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-~.~M= U.S. nuclear weapons pro- - - gram, there have been eight known accidental criticalities and two fatalities, both in 4 New Mexico in the mid- ~j > 1940s. Lately, there have been a few close calls (technically, "criticality infractions"). In - late September 1994 a work- er drained liquid Erom a tank at Rocky Flats, leaving five liters of highly concentrated plutonium solution in what - l the Defense Nuclear Facili- ` ties Safety Board called "a potentially unsafe geometry." There was also a near miss ~ ' ` ~ t' ~ ~ several years ago at the Ida- _ . m ho site, when some fuel bun- ~ tiles suspended in a pool fell ' LL co the bottom near one an- r ~ other. i ~ t~.~ ? During the mid-1980s, 1 W Hanford's plutonium-finish- ~~r ' ~ ~ ing plant was declared a ~ ~ serious eatthquake risk. One ~ PLUTONIUM "BUTTON" waz Hanford's sole product. Consisting mainly of the isotope pluto- anal sis found that a tem- . nium 239, the buttons were sent to be machined into bomb parts in Colorado. The metal must be y ' handled in glove boxes, such az the one shown here, because extremely minute quantities of the blot could rend a construc- metal in the lung can induce cancer. Currently the DOE has no long-term plans for its plutonium. non joint, possibly releasing plutonium compounds into the air. This threat has been ' gredients may be different even in dif- Plutonium sir in storage ac Hanford, pushed into the background by other ' ferent patts of individual tanks. I (much of it under tight security in vaults risks and changing priorities. The "tank-waste characterization" , at the fmishing plant. In addition, an es- Plans for disposing of the scavenged program, which seeks to specify what is cimated LS tons are believed to be in plutonium-not only at Hanford but in the tanks, has been a lightning rod ''waste dispersed in the soil around the also at Rocky Flats, Savannah River for criticism. "They've been doing this site or in pipes and filters in its facilities. and Pantex-have been stymied by the for 10 years and have spent $260 mil- Plutonium exists in many forms at DOE's inability to decide whether pluto- lion, and only now are they at a point Hanford. There are tiny scraps of it, nium should be hoarded for possible where they can take samples at a tea- and it is present in sludges and in 3,500 furore use. `The largest Eactor atfetting sonable rate," says William R. Swick, liters of nitrate and other solutions. At the cleanup scope relative to plutorium senior evaluator for energy and science the finishing plant, workers have begun is the absence of a national polity on issues at the Richland bureau of the cleaning out countless air ducts, filters whether some or all of the plutonium at General Accounting Office (GAOI. Sam- and "glove boxes" where the metal was Hanford is an asset to be maintained in i piing of the tanks is hindered by the extracted and handled. They are also inventory or a waste to be disposed of," high radioactivity and toxicity, which bringing plutonium to the finishing plant wrote analysts Steven M. Blush and make access difficult and dangerous, from other Hanford sites, to consoli- Thomas H. Heitman in a recent con- and by the waste's multiplicity of physi- date the element iu one place. Most of gressional report on Hanford's cleanup. cal states and ongoing chemical activity. it will be baked into oxides or other tea- ~ The DOE spends about $g2 million a sonably stable, powdery forms for long- ~ year maintaining the plutonium just at Deadly Bullion term storage. The work is slow and ex- Hanford's finishing plant. pensive because plutonium is extremely ntil recently, plutonium was Han- dangerous; a mere 27 micrograms in Costly Canyons Uford's raison d'etre, but now it is ~ the lung can bring about cancer. just another big and expensive head Workers must also be mindful of the ''T"he reprocessing plants, where plu- ache. For 40 years, pluronium nitrate metal's critical mass-which can be as j tonium was exrracted from irradi- solutions were brought from the repro- ` little as 11 kilograms. If the critical aced fuel before being sent to the finish- cessing facilities to the on-site plutoni- 1 mass is allowed to accumulate in one ing plant, are another financial burden. um-finishing plant, where the element place, a spontaneous fission chain teat- Hanford has five of them, each in con- , was converted into dull, leadlike "but- i tion known az a criticality can occuy re- Crete buildings called canyons. Some of tons," about the size of hockey pucks, leasing a lethal shower of neutron and the canyons aze comparable in size to ' for farther machining. Eleven tons of (gamma radiation. In the history of the the Empire State Building, if it were ly- 92 SCIENTIFIC AMERICAN May 1996 Han{ord's Nuclear Wasteland