Radioactive kitty litter may have ruined our best hope to store nuclear waste

Radioactive kitty litter may have ruined our best hope to store nuclear waste

Some of the most dangerous nuclear waste in the US is currently scattered between 77 locations all over the country, awaiting permanent storage. Until February, many experts suggested that the best place to put it was a facility about 40 miles east of Carlsbad, New Mexico, called the Waste Isolation Pilot Plant (WIPP). For 15 years, WIPP has operated as the first and only permanent, deep geologic nuclear waste storage facility in the country, holding “low level” radioactive materials — mostly clothing and tools exposed to radiation from nuclear weapons production — in steel barrels more than 2,150 feet below the Earth’s surface.

But earlier this year two emergencies brought that suggestion — and WIPP’s future — into question. And now it seems kitty litter may be to blame.


WIPP is in a salt desert, and much of the work there involves burrowing through the salt and using huge elevators to deposit the stuff at surface level. The resulting underground caverns are then filled with radioactive waste and eventually closed shut, sealed forever.


In February, according to a press release from the US Department of Energy — which oversees operations at WIPP — two things happened to stall that relatively simple process.

First, on February 5th, a salt-hauling truck caught fire. That would be an inconvenience on the side of a highway, but in an enclosed salt cavern surrounded by nuclear waste, it’s a potential catastrophe. Workers evacuated the site. Fortunately no one was hurt. But the fire was significant enough to shut down underground operations until investigators could figure out what happened and how to stop it from happening again. Surface-level operations continued.

But not for long. Nine days later, late at night on Valentine’s Day, an alarm sounded, indicating that radioactivity was present in the air underground. No one was below ground at the time, but employees on the surface activated massive fans designed to ventilate the underground air. The next day, another monitor went off — this one on the surface — indicating airborne radiation. Employees who worked outside on the surface were told to take shelter inside buildings completely separated from storage operations. Valves allowing air to flow underground were sealed with high-density expanding foam. Everything came to a standstill, indefinitely.


There are no indications that anyone has been injured from the radiation leak. (All employees went through examinations for radiation exposure; a DOE press release says most workers were not affected, and those who were “received less exposure than a person receives from a chest X-ray.”) But for months, nothing has changed. The standstill remains. WIPP’s 850 or so employees are mainly sitting around, waiting (or “performing surface facilities maintenance or assisting with procedure reviews and revisions”) while investigators from the US Department of Energy (DOE), the New Mexico Environment Department and elsewhere attempt to figure out what happened.

Initially, there were two hypotheses. The first was that something had gone wrong with the supports inside the cavern where waste was being stored. If that were the case, it meant a piece of salt rock or a steel support had fallen into one of the sealed barrels, puncturing it and releasing radiation into the air.

“That was an unlikely possibility,” says Norbert T. Rempe, PhD, a retired geologist who spent decades as a principal engineer at WIPP. The cavern where the radiation monitor went off had been dug only recently, so the chances that supports had eroded or collapsed were probably slim.


Organic kitty litter likely caused a steel barrel’s seal to puncture at the Waste Isolation Pilot Plant in Carlsbad, NM. The damage and the resulting radiation leak could close the facility, experts say. (Department of Energy)

More likely, he said, was the second hypothesis: that something had gone awry inside one of the radioactive containers — that the radioactive material had become hot for some reason, expanding and puncturing a steel barrel from the inside.

Last month, DOE investigators went into the cavern. Pictures showed that the latter hypothesis was true; a waste container’s lid was unsealed, and dust around the lid had turned yellow from the unusual heat emanating from inside. Each barrel is labeled to track where it came from. The punctured barrel originated from Los Alamos National Labs.

Jim Conca, PhD, a geologist who worked for years at WIPP who now blogs at Forbes about energy issues, believes he knows what blew the lid off at least one of WIPP’s radioactive barrels. The culprit, he wrote, was kitty litter.


As Conca explains it, inorganic cat litter has properties that make it ideal for stabilizing nitrates in radioactive material — for ensuring that it doesn’t dry out and become dangerously hot. So kitty litter is often mixed in barrels with the low-level waste that’s eventually sent to WIPP. What happened at WIPP, he believes, is that one of the radioactive shipments was mixed with organic instead of inorganic material. “‘Green’ cat litter,” he writes, is “made with materials like wheat or corn. These organic litters do not have the silicate properties needed to chemically stabilize nitrate the correct way.” The result: “solutions can ignite when they dry out.”

