Wednesday, June 26, 2013

the $64,000 question is: “Which is safer? Spent fuel pools or dry casks?” #NukeFreeCal

New NRC Study Shows Benefits of Transferring Spent Fuel to Dry Casks:
The study released Monday by the Nuclear Regulatory Commission (NRC) on the potential consequences of an earthquake on spent fuel pools reinforces our concerns about spent fuel pool safety and fails to address some key issues.
The NRC considered only one scenario—an earthquake—at one nuclear power plant—the Peach Bottom plant in Pennsylvania—and neglected to consider other factors relevant to the benefits of transferring spent fuel from pools to dry casks. Even so, the report demonstrates that reducing the amount of spent fuel in pools can drastically reduce the amount of radiation exposure to the public in the event of an accident.

Limitations of the Study

The NRC study analyzed the potential effects of a large earthquake on a spent fuel pool at a boiling water reactor (BWR) reactor, which is what occurred at Fukushima two years ago. But there are other scenarios that could trigger a loss of water in a spent fuel pool besides an earthquake.
“By discounting other plausible threats to spent fuel pools, the study doesn’t add anything to the debate over spent fuel management,” said UCS’s Dave Lochbaum. “The NRC must address many shortcomings if its final report is to help the Congress and the administration make an informed decision about this important issue.”
The study did not consider the possibility of a terrorist attack, for example, which could compromise a spent fuel pool, or other plausible scenarios. In a 2006 report, the National Academy of Sciences concluded that terrorists might choose to attack pools because they are less protected structurally and contain more radioactive material than reactor cores, and that such attacks could lead to a loss of coolant in the pool and a fire in the pool that would lead to a large radioactive release to the environment.
The NRC conceded at a June 24 meeting of the National Academy of Scientists’ Fukushima committee that it had not considered scenarios, such as a terrorist attack, that could cause a “partial drain-down” of the spent fuel pool. The NRC study’s failure to consider a partial drain-down is an important omission since it could result in a higher likelihood of a fire than an earthquake scenario that causes a complete loss of a pool’s water.
Dave notes that there have been several accidents due to other causes where spent fuel pools experienced a partial drain-down. In 1984, a ruptured refueling cavity seal drained 200,000 gallons at the Connecticut Yankee nuclear plant. In 1986 an inflatable seal at the Hatch plant in Georgia failed, causing 140,000 gallons to drain from its spent fuel pool. BWR pools typically hold about 400,000 gallons of water.

The $64,000 Question

The study also failed to compare the quantitative risks of storing spent fuel in pools versus dry casks. Instead, it looked at one initiating event—an earthquake—and concluded that storing spent fuel in pools is adequately safe by NRC standards.
As Dave says, the $64,000 question is: “Which is safer? Spent fuel pools or dry casks?”
While the report did not specifically answer this question, UCS’s Ed Lyman points out that the facts contained in the report actually reinforce the conclusion that dry cask storage is safer and more secure than cramming more spent fuel rods into pools that weren’t designed to accommodate that much material.
In particular, he notes that the NRC study acknowledges that storing spent fuel rods in overstuffed pools is risky for a number of reasons. For example, the study states that a fire in a densely packed spent fuel pool at the Peach Bottom plant could contaminate thousands of square miles with radioactive material, force the long-term displacement of millions of people, and cause tens of thousands of cancer deaths. The study did not evaluate plants closer to major urban areas than Peach Bottom, such as the Indian Point plant near New York City, where the consequences of a similar event could be even greater.
However, the study shows that removing spent fuel older than five years from the pool could reduce the amount of radioactive cesium released by factor of 80, the number of cancers by a factor of 10, and the total amount of land that would be uninhabitable by a factor of 50.
The bottom line—reinforced by the details in the NRC study—is that the public is better protected by reducing the amount of spent fuel storage in pools at U.S. reactors by moving it to dry storage. Doing so is an important defense-in-depth measure and that would significantly reduce the radiological risk to the public from spent fuel pool fires.