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Main Steam System > MS > Flashcards

MS Flashcards

0
Q

What systems receive steam from the main steam system?

A 
MSR
FW pump turbines
Steam seal system (MT and FWP turbines)
AFA-P01
Aux steam
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1
Q

What is the purpose of the main steam system?

A

Delivers steam from the SG to the HP turbine from warm-up to valves wide open
Also provides method of heat dissipation

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2
Q

What do the SG downcomer isolation valves do?

A

Allows remote isolation of the downcomer FW lines downstream of the downcomer CVs

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3
Q

What do the SG economizer isolation valves do?

A

Allows the remote isolation of the economizer FW lines downstream of the economizer CVs

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4
Q

What does the SG do?

A

Transfers heat from the RCS to the secondary system moisture separators and steam dryers.

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5
Q

What do the main steam safety valves do?

A

5 MSSVs on all four MS supply lines upstream of the MSIVs

Prevents over pressurization protection from being removed from SGs and Main steam supply lines.

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6
Q

What do the main steam ADVs do

A

Means to remove heat from the RCS when the main condenser and/or SBCS is not available.

One ADV on each main steam supply line upstream of MSIVs

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7
Q

What do the MSIVs do?

A

One valve just downstream of the safety and ADVs.

Quick closes on MSIS using the accumulator

Slow positioning using air operated hydraulic pump.

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8
Q

What do MSIV bypass valves do?

A

Pneumatic operated gate-type valves

Bypasses one of the two MSIVs

Allows warmup of the downstream piping

Also equalizes pressure for easier valve operation

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9
Q

What do the SBCVs do?

A

8 valves (6 to condenser, 2 to atmos)

Open automatically or manually based on need for main steam pressure control

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10
Q

How does the RCS interact with the main steam system?

A

Depends on the SGs for heat removal

Loss of this ability = Rx trip
Extended loss= core damage

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11
Q

How doe the FW system interact with the main steam system?

A

Interface downstream of 7a & 7b FW heaters

Loss = inability to cool RCS leading to plant trip (due to low SG water levels or high pressure)

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12
Q

How does the SBCS interact with the MS system?

A

Modulates SBCVs to maintain high steam pressure

If high pressure goes uncorrected by use of ADVs, decrease in turbine load or Rx power = Rx trip and/or high primary system temperature or pressure

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13
Q

How does IA interact with the MS system?

A 
Supplies control or operating air or both to :
Downcomer FWIVs
Economizer/downcomer CVs 
ADVs
SBCS valves

Some hydraulic operated valves use IA for operating pumps

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14
Q

How does The service gas system (GA) interact with the MS system?

A

Provides N2 to accumulators for ADV, downcomer FWIVS & backup for downcomer feed CVs.

Also for blanketing SG in shutdown

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15
Q

How does the aux feed system interact with MS?

A

SG supplies steam to AFA-P01

AF supplies water to either SG either manually or automatically

AFN supplies during shutdown conditions

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16
Q

What is the steam source for the second stage heating in the MSRs?

A

Main steam

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17
Q

What provides steam to the aux steam system?

A

Main steam

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18
Q

What is the purpose of the steam generator downcomer valve upstream block valves?

A

Allows remote isolation of the downcomer CVs

Motor operated, normally open, gate valves

Just upstream of the SG downcomer CVs.

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19
Q

What is the purpose o the SG downcomer control valves? And how are they operated?

A

100% of flow passes through during low power operation.

At 15% and increasing valves close and economizer valves throttle open.

At 50% downcomer CVs re-open to a set position and supplies 10% of all feed flow from 50-100% power.

Provides sub cooling for recirc water, also increase recirc ratio

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20
Q

What is the purpose do the SG downcomer control valve bypass valves?

A

Motor operated, normally closed

Taps into the downcomer FW lines just upstream of the SG downcomer valve upstream isolation valve and just downstream of the downcomer control valves.

In mode 3 they are used to control generator water level.

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21
Q

What is the purpose and operation of FW downcomer isolation valves?

A

Gives the ability to isolate the downcomer feed line.

Pneumatically operated, normally open

2 valves. On each line (A-upstream & B-downstream)

CR operated

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22
Q

How does an operator override the downcomer isolation valves?

A

Place the valve in the closed position and then to open.

Valves fail open on loss of DC control power and fail closed on loss of IA or N2 backup.

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23
Q

If we were to lose IA how long will the downcomer isolation valves be able to operate?

A

Up to 8 hours using installed backup nitrogen accumulator.

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24
Q

Where are the downcomer isolation valves located?

A

On the MSSS 100’ level.

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25
Q

What is the purpose of the SG economizer feed control valves?

A

Control the flow of FW into the SGs in conjunction with the downcomer control valves & digital FW control system.

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26
Q

What is the purpose of the SG economizer line stop valves?

A

Allow remote isolation of the economizer FW line

Motor operated non class MCC power.

Located just upstream of economizer CVs.

27
Q

What is the purpose of the SG economizer CVs?

A

Control feed to the economizer section of the SG.

Pneumatically operated and normally controlled by the digital FW control system.

May be controlled manually by operator in the CR.

Located in the turbine building 120’ mezzanine.

28
Q

What is the purpose of the FW economizer isolation valves?

A

Allows the remote isolation of the economizer FW line on the outside of containment.

29
Q

How do the FW economizer isolation valves respond to a loss of powe/air?

A

FC on loss of power

On loss of air valves fail as is. (Remain capable of fast closing)

30
Q

Where are the FW economizer isolation valves located?

A

MSSS building 120’ level.

31
Q

How are the economizer isolation valves controlled?

A

By hand switches in the CR or by the ESFAS system on MSIS.

32
Q

How many inlet and outlet nozzles does a SG contain?

