A nuclear waste repository in New class="mandelbrot_refrag"> Mexico was ordered by the state on Tuesday to craft a plan to hasten the sealing off of underground vaults where drums of toxic, plutonium-tainted refuse from Los Alamos National Laboratory may have caused a radiation release. The directive by state Environment Secretary Ryan Flynn said the drums, buried half a mile below ground at the Waste Isolation Pilot Plant near the town of Carlsbad, "may present an imminent and substantial endangerment to health or the environment". The repository, the only facility of its kind in the United States, has been shut since Feb. 14, when unsafe radiation levels were detected there. The leak of radiation, a small amount of which escaped to the surface and exposed 22 workers at the plant, ranks as the facility's worst accident and one of the few blemishes on its safety record since it opened in 1999. Flynn ordered managers of the U.S. Energy Department facil