers.
He denied the covers had any palpable shielding effects, telling The Asahi Shimbun, "The way the dosimeter sounded the alarm (to indicate high radiation levels) was hardly different from when no cover was applied."
The practice almost certainly constitutes a breach of the Industrial Safety and Health Law.
Eight of the 12 employees who toiled in dangerous conditions, including some who did not shield their dosimeters, had been dispatched by companies that had no temporary staffing license.
The eight workers were supposed to be employed temporarily by a Build-Up subsidiary, but had, in fact, been staffed by three other companies, TES officials said.
In a separate case, an employee of another TES subcontractor was found to have worked at the Fukushima No. 1 nuclear plant on Aug. 3 without a personal dosimeter. TES acknowledged it had failed to make sure that even this minimum level of protection was made available to its workers.
To prevent a recurrence, TES will assign someone to the Fukushima No. 1 plant's Main Anti-Earthquake Building to ensure that personal dosimeters are handed out to workers after they arrive.
It said steps will be taken to double-check that the workers are wearing the devices on the premises.