ADS - 1.0 Flashcards
What is the purpose of ADS?
Depressurize the RPV during a SMALL BREAK LOCA when HPCI cannot maintain level.
Describe the operation of the ADS SRV solenoids.
- 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
- The 5 ADS SRVs have a high safety setpoint to preclude opening and save them for their Emergency Depressurization function (1130#)
Describe the ADS Logic.
- Two logic channels (B & D) are used to depressurize the RPV on LOCA conditions when HPCI is incapable of maintaining level.
- 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.
- Loss of 1E DC power will render its respective ADS logic channel and the pilot solenoid inop (prevents all inititiation).
- Loss of 1E AC inverter power (1BD481/1DD481) deenergizes trip units and prevents ADS actuation from the respective channel (prevents auto initiation).
- 105 second timer starts and seals in when -129 and high drywell seals in
When does ADS initiate?
- Hi Drywell Pressure (1.68psig) [Seals in]
OR
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:
a) One CS loop operating (Both D/ch pressure ≥ 145 psig)
b) One LPCI loop operating (Pump D/ch pressure ≥ 125 psig)
Explain the ECCS pump channels for each ADS sub-channel.
- Low pressure pumps are channelized for each ADS sub-channel permissive:
a. Channel B sub B = CSS B or RHR B or RHR D
b. Channel B sub F = CSS D or RHR B or RHR D
c. Channel D sub D = CSS A or RHR A or RHR C
d. Channel D sub H = CSS C or RHR A or RHR C
Explain the relationship btwn manual operation of ECCS pumps and ADS.
Pump permissives are not required for manual initiation, and subsequent pump stops do NOT stop ADS.
Purpose of the 300 sec TD.
The 300 second (5 minute) timer is for breaks outside of the drywell.
How many ADS pushbuttons are there?
Each Channel (B, F, D, H) has its own manual initiate pushbutton.
Explain the purpose of the keylock switches.
ADS can be inhibited prior to initiation by placing keylock switches in inhibit
1. Will NOT close already open ADS valves.
What actuates the SRV/ADS VALVE NOT CLOSED OHA?
SRV High tailpipe temp or Acoustic Monitor
List the power supplies for ADS.
- ADS Channel B logic and the A ADS SRV pilot solenoids are powered from 1BD417 dist. ( - 10D420 bus)
- ADS Channel D logic and the B ADS SRV pilot solenoids are powered from 1DD417 distribution pnl (10D440)
List the ADS SRV setpoints.
- A/B/C/D/E Lift Safety Setpoint 1130 PSIG
- G/L/J/R/P Lift Safety Setpoint 1120 PSIG
- M/F/K/H Lift Safety Setpoint 1108 PSIG
- Low-Low Set Actuations:
a) Lo-Lo Set H & P Arms 1047 PSIG
b) ‘P’ Open 1047 PSIG
c) ‘P’ Close 935 PSIG
d) ‘H’ Open 1017 PSIG
e) ‘H’ Close 905 PSIG - SRV Safety Reclosure ≈55-100 PSIG below opening setpoint
- ADS Valve Closure ≈50 PSID
Explain the power supply for H and P SRV logic.
- ‘P’ is D channel 125vDC logic powered and also ‘D’ pressure instrument [1/1 logic]
- ‘H’ is B channel 125vDC logic powered and also ‘B’ pressure instrument [1/1 logic]
When are the logics resets?
LOGIC RESET – resets 300sec timer if <1.68# and <-129”
Resets 105 sec timer if >1.68# and <129”
Closes ADS valves if actuated on logic
HI DW press logic reset – resets hi drywell seal in only – does not affect timers if 1.68 still in
ADS timer inhibit – stops ADS timer, closes valves if logic actuated
Logic reset – resets 105sec timer (initiates in 105s if >1.68#), resets 300sec timer (405s if -129).
What occurs when RSP takeover is initiated?
When RSP takeover has been performed, the ‘H’ lo-lo set logic no longer goes to bailey, therefore only ‘P’ logic remains. RPV will cycle on ‘P’ lo-lo between 1047 and 935#.