In other words, the whole problem at WIPP — the radiation leak, the months-long stall in operations, the worries over safety — results from one person’s mess up. (Yesterday, a DOE press release confirmed that kitty litter “may have caused a chemical reaction” that lead to the leak.)

“Everything nuclear is proceduralized,” he tells The Verge. “It’s well laid out and everything everyone does is supposed to go up and down the chain of command. When you decide on a procedure for doing something like treating this waste, you don’t deviate from it. Ever. And when someone decides to deviate, that is a bad, bad thing.”

He continues: “In this case, it could shut down the most successful nuclear repository in history.”


Apart from the absurdity in a multibillion-dollar project halted by the decision to use off-brand kitty litter, the real lesson here may lie in the fragility of even the best nuclear storage facility. Corrective action at WIPP could be a massive undertaking. How many other barrels contain the dangerous organic cat litter? Are all of those barrels underground at WIPP? Are they awaiting shipment at surface level in places like Los Alamos? Or are they located at the temporary storage site in Andrews, Texas, where some containers were transferred when problems arose at WIPP?

“Expert assessment will be needed,” writes Per Peterson, a professor and researcher at UC Berkeley’s Department of Nuclear Engineering, in an email shared with The Verge, to merely “determine whether the safety benefits of stabilizing or repackaging the material in these drums are justified by the risk to personnel who would attempt to do this work.”

And if the DOE decides stabilizing or repackaging the material is unjustified, that would close WIPP for good.

“If that happened, it would be a shame and a disaster — particularly for taxpayers,” says the retired WIPP geologist Rempe. The DOE estimates the total cost of the WIPP plant to be $7.2 billion.

Even if WIPP does begin operating again, “we have no idea how long this will take until WIPP is back to normal operations, or what the new normal operations will be,” Rempe says. “No one knows right now. And it could be a long time before anyone knows.”

A typo and a bag of kitty litter might cost US taxpayers billions in nuclear waste cleanup

A typo and a bag of organic kitty litter may end up costing United States taxpayers more than $2 billion in nuclear waste cleanup, according to a new report by Ralph Vartabedian at the Los Angeles Times .

Back in February 2014, a drum of nuclear waste burst open inside the cavernous Waste Isolation Pilot Project (WIPP), which is drilled out of a salt deposit nearly half a mile below the deserts of Carlsbad, New Mexico.

The US Department of Energy (DOE), which funds the company that runs the nuclear waste dump, quickly suspended operations and launched an investigation to figure out the cause.

drum 68660 wipp doe labeled
Drum 68660, which burst in WIPP nuclear waste dump.

In their 277-page report , investigators determined the blast vaporized nearly 7.5 lbs of the material inside a single barrel, labeled ” Drum 68660 .” That material included some radioactive isotopes of americium, plutonium, and uranium — byproducts of Cold War-era nuclear weapons production.

Although no one was inside WIPP when the drum burst, the facility’s air ventilation system spread some of the gases outside, exposing 21 workers to low doses of radiation.

Investigators also discovered the trigger of the “thermal runaway event,” also known as an “explosion”: a dangerous combination of nitric acid and salts, triethanolamine, and “sWheat Scoop” organic kitty litter . (The DOE mentions the brand almost 400 times in its report.)

The cleanup itself will cost hundreds of millions, but that’s not where the mishap’s ledger ends.

A radioactive kitty litter ‘bomb’

waste isolation pilot plant wipp radioactive waste barrels drums doe
Workers wrap up drums of nuclear waste.

The “organic” part of the kitty litter in question is crucial.

That’s because wheat, which makes up the pee-absorbing bulk of organic kitty litter, contains plant cellulose that can burn. Standard kitty litter, meanwhile, is in organic, since it’s primarily made of clay.

So when drum-packing workers at Los Alamos National Laboratory (LANL) followed instructions to add an organic variety to soak up radioactive fluids, they were unknowingly packing up what Sarah Zhang at Gizmodo called ” the ingredients of a bomb .”

