By Matthew Bigg
BROWNS FERRY, Alabama (Reuters) - A U.S. nuclear plant in Alabama similar in design to the earthquake-hit Fukushima facility in Japan has multiple defenses to prevent and tackle the same kind of emergency, its operator said.
Safety features at the Browns Ferry plant in northern Alabama are so superior to those at Japan's Fukushima Daiichi plant that even in the event of massive flooding the chances of a crisis were negligible, officials from the Tennessee Valley Authority (TVA) told reporters.
"What we have here is defense in depth, multiple levels of redundancy, backup to the backup to the backup," TVA communications consultant Jim Nesbitt told journalists who toured the facility on Friday as he explained the plant's elaborate safety systems.
The emergency at the Japanese plant has escalated since March 11 when a tsunami, triggered by a massive earthquake, knocked out power.
It has revived debate over U.S. nuclear safety just as the industry is set for its first expansion since an accident at the Three Mile Island nuclear facility in Pennsylvania in 1979. About 20 percent of U.S. electricity is supplied by nuclear power.
Japan's woes have focused attention on how far U.S. facilities are protected against one-off events such as terrorist attacks, earthquakes or flooding.
Comparisons between Fukushima and Browns Ferry are relevant because both have Mark 1 boiling water reactors made by General Electric. In total, there are 23 such reactors in the United States.
Some nuclear engineers deem these reactors more vulnerable than newer pressurized reactors to dangerous overheating in the event of power loss.
Critics point to objections raised by U.S. nuclear engineers in the 1970s and 1980s about possible design vulnerabilities in boiling water reactors and they say what happened at Fukushima merely validates those concerns.
"We've known since the 1970s that these designs are dangerous and now we've seen what can happen," Diane D'Arrigo, radioactive waste project director at the Nuclear Information and Resource Service, said in an interview.
"If there's a loss of power the pressure suppression system doesn't work. The pressure builds up and you have an explosion," said D'Arrigo, whose non-profit organization advocates that the United States turns to renewable energy.
BACKUPS: BATTERIES AND HOSES
Officials at Browns Ferry, which first came online in 1974, said they would look to improve safety in the light of events in Japan.
"Once they get things stable over there, there will be a full blown root cause (investigation) across the world and that's when we will get the fixes," said Keith Polson, vice president at Browns Ferry.
The facility combines the functionality of a big industrial plant with the security of a federal prison. Armed guards are stationed at the plant's perimeter and patrol inside the reactor building itself.
TWA officials offered journalists a tour that included a look at the "torus," a doughnut-shaped structure filled with water that helps cool the core, a spent fuel pool and a control center from which operators can shut the plant down in an emergency.
The officials stressed two crucial differences between Fukushima and Browns Ferry: the U.S. facility's key power sources were shielded against even a once-in-a-million year flood on the nearby Tennessee River, which provides water to the plant.
Second, multiple backup systems would continue to provide power and thus control, even in the event of a flood.
"A big difference between Japan and here is that when you have got all of your power systems we are able to cool much more quickly," said Preston Swafford, executive vice-president and chief nuclear officer at TVA.
Officials also pointed to fire hoses running up the interior of the building.
"These hoses were installed a few years ago. We don't think the plant in Japan had them," Swafford said. A series of batteries strategically located within the plant could also be activated in a crisis to continue to provide power.
VULNERABLE FUEL POOL?
Another focus of concern is the storage tank where highly radioactive spent fuel lies in a 29-foot deep (10-meter) swimming pool-like structure high in the reactor building.
Efforts to avert meltdown at Fukushima were in part centered on supplying water to spent fuel-rod storage.
Critics argue the pool is a weak spot because it is above rather than below ground and because the storage room itself is not encased by a sufficiently secure structure.
"If (terrorists) are going to aim for a nuclear plant, the Mark 1 is the best target because the fuel pool is way up high," said Arnold Gunderson, a nuclear engineer.
Since the 9/11 attacks, U.S. authorities have looked at whether the pools would be vulnerable to a terrorist attack and Fukushima would only revive those concerns, officials said.
"I believe the spent fuel pool is something that will be looked at very closely after Japan," said Robert Norris, a senior TVA official.
(Editing by Pascal Fletcher and Eric Beech)