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
What is the S/G PORV Set point raised to when have a SG Tube Rupture?
- 1040#
How do the S/G PORV’s fail?
- Closed
How do the MSL, Bypass Header, and Turbine Steam Lead Drains fail on Turbine Trip?
- Open
Which ONE of the following describes the function of the LOCKOUT position associated with each Steam Generator Stop Valve (SGSV) Dump Valve control switch?
A. Prevents the operator from opening the SGSV Dump Valves after the receipt of a Hi-Hi Containment Pressure Signal.
B. Allows the operator to close the SGSV Dump Valves after the receipt of a Hi-Hi Containment Pressure Signal.
C. Prevents a Hi-Hi Containment Pressure Signal from closing the associated SGSV and allows testing of the circuitry.
D. Allows the operator to open a SGSV hydraulically after the receipt of a Hi-Hi Containment Pressure Signal.
B. Allows the operator to close the SGSV Dump Valves after the receipt of a Hi-Hi Containment Pressure Signal.
What is the safety related purpose of the Main Steam system?
- Supply steam to the TDAFP
How is the SGSV held open/closed?
- Detents
Where are the U1 Main Steam orifices located?
- On the bypass header before entering the bypass equalizing header
Where are the U2 Main Steam orifices located?
- Main Steam Header right after the SGSVs
