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Glass strategy: Hanford’s enhanced waste glass program
The mission of the Department of Energy’s Office of River Protection (ORP) is to complete the safe cleanup of waste resulting from decades of nuclear weapons development. One of the most technologically challenging responsibilities is the safe disposition of approximately 56 million gallons of radioactive waste historically stored in 177 tanks at the Hanford Site in Washington state.
ORP has a clear incentive to reduce the overall mission duration and cost. One pathway is to develop and deploy innovative technical solutions that can advance baseline flow sheets toward higher efficiency operations while reducing identified risks without compromising safety. Vitrification is the baseline process that will convert both high-level and low-level radioactive waste at Hanford into a stable glass waste form for long-term storage and disposal.
Although vitrification is a mature technology, there are key areas where technology can further reduce operational risks, advance baseline processes to maximize waste throughput, and provide the underpinning to enhance operational flexibility; all steps in reducing mission duration and cost.
Seong-Wan Hong, Beong-Tae Min, Seong-Ho Hong
Nuclear Technology | Volume 191 | Number 2 | August 2015 | Pages 122-135
Technical Paper | Fuel Cycle and Management | doi.org/10.13182/NT14-84
Articles are hosted by Taylor and Francis Online.
Steam explosions by the interaction of molten corium with water have been studied extensively because they may have the potential to impact the integrity of the containment. Since breakup and fragmentation processes during premixing are important mechanisms that influence steam explosion behavior, the particle size distribution characteristics on fuel-coolant interaction (FCI) have been investigated in the TROI (Test for Real cOrium Interaction with water) test facility.
The data characteristics indicate that FCI characteristics depend upon the composition of the prototypic corium material, and the particle size of the debris is related to the intensity of the dynamic pressure produced by an explosion. The mass mean diameters of the debris produced by explosive compositions were less than that of the nonexplosive compositions. A mass mean diameter of 2 mm was found to be a boundary size produced by a steam explosion of corium. The particle sizes of the molten corium involving a steam explosion were shown to be mainly 3 to 6 mm depending on the material and composition, but the size distribution shifted to smaller sizes if a steam explosion occurred. Small corium droplets of less than ∼3 mm did not seem to contribute to a steam explosion owing to solidification at an early stage before the explosion, but large droplets contributed due to their liquid state.
Zirconia, with the largest fusion heat, has almost always exploded, and the explosions have been energetic, while the eutectic composition (UO2/ZrO2 = 70/30 at weight percentage) frequently exploded. On the other hand, noneutectic compositions rarely exploded, even though the heat of the fusion was very similar to the eutectic composition that frequently exploded. The main reason why noneutectic corium compositions do not explode seemed to be that they undergo solidification by forming a “mushy zone” with a small freezing temperature range. To determine whether noneutectic corium melts cooled down through the mushy zone, particles of this composition were analyzed from the surface inward using a scanning electron microscope, an electron probe microanalyzer, and X-ray diffraction. However, all particles were found to have a homogeneous solid solution. The large particles showed the typical solidification shapes of a general molten material. The small particles generally had only a few small pores and small cracks. The morphologies of the large and small particles were found to be similar.