In a letter to Nuclear Regulatory Commission Chairman Allison Macfarlane, the senators said the agency that oversees the nation's commercial nuclear industry has been freeing closed plants from certain emergency and security safeguards, even though the spent fuel on site remains dangerous for years to come.
They wrote that studies, including by the NRC, have concluded that "draining a spent nuclear fuel pool can lead to fires, large radioactive releases and widespread contamination."
The "NRC's analysis has even concluded that the health and economic impacts of a spent fuel fire could equal those caused by an accident at an operating reactor," the letter said.
They pointed to Japan's Fukushima Daiichi plant, which suffered multiple meltdowns following a 2011 earthquake and tsunami, as evidence that exhaustive emergency and evacuation planning must be in place, even at shuttered plants. The senators said research has found spent fuel pools "could not be dismissed as potential targets for terrorist attacks."
The letter was sent by Sens. Barbara Boxer of California, Edward Markey of Massachusetts, Patrick Leahy of Vermont and Kirsten Gillibrand of New York, all Democrats, and independent Bernie Sanders of Vermont.
NRC spokesman Eliot Brenner issued a one-sentence statement Friday saying the commission would reply to the senators' letter "in the normal course of our correspondence process."
The letter said exemptions have been granted at 10 shuttered reactors, some dating to the 1980s, and others are possible, including at Southern California's San Onofre plant, which closed last year.
The senators urged the commission to reject any requests for exemptions.