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Primary System Mechanical > HVAC Week > Flashcards

HVAC Week Flashcards

0
Q

What areas in containment are cooled by containment HVAC?

A

CEDMs, Pzr cubicle, reactor cavity, tendon gallery, and MSSS

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1
Q

What spaces are affected by containment HVAC?

A

Containment and MSSS

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2
Q

What is NC used for in containment HVAC?

A

Cool the CEDM ACUs

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3
Q

Where does the chilled water for the normal ACUs come from?

A

Normal chill water (WC)

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4
Q

What containment HVAC components are affected on a SIAS?

A

Normal ACUs trip, CEDM normal ACUs trip, reactor cavity fans trip

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5
Q

What happens to the containment building HVAC system on a CIAS?

A

Isolation valves for the RU-1 monitor close

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6
Q

Which ACUs are sequenced back on following a LOP?

A

CEDM and containment normal ACUs

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7
Q

What does the containment hydrogen control system do?

A

Maintains hydrogen levels inside containment below combustibility limits

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8
Q

What is the purpose of the containment purge system (CP)?

A

Assist HC in reducing levels of airborne radioactivity prior to personnel access.

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9
Q

How many normal ACUs are there for containment HVAC?

A

4 to recirc and cool air inside containment

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10
Q

What is the purpose of the pre-access normal AFUs?

A

They are 2 filter units that are operated in support of personnel entry into containment.

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11
Q

What is the flow path of air through the CEDM normal ACUs?

A

Air from containment is drawn across the RX vessel head and around the CEDMs then into ducting leading to the ACUs. Air then gets cooled and discharged to the upper containment volume.

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12
Q

What do the four reactor cavity cooling fans prevent?

A

Deterioration of the cement in the reactor cavity.

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13
Q

Why are both MSSS ventilation exhaust fans normally operating?

A

Since each fan only takes a suction on one side of the MSSS both fans should normally be running

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14
Q

Where is RU-1 located and where does it take a suction sample from?

A

It’s located in the aux building and it draws a sample from the 120’ level of containment

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15
Q

What are the power supplies for the normal containment HVAC ACU fans?

A

PGA and PGB

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16
Q

How are the HC normal ACUs’ fan suction dampers operated?

A

Motor operated and they open when the ACU is started

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17
Q

What type of interlock is associated with the HC normal ACU duct heaters?

A

A low flow interlock to keep the heaters from turning on without enough air flow to remove heat generated.

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18
Q

What will cause another fan to start in the HC normal ACU line?

A

If an operating fan trips and the other fan is in the “Normal After Stop” position, another fan will start 60 seconds after one has tripped.

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19
Q

What components make up the containment pre-access filtration AFUs?

A

High efficiency filter bank, HEPA filter, charcoal filter, and then a second HEPA filter.

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20
Q

How many CEDM ACUs are operated at one time?

A

Normally two 100% capacity redundant ACU’s are operated whenever the CEA mechanisms are energized.

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21
Q

Why is there a 120 second time delay between 2 CEDM ACU fans tripping and the second set starting?

A

To allow the non operating fans to come to a stop if the back draft or suction dampers were leaking. Leakage would cause reverse rotation of the fans.

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22
Q

How many RX cavity cooling fans are normally in service?

A

Two. (There are 4 total and they are powered by NH

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23
Q

Where can damper position be verified for the RX cavity cooling fans?

A

At the MCC supplying power to the damper

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24
Q

What auto function is associated with the RX cavity cooling fans?

A

There is a 60 second delay in the auto start of a fan after low d/p is sensed on the running fan.

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25
Q

What are the power supplies to the Pzr space exhaust fans?

A

SIAS load shed panels NHN-M71 and M72

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26
Q

Where are the MSSS vent supply fans controlled from?

A

Locally with a 3 position switch (stop- auto- start)

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27
Q

Are there any automatic features associated with the MSSS exhaust fans?

A

No.

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28
Q

Where is power for RU-1 isolation valves supplied from?

A

PK

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29
Q

What does the containment purge (CP) system do?

A

Purges containment atmosphere to the plant vent stack while introducing filtered air from outside for personnel comfort when the plant is shutdown and for limited periods during power ops for personnel access.

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30
Q

What subsystems make up CP?

A

Refueling purge and power access purge

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31
Q

What else is the power access purge system used for?

