Chemical Volume & Control System Flashcards
(18 cards)
Where does Letdown come off the RCS?
Loop 3 Intermediate Leg
Describe LCV-0459 & LCV-0460 to include any interlocks and automatic actuations associated with these valves.
LCV-0459/460 are the letdown isolation valves. They are Air-operated DC solenoid valves that fail closed on a loss of air or a loss of power.
Auto Close:
- Train ‘A’ SI
- Low Pressurizer Level ≤17%
Interlocks:
- LCV-0459 and LCV-0460 can only be closed if all three letdown orifice isolation valves (u-8149A-C) are closed. In other words, LCV-0459/60 will not move until all three letdown orifice isolation valves are on their closed limit switch. The same is true for opening 0459/60.
Why:
- Low Pressurizer level: Isolates letdown to prevent uncovering the pressurizer heaters during a LOCA
- Letdown orifice: Prevents flashing the piping downstream of 459/460
Describe the 8160 and 8152 to include any interlocks and automatic actuations associated with these valves
8160 & 8152 are the letdown containment isolation valves. They are air operated DC solenoid valves that fail closed on a loss of power or air.
Auto-Close:
- Phase A containment isolation (actuated from SI)
Describe the properties of relief valve 8117 to include when it lifts, where it relieves to, and a general description of where it is in the system.
8117 lifts at 600 psig and relieves to the PRT. It’s located inside containment and taps off the common header at the outlet of the letdown orifice isolation valves.
Describe the operation of PCV-131
PCV-131 is a fail open air-operated valve that functions to maintain a backpressure (~310#) on the letdown heat exchanger to prevent flashing of the fluid between the letdown orifices and the letdown heat exchanger.
PCV-131 is also utilized in shutdown conditions to maintain the RCS solid.
PCV-131 is opened to decrease backpressure, and closed to increase backpressure.
Describe the properties of relief valve 8119 to include when it lifts, where it relieves to, and a general description of where it is in the system.
8119 lifts at 300 psig and relieves to the VCT. Its located just downstream of PCV-131 and before the GFFM.
Describe the operation of TCV-129
TCV-129 is a three-way air-operated valve that ‘opens’ to align flow through the CVCS demineralizers, and ‘closes’ to bypass the demineralizers.
Auto Bypasses:
- ≥135F Outlet of Letdown Hx
- ≥155F Inlet to BTRS Demineralizers
The VCT has two level channels, LT-112 and LT-185. Describe the inputs of these channels.
LT-112
- 98% Full divert to RHUT if in AUTO
- 70% Hi Alarm
- 62% Start of 112A Divert to RHUT if in AUTO
- 56% Stop auto makeup
- 46% Start auto makeup
- 16% Lo level alarm
- 2% Lo-Lo level alarm (1/2)
LT-185
- 98% LCV to HUT Hi Hi Alarm (Also causes divert)
- 70% Hi Alarm
- 16% Low level alarm
- 2% Lo-Lo level alarm (1/2)
(2/2) Lo-Lo coincidence to auto-swap CCP suction from VCT to RWST
What is the purpose of maintaining a hydrogen overpressure on the VCT
A hydrogen overpressure of approx. 20-25 psig is maintained on the VCT as an oxygen scavenger and provide NPSH to the charging pumps. Additionally, a pressure of >15 psig is necessary to maintain enough back pressure on the #1 RCP seal to force flow up to the #2 seal.
Describe the function of PCV-115 and any automatic actions
PCV-115 is used to align the VCT to the WGPS as needed to reduce pressure or for RCS degas operations.
Auto-Close:
- Low VCT # 14 psig
- Low WGC suction -0.5 psig
- Hydrogen recombiner low oxygen flow (valves closed)
Describe the train-relation and interlocks associated with LCV-0112B/D
LCV-0112B is interlocked with LCV-0112D (both are Train A related), and 8220
LCV-0112B will auto close:
- Lo-Lo (2/2) VCT level AND LCV-0112D is OPEN
- Train A SI signal AND LCV-0112D is OPEN
When LCV-0112B closes, 8220 the CCP High point vent to VCT will close as well.
Describe the train-relation and interlocks associated with LCV-0112C/E
LCV-0112C is interlocked with LCV-0112E (both are Train B related), and 8221
LCV-0112C will auto close:
- Lo-Lo (2/2) VCT level AND LCV-0112E is OPEN
- Train A SI signal AND LCV-0112E is OPEN
When LCV-0112C closes, 8221 the CCP High point vent to VCT will close as well.
List the auto-starts and trips for a CCP
Auto-start:
- Train related BOS start signal
- Train related SI with SIS start signal
Trips:
- Bus undervoltage
- 86M lockout on the motor
What are the normal and alternate miniflow paths for the CCPs, how much can either flow? What minimum must be maintained?
The normal miniflow for the CCPs is approximately 72gpm; 60gpm via 8110/8111 and 12gpm from RCP seal return.
Alternate miniflow for the CCPs is approximately 84gpm (per pump) through 8511/12 A&B via a relief valve to the RWST
Describe the function of the PDP to include power supply, operational concerns, and trips
The PDP is one of three charging pumps and is powered from uEB1. Its speed controller should be set at approx. 55% (55 gpm) to ensure that LO pressure is greater than 4 psig. The speed controller fails high on loss of air pressure.
To start:
- 8109 (PDP Recirc valve) must be open
- No OL from Train A SI or BO is present
Trips:
- Low lube oil pressure (4 psig)
- Train A SI (load shed)
- Bus undervoltage
- Overcurrent
Describe the function and operation of FCV-121
FCV-121 is a fail open AOV and it is responsible for controlling charging flow at the outlet header of the CCPs.
Alarms:
- Hi flow ≥150 gpm
- Lo flow ≤55 gpm
In auto, the controller (FK-121) modulates charging flow by comparing actual flow to an input setpoint from the pressurizer level control system. The controller, in auto, limits valve position to a minimum flow of 55 gpm. In manual, the valve can be fully closed.
What are the normal positions of 8511A/B and what conditions must be met for these valves to re-position?
8511A/B are normally closed valves. They auto-open on an SI signal to align the CCP alternate miniflow to the RWST through two relief valves set to lift at 2200#.
8804A RHR to CCP suction & 8804B RHR to SIP suction are interlocked with 8511A/B such that 8804A/B, must be closed before 8511A/B are opened to prevent sending ‘potentially’ contaminated water from the RHR system back to the RWST.
Upon receiving an SI signal, describe how the CVCS system responds including general scope and valve-repositions.
After receiving an SI, letdown isolation valves LCV-0459/460 go closed, and normal charging isolation valves 8105/6 closed, isolating normal letdown and charging.
The subsequent Phase A actuation isolates the letdown containment isolation valves 8160 and 8152, and the RCP seal return containment isolation valves 8112 and 8100.
CCP suction swaps from the VCT to the RWST (112D/E come open before 112B/C close). Closure of 112B/C result in closure of the charging pump suction vent valves 8221 and 8220.
CCP alternate miniflow valves 8511A/B open as long as 8804A/B are closed
8801A/B open and CCPs inject through SI injection flowpath.
