The story was on May 13, 2014 on Reuters, before the latest update from the US Department of Energy on May 16, 2014.
It fondly reminded me of TEPCO's use of bath salt (as tracer) and shredded newspaper and baby diaper polymer to plug the leak at the water intake for Reactor 2 back in April 2011.
From Reuters (5/13/2014; emphasis is mine):
Kitty litter eyed as possible culprit in New Mexico radiation leak
Kitty litter used to absorb liquid in radioactive debris may have triggered a chemical reaction that caused a radiation leak at a below-ground U.S. nuclear waste storage site in New Mexico, a state environmental official said on Tuesday.
The waste disposal site, where drums of plutonium-tainted refuse from nuclear weapons factories and laboratories are buried in salt caverns 2,100 feet (640 meters) underground, has been shut down since unsafe radiation levels were first detected there on Feb. 14.
The leak of radiation, a small amount of which escaped to the surface and exposed 21 workers at the Waste Isolation Pilot Plant, ranks as the worst accident at the facility and one of the few blemishes on its safety record since it opened in 1999.
Investigations of the chamber where the leak occurred suggest a chemical reaction may have generated sufficient heat to melt seals on drums and boxes of contaminated sludge from the Los Alamos Nuclear Laboratory, releasing radioisotopes such as plutonium, Energy Department officials have said.
Jim Blankenhorn, deputy manager with the contractor running WIPP, told a public meeting last week that a change in the materials used at Los Alamos to package waste may have triggered a reaction between nitrate salts and organic matter.
“Kitty litter is in the field of theories,” Jill Turner, spokeswoman for the New Mexico Environment Department, said about a possible cause for the accident.
Kitty litter is used as an absorbent for liquid contained in radiological debris destined for WIPP, which does not accept fluid waste, Turner said.
Los Alamos, a leading U.S. nuclear weapons lab, and the WIPP contractor, Nuclear Waste Partnership, did not immediately respond to requests for comment on Tuesday.
Dozens of drums of waste from Los Alamos that have been linked to the radiation accident are deposited in two separate waste disposal chambers at WIPP, managers have said.
The plant last week suspended shipments of that waste to a Texas-based commercial storage facility, which had received 25 drums between April 1 and May 1, said WIPP spokesman Brad Bugger.
The plant in the Chihuahuan Desert in southeastern New Mexico provides for permanent disposal of contaminated items like clothing and equipment from U.S. nuclear laboratories and weapons sites.
It is not expected to resume operations for at least 18 months and may take as long as three years to be fully operational, managers have said.