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Secondary > Auxiliary Feedwater (AF) > Flashcards

Auxiliary Feedwater (AF) Flashcards

1
Q

How does water get to SG after MSIS?

A

AFA turbine can be fed upstream of the MSIVs so on a MSIS we can still get steam to the turbine to then feed downstream of the downcomer FWIV into the SGs.

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2
Q

What happens on MSIS?

A

The following close to isolate steam from leaving containment:

- Downcomer FWIV’s (SGA-UV-172, 175, 
  SGB-UV-130,135)
- Economizer FWIVs (SGA-UV-174, 177, 
  SGB-UV-132, 137)
- MSIVs
- MSIV bypass isolations
- Upstream steam trap isolation valves
- BD ctmt iso and sampling ctmt isolation 
  valves
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3
Q

What actuation signals that affect AF?

A
  • AFA will actuate on AFAS ½
  • AFB actuates on AFAS ½
  • LOP (after sequenced back on)
  • SIAS and CSAS
  • AFN trips on SIAS
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4
Q

What are the Flex Connections on AF?

A

FLEX connections are north of CST for a pump that sucks on B AF suction piping and discharges downstream of check valves to feed either SG in the AFB room

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5
Q

What are the location of FLEX tools and how are they operated?

A

FLEX pump will be brought from our FLEX building and staged north of the CST where it will be hooked up following the procedure that is on the pump skid and attached to the connections closer to the CST

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6
Q

What are the flex inputs to AFW used for?

A

Fukushima was the reason for us having flex to remain in green risk when we have a piece of an equipment out for maintenance or something

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7
Q

What are the auto actions/interlocks with AFN?

A
  • AFN will only start if both of its suction
    valves HV-1 and HV-4 are at least 80%
    open
  • If they are not, it will not start or if it’s
    running, it will trip the pump. The pump
    will also trip on a SIAS
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8
Q

Where does FP tap into AFN?

A

Fire protection taps into AFN discharge piping and the fire pumps can pump the water into the SG

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9
Q

What are the rounds on the AF pumps A and B?

A
  • AFA has pump oil checks
  • AFB has pump and motor oil checks
  • They both have temperature tape on their discharge piping upstream the check valve to identify a failed check valve and we either have steam coming back and could steam bind the pump
  • After checking B pump room out, you have to ensure the door separating the pump rooms is closed
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10
Q

What happens when the temperature strip indicates steam binding?

A
  • If the temperature strip indicated steam binding, the pump must be vented by closing the locked open mini recirc back to the CST valve and open the discharge header vent valve until solid stream of water then close vent valve and reopen and lock the mini recirc valve
  • If temperature doesn’t decrease, close vent and tell system engineer to investigate
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11
Q

How are AF pumps cooled?

A

Self cooled from the 4th stage discharge to cool oil coolers and returns to pump suction

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12
Q

How does water flow through the AF pump?

A
  • They are 8 stage double volute pumps so the water enters one side and goes through four stages and then loops over to the other side and goes back through the last 4 stages then it discharges via discharge piping in the middle of the pump
  • This way there isn’t a need for thrust bearings because the flow in both ways equalize the thrust wear and force in one direction
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13
Q

What are the interlocks for AFN suction valves?

A

Must be >80% open before start or it wont start or it will trip the pump if running

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14
Q

Is the non seismic part of AF tech spec related (AFN)?

A

The non seismic part of AFN is everything after the two seismic suction valves (AFN-HV-1 and 4) from the CST

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15
Q

In regards to AF, which valves are the containment isolation valves?

A
  • AFA-V079 and AFB-V080 are discharge check valves inside CTMT
  • AFB-UV-0034, -0035, AFC-UV-0036 and AFA-UV-0037 are outboard CTMT isolation valves (relief valves on 0037 and 0036 are also classified as ctmt isolation valves)
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16
Q

What are the containment isolation valves for the steam lines in AF?

A

SGA-UV134, -134a, -138, -138A all are isolation valves coming from the SG to feed the AFA turbine

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17
Q

What are the auto start/stop features of the AF pumps?

A
  • AFA starts on AFAS 1/2 (SGWL: 25.8%)
  • AFB starts on AFAS ½, CSAS, SIAS and LOP after sequenced back on
  • AFN trips on SIAS
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18
Q

What happens when an AFAS is received and what initiates it?

A
  • Generated by PPS when applicable steam generator water level has lowered to 25.8% of the Wide Range detector
  • Both Essential AF pumps start, and the affected steam generator(s) regulating and isolation valves open
  • When level in the affect steam generator(s) reaches 40.8% wide range, the applicable regulating and isolation valve will close
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19
Q

What are the requirements of being the dedicated operator to close containment isolation valve?

A

Dedicated operator has 60 seconds to close isolation valves per the containment integrity design basis manual

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20
Q

What modes are containment isolation valves required?

A

Modes 1-4 per LCO 3.6.3

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21
Q

Describe how to reset AFW pump overspeed trip

A

There are two overspeed trips, electrical and mechanical

22
Q

What provides cooling to the AFW pump bearing?

A
  • Bearing lubrication is by slinger rings to throw oil onto the bearings
  • Cooling for bearing oil is accomplished via two integral oil coolers that utilize a slipstream form the pump first stage discharge
23
Q

Describe the operation of AFN-P01

A

Takes suction on the CST and feeds the SGs through the main feed downcomer control valves usually used during low power operations (up to 3% power since we can inject ammonia and hydrazine into the suction of the pump)

24
Q

What are the power supplies including control power for AF pumps?

