MONTPELIER, Vt.—A new leak at the Vermont Yankee nuclear plant -- this one from a valve in an emergency cooling system -- briefly put it on the path to a required shutdown before it was fixed early Wednesday, officials said.
Plant and federal Nuclear Regulatory Commission officials said there was no direct threat to the public health and safety, but that safety margins were reduced enough that the plant would have been required to shut down within 24 hours if it were unable to replace the valve.
The valve was in the main reactor building, outside the primary reactor containment. It was found Tuesday morning to be leaking 1.6 gallons of radioactive water per minute, 60 percent more than the allowable limit of 1 gallon per minute, plant officials said. The water was being collected in a drain system and did not get into the outside environment.
The plant had a replacement valve in stock, and plant technicians replaced the faulty one within five hours, Vermont Yankee spokesman Larry Smith said.
Calculations have shown that under worst-case-scenario accident conditions, radiation levels in the main reactor building would rise too high with a valve leak that big, said Donald Jackson, a project branch chief with the NRC's Northeast regional office.
Jackson said the water that leaked contained "very, very small amounts" of radioactivity -- less than was contained in water found leaking from a pipe May 29.
That older leak contained 13 different radioactive isotopes, some of them with half lives short enough to indicate it had been through the reactor a short time before, officials have said.
The new leak was of water that the plant was keeping in an emergency cooling system; it is not believed to have been through the reactor in several weeks, Jackson said.
The 38-year-old reactor in Vernon, in Vermont's southeast corner, has been plagued by leaks recently. In January, it was announced that radioactive tritium, which can cause cancer when ingested in large amounts, had turned up in a monitoring well on the plant grounds. Follow-up tests found other radioactive substances as well.
The May 29 leak was found in the same area -- an alley between two plant buildings -- where plant officials had dug a trench to find the source of the leaking tritium.
The plant, owned by New Orleans-based 
