Actually, they were following instructions. There were a few articles shortly after the incident that said that LANL had updated their procedures documentation, and somehow the LANL documentation specified 'organic' instead of 'inorganic':
A typographical error in a revision to a LANL policy manual for repackaging waste led to a wholesale shift from clay litter to the wheat-based variety.
The revision, approved by LANL, took effect Aug. 1, 2012, mere days after the governor's celebratory visit to Los Alamos, and explicitly directed waste packagers at the lab to "ENSURE an organic absorbent (kitty litter) is added to the waste" when packaging drums of nitrate salt.
"Does it seem strange that the procedure was revised to specifically require organic kitty litter to process nitrate salt drums?" Freeman, Nuclear Waste Partnership's chief nuclear engineer at WIPP, asked a colleague in a May 28 email.
Freeman went on to echo some of the possible reasons for the change bandied about in earlier emails, such as the off-putting dust or perfumed scents characteristic of clay litter. But his colleague, Mark Pearcy, a member of the team that reviews waste to ensure it is acceptable to be stored at WIPP, offered a surprising explanation.
"General consensus is that the 'organic' designation was a typo that wasn't caught," he wrote, implying that the directions should have called for inorganic litter.
Officials at LANL declined to comment about whether a typographical error led to the switch to organic kitty litter.