Main and Reheat Steam Flashcards
What is the function of the Main Steam system?
- Supply steam to the TDAFW Pump
- Control the plant cooldown rate during a station blackout using the SG PORVs
- Allow rapid cooldown following a SGTR.
- Provide isolation capability following a HELB.
What is all of the Main Steam piping designed for?
- 1085# and 600°F
What the pressure set points for the SG PORVs, and MSSVs? ***
2 Safeties @ 1065 psig
2 Safeties @ 1075 psig
1 Safety @ 1085 psig
1 SG PORV @ 1025 psig
What percent steam flow are each safety rated for? ***
- 5.5% steam flow ea and 110% of design pressure
Why do we have PORVs?
- Prevents lifting safeties
use to cooldown when steam dumps are unavailable
What percent steam flow are each PORV rated for?
- 2.5% steam flow ea
What will cause a SI?
- SG < 500# on 2/4 SGs (1/1) (Manually blocked when P-12 is in) - Steam Line ΔP > 100# 1 SG lower than 2 others - 1 # in Ctmnt (2/3) - Pzr # Low 1775# (2/3)
What causes Steam Line Isolation (SLI)? ***
- 2.8# in Lwr Ctmnt
- SG Pressure Low
(500# 1/1 on 2 SGs) - High Steam Flow with Low-Low Tavg (541°F)
(1.42E6 (1.6E6) pph @ 0%, variable with power 1/2 on 2/4 SGs) - Manual
Where are the MS orifices located for each unit and how much do they restrict flow?
- Restricts SG flow to 40% of maximum
- U1 orifice is in Bypass Header.
- U2 orifice in MS line before bypass header (outlet of SGSV)
How will the SGSV dump valves fail on loss of ctrl power?
- Fails close which will not close the SGSV
How will the SGSV dump valves fail on loss of ctrl air?
- Fail open which will close the SGSV
Are the rad monitors downstream of the PORVs operable if the PORVs are isolated? ***
- No, they are INOP
2 monitors, and 4 detectors
What is the purpose of the SGSVs?
- Ensures only 1 SG will blowdown in a steam rupture, even when 1 SGSV fails.
- Minimize positive reactivity from RCS cooldown
- Limit Containment pressure for steam rupture inside Containment.
WIll the SGSVs close on a SLI?
- Yes, in 8 sec
How are the SGSVs interlocked to prevent opening them with a SLI signal?
- Hydraulics are interlocked to prevent opening with a standing SLI signal
How do you clear the SGSV interlock after and SLI signal has cleared to allow closing of the SGSV dump valves?
- Take the ctrl switch to lockout
What are the MS bypass header loads?
- MFPs
- MSR High Pressure Steam
- Steam Dumps
- Aux Steam
- Low Flow FW Preheating
- Turbine Steam Seals (U2 Only)
What are the Aux Steam header loads?
- Turbine sealing steam (U1)
- SJAE
- MFPs (startup)
- Plant heating
- Aux Building Vent Heating
- Boric Acid Batch Tank
- Chemical cleaning station
- Hotwell de-aerating (Unit 2 only)
- CO2 vaporizers
Where are the TDAFP Turbine steam shutoff valves located?
- on the 2 and 3 SGs after the MS venturis and before the Safties/PORVs
How will the PORVs fail on loss of ctrl power?
- Closed
How will the PORVs fail on loss of ctrl air/N2?
- Closed
How are the PORVs operated if ctrl power and ctrl air/N2 is lost?
- Manually by a handwheel on the valve
How do the SGSVs open and close?
- Hydraulic for normal opening and closing
- Steam to close in emergency
What does 3.7.4D SG PORVs (Mode 4 when SGs relied upon for heat removal) state?
- If 1 or more required SG PORVs Inoperable in Mode 4 when SG are relied upon for heat removal
IMMEDIATELY: - Initiate action to restore Inoperable SG PORV(s) to Operable status
