Term
| Function of pressure control system |
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Definition
| Operate turbine control valves and bypass valves to control reactor pressure and turbine speed. |
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Term
| Why is pressure control important? |
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Definition
Without pressure control, a rise in turbine demand, would open the control valves, which would drop pressure, reducing reactor power which would open the control valves further… In other words, the pressure control system provides a necessary feedback mechanism. |
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Term
| Range of mechanical pressure regulator |
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Definition
| per B-manual, 120 psig to 1050 psig |
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Term
| Range of electrical pressure regulator |
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Definition
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Term
| When is mechanical pressure regulator used? |
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Definition
| Due to its wide range, it is used during startup and shutdown. It is also used as a backup to the electrical pressure regulator (setpoint set higher). |
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Term
| Location and power supply to Electrical Pressure Regulator |
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Definition
| Location: Cable Spreading room; Power supply: Y-30 |
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Term
| Where can Pressure Regulator Override be operated? |
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Definition
| Panel C-07 or locally (front standard) |
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Term
| Discuss operation of the Pressure Regulator Override |
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Definition
| Can be used to manually open the control and bypass valves. May be used to vent the reactor and to establish steam flow through the bypass valves during startup provided the control valves are held shut by load limit or speed/load changer. If not, the PRO will fully open control valves first. |
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Term
| Discuss the flow limit control |
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Definition
| Mechanical stop in the control linkage system to limit the maximum opening of the control and bypass valves. Adjusted so that the total steam flow is restricted to slightly greater than reactor rated flow. |
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Term
| Describe the indicating lights on C-07 that show which of the three inputs (MPR, EPR, PRO) is controlling. |
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Definition
| Red light: controlling; Green light: Not controlling. It is possible to have two red lights). |
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Term
| Purpose of the speed governor |
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Definition
Acts on the error signal between turbine speed and the speed setpoint (as determined by the position of the speed/load changer) and positions the control valves to maintain proper turbine speed. NOTE: turbine speed is fixed at 1800 RPM when on the grid. |
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Term
| Function of Speed/Load Changer |
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Definition
Used for synchronizing the generator during startup and for turbine load demand once the generator is tied to the grid. Will not control below 95%. |
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Term
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Definition
| Limit the load on the turbine to any desired level. Normally used to open the control valves during startup until Speed/Load changer assumes control. Latched by turbine trip oil so if turbine trips, control valves automatically close. |
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Term
| What is the typical difference between EPR and MPR setpoint? |
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Definition
| No less than 10 psi and no greater than 18 psi. |
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Term
| When is a shutdown of EPR allowed? |
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Definition
| All pressure regulators are required unless reactor power is less than 25% or between 90 and 100%. |
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Term
| Discuss an EPR failure upscale |
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Definition
| EPR input to HVG1 will be negative which means that MPR will control. |
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Term
| Discuss an EPR failure downscale |
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Definition
| EPR will remain in control and control valves and bypass valves will open. Eventually scram will occur (after Group I isolation… 840 psig in run). |
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Term
| Summarize the MPR/EPR failures |
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Definition
| A failure causing one steam pressure signal to go up will result in other regulator controlling. A failure causing the steam pressure signal to drop will result in a high signal with no backup from the other regulator. Control valves will fully open, bypass valves will open. Group I isolation at 840 psig (in run) and automatic reactor scram (MSIV closure). |
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Term
| Per the C.4 for Loss of Pressure Control Resulting in a Drop in Steam Pressure, above what pressure difference between EPR and MPR would an automatic reactor scram occur upon securing the EPR? |
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Definition
Pushing the EPR STOP pushbutton on C-07 with MPR available will remove the EPR from service and Reactor pressure should increase to the MPR setpoint. If this action is taken when the difference between Main Steamline pressure and MPR setpoint is greater than approximately 15 psi, the resulting pressure transient will most likely result in an automatic Reactor Scram (on high neutron flux). |
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