Main and Reheat Steam

Question 1

What are the safety related functions of the Main Steam system?

Answer 1

• 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.

Question 2

What the pressure set points for the SG PORVs and MSSVs?

Answer 2

2 Safeties @ 1065 psig
2 Safeties @ 1075 psig
1 Safety @ 1085 psig

1 SG PORV @ 1025 psig

Question 3

What percent steam flow are each safety rated for?

Answer 3

5.5% steam flow ea

Question 4

Why do we have PORVs?

Answer 4

• Prevents lifting safeties
• Used to cooldown when steam dumps are unavailable

Question 5

What percent steam flow are each PORV rated for?

Answer 5

2.5% steam flow ea

Question 6

In regards to the Main Steam System, what will cause a SI?

Answer 6

• SG less than 500 psi on 2 SGs (1/1)
• Steam Line DP greater than 100 psi, 1 SG lower than 2 others

Question 7

What causes Steam Line Isolation (SLI)?

Answer 7

• 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 at 0%, variable with power 1/2 on 2/4 SGs)
• Manual

Question 8

How will the SGSV dump valves fail on loss of ctrl power?

Answer 8

Closed, causing the SGSV to remain open

Question 9

How will the SGSV dump valves fail on loss of ctrl air?

Answer 9

Open, which will close the SGSV

Question 10

Are the rad monitors downstream of the PORVs operable if the PORVs are isolated?

Answer 10

NO

Also INOP if controller is taken to manual and closed

Question 11

What is the purpose of the SGSVs?

Answer 11

• 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.

Question 12

WIll the SGSVs close on a SLI?

Answer 12

Yes, in 8 sec

Question 13

How are the SGSVs interlocked to prevent opening them with a SLI signal?

Answer 13

Hydraulics are interlocked to prevent opening with a standing SLI signal

Question 14

How do you clear the SGSV interlock to allow closing of the SGSV dump valves?

Answer 14

Take the ctrl switch to lockout

Question 15

What are the MS bypass header loads?

Answer 15

• MFPs
• MSR High Pressure Steam
• Steam Dumps
• Aux Steam
• Low Flow FW Preheating
• Turbine Steam Seals (U2 Only)

Question 16

What are the Aux Steam header loads?

Answer 16

• 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

Question 17

Where are the TDAFP Turbine steam shutoff valves located?

Answer 17

2 and 3 SGs after the MS venturis and before the Safties/PORVs

Question 18

How are the PORVs operated if ctrl power and ctrl air/N2 is lost?

Answer 18

By a handwheel on the valve

Question 19

How do the SGSVs open and close?

Answer 19

• Hydraulic for normal opening and closing
• Steam to close in emergency

Question 20

What does 3.7.4D SG PORVs (Mode 4 when SGs relied upon for heat removal) state?

Answer 20

IMMEDIATELY Initiate action to restore Inoperable SG PORV(s) to Operable status

Question 21

What is the S/G PORV Set point raised to when have a SG Tube Rupture?

Answer 21

1040 psi

Question 22

How do the S/G PORV’s fail?

Answer 22

Closed

Question 23

How do the MSL, Bypass Header, and Turbine Steam Lead Drains fail on Turbine Trip?

Answer 23

Open

Question 24

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.

Answer 24

B. Allows the operator to close the SGSV Dump Valves after the receipt of a Hi-Hi Containment Pressure Signal.

Question 25

How is the SGSV held open/closed?

Answer 25

Detents

Question 26

Where are the U1 Main Steam orifices located?

Answer 26

On the bypass header before entering the bypass equalizing header

Question 27

Where are the U2 Main Steam orifices located?

Answer 27

Main Steam Header right after the SGSVs

Question 28

How many rad monitors and detectors for the PORVs?

Answer 28

2 monitors, and 4 detectors

Question 29

What does the operability of the Main Steam Safety Valves ensure?

Answer 29

secondary steam pressure will be limited to 110% of desired pressure during most severe anticipated operational transient

Question 30

When are the PORV Rad Monitors considered INOPERABLE per TRM 8.3.8?

Answer 30

• If PORV Manual Isoaltion Valves is closed
• If PORV controller is in manual

Question 31

When is Reactor Nitrogen System needed to maintain SG PORV Operability per TS 3.7.4?

Answer 31

When CAC or CD EDG is unavailable

Question 32

When is a SG PORV considered OPERABLE?

Answer 32

When capable of fully opening from the control room. (If manually isolated in field, PORV is INOP)

Question 33

What are the main steam pressures for both units at ~50% power?

Answer 33

Unit 1 ~885 psig
Unit 2 ~900 psig

Unit 2 SG pressures higher than Unit 1