Diablo Canyon nuclear power plant could be affected by new rules

New state rules would require that the cooling system used at Diablo Canyon nuclear power plant be phased out within the next 15 years, but would allow plant managers to apply for alternatives that reduce cost.

The goal of the rules is to eliminate the method known as once-through cooling, which uses billions of gallons of ocean water daily to cool electrical steam generators. State water officials consider once-through cooling used by 19 coastal power plants to be too damaging to the ocean environment.

“Ultimately, once-through cooling has got to go,” said Dave Clegern, spokesman for the State Water Resources Control Board.

The rules would allow Diablo Canyon, owned by Pacific Gas and Electric Co., and a nuclear plant at San Onofre to apply for less stringent requirements to offset the damage of their cooling systems if eliminating once-through cooling is determined to be “wholly out of proportion to the cost.”

Typical alternatives to once-through cooling are the use of giant radiators or cooling towers to reduce the temperature of cooling water in a closed system. However, PG&E officials have said the cost of these could be prohibitive.

In the past, PG&E and state water officials have also considered less expensive options, including conserving undeveloped land around Diablo Canyon and constructing offshore reefs in order to create or protect fish habitat.

The Morro Bay power plant, which is antiquated and rarely operates, would have until 2016 to comply with the new rules. Diablo Canyon’s compliance deadline is 2025.

Kory Raftery, a PG&E spokesman, said the utility is still reviewing the proposed rules and has not decided how it will proceed if they are adopted, but it “supports an orderly transition from once-through cooling.” PG&E also supports allowing alternative requirements for nuclear plants, he said.

Once-through cooling has fallen out of favor with regulators because it harms the ocean environment in several ways.

In the case of Diablo Canyon, nearly 2.3 billion gallons of seawater are circulated through the cooling system each day. Many, if not all, of the larvae carried in the waster are killed by the 20-degree temperature increase or are eaten by barnacles and other crustaceans that line the cooling water pipes. The heated water has also altered the marine ecology of the plant’s discharge cove.

Other once-through-cooling plants in the state have more dramatic effects. Their intake structures, unlike Diablo Canyon’s, are narrow offshore pipes that create enough suction to kill or injure fish and marine mammals.

The worst offender is the state’s other nuclear plant, San Onofre. Between 1978 and 2000, 64 harbor seals, 153 sea lions and four sea turtles were found dead in the plant’s intake structure.

Rules phasing out once-through cooling were initially proposed nearly a year ago. State water officials later revised them to give additional oversight to other state agencies, such as the Public Utilities Commission, that were concerned about reliability of the state’s electrical grid.

“We are trying to balance protecting the aquatic environment with people’s need for energy,” Clegern said. “We don’t want the lights to go out.”

The proposed policies also contain language that recognizes the importance of Diablo Canyon and San Onofre in meeting the state’s goals to significantly reduce greenhouse gas emissions. The two nuclear plants provide about 20 percent of the state’s power and have applied to federal regulators to extend their operating licenses by 20 years.

It will be up to each utility to decide which technology it will use to replace once-through cooling, Clegern said. Owners of older plants, such as Morro Bay, may decide to shut them down.

Comments on the proposed rules will be accepted until April 13. The agency will hold a hearing and could adopt them May 4.

Reach David Sneed at 781-7930.