Why did they use fancy organic kitty litter instead of plain old clay kitty litter?

According to a Nov. 2014 story by Patrick Malone at the Sante Fe New Mexican , which we first learned about in Gizmodo’s detailing of events, it was likely the most common and mundane of human errors — a typo:

“Even before the waste was treated at Los Alamos, mistakes had been made that could have been instrumental in causing the accident at WIPP. Emails between WIPP contractors involved in the leak investigation indicate that something as simple as a typographical error in a revision of LANL’s procedural manual for processing waste containing nitrate salts may have precipitated a switch from inorganic clay kitty litter to the organic variety .”

A Sept. 2014 report released by the DOE appears to back this up, stating “handwritten notes that called for an organic absorbent to process nitrate salt drums were improperly relied upon to revise the Procedure”.

Expanding cleanup costs

wipp cleanup workers doe
Suit-clad workers descend into WIPP in April 2014 to inspect the facility.

Whether handwritten or typed, that error is going to be costly.

According to Vartabedian at the LA Times , the cleanup costs directly related to Drum 68660 will be about $640 million, per a July 2016 contract modification with the Nuclear Waste Partnership (the company that runs WIPP for the DOE).

Further, he wrote, this “does not include the complete replacement of the contaminated ventilation system or any future costs of operating the mine longer than originally planned.”

The DOE disputed that cost figure with Business Insider, saying direct cleanup costs will be about $244 million — not $640 million.

wipp explosion location air shafts
A cutaway diagram of the WIPP facility.

That extra money in the larger figure, it says, comes from a new two-project air ventilation system for WIPP. Together those (very expensive) projects may cost between $270 million and $398 million. But the DOE told us approval wasn’t entirely tied to the mishap.

“[T]he two ventilation system capital asset projects are needed as a result of a general evaluation of WIPP infrastructure upgrades and partially the event ,” a DOE spokesperson told Business Insider in an email (our emphasis added).

Whatever the case, WIPP isn’t entombing any nuclear waste while cleanup work continues — which means the US government’s grand scheme to seal it all up has a major wrench in its gears.

The Times reports the facility may need 7 years of additional operation to handle the backup of waste. At $200 million per year, according to the Times’ analysis, that could add up to $1.4 billion in extra costs triggered by the mishap .

The DOE did not immediately dispute that length of time, but said it anticipates WIPP could resume taking in — or “emplacing” — new drums of waste sometime in 2017.

“DOE can resume waste emplacement without the new permanent ventilation system,” the spokesperson said.

In the meantime, the DOE might also have to pay temporary storage and inspection costs for all of the waste that WIPP can’t entomb until the cleanup work is finished. The DOE couldn’t confirm or deny this, nor the cost.

“The Waste Isolation Pilot Plant (WIPP) is critical to the Department of Energy’s mission to cleanup nuclear waste generated by atomic energy activities,” the spokesperson said. “WIPP is the nation’s only repository for the disposal of nuclear waste known as transuranic (TRU) waste. The Department is committed to the recovery, and resumption of TRU disposal operations at WIPP when it is safe to do so.”

Business Insider contacted sWheat Scoop for comment, but the company did not immediately respond.

How the wrong cat litter took down a nuclear waste repository

David T. Hobbs is an expert in the complicated chemistry of nuclear waste management. He’s studied nuclear waste materials, radiochemical separations, and complex chemical environments for more than three decades. But three years ago, when an accident in a New Mexico repository brought disposal of U.S. defense nuclear wastes to a standstill, he was called to investigate a different kind of material—cat litter.

Hobbs, who doesn’t own a cat, is one of the researchers who studied the nuclear waste mixture that in 2014 led to a drum failure and radiological release at the Waste Isolation Pilot Plant (WIPP) near Carlsbad, N.M. The accident shut down the facility for three years. It was ultimately traced to an unorthodox sorbent, an organic cat litter called sWheat Scoop, that was used in error to prepare the nuclear waste for disposal at WIPP.

After a 33-year tenure, Hobbs retires this month from Savannah River National Laboratory, a South Carolina facility that produced plutonium isotopes for U.S. nuclear weapon and space programs. He recently spoke with C&EN about the accident at WIPP and the enduring thrill of scientific discovery.

