As the United States continues to grapple with long-term storage of highly radioactive spent fuel from the nation's nuclear power plants, science watchdogs are warning of serious flaws with the current storage method, which involves densely packing the combustible spent fuel assemblies under at least 20 feet of water in pools located at individual plants while awaiting creation of a permanent repository.

The warning came in the May 26 issue of the journal Science, in a policy forum article titled "Nuclear safety regulation in the post-Fukushima era: Flawed analyses underlie lax U.S. regulation of spent fuel." The authors are physicists Edwin Lyman of the Union of Concerned Scientists' Global Security Program and Michael Schoeppner and Frank von Hippel of Princeton University's Program on Science and Global Security.

Following the 2011 disaster at Japan's Fukushima Daiichi nuclear power plant, the U.S. Nuclear Regulatory Commission (NRC) ordered a comprehensive review of regulations. While the buildings that housed the Fukushima plant's spent fuel pools were destroyed, the spent fuel fortunately remained covered with enough water to keep the metal cladding that encloses the uranium from catching fire. Scientists working for the NRC estimated that a fire in one of the plant's pools would have dramatically increased the amount of radioactive pollution released and could have led to the forced long-term relocation of between 1.6 million and 35 million people from Japan's East Coast rather than 150,000.

The NRC adopted a number of safety upgrades after the Fukushima disaster but rejected a measure to end dense packing of the 90 spent fuel pools located at nuclear plants across the U.S. — a technique utilities use to reduce storage costs. But the authors say the screening process failed to adequately account for the impacts of "large-scale land contamination events" from spent fuel pool fires. The NRC's own technical evaluation estimated that a fire in a densely packed spent fuel pool at the Peach Bottom plant in Pennsylvania just north of the Maryland border would require the evacuation of 4.1 million people from an area of over 9,400 square miles.

"Unless the NRC improves its approach to assessing risks and benefits of safety improvements — by using more realistic parameters in its quantitative assessments and also taking into account societal impacts — the United States will remain needlessly vulnerable to such disasters," the authors warned.

According to a 2012 Congressional Research Service report, two of the five states with the largest amount of spent nuclear fuel stored in wet pools are in the South — North Carolina and Alabama. The others are Illinois, Pennsylvania and New York.

More realistic assessments needed

Under the NRC's current rules (which the authors point out are self-imposed), the potential backfit for the storage problem — moving the spent fuel from the pools to air-cooled dry storage casks after a few years — could be adopted only if 1) the monetary value of the resulting public risk reduction were to exceed the cost of implementation and 2) the increase in safety were "substantial." The estimated cost of transferring the spent fuel to dry cask storage is $5 billion, about $50 million for each of the nation's 100 reactors.

The NRC's analysis assumed the chance of a fire resulting in a large release of radioactive pollution would be small, though with considerable uncertainty. Its risk analysis also failed to account for a possible terrorist attack and made other assumptions that minimized the estimated health and economic consequences of a high-density fuel pool fire.

For example, it ignored accident consequences beyond 50 miles and assumed radiation dose standards for population relocation that were less restrictive than those recommended by the Environmental Protection Agency. In addition, the NRC overlooked the societal risks of accidents such as the psychological trauma of mass relocation.

"In our view, if the NRC were to use more realistic quantitative assessments and give weight to societal impacts, a requirement to expedite transfer of spent fuel to dry casks would be justified," the authors wrote.

They are calling on Congress to allocate the $5 billion needed for the dry storage casks. They also note that states can take action to reduce risk. For example, New York and Illinois recently approved subsidies for continued operation of nuclear reactors that could add conditions requiring utilities to end dense packing of spent fuel pools.

The renewed concerns about spent nuclear fuel storage come as the Trump administration is trying to jumpstart the controversial effort to create a permanent repository for the waste at the Yucca Mountain site in Nevada, which is opposed by that state's entire congressional delegation as well as by environmental advocates and nearby Native American communities.

Back in March, the administration requested $120 million to restart the stalled approval process. That same month, Energy Secretary Rick Perry toured the Yucca Mountain site, just weeks after his home state of Texas filed a lawsuit against the federal government charging that it has failed to follow the law by providing a permanent disposal site for nuclear waste.

While Congress approved the Yucca Mountain site in 2002, the Obama administration cut off funding in 2011 amid growing concerns including the site's suitability and transportation risks.