AIKEN - The federal government is moving forward with plans to construct a new plutonium weapons facility - possibly at Savannah River Site - despite a recent study that suggests the highly radioactive material is lasting longer than some scientists had thought it would, officials said Monday.

The study, produced by the Lawrence Livermore and Los Alamos National Laboratories and released last week, found that plutonium in most of the country's nuclear weapons has a minimum lifetime of between 85 and 100 years, almost twice as long as the government previously thought.

The findings, however, do not alter the National Nuclear Security Administration's plans to build a Consolidated Plutonium Center.

The facility could produce 125 plutonium pits - softball-size spheres used to detonate nuclear weapons - every year, starting in 2022, officials have said.

The agency won't select its site until 2008, but officials already estimate that the facility would cost between $200 million and $300 million annually to operate and create at least 1,000 jobs.

If SRS is selected, it would also mean that an untold amount of the potentially destructive material would be shipped to the site on top of 34 tons of plutonium that already is to be shipped there for conversion into fuel for nuclear power plants.

The agency isn't changing plans for several reasons, said spokeswoman Julianne Smith, including the increased safety that comes with storing all of the nation's weapons-usable plutonium in one place, the need for additional research and development and the lack of a facility that can manufacture plutonium for weapons on a large-scale basis.

"We are the only nuclear superpower without the capability to produce pits at this level," she said.

Los Alamos, one of the site's being considered for the proposed center, can currently make between 30 and 50 pits, but that is on an interim basis, Ms. Smith said.

Critics, who have long asked the government for proof that aging plutonium needed to be replaced, say that the study proves that it doesn't.

"This indicates that there will not be aging-related concerns with the plutonium pits," said Arjun Makhijani, president of the Institute for Energy and Environmental Research. "So, from the nuclear side of the business, there's absolutely no need to make new pits. We'll be creating more problems for nothing."