By CP Staff
By Olivia LaVecchia
By Chris Parker
By Jesse Marx
By John Baichtal
By Olivia LaVecchia
By Jesse Marx
By Olivia LaVecchia
"Defense in depth"--the premise that each containment system is backed up by another containment system, which has its own backup, and so forth--is the principle at the heart of the nuclear industry's safety argument. Coincidence will have it, however, that the steam generator is one place where that rule doesn't quite apply. To protect the costly machine from overheating, engineers built into it a special vent designed to pop under pressure and release steam to the outside. When a tube breaks, that means highly radioactive steam goes out the roof--which is exactly what happened in 1979 at Prairie Island.
And 1979 was no fluke. In 1992, the NRC's then-director of nuclear reactor regulation, Thomas Murley, wrote in an internal memo that "there is a general acceptance that steam generator tube rupture events appear to be unavoidable." (Having just visited several reactors in Europe, Murley also noted that "it was clear that the U.S. lags behind the major European countries in terms of the scope of inspection.")
No cases of steam generator tube ruptures leading to catastrophic accidents are known, though the Mihama plant in Japan--whose generator was not made by Westinghouse--came awfully close in 1991. There, water rushed through a broken tube so fast the plant had to activate its emergency cooling system; some of that system's valves malfunctioned too, and technicians scrambled for some 45 minutes to arrest what could have been a meltdown.
And only a single tube broke at Mihama, an accident the steam generator is built to withstand. Multiple ruptures, by contrast, represent a "beyond design basis" condition, one where all bets are off. Though no one has wanted to contemplate the effects of such an incident, NRC Commissioner Kenneth Rogers told an industry symposium in 1988 that the scenario was entirely conceivable: If many tubes were deteriorating, as they were, it stood to reason that several could break at the same time. "In essence," he said, "we have a loaded gun, an accident waiting to happen."
So far, the NRC has taken a wait-and-see attitude to all this--occasionally asking for stepped-up inspections, yet allowing plants with severely degraded generators to continue operating. Last June, the Prairie Island Coalition asked the NRC to suspend NSP's license until the utility had inspected all of its tubes with state-of-the-art equipment. Russell notified the group that the petition "has not identified any safety issues warranting immediate action at the Prairie Island Nuclear Generating Plant... As provided by [federal law], NRC will take appropriate action on your Petition within a reasonable time." The group is still waiting.
NRC regulations, like any other kind, are not about safety at any cost. If the possibility of a particular kind of accident is deemed tolerably remote, or if contamination of people and the environment is kept within a certain limit, companies can't be forced to go to huge lengths to avert it. Thus, for example, there isn't much noise in the industry over the possibility that some of the cracked steam generator tubes may be leaking--which the documents indicate they do--because the amount of liquid is small enough to stay under a permitted "administrative leak rate" that works out to a gallon per minute at Prairie Island. (Interestingly, the 1992 memo from the NRC's Thomas Murley noted that limits on such releases were far stricter in Europe than in the U.S.)
And even the rules that govern when a utility needs to worry about steam generator cracks are up for changes. Utilities have long been telling the NRC that regulations written in the 1960s and '70s, for a whole different set of technical problems, are forcing them to go through unreasonable amounts of repairs and down time. "They are looking for some relief [from] a very conservative rule," says the commission's Sheron. "We've been dealing with that on a case-by-case basis, so we thought maybe we should promulgate a new rule." Sheron won't say what the new specifications will entail, and insists that "no one's getting a free ride here." But he knows, like any other federal employee, that the Clinton administration and Congress want agencies to "reengineer" themselves in a more customer-friendly manner. At the NRC, this has resulted in a promise of "cost-beneficial licensing actions," which translates as getting rid of particularly expensive requirement. In its 1994 annual report, the commission came right out and announced that "the industry [is] in the best position to identify which regulations impose a heavy economic burden with little commensurate safety benefit."
The phrase "economic burden" rings especially loud where nuclear plants are concerned because, as utilities have discovered over the past 20 years, the power once touted as being "too cheap to meter" is nothing of the sort. No new reactors have been ordered in the U.S. since 1978, and according to a 1995 study by the consulting firm Washington International Energy Group, three-quarters of utility executives surveyed didn't think their companies would ever build another nuclear plant. Even Hazel O'Leary, the former NSP exec who now heads the Department of Energy, told Congress in 1993 that "the costs of nuclear power, if you include new construction, are not competitive." Against that backdrop, the extra cost of deteriorating steam generators (and other reactor parts) may be the last straw for some plants. At least one utility, Oregon's Portland General Electric, has already decided to just chuck the whole thing. For years, citizen groups demanded the shutdown of the Trojan reactor, and PGE resisted. In 1992, it turned around and closed the plant--in large part because of the escalating cost of steam generator repairs.