Frequency Categories

Due to the nature of the particular type of cycle gas compression at the facility, a significant release of hydrocarbon, though highly unlikely, could not be placed in a frequency category of 1 "not realistically expected to occur." For these reasons, the qualitative assessment team ranked the scenario as a "2" frequency. It was felt that a QRA would only confirm this evaluation. 

In the high-frequency category of discharges, several investigations of coal have been reported. All of these investigations use microwave (2.45 GHz) excitation. Use of rf (1—200 MHz) excitation has not been reported yet, perhaps due to difficulty in sustaining the discharge at gas pressures produced on volatilization of the coal. 

III Unlikely 10 >F>10" Accidents that are not anticipated to occur during the lifetime of the facility. Natural phenomena of this frequency category include Uniform Buiiding Codelevel earthquake, 100-year flood, maximum wind gust, etc. 

V Extremely Unlikely 10 >F All other accidents. Accidents too unlikely to be considered in the design basis. Some accidenfe in feis frequency category may be evaluated as beyond design basis accidents. 

The entire accident scenario is described by a frequency category, F, corresponding to a yearly frequency measure,/, given by equation 2. 

Frequency Category Dose target to public Plant criteria... 

TABLE XIV-3. PBMR FREQUENCY CATEGORIES AND EVENT TYPES [XIV-9]... 

Event type Postulated initiating EVENT Frequency CATEGORY Notes... 

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