SC- Steam Generating Blowdown

Question 1

What is the purpose of the SC blowdown system?

Answer 1

To compensate for the impurity concentration effect on the steam generators by continuous blowdown and processing of a portion of the fluid from each steam generator

Also maintains the steam generator in wet lay-up by providing the capability to adequately mix, sample, and add chemicals to the S/Gs

Question 2

What are the three different types of S/G blowdown flow rates used?

Answer 2

Normal, Abnormal, and High Rate

Question 3

Where are the three S/G Blowdown connections on the Steam Generator and what does each line have?

Answer 3

Hot leg blowdown, Cold Leg Blowdown line, and Downcomer Blowdown line

Each line has two automatic Containment Isolation valves that will isolate the Blowdown system on actuation signals from PPS (AFAS, MSIS, SIAS)

Question 4

Which S/G blowdown line is the primary connection used?

Answer 4

Downcomer Blowdown

Question 5

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

Answer 5

Heater Drain Tank equalizing line or the Condenser

Question 6

What happens to the liquid in the Blowdown 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? What happens if radioactive concentration gets above a predetermined setpoint?

Answer 7

Steam Generator Overboard piping

To the retention tanks

Isolation valve will automatically close

Question 8

What provides cooling to the S/G Blowdown Heat Exchanger?

Answer 8

CD system

Question 9

What is used to backflush the S/G blowdown basket strainer?

Answer 9

DS

Question 10

Which LPFW heater can the Blowdown Flash Tank liquid be directed to?

Answer 10

3

Question 11

Where is the condensate cooling water for the S/G BDHX returned to?

Answer 11

Discharge of the ED pump just prior to the suction of the Main Feedwater pumps

Question 12

What is used to cool the S/G blowdown demineralizer sample coolers?

Answer 12

Normal Chill Water

Question 13

If there is activity present in the S/G B/D low TDS sump, where can I send it to?

Answer 13

LR TDS system

this path is used during a S/G tube leak

Question 14

The SGBD demineralizers high TDS sump is normally pumped to what location?

Answer 14

Chemical Waste Neutralizing Tank

Low TDS sump can also be pumped here

Question 15

Where are the S/G Blowdown Flow Control Valves located?

Answer 15

in separate blowdown lines, 100’ Turbine Building west side

Question 16

How are the S/G Blowdown Flow Control valves operated and what position do they fail to?

Answer 16

Air operated

Fail closed on a loss of air or power

Question 17

Where is the S/G blowdown normally controlled from?

Answer 17

Control Room

Question 18

Where is the Blowdown Flash Tank located? What is its purpose?

Answer 18

140’ Turbine Building

to collect blowdown liquid from both S/Gs and allows the liquid to flash prior to processing by the filter and B/D demins

Question 19

How is the Blowdown Flash Tank sized?

Answer 19

For processing continuous abnormal rate blowdown from one steam generator, and normal rate from the other steam generator

Question 20

Where can the liquid flow go downstream of the Blowdown flash tank and what is the purpose of the outlet valves to each flow path?

Answer 20

the outlet valves maintain level in the BFT

the flow paths are:

to the #3a/b/c LPFWHs

to the BDHX and to either through the B/D filters to the B/D demins or from the BDHX to the retention tanks

Question 21

What is the blowdown flash tank pressure control valve to HDT equalizing line, SCN-PV-4A and what does it do?

Answer 21

A pressure regulating valve in the vapor line from the flash tank

Maintains flash tank pressure at a nominal setting of 200 psig, but may be adjusted by the operator

Question 22

When would blowdown flash tank pressure control valve to the condenser, SCN-PV-4B, be opened?

Answer 22

When both Heater Drain Tanks are out of service or it is desirable to discharge the vapor directly to the condenser, the isolation valves downstream of SCN-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 two BFT pressure control valves operated and what is their fail position?

Answer 23

Air operated

Fail open on a loss of air or loss of power

Question 24

After plant power is changed by greater than 5%, why do operating procedures direct the NLO to close the Blowdown Flash Tank to the Heater drain Tank Equalizing Line valves?

Answer 24

To reduce Secondary Chemical Hideout by having all blowdown that ends up in the flash tank to go to the condenser

Question 25

What makes up the Blowdown Demineralizer package?

Answer 25

Two mixed bed, regenerative resin type units operated in series

A filter removes suspended solids from the blowdown liquid before demineralization

Question 26

Where is the S/G Blowdown Demin Package located?

Answer 26

North Yard of the Turbine Building

Question 27

What could cause the S/G blowdown Demin bed Outlet Valve (SCN-LV-3B) to shut automatically? In that case, how could I reestablish blowdown flow?

Answer 27

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

Take switch to BYP DEMIN MODE

Question 28

What happens if High Sodium, > 1 ppb, is detected in one of the S/G blowdown demin vessels and both vessels are in service in the AUTO STOP mode?

What happens if just one vessel is in service in the auto stop mode and a High Sodium is received? what if it was in manual stop mode

Answer 28

The affected vessel will be removed from service

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

chemistry must sample prior to removal from service

Question 29

What would happen if there was a high D/P across an in-service S/G blowdown demin vessel?

