LOS ALAMOS, N.M. (AP) — Workers at the Los Alamos National Laboratory in northern New Mexico have started treating 60 drums of remediated nitrate salts. They plan to treat about one drum per day and have the job completed this summer. The drums contain an incompatible combination of nitrate salt waste mixed with an organic absorbent added during repackaging to absorb liquids and neutralize the combustible characteristic of the salts. The drums need to be treated to be safely disposed of at southern New Mexico's Waste Isolation Pilot Plant, the nation's only underground nuclear repository. The Carlsbad plant was forced to close in February 2014 after an improperly packed drum of waste from Los Alamos ruptured and caused a radiation release. Shipments of waste only recently began making their way to the plant for disposal.