COLUMN ONE : A Nuclear Drama Is Brewing : Composition of radioactive waste in storage tanks at Hanford, Wash., worries U.S. officials. The potential for disaster is being assessed--but too slowly, some fear.

Just before dawn one day last month, in a million-gallon caldron encased in reinforced concrete and buried six feet underground, a vile brew of radioactive waste heaved and gurgled, and then--right on schedule--emitted a huge burp of hydrogen.

For reasons that scientists do not understand, this unnerving drama has been recurring every 80 to 109 days for the past 10 years. From seething sludge at the bottom of Waste Tank 101-SY at the sprawling Hanford U.S. nuclear weapons production site here, hydrogen gas rises and accumulates until the pressure breaks through--or around--a thick crust floating on the surface.

Precisely what malevolent chemical reactions are churning in the bottom of the gigantic vessel experts do not know, but it is no mystery that a spark in the concentrated hydrogen-and-nitrous-oxide gas could start a fire and set off a chain reaction that would rupture the tank’s dome and spew out radiation--with potentially dreadful consequences.

After having been kept top secret for 13 years, Waste Tank 101-SY’s disturbing case of indigestion has become the No. 1 priority for government and industry waste managers who are baby-sitting 228 huge tanks of high-level radioactive waste produced during the more than 40 years that the government has produced plutonium and tritium for nuclear weapons.

Leo Duffy, the Energy Department official now in charge of the massive weapons facility cleanup, estimates that emptying the Hanford tanks and permanently disposing of their contents may eventually cost $25 billion, and possibly as much as $200 billion if the problem continues into the next century, as now is expected.

For now, understanding and stabilizing Waste Tank 101-SY is the immediate goal.

“A spark could really set it off,” said Ronald Gerton, director of the waste management division at the Energy Department’s Richland operations office. “There hasn’t been a spark so far, and we have been lucky. Well, the Challenger shuttle was lucky, too, for a number of flights, and then it got unlucky. We have to get this taken care of before we get unlucky.”

But the house-sized 101-SY is hardly the only underground vessel here that needs special attention.

Twenty-two other such tanks at Hanford have similar, though much less dramatic, symptoms of hydrogen accumulation. And yet another 22 are laden with chemical compounds that could cause an explosion powerful enough to blow them open if they become overheated by radiation.

Scientists also believe that another 66 of 149 single-shell tanks that were in vogue at Hanford before the appearance of double-walled vessels in 1980 may have sprung leaks under the punishment of heat and corrosion, allowing upwards of 750,000 gallons of the dangerous mixture to drain into the ground.

All are legacy of a time when the premium on plutonium and tritium production for nuclear warheads dwarfed considerations of long-term safety and protection of the environment. To save time and energy, officials of the old Atomic Energy Commission ordered high-level waste--treated with water and lye--stored in single-shell carbon steel tanks at Hanford. All that came in spite of stern warnings from safety experts as early as 1948.

Confronted with the prospect of massive leakage problems, officials at Hanford and a Savannah River, S.C., tritium production site eventually turned to double-shelled tanks, with two walls of carbon steel surrounded by reinforced concrete. Hanford has 28 of them, including Waste Tank 101-SY, and Savannah River has 51.

Although the 34 million gallons of waste in the South Carolina tanks contain more than 75% of the total curies of radiation that still are in temporary storage from the decades of U.S. bomb-production, Hanford’s problems are far more daunting. Over the years, the complex here in southeastern Washington employed three different chemical processes for stripping plutonium from the fuel rods of its production reactors, each creating its own characteristic wastes.

The stuff deposited by different generations has become mixed. Material from leaky old tanks has been transferred into modern double-shelled containers, and over the years, some vessels have been “mined” to recover uranium for recycling. They have had strontium and cesium chemically stripped out by the lye or ferrocyanide; and to reduce waste volume and the danger of leakage, they have been heated and dried.

Although scientists have a good idea of what has been put into the various tanks, they have little confidence that they understand the chemical reactions taking place after the mixing and treatment over the years. “The whole operation has been destabilized since about 1954,” said Robert Alvarez, an investigator for the Senate Government Affairs Committee, which has kept a close eye on the tanks over the past year. “They have been flirting with a dangerous situation since that time.”

Estimates for the cleanup of the Hanford site, including the decommissioning of its eight plutonium production reactors, run as high as $57 billion. Projected costs for cleaning up the entire weapons complex go to $91 billion over a 30-year period and $200 billion for a 60-year period--not to mention as much as $52 billion worth of modernization over the next 20 years.

Waste experts once believed that the mayonnaise-thick sludge in the bottom of the temperamental tank 101-SY formed one huge bubble that rose through the liquid to be trapped beneath the crust that was floating on top. For six years, they tried to relieve the pressure by periodically “lancing” the crust with a jet of water or steam or a burst of air, or by dropping a weight through it.