Before WIPP opened in 1999, Hobbs and colleagues conducted studies on the radiolytic generation of gases from organic polymers and the hydrogen transport properties of filter vents used with transuranic waste drums. Their efforts fed into the creation of limits on the quantity of α-particle-emitting materials in waste and transportation packages. They also contributed to the testing protocol for qualifying filter vents.

When Hobbs heard about the Feb. 14, 2014, radiological release at WIPP, two things sprang to mind. First, Hobbs recalled a fire at the facility a week earlier that triggered an emergency response crew and sent six workers to the hospital for smoke inhalation. And second, because the disposal facility is built in a salt deposit and is designed to encapsulate the waste packages as the salt formation naturally flows and collapses around them, he wondered if a drum had been punctured in a collapse event.

“I could not think of a mechanism under which a drum itself would release contamination,” Hobbs says. “I thought it had to have been an external event.”

But an April 2014 accident investigation report by the Department of Energy came to a different conclusion. It says the radiological release likely stemmed from a single breached drum. Plus, photographs taken in May 2014 show an open container with heat damage to the surrounding area. This suggests that a thermal event inside the drum caused the container to fail.

The drum came from Los Alamos National Laboratory (LANL). It contained a reactive mix of radioactive nitrate salt waste, a neutralizing liquid, and organic cat litter, which had been used as a sorbent.

An October 2014 report from the Department of Energy’s Office of Inspector General points to a change in the packaging procedure at LANL that specified organic cat litter, when an inorganic sorbent was likely intended. Investigators traced a series of internal communications in which the specifications for “kitty litter/zeolite clay” were transformed into “kitty litter (clay),” the report says.

Combined with inadequate technical review, this resulted in LANL workers filling waste containers with a mixture of nitrate salts and sWheat Scoop, a cat litter that is 100% wheat, according to its manufacturer.

“It would have been much clearer if they had said an inorganic zeolite sorbent,” Hobbs says. “It’s been a very expensive mistake, costing at least half a billion dollars.”

Hobbs led a team that investigated the chemical reactivity of the mixture inside the drum as well as the series of events that caused the drum to fail and release ­radioactive material. Trained as an inorganic chemist, he says the experience brought back memories of organic chemistry labs he did as an undergraduate.

“I had no experience with kitty litter before,” he says. “There was a steep learning curve to think about all sorts of organic nitrate reactions.”

Though from a purely scientific perspective, he adds, it was an interesting problem to solve.

“We need to tell the story so that hopefully it won’t happen again.”

Hobbs’s team of chemists and engineers from several national laboratories had expertise in the characteristics of energetic materials, the reactivity of organic nitrate mixtures, and the handling of transuranic waste. Using what they knew about the history of the drum and what they discovered about the reactivity of the mixtures through experiments, the researchers pieced together an explanation for the thermal event that breached drum 68660.

Inside the drum was “a complex, heterogeneous mixture of materials with the potential for multiple reaction sites and reaction chemistries,” Hobbs and his team said in a March 2015 DOE report.

The contents of the drum, which included metal nitrate salts, the sWheat Scoop litter, and a neutralization reagent, were incompatible, the report says. The mixture likely underwent a series of exothermic reactions, including hydrolysis, oxidation, and nitration of the organic components, the report says. The reactions produced a thermal runaway condition in which increasing internal heat and pressure caused the waste container to break open and release radioactive material.

Hobbs says questions remain about why only one drum failed. LANL generated nearly 700 drums with a similar waste mixture that includes the organic cat litter. Drums with similar mixtures were isolated and are monitored, DOE says.

“Why didn’t more than one drum react as that drum did?” Hobbs asks. “Never to my knowledge did we firmly establish that there is something completely unique about 68660.”

Explaining how a nuclear weapons lab got mixed up in an expensive radioactive release accident because of cat litter is an odd circumstance. Hobbs says, “In hindsight, it certainly makes me uncomfortable having to talk about this occurring when I think of things that we do to evaluate hazards and risk in the laboratory—evaluating the compatibility of chemicals, for example.”

Hobbs adds, “We need to tell the story so that hopefully it won’t happen again.”

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