ALBUQUERQUE, N.M. (AP) -- Four days after a radiation alert shut the nation's only underground nuclear waste repository, an independent monitoring center said Wednesday it found radioactive isotopes in an air sensor about a half mile from the southeastern New Mexico plant.
A filter from a monitor northwest of the Waste Isolation Pilot Plant in Carlsbad had trace amounts of americium and plutonium, said Russell Hardy, director of the Carlsbad Environmental Monitoring and Research Center.
The levels are the highest ever detected at or around the site, but are far below those deemed unsafe by the Environmental Protection Agency, he said.
The readings come on the heels of a radiation alert that closed the plant to all non-essential personnel last weekend after an underground sensor detected airborne radiation. Department of Energy officials say most operations remain closed, but they have not released any further information.
Two weeks earlier, a truck hauling salt in an underground mine at the site caught fire, shuttering operations for a few days. Officials said that fire was in an area separate from where nuclear waste is stored. In both instances the DOE has said public safety has not been threatened.
Hardy said his center, an arm of New Mexico State University that monitors air, ground and water samples from in and around WIPP, didn't get the filters from the underground radiation sensor that was activated Saturday until Tuesday. He said he expects to have readings from that and an air sampling station closer to the plant next week.
He did note, that a second air sampling station 11 miles from the plant showed no radioactive particles.
Hardy said the center gets filters every day from sampling stations, and there have only been four incidences in the past in which radiation was detected. All were so low that "you could eat it and it wouldn't hurt you."
The Waste Isolation Pilot Plant is the nation's first and only deep geological nuclear repository. It takes plutonium-contaminated waste from Los Alamos National Laboratory and other defense projects, and buries it in rooms cut from underground salt beds.
Copyright 2014 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.