Steam Generator Blowdown

Question 1

What is the purpose of the SC system?

Answer 1

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

Question 2

What are the 3 types of blowdown used?

Answer 2

Normal, abnormal and high rate

Question 3

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

Answer 3

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

Question 4

Which blowdown line is the primary connection used?

Answer 4

Down comer blowdown

Question 5

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

Answer 5

To the heater drain tank equalizing line or the condenser

Question 6

What happens to the liquid in the flash tank?

Answer 6

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

Question 7

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

Answer 7

Steam generator overboard piping

To the retention basin

Question 8

What happens if radioactive concentration gets above a predetermined setpoint?

Answer 8

Isolation valve SCN-HV1283 will auto close

Question 9

What provides cooling to the blowdown heat exchanger?

Answer 9

CD system

Question 10

What is used to backflush the blowdown basket strainer?

Answer 10

DS

Question 11

Which LPFW heater can the BFT liquid be directed to?

Answer 11

3

Question 12

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

Answer 12

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

Question 13

What is used to cool the blowdown demin sample coolers?

Answer 13

Normal chill water WC

Question 14

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

Answer 14

LR TDS system

Question 15

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

Answer 15

CWNT

Question 16

How are the blowdown flow control valves operated?

What position do they fail in?

Answer 16

air operated

Fail closed on loss of air or power

Question 17

Where is the blowdown normally controlled from?

Answer 17

control room

Question 18

How is the BFT sized?

Answer 18

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

Question 19

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

Answer 19

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

Question 20

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

Answer 20

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

Question 21

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

Answer 21

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

Question 22

When would SCN-PV-4B be opened?

Answer 22

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

Question 23

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

Answer 23

Air operated

Fail open on a loss of air or loss of power

Question 23

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?

Answer 23

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

Question 24

What makes up the blowdown demin package?

Answer 24

2 mixed bed regen type units in series a filter that removes suspended solids from the blowdown liquid before demineralization

Question 25

What could cause the demin outlet valve (SCN-HV-3B) to auto shut? In this case how would we reestablish blowdown flow?

Answer 25

If that outlet valve is controlling BFT level and a high demin inlet temp is sensed Take switch to "BYP DEMIN MODE"

Question 26

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

Answer 26

The affected vessel is removed from service

Question 27

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

Answer 27

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

Question 28

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

Answer 28

25 psi

Question 29

What flows thru the tube side of the BDHX?

Answer 29

Condensate

Question 30

What is the outlet temp of the BDHX controlled at?

Answer 30

less than 135F

Question 31

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

Answer 31

To correct abnormal steam generator chemistry

Question 32

What is the SG blowdown systems role in SG wetlay up operations? 2) What would be different during wet layup cleanup operations?

Answer 32

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

Question 33

What else can we use the wet layup pumps for?

Answer 33

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

Question 34

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

Answer 34

220 psi

Question 35

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

Answer 35

Optimal flow @ 160gpm @ 180psi Maximum flow @ 220gpm @ 100psi

Question 36

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

Answer 36

located in containment next to the pumps on the 80' NH

Question 37

How is the system affected by the loss of IA?

Answer 37

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

Question 38

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

Answer 38

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

Question 39

How is the plant affected by loss of blowdown system?

Answer 39

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

Question 40

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

Answer 40

40%