A
  • AFA control power to governor: PKA-D21
  • AFA isolation and regulating valves: PKA or PKC (batteries so we can
    still steam the SG when LOP)
  • AFN power: PBA-S03
  • AFN control power: PKA-D21 OR from A train battery charger
  • AFB power: PBB-S04 – PHB for reg and isolation valves
25
Q

What is the flow capacity of the various AFW pumps?

A
  • AFA: 1010 gpm 1425#
  • AFB: 1010 gpm 1425#
  • AFN: 1010 gpm 1280#
26
Q

What is the normal discharge pressure for a AFW pump?

A

> 1330 psig (overcome SGs (1270 psig))

27
Q

What is the basis for the amount of AF that is reserved for use in the plant during an emergency situation?

A

Provides sufficient reserve of feedwater to permit the plant to operate in Mode 3 for 8 hours followed by an orderly plant cool down at a rate not to exceed 75F/hr, to the point where Shutdown Cooling may be placed in operation (RCS ~350F)

28
Q

What is the capacity of the CST and RMWT?

A

CST – 550,000 gallons

RMWT – 480,000 gallons

29
Q

How is HA affected by a high water level in either AF pump room?

A

Aux Building Normal AHU dampers isolate the Aux Building HVAC form the rooms

30
Q

How is ‘N’ AFP self-lubricating?

A

Uses dipper rings to throw oil onto the bearings

31
Q

What provides cooling water for the AFP lube oil coolers?

A

Pump’s first stage discharge

32
Q

Why does ‘N’ AFP have two class powered suction valves? Where are they located?

A
  • Provide class and seismic protection
    boundary for CST inventory, separating it
    from the non-seismic piping to ‘N’ AFP
    downstream of the isolation valves
  • Located in CST Pump House
33
Q

What is the interlock associated with ‘N’ AFP and its suction valves? Purpose?

A

If either of the valves is less than 80% open, the pump will not start and will trip if running
To provide protection from a low suction pressure condition, which could damage the pump

34
Q

Where is ‘N’ AFP located?

A

100’ Turbine Building, NW corner

35
Q

Where are all non-seismic Category 1 penetrations located on the CST?

A

Above the level of the Safety related storage volume (300,000 gallons, or ~28 ft)

36
Q

The construction and design of ‘B’ AFP are effectively identical to that of ‘N’ AFP with what exceptions?

A
  • ‘B’ AFP is designed to meet seismic category 1 requirements
  • ‘B’ AFP is equipped with a larger horsepower motor (125% larger)
  • ‘B’ AFP is equipped with an automatic start feature from the ESFAS load sequencer module of the BOP ESFAS that will start the pump under certain conditions
37
Q

What else starts when the ‘B’ AFP starts?

A

Essential air cooling unit automatically starts

38
Q

Where are ‘A’ and ‘B’ AFP located?

A

80’ of the MSSS

39
Q

In regards to the ‘A’ AFP, what is the purpose of the worm drive gearbox?

A

Coupled to an oil pump and the turbine’s governor actuator, and driven off of the turbine

40
Q

What is the minimum speed of the ‘A’ AFP to provide adequate lubrication and cooling?

A

1000 rpm

41
Q

How do we maintain the cleanliness of the ‘A’ AFP governor control system?

A

Renewable cartridge filter that has a built in dirt alarm that will automatically bypass the filter when it becomes clogged

42
Q

How does ‘A’ AFP respond to an AFAS?

A
  • SGA-UV-134A and 138A open first to bring the turbine up to speed in a slow and controlled manner
  • 30 seconds later SGA-UV-134 and 138 open to allow maximum steam flow to the turbine, and as the turbine approaches nominal speed, governor begins to throttle governor control valve to ~3600 rpm
43
Q

Why is there a large condensate pot installed in the Aux Building?

A
  • To allow for continuous draining of the moisture that can accumulate in the steam supply line
  • Without it, moisture could accumulate in the steam supply line which would greatly increase the chance of turbine overspeed during startup
44
Q

Where can I trip AFA-HV-54 electrically?

A
  • Board 6 in the Control Room
  • ‘A’ Remote Shutdown Panel
  • Local control panel
45
Q

What is the purpose of the AF Regulating and Isolation valves?

A

To provide means to regulate and isolate flow, respectively, to the steam generators from the Essential AF pumps

46
Q

What powers the regulating and isolation valves associated with ‘A’ AFP?

A

PKA and PKC

47
Q

What is pressure locking in regards to double disk gate valves?

A
  • When the valve is closed, inevitably a volume of water becomes trapped between the two disks
  • Pressure locking occurs when that trapped volume of water experiences thermal expansion due to heating, which causes an increase in pressure that is sufficient to “lock” the valve in the closed position such that the valve actuator may not be able to open it
48
Q

How do we prevent pressure locking?

A
  • Each ‘A’ train isolation valve’s bonnet areas is connected to a relief valve that relieves to the CST, normally via ‘A’ AFP mini-flow line
  • An equalizing valve is installed between the ‘B’ train isolation valve’s bonnet areas and the discharge side of these valves
49
Q

What happens if steam generator pressures differ by more than 185 psid?

A
  • Indicative of a main steam line break or feedwater line break affecting the steam generator with the lowest pressure
  • The D/P lockout will close the regulating and isolation valves for the affected steam generator, and prevent them from being reopened
50
Q

During startup, up to what power will we maintain S/G levels with AF?

A

2%

Secondary (15 decks)

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