It’s still just a theory, but it’s the best they’ve got.
As investigators explore the possibility that nitrate salts caused a chemical reaction hot enough to melt material in nuclear waste drums at the Waste Isolation Pilot Plant, one thing is clear: No one thought the salts were a problem.
On Valentine’s Day this year, radiation leaked from the deep underground repository near Carlsbad, which holds remnants of the country’s nuclear defense program. The Department of Energy and its contractors have been searching for answers about what happened ever since.
In its only publicized theory, DOE suggested earlier this month that untreated nitrate salts may have combined with “cellulosic material” – in this case, a new organic cat litter used as an absorbent – to cause a reaction that may have released intense heat. The idea is that the organic, instead of inorganic, cat litter not only didn’t do its job but may have precipitated a reaction, according to a former WIPP scientist.
A set of drums from the Los Alamos National Laboratory has been the focus of the nitrate salts theory, although waste from two other sites is also underground where the leak is believed to have occurred and is under investigation.
Every container shipped to WIPP comes with a lengthy document detailing every single thing inside, material and chemical. So how did untreated nitrate salts slip through? The answer is: they didn’t. The authorities knew they were there because they were permissible and were believed to have been neutralized.
Nitrates in different forms are used to process plutonium, a radioactive element of nuclear waste, and are present in waste coming not just from LANL but other sites as well. A profile of the contents of the stream of LANL waste in question shows that, as recently as last fall, WIPP and the New Mexico Environment Department believed the nitrate salts had been properly handled.
The profile said, “LANL has determined that these salts … would not stimulate combustion” and also determined “that nitrate salts, when mixed with inert absorbent material, would further support the managing of the waste as non-ignitable.”
Jim Conca, a scientist who worked for a decade at WIPP through 2010, said the issue “may have been a unique chemistry” in a single waste stream or single drum.
“It sounds like this is a slow chemical reaction that built up pressure,” he said. “There are a lot of unknowns.”
Nitrate salts “are just salts,” said Trais Kliphuis, WIPP staff manager in the Environment Department’s Hazardous Waste Bureau. “They are not really that ignitable.”
However, she said, the nitrate salts in the LANL drums in question “were dissolved in a liquid sludgy matrix. If they weren’t neutralized appropriately, they could have combined with cellulose in the kitty litter” and caused a reaction.
The Environment Department indicated that it is looking into why the absorbent cat litter was switched from an inorganic to organic version, and how that decision was made.
The latest photos and video taken by WIPP crews investigating underground show streaks of black melted material on white drums and piles of magnesium oxide powder where the heavy protective sacks sitting on the drums disintegrated. The 3,000-pound-plus sacks of magnesium oxide are an engineered barrier to prevent radiation from releasing into the environment.
WIPP hasn’t used the word “explosion” to describe what happened but rather “heat-producing event.” Just how hot the waste got, and how powerful the event was, is unknown – but it was hot enough to melt plastic and rubber on the drums, dissolve the sacks holding magnesium oxide and, somehow, allow radiation to escape the drums.
Also unknown are what other theories WIPP is pursuing as it searches for the cause of the radiation leak that contaminated at least 21 workers with very low levels of plutonium and americium. WIPP has been reluctant to share its theories publicly or with the state Environment Department.
“If this is not the correct theory du jour, what else are they looking at?” said Kliphuis. “This may not be what caused this. It’s important that we keep asking questions.”