Disposition Options for Hanford Site K-Basin Spent Nuclear Fuel Sludge

Abstract

This report provides summary-level information about a group of options that have been identified for the disposition of spent-nuclear-fuel sludge in the K-Basins at the Hanford Site. This study builds upon a review performed in CY1999 which established the current baseline for sludge retrieval and storage from K Basin. (a) Building upon this study, an expert review team was assembled to consider expert knowledge and project progress which has evolved since that time. The membership of this team is provided in Appendix C. This team outlined a revised set of potentially feasible alternatives which could be broadly classified as ambient and elevated temperature treatment methods. In considering the breadth of these methods, the team concluded that the presence of a high uranium metal content fraction was limiting the feasibility of several candidate methods. In other words, if some mechanism were available to eliminate or significantly reduce the uranium metal content, the range and efficacy of feasible treatment methods would be enhanced. Given these preliminary findings by the team, additional discussions were held with Flour Hanford senior project members to explore both the feasibility of separating a uranium metal stream and the congruence of potentially feasible treatment methods with other program interfaces and objectives. The selection of alternatives given in this report for disposition of the sludge is derived for this team effort. The product of each treatment option would be treated sludge that would meet waste-acceptance requirements for disposal as transuranic waste at the Waste Isolation Pilot Plant. The separated concentrated uranium stream would be treated by one of several methods identified by the team, which are beyond the scope of this report. K-Basin sludge is made up of degraded fuel, corrosion products, dirt, and other material that has accumulated in the basins through the 30-year fuel-storage mission. Sludge can be categorized by its location into pit sludge, floor sludge, canister sludge, knockout pot (KOP) sludge, and settler sludge. Pit sludge can be further categorized in accordance with the specific pit in which it resides. Key characteristics of this sludge that shape the selection of a path forward are: • U-metal (b) content ranging up to 5% for canister sludge (and greater than 50% for KOP sludge) • Plutonium content greater than 100 nci/gm, requiring controls for airborne alpha • Dose rates up to approximately 5 rem/h (higher for KOP sludge) • Fissile content requiring controls for the prevention of nuclear criticality. The treatment options that were considered can be divided into two groups-those that would be performed at ambient temperature and those that require elevated temperatures. The two (a) Sludge Treatment Analysis HNF-4097, Rev. 0, K. L. Pearce, NUMATEC Hanford, 4/27/99. (b) The term "U-metal" is used to distinguish uranium in the mettallic form from uranium that will be present, as, for example, an oxide or hydride. iv ambient-temperature treatment options that were...

Mitigation of Hydrogen Gas Generation from the Reaction of Water with Uranium Metal in K Basins Sludge

“…Because H 2 is flammable, its release into the gas phase above K Basin sludge during sludge storage, processing, immobilization, shipment, and disposal is a concern to the safety of those operations in the current alternatives and design development activities of the K Basin Sludge Treatment Project (STP). Previous considerations of the disposal of the K Basin sludge to the Waste Isolation Pilot Plant (WIPP) determined that the sludge amount that could be loaded into drums for shipment as remote-handled transuranic waste was limited by the H 2 generation rate (Mellinger et al 2004). The evaluations showed that the H 2 generation rate is dominated by the H 2 arising from the uranium-water reaction with much lower contributions from radiolytic H 2 .…”

Interim Report on Uranium Metal Segregation Testing

“…A technology assessment (Mellinger et al 2004) concluded that to meet the WIPP hydrogen gas concentration criterion, both a uranium metal removal operation and some reduction of the reaction rate by a solidification matrix will be required. Accordingly, testing is required to establish the technical feasibility of segregation processes and to determine the extent to which the uranium metal can be removed.…”

“…), and a preconceptual process flow diagram ( Figure A.1). Based on discussions with vendor technical staff and mineral processing experts, it was concluded that gravity mineral concentration technology potentially could remove 85% or more of the uranium metal from the bulk of the K Basin sludge (Mellinger et al 2004). Removing 90% of uranium metal from design-basis KE floor sludge would likely satisfy a conservative interpretation (a) of the WIPP hydrogen generation limit.…”

Construction, calibration, and field test of a home-made, low-cost hydrophone system for cetacean acoustic research

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