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More nuclear waste highway bound for Savannah River Site

By Michael Hopping

Another round of weapons-grade plutonium shipments to the Savannah River Site (SRS) has begun, according to a recent announcement from the U.S. Department of Energy (DOE). At the completion of the transfer, the K-Area Material Storage facility at SRS will house approximately 13 metric tons of “non-pit” (never weaponized) plutonium, says Allen Gunner, an SRS-based DOE manager.

This supply, Gunner adds, is in addition to 38 tons of U.S. weaponized plutonium and 14 tons of non-weapons grade plutonium to be removed from military stockpiles as part of a deal struck with Russia several years ago. At some point, that material may also be South Carolina bound.

In all, the current non-pit shipping campaign involves 2,511 packages of plutonium metal and oxide from the Hanford site in Washington State, Los Alamos, and the Lawrence Livermore National Lab in California. The containers will travel in unmarked armored tractor trailer rigs known as “Safe Secure Transports,” driven and guarded by armed federal personnel. Routing details are classified and state officials aren’t notified when a shipment passes through.

The DOE’s plutonium drivers don’t pick their own routes to SRS. Instead, federal dispatchers direct them with RADTRAN or TRAGIS software. These routing programs take several factors, including road conditions, accident rates, population centers, etc., into account. RADTRAN and TRAGIS vary in the weighting of such factors, but the routes they select are likely to be similar.

John Sticpewich, a retired international oil and gas geologist living in Asheville, N.C., has access to TRAGIS software. When Sticpewich entered the plutonium origin and destination information into the program, the resulting itineraries surprised him. Columbia appears only as a third choice alternative from Hanford. “What’s striking about the maps is that all but one of them converge on Atlanta,” he says.

But for those living along the I-26 corridor, rejoicing may be premature. Ninety percent of the material scheduled for transfer resides at Hanford, and RADTRAN may value Atlanta more highly than does TRAGIS. The result: it could just as easily route some of the shipments through Columbia.

Spinach Cans

Twenty-two lbs. of plutonium-239 is enough to go critical under certain circumstances, so DOE limits the amount in any single package to about nine and a half pounds. The specific transport and storage container DOE chose is a layered stainless steel drum system.

Plutonium rests inside a primary and secondary containment vessel: nested stainless steel tubes wrapped by a half-inch lead jacket. This assembly is placed in the “overpack,” a 35-gallon stainless steel drum with an inner padding of Celotex rings. (Celotex is a type of fiberboard with a consistency reminiscent of stiff felt. It is commonly used to sheath houses.) Together, these components comprise a “9975 package.”

Federal regulations require containers and casks for highly dangerous or radioactive materials to meet standards for damage resistance in accident conditions. They must not release their contents after a series of misfortunes including a 30-foot drop onto an unyielding surface, puncture by a stationary iron pin and a 30-minute engulfing fire burning at 1475° F. The tests are designed to account for the possibility of a severe transportation accident, such as a container being hit by a train or a fiery tunnel crash involving multiple vehicles.

Bureaucratic snafus delayed the 9975’s Type B certification for years. It was eventually granted in 1999, but trouble soon followed. Someone noticed that when a 9975 was dropped on the lid end at a 45-degree angle, the outer lid opened up. Integrity of the steel drum is critical to the container’s fire resistance. Celotex burns at temperatures above 350° F and lead melts at 622° F.

Type B certification was withdrawn. Testing at the Westinghouse Savannah River Company confirmed the severity of the problem. Lids on the 9975 routinely popped open like Popeye’s can of spinach when the package was dropped at an unfavorable angle. The report concludes, “conventional clamp ring closures are not suitable for packages where the weight ratio of the internals (containment vessels, contents, shielding, etc.) to the gross package weight is greater than 50 percent … the failure rate for packages exceeding this limit is nearly 100 percent for the packages evaluated.” The combined weight of lead and stainless steel “internals” in the 9975 virtually guaranteed lid failure on the regulatory drop test.

Talk about embarrassing. The fault was remedied by redesign. A series of bolts now secures the lid. The 9975 was recertified in 2001 and has been continuously certified since then, although the redesigned model was not subjected to the series of Type B damage tests.

In fact, it appears that the 9975 was never subjected to the test series. James Giusti, a DOE public affairs officer at SRS told me, “Drum and fiberboard overpacks were already a mature technology at the time of the 9975 certification testing, with extensive testing dating back for over twenty years, at Savannah River Site, Oak Ridge National Laboratory and Sandia National Laboratory. The 9973 and 9975 were so similar to the earlier, certified packages that extensive additional testing was not necessary.”

