Many of these lawmakers, both Democrats and Republicans, have received significant campaign contributions from the industry. For instance, Mr. Barrow’s top contributor in the 2012 election was the Southern Company, a Georgia-based utility that is a major player in nuclear power. Some of the lawmakers also have nuclear reactors in their districts, a major source of tax revenue and jobs.

The appointment books for certain commission members, reviewed by The New York Times, show frequent meetings with the industry, including private sessions at the commission’s headquarters. Nuclear industry opponents occasionally have had their own private meetings, but not nearly as often, the records show.

E-mails obtained by The Times also demonstrate the teamlike approach taken by the industry and the regulators in dealing with safety questions, as they have worked behind the scenes with the Nuclear Energy Institute, the leading trade association, to try to prevent a reaction against nuclear power in the aftermath of the Fukushima accident.

“It would be nice if the industry was even more proactive by having N.E.I. send us a letter that says something to the effect that in the wake of the Japanese disaster here is a list of all the things the commercial U.S. nuclear licensees are doing,” wrote Brian Sheron, the head of nuclear regulatory research at the regulatory commission, in an e-mail to his colleagues, referring to the Nuclear Energy Institute.

Mr. Sheron, in a statement, said he was prodding the industry, not trying to protect it, as he realizes the “industry never seems to want to aggressively get out in front of issues.” Since the accident in Japan, American regulators have imposed several mandates on the industry but none are likely to cost the industry much money, industry officials said.

The filtered vent proposal, by far the most expensive, would be required only on boiling water reactors like Nine Mile Point, which are considered much more prone to leaking during an accident because they have unusually small primary containment chambers and pressure can build quickly.

But how well the filters work is unclear because the vents to which they would be attached have never been used successfully in an accident at a modern commercial reactor, experts said. The vents failed at Fukushima, which would have rendered filters moot. A panel of independent senior advisers to the commission opposes a strict requirement for filters.