A

One inlet

2 outlet

33
Q

What does the primary chamber do for the SG?

A

Directs reactor coolant flow through the steam generator

34
Q

What is the design purpose of the tube sheet and u-tubes in the SG system?

A

They form the boundary between the SG primary and secondary sides.

35
Q

What is the purpose of the secondary side shell in the SG system?

A

It forms the pressure boundary between the steam generator secondary side and containment atmosphere.

36
Q

What feature is included in the outlet nozzle of each main steam SG outlet line?

A

An integral flow orifice which limits steam flow in the event of a steam line break.

37
Q

What is the design purpose of the downcomer FW ring in the SG system?

A

Distributes FW entering the SG from the downcomer FW nozzle.

Enters top of the downcomer region and combines with moisture separated from the steam-water mixture… Drains to do encoder annulus.

38
Q

What is the purpose of the economizer in the SG system?

A

Increases SG efficiency by preheating incoming FW before it enter the evaporator section.

39
Q

What is the purpose of the wrapper plate in the SG system?

A

It divides the SG downcomer and evaporator sections.

40
Q

How do the moisture separators work?

A

They feature a cyclone design with spinner blades that are fixed, forcing the steam-water mixture entering the moisture separators into a circular motion.

41
Q

What is the purpose of the steam dryers in the SG system?

A

Provide for additional moisture removal before the steam leaves the SG.

Mounted on the dryer support plate above the moisture separators.

42
Q

What is the purpose of the MS safety valves?

A

They prevent the removal of overpressure protection from SGs and MSSLs

No isolation valves installed upstream of the safety valves.

43
Q

What is the relieving capacity of the MSSVs.

A

Capacity is divided equally between the main steam lines and is sufficient to pass greater than 100% steam flow.

Valves are spring operated and relieve sequentially. (Reduces chances of valve sticking open)

44
Q

How do ADVs react to a loss of IA (N2 backup included) or power?

A

Loss of power FC

Loss of air FC

45
Q

Are ADVs still operable in the event of a loss of IA and N2 accumulator?

A

Yes their is a back up nitrogen accumulator.

46
Q

What is the purpose of the Aux feed A feed pump steam supply valves?

A

Provides AFA feed pump turbines with steam when called upon by an AFAS or by hand switch actuation.

47
Q

How are the AF pump steam supply valves operated?

A

They are electrically operated gate valves.

Each SG supplies one set of valves.

Steam is supplied from a point upstream of MSIVs

48
Q

What happens when a steam supply valve (AFA) receives a signal to open?

A

Bypass first opens for 30 seconds which provides steam to spin the AFA feed pump.

Once governor oil pressure has sufficiently increased bypass valve closes and main steam supply valves open.

49
Q

Can the AFA feed pump turbine supply valves be closed automatically once opened?

A

No they must be shutdown manually…

When the hand switch is taken to close there is no 30 sec delay

Each supply valve has override capabilities.

50
Q

What are the methods for controlling the main steam supply valves?

A

CR board 6

Or from the. Remote shutdown panel by a two position spring return to normal switch.

51
Q

What is the purpose of the main steam isolation valves?

A

Designed for rapid positioning and will close automatically within seconds of receiving a MSIS

Valve positioning system allows for fast or slow closing.

52
Q

Where are the MSIVs installed in the main steam line?

A

They are downstream of the safety and ADVs.

53
Q

How do the MSIVs react on receipt of a MSIS?

A

A self contained hydraulic actuator mounted atop the valve yoke is provided along with two independent, redundant hydraulic supply systems. An MSIS from either train will actuate one hydraulic actuator per valve and will close all four MSIVs

54
Q

What will happen to the MSIVs on loss of offsite power or IA in relation to the hydraulic fluid control valves?

A

Two back up air reservoirs are provided to supply air for positioning the hydraulic fluid control valves.

55
Q

What happens to the MSIVs upon loss of IA or power?

A

Loss of power results in use of battery backup. When that is depleted FC

Loss of air=no change in position with capability of fast close still available.

56
Q

How many MSIV bypass valves are there?

A

2, one for each SG.

Located on MSSS 140’

57
Q

What will happen to MSIVs on MSIS, loss of power, loss of air?

A

Close MSIS
Close lop
Close loss of air

58
Q

How are the SBCVs operated?

A

Pneumatically operated using IA as the control and operating pressure source.

Normally operated from the control room by, SBCS or operator action.

Local manual control also available.

59
Q

What is the purpose of the downcomer, hot and cold leg blowdown isolation valves?

A

Provides the CR operator the ability to select the source for SG blowdown or to totally isolate the blowdown system if necessary.

60
Q

How are the downcomer, hot and cold leg blowdown isolation valves operated?

A

Motor operated valves located in containment.
No auto functions
Operated from CR with local manual operation available.

61
Q

What is the purpose of the combined blowdown line containment isolation valves?

A

Isolates the SG blowdown piping when desired or upon receipt of MSIS, AFAS or SIAS.

62
Q

Describe the normal operation of the combined blowdown line containment isolation valves?

A

Pneumatically operated gate valves

Normally operated from CR but can be operated manually.

2 valves (1 in ctmt, 1 outside ctmt)

63
Q

How do the combined blowdown line containment isolation valves respond to a loss of power or air?

A

The valves will fail closed.

64
Q

What is the purpose of the wet layup recirc pumps?

A

Provides a motive force to recirculate water in the SGs during shutdown conditions.

Also used for inventory transfer from the SGs.

65
Q

Describe the wet layup recirc pumps and how they are operated.

A

Single stage centrifugal pump per SG.

Operated locally at a control panel on the 80’ level of ctmt.

66
Q

Where can the SGs be recirculated from using the wet layup recirc pumps?

A

Hot leg, cold leg, downcomer blowdown lines..

Main Steam System (4 decks)

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