What is the purpose of the ADS?
Depressurize the RPV during a SMALL BREAK LOCA when HPCI cannot maintain level.
The ADS SRVs are?
A,B,C,D, and E SRVs
What is the ADS SRVs setpoint and why?
1130 psig. The 5 ADS SRVs have a high safety setpoint to preclude opening and save them for their Emergency Depressurization function
ADS uses what logic and why?
- ADS uses B and D logic.
- HPCI uses A and C logic. The ADS is electrically separated from the HPCI System, including sensors and logic circuitry, thereby ensuring that no single failure affecting the HPCI System will impact the ADS, and vice versa
How do the ADS SRV solenoids work and what is their power supply?
- Each of the 5 ADS SRVs contain 2 pilot solenoids,
- EITHER of which will open the SRV.
- One pilot solenoid is ‘B’ DC powered, the other is ‘D’ DC Powered
- (1BD417 / 1DD417)
Two logic channels (B & D) are used to depressurize the RPV on LOCA conditions when HPCI is incapable of maintaining level. How do the subchannels work?
- Each logic channel contains 2 sub-channels, both sub-channels within EITHER channel must actuate; however, EITHER logic channel will energize the respective ADS SRV pilot solenoids.
- B --> B & F
- D --> D & H
How does loss of power affect ADS function?
- Loss of 1E DC power (1BD417 / 1DD417) will render its respective ADS logic channel and the pilot solenoid inop (prevents all initiation).
- Loss of 1E AC inverter power (1BD481/1DD481) deenergizes trip units and prevents ADS actuation from the respective channel (prevents auto initiation).
When does ADS initiate?
- Hi Drywell Pressure (1.68psig) [Seals in]
- 300 Second TD w/ RPV level below -129”
- Rx Low Level – Level 1 (-129”) [levels do NOT seal in]
- Rx Low Level – Level 3 (+12.5”) [B&D only, Confirmatory Signal]
- 105 second timer expired [B & D only] (Starts when above 3 in)
- Any of the following:
- __One CS loop operating (2 pumps both D/C pressure >=145 psig)
- __One LPCI loop operating (Pump D/ch pressure >=125 psig)
- __Low pressure pumps are channelized for each ADS sub-channel permissive:
- ____Channel B sub B = CSS B or RHR B or RHR D
- ____Channel B sub F = CSS D or RHR B or RHR D
- ____Channel D sub D = CSS A or RHR A or RHR C
- ____Channel D sub H = CSS C or RHR A or RHR C
What pump permissives are needed for manual initiation?
Will subsequent pumps stops stop ADS
What is the purpose of the 300 second timer?
The 300 second (5 minute) timer is for breaks outside of the drywell.
How many manual initiate pushbuttons are there?
4, Each Channel (B, F, D, H) has its own manual initiate pushbutton.
How can ADS be inhibited? What is a limitation of this inhibit?
- ADS can be inhibited prior to initiation by placing ADS ACTUATION TIME keylock switches in inhibit.
- This will NOT close already open ADS valves.
How do you reset an ADS timer?
When LOGIC B/F (D/H) INIT RESET PB is depressed it resets ALL timers to 0.
What causes the SRV/ADS VALVE NOT CLOSED alarm?
SRV High tailpipe temp or acoustic monitor
Power Supplies for ADS solenoids:
- ADS Channel B logic and the A ADS SRV pilot solenoids are powered from 1BD417
- ADS Channel D logic and the B ADS SRV pilot solenoids are powered from 1DD417
A,B,C,D,E Lift Safety Setpoint:
G,L,J,R,P Lift Safety Setpoint:
M,F,K,H Lift Safety Setpoint:
Low-Low Set setpoint and actuations:
- Lo-Lo Set Arms - 1047 psig
- ‘H’ and ‘P’ both open
- Setpoints are set down to:
- __‘P’ Open - 1047 psig
- __‘H’ Open - 1017 psig
- __‘P’ Close - 935 psig
- __‘H’ Close - 905 psig
What is the SRV Safety reclosure?
55-100 PSIG below opening setpoint
When will SRVs begin to close even with an OPEN signal?
The SRV will begin to spring actuate closed WHEN system inlet pressure < 50 psig.