Experimental Investigation of In Situ Cleanable or Regenerative Filters for High Level Radioactive Waste Tanks
The Westinghouse Savannah River Company, located at the Savannah River Site (SRS) in Aiken, South Carolina, is currently testing two types of filter media for application as in situ regenerable/cleanable filters on high-level radioactive liquid waste tanks. Each of the 1.3 million-gallon tanks is equipped with an exhaust ventilation system to provide tank ventilation and to maintain the tank contents at approximately 1-in. water gauge vacuum to prevent the release of radioactive material to the environment. These systems are equipped with conventional, disposable, glass-fiber, High Efficiency Particulate Air (HEPA) filters that require frequent removal, replacement, and disposal. The need for routine replacements is often caused by accelerated filter loading due to the moist operating environment, which structurally weakens the filter media. This is not only costly, but subjects site personnel to radiation exposure and possible contamination. The types of filter media tested, as part of a National Energy Technology Laboratory procurement, were sintered metal and monolith ceramic. The media were subjected to a hostile environment to simulate conditions that challenge the tank ventilation systems. The environment promoted rapid filter plugging to maximize the number of filter loading/cleaning cycles that would occur in a specified period of time. The filters were challenged using non-radioactive, simulated high level waste materials and atmospheric dust, as these materials are most responsible for filter pluggage in the field. The filters were cleaned/regenerated in situ using an aqueous solution of dilute (10% volume) nitric acid. The study found that both filter media were insensitive to high humidity or moisture conditions and were easily cleaned in situ. The filters regenerated to approximately clean filter status even after numerous plugging and cleaning cycles. The filters were leak tested using poly alpha olefin aerosol at the beginning, middle, and end of the test campaign. Both the sintered metal and ceramic filters passed the challenge test with the efficiency of a conventional HEPA filter each time. The sintered metal and ceramic filters not only can be cleaned in situ but also hold great potential as a long life alternative to conventional HEPA filters. The Defense Nuclear Facility Safety Board Technical Report, entitled HEPA Filters Used in the Department of Energy's Hazardous Facilities, found that conventional glass fiber HEPA filters are structurally weak and easily damaged by water or fire. The structurally stronger sintered metal and ceramic filter media would reduce the potential of a catastrophic HEPA filter failure due to filter media breakthrough in the process ventilation system. An in situ regenerable system may also be applicable to recovery of nuclear materials, such as plutonium, collected on glove box exhaust HEPA filters. This innovative approach of the in situ regenerable filtration system may be a significant improvement upon the shortfalls of conventional disposable HEPA filters.
- Research Organization:
- Savannah River Site (SRS), Aiken, SC (United States)
- Sponsoring Organization:
- US Department of Energy (US)
- DOE Contract Number:
- AC09-96SR18500
- OSTI ID:
- 761161
- Report Number(s):
- WSRC-MS-2000-00599; TRN: US0406849
- Resource Relation:
- Conference: 26th Nuclear Air Cleaning Conference, Richland, WA (US), 10/10/2000--10/12/2000; Other Information: PBD: 23 Aug 2000; PBD: 23 Aug 2000
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ALKENES
AQUEOUS SOLUTIONS
CERAMICS
CLEANING
CONTAMINATION
LIQUID WASTES
NITRIC ACID
PLUTONIUM
RADIOACTIVE MATERIALS
RADIOACTIVE WASTES
TANKS
VENTILATION SYSTEMS
WASTES
RADIOACTIVE WASTE FACILITIES
STORAGE FACILITIES
AIR FILTERS
REGENERATION
PERFORMANCE
AIR POLLUTION CONTROL