Problems at US pilot facility highlight challenges facing underground nuclear waste disposal
10 July 2014
A serious accident in February 2014 at the United States’ only deep storage repository for nuclear waste has still to be satisfactorily explained. Five months later, scientists still do not know what caused the explosion of a barrel of nuclear waste at the Waste Isolation Pilot Plant (WIPP) in Carlsbad, New Mexico.
WIPP cutaway: Photo - DOE
WIPP, carved out of a salt bed 655 metres below the desert near Carlsbad, is run by the US Department of Energy (DOE) and stores low- and medium-level military nuclear waste, mainly from the Los Alamos National Laboratory, containing long-lived man-made elements such as plutonium and americium.
Following the explosion, 22 workers at the facility were exposed to radiation and trace elements of radioactive materials were detected by nearby surface sensors. Initial surveys of the underground storage panel where the incident took place show blast damage and evidence of several fires having broken out.
According to a preliminary report released in April by a DOE-appointed Accident Investigation Board, the root cause of the accident lies with the department’s field office and Nuclear Waste Partnership, the contractor that operates the site. They failed to identify radiological risks and make plans to control them, the report’s authors said. They added that maintenance of safety systems was neglected, and that DOE oversight was “ineffective”.
The DOE said the second phase of its investigation would start mid-July, and this would include controlled entries by a team of experts into the underground storage area where the radiation originated. They will try to reach the damaged waste container believed to be the source of the leak and check other containers for damage.
In a letter released on July 3, the Los Alamos National Laboratory admitted to the New Mexico Environment Department that an internal investigation had revealed several violations of the facility's Hazardous Waste Facility Permit. For example, the lab admitted that it did not follow proper procedure when making the switch between different types of cat litter (which is added to the waste drums to absorb moisture). The investigation also found that the lab did not follow up after tests showed that certain waste drums were highly acidic.
Some researchers suspect that the new cat litter, the acidic waste and lead might all have contributed to a chemical reaction that produced the explosion. However, neither state nor federal investigators have been able to prove this hypothesis. They have performed hundreds of attempts to re-create the explosion with test containers, but all have failed.
National Public Radio said the incident could have been triggered by a piece of salt falling from the panel ceiling, crushing the waste container(s).
Don Hancock, director of nuclear waste safety at the Southwest Research and Information Center, a watchdog group in Albuquerque, has been critical of the government's failure to explain the WIPP incident, quantify its health or environmental impacts, or explain how to prevent future accidents.
Hancock notes that five months after the incident, it is still unclear whether other containers inside WIPP might be leaking, and that the breached container has yet to be physically examined. Few if any of the underground tunnels through which radioactive material was expelled to the surface have been tested, he says.
An article in Nature claims that the incident could be in large part due to the government disbanding a key independent scientific body charged with oversight of the safety of the facility.
The Environmental Evaluation Group (EEG), a scientific body set up in 1978 and charged with protecting public health and the environment, provided an independent and credible source of information and review of WIPP. The EEG was staunchly independent of the DOE, and its technical expertise and authority were widely viewed as key to the public and political trust that the repository won, Nature says.
But in 2004, with WIPP by then fully operational, the group was defunded and disbanded. Responsibility for oversight moved primarily to the New Mexico Environment Department in Santa Fe and the US Environmental Protection Agency.
Whoever bears final responsibility, the effect on nuclear waste disposal in the US has been dramatic. In May, a Nuclear Waste Partnership manager said the investigation and clean up could cause a suspension of waste disposal at WIPP for up to three years, which would leave large amounts of nuclear waste nationwide stranded.
Los Alamos, in particular, faces difficult decisions what to do with plutonium-contaminated waste at its northern New Mexico campus before the wildfire season peaks.
WIPP is the only operational underground geological nuclear waste facility in the world, and as such, had been held up as an example of the future of nuclear waste disposal. The problems it is facing following the February incident could well make it more difficult for consent to be gained for other such facilities elsewhere.
Sweden, Finland and France all have active underground repository programmes in the planning or construction stage, and a number of other countries are considering following suit. The lessons of the WIPP incident need to be carefully examined by all potential future underground facility operators when the investigation is finally complete and brought into the public domain.
Given the far greater dangers of storing nuclear wastes on the surface for the hundreds of thousands of years that they remain highly toxic, underground disposal in geologically stable repositories is the only safe long-term solution. This early setback should not be allowed to obscure that fundamental message.