Thomas Gardiner
Degrading safety equipment in the spent nuclear fuel pool at the Pilgrim Nuclear Power Station in Massachusetts forced plant owner and operator Entergy to devise a plan to more than double its current number of used fuel assemblies in dry cask storage.
The current storage situation, in which close to 3,000 spent fuel assemblies remain in wet storage, has some local residents worried about potential disaster spreading as far as the nearby cities of Boston and Providence, R.I.
“In 2018, we will be conducting an additional dry fuel campaign to move approximately 600 more assemblies from the pool to dry fuel storage,” said Patrick O’Brien, Entergy’s spokesman at Pilgrim. That would be about one year ahead of the scheduled closure of the state’s last operational nuclear power plant, on May 31, 2019.
There are already 544 spent fuel assemblies in dry storage at Pilgrim, O’Brien said.
The facility in Plymouth was designed for and licensed to hold 880 spent fuel assemblies in wet storage when it was first constructed. Its license was changed in during the 1980s to allow storage of up to 3,859 assemblies. Now, with less than two years left in its operational life, the 45-year-old plant’s spent fuel pool holds over 2,990 assemblies.
The final assemblies now in the reactor, 580 in total, would be moved to the spent fuel pool in 2019, O’Brien said. “During decommissioning, all spent fuel will be moved from the pool into dry fuel storage.”
Criticality, the point at which a nuclear fission reaction becomes uncontrollable, could happen with as few as four fuel assemblies. Used fuel remains hot and must be stored in the pool to cool for several years. As they continue to decay, underwater assemblies release radiation. If protection methods fail, that radiation could initiate more reactions as it hits other assemblies, causing more reactions and more heat. If criticality were reached, the assemblies could boil off the water in the pool and start a fire that would result in a large radioactive release.
O’Brien said the facility has an emergency action plan in place that adheres to the standards set by the Nuclear Regulatory Commission. “The plan prepares the station to deal with a multitude of different scenarios, however small their possibility, including a test of spent fuel pool criticality,” he said.
With the addition assemblies in storage, Entergy installed Boraflex panels on the underwater storage racks, a practice used at a number of nuclear power plants across the nation. According to NRC inspections and reports, years of exposure to radiation and constant immersion in water have degraded about 900 of the nearly 5,000 panels, just shy of 20 percent.
“To prevent a fire from happening, they placed boron sheets on the assembly racks to absorb radiation,” said Mary Lampert, director of the nongovernmental Pilgrim Watch. “It was a good theory. Theories look good on paper, but now they discovered there is a problem. The NRC said 885 of those Boraflex panels were said to be susceptible to unacceptable deterioration by September 2017.”
Entergy enacted a plan to rearrange the bundles in storage, attempting to move the hottest bundles, those most recently removed from the reactor, away from the damaged panels.
“The problem is that when there was not a clear off-site waste solution, the NRC, instead of requiring spent fuel pools remain sparsely filled so they get air convection allowed them to continue re-racking,” Lampert said.
In a report released this month, Pilgrim Watch overlaid radiation plume maps from Japan’s 2011 Fukushima Daiichi nuclear power plant disaster over the Pilgrim plant and surrounding areas. The one-day radiation map shows a disaster of that magnitude would irradiate Boston and areas near Providence: home to more than 850,000 people combined.
The NRC and National Academy of Sciences, in respective reports from 2001 and 2016, found that a fuel pool disaster could release much more radiation than a core meltdown, and could leave contamination for hundreds of years across an area as large as 38,000 square miles. That is more area than all of Massachusetts and Rhode Island as well as neighboring Connecticut combined.
“Major population areas are at risk, and that’s not an amusing thought,” Lampert said. “Boston and Providence are right here, think what that would do to the economy. Public safety took a back seat and that’s all there is to it.”
