Core Spray - 1.0 Flashcards
What is the design purpose of the CS system?
Designed to limit fuel cladding from exceeding 2200°F following a LOCA which rapidly depressurizes the RPV OR operates in conjunction with ADS when the RPV remains pressurized and H.P. sources are unable to maintain level.
Describe the arrangement of the CS system
2 loops with 2 pumps a piece
Where are the CS suction valves operated from and what interlocks are they associated with?
(HV-F001A/B/C/D) are remotely operated from the MCR and have no interlocks (no auto open, no pump trip scheme, etc.).
What are the CSS pumps rated for?
a) 50% capacity
b) Rated flow of 3175 gpm (6350 gpm per loop at 138.6 psid)
c) Shutoff head of 875 feet (approximately 385 psi)
When does the CSS pump auto start?
a) 1.68 PSIG Drywell
b) -129” RPV Level
c) Associated CSS Manual Init P.B.
What are the time delays for a CSS pump after CS initiation?
- With offsite power available (no LOP) - 10 seconds
- With offsite power not available (LOP) - 6 seconds after respective EDG output breaker closes.
(this logic is associated with the CSS logic, not the LOP/LOCA logic)
What is the sequence of events on initiation (Manual Arm and Depress or Auto) of the CSS?
- EDGs receive AUTO START signal, output breakers do not close.
- Non-1E loads are LOCA load shed and sequencer starts associated loads.
- PCIS isolations occur.
- CSS pumps start 10 seconds initiation signal.
- HV-F004A(B) and HV-F005A(B) (injection valves) open permissive(opens when drops below 461 psig)
- HV-F015A(B) (full flow test valve) CLOSES.
- HV-F031A(B) (CSS pump minimum flow valve) opens and then closes when flow above 775 gpm.
- CSS Logic INIT AND SEALED IN lights illuminate.
What is the only difference in the sequence of events for a CSS initiation during a LOP vs a LOCA?
the sequence of events without offsite power is the same as with offsite power available except that the CSS pumps start 6 seconds after the respective EDG output breaker closes
What is monitored for an input to ADS?
- Confirmatory for a L.P. ECCS system is running – needs both pumps running for a confirmatory signal
- Looks for 145 PSIG for both pumps in a loop (ADS needs at least one full loop running)
Describe the operation of the Min flow valve?
Each loop contains a minimum flow line, common for both pumps, via HV-F031A/B
1. OPEN if pump(s) running and flow <775 GPM [normally open]
2. CLOSE when flow >775 GPM
3. Normally are open
Describe the operation of the full flow test line.
H. Each loop contains a full flow test line, back to the Torus, via HV-F015A/B
1. Operated manually from MCR
2. Auto CLOSE on initiation signal
a) Auto close signal is from ‘A’ and ‘B’ channels of initiation logic
How many injection valves are there?
Each loop contains an Upstream and Downstream injection valve (HV-F004A/B & HV-F005A/B)
Explain the operation of the Upstream Injection Valve.
- HV-F004A/B is normally open
a) Auto open signal on CSS initiation AND RPV <461 PSIG
b) Must be closed to manually open HV-F005A/B (one-way interlock) [Close the 4 to open the 5, then open the 4 again]
c) F004 can NOT be overridden closed if logic is init/sealed in [1.68# or -129] – this logic may not actuate with a loss of a 481 inverter (since that supplies power to the trip units that initiate the logic - but not 482 – that’s just bailey logic and outer horseshoe lights). In the case of a loss of a 481 inverter and a valid initiation signal, the F004 never opens since the 481 never inputs to the 417 125vdc logic. Thus, the F004 must be closed, the F005 opened, then the F004 reopened, in order to inject
Explain the operation of the Downstream Injection Valve.
- HV-F005A/B is normally closed
a) Auto open signal on CSS initiation AND RPV <461 PSIG
1. Auto open signal can be overridden only when the auto open signal (initiation AND RPV <461 PSIG) is present
b) Cannot be manually opened unless HV-F004A/B is full closed (one-way interlock) OR CSS initiation AND RPV <461 PSIG
c) F005 can be overridden and closed on a LOCA (Open o/r only stays in while <461#)
d) If only one CS pump is operating in a loop the F005 should be throttled to prevent pump runout.
e) To override and close the F005, pressure must be below 461#. Press override and close valve.
f) F005A(B) only opens if there is power to the A(B) bus – the F005 is AC powered off the A(B) bus!
How is power supplied to reposition valves vs. the logic?
A/B 125vdc Logic is in control of repositioning the valves. F004/F005 A/B Powered from 10B212/10B222. (i.e. if ‘A’ Logic is lost during an initiation, the ‘C’ pump will start, but the valves on the ‘A’ side will not automatically reposition.)
