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Long before Japan’s nuclear crisis or even the 1979 Three Mile Island accident, U.S. regulators had strong reservations about the design of boiling water reactors and considered banning such units over fears about their vulnerability to radioactive leaks, documents show. An industry study also noted that the reactors had less ability to withstand earthquakes than other models.

In the early 1970s, just as a number of reactors were about to be licensed, Stephen Hanauer, a senior member of the Atomic Energy Commission staff, suggested banning “pressure suppression” methods to contain radiation in the event of a meltdown — methods built into General Electric’s Mark I and Mark II containment designs as well as Westinghouse’s ice condenser design. The advice was considered and disregarded.

“Steve’s idea to ban pressure suppression containment schemes is an attractive one in some ways,” Joseph Hendrie, then a deputy director with the AEC, wrote in a Sept. 25, 1972, memo. Hendrie acknowledged that alternative, “dry” containments — featuring the towers or domes commonly associated with nuclear plants — had the “notable advantage of brute simplicity in dealing with a primary blowdown, and are thereby free of the perils of bypass leakage.”

But regulators ultimately decided that the technology developed by General Electric and Westinghouse was “firmly embedded in the conventional wisdom.” Banning it, Hendrie wrote, “would generally create more turmoil than I can stand.” His memo was obtained by the Union of Concerned Scientists through a Freedom of Information Act request.

The 85-year-old Hendrie, reached at his home on Long Island, N.Y., told the Center for Public Integrity that “there were some serious questions about the pressure suppression scheme, but it seemed in many ways like a good way to deal with a loss-of-coolant accident. To have declared it unacceptable when we’d already been licensing [plants] with it seemed more of a tearing up of a regulatory structure than was justified. When I said it would create more tumult than I can stand, I think I really meant it.”

Hendrie’s pragmatism eventually earned him a promotion as he later became the third chairman of the Nuclear Regulatory Commission, a position he held during the Three Mile Island accident, and regulators’ sentiments allowed the design to proliferate around the world. He is now retired.

Today, three of six GE reactors at the Fukushima Daiichi plant in northeastern Japan are in danger of meltdown after a catastrophic earthquake and tsunami. And 31 aging GE reactors of the same design — 23 of them with Mark I containment systems and eight of them with Mark II — continue to operate in the U.S., raising concerns among both politicians and scientists. The Mark I containment is rectangular, the Mark II cylindrical. This NRC document explains the two in more detail.

The nuclear industry and the NRC said Monday they remain confident that the GE reactors, as well as the nine Westinghouse ice condenser reactors, are safe given the risks they face, and that Japan’s crisis represents a worst-case scenario.

“The BWR Mark 1 reactor is the industry’s workhorse with a proven track record of safety and reliability for more than 40 years,” GE said in a statement. “Today, there are 32 BWR Mark 1 reactors operating as designed worldwide. There has never been a breach of a Mark 1 containment system.”

NRC Chairman Gregory B. Jaczko told reporters Monday that all U.S. nuclear plants “are designed to withstand significant natural phenomena like earthquakes, tornadoes and tsunamis. We believe we have a very solid and strong regulatory structure in place right now.”

But industry watchdogs see the fateful decision regulators made almost 40 years ago — to choose political and economic pragmatism over tougher safety standards — as endemic in the culture of the NRC as it deals with the prevention of low-probability, high-consequence accidents.

The decision was based largely on cost, said Jim Riccio, a nuclear policy analyst with Greenpeace. The pressure suppression containment systems, which use water or extreme cold to keep radiation from leaking into the environment, were cheaper than dry systems, which require construction of the massive domes or towers. But they were inherently less safe, Riccio said.

“They were designed to withstand a pipe break, not a meltdown,” he said. It wouldn’t take a major earthquake or a tsunami to knock out primary and backup power and push the systems to the breaking point; a hurricane or tornado could suffice.

Vulnerable to Seismic Events

A 1975 report for GE by a team of scientists and engineers found that the company’s boiling water reactors were more vulnerable to seismic events than pressurized water reactors — such as Three Mile Island — designed by Westinghouse and other firms.

“The PWR [pressurized water reactor] design is inherently more seismic resistant because of lower reactor vessel placement and the need to design for larger LOCA loadings,” the report said. LOCA is an acronym that stands for loss of coolant accident — the type of accident triggered by the earthquake and tsunami in Japan. GE’s research team said it would push to make the company’s newer reactors more able to withstand earthquake-related stresses.

The report added that “because of phenomena recently discovered all BWR [boiling water reactor] containment types are undergoing extensive additional analyses to evaluate structural adequacy.” It said Mark I and Mark II containments “are likely to be redesigned and retrofitted.”

In 1986, former NRC official Harold Denton told a group of utility executives that, according to commission studies, GE Mark I reactors had “something like a 90 percent probability of that containment failing” under accident conditions.

On top of concerns about the boiling water reactors are worries about relicensing, the storage of spent fuel, and the design of the next generation of plants.

Relicensing: On March 10, one day before the earthquake in Japan, the NRC voted to relicense one of the GE Mark I plants — the 39-year-old Vermont Yankee Nuclear Power Station near Brattleboro, Vt. — for an additional 20 years. Last year, the Vermont Senate voted overwhelmingly against licensing of the plant beyond 2012, noting that it has suffered a litany of safety problems, including leaks of radioactive tritium and the collapse of a cooling tower. Vermont is the only state that has the authority to approve a reactor operating license.

