Systems Exam 2 - Reactor Coolant System Flashcards
RCP Start Permissive
→ ≥600# Lift Oil pressure
→Oil Lift Pump running to start RCP (Oil Lift pump manually S/D > 1 minute after RCP starts)
What is the purpose of “Hot Loop/Cold Loop” control switch on RCP Breaker?
The “Hot Loop/Cold Loop” control switch used when starting RCPs
→”Cold Loop” position enables the “Locked Rotor” and “Failure to Accelerate” trips.
→”Hot Loop” blocks those trips to prevent a single point trip during normal plant operation in the event of a failed fuse
RCP Trip Criteria (per ABN-101)
→Motor Bearing Temp > 195°F
→Motor Stator Winding Temp > 300°F
→Low Seal Water Bearing Temp > 225°F
→Seal Water in Temp > 235°F
→Loss of CCW Flow to Motor (Trip RCP w/in 1 minute)
→Loss of Seal Injection AND Thermal Barrier cooling
→Shaft vibration at 15 mils and increasing at > 1 mil/hr OR 20 mils
→Frame vibration at 3 mils and increasing at > 0.2 mils/hr OR 5 mils
PRT Level band, pressure band, temp, rupture disc pressure?
→Filled 64-88% with reactor makeup water with a 1-7 psig nitrogen atmosphere and maintained <113°F
→Discharge into the PRT is through a sparger pipe beneath the water level
→Provided w/ 2 rupture discs @ 91 psig
→Normally cooled via RCDT HX
Design temp of RCS
650°F, except for the PZR and its surge line, which is 680°F
An RCP trip will also cause the associated SG to…
shrink and steam flow to drop off due to no heat transfer.
Which RCP provides the best spray flow characteristics?
4 RCP. It is desirable to ensure it is kept available.
What cools the RCPs?
At what temperature/flow do the RCP Thermal Barrier return lines isolate?
→RCPs are cooled by CCW
→the motor portion and thermal barrier portions have separate return lines and a common supply line
→Thermal Barrier return lines isolate on:
→high temperature 182.5°F on each pump (IRC) and uHV-4709 (ORC)
→high flow 64 gpm on uHV-4696 (IRC).
(The arrangement on the flow diagram is “TFT”)
For the #1 seal, what is the temperature limitation?
Seal injection temperature should be kept less than 130°F to the #1 seal.
How much seal leakoff flows up vs down the RCP shaft?
Approximately 3 gpm flows up the shaft, lubricating the radial bearing and leaking through the No. 1 seal and 5 gpm flows down the shaft, through the thermal barrier heat exchanger, and into the RCS.
Core Bypass Flow values
→ ~94% of the reactor coolant flow is available for heat removal; ~6% bypasses the core
The other 6%:
→2% - Control rod & instrument thimble bypass flow travels through the control rod guide and instrument thimble tubes of the fuel assemblies
→2% - Baffle cooling flow is the water that enters the baffle and former plate region just above the lower core plate and travels upward, removing heat, and exits the baffle and former plater region just below the upper core plate
→1% - Nozzle bypass flow travels directly from the inlet nozzles to the outlet nozzles.
→0.5% - Baffle wall bypass flow passes between the inside of the baffle wall and the fuel assemblies.
→0.5% - Head cooling bypass flow passes through holes drilled in the upper support structure flange & core barrel flange.
Normal RCS Parameters:
→Volume: 95,000 (91,000) gal
→Flow Rate 403,700 (408,000) gpm
→Pressure 2235 psig
→T-hot 618°F (620°F)
→T-cold 560°F (559°F)
→T-avg 557-585.4 (589.2)
→PZR Level 25%-60%
Requirements to open #1 seal bypass valve
The No. 1 seal bypass valve should not be opened unless either the pump bearing temperature approaches 225°F or the No. 1 seal water inlet temperature approaches 235°F. These are also RCP trips.