Not only did the practice fail to produce results, scientists since have found evidence that the air and steam injections may actually have made the episodes worse, and that the operation itself risked causing a disastrous spark.

The experts’ latest judgment is that the possibility of an instantaneous explosion is so far-fetched that it defies credibility. What does cause them acute concern, however, is the possibility that a fire might be set off in the crust.

“We know that it has organic materials that would provide fuel, and so the stuff might burn like black powder,” Gerton said. “That could generate enough energy and heat to cause the dome to fail and open the tank to the atmosphere.”

To understand the reactions that are generating the hydrogen, scientists need top-to-bottom samples that would enable them to construct a chemical model of the tank’s behavior.

The burp in October vented the gas sufficiently that officials hoped to have several weeks in which to work with remote-controlled equipment to retrieve samples. But by last week, they had given up hope for now of getting beyond the crust because the possibility of creating a spark had not been eliminated beyond doubt. While they may be able to get material from the crust before the pressure buildup makes it prudent to suspend work, they will have to wait until a later burp before trying to get critical core samples yielding the needed cross section of the crust and the salt-cake-and-sludge bottom.

There will be no drill operation in the tank, Duffy said, until tests demonstrate that there is no possibility of igniting the crust. While the restless behavior of Waste Tank 101-SY compels immediate attention, at least 22 older tanks that have been doctored with 160 tons of ferrocyanide between 1954 and 1957 pose a special explosive potential of their own.

The Energy Department stresses that the temperature in these tanks is now some 300 degrees below the level that is considered explosive--and still is dropping. And while officials conceded three years ago that if an explosion did occur, it could be powerful enough to breach filters and release a radioactive aerosol into the atmosphere, they maintain that beyond Hanford’s boundary, the additional exposure would be comparable to natural radiation levels.

Still, the department’s official estimates of potential magnitude--contained in a 1987 environmental impact statement--have been seriously challenged. A study by the Battelle Pacific Northwest Laboratory, kept secret for five years before it was made public by the Senate Governmental Affairs Committee last year, concluded that a ferrocyanide explosion could be equivalent to 36 tons of TNT. The disclosure prompted several investigations.

A just-completed analysis by the General Accounting Office, the congressional watchdog agency, found that such an accident would blow a large hole in the tank top and the earth overhead, releasing a cloud containing highly radioactive cesium-137 and strontium-90.

“Such an explosion would be a major accident,” the GAO said in a report to the House Government Operations subcommittee on environment, energy and natural resources. The document warned gravely of the possible “contamination of large areas within and possibly beyond the Hanford site boundaries, in addition to human health effects.”

While the GAO report did not dispute the Energy Department’s contention that the chance of an explosion is slim, it said that work performed by the Westinghouse Hanford Co. and Pacific Northwest Laboratory “indicates that, although the probability of an explosion may in fact be low, not enough is known about the waste in the single-shell tanks to rule out the possibility of a spontaneous explosion.”

Washington State University Prof. George W. Hinman, who served as a consultant to the GAO study, calculated that an explosion in one of the tanks might produce off-site radiation exposures 100 times those that the Energy Department estimated in 1987.

Because Hinman assumed that greater amounts of cesium and strontium would be dispersed in an explosion, he calculated that off-site exposure to airborne radiation could theoretically be as high as 7.3 rem. The National Research Council predicts that prolonged exposure at that level would produce one additional case of cancer for every 160 persons exposed.

An ad hoc Energy Department task force--the last in a succession of panels reviewing the tanks in recent months--took issue with the radiation dose estimates, though it agreed with broad aspects of the GAO’s findings.

Meanwhile, Energy Secretary James D. Watkins has announced that the department will now proceed to prepare a supplemental environmental impact statement on the entire Hanford tank situation.

The intense new assessment, he said, is not an indication that federal officials have changed their opinion that a significant radiation release from any of the tanks is only a remote possibility. Instead, he characterized the new review as a step “to assure the people of Washington and Oregon that the Department of Energy is committed to an open and frank analysis and discussion of the problems presented by the radioactive and hazardous wastes currently stored in the Hanford Site’s tanks.”

Although there is less mystery about the ferrocyanide-treated tanks and the rest of the old single-shelled vessels than there is about the bizarre 101-SY, officials urgently want extensive core-samples from them as well.

Indications are that temperatures in the ferrocyanide tanks are no more than 135 degrees--well below the estimated 445-degree level that scientists believe is necessary for a chemical reaction to begin. But the readings are taken along only one vertical line from the surface to the bottom of the sludge--leaving open the possibility that dangerous “hot spots” could exist undetected across the 75-foot diameter of the tank.

While the salts in the old tanks are saturated with moisture, the waste in most of them is no longer liquid in the conventional sense. Nearly 100 of them have already been “stabilized” by evaporating the liquid, which was low in radiation and pumped out, leaving salt cake and sludge--and a much-reduced danger of leaks. Under an agreement among the Energy Department, the Environmental Protection Agency and Washington state, the rest of the single-shell vessels must be stabilized by 1996.

