Sluicing operations were performed to retrieve high-heat sludge from single-shell tank (SST) 241-C-106 (C-106) and transfw it to double-shell tank 241-AY-102 (AY-102) using the Waste Retrieval Sluicing System. This has eliminated the high-heat safety issue for C-106 and demonstrates a technology for retrieval of SST waste. The behaviors of AY-102 and C-106 were monitored during the waste transfer operations, providing a clear picture of general trends in each tank. Specific issues addressed were evaluation of the data for evidence of flammable gas accumulation in AY-102 and thermal performance of AY-102 under the increasing heat load. Reports summarizing the data were produced on a regular basis from September 1998 through October 1999 and posted to a web page on the internal Hanford intranet. This greatly facilitated communication between the contractors, Pacif3c Northwest National Laboratory and the Office of River Protection during the operations. Sluicing operations were canied out in a series of three campaigns, each of which removed approximately one-third of the C-106 sludge. The first campaign was initiated on November 10, 1998, with the fti transfer of sludge from C-106 to AY-102, and was concluded on March 28, 1999. Unexpected delays were encountered due to unacceptably large releases of volatile organic compounds (VOCS) through the C-006 ventilation stack when operations fmt disturbed the deep layers of sludge in C-106. (Release mtes were measured in excess of 450 ppm when the permitted limit was 50 ppm.) Changes @procedures and equipment mitigated this problem, and in the following campaigns, the VOC release rate never exceeded the permitted limit. The initial estimate based on sluicing data indicated that 75,405 gallons of sludge (approximately 40% of the 192,000 gal originally in C-106) were transferred to AY-102 in Campaign #1. Campaign #2 was initiated on April 23, 1999 after meeting the requirements of hydrogen release rate and level change to determine that gas was not being retained h"the waste that had been transferred to AY-102. The amount transferred in Campaign #2, which was terminated on June 3, 1999, was initially estimated as 51,482 gal of sludge. This represents about 27°/0 of the initial sludge volume in C-106, resulting in an estimated 66% transferred to AY-102 in the frst two campaigns. Campaign #3 was initiated on July 21, 1999 and continued in 12 separate batches until October 6, 1999. The amount transferred in this campaign was initially estimated as 59,000 gal of sludge, or about 31YOof the original amount in C-106. A total transfer amount of approximately 186,000 gal, or 97Y0,was estimated from measurements during sluicing. Estimates obtained from thermal analyses of C-106 and AY-102 and other independent calculation methods post-sluicing indicate that at least 182,000 gallons, or 95°/0 and up to 188,000 gallons, or 98?40,of the original C-106 sludge was transferred to AY-102. The video inspection pefiormed in C-106 in July 2000 clearly shows that about 45,000 gal of waste remai...

ph: (865) 576-8401 fax: (865) 576-5728 email: reports@adonis.osti.gov Available to the public from the National Technical Information Service, U.S. Department of Commerce, 5285 Port Royal Rd., Springfield, VA 22161 ph: (800) 553-6847 fax: (703) 605-6900 email: orders@ntis.fedworld.gov online ordering: http://www.ntis.gov/ordering.htmThis document was printed on recycled paper. SummaryThe Hanford Spent Nuclear Fuel Project focuses its efforts on determining how to safely move the degraded N-Reactor spent fuel from water-stored basins to a dry storage facility. As part of this effort, the project initiated experimental studies to address issues relating to the chemical reactivity of the degraded/corroded metallic uranium material. The studies generated a limited set of data on chemical reaction rates of the N-Reactor spent fuel in dry-air, moist-air, and moist-inert atmospheres for comparison with published data on unirradiated/irradiated metallic uranium. Based on the laboratory data, the project chose to use a conservative enhancement factor in analyzing the oxidation behavior of the spent metallic fuel. However, there is a need for the project to increase the fuel throughput for the drying-treatment process by implementing certain design optimization steps. The study discussed in this paper re-evaluated the previous laboratory data in conjunction with the cold vacuum drying (CVD) process experience and determined whether the built-in level of conservatism could accommodate the potential changes in the process without compromising public and worker safety.Evaluations based on laboratory data on samples taken from the corroded N-Reactor spent fuel showed no reactivity enhancement for the degraded metallic uranium in moist atmospheres. The established oxidation reaction-rate constant was used to accurately determine the reactive surface areas of corroded N-Reactor fuel elements. The surface areas calculated for six different N-Reactor elements that were stored in the K-West Basin and shipped to Pacific Northwest National Laboratory for drying studies ranges from as low as 0.0018 m 2 for a broken element to 8.1 m 2 for a highly corroded spent nuclear fuel (SNF) element 5744U based on the measured reaction-rate constant for the K-Basin SNF (k SNF ). On the other hand, if the literature-averaged rate constant (k Lit ) is used, the calculated areas are between 0.0002 and 1.1 m 2 .

Nearly 2100 metric tons of metallic uranium spent nuclear fuel (SNF) are stored in two water-filled pools-the K-Basins-in the 100-K Area at Hanford. The Spent Nuclear Fuel Project is resolving the safety and environmental issues associated with continued wet storage of the deteriorating SNF in these basins. The project's fuel-handling process involves preparing, loading, and transporting fuel for drying and subsequent storage in canisters, pending suitable repository disposal. Scrap generated from October to July, 2001, while washing the SNF to prepare it for cold vacuum drying, differed significantly from that envisioned during project design. This raised the issue that the geometric reactive surface area of particles of uranium in the scrap could be higher than allowed for the baseline process. Therefore, Fluor Hanford convened a technical review panel to evaluate the new information about the physical characteristics of scrap generated during processing. The technical review began after K-Basin staff tested the process by retrieving, weighing, and photographing the scrap that they collected during the washing process.

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