Setpoints alarm/action

The action functional component represent all the possible predetermined response actions which should occur upon reaching apredetermined alarm/action setpoint. Response actions could include activation of audible and/or visual alarms, annunciation of specific alarm conditions and locations, hardcopy of past and present gas concentrations or environmental conditions, notification of local and remote emergency response personnel, activation of emergency safety control systemsl l through relays such as gas supply source and equipment shutoffs, HVAC system shutdown with 100% exhaust, or one-pass cleanroom air flow operations. The predetermined response actions should follow established emergency response procedures and policies of your organization and all applicable environmental, health, and safety regulations to protect both personnel and the environment and minimize the extent and effect of any hazardous situations. 

Flammable gas detection systems are typically used to initiate an alarm at a concentration level below the lower flammable limit (LFL). Two gas alarm levels (low and high) are often utilized to allow early warning prior to taking automatic actions. Detection systems may also be used to stop electrical power and initiate process shutdown. The low alarm setpoint should be —20% LFL and the high alarm level set point should be between 40%-60% LFL. Where these devices are used to initiate process shutdown or activate fire protection systems, it is common practice to use some form of voting, typically 2 out of 2, such that the frequency of spurious shutdowns or system activation is minimized. 

The Zone 1 exhaust fan inlet volume control damper is manually set to maintain the total SCB exhaust flow rate in order to achieve the necessary residence time for exhaust gas in the charcoal filters. This ensures that radioactive iodine is removed from the Zone 1 exhaust gas before the exhaust gas is released to the environment. An alarm is provided to alert the operations staff if the flow rate exceeds the established setpoint. Should this occur, HCF operations personnel will investigate the reason(s) for the abnormal condition and take appropriate corrective action, which may include re-adjustment of the volume control damper. Since such an occurrence is not an initiator for a radioactive material release event, operator action is an appropriate response. In addition, certain activities in the SCBs may be curtailed until the condition is corrected. 

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