Investigation into optimal conditions for cross-flow filtration of high-level nuclear waste
- Westinghouse Savannah River Co., Aiken, SC (United States)
The Savannah River Site has 23 Type 3 high-level radioactive waste tanks, each with a storage capacity of 1.3 million gallons. These tanks contain nearly 9 million gallons of precipitated salt. To immobilize the waste, the salt is dissolved through water addition, followed by precipitation of the radionuclides through the addition of sodium tetraphenylborate. This precipitate is then concentrated and washed to remove sodium through cross-flow filtration. This waste pretreatment process started radioactive operation in late 1995. During the normal plant operation, the cross-flow filtration system (consisting of two 216-square-foot filter elements) maintains a constant filtrate production rate. This objective is achieved by allowing the operating pressure to increase to maintain a constant filtrate production rate. A maximum pressure differential limit of 40 psig has been imposed on this system. When this maximum is approached, a high-energy backpulse of filtrate removes foulant from the surface of the filter, thereby restoring the filter flux. This laboratory work examined two key aspects of the anticipated facility operating conditions: the efficacy of using pressure differential to control filtrate production rates and the risk posed to filter performance associated with pore plugging of the filter immediately following the backpulse. Tests used simulated tetraphenylborate precipitate and a bench-scale cross-flow filtration unit consisting of two parallel filter units each 4 feet in length. Tests used slurries containing between 1 and 10 wt% tetraphenylborate to cover the anticipated range of operation. Data collected included both initial flux-decline measurements and steady-state filtrate production measurements. Analysis of these data indicates, for the more dilute slurries, pressure was an effective tool in controlling filtrate flux. However, as the slurry became more concentrated, the ability to manipulate filtrate flux by pressure greatly diminished. Analysis of the initial filtrate decline data using first-principle models indicates that the primary mechanism for decreasing filter flux involved development of a surface cake. Given the operating constraints of the facility, these results provide guidance for future filtration operation.
- Sponsoring Organization:
- USDOE, Washington, DC (United States)
- DOE Contract Number:
- AC09-96SR18500
- OSTI ID:
- 354482
- Report Number(s):
- CONF-9710103-; ISSN 0149-6395; TRN: IM9930%%223
- Journal Information:
- Separation Science and Technology, Vol. 34, Issue 6-7; Conference: 10. symposium on separation science and technology for energy applications, Gatlinburg, TN (United States), 20-24 Oct 1997; Other Information: PBD: Apr-May 1999
- Country of Publication:
- United States
- Language:
- English
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