EHC - .5 Flashcards
How much does the EHC reservoir hold?
800 gal
What is the setpoint for the EHC relief valves?
2000#
What is the normal system pressure for EHC?
1600#
At what pressure does the standby EHC pump start?
1300#
At what EHC system pressure will the turbine trip?
1100#
List the power supplies for the EHC pumps?
‘A’ - 10B112
‘B’ - 10B141
What happens when EHC pump strainer is dirty?
Internal bypass opens.
List the number of accumulators and their loads. in the EHC system.
6 @ reservoir skid for transient pressures.
3 @ BPVs for transients. rated to hold (can also open) all bypass valves for 1 min.
4 @ TCVs.
What is the Generator Load Reject?
The load rejection circuitry monitors intermediate pressure (high pressure turbine exhaust pressure as a measure of the turbine energy) and generator stator amperage (as a measure of the energy being produced by the generator). PLU action on valves occurs when the generator current is decreasing at a rate of 1500%/sec. Below 40% of rated intermediate pressure, the PLU circuit cannot actuate.
What are the power supplies for the EHC Logic System?
Logic power in 10C363 is auctioneered between 1AD483 and 10Y107.
1AD483 - Primary logic power and 10C651D HMI
10Y107 - Backup power supply and 10C650E HMI
What happens when a load rejection signal is received?
- The load signal is immediately set to minimum.
- The control valve and intercept valve fast acting solenoids are actuated
- A direct turbine trip is generated.
How does pressure affect RPV level?
Pressure rises, RPV swells.
Pressure lowers, RPV shrinks.
How does RPV pressure affect power?
Pressure rises=> Less boiling due to an increase in saturation temp=> Void content goes down=> More moderation=> Prx goes up.
Pressure lowers=> More violent boiling due to a lower saturation temp=> Void content goes up=> Less moderation=> Prx goes down.
Describe the Turbine Speed Control (S1) coincidence.
2/3 coincidence.
When 1 is lost, alarms and loss of backup, then becomes 1/2 coincidence.
When 2 are lost, the turbine is tripped.
Describe the Turbine Pressure Control (P1) coincidence.
2/3 coincidence.
When 1 is lost, alarms and loss of backup, then becomes 1/2 coincidence.
When 2 are lost, loss of BPV’s and TCV’s a closed.
Describe the operation of speed control during an overspeed condition.
100% Normal speed.
V
105% TCV’s are shut.
V
107% CIV’s are shut.
V
108% Overspeed turbine trip.
V
110% Backup overspeed trip.
Control valves will close 20% for every 1% overspeed (100-105%). CIV’s will close 50% for every 1% (105-107%).
What occurs at 530 psig EHC oil pressure? is there a time when it is bypassed?
RX Scram(1 out of two taken twice)
Bypassed <18%
TCV Control pac disk dump valves
Describe the relationship between Rx and throttle pressures.
Throttle pressure is linear and Rx pressure is not. 30 pounds for 0-100% stm flow.
3.33% flow/psi error.
What is the first scram signal that occurs upon a turbine trip from?
the first scram signal to RPS will be from TSV closure (even when from 1100#) when above 18%
When below 18% it will be the high pressure scram
How does the Turbine Load Reject(Power to Load Unbalance) initiate a trip?
The control valve and intercept valve fast acting solenoids which remove ETS pressure from the TCVs initiating a turbine trip, in addition to load being immediately set to minimum.
What is the purpose of a Turbine load reject turbine trip?
This is necessary to prevent excessive turbine overspeed during the load reject
if the suction strainer for the EHC pump becomes clogged what will happen?
There is an internal port which will allow oil flow to the pump
What is the EHC oil discharge filter alarm setpoint?
100psid
What are the EHC Coolers cooled by?
TACS
What position do the TACS control valves fail to on a loss of air?
open
How many EHC accumulators are there and what are they used for?
- 6 on the skid - system surge volume
- 3 at the bypass valves (Provide 1 minute of operation to minimize pressure spike on loss of EHC.)
- 4 Fast Acting solenoid Control Valve accumulators - for control valve surge volume
What is the cross pressurization needle valve?
it is a valve in the Duplex 2/3 Trip Device that is - opened to pressurize an out of service manifold from the in-service manifold.
What is the sequence that steam is secured to the turbine as it overspeeds?
From 100% to 105% speed - The Turbine Control Valves will go from full open to full shut linearly.
From 105% to 107% speed - The Intercept Valves will go from full open to full shut linearly
IE neither use fast acting solenoids
Does turbine throttle pressure increase the same rate as reactor pressure?
No, throttle pressure is linear and reactor pressure is exponential
Can you explain pressure changes using the EHC logic?
yes
If you lower pressure set, what occurs?
control valves close -> RX pressure goes up, power goes up, and level goes down -> Bypass valves open to reduce pressure in the RX
How should you maintain your pressure setpoint when operating using the cooldown controller?
Maintain the pressure setpoint no more than 50# above throttle pressure
Which EHC oil is ported to the servo and to the hydraulic cylinder for valve operation?
FAS
Upon receipt of a turbine trip signal what happens to the BPVs?
simultaneous opening of all nine BPVs will occur within 0.15 seconds