The 9973 container Giusti mentioned is a smaller, 30-gallon, drum system without lead shielding. At least one 9973 was put through the regulatory series of damage tests in 1994 and survived. In view of the subsequent problem with the 9975, the lack of lead in the 9973 may have made a critical difference. An unloaded 9973 package weighs only 187 lbs., less than half that of a 9975. According to the Westinghouse findings, a 9973 would likely retain its lid when dropped at an angle.

I asked Gunner, who manages the 9975 package program at SRS, what was stored or moved in the old model 9975s before the lid problem was discovered. He said that although the 9975 was available for use, it wasn’t actually pressed into service until after the lid problem was corrected. According to him, no lid failures have occurred with the bolted lid model. The old-style 9975 isn’t used to store anything requiring a Type B container.

Cross country

People concerned about the nation’s diesel supply may be relieved to learn that 2,511 Safe Secure Transport (SST) convoys may not be required to move the plutonium across country to South Carolina. A DOE document states that as many as ten 9975s were aboard the SSTs that transported a different fissile element out of South Carolina a few years ago. If plutonium shipments are similarly consolidated, the number of SST trips could be reduced to less than 300.

For those concerned about the consequences of a severe accident involving an SST, this prospect is less welcome news. Worst case scenarios worsen as more plutonium is added to a wreck.

DOE’s announcement of the current plutonium shipping campaign has this bit of bureaucratese to offer on the risk of serious highway accidents:

“DOE evaluated the impacts of a severe accident while transporting plutonium oxide material in Type B shipping containers in Safe Secure Transports (SSTs). The hypothetical accidents modeled for the impact assessment involve either a long-term fire or tremendous impact of crushing forces. In the case of crushing forces, a fire would have to be burning in order to spread the plutonium as modeled. These accidents were assumed to cause a ground-level release of 10 percent of the radioactive material in the SST. These accidents fall within the Nuclear Regulatory Commission’s severity Category VIII, with an accident frequency in rural areas of about 1 x 10-7 per year (once in 10 million years). DOE estimated that if such an accident were to occur in an urban area as many as 114 cancer fatalities could result. In addition, the accident itself would cause a number of non-radiological fatalities, depending upon the specific circumstances.”

This determination is based on arbitrary DOE assumptions dating to 1977. They aren’t specific to plutonium, the 9975 container, or the present shipping campaign.

DOE classifies hypothetical radiological transport accidents on an eight-point scale. Category VIII is the most severe. An appendix to a Clinton-era environmental impact statement defines a Category VIII accident: “For the truck and air analysis, the eight accident-severity categories defined in the Nuclear Regulatory Commission’s (NRC) Final Environmental Statement on the Transportation of Radioactive Material by Air and Other Modes (NUREG 0170, December 1977) were used… . The most severe category (Category VIII) represents a large crush force, high-impact velocity, high puncture-impact speed, an 88-kilometer [km] per hour (54.6-mile [mi] per hour) collision into the side of the vehicle and a 982-degree Celsius (°C) (1,800-degree Fahrenheit [°F]) fire lasting 1.5 hours to produce a release of the material (plutonium, highly-enriched uranium, or tritium). The release fractions for Category VIII accidents were conservatively estimated to be 0.1 for all types of materials analyzed.”

Translated to English, DOE’s worst case pencil and paper accident scenario involves a tractor trailer collision at a speed of 55 mph and a hot fire, but one that only burns for an hour and a half. DOE’s calculation of 114 cancer fatalities is derived from the arbitrary Category VIII assumption of a 10 percent release of radioactive material. Whether that number has any relevance to the 9975 container, a packaging system that didn’t exist in 1977, is anybody’s guess.

Thankfully, to date, there have been no publicly acknowledged accidents involving SSTs hauling 9975 packages. This testifies to the skills of SST drivers but has no bearing on the reasonableness of the DOE’s projection of a severe accident frequency of “once in 10 million years” or the ability of an SST to retain 90 percent of the radioactive cargo it contains.

When Sticpewich looks at the schematic drawing of the 9975 and imagines what might happen if a load of 9975s is hit by one or more 80,000 lb. tractor trailer rigs traveling at highway speed, followed by a fire such as the inferno that closed an Interstate-5 tunnel in LA for more than two days in October, he’s not optimistic. “I fear the durability of these containers may be a real concern.”

Gunner is more confident. When I suggested that the 9975 doesn’t look like a can with much of a chance in a smashup featuring hurtling big rigs and fire, he replied, “These containers aren’t going to open up in a wreck.”

Hopefully, we’ll never have to find out.