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
_____Hi fast opens group __and ___ valves when on the plant trip controller.
15F
groups 1 and 2 valves
_____HiHi fast opens group __and ___ valves when on the plant trip controller.
30F
Groups 3 and 4
Load reject controller controls at ____ above Tave and the plant trip controller controls at _____above Tave.
3F
0F
The steam dump actuated light means that ______ and the steam dump armed light means that_____.
Any of the trip open temperature bistables has reached or exceeded its setpoint.
One of the arming circuits has armed the steam dumps.
The reset position of the mode select switch _______.
Resets the C-7
Normally steam dumps have a ___ second stroke time and will fast open in ____ seconds.
20
3
Group __ valves are the cooldown valves and can cool the RCS to <_____.
1 (A, E, J)
<550F
Load reject controller range from 0-100% demand is ____ and plant trip controller range from 0-100% demand is ______.
Load reject helpful hint:
Hint add 5.2 for hi 5.2 more for hi hi
Add4.4 for hi and 4.4 more for hi hi
10.4F (8.8F) (Accounts for the 3F at 0%)
30F
PK-507 (steam pressure controller) normally set at ______ and output is ___% demand for each ___ psi error.
1092#
1% demand for each 1 psi error
When is the Load Reject controller in service?
Steam Dumps in Tave Mode w/RTB or BYB closed
If a single Bypass/Interlock switch is placed in OFF, how many steam dump valves will NOT be able to open?
12 (No valves can open)
Loss of Instrument Bus 111:
Steam Dumps will not arm on a Load Reject (C-7)
