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B21 Main Steam > General > Flashcards

General Flashcards

1
Q

What is the purpose of the Main Steam System?

A

The Main Steam System directs steam to the Main Turbine, provide a relief path for the RPV(SRVs), bypass steam directly to the Main Condenser, and provides for RPV isolation in the event of a steam line break.

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2
Q

What is the basic Main Steam flow path from the RPV to the Main Turbine?

A

RPV–>RCIC connection MSL A–>SRV–>Flow Restrictor–>Inboard MSIV–>Guard Pipe–>Outboard MSIV–>MSSV–>Equalizing Header–>Bypass Valves–>TSV/TCV–>Main Turbine.

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3
Q

Where does RCIC tap into the Main Steam System?

A

RCIC taps into Main Steam Line A upstream of the SRV.

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4
Q

How many Safety Relief Valves are in the Main Steam System?

A

There are 19 total SRVs.

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5
Q

What are the safety setpoints of the Safety Relief Valves?

A

1165 - 8 SRVs
1180 - 6 SRVs
1190 - 5 SRVs

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6
Q

How many Safety Relief Valves are Low-Low-Set valves?

A

6 total

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7
Q

What are the setpoints of the Low-Low-Set Safety Relief Valves, and how does the logic change those setpoints?

A

Normal setpoints:
B21-F051D: Open - 1103 psig Close - 1003 psig
B21-F051C: Open - 1113 psig Close - 1013 psig
B21-F051G & 3 other SRVs: Open - 1113 psig Close - 1013 psig.

Low-Low-Set setpoints:
B21-F051D: Open - 1033 psig Close - 926 psig
B21-F051C: Open - 1073 psig Close - 936 psig
B21-F051G & 3 other SRVs: Open - 1113 psig Close - 946 psig.

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8
Q

How many vacuum breakers are on the Safety Relief Valve tailpipe, where do they draw air from to break vacuum, and where do the tailpipes discharge?

A

There are 2 vacuum breakers on each SRV tailpipe.

The Vacuum Breakers draw air from the Drywell. The SRV tailpipes discharge into the Containment Suppression Pool.

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9
Q

What is the concern if a Safety Relief Valve Tailpipe Vacuum Breaker were to stick open?

A

If a SRV was to lift with a stuck open Vacuum Breaker the Drywell would be directly pressurized.

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10
Q

What are the two modes of operation for a Safety Relief Valve?

A

1) Safety

2) Relief Mode

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11
Q

How does the Relief function of the Safety Relief Valves work?

A

1) The SRVs will open at predetermined relief setpoints and seat at approximately 100 psig lower than the opening value.
2) Low-Low-Set: Six SRVs will open/close at modified setpoints after the first SRV opens.

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12
Q

How are the Safety Relief Valves affected when their control switches are placed in OFF?

A

When the control switch for the SRVs is placed in OFF the Relief Mode is bypassed.

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13
Q

How many solenoid valves are required to energize to open a Safety Relief Valve?

A

Each SRV has two solenoid valves, but only ONE is required, which can energize to provide air to actuate an SRV.

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14
Q

What are the power supplies to Safety Relief Valve Solenoids?

A

Division 1 - ED-1-A

Division 2 - ED-1-B

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15
Q

If one SRV key-lock switch is placed in OFF will the Relief Mode be disabled?

A

No, the other division is still available for the Relief Mode function.

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16
Q

Is the Automatic Depressurization System function bypassed with the key-lock switched is OFF?

A

NO, the ADS function is available regardless of the Control Room key-lock position.

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17
Q

What is the air supply to the Safety Relief Valves?

A

10 SRVs are supplied by Instrument Air.

9(8 ADS & 1 LLS) SRVs are supplied by Safety Related Instrument Air.

18
Q

What is the backup source of air if the normal supply is lost?

A

The SRVs have accumulators that store air in case the normal source is lost.

Non-ADS SRVs have one accumulator good for one cycle.
ADS SRVs have two accumulators good for two cycles.

19
Q

What is the RED light above the key-lock switches an indication of?

