Washington — Nuclear power critics have released a report citing potential safety problems resulting from the use of O-rings -- like those leading to the space shuttle Challenger accident -- in nuclear power plants. Thousands of O-rings are used in power plants to seal valves and around electrical cables and pipes. According to the report, these O-rings are not designed to withstand conditions that might result from a serious nuclear accident. Nuclear industry officials disagree, saying there is no significant safety risk from use of the rings.
Nuclear power critic Daniel Ford was reading the report on the shuttle Challenger accident when his mind locked in on the discussion of the failed O-rings. That sparked an investigation on the use of O-rings by the nuclear power industry, and the results were released this week by a group called Public Citizen.
``NASA's problem with the space shuttle was that they had a defective design for the O-ring joint and that they launched the shuttle when it was too cold,'' says Mr. Ford, former executive director of the Union of Concerned Scientists and coauthor, along with Robert Pollard, of the study. ``In nuclear plant accidents the main problem is that it would be too hot for the O-rings.''
Industry spokesmen disagree, and, while admitting that some O-rings might fail, point out that nuclear power plants are specifically designed with back-up systems to guard against equipment failure.
``I think it is disgraceful to raise the Challenger tragedy in order to create an unwarranted public fear,'' says Carl Goldstein, vice-president for media at the US Committee for Energy Awareness.
O-rings look like rubber doughnuts, and come in hundreds of sizes to match as many applications. They are used on waterproof watches to prevent water leakage around the watch stem, and in automobile brake systems to keep the brake fluid from seeping out when you step on the pedal before a stop. The rings are designed to fit in precisely machined grooves and to deform under pressure, changing their shape to seal off any possible leaks.
Loring Mills, vice-president for nuclear activities at the Edison Electric Institute, says there ``is not a single seal in a power plant that, if it failed, would cause a major accident. We do not apologize for using them, . . . we need an elastic material to form a good seal.''
The report relies on government studies and nuclear plant operating data to substantiate claims of potential failure. Hundreds of O-ring problems have been reported to the Nuclear Regulatory Commission (NRC) by power plant operators. A number of government studies have also pointed out potential problems, including a test in 1977 demonstrating that hot steam escaping from a serious reactor accident could leak past the O-ring seals protecting electrical systems and cause short circuiting. According to Ford, without a functional electrical control system, plant operators would be unable to make full use of safety measures needed to prevent a meltdown from developing.
A nuclear plant accident could generate temperatures between 500 and 1,300 degrees F.; 5,000 degrees F. could be reached in the unlikely case of a full-scale meltdown. These high temperatures, combined with potential radiation damage and high pressure levels, exceed O-ring limits set by manufacturers.
Ford and Mr. Pollard point out that containment buildings are pierced in hundreds of locations by cables, pipes, and doors -- all of them sealed by O-rings. They call for the NRC to close down those reactors located in urban areas because these O-rings could fail and cause the release of radioactive gas in the event of a serious accident.
Industry spokesmen claim that safety measures would be taken before reactor temperatures climbed to dangerous levels, and that rubber O-rings are not the only type of seal used in critical areas.
``There is no denying that seals can fail,'' Mr. Goldstein says. ``We know that, and the industry is seeking improvements. But you have to go through quite a few `what ifs' to get to the fears raised in the report. . . . It is misleading and totally incomplete.''
Joan Claybrook, president of Public Citizen, says the group is considering a petition to the NRC. ``[Petitioning] is the only way to force them to pay attention. Public exposure of the issue and actual petitions that trigger the mechanisms within the agency for action are the only ways to get them to do things,'' she says.
NRC officials say they are studying the O-ring issue, but their concerns do not involve a major safety risk.