MAIN STEAM Flashcards
What is the maximum tensile tube-to-shell ΔT for OTSG?
-70°F
What is the maximum compressive tube-to-shell ΔT for OTSG?
+60°F
What is the maximum allowable secondary pressure when OTSG secondary temperature is below 100°F?
200# (Tech Spec 3.1.2).
What is the limit for secondary coolant activity, and what actions must be taken if exceeded?
≤ 0.10μCi/g; if exceeded, be in Hot Standby (HSBY) in 6 hours and Cold Shutdown (CSD) in 30 hours.
How many MSSVs per OTSG are required between 250°F and Hot Standby?
At least 2 MSSVs per OTSG.
What is the required MSSV configuration for OTSGs between Hot Standby and 5% power?
At least 2 MSSVs per OTSG.
What are the MSSV requirements for OTSGs at different power levels?
- 6 MSSVs: 85.1% power
- 5 MSSVs: 70.1% power
- 4 MSSVs: 55.1% power
- <4 MSSVs: Restore in 4 hours or be in Hot Standby in 6 hours.
How many TBVs must be operable, and what is the restoration time if fewer are operable?
4 of 6 TBVs must be operable; restore in 72 hours (no shutdown action required).
What is the function of MS-V-1A/B/C/D valves?
They prevent blowdown of both OTSGs if a rupture occurs upstream.
How does Emergency Feedwater (EFW) enter the OTSG, and what is its purpose?
EFW enters through 7 upper nozzles to promote natural circulation by raising the thermal center and reducing thermal stress on the lower tubesheet.
At what pressures does MS-V-3 open during different operational states?
- 895# during startup (+10 bias)
- 960# during normal operations (+75 bias)
- 1010# during reactor trip (+125 bias)
- 1040# during kicker conditions.
What is the operating pressure range for MS-V-4?
MS-V-4 operates between 1026 – 1052# and closes on loss of air.
What happens to MS-V-4 control when ICS AUTO is lost?
MS-V-4 transfers to manual backup loader on loss of ICS AUTO.
When does control transfer from TBVs to ADVs?
Control transfers from TBVs to ADVs when vacuum is <23” or <2 CWPs.
What happens to TBVs and ADVs when a reactor trip and CVI occur?
TBVs go to HAND at 20%, and ADVs control at 20% based on previous demand.
At what vacuum level do ADVs resume control at 1026# post-trip?
ADVs resume control at 1026# when vacuum is restored to ≥23” post-trip.
What is the purpose of main steam heated posts?
They minimize movement due to piping expansion to prevent cracking under MSSVs.
What do TBVs and ADVs control on?
TBVs and ADVs control on OTSG outlet pressure at THP Setpoint + Bias.
How are MSIVs operated locally?
MSIVs are NOT jogged locally; the main disk closing is motor-controlled, with steam flow holding the disk open.
What action is required if L2204 MSIV is closed?
Reduce reactor power to <90%, re-open ASAP, or reduce power to <15% if it cannot be re-opened.
What should be done if the turbine trips on low condenser vacuum but the reactor does not trip (<45%)?
Ensure reactor trip and control OTSG pressure using ADVs.
