Hanford reactor's safety is questioned.

Hanford reactor's safety is questioned

Since the catastrophic Chernobyl reactoraccident in April (SN: 5/3/86, p.276), at least six studies have been commissioned or undertaken to assess the safety of a U.S. defence reactor at the Hanford site near Richland, Wash., which bears some Chernobyl-like attributes. Three of these assessments have already been published. The most recent, released last week by the U.S. General Accounting Office (GAO), found that many systems and components in the 23-year-old "N-Reactor"--one of the two reactors at the Hanford site -- are deteriorating to a point where they could jeopardize safety. GAO estimates that correcting those deficiencies and replacing aging parts could cost the federal government as much as $1.2 billion.

Still another report, due out soon, willacknowledge there are still many uncertainties as to whether the plant's design features are potentially serious liabilities in a core-melt accident, according to Robert Barber, director of nuclear safety for the Department of Energy (DOE). Such an accident occurred both at Pennsylvania's Three Mile Island #2 nuclear plant and at Chernobyl. Though two earlier DOE studies found no major safety problems, Barber told SCIENCE NEWS, neither appraisal evaluated N-Reactor's design in great detail or considered how the plant might respond in a severe core-melt accident.

The N-Reactor's lack fo a domed containmentbuilding to trap radioactive materials emitted during a serious accident is one of the design features it shares with the Chernobyl plant. According to Rep. James Weaver (D-Ore.), a recently disclosed report written a number of years ago by the Atomic Energy Commission, DOE's predecessor agency, says the plant's builder chose the filtered "confinement" system -- instead of a more substantial "containment" building -- "because of its lower cost." Weaver notes that a federal advisory committee on reactor safeguards reported at about the same time, however, that "Several of its features raise questions as to the possibility of larger releases from a severe accident than are believed credible for commercial power reactors."

One of those questionable features inthe confinement system's reliance on aerosol filters to limit radioactive releases, according to Washington, D.C.-based reactor-safety analyst Susan J. Niemczyk.

Until about 10 years ago, she says, severe-accidentmodels tended to ignore the quantity of radioactive aerosols that might be released, but recent studies have shown that a pressurized-water reactor, like N-Reactor, might generate tons. Meanwhile, experience has shown in reactor cleanup systems where filters are used that significant filter clogging can occur after just a few dozen pounds of aerosols enter, she adds. With the N-Reactor's system of four filters, "it probably wouldn't take a whole lot of aerosols [during a severe accident] before you'd risk clogging the filters, failing them and then begin pumping [radioactive particles] directly into the environment," she says.

Niemczyk also believes that computercodes recently developed to better gauge a commercial reactor's potential radioactive emissions during a severe accident (SN: 4/20/85, p.250) "would not be appropriate for analyzing the Hanford N-Reactor because of the completely different configuration [from other U.S. reactors] of its core." Like the Chernobyl plant, the Hanford reactor core is made up of more than 1,000 separate fuel tubes--each in its own miniature reactor vessel -- instead of a single huge reactor vessel surrounding all of the fuel rods together. Without updated codes, she says, "it's not obvious how [DOE] assessed the Hanford reactor's safety."

DOE's Barber acknowledges that thealready-published DOE reports fall short on this count, but adds that in the soon-to-be-released report, "Our reviewers have raised some of the same questions" as Niemcyzk has.

In contrast to these design and analyticalquestions, the new GAO report focuses on more obvious problems that signal age -- valves that are becoming worn, graphite that is becoming misshapen, unreliable mechanical systems. In fact, it was largely his concern about having to fix these nuts-and-bolts types of safety-related problems that prompted Sen. Mark Hatfield (R-Ore.) last week to say, "I am convinced that the N-Reactor should be shut down by 1995 for economic if not safety reasons." Toward that goal, on Aug. 7 he marshaled legislation through his subcommittee on energy and water that would strike $21 million from DOE's 1987 budget -- money DOE had earmarked for beginning renovations to extend the life of the reactor well into the next century. The legislation also instructs DOE to consider closing the plant.

N-Reactor's main function is to produceplutonium for nuclear weapons. Because plutonium is being stockpiled, Weaver says the plant is not needed.

DOE disagrees. Not only does the reactorproduce electricity at a cost that is below the national average, says DOE spokesperson Jack Vandenberg, but also "we feel it is needed to produce plutonium. However, since supplies of plutonium are a classified matter, we cannot discuss that in any detail."