Heater Drains and Extraction Steam

Question 1

What is the steam load created by the MSRs?

Answer 1

3-5%

Question 2

What is the function of Ramp mode on the MSR control?

Answer 2

Regulates the opening of the 6” steam control valves over a 2 hour period. This rate ensures there is an acceptable rate of differential expansion between the LP Turbine casing and the rotor.

Question 3

When is the Ramp mode on the MSR control used?

Answer 3

When turbine load reaches 30%

Question 4

What is the function of the 400 F mode on the MSR control?

Answer 4

Maintains LP Turbine inlet steam temperature at 400 F to prevent overheating the last 2 rows of blades in the LP Turbine at continuous operation below 10% load

Question 5

When is the 400 F mode on the MSR control used?

Answer 5

When turbine load is reduced to 10% or less

Question 6

What is the function of the manual setpoint knob on the MSR control?

Answer 6

Opens reheater control valves to some position immediately. The operator is manually ramping temperature by use of a procedural table

Question 7

How do the MSR steam control valves respond to a turbine trip?

Answer 7

Automatically close to prevent flooding of the reheater drain tanks and E-6A/B

Question 8

How does the T-5/E-5A/B pressure control system operate?

Answer 8

• There is an equalizing valve open between T-5 and E-5A/B.
• D/P is monitored between T-5 and E-5A/B.
• Upon loss of turbine load, pressure drops in the E-5A/B shells.
• To avoid a corresponding pressure drop in T-5, and flashing in the Heater Drain Pumps, the equalizing valve closes, and when it’s 25% closed, subcooling valves open from the Condensate Pumps to the suction of the Heater Drain Pumps.
• Check valves in the lines from E-5A/B to T-5 close to complete the isolation when T-5 pressure is higher than E-5A/B pressure.
• Equalizing valve modulates to maintain E-5A/B pressure greater than T-5 pressure.

Question 9

How is T-5 normal level maintained?

Answer 9

Normal level control valve CV-0608 modulates to maintain T-5 level 60-65%

Question 10

What happens on a T-5 high level condition?

Answer 10

At 80%, high level dump to the condenser opens to restore level

Question 11

What is the interlock between T-5 level control and the MFPs?

Answer 11

MFP low suction pressure of 270 psig overrides normal level control signal, and causes normal level control valve CV-0608 to fail open.

Question 12

What is the design capacity of the Heater Drain Pumps?

Answer 12

6100 gpm @ 350 psig

Question 13

What are the power supplies for the Heater Drain Pumps?

Answer 13

P-10A/B both powered from Bus 1E

Question 14

What causes the Heater Drain Pumps to trip?

Answer 14

• T-5 low level (P-10A trips @ 12.8%, and P-10B trips @ 22.5%)
• Overcurrent
• Indirectly from SIS, due to Bus 1E being load shed

Question 15

What provides seal cooling and subcooling water to the Heater Drain Pumps?

Answer 15

Condensate Pumps P-2A/B

Question 16

What is the purpose/function of the Bleeder Trip Valves?

Answer 16

Stop check valves held out of the steam flow by air, installed on the drain lines from the turbines to E-3A/B, E-4A/B and E-6A/B. Close on turbine trip or high level in the associated heater to prevent water intrusion into the turbines.

Question 17

What are the plant requirements for bypassing feedwater heaters?

Answer 17

• If heaters are bypassed with the plant online, they are to be bypassed before the load reduction.
• If any 2 stages of heaters are bypassed, turbine load is restricted to 600 MWe to prevent excessive extraction steam velocity in the next higher pressure heater.

Question 18

What are the plant requirements for bypassing either E-5 feedwater heater?

Answer 18

The associated E-6 feedwater heater is required to be removed from service, and turbine load is restricted to 600 MWe

Question 19

What are the plant requirements for bypassing either E-6 feedwater heater?

Answer 19

Power level shall be lowered to at least 3% less than maximum permissible power level to prevent exceeding maximum permissible power level due to the introduction of colder feedwater

Question 20

What are indications of a feedwater heater tube leak?

Answer 20

• Lowering drain temperature due to higher pressure, but relatively lower temperature condensate/feedwater flowing through the tubes of the heater.
• Rising drain rate (LCV open farther than normal).
• Lower MFP suction pressure
• Higher Condensate Pumps amps