Experimental Investigation of In Situ Cleanable HEPA Filters

Abstract

DISCLAIMERThis report was prepared as an account of work sponsoredby an agency of the UnitedStates Government.Neither the United States Governmentnor any agency thereof,nor any of their employees, makes any warranty, express or impliecl or assumes any legal liability or respondility for the accuracy, completeness,or usefulnessof any information apparatus, product, or process disclosed,or representsthat its use would not infringeprivately owned rights.Referencehereinto any specificcommeraal product, process,or serviceby trade name, trademark manufacturer,or otherwisedoesnot necessarilyconstituteor implyits endorsement, recommendation,or favoring by the United States Governmentor any agency thereof. The views and opinionsof authorsexpressedhereindonot necessarilystate or reflectthose of the UnitedStatesGovernmentor any agencythereof. The SRS high level waste (HLW) tank ventilationsystems are equippedwith conventionaldisposableglass-fiberHEPA filter. Routineremoval, replacement, and disposalof these filtersare not only costly, but subjectssite personnel to radiationexposure and contributeto an ever-growing waste disposalproblem for the site.The Engineering Development Section designed and constructed a test rig, as shown in Drawing A (pictures in Appendix B) to simulate the conditions found in a HLW tank ventilation system. Two sintered metal filters were tested, one manufactured by Mott Filter Corporation and the other by the Pall Filter Corporation. Testing was conducted to determine the feasibility of washing HEPA filters in situ after becoming plugged with the simulated solutions found in the HLW tanks.The filters were tested using simulated HLW salt, simulated HLW sludge and South Carolina road dust to simulate atmospheric dust. The filters were operated until they became plugged (airflow decreases 20% or greater due to particulate matter buildup from the simulated solutions). The filters were then cleaned in situ by spraying off the soiled side of the filters with 10°/0nitric acid and/or 10°/0sodium hydroxide and/or water. After the wash cycle, the filters were returned to service.During the simulated HLW salt test, the Pall filter completely plugged after being saturated with water during the in situ wash, as shown in Figure 1, 2 and 3. Since the PalI filter did not recover from the in situ cleaning without oven drying, it was not suitable for our use and removed from fhrther testing. On the other hand, the Mott filter was insensitive to water and recovered to approximately the original airflow and differential pressure (dP) after the in situ cleaning, as shown in Figures 1,4 and 5. Distilled or nano-pure water was the only solution required to clean the Mott filter during the salt test.The Mott filter recovered after in situ cleaning after pluggage with dry salt. As shown in Figures 6 and 7, the airflow and dP across the filter recovered after each cleaning cycle. The Mott filter was also regenerable with in situ cleaning while testing with both simulated HL W sludge and South Carolina road dust. Figures 10...

Full Scale Regenerable Hepa Filter Design Using Sintered Metal Filter Elements

“…The results of those tests are reported in document WSRC-TR-98-00382 issued in October of 1998. 1 The findings suggested that a full-scale HEPA filter utilizing porous metal media was feasible.…”

Alternative HEPA Filter Full-Scale Single Element Testing

“…(10) From the analysis one could determine what analytes were collecting on the filter media from the simulant. These materials (and atmospheric dust), neglecting the radioactive constituents, are believed to be responsible for plugging the existing HEPA filters in the HLW tanks.…”

“…Proof of principle for an in situ cleanable HEPA filter was a success with the lab scale filters, which led to the full-scale single element work with the ceramic and sintered metal filters. (2) Through the Tanks Focus area, this technology was shared with other locations such Idaho National Engineering Laboratory (INEL), West Valley and Lawrence Livermore National Laboratory (LLNL). At INEEL, simulated Calcine transfer testing was conducted using small-scale ceramic filters with success.…”

Secondary Waste Considerations for Vitrification of Sodium-Bearing Waste at the Idaho Nuclear Technology and Engineering Center FY-2001 Status Report

“…Savannah River Site has been experimenting with washable ceramic HEPA filters. 4,5 Further studies on these filters would need to be checked for flow capacity, amount of rinse solution produced, and plugging problems with the acidic scrubber off-gas.…”