Browns Ferry vulnerable to attack
Terrorism wasn’t a threat when plant was designed
By Eric Fleischauer
Suspended more than 60 feet above ground at Browns Ferry Nuclear Plant, three cooling pools contain more than 2,000 tons of radioactive material.
If a terrorist attack or accident breached one of those pools, causing the water to pour out, fire or meltdown could make Decatur, Athens and even Huntsville uninhabitable for decades, experts say.
The Browns Ferry pools, built in the early 1970s, were not designed to withstand terrorist attack.
“In those days, we weren’t thinking about suicide attacks and sabotage,” said David Lochbaum, director of nuclear safety at the Union of Concerned Scientists. He was a reactor engineer at Browns Ferry Unit 1 from 1980 to 1983.
Scientists who have studied the issue concluded a spent-fuel pool fire would contaminate, with cancer-causing radiation, up to 10 times the area contaminated in the 1986 failure of the reactor at Chernobyl in the former Soviet Union.
“They’re vulnerable as hell,” Peter D.H. Stockton said of the Browns Ferry spent-fuel pools. Stockton is a former special assistant on nuclear issues to the secretary of the U.S. Department of Energy.
Most nuclear plants store spent fuel in pools at or below ground level, greatly reducing the likelihood of a rapid loss of coolant. The uncovered 35-by-40-foot surfaces of the spent-fuel pools of Browns Ferry’s three reactors are on the same floor. They are near the top of the 152-foot reactor building. The floors of the pools are three stories above the ground.
The pools were designed to withstand natural calamities, including earthquakes, Browns Ferry spokesman Craig Beasley said.
The walls and floors are made of reinforced concrete from 4 to 6 feet thick. The water in each pool is 40 feet deep. They are centrally located in the reactor building, which faces the Tennessee River.
“At the time they were built, the idea of an airplane, like we experienced in 2001, was probably not thought of,” said Beasley. “Those pools are designed to withstand quite a bit of punishment, though.”
As designed originally, the Browns Ferry cooling pools were to have been loosely packed.
“If water had been lost from one of these pools, then air would have been able to circulate relatively freely around the spent fuel, thereby cooling the fuel,” explained Gordon Thompson, executive director of the Institute for Resource and Security Studies. That changed, however, with delays in the creation of a national spent-fuel repository. Considered imminent when Browns Ferry was built in 1974, no such repository exists. Yucca Mountain in Nevada was the location of choice, but political and scientific hurdles leave its status in limbo.
“If water is lost, in almost all conditions, you will then have a fire that releases extremely large amounts of radioactive material,” Thompson said. “For practical purposes, it’s a given.”
Thompson co-authored a National Academy of Sciences report last year on spent-fuel pool vulnerability.
Each Browns Ferry reactor uses 764 15-foot-tall fuel bundles at a time. TVA replaces the fuel bundles, each of which weigh 600 pounds, every six years. The spent fuel goes to the cooling pools, where it must remain for almost five years before its heat and radiation have subsided enough to permit dry storage.
In harm’s way
More than two decades after the Chernobyl event, that area is uninhabitable within 19 miles of the plant. Athens is eight miles from Browns Ferry. Decatur is nine miles away. Also within 19 miles of the plant are Elkmont, Rogersville, Moulton, Courtland and Priceville.
“The uninhabitable area would be considerably greater than from the Chernobyl event,” Thompson said. “It could run into thousands of square miles.”
Radioactive material from a spent-fuel pool would travel much farther than it did from Chernobyl’s reactor because of the comparatively high levels of radioactive cesium in the pools. Cesium is lightweight, so it would travel great distances in the Tennessee Valley’s prevailing winds, which blow to the east.
“Huntsville would be in a bad way,” Lochbaum said. “It’s very much in harm’s way should this occur.”
Even with Chernobyl’s much lower cesium levels, Lochbaum said, some areas up to 100 miles from the reactor remain uninhabitable.
Cesium burns at a temperature below that of the ignition point of the zirconium sheaths, so massive amounts would boil into the atmosphere in the event of a spent-fuel pool fire, Thompson said.
The possibility of a spent-fuel fire could be eliminated, even with Browns Ferry’s above-ground pool design, but the Nuclear Regulatory Commission is not requiring the solution and TVA is not pursuing it.
The solution, advocated by the National Academy of Sciences in a report issued last year, is to empty the spent-fuel pools of all fuel more than five years old. The spent fuel, NAS said, should be transferred to dry casks that TVA and other nuclear plant owners maintain on site.
Congress asked NAS to prepare the report.
