-
Unit Two is operating 100% power with normal EHC configuration. Which of the following EHC system controls, if inadvertently operated by 20% in the lower direction, could cause a reactor scram due to high reactor pressure and/or high neutron flux caused by void collapse?
A. Load set.
B. Load limit.
C. Pressure set.
D. Max combined flow.
D. Max combined flow.
Operating load set or load limit in the lower direction would cause that signal to becomeLimiting at the EHC pressure load LVG. This would cause control valves to close as the signal is lowered, but also cause bypass valves to open to maintain constant pressure (as soon as TCV valve demand starts dropping, BPV demand rises). Operating pressure set in the lower direction would cause TCVs to open and reactor pressure to drop until a group 1 would occur on low steamline pressure. Lowering max combined flow would cause that signal to become limiting at the EHC pressure load LVG without the delta being sent to BPVs.
-
Unit Two is operating steady state at power with the following EHC configuration:
Reactor Pressure 1030 psig
EHC Pressure Setpoint 945 psig
PAM Pressure 970 psig
Pressure Regulator A In control
Pressure Regulator B 3 psig bias
The Pressure Averaging Manifold (PAM) pressure input to Pressure Regulator A fails low. The PAM pressure input to Pressure Regulator B is unaffected.
How will the EHC system respond?
A. Pressure regulator B takes control and PAM pressure stabilizes at 967 psig.
B. Pressure regulator B takes control and PAM pressure stabilizes at 973 psig.
C. Control valves close, reactor pressure and neutron flux rise, and the reactor scrams.
D. Control and Bypass valves open and steam line pressure drops to the group 1 isolation setpoint.
B. Pressure regulator B takes control and PAM pressure stabilizes at 973 psig.
The output of pressure regulator “A” & “B” is routed through a high value gate with a positive bias on regulator “B” pressure set signal. This means regulator “B” is normally calling for a smaller valve demand than regulator “A.” If “A” fails low, TCVs would start to close, and PAM pressure would start to rise until the “B” regulator output equals the previous “A” output (a rise in pressure of 3 psig). “C” would be correct if there was no backup regulator, and “D” correct if A regulator failed high.
-
Which one of the following identifies the reason that the Turbine Bypass Valves will open following a main turbine trip from full power?
A. Prevent overspeeding of the main turbine during the coastdown.
B. Prevent over pressurization of the MSR cross-over piping.
C. Prevent over pressurization of the reactor vessel.
D. Prevent rupture of the LP Turbine rupture discs.
C. Prevent over pressurization of the reactor vessel.
-
Which one of the following identifies the parameter that provides a direct input into the
RPS logic (i.e., does not actuate a turbine trip logic first)?
A. Control Valve Position LVDT
B. EHC Low Header Discharge Pressure
C. ETS (Emergency Trip System) Pressure
D. RETS (Relayed Emergency Trip Supply) Pressure
D. RETS (Relayed Emergency Trip Supply) Pressure
-
Unit Two is in power ascension following a refueling outage.
Reactor power is currently 22%.
The generator has been synchronized with the grid.
Load Limit is set to 110%
GP-04, Increasing Turbine Load to Rated Power, directs increasing turbine Load
Set to 100%.
If the RO adjusts Turbine Load Set to 90%, which one of the following predicts how the plant will respond as reactor power is raised?
A. When turbine load exceeds 90%, reactor pressure will increase and cause a reactor scram.
B. When reactor power reaches 1OO°A> then turbine load will be 100%.
C. When turbine load exceeds 90%, bypass valves will open to control turbine inlet pressure.
D. When turbine load reaches 90%, bypass valves will open causing a Group I Isolation.
C. When turbine load exceeds 90%, bypass valves will open to control turbine inlet pressure.
Load Set is a reference signal set from the RTGB. When sensed turbine load reaches the Load Set setting, additional turbine load is restricted. Any additional steam produced as a result of continuing to raise reactor power is diverted to the condenser via bypass valves.
-
Unit Two is operating at rated power with EHC Pressure Regulator B out of service.
Pressure Regulator A output fails low.
Which one of the following identifies how reactor pressure will respond and also identifies the availability of the bypass valves following the reactor scram?
A. Reactor pressure will decrease and a scram will occur on a Group I Isolation. Bypass valves are not available using the Bypass Valve Jack.
B. Reactor pressure will increase and a scram will occur on high pressure. Bypass valves will still be available using the Bypass Valve Jack.
C. Reactor pressure will decrease and a scram will occur on a Group I Isolation. Bypass valves will still be available using the Bypass Valve Jack.
D. Reactor pressure will increase and a scram will occur on high pressure.
Bypass valves are not available using the Bypass Valve Jack.
B. Reactor pressure will increase and a scram will occur on high pressure. Bypass valves will still be available using the Bypass Valve Jack.
- This will cause steam flow to be restricted, reactor pressure to increase, and reactor power to increase
- due to void concentration. The result will be a reactor scram on either high pressure or high flux.
-
Unit 2 is at 96% power with the following EHC conditions:
Reactor pressure 1030 psig
EHC pressure setpoint 945 psig
PAM pressure 970 psig
Pressure Regulator A in Control
Pressure Regulator B in Standby (3 psig bias)
Pressure Regulator A output fails high.
How will the EHC system respond?
A. Pressure Regulator B takes control and stabilizes pressure at 967 psig.
B. Pressure Regulator B takes control and stabilizes pressure at 973 psig.
C. Control Valves close causing reactor pressure and neutron flux to rise causing a reactor scram.
D. Control and Bypass Valves open and steam line pressure lowers to the Group 1 isolation setpoint.
D. Control and Bypass Valves open and steam line pressure lowers to the Group 1 isolation setpoint.
|
|