A

Used to control pressure in containment by periodically venting to the plant vent stack

32
Q

What components make up the refueling purge unit AHUs?

A

Filter, heating and cooling coils, and two supply fans that discharge through dampers and isolation valves

33
Q

How many radiation detectors are in the refueling purge system discharge line?

A

Two. They will alarm on high radiation.

Two others are located near the exhaust lines that will isolate the purge system if they sense high radiation.

34
Q

What components make up the power access purge exhaust AFU?

A

Moderate filter, HEPA filter, charcoal filter, HEPA filters, and a fan.

Also has 2 monitors in the line and 2 monitors near the exhaust.

35
Q

What flows through the cooling coils in the refueling purge AHU and the power access purge AHU?

A

Normal chilled water

36
Q

How do the air operated valves and dampers in the CP system fail on a loss of IA?

A

They fail closed and this causes the shutdown of the associated AHUs and AFUs and their supply and exhaust fans.

37
Q

When is the refueling purge supply AHU operated?

A

Only in mode 5 or 6

38
Q

How many supply and exhaust fans are normally running when the refueling purge AHU/AFU is running?

A

2 of each with the exhaust being higher capacity for negative pressure

39
Q

Why is a heater installed upstream of the charcoal filter in the power access purge normal exhaust AFU?

A

To prevent the charcoal from being damaged by moisture.

40
Q

What will cause a purge to stop in the CP system?

A

CPIAS or CIAS will initiate on a high rad alarm from RU-37 or 38. Either of these will stop the purge

41
Q

What happens when the refueling purge supply AHU is started?

A

Discharge dampers open and cooling water supply valve auto opens. It will open and close to vary temperature automatically. If the heaters are needed, they will be manually placed in service and will cycle as needed.

42
Q

What systems are operated together as necessary to clean the containment atmosphere?

A

HP(pre access normal AFUs and the power access purge system

43
Q

What is the difference between the venting mode in CP and the power access purge mode?

A

In venting mode, air pressure that has built up during normal ops is vented out through a bypass with a flow orifice.

In the power access mode, containment atmosphere is purged to the plant vent stack through an exhaust AFU while introducing filtered and treated air from outside using the AHU.

44
Q

How does a loss of 120vac affect CP?

A

Power is lost to RU-37 & 38 and this actuates a CPIAS. This will cause the system to shutdown and isolate from containment.

45
Q

How does a loss of 125vDC affect CP?

A

The refueling purge outlet dampers fail closed and prevent AHU operation.

The power access purge inlet damper fails closed and prevents operation of the AHU.

46
Q

How does a loss of IA affect CP?

A

Air operated containment purge valves fail closed. If a purge is in progress and IA fails, the valves will fail closed.

All that should be done is to verify valves went closed.

Any air operated dampers will fail closed on a loss of IA and trip any running fans.

47
Q

What does the containment hydrogen control system (HP) do?

A

Monitor H2 concentrations in containment following an accident

Maintain H2 below the lower combustible level limit of 4% in the air.

48
Q

What subsystems make up the HP system?

A

Hydrogen monitoring system
Recombined system
Purge subsystem

49
Q

How many locations does the H2 monitoring subsystem take a suction on in containment?

A

Two.

50
Q

Where does the H2 sample suction line come from?

A

The suction line to the H2 recombiner which comes from containment and goes back into containment.

51
Q

When is the H2 placed in service?

A

Following a LOCA, excess steam demand, or functional recovery procedure implementation, the control room un-isolates the analyzer and turns it on.

52
Q

Why is heat trace supplied for the HP analyzer subsystem?

A

To prevent excess condensate from developing in the lines

53
Q

What two gases are required for operation of the hydrogen analyzers?

A

N2 for calibration of the unit an O2 is required for the unit to work.

54
Q

How are the H2 analyzers placed in service?

A

By un isolating them and taking the switch on the panel in the control room to analyze.

55
Q

What are the power supplies to the H2 analyzers?

A

PH and PK

56
Q

How is hydrogen mixing accomplished after a LOCA?

A

Mixing is provided by containment spray and the internal design of containment structure. The design permits convective mixing and prevents local entrapment of hydrogen as long as the accident conditions require.

57
Q

How does the hydrogen recombiner work?

