Tepco defended its worker training, which "includes basic knowledge of protection against radiation, such as how to manage radiation doses or how to put on and take off protective suits and other equipment," said Mayumi Yoshida, who works in the utility's corporate communications office.
But nuclear experts point to what they call a lax safety culture that downplays the risk of radiation exposure.
"What's troubling is that both the utilities and the government are saying there isn't a problem, while we know the doses these workers are being subjected to [are] quite high," said Kristin Shrader-Frechette, a professor of radiobiology and philosophy at Notre Dame University.
After the Fukushima disaster, the government raised the annual limit for allowable radiation exposure from 200 millisieverts to 250 for nuclear plant workers, Shrader-Frechette said.
Meanwhile, the United Nations Scientific Committee on the Effects of Atomic Radiation has warned that exposure to just 30 millisieverts a year can cause cancer. "The government is allowing workers to receive more than seven times that amount," she said.
Tepco says it monitors radiation absorption rates among workers, who are not allowed to exceed government-set limits.
Since the start of Japan's nuclear boom in the 1970s, utilities have relied on temporary workers for maintenance and plant repair jobs, while providing little follow-up health training, activists say.
"Typically, these workers are only told of the dose they get from an individual or daily exposure, not the cumulative dose over the time they work at a particular plant," said Shrader-Frechette. "As they move from job to job, nobody is asking questions about their repeated high doses at different sites. We're calling for a nuclear dosage tracking system in Japan and other nations."
Activists say utilities rely on a network of contractors, subcontractors and sub-subcontractors to supply those who work for short periods, absorb a maximum of radiation and are then let go.
Hiroyuki Watanabe, a city councilman in Iwaki, just south of the Fukushima plant, said past medical tests on plant contractors who had become sick did not produce a definite link to radiation exposure. Still, he thinks the utilities should be more forthright about the dangers such workers face.
"It's wrong to prey on the poor who need to feed their families," he said. "They're considered disposable, and that's immoral."
No matter what people called him, Okawa is proud of the work he performed for his nation's nuclear industry. He labored among teams of men who every day faced incredible risks without complaint.
Yet his scariest work had nothing to do with radioactive exposure. "I stood atop a building once, seeing the danger with my own eyes," Okawa said. "That's the way many guys felt about radioactivity: You had to see the danger to fear it. We never saw it."