By Eric M. Johnson
SEATTLE (Reuters) - A storage tank holding radioactive waste at a decommissioned nuclear weapons site in Washington state may be leaking but poses no immediate threat to public safety, state and federal officials said on Friday.
The underground tank is one of 28 double-walled containers into which waste from older, single-shell tanks was pumped during a decades-long cleanup at Hanford Nuclear Reservation, according to Lori Gamache, a U.S. Energy Department spokeswoman.
In October, officials determined waste was leaking in the primary tank but had not breached its outer shell. Then on Thursday, workers found increased radioactivity levels in pumps used to remove water and sediment from the tank's "leak detection pit," Gamache said.
News of the possible leak comes the same week Ernest Moniz made his first visit as U.S. Energy Secretary to the 586-square-mile (1,518-square-km) site along the Columbia River, established in 1943 as part of the Manhattan Project, the U.S. government program that developed the first atomic bombs.
Production of weapons-grade plutonium there resulted in more than 43 million cubic yards of radioactive waste and 130 million cubic yards of contaminated soil and debris.
As part of the cleanup - projected to cost nearly $115 billion by the end of the century - as much remaining liquid waste as possible was pumped out of older single-shell tanks into sturdier double-walled tanks in a process completed in 2005.
In all, there are 177 tanks holding some 56 million gallons of waste, 149 of which are single-shell. Six of those tanks were discovered in February to be leaking at a rate of about 1,000 gallons annually. The double-shelled tanks were thought to be safe.
Washington state Governor Jay Inslee described the news as disturbing.
"I continue to have serious concerns regarding the pace of addressing the leaking tanks," Inslee said in a statement.
(Editing by Cynthia Johnston and Lisa Shumaker)