A

Containment atmosphere is drawn into the recombiner with a blower. The air/hydrogen is heated to 1150F. The free hydrogen recombines with O2 to form water vapor at that temp in the reaction chamber. The water vapor passes through a gas cooler where it’s cooled and returned to containment.

58
Q

What signal will isolate the hydrogen recombiner?

A

CIAS

59
Q

When would the hydrogen purge subsystem be used?

A

If the recombiners both failed.

60
Q

How many hydrogen purge units are there on site?

A

One that is shared between all units.

61
Q

What are the major components of the hydrogen purge unit?

A

Moisture separator, heater, 2 HEPA filters, and carbon adsorber

62
Q

What happens to the hydrogen purge subsystem on a loss of IA?

A

The unit uses service air to drive air through the h2 purge unit. The unit would not operate.

63
Q

What is the purpose of aux building HVAC system?

A

A) provide ventilation to the aux building during normal ops and maintain temps in the required limits.
B) control release of airborne radioactivity from the aux bldg. During normal plant ops
C) maintain temps in the ESF equipment rooms during any emergency situation
D) control release of radioactivity from the area located below the 100’ elevation of the aux bldg after a LOCA. This feature utilizes the fuel bldg and aux bldg essential AFUs in the fuel bldg.

64
Q

What components make up HA (aux bldg HVAC)?

A

1) 2 normal supply and 2 normal exhaust AHUs.
2) a multi-zone AHU for the access control area
3) 2 local recirculating normal ACUs for the CEDM control cabinet room and MG set rooms
4) a normal ACU for each charging pump room
5) 5 normal fume hoods for the labs
6) a normal elevator fan
7) ESF equipment room essential ACUs
8) dampers, duct work, and mixing boxes

65
Q

How is smoke removed from the aux building in case of a fire?

A

Portable smoke ejectors

66
Q

How do the mixing boxes in the access control system ventilation system work?

A

Dual duct discharge from the AHU supplies one hot duct and one cold duct. The ducts enter the mixing boxes which uses pneumatic dampers to control air volume from the hot duct. The cold duct air flow is not modulated.

67
Q

Where do the HA normal exhaust AFU normally discharge to?

A

The plant vent

68
Q

When should the fire protection system be connected to the deluge system on the carbon adsorbers in the HA normal AFUs ?

A

When excessive temp levels are indicated in the charcoal adsorbers. The charcoal will ignite at 625F.

69
Q

Which ACUs are a part of the essential aux building HVAC equipment?

A 
HPSI pump room
LPSI pump room
CS pump room
EW pump room
AF pump rooms (in the MSSS)
ESF electrical pen rooms
70
Q

When will the ACUs in the electrical pen rooms start and stop?

A

Start on a SIAS or LOP

Manually stopped after condition clears

71
Q

What starts the AF pump air handling unit?

A

If either of the two steam supply valves open, ACU starts
Auto stop 5 minutes after steam valves close.

Can be started manually, but must be stopped manually if started manually

72
Q

What has to be done if AF pump room high temperature condition is caused by a steam leak?

A

The AF pump rooms must be isolated from each other within 1 hour to prevent degradation of the other AF pump.

73
Q

What can abnormal building ventilation line ups cause?

A

Failure of fire dampers and loss of negative pressure.

74
Q

Why do we not want to shut down either A or B train of aux bldg ventilation during boric acid concentrator discharges?

A

Because water formation in the ventilation and associated radiation monitors can occur. Notify the CRS and the rad waste area operator prior to stopping either train of aux building ventilation

75
Q

What would need to be done if there was a change in either aux building ventilation or rad waste building ventilation during a waste gas release and why?

A

Temporary suspension of the waste gas release.
The change would affect the plant ventilation exhaust process flow rate parameter used in calculating RU-12 set points for the release. The concentration at the release point would be increased due to less dilution flow.
Recalculation would be needed and if the calculation didn’t change, then we could continue on the same permit.

76
Q

What happens to HA on a loss of 125vdc?

A

Isolation dampers that isolate below the 100’ level in the aux building all fail closed

77
Q

What happens to ventilation in the access control area on a loss of IA?

A

AHU continues to run, but taking suction on the HA supply header. This could result in contamination of the 140’ spaces supplied by this AHU. Hot air to mixing boxes is stopped causing the discharge to be in complete cooling mode.

Primary System Mechanical (7 decks)

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