SSPS Flashcards
Purpose:
Protect the plant with:
a. Reactor trip
b. ESF actuation
and provide MCB and plant computer with indications of these two functions.
D-R-I-F-T
Diversity- More than one method used to perform similar functions or indicate the same casualty. Multiple protections for DNBR.
Redundancy- Multiple components and systems available to respond to transients. Each parameter measured by more than one instrument. Spurious measurement will not cause or prevent required actuation.
Independence- Separation of trains, separation of channels. Single malfunction affects only one train or channel.
Fail-safe- Designed to supply safest signal on failure. Loss of power to a bistable will supply a trip signal.
Testability- System is capable of being calibrated or tested while in service with minimal loss of protection.
Slave relay power supplies:
A- Inst bus 111
B- Inst bus 114
SSPS interface- What generic components/cabinets make up SSPS?
- Input relay bay- divided into 4 compartments, one for each input to SSPS.
- Logic Bay- Contains circuitry which produces required action or rx trip on signal from input relays. Contains master relays.
- Output bay- Contains slave relays which are energized by safeguards boards to start equipment.
Input cabinet inputs:
- process instruments
- NI’s (120VAC from NI drawers)
- Field contacts:
a. Turbine throtlle valve positions, 4
b. EHC<1000 psig (3/train, 2 trains)
c. RCP breaker position
d. UV relays on RCP buses
e. UF relays on RCP buses
Protection cabinet power supplies:
Primary 120VAC instrument buses
Secondary 480VAC ESF MCC
SSPS power supplies:
48VDC used for :
-RX trip breaker UV coils (UV driver output)
-General warning circuit
-Master relay coils (safeguard driver output)
15VDC used for:
-Logic cards and circuits
-Slave relay testing
120VAC used for:
-Field contacts (supplied from input bays)
-Slave relay coils (via master relay contacts)
-Supply power for 15 and 48 VDC rectifiers
Purpose of input bay:
- Provides on/off signals to logic bay
- Provides isolation from plant instrumentation, and provides isolation between trains of parallel inputs to SSPS.
Purpose of logic bay:
- Evaluates inputs to determine if reactor trip and/or ESF actuation is required and delivers a signal to the output bay.
- Provides multiplexed signals to MCB and plant computer.
Output bay, description of master/slave relay setup
Master relays are actuated from input coming out of the logic bay. Master relays control the slave relays and the slave relays actuate the safeguards equipment.
Energize to actuate circuits
- RWST lo-2 level (46.7%)- Prevents inadvertent alignment of RWST valves.
- Containment Hi-3 pressure (20 psig)-Prevent inadvertent CS actuation.
- P-6 SR block permissive (1.0E-5% RTP) energize at power.
- P-11 PZR pressure low permissive (1930 psig). Energize at <1930 psig. Do not want to energize at power. If P-11 was energized at power circuit, and it was inadvertently de-energized, it would allow blocking steamline low press and pzr low press SI signals at >1930 psig.
Input error inhibit switch:
- Located in logic bay
- Inhibit position opens all circuits to logic ground, disabling all SSPS inputs on this train.
- Allows for testing and train restoration.
Inhibit switch isolates signal before they go to the ______. Output mode select switch is located in the _______ and switches the power source from _____ to _____ for testing.
Repositioning either switch generates a _______ signal.
Logic bay, reactor trips come off the logic bay.
Output bay
120VAC to 15VDC
General warning
48VDC is used in the ______ bay for ______and _______output drivers.
Logic
UV and Safeguard
The ______ switch allows a current flowpath around a _______ to keep its output energized. This is used for testing.
Bistable bypass
bistable
