• Provide primary system overpressure protection.
• Provide automatic and manual RPV depressurization or pressure control.
• Flow path for alternate shutdown cooling.

• 1109 psig
• 30 psid blowdown
• Two sizes (750,000 lbm/hr and 887,000 lbm/hr)

Backup to HPCI.

Enables low pressure ECCS to inject should HPCI fail to operate.

107 sec Timer expiration

Timer starts when:

-47 inches reactor level AND AC interlock satisfied.

NOTE: if low low level clears before timer expiration, then ADS does not initiate. However, if ADS initiates, then the only two things that will interrupt the signal are:

• Both ADS Inhibit switches OR
• No AC interlock

• If water level goes above -47 inches (with AC interlock prior to timer timing out),
• AC interlock not satisfied,
• Both INHIBIT switches

• Full scram signal present
• Hand-switch in auto
• Reactor pressure below setpoint (1052, 1062, 1072 psig)

H: 1052 psig

G: 1062 psig

E: 1072 psig

Blowdown is approximately 80 psi

10 seconds after valve shuts

(Minimizes possibility of SRV re-opening with elevated water leg inside discharge piping.)

• Loss of AC Interlock (no low pressure ECCS pumps running)
• Level restored above -47 inches prior to 107 second timer timing out
• Both Inhibit switches.

MSIVs trip on:

1. Less than 840 psig with mode switch in RUN
2. Rx Low-Low Level (-47 inches)
3. High Areal Temp (195-200 degrees F)
4. 140% steam flow.

PCT trips on:

1. Rx Low Level (+9 inches) or
2. High Drywell Pressure (1.84 psig)

Non-liquid PCT trips on:

1. Fuel pool high rad (50 mR/hr) or
2. Rx Building Plenum High rad (26 mR/hr)

NOTE: these trips are NOT 1-out-of-2 taken twice.

RWCU trips on:

1. Low-low leve (-47 inches)
2. High drywell Pressure 1.84 psig
3. High Flow (462 gpm for 10 seconds)
4. Low Flow (-200 gpm for 10 seconds)
5. RWCU room high temperature (170 degrees F)

RCIC Isolates on:

1. High steam flow (44,434 lbm/hr for 5 seconds)
2. RCIC steam line area high temp (187.5 degrees F)
3. RCIC steam line low pressure (60 psig)

HPCI isolates on:

1. High steam flow (300,000 lbm/hr for 4 seconds)
2. Area temperature (187.5 degrees F)
3. HPCI steam supply line low pressure (100 psig)

1. Initiation signal must be clear
2. All MSIV handswitches are placed in CLOSE
3. Reset pushbutton

1. Initiation signal must be clear
2. All handswitches in the group are placed in CLOSE with exception of MOVs
3. Reset pushbuttons

1. Initiating signals clear
2. Reset Pushbuttons

AC Source: Y10

DC Source: D33

AC Source: B-44P

DC Source: D100

Pneumatic System Supply for SRVs

Normal: Instrument Nitrogen

Safety-Related Backup:

• Alternate Nitrogen Train 'A': SRVs A, B, E
• Alternate Nitrogen Train 'B': SRV's C, H, F
• Accumulators: D and G

Nonsafety-Related Backup: Instrument Air