The No. 1 seal bypass valve (u8142) should then be opened only if all of the following conditions are met:
→RCS pressure is between 100 psig and 1000 psig.
→No. 1 seal leakoff valve is opened.
→No. 1 seal leakoff flowrate is less than 1 gpm.
→Seal injection water flowrate to each RCP is at least 8 gpm.
Pressurizer PORVs N2 Accumulators rating
→2 PORVs controlled by PZR Pressure Control System
→210,000 lbm/hr each
→use N2 for motive force
→supplied w/ N2 accumulators to allow associated valve to be stroked 100 times in 10 min
Mode 4 and 5 RCP start limitations
An RCP shall not be started in Mode 4 or 5 with any RCS cold leg temperature ≤350°F unless the secondary water temperature of each steam generator is <50°F above each of the RCS cold leg temperatures. (TS 3.4.6 and 3.4.7)
RCP Motor Start Requirements
Per SOP-108:
1. Two successive starts are permitted, provided the motor is allowed to coast to a stop between starts (5 minutes).
2. A third start may be made when the winding and the core have cooled by running a period of 20 minutes, or by standing idle for a period of 45 minutes.
3.Only one RCP is to be started at any one time
RCP Start Motor Oil Lift Interlock
There is a permissive interlock in the RCP motor start circuit that does not allow the RCP to be started until the oil lift pressure has reached 600 psig (Blue Light) and oil pump running. Admin time of 2 minutes running prior to start.
Are there any auto starts for the Oil Lift Pumps?
There are no auto start features for oil lift pumps, if the RCP trips or is stopped the thrust bearing will maintain its oil wedge on coast down
PZR Safeties:
→lift setpoint
→rated flow
→design function
→3 Safeties, 420,000 lbm/hr each, lift setpoint 2460#
→Designed for the maximum surge rate resulting from a complete loss of steam flow to the main turbine without a Rx Trip, auto rod control, steam dumps, PORVs or operator action
→Temp indication provided downstream of PORVs (common for both) and downstream of each safety, alarms provided at 140°F.
→Position indication use magnetic reed switches to indicated either fully open or fully closed.
RCP Trip Criteria (ABN-101) for seals
1 Seal Leakoff problems:
→Leakoff > 6 gpm w/ total leakoff between 6 and 8 gpm AND Pump Brg/ Seal Inlet Temp increasing: immediate S/D
→Leakoff > 6 gpm w/ total leakoff between 6 and 8 gpm AND Pump Brg/ Seal Inlet Temp stable: orderly S/D
→Leakoff < 0.8 gpm w/ total leakoff < 0.8 gpm AND Pump Brg/ Seal Inlet Temp increasing: immediate S/D
→Leakoff < 0.8 gpm w/ total leakoff < 0.8 gpm AND Pump Brg/ Seal Inlet Temp stable: orderly S/D
→Leakoff > 8 gpm: immediate S/D
TS Minimum loop temp for criticality
TS 3.4.2 Minimum loop temp for criticality is ≥551°F, or be in MODE 2 with keff < 1.0 within 30 min
What are some indications that natural circulation is occurring?
- RCS sub cooling - GREATER THAN 25°F (55°F FOR ADVERSE CONTAINMENT).
- SG pressures - STABLE OR DECREASING.
- RCS hot leg temperatures - STABLE OR DECREASING.
- Core exit TCs - STABLE OR DECREASING.
- RCS cold leg temperatures - AT SATURATION TEMPERATURE FOR SG PRESSURE.
Define reflux boiling
Reflux boiling is characterized by boiling core water and condensing steam in the SG with flow back through the Hot Legs.
PRT Rupture Disc
The tank is protected against a discharge exceeding the design value of 100 psig by two rupture discs, set at 91 PSID, if containment press is 10 psig then lifts at 101 psig in PRT, up until this time a stuck open PORV will drop RCS pressure at a decreasing rate and then suddenly increase as the rupture disc fails
