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Secondary > Steam Generator Blowdown > Flashcards

Steam Generator Blowdown Flashcards

1
Q

What is the purpose of the SC system?

A

To compensate for the impurity concentration effect on the steam generators by continuous blowdown

Also maintains the SG in wet lay-up by providing the capability to mix, sample and add chemicals to the SGs

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2
Q

What are the 3 types of blowdown used?

A

Normal, abnormal and high rate

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3
Q

Where are the 3 blowdown connections on the SG and what does each line have?

A

Hot leg blowdown, cold leg blow down and down comer blow down

Each line has 2 auto containment isolation valves that will isolate blowdown system on AFAS, MSIS & SIAS

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4
Q

Which blowdown line is the primary connection used?

A

Down comer blowdown

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5
Q

When a blowdown is aligned to the BFT, where does the resultant vapor discharge to?

A

To the heater drain tank equalizing line or the condenser

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6
Q

What happens to the liquid in the flash tank?

A

processed for reuse by cooling in the blowdown heat exchanger, filtering, demineralizing and discharging to the condenser hotwell

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7
Q

What allows the plant to divert secondary water with unsatisfactory chemistry and where does it go?

A

Steam generator overboard piping

To the retention basin

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8
Q

What happens if radioactive concentration gets above a predetermined setpoint?

A

Isolation valve SCN-HV1283 will auto close

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9
Q

What provides cooling to the blowdown heat exchanger?

A

CD system

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10
Q

What is used to backflush the blowdown basket strainer?

A

DS

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11
Q

Which LPFW heater can the BFT liquid be directed to?

A

3

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12
Q

Where is the condensate cooling water for the BDHX returned to?

A

Discharge of the ED pump just prior to the suction of the main feedwater pumps

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13
Q

What is used to cool the blowdown demin sample coolers?

A

Normal chill water WC

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14
Q

If there is any activity present in the low TDS sump, where can I send it to?

A

LR TDS system

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15
Q

The SGBD demin High TDS sump is normally pumped to where?

A

CWNT

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16
Q

How are the blowdown flow control valves operated?

What position do they fail in?

A

air operated

Fail closed on loss of air or power

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17
Q

Where is the blowdown normally controlled from?

A

control room

18
Q

How is the BFT sized?

A

For processing continuous abnormal rate blowdown from 1 SG and normal rate for the other

19
Q

How is operation affected when Demin/reten LV (HG-3B/3C) is selected?

A

Demin outlet valve (HV-3B) is modulating to maintain BFT level and the blowdown flow to the condenser or HV-3C is lined up and the blowdown flow is going to the retention pond.

The demin bypass HV-3A is closed

20
Q

How is operation affected when “BYP DEMIN MODE” is selected?

A

HV-3A is modulating to maintain BFT level with the flowdown flow going to feedwater heaters 3A, B, and C. Vlave HV-3B is closed

21
Q

What is SCN-PV-4A and what does it do?

A

A pressure regulating valve in the vapor line from the BFT

Maintains flash tank pressure at nominal setting of 200psig but is adjustable by the operator

22
Q

When would SCN-PV-4B be opened?

A

When both heater drain tanks are out of service of it is desirable to discharge the vapor directly to the condenser, the isolation valves downstream of PV-4A are closed and 4B is opened

Also opens when valve 4A cannot maintain the flash tank pressure at its proper setting

23
Q

How are the 2 valves operated and what is their fail fail position? (SCN-PV-4A & -4B)

A

Air operated

Fail open on a loss of air or loss of power

23
Q

After the plant power is changed by greater than 5% why does the operating procedure direct an operator to close the BFT to the heater drain tank equalizing valves?

A

To reduce secondary chem hideout by having all blowdown that ends up in the BFT to go to the condenser

24
Q

What makes up the blowdown demin package?

A

2 mixed bed regen type units in series

a filter that removes suspended solids from the blowdown liquid before demineralization

25
Q

What could cause the demin outlet valve (SCN-HV-3B) to auto shut?

In this case how would we reestablish blowdown flow?

A

If that outlet valve is controlling BFT level and a high demin inlet temp is sensed

Take switch to “BYP DEMIN MODE”

26
Q

What happens if high sodium greater than 1 ppb is detected in one of the vessels?

A

The affected vessel is removed from service

27
Q

What happens if just one vessel is in service and a high sodium is received?

A

Vessel goes into 30 min rinse to see if the concentration will be reduced

28
Q

What would be considered high D/P for a vessel?

A

25 psi

29
Q

What flows thru the tube side of the BDHX?

A

Condensate

30
Q

What is the outlet temp of the BDHX controlled at?

A

less than 135F

31
Q

When is a situation where the abnormal rate of blowdown would be used?

A

To correct abnormal steam generator chemistry

32
Q

What is the SG blowdown systems role in SG wetlay up operations?

2) What would be different during wet layup cleanup operations?

A

Water from the SG is recirculated using the SG wet layup pumps.

This water is pumped from the SGs thru the blowdown lines and recirculated back to the SGs via the downcomer lines

The blowdown system provides a means of chemistry to add chemicals to the SGs during wet lay up operations

2) same as above except the water is processed thru the blowdown demins prior to returning to the SG downcomer lines

33
Q

What else can we use the wet layup pumps for?

A

To pump down SGs during drain and refill operations as required for maintenance

34
Q

What is the rated shutoff head for wet lay up pumps?

A

220 psi

35
Q

What is the optimal flow and maximum flow for these pumps?

A

Optimal flow @ 160gpm @ 180psi

Maximum flow @ 220gpm @ 100psi

36
Q

Where are the switches for the recirc pumps located and where do they get power from?

A

located in containment next to the pumps on the 80’

NH

37
Q

How is the system affected by the loss of IA?

A

Blowdown to flash tank control valves fail closed and blowdown to condenser control valves fail closed stopping blowdown.

Also, the flash tank condensate level control valve to FW heater fails closed, the BFT pressure control valve to heater drain tank fails open and the BFT control valve to condenser fails open

38
Q

How is the system affected by a loss of condensate flow to the blowdown heat exchanger?

A

Inlet water temp to the blowdown demins will rise to the point that the demin outlet valve will auto close

Blowdown is secured to prevent overfilling and over pressurizing the BFT

39
Q

How is the plant affected by loss of blowdown system?

A

While at power conductivity increases in the SGs leading to significant corrosion rates in the SGs

This requires chemistry to initiate CCIs or direct control room to shut down the system

Demand for SG feed will drop during loss of blowdown

40
Q

How much of the wet layup recirc water enters the tube bundle area of the SG thru the recirc line?

A

40%

Secondary (26 decks)

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