Nuclear power industry radiation registration and dose record manual regulations

The nuclear industry’s registration and dose-record system links access to work with an official booklet documenting radiation exposure. In the investigation, that system offers a possible trail to workers living under unstable or assumed identities, yet its limits reflect the same fragmented labor structure that makes the trail difficult to follow.

Registration and the dose booklet

Workers registered with the Workers’ Radiation Dose Registration Center were automatically issued a Radiation Dose Management Booklet. They had to present it to an employer as part of getting a job. The booklet therefore served both as a record of exposure and as a credential within the hiring process: it connected a worker to registration while carrying information relevant to subsequent employment.

The booklet’s evidentiary value was not the same as proof of a person’s true identity. A crew leader recalled that he would have recognized a fake and would not have hired anyone suspicious, but his memory was uncertain, and investigators concluded that the booklet alone could not establish that Kazutoshi Yokoyama was who he claimed to be. The case had already shown that, in the industry, identity checks could be loose enough for a forged residence certificate to result in a booklet being issued to someone under eighteen.

Work, exposure, and fragmented employment

The records mattered because workers could move frequently between plants and employers. One worker described nuclear-plant labor as resembling day labor in construction: subcontractors and smaller sub-subcontractors recruited people with varied personal circumstances, provided temporary dormitories, and sent them from one plant to another after a few months. He had worked that way for four years. A booklet could travel through this unstable working life as a portable record, even when a worker had no enduring home or employer.

The work itself made radiation exposure central to the system. A worker explained that inspections and maintenance involved cleaning contaminated areas, using cloths and brushes to remove radiation. An industry expert told investigators that radiation-controlled work was a route to higher earnings than other available work, while much of the money could be taken by intermediaries. The system thus recorded exposure within a labor market in which workers moved through contractor chains, undertook hazardous tasks, and did not necessarily deal directly with the companies ultimately responsible for the work.

Limits of the records

Investigators found that old employment records were scarce. Companies were required to retain employee documents for three years only for full-time workers; that rule did not cover short-term employees, a common arrangement in an industry organized through contractors and subcontractors. Forged residence cards and employment under false names were described as routine. Even if Shunichi Watabe had worked under that name, the task force could not assume that a search of ordinary employment records would find him.

The same uncertainty applied to registration. Investigators confirmed that neither Shunichi Watabe nor Mutsuo Koshikawa appeared in the records for radiation-controlled work at one plant. That absence did not rule out employment at a nuclear power station under either name if the work did not involve a controlled area. An expert considered that unlikely, because workers seeking the industry’s better-paid jobs generally accepted radiation exposure, but the distinction prevented a missing registration entry from functioning as conclusive evidence.

Investigative use and narrative significance

A tip from the Hamaoka Nuclear Plant suggested that someone might recognize a sketch of the man investigators were seeking. If the name supplied with the tip appeared in the relevant records, the task force expected to obtain an address, registered domicile, work history, and radiation dosage—information that could help locate the person and assess whether he was their target. The booklet and registration system therefore promised a practical route from work history to identity, even though the investigation had already established reasons to distrust any single name or document.

That promise was especially consequential in the story of Tadao Asai’s hidden life. A man working at nuclear plants under the name Kazutoshi Yokoyama described temporary company dormitories and showed Tadao a Radiation Dose Management Booklet bearing that name. Later, Tadao’s letter to Hiromi Asai used the same assumed identity and explained that he was working at a nuclear plant in Fukushima Prefecture cleaning up radiation. The administrative record that investigators treat as a possible means of tracing a worker is also part of the machinery through which Tadao sustains concealment. The rule is thus both a record of exposure and a fragile link between a person, a job, and a name.