To complete the assessment, the department’s first five-year cleanup plan calls for acquisition of at least two core samples from each of the single-shell tanks.

Officially, the timetable calls for completion of the sampling and analysis by the autumn of 1998, but last month the Defense Nuclear Facilities Safety Board, created by Congress as a watchdog over the massive cleanup program, advised Watkins that will not be soon enough.

In a memorandum to the energy secretary, board Chairman John T. Conway said the department’s responses to a series of recommendations on the tanks were “not adequately responsive” in several respects and the sampling needed to be “greatly accelerated.”

“The proposed schedule whereby analysis of two core samples from each single shell tank is to be completed by September, 1998, is seriously inadequate in light of the uncertainties as to safety of these tanks,” Conway said. “Furthermore, additional samples are required at several radii and at a range of elevations for the tanks containing ferrocyanide. . . .

“The schedule for the program on study of the chemical properties and explosive behavior of the waste in these tanks is indefinite and does not reflect the urgent need for a comprehensive and definitive assessment of the probability of a violent chemical reaction.”

The formal schedule notwithstanding, Duffy said the Energy Department expects to have a solid idea by 1992 precisely what is in the tanks. About 45 of them, including those with the heaviest loads of ferrocyanide, have already been “sampled” with “non-intrusive” techniques such as sonic and infrared inspection and gamma spectroscopy.

Within the next six months, officials hope to complete tests to demonstrate that it is safe to take actual samples from the bottoms of the tanks containing ferrocyanide. Once the tanks can be sampled, the big question will be whether GAO consultant Hinman was correct in his belief that cesium and strontium are so concentrated that an explosion could produce a radiation hazard beyond the bounds of the reservation.

If Hinman is right, Hanford faces the staggering new problem of how to neutralize that threat. But if the Energy Department’s own estimates prove correct, the government can begin planning to empty all of the old single-shell tanks at last--either by using robots to remove the dry salt cake and sludge, or by reliquefying the material so it can be pumped out and melted with glass.

As Hanford awaited the October burp of Waste Tank 101-SY, authorities at Savannah River, S.C., started a series of electric pumps and sent water pulsing through a new billion-dollar complex that is supposed to make dangerous waste tanks a bad memory.

It was the beginning of an 18-month “cold” test, preparing for the day when a stream of intensely radioactive broth will be piped into a 1,000-degree melter along with a talcum-fine silicate to create deep-brown, obsidian-like logs of glass.

Once these “hot” operations begin, the Defense Waste Processing Facility is expected to make glass night and day for about 15 years. Unless there is an emergency, it will shut down only two or three times--whenever it becomes necessary to install a new melter.

Sealed in heavy stainless steel canisters, the 10-foot-long, 2-foot-diameter glass logs will be individually stored in a honeycomb of concrete underground. There they will remain until the government has a geological repository--which it hopes to locate deep in Nevada’s Yucca Mountain--ready for permanent disposal of its most radioactive bomb wastes, as well as spent fuel from commercial power reactors.

In preparation for the vitrification process, the 30 million gallons of liquid in Savannah River’s 51 tanks will be chemically stripped of their most virulent isotopes and piped away to be mixed into concrete and poured into heavy bunkers. The remaining 4 million gallons of sludge-turned-into-glass will be reduced to 7,000 canisters that will still crackle with radioactivity even after a thousand years.

Building on its experience in South Carolina, the Energy Department will soon be ready to break ground for a similar installation to glassify the sludge and salt cake from the bottom of Hanford’s 28 double-shelled tanks, and--one day, perhaps--the troublesome stuff in the old single-wall tanks as well.

The vitrification operation will be accompanied by a new generation of its own hazards. Byproducts from glassification of the Savannah River waste, for example, will include 50 to 70 tons of radiation-contaminated mercury and as much as 100,000 gallons of benzene, which must then be incinerated.

Although France, Germany and the Soviet Union have turned to vitrification as their prime means of stabilizing high-level waste, skeptics are concerned that the complexity of the material in the Hanford and Savannah River tanks will introduce unexpected problems.

“The claim that this is a tried and true technology is not true where this country is concerned,” Robert Alvarez, the Senate investigator, said.

Moreover, with the future of the long-delayed geological repository still uncertain, the logs of radioactive glass could wind up at Hanford and Savannah River indefinitely.

And considering DOE’s past difficulties in putting low-level waste into cement--thousands of barrels of radioactive concrete failed to solidify at Oak Ridge National Laboratory--there is still room to question the strategy for disposing of tank liquids.

Says Peter Johnson, waste expert at the Congressional Office of Technology Assessment:

“Standing on the evaporator tower at Hanford, you can look off in one direction and see the tank farms that have caused all the trouble, and in the other direction, you can see the concrete bunkers that are supposed to be part of the solution, and it appears that they are still only moving from one set of containers to another.”