Reactor Protection Flashcards
What is the RPS design Criteria?
- Reliable - redundant electronic systems ensure a scram will occur if a parameter exceeds its limit.
- Independent - redundant portions of RPS are separated so that no single failure or event can prevent a reactor scram.
- Fail Safe - a component malfunction, loss of electrical power or air will not prevent a scram.
- Testable - each channel, trip logic channel component, sensor etc. is testable without causing a scram or impairing the operability of RPS.
Describe the logic for the RPS system.
“1-out-of-2-taken-twice” - This means that one trip channel in each trip system must provide a trip signal to produce an actuation signal
What are the RPS bus loads?
1) Main Steam Line Radiation Monitors
2) NSSSS logics(A RPS to A&C NSSSS, etc)
3) RPS trip logics
4) Scram Pilot Solenoid Valves
5) Scram dump valves(both must deenergize to actuate)
Are the backup scram valves powered by RPS?
No, the P/S for these valves are energized from 1E 125VDC to isolate instrument air from and vent the scram air header. The RPS buses energize the solenoids to maintain air to the scram air header. ie, when you loose RPS, 125 DC moves the valves to vent.
What is the purpose of the flywheel?
Maintains generator within 5% of the output voltage and frequency during a <2 sec power disruption of the motor.
How do the EPA work?
EPA breakers are after the MG sets. If the 480VAC supply to the MG sets is lost, the RPS bus will deenergize within 1-3 secs. If the EPA breakers trip, the RPS bus is deenergized instantaneously.
What type of breaker operation is swapping an RPS power supply to alternate? what is the operational significance of this?
Alternate power is break before make. Taking the switch to ALT causes a half scram / Loss of RPS bus (including the RWCU NS4 iso.) and RPS sees >98.1# 1st stage pressure.
How can you bypass the scram discharge volume?
It is bypassed when the MSS is in S/D or Refuel to allows resetting the scram and the draining of the SDV.
What should be done if the main turbine is Shutdown or lost?
Ensure the EOC-RPT is bypassed prior to swapping RPS power or all of the EOC-RPT breakers will trip due to a loss of power to the transmitter that senses 98.1#. (No Scram)
What should be done if the main turbine is Shutdown or lost and you need to swap RPS power supplies?
Ensure the EOC-RPT is bypassed prior to swapping RPS power or all of the EOC-RPT breakers will trip due to a loss of power to the transmitter that senses 98.1#. (No Scram)
Why is there a time delay for the reset circuitry for a scram?
The 10 sec TD was built in to allow time for the rods to fully insert. The scram should be reset ASAP to protect the CRD seals.
Why is the MSS placed in S/D following a scram?
To bypass the <756# MISV closure.
What is the function of the Electrical Protection Assemblies (EPA) breakers?
To provide highly reliable power source to scram pilot valves. To protect the SSPV’s from damage due to a long term degraded power supply.
- Overvoltage - 10%
- Undervoltage - 10%
- Overfrequency - 5%
List the scram setpoints.
- RPV level Lo: +12.5”
- RPV Stm Dome: 1037#.
- Drywell Press: 1.68#
- IRM upscale: 120/125.
- IRM INOP: MU SO HVL.
- APRM STP Upscale (Flow Biased):
a. ≤0.56+58%
b. ≤0.56(W-10.8%)+58% for SLO
c. ≤113.5% of Rated Thermal Power - APRM Neutron Flux Upscale:
a. ≤17% of Rated Thermal Power
b. ≤116.3% of Rated Thermal Power - APRM INOP:
a. Mode switch not in OPERATE.
b. Firmware/Software WDT timed out.
c. Critical Self-Test Fault is detected. - SRM Hi-Hi: 200000 CPS
- SDV Level Hi:
a. North Header: 80.5” above inst. zero.
b. South Header: 83.25” above inst. zero. - MSIV Closure: ≤8 Closed
- TSV Closure: ≤5% Closed
- TCV Fast closure, EHC Trip Oil Pressure - LO: ≥530# EHC Trip Oil Press
- OPRM Trip: Detection of Thermal Hydraulic Instability.
if a single channel of logic is tripped/inop(ex A1) what will occur if the opposite side receives a half scram(any B side)
1/4 of control rods will scram
