The triple meltdown at the Fukushima Daiichi nuclear plant in March startled many people in the American nuclear industry, the chairman of the Nuclear Regulatory Commission said on Tuesday, although the success in ultimately gaining control of the reactors did not.

“I think there are many people who are associated with this industry who believed we had designed away, or operated in a way, that eliminated the possibility of ever having a significant, really severe accident,’’ said the chairman, Gregory B. Jaczko, who held a year-end roundtable session with reporters.

That it was possible for the three reactors to melt down without causing any immediate deaths was far less surprising, he said. “Plants ultimately have a number of safety features and designs to reduce the likelihood” of releasing enough radiation to cause immediate illness, he said.

Still, the damage wrought by relocating thousands of people from their homes for extended periods was incalculable, he added.

In a wide-ranging discussion, Mr. Jaczko said that applying the lessons of Fukushima to American reactors was taking up so much of the Nuclear Regulatory Commission’s time that it may have to slow down on some other work, like processing applications for license renewals and for permission to produce more power.

“The practical realities are there are resource limitations and some decisions will have to be made,’’ he said. One big challenge for the agency, he said, is that its budgets are likely to be flat for years to come.

Mr. Jazcko said he was concerned about some minor human errors at operating reactors in the United States that could signal “possible declines in performance.’’ At two plants, Perry in Ohio and Cooper in Missouri, poor planning or poor adherence to procedure led to a situation where employees encountered unexpectedly high levels of radiation and avoided significant exposures only because their monitoring equipment sounded an alarm, he said.

For a time this year, three reactors were shut down at the same time for extended periods, he pointed out, the first time in years that the number has been so high. The Crystal River reactor, near Tampa, Fla., has been shut since 2009, first for maintenance and then because of problems with its containment building; the Fort Calhoun reactor near Omaha had performance problems and had difficulty coping with the rising water of the Missouri River last spring, and North Anna in Mineral, Va., was closed for weeks for damage assessment after the earthquake there in August. (The damage was eventually found to be minor.)

The commission chairman also defended his role in shutting down research work on the suitability of Yucca Mountain as a nuclear waste repository. Some members of the commission and its staff told the agency’s inspector general that they believed he had acted in a peremptory manner.

Mr. Jaczko said he believed that the commission had ended its work appropriately and in a “professional” and “methodical” way.

Nuclear waste is not a pressing issue, he said. “Fundamentally, when I look at spent fuel, the issues that are out there for spent fuel are manageable issues for at least the next 100 years’’ and possibly much longer, through storage in dry casks or spent fuel pools, Mr. Jaczko said.

(Source: www.nytimes.com )