Allison Macfarlane, chairwoman of the Nuclear Regulatory Commission, was in San Luis Obispo on Tuesday to tour Diablo Canyon nuclear power plant and meet with local elected officials, plant managers and community activists.

This was Macfarlane’s first visit to Diablo Canyon since being appointed chairwoman by President Barack Obama in July. On Monday, she toured the troubled San Onofre Nuclear Generating Station in Southern California, which is idled because of problems with its steam generators.

Macfarlane is a geologist and an expert on nuclear waste, two issues of intense interest at Diablo Canyon. In an interview with The Tribune, Macfarlane said she discussed seismic safety issues with plant managers but did not go into detail.

Earthquakes are just one of many natural hazards nuclear plants must be prepared for, she said. Others include tornadoes, flooding, drought and tsunamis.

“There are a lot of earth processes that need to be taken into account, and we are constantly reviewing them,” she said. “They are constantly evolving.”

She deflected several questions about the impact of the state Coastal Commission’s denial of PG&E permits to conduct high-energy seismic surveys off the coast of Diablo Canyon.

“It’s nothing we required. That was not us; that was you guys,” she said referring to state public utilities officials who wanted the surveys done.

She noted that the high-energy surveys are only one part of PG&E investigations into the earthquake faults surrounding the plant. Others include low-energy offshore surveys as well as three-dimensional and two-dimensional land-based surveys.

The NRC did require that all nuclear plants in the country review their earthquake readiness in the aftermath of the March 2011 nuclear disaster at the Fukushima Dai-ichi plant in Japan. Macfarlane recently toured the Fukushima area and was struck by the empty villages evacuated as a result of radiation releases.

“That is the kind of disaster we don’t want to have here,” she said. “It means that we need to be careful and integrate lessons learned.”

The NRC has already issued a series of new requirements for plants as a result of the Fukushima disaster. The main one is that plants must add more and redundant equipment, such as diesel generators and pumps, which will allow them to continue to cool their reactors in the event of a complete loss of power, preventing a catastrophic core meltdown.

“These changes will take time, but the NRC has been quick to respond,” she said.

Before being named to the commission, Macfarlane served on the Blue Ribbon Commission on America’s Nuclear Future, a panel convened by Obama to examine options for storing the nation’s high-level nuclear waste now that the administration has rejected plans to store the waste at Yucca Mountain in the desert of Nevada.

Speaking as a former member of the Blue Ribbon Commission and not chairwoman of the NRC, Macfarlane said one or more geologic or underground repositories for the spent fuel are possible. She referred questions about timelines and other details to the White House.

“The NRC does not make policy,” she said. “We license facilities.”

Macfarlane’s visit to Diablo Canyon was the first visit by an NRC chairman to the plant since 2005. She described the visit as “a good tour.” She was struck by the isolation of the plant and the fact that it is confined to a narrow strip of land between the ocean and the Irish Hills rising in back of the plant.

“It’s interesting to see these plants and their different layouts,” she said.

Regarding the future of the San Onofre plant, NRC regulators will not allow the reactors to restart until they are convinced the plant is safe, she said. That plant was shut down a year ago because its steam generators showed premature wear that resulted in the release of a small amount of radioactive steam.