ECC directed unloading Flashcards
State the required entry and exit conditions associated with ZZ25 ECC directed unloading.
Entered when ECC requests a reduction to generation output by < 600MW to restore grid stability.
Exited when:
the steps are performed or a reactor trip occurs.
Describe the major steps necessary to reduce turbine load.
U1 coordinates the load reductions.
<200 MW performed by App A and the SBCS
- Boron eq.
- CEDMCS NOT in AS
- SBCS local setpoint adj to >20psig above actual Psg.
- SBCS to Local Auto, no auto demands present and give both 1001 and 1004 a manual permissive.
- Using load limit pot, reduce turbine load to transfer to SBCS.
> 200MW from a single unit with Rxpwr > 75% may be performed by manual RPCB.
App E.
- Initiate A LOFP RPCB
- check MT load is < 65%
- Check CEAs < 6.6 deviated
- SG lvls 45-60% NR
- Tave - Tref +- 3 F and SBCS controlling MS pressure at setpoint.
- Reduce Load limit pot to gain positive control of MT control valves.
- When CEAs only required for Xe and MT load limit light is lit, then place CEDMCS in MS.
- Start boron eq.
State the time limit for reducing turbine load.
15 minutes.
When will individual units NOT reduce generator load when directed by the ECC?
Currently in an outage(no shit)
has extenuating circumstances taht would prevent a reduction of power.
State the site and individual unit load reductions that are allowed.
600MWe is the maximum load reduction for the site.
200 MWe is the maximum load reduction per unit using APP A. Load reductions greater than that will use App E. RPCB.
State the expected alarm associated with a restoration of power in APP B.
APP B restoring turbine load
NOTE: a COLSS POL alarm is expected bc TFSP power was calibrated up to JSCALOR while TLI and rx power were out of balance.
State the major steps required to restore Turbine Load.
If using the load limit pot, then:
- Ensure pot is controlling load
- raise load set motor sufficiently out of the way, it will follow the pot down ~2-3% and will have to be raised up periodically to get it out of the way.
- Slowly raise load with the potentiometer.
If load set control will be used:
- Slowly raise the load limit pot out of the way. From the condition of the turbine on the pot, the load limit pot will have to be raised to give control to the load set motor.
- Select desired loading rate
- slowly raise the load set to the desired value using the increase pushbutton.
When SBCS valves are fully closed, then:
- Ensure the individual SBCS valve controllers manual setpoint is 0.
- Ensure auto demand for SBCV is 0
- Remove manual permissive on affected SBCVs.
- Ensure individual SBCV controllers in Auto.
- Place SBCS master in Remote Auto
- Restore local auto setpoint to normal(CRS)
- Go to Power operations GOP
State when it is required to reduce Rx power to match turbine power after an ECC Directed load reduction.
If the ECC estimates that the grid problems can NOT be corrected within 2 hrs and a unit lowered load using App A. Then lower RX power with App C.
IF a RPCB was used and the grid problems are not able to be restored within 2 hrs, then go to Power operations GOP for operation at reduced load.
State the consequences of local auto with manual permissives on two valves for the following scenarios:
Rx trip while set up to reduce load(local auto setpoint at 1070psia with manual permissive)
Turbine trip at power with L - A setpoint at 1070psia with manual permisives)
On a rx trip in this condition, you would get SBCS response to maintain 1070psia. THis corresponds to ~ 554F RCS temperature and result in overcooling the RCS, potentially emptying the Pzr and picking up SIAS, CIAS.
On a turbine trip at power in this condition, there is no quick open feature and the RCS pressure excursion from the load reject would result in a Ppzr HI trip at 2383#.
