The leak of radioactive material that contaminated groundwater beneath the San Onofre nuclear power plant has not reached a drinking-water source in San Clemente, according to test results announced Tuesday. City officials shut down the drinking-water well last week as a precaution after learning that cancer-causing tritium had been detected two miles away, beneath the San Onofre Nuclear Generating Station in northwest San Diego County. "The news is good: The test results came in this morning, and there is no tritium in the well," said David N. Lund, San Clementes public works director.Tritium, an isotope of hydrogen, occurs naturally in the environment but is also a byproduct of nuclear fission.

The city gets 3% of its potable water from that well. Much of it is used to irrigate San Clementes city golf course, but some supplies drinking water to homes in the southernmost part of town, Lund said. The city gets the rest of its water from the Colorado River and Northern California. City officials want to learn more about the areas geology and hydrology and its relation to the groundwater beneath San Onofre before putting the well back into service, Lund said. It was unknown how long the work would take.

Sandwiched between Camp Pendleton and the Pacific Ocean, San Onofre is the larger of Californias two nuclear power plants and can generate 2,200 megawatts, enough power to serve 2.75 million households throughout Southern California. The plant is operated by Southern California Edison and houses two working reactors. A third, 450-megawatt reactor was shut down in 1992 and is being dismantled.

Plant spokesman Ray Golden, who had previously said there was no evidence that the tritium had left the site, said Edison was happy to hear the water testing results. "We will continue to be monitoring here on the site," he said. The contamination was discovered this month when workers were dismantling the containment dome that housed the inactive reactor.

They discovered that groundwater beneath the reactor complex was tainted with 50,000 to 330,000 picocuries of tritium per liter. The U.S. Environmental Protection Agencys drinking-water safety limit for tritium is 20,000 picocuries per liter. California has recommended a "public health goal" of no more than 400 picocuries per liter of drinking water, a level that state environmental officials determined could still cause one cancer case per million people exposed.

Leaks of tritium, which can cause cancer, miscarriages and birth defects, are increasingly stoking fears in communities near nuclear plants. A tritium leak that contaminated millions of gallons of groundwater near the Braidwood Nuclear Generating Station in northeast Illinois led that state to sue the plants owner in March. San Onofre has extracted more than 10,000 gallons of the contaminated groundwater and piped it about 8,600 feet offshore, where plant officials said it was being diluted in seawater.

Because groundwater will continue to seep into the contaminated area, the plant will keep discharging contaminated water into the ocean. After the containment dome is dismantled, workers will excavate the contaminated soil and send it to a nuclear-waste disposal facility, Golden said. It was unknown how much tritium seeped into the ground, where it came from, or how long the leak lasted, Golden said. It was likely that it leaked from the reactor, the spent-fuel pool, various water storage tanks or pipes sometime between 1968 and 2004, he said.
(By Seema Mehta, Los Angeles Times, 23/08/2006)
http://www.latimes.com/news/science/environment/la-me-onofre23aug23,1,5443248.story?track=rss