Steam dumps Flashcards
Effect of losing ANY unit specific 125VDC bus:
Steam dumps will not open due to loss of power to at least one control solenoid.
Effect of loss of offsite power:
Loss of off site power, steam dumps will not open due to C-9.
If ‘A’ RTB fails to open on reactor trip:
Steam dumps control on Plant trip controller @557F if armed by load rejection (10% in 2 minutes).
If ‘B’ RTB fails to open on reactor trip:
Controls on load rejection controller @560F (3F error)
When does each steam dump open based on demand signal?
0-25% A, E, J
25-50% B, F, K
50-75% C, G, L
75-100% D, H, M
C-7 Loss of load setpoint, coincidence and function
10% decrease w/i 120 seconds on 2/3 coincidence (PT505, 506 and EH Pimp).
Arms steam dumps in Tave mode after load rejection.
C-9 Condenser available setpoint, coincidence and function
Condenser pressure >23” vacuum and CW brkr closed.
Condenser available for steam dumps.
P-12 Low-Low Tave setpoint, coincidence and function
<550F, 2/4, Blocks steam dumps. If 3/4 Tave exceeded 550F, the bypass interlock must be reactivated when 2/4 Tave lower to <550F.
What happens when the A-train reactor trip breaker auxiliary contacts open?
Arms steam dumps in Tave mode after plant trip.
The input to the ‘A’ solenoid is ___ and it receives power from DC bus ____.
P-12 ‘A’ Train
DC 113
The input to the ‘B’ solenoid is ___ and it receives power from DC bus ____.
P-12 ‘B’ train
DC114
The input to the ‘C’ solenoid is ___ and it receives power from DC bus ____.
Tave/Tref/no load Tave
DC113
The input to the ‘D’ solenoid is ___ and it receives power from DC bus ____.
‘Steam press’ position
Load rejection C-7
A-train RTB/BYB open
-and- C-9
DC113
There are _____ bypass interlock trn switch(es). The function of the off/reset position is____, the function of the on position is_____, and the function of the bypass position is_____.
2, train A and B
Off/reset blocks air to steam dump by de-energizing the A and B solenoids; also resets Lo-2 Tavg interlock being bypassed.
On- Steam dumps operate normally.
Bypass- Permits operation <550F using the 3 cooldown dumps, spring return to ‘on’.
Purposes of steam dump system: (5)
- Provide an artificial steam load
- Remove 40% load without actuation of SG safeties after a reactor trip, and bring plant to equilibrium.
- Control steam pressure at no-load conditions.
- Used when transient exceeds rod control design of >10% step change.
- Provide manual cooldown of plant.
Function of A and B solenoids:
Prevents excessive cooldown
De-energizes to block air from passing; block auto clear >550F
Function of C solenoid:
Normally ____ to pass air to D solenoid.
______ positioner on large error signals.
When_____ full IA changes stroke to ____ seconds.
Hi-1 bypasses groups ______
Hi-2 bypasses groups_______
Normally de-energized to pass air to D solenoid.
Bypasses positioner on large error signals.
When bypassed, full IA changes stroke to 3 seconds.
Hi-1 bypasses groups 1 and 2
Hi-2 bypasses groups 3 and 4
Function of D solenoid:
Normally de-energized; energizes to ARM passing air to B solenoid.
If the mode select switch is in STM PRESS, compares ____ to _____.
Validated 2nd highest steam pressure to desired steam pressure.
Steam dump armed light will be caused by: (3 items)
C-9 -and any of the following-
‘Steam press’ position
Load rejection C-7
A-train RTB/BYB open
Group 1 ____
Group 2 _____
Group 3 _____
Group 4 _____
1-A, E, J
2-B, F, K
3-C, G, L
4-D, H, M
Steam dump valves are ___ to open and ____ to close.
Air
Spring
_____Hi fast opens group __and ___ valves when on the load reject controller.
8.2F(7.4F) Hi fast opens group 1 and 2 valves
_____ HiHi Fast opens group _ and _ valves when on the load reject controller.
13.4F(11.8F) HiHi Fast opens group 3 and 4 valves
