Passive filters charcoal filter

The Zone 1 and Zone 2A ventilation exhaust ducting and HEPA and charcoal filters are passive components. Their safety-related function is performed continuously while the HCF ventilation system is in operation. When the ventilation system is not operating, no isotope processing operations are being conducted, and any residual radioactive materials are in nonvolatile states and are confined within the SCBs and Zone 2A canyon. Thus, the functional requirements applicable to the filters are ... 

A TSR requirement to verify that Zone 1 and Zone 2A ventilation exhaust HEPA and charcoal filters are in-service vwll be implemented to assure that exhaust gases are being filtered when the HCF ventilation system is in operation. A TSR requirement to verify the ventilation system fan sequencing interlock is operable vvnil be implemented to ensure that proper building airflow patterns are maintained in the event of exhaust fan failures. The ventilation system exhaust ducting provides only an inherent passive safety function (i.e., confinement) and no specific TSR controls are required to ensure continued performance of this function. 

The effectiveness of active filter systems is known to be high, based on system tests, research results and simulations. The effectiveness of filters in passive systems as a means of limiting the potential for iodine releases is not known. Backfitting a filter system to an existing containment may be more expensive and less effective than some combination of other mitigation techniques discussed below. A drawback for all charcoal filter systems is the high cost associated with periodic testing of the effectiveness of charcoal. 

This potential design improvement consists of providing the middle and lower atmulus of the secondary concrete containment with a passive annulus filter system, for filtration of elevated releases. The passive filter system would be operated by drawing a partial vacuum on the middle annulus through charcoal and high efficiency particulate in air filters. The partial vacuum is... 

The instruments include an ionization chamber, the charcoal-trap technique, a flow-type ionization chamber (pulse-counting technique), a two-filter method, an electrostatic collection method and a passive integrating radon monitor. All instruments except for the passive radon monitor have been calibrated independently. Measurements were performed... 

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