Answer 29

it will need to be removed for regen

Question 30

What is outlet temperature of the S/G BDHX controlled at? How?

Answer 30

<135F

by throttling the cooling water outlet valves

Question 31

When would be a situation where the Abnormal Rate Blowdown would be used in the SC system?

Answer 31

To correct abnormal steam generator chemistry

Question 32

What is the S/G Blowdown System’s role in SG wet layup operations?

Answer 32

Water from the SG is re-circulated using the SG Wet Layup Pumps. This water is pumped from the SGs through 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 layup operations

Question 33

What would be different during Wet layup cleanup operations, compared to the regular wet layup?

What else can we use the Wet Layup recirc pumps for?

Answer 33

Water from the SG is re-circulated using the SG Wet Layup Pumps. This water is pumped from the SGs through the Blowdown lines and recirculated back to the SGs via the downcomer lines, except the water is processed through the Blowdown Demineralizers prior to returning to the SG downcomer lines

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

Question 34

Where are the switches for the S/G wet layup Recirc pumps located and where do they get power from?

Answer 34

Located in the containment next to the pumps on the 80’

NH

Question 35

How is the SC blowdown system affected by a loss of Instrument Air?

Answer 35

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 Pressure Control Valve to Cond fails open

Question 36

How is the SC blowdown system affected by a loss of Condensate flow to the Blowdown Heat Exchanger?

Answer 36

Inlet water temperature to the Blowdown Demins will rise to the point that the Demin outlet valve will automatically close

Blowdown is secured to prevent overfilling and over pressurizing the BFT

Question 37

How is the plant affect by a loss of the SC Blowdown System?

Answer 37

While at power, this will cause increased corrosion rates in the SGs. This will require the chemistry department to issue Chemistry Control Instructions to the Control Room staff that can include performing an immediate shutdown as quickly as safe plant operation permits

Demand for SG feed will drop during a loss of blowdown

Question 38

How much of the S/G wet layup recirculation water enters the tube bundle area of the SG through the recirculation line?

Answer 38

40%

Question 39

Where is the effluent of the S/G blowdown demins directed?

Answer 39

‘A’ condenser

Question 40

Can the S/G blowdown demin low TDS sump be discharged to the circ water return line?

Answer 40

yes

Question 41

Does each steam generator have a blowdown flow path directly to the condenser?

Answer 41

yes

Question 42

Concerning the S/G blowdown flow control valves, when in high rate blowdown, which blowdown valves are open?

Answer 42

high and abnormal flow

Question 43

What is potentially caused by a misalignment of the S/G blowdown flow control valves?

Answer 43

cause the plant to exceed the power operating limits

Question 44

Concerning the S/G blowdown demin package, there is additional piping and controls for what?

Answer 44

air mixing the vessels, pre-service rinse of the vessels, bypassing the vessels, and for aligning the vessels by themselves or in series lead and lag

Question 45

Why was a second filter installed upstream of the S/G blowdown demin vessels?

Answer 45

to enable taking one out of service without affecting blowdown flow rate

Question 46

Where is the S/G BDHX located?

Answer 46

plant south of the B/D demins

Question 47

When the S/G blowdown demins are out of service, what system has to be in-service?

Answer 47

CD demins are needed to process the S/G blowdown

Question 48

What is the advantage of the S/G wet layup recirc piping arrangement?

Answer 48

the recirc line supplies 40% of the wet layup recirc water to the tube bundle area of the S/Gs

this line taps off of the aux. feed line before it enters the S/Gs

it would be more efficient to have more flow through this path but that would require more valves, which is against plant design due to single failure of a valve and aux. feedwater is isolated from the S/G

Question 49

How is the SC blowdown system effected by a loss of the CD system?

Answer 49

loss of cooling flow to the S/G BDHX, increasing the inlet temperature to the BD demins which isolates the demin vessels and will secure B/D

Question 50

Each S/G blowdown containment penetration is equipped with an “A” train and a “B” containment isolation valve that is controlled by Tech. Specs. How do these valves operate and what auto closes them?

Answer 50

air to open, spring to close

fail closed on a loss of air or power

also close on SIAS, MSIS, AFAS

Question 51

What is the difference between the S/G B/D containment isolation valves and the blowdown sample line containment isolation valves?

Answer 51

nothing, valves operate and fail closed the same way

Question 52

When are the S/G wet layup pumps isolated and in-service?

Answer 52

isolated at power, in-service during shutdown to maintain chemistry

Question 53

In regards to the S/G wet layup recirc pumps, describe the operation during outages.

Answer 53

S/Gs filled to narrow range level with AF and N2 blanket

pumps mix and clean up system water

can take suction from hot leg, cold leg or downcomer blowdown lines

can take suction on either S/G and return water to either, but only one at a time for single pump

Question 54

Where are the S/G blowdown recirc wet layup pumps located?

Answer 54

80’ containment

Question 55

What is the method of putting SC blowdown sight glasses in-service?

Answer 55

allow the sightglass to adjust to system temp and pressure by slowly opening the isolation valves with the vent open, when glass is filled, close vent

repeat until gauge is system temp., check for leakage