Workers’ Radiation Dose Registration Center

The Workers’ Radiation Dose Registration Center is the institution that registers workers in the nuclear industry and issues their Radiation Dose Management Booklets. In the investigation, its records offer a rare route from years of subcontracted, sometimes falsely named work to concrete identity and employment information. The Center’s role also exposes a tension at the heart of the case: hazardous work generates official records, but those records do not necessarily capture everyone who performs it.

Registration and Records

Workers in radiation-controlled areas were required to register with the Center. Registration brought an individual a Radiation Dose Management Booklet, which workers had to present to employers when seeking a job. The booklet recorded radiation exposure, making it both a work credential and a record of occupational risk.

The Center’s files could preserve details useful beyond radiation tracking. When investigators identified Kazutoshi Yokoyama in its records, they learned that his address and legal domicile had been in Nagoya. His current residence certification had been deleted without any recorded notification of a move, however, so the file established a past identity and location without revealing where he was now.

Use in the Investigation

The task force searched for Shunichi Watabe and Mutsuo Koshikawa, whose names might have been false identities used for nuclear-plant work. Investigators confirmed that neither name appeared in the Center’s records. That absence did not conclusively rule out employment: a person could have worked at a nuclear plant without entering a radiation-controlled area, although an industry expert considered this unlikely because such work was commonly understood as a way to earn substantially more money.

A lead from Hamaoka Nuclear Power Station offered a possible way forward. If the name supplied by the contact appeared in the records, investigators expected to obtain an address, registered domicile, work history, and radiation dosage information—enough to help locate the person and assess whether he matched the man they sought. The Center therefore served not simply as a repository of exposure data but as a potential bridge between a sketch, a worker’s employment past, and an identifiable person.

Limits and Wider Significance

The records’ usefulness was bounded by the structure of the work. Nuclear maintenance was often organized through long chains of contractors and subcontractors, with small firms supplying workers far down the chain. After the 2011 earthquake and tsunami, many of those smaller companies withdrew from the business, further complicating efforts to trace old employment. Companies were required to retain employee documents for three years for full-time workers, but that requirement did not apply in the same way to short-term workers.

The novel contrasts the Center’s formal registration system with this fragmented labor market. Workers could move between temporary dormitories and plants, while subcontracting obscured which company had employed whom; false names and forged residence cards were described as routine possibilities. Against that background, the Center’s records are valuable precisely because so much of the employment trail is difficult to reconstruct. Yet they are not a complete map of the workforce: the absence of a name from the files narrows the inquiry without settling it, and a booklet can document exposure and employment without resolving the identity concealed behind them.