Arizona Public Service finds leak and shuts nuke

Arizona Public Service shut the 1,270 megawatt Palo Verde 3 nuclear unit in Arizona after finding a coolant system leak, the company told the Nuclear Regulatory Commission in an event report on Monday. The Palo Verde station is located in Wicksburg, Arizona, about 50 miles west of Phoenix. Unit 3 produces about enough power for 1 million homes. A spokesman for the utility, a unit of Pinnacle West Capital Corp. stressed "very strenuously" that the leak was not near the reactor vessel's lid. Boric acid residue was found outside of the reactor coolant system during an inspection made Sunday, More than two years ago, the Davis-Besse nuclear plant in Ohio was shut after leaking boric acid was found to have chewed holes nearly all the way through the reactor vessel's carbon steel lid, a serious safety violation.

The plant remains offline with no restart date yet set. "They found it at an early stage. The good news is that because of Davis-Besse, plants like Palo Verde are looking more broadly. The bad news is that it is supposed to be caught before it leaks to the outside," said David Lochbaum, nuclear safety engineer at the Union of Concerned Scientists, an environmental advocacy group. The company said the event "did not result in the release of radioactivity to the environment and did not adversely affect the safe operation of the plant or health and safety of the public." "There does not appear to be residue running down the outside of the sleeve.

There were no signs of dripping, spraying, puddles of liquid, or liquid running down the nozzle or pressurizer. The residue appeared dry," the company added. No estimate was available for when the unit was likely to return to service. Lochbaum said the location of the leak means it should be easier to repair than the South Texas nuclear plant, which was shut for more than four months last year after boric acid deposits were found on the bottom of the reactor vessel. "That (South Texas) was a pretty tricky fix. I don't think it (the Palo Verde repair) will take that long," he said. On Friday, the unit was operating at 99 percent of capacity.