“We saw no good safety reason for doing that,” said NRC spokesman Roger Hannah. “The NRC has maintained and continues to maintain that fuel can be stored safely both in spent-fuel pools and dry casks. They both meet the regulations, and they both provide adequate protection.”
Browns Ferry already has three such casks. Beasley said TVA plans to fill another five casks with spent fuel this year.
Like most nuclear plants, though, TVA is doing little more than keeping up with its fuel usage. The spent-fuel pools remain full.
The main reason for the NRC’s rejection of the NAS proposal is expense. A dry cask holds 15 to 20 tons of spent-fuel rods, a tiny percentage of the rods stored in the pools. Securing spent fuel in the heavy-duty containers costs about $1 million per cask.
“You’re going to have to move the fuel to the casks eventually,” Lochbaum said. “We think now is the time to make that happen, to make the plants a little bit less vulnerable to terrorists.”
Thompson thinks part of NRC’s reluctance to impose the requirement reflects a nuclear industry attitude.
“Partly it’s money,” Thompson said. “Partly it’s that this is not an industry that likes to admit error.”
The dry casks are transportable, so in the event Yucca Mountain opens, spent fuel will have to be moved into the casks for rail transport. If Yucca Mountain does not open, the spent fuel will have to be moved to casks to make room for newer spent fuel.
NRC spokesman Roger Hannah said dry casks have vulnerabilities.
“The NRC thinks dry casks and spent-fuel pools are equally secure and equally safe to the public,” Hannah said. “Spent fuel now is better protected than it ever has been.”
Beasley said moving spent-fuel rods to casks can expose workers to radiation, so TVA does this as little as possible.
While the NAS proposal — emptying the pools of all spent fuel more than five years old — would be ideal, Thompson said a cheaper approach probably would solve the problem.
“Use low-density racks for the spent fuel, as per the original design,” Thompson said. “That would prevent fuel ignition in almost all scenarios.”
There are options that might keep even densely packed, dry spent-fuel rods from igniting, but they generally require that workers have access to the pools.
“There is no way that operators or emergency personnel could remain there to retain control,” Thompson said. “In the immediate vicinity of the pool, personnel access would be impossible” because of the heat and radiation.
Two of the Browns Ferry pools are connected by a canal, said Lochbaum. The canal is about half the depth of the pool. A rapid loss of water from one pool could cause a partial loss of water in the adjoining pool. The remainder of the water could boil off in the extreme heat, causing that pool to ignite as well.
Stockton, now senior investigator with the Project on Government Oversight, said three categories of terrorist attack concern nuclear engineers and safety experts.
Airplanes. A 9/11-style jetliner attack is the worst-case scenario. Not only would it breach the pools, it would make impossible any effort to control the heat. A small plane loaded with explosives would do the same, he said.
Projectiles. While the Nuclear Regulatory Commission discounts the possibility, Stockton and other experts fear that an explosive projectile, such as a platter charge or an anti-tank missile, could breach the cooling pools. Platter charges need no firing device and are relatively easy to make. The Army uses them to destroy bridge supports.
Stockton said the fact that Browns Ferry is within the line of sight of many non-secure areas, on and across the river, makes it particularly vulnerable.
Ground attack. The surfaces of the spent-fuel pools are open. Some studies suggest a ground attack would result in a loss of coolant if the attackers dropped knapsack-contained explosives in the pools. The weight of the water above the explosives would direct the charge at the pool floor, increasing the likelihood of a rupture.
“With the pools up as high as they are and relatively exposed, they do make attractive targets,” said Lochbaum.
NRC’s Hannah said the various theories on spent-fuel pool vulnerabilities are not compelling.
“Under certain scenarios you can postulate a situation where you would have some damage to a spent-fuel building,” Hannah said. “I can’t get into details, but there are a number of things that would preclude that from happening.”
Hannah said above-ground pools remain an option for any new plants that are built, “but I don’t know if we may look at enhancing or changing those regulations. At this point, we’re not reviewing applications, so we’re not looking at those particular aspects.”
The risk of a spent-fuel fire is not limited to terrorist attack. Some experts focus on the risk of an accident when fuel rods are removed from the pools. A crane above the pools lifts up to 68 tons of fuel in two canisters. One canister weighs 19 tons. Beasley said he did not how much the other, larger canister weighs. The issue is whether a dropped canister would fracture the pool floor, causing a rapid loss of coolant in an above-ground pool.
Thompson is critical of TVA for spending $1.8 billion when, for a few million dollars, it could eliminate the spent-fuel vulnerability.
“TVA is supposed to serve the public interest,” he said. “I would have thought that’s one utility that should be more seriously thinking about the spent-fuel pools.”
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