Riccio said the NRC’s action was predictable. About 20 years ago, he said, the agency “lowered the bar [for relicensing] so low you can’t even trip over it. We’re renewing aged reactors’ licenses with a rubber stamp.”

NRC spokesman Scott Burnell said the decision to extend Vermont Yankee’s life through March 2032 came after lengthy NRC reviews. “In the case of Vermont Yankee, not only did we have more than two years of intense technical review, we also had a very deliberate, very appropriate legal review that lasted until last Thursday,” he said. “That would not meet most people’s definition of a rubber stamp.” It was during that review that some of the most serious tritium leaks at the plant occurred.

Burnell added that the decision does not guarantee that the plant, operated by Entergy Nuclear Operations, “has a blank slate to continue running” for two more decades. It will have meet rigorous safety standards at all times, he said.

Spent Fuel: Spent fuel rods at Fukushima Daiichi may have burned during the most recent fire at the plant, releasing radiation, Japanese officials reported Monday. Critics in the U.S. say that too much spent fuel at reactors is packed tightly into onsite pools — awaiting a permanent storage site — rather than being moved as quickly as possible into “dry casks,” which are less vulnerable to accidents or terrorist attacks.

“Current onsite storage plans place spent fuel in wet pools until the pools are essentially filled and then intermittently transfer spent fuel to dry casks when needed to free up space for the next discharge from the reactor,” David Lochbaum, director of the Union of Concerned Scientists’ Nuclear Safety Project, wrote in a submission to the Blue Ribbon Commission on America’s Nuclear Future last August. “Responsible onsite storage accelerates the transfer of spent fuel to dry casks to maintain the inventory within the wet pools near minimal amounts.”

Burnell said the NRC believes the current method of spent fuel storage is safe. “The combination of both spent fuel pools and dry-cask storage is an appropriate and acceptable means of safely and securely storing spent fuel until such time as there is a national destination for that material,” he said.

New Reactors: Just days before the earthquake in Japan, Rep. Edward Markey of Massachusetts, the top Democrat on the House Natural Resources Committee, sent a letter to NRC chairman Jaczko, asking the agency to withhold final approval of a new Westinghouse reactor design due to “serious safety concerns.” Markey wrote that an NRC expert had identified “potential loopholes, which, if left open, allow designs for unsafe reactors to go forward despite the risk that an earthquake or aircraft impact could result in a catastrophic core meltdown.”

Fourteen reactors based on the design — which has never been built — are under development in Alabama, Florida, North Carolina, South Carolina and Georgia.

The Nuclear Energy Institute, a trade association for the nuclear power industry, said in a statement that “Japan is facing what can literally be considered a ‘worst case’ disaster and, so far, even the most seriously damaged of its 54 reactors has not released radiation at levels that would harm the public. That is a testament to their rugged design and construction, and the effectiveness of their employees and the industry’s emergency preparedness planning.”

In a conference call with reporters on Monday, Lochbaum, of the Union of Concerned Scientists, hinted at another possible problem. “The primary problem the [Fukushima] plant faced was loss of power and backup power,” he said. “The situation that plant faced was having eight hours of battery [capacity] and losing that.”

“In this country, most of our reactors are only designed with battery capacity for four hours, so we’re more vulnerable in those situations. While many of our plants may not be vulnerable to the one-two of earthquake and tsunami, many of them are in situations where hurricanes or tornadoes or ice storms or a tree in Cleveland could cause a blackout that would put us in the same situation.”

German and Swiss reactors have had the most redundant emergency systems for an accident involving an uncooled core.

In 1975, a team of engineers and scientists attempting to limit the risks of GE’s containment systems noted that the NRC requires that for any single accident “which might result in an uncooled core, two emergency cooling systems must be available, either of which could by itself cool the shutdown core, and both of which have considerable internal redundancy.”

Similarly, Japanese authorities allowed nuclear plants with only two emergency cooling systems — both of which have proven unreliable in the events triggered by the earthquake and tsunami.

But German and Swiss authorities as far back as the early 1970s required three backups. “The argument runs that one backup system could at any time be out of action, because of repair work, or surveillance testing, that a second could fail to work because of an unknown defect, and that a third would then be available if needed,” the team working for GE noted.

On Tuesday, Germany decided to shut down its seven oldest nuclear power plants at least temporarily, pending a safety review.

Hendrie, the former NRC chairman, remains a believer in nuclear power. All technologies have some risk, he said. “The Japanese experience is apparently going to be pretty bad, but mankind over the centuries has devised technologies that turned out to be very useful to mankind, developed them, taken some lumps from accidents and mishaps, made corrections to the technology and moved ahead,” he said. “A lot of coal miners die. We pollute the Gulf of Mexico. So, all these technologies have their unhappy connections. And I wouldn’t slight the need for strong regulations. But I think it’s reasonable and, indeed, essential for us to move ahead and keep on with nuclear energy development.”

Bill Sloat and Susan Stranahan contributed to this story

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A journalist since 1978, Jim Morris has won more than 80 awards for his work, including the George Polk...