Design for safeguards of nuclear facilities - Online HePA filter replacement system
Date of Original Version
High Efficiency Particulate Arrestance (HEPA) filters serve an important role in the safety of nuclear facilities and can be an important tool in safeguards verification of nuclear activities. This paper describes a new design for HEPA filter housing in nuclear facilities to reduce replacement time, improve safety, reduce worker dosage, and facilitate safeguards procedures post replacement. A primary goal of this design was for the facility to remain online during filter exchanges. Other design goals were: 1) achieve International Atomic Energy Agency (IAEA) sampling practices; 2) meet the nuclear air and gas code specifications and relevant subsections ; and 3) adhere to the principles of ALARA (as low as reasonably achievable), for maintaining low radiation levels to maximize worker safety. Our new design focuses on improved safety while achieving an online filter exchange. Not only will an online filter exchange reduce facility downtime and save facilities money, it has the potential to offer increased worker safety, and provide easy filter access for IAEA officials who wish to conduct sampling and inspection for safeguards. We also conducted research on sealing techniques to support the online system design. We have established a project relationship with Radiation Protection Systems (RPS) Inc., a company based in Groton, Connecticut, USA that specializes in mobile HEPA filter and carbon pre-filter housings for nuclear applications. The technical information exchange and partnership with RPS may result in a product that can be installed in future nuclear power plants if the design is proven viable in concept and function. It may also be possible to retrofit existing HEPA installations in some cases. The design includes a double door bag-in, bag-out (BIBO) design and operational procedure to maintain worker safety. The system allows for zero escape of radioactive volatiles or particulates into the air external to the facility enclosure. A combination of neoprene gasket, silicone gel, and brush sealing techniques are employed in the new design while maintaining continuity of airflow during the switch. This innovative design improves safety as well as operational efficiency. The design team is cognizant of safeguards considerations and targeted the design towards facilitating access. In particular, our new design access to HEPA filter for sampling involves a much easier process. This in turn potentially improves the frequency and quality of sampling during IAEA inspections. Likewise, the lower level of effort (therefore cost) in switching filters will encourage changing filters more frequently. This will lower the risk of filter failures caused by clogged or possibly faulty filters. In fact, the IAEA reported that “Investigators from other national laboratories have suggested that aging effects could have contributed to over 80 percent of these failures.” The prototype design features a HEPA filter train (2 HEPA filters connected by a gel-seal interface) that slides seamlessly through the housing on rollers while the nuclear facility is online, the first (old) filter is dislodged into a sealed bagging unit, and the second (new) filter is clamped into place using a cam shaft clamping mechanism. The design shows promise for success in maintaining air flow and safety during the filter exchange, improving ease of use, automating the exchange process, providing continuity of knowledge, and simplifying radiation monitoring techniques.
Transactions of the American Nuclear Society
Bolt, Joshua J., Matthew J. Carlson, David L. Kehoe, Bahram Nassersharif, Christy Ruggiero, and Carolynn P. Scherer. "Design for safeguards of nuclear facilities - Online HePA filter replacement system." Transactions of the American Nuclear Society 119, (2018): 990-993. https://digitalcommons.uri.edu/mcise_facpubs/618