By Staci Matlock, The Santa Fe New Mexican
An absorbent material similar to kitty litter is the likely cause of a radiation leak that shut down the nation’s only underground nuclear waste repository near Carlsbad three months ago, according to a longtime nuclear expert.
A company in charge of packing radioactive contaminated materials at Los Alamos National Laboratory in containers for shipment to the Waste Isolation Pilot Plant switched from using a clay-based absorbent in the drums to a wheat-based absorbent — both made of the same materials used in different types of kitty litter, according to Jim Conca, a geochemist who worked for years at the lab and in environmental monitoring for WIPP.
The absorbent soaks up any liquids in the containers and remains as part of the mix that is shipped to WIPP.
The kitty litter switch could have created dried-out nitrate salts and led to a “mild” explosion in one or more of the waste containers, Conca said. “I think it is the most likely cause, but there is still some room for doubt until they get to the drum that leaked,” said Conca, senior scientist with UFA Ventures and science columnist for Forbes.
Officials at LANL, the, Department of Energy and WIPP did not specifically comment on the theory.
Meanwhile, federal officials say it could be up to three years before WIPP is reopened. Conca believes that is an ill-advised decision if indeed the wrong kind of absorbent in a LANL container set off a reaction that caused the leak. The fault then wouldn’t lie with WIPP, he noted. “This was probably a stupid mistake by someone who didn’t understand the chemistry of cat litter,” he said. “Trying to be green doesn’t excuse not talking to a nuclear chemist before you make that decision.”
Conca said it is “an awfully good thing this drum was in WIPP when it went off because if had been anywhere else, just think about what might have happened. So they need to act quickly, they need to corral all these drums and get them into WIPP right away, put them in Panel 7 and seal it off.”
Investigators looking into the Feb. 14 leak that shut down WIPP have so far ruled out a roof collapse or a roof bolt puncturing a waste container in the deep salt cavern room called Panel 7, where air monitors detected radiation. Investigators saw several large bags of magnesium oxide in Panel 7 had been damaged and moved. The bags are placed on top of waste containers to prevent radiation leaks.
Investigators are focused now on containers from one Los Alamos National Laboratory waste stream stored in the panel, along with radioactive waste from Savannah River and Idaho.
“To maintain the Energy Department’s commitment to the protection of workers, residents, and the environment, we are evaluating all possible causes including the waste packages themselves to identify the cause of the Feb. 14 event,” said a statement issued Friday by the agency. “All possible scenarios will be thoroughly investigated until the cause of the event has been determined.”
The lab, under a looming June 30 deadline from the state to remove all the old lab tools, coats debris and other waste contaminated during decades of nuclear research, had started shipping the waste containers to a Texas facility. Those shipments have stopped until federal investigators can determine if the LANL containers were the source of the leak.
Charlie McMillan, LANL’s director, said during a media gathering Thursday, “The delays in being able to get things into WIPP, and now being able to get things to Waste Control Specialists [in Texas, are very much a cause for concern, and I’m working very closely with the team. We have a very aggressive schedule, and to get everything off the site is certainly the goal, but it’s too early to tell.”
EnergySolutions, the Salt Lake City company hired to excavate, package and characterize the transuranic waste at LANL for shipment, did not return a call or email seeking comment.
Nuclear Waste Partnership also helps characterize and inspect containers from the nuclear sites before storage.
Conca is a nuclear power advocate and a WIPP believer, so he’s hoping his kitty litter theory proves correct.
The materials in kitty litter have long been used to clean up chemical spills, he said. For years, nuclear scientists relied on clay-based absorbents to soak up liquids used to clean lab tools, for example. The silicate minerals in the clay bonded and stabilized ammonia nitrates and other liquids, Conca said.
The organic absorbents made of wheat or corn don’t do that, he said. “It absorbs like a sponge. If you let the salts dry out completely, they can ignite.”
It would take a high concentration of the nitrate salts to cause a reaction. Likely the problem was in one drum, he said.
Packing a container with the wrong absorbent wouldn’t be visible to an inspector looking at the outside of the drum, and a chemical test of gases in the headspace at the top of the container wouldn’t have caught the problem either, Conca said.
Still, he said, “it is incredibly important to act quickly. You don’t want to wait months and let the drums keep drying out. They need to be gathered quickly and get them to WIPP. By being stupid, we risk doing this wrong and making it worse.”
Contact Staci Matlock at email@example.com.