In conditions this dangerous, wanting to help and being allowed to help are different things. Some lawmakers initially scoffed at the volunteers, including Goshi Hosono, an aide to Prime Minister Naoto Kan, who told reporters last month that the work in Fukushima did not yet require a “suicide corps.”

“It is very precious that they sacrifice their lives and volunteer to resolve this situation,” Mr. Hosono later explained. But “they are at a certain age, so we don’t want them to get sick after working in such a dangerous environment with full face masks.”

But in a country starved for feel-good stories, the Skilled Veterans Corps has captured the hearts of many. Requests for interviews have poured in from around the world. Politicians have slowly come on board. On June 6, Mr. Yamada met Banri Kaieda, the minister of economy, trade and industry, who promised to help the volunteers before their “enthusiasm burns out.”

“I thought, what a brave idea when so many Japanese and non-Japanese are afraid to go to Fukushima,” said Hiroe Makiyama, a Parliament member in Mr. Kan’s Democratic Party of Japan who is helping promote the project. “No one intends to die there. They don’t really want to do this, but they feel they have to do this.”

Mr. Yamada got so busy working from home that he found some office space in a narrow walk-up in Tokyo’s Shimbashi neighborhood. In a spartan room with a couple of computers, a hot water pot and a few folding chairs, Mr. Yamada and his team are applying to become a nonprofit group and awaiting approval of their application to visit the Daiichi plant in July.

Mr. Yamada and Mr. Shiotani say the hardest part of their jobs may be dealing with officials at Tokyo Electric Power, or Tepco, as it is known. As engineers, they understand that their counterparts, who undoubtedly are very busy, likely will have bruised egos, given the scale of the damage and the tumbling status of the company.