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MSR Effects Upon Secondary Cycle
MSR Effects Upon Secondary Cycle
###666
Heater Drain Pump
Main Steam
Main Turbine
#6 FWH
MSR
#5 FWH
#4 FWH
MOV
Drain Tank
Manual Valve
AOV
Note: Most plants have a Heater Drain Tank between the FWH and HDP
To LP Turbine
MSR Effects Upon Secondary Cycle
• There had been approximately 3 cycles (4-1/2 years) of continual FWH level alarms in the #4, #5 and #6 FWH.
• I&C would be sent at least once a week to try and adjust the tuning to stabilize the level control.
• Level control valves, positioners and diaphragms were experiencing degraded operation and pre-mature failures (Fisher V-Ball valves) due to the frequency and magnitude of the valve cycling.
• The level controllers were experiencing similar problems as the level control valves.
MSR Effects Upon Secondary Cycle
What was not heard or listened to?
• I&C stated that the controls were maintaining FWH level BUT there would be a surge in the level THEN the FWH level control would try to respond AND this surge would cascade through the FWH string!!
• The FWH level swings started WHEN we installed the new MSR’s!!
MSR Effects Upon Secondary Cycle
What given information do we need to validate our assumption(s)? FWH operation: What do we know about inlet flows? (extraction steam, cascaded & MSR drainage)1. Constant unit load results in constant extraction
steam flows.2. Varying inlet drain flows can cause erratic FWH levels
due to cascaded drainage from one FWH to the next.3. Varying flows from the MSR’s can occur due to drain
tank level control or some other anomaly in the MSR.
MSR Effects Upon Secondary Cycle
MSR operation: What do we know about inlet MSR drain flows? (2nd pass drain, 4th pass drain, separator drain)1. Constant unit load results in constant turbine exhaust
flow as well as the volume of moisture removed from the turbine exhaust steam flow. The separator drain flow must be constant.
2. 2nd pass drain flow was constant due to a stable level in the drain tank and stable level control valve position.
3. 4th drain flow could not be determined due to a lack of instrumentation.
MSR Effects Upon Secondary Cycle
###666
Heater Drain Pump
Main Steam
Main Turbine
#6 FWH
MSR
#5 FWH
#4 FWH
MOV
Drain Tank
Manual Valve
AOV
Note: Most plants have a Heater Drain Tank between the FWH and HDP
To LP Turbine
MSR Effects Upon Secondary Cycle
• MSR operation: How do we verify if the drain flow is stable and remembering that the problem of FWH level alarms started WHEN we installed the new MSR’s!!
• Reviewed EPRI TR-106345• Reviewed the scope of the MSR commissioning.• Based upon EPRI-We needed to verify if there is
condensate slugging from the 4th pass drain!!
MSR Effects Upon Secondary Cycle
• What was outcome of the performance of the manufacturer’s commissioning protocol (ASME Performance Test Code 12.4)?
• Answer: We did NOT satisfy the manufacturer’s protocol !! The protocol required achieving 10 to 20 F of sub-cooling and we had 0 F of sub-cooling!!
• Consulted EPRI publications 106345: MSR Source Book, 1003472: Level Control Guide for Feedwater Heaters, Moisture Separator/Reheaters, and Other Equipment
• Sub-cooling is the temperature difference between the saturated steam entering the heaters (1st pass) and the temperature of the condensate existing the MSR (4th pass).
MSR Effects Upon Secondary Cycle
###666
Heater Drain Pump
Main Steam
Main Turbine
#6 FWH
MSR
#5 FWH
#4 FWH
MOV
Drain Tank
Manual Valve
AOV
Note: Most plants have a Heater Drain Tank between the FWH and HDP
To LP Turbine
MSR Effects Upon Secondary Cycle
• >>>> CONDENSATE SLUGGING!!
• The manufacturer’s protocol was implemented to achieve 10 to 20 F of sub-cooling. (ASME PTC 12.4)
• We throttled the Manual Valve and monitor the manufacturer’s thermocouples to achieve approximately 20 F of sub-cooling.
MSR Effects Upon Secondary Cycle
Outcome:• We achieved closer to 20 F of sub-cooling.• The FWH levels stabilized.• Went from 30 to 50 level alarms per day to maybe
one or two a week-that as fast as the alarm annunciated-the alarm cleared.
• I&C was able to fine tune the FWH level control.• The stability of the turbine driven MFP improved
since the flow from the heater drain pumps stabilized.
MSR Effects Upon Secondary Cycle
• The MSR’s were 20% oversized for future EPU and there were further savings to be realized.
• The main steam flow was throttled to the MSR steam heater (reheater section) by closing the inlet AOV and throttling the MOV.
• Results: Achieved an additional 8 MWe!! NOTE: There is still more room to throttle to achieve further increase in MWe.
MSR Effects Upon Secondary Cycle
###666
Heater Drain Pump
Main Steam
Main Turbine
#6 FWH
MSR
#5 FWH
#4 FWH
MOV
Drain Tank
Manual Valve
AOV
Note: Most plants have a Heater Drain Tank between the FWH and HDP
To LP Turbine
MSR Effects Upon Secondary Cycle
Future Considerations: Achieved an additional MWe!!
• NOTE: There is still more room to throttle to achieve further increase in MWe.
• A graph of MWe verses valve position needs to be trended to determine were the peak in MWe occurs (Brayton Point) which would be the stopping point.