A

The red light above the key-lock switches on panel 601 illuminate on a pressure of 30 psig in the SRV Tailpipe.

20
Q

What do the Red and Green lights above the key-lock switches on the back panel indicate?

A

The Red and Green lights above the switches on the back panel are solenoid status lights.

21
Q

What is the purpose for Low-Low-Set?

A

Low-Low-Set reduces the number of SRVs that cycle thereby reducing the cyclic load on the Containment.

22
Q

When does the Low-Low-Set logic activate?

A

Low-Low-Set is armed when the first SRV setpoint is reached at 1103 psig.

23
Q

What are the two purposes of the Flow Restrictors?

A

1) Limit the blowdown to 150% in the event of a pipe break.

2) Upstream and Downstream taps provide input to Leak Detection and Digital Feedwater.

24
Q

What system provides air to operate the Main Steam Isolation Valves?

A

Instrument Air

25
Q

What type of valve is the Main Steam Isolation Valve and how does it operate?

A

The MSIV is a 26 inch angle globe valve. The MSIV uses IA pressure to overcome spring pressure to open, and bleeds air off to allow the springs(and air sometimes) to close.

26
Q

How many solenoid valves are energized when the MSIVs are OPEN, and how many must de-energize to close an MSIV?

A

Both solenoids are normally energized, and both must de-energize to cause an MSIV to close.

27
Q

What is the difference between closing an MSIV with the Control Switch/Automatically, and using the TEST pushbutton?

A

Closing the MSIVs with the Control Switch or Automatically is a “fast close” meaning air is bled off faster and air is applied on top of the MSIV to assist in closing.

Using the TEST Pushbutton bleeds air off slower and air is not applied to assist the MSIV in closing making it a “slow close”.

28
Q

Where does the power for the MSIV solenoids come from?

A

RPS A - A solenoid valves

RPS B - B solenoid valves

29
Q

What are acceptable closing times for the MSIVs?

A

2.5 - 5 seconds, with an average being 3 seconds or greater for the faster number.

30
Q

What is the basis for the MSIV closing time requirements?

A

Too fast would be a too large of a pressure/power spike.

Too slow would allow too much contaminated steam to reach the environment.

31
Q

What is the significance of Instrument Air pressure dropping to 90 psig in regards to the MSIVs?

A

The MSIVs must be declared inoperable due to possibly not meeting their closing times.

32
Q

What is the significance of Instrument Air pressure dropping to 48 psig in regards to the MSIVs?

A

When Instrument Air pressure drops to 48 psig the MSIVs will start to drift closed.

33
Q

What is the interrelation with Safety Related Instrument Air and the Outboard MSIVs?

A

Safety Related Instrument Air provides for Post-LOCA leak tightness for the Outboard MSIVs.

34
Q

What will cause an MSIV to automatically close?

A

1) Level 1(16.5 inches RPV Level)
2) Low Main Steam Line Pressure 807 psig
3) High Turbine Building Temperature 146 F
4) High Main Steam Tunnel Temperature 156 F
5) Low Condenser Vacuum 21.5” HgA
6) High Main Steam Line Flow 254 psid
7) Manual

35
Q

What type of logic does the MSIVs use for automatic closure?

A

1 out of 2 taken twice

36
Q

What will cause the Main Steam Line Drain Valves(F016 & F019) to automatically close?

A

The same signals that cause an MSIV isolation.

37
Q

What type of logic do the Main Steam Line Drain Valves use for automatic closure?

A

Inboard/Outboard logic.

38
Q

How many Main Steam Bypass Valves are there, and what is their capacity?

A

There are 7 Bypass Valves, and they can pass 4% steam flow each for a total of 28%.

39
Q

What are the loads off the Main Steam Line Equalizing Header?

A

1) MSR 2nd Stage Heaters
2) Reactor Feed Pump Turbines
3) Offgas Preheaters
4) Steam Seal Evaporators
5) Steam Jet Air Ejectors

40
Q

How many pressure signals cause an SRV solenoid to energize?

A

2 independent pressure signals are required to energize an SRV solenoid.

B21 Main Steam (2 decks)

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