Power Operations 20-100% Flashcards
Why should you slowly place MSRs in service?
avoids excessive temp transients which minimizes Turbine vibrations.
What operator actions with MSRs helps maintain LP Turbine dTemperature < 50F?
- Operate MSRs in the same Mode to maintain LP Turbine ∆T’s < 50°F.
State several items that can affect the intensity of MT vibrations during operation.
- Lubricating oil temperature
- Low turbine loading
- High rates of power change
- High rates of condenser vacuum change or approaching 2” HgA
- ∆T across the condenser section
- MSR operation
- Steam drain operation
- Thermal transients (Equipment malfunctions that direct steam or drains to the condenser)
What steady state method of turbine control maintains plant stability?
What else does this minimize with respect to the TCVs.
- Steady state: turbine control on the load limiter. Maintains plant stability and minimize pressure surges on control valves.
What is the normal MT vibration threshold?
What is the MT trip criteria for high vibrations?
When should a reactor trip be performed with regard to high vibrations in the MT?
-
5 mils (normal Turbine vibration)
- Auto turbine trip at 12 mils unfiltered
-
Turbine trip criteria:
- Filtered journal vibration > 10 mils and rapidly ↑ towards 12 mils at rated speed
- Filtered vibration > 10 mils with a slow ↑ towards 12 mils after a 15 minute time span at rated speed
-
Reactor trip criteria (if during normal power reduction with a planned reactor trip):
- Sudden step ↑ of 2 mils
- Vibration ≥ 10 mils
What is the temperature limit for the following:
MT oil drain temp.
MT bearing metal temp.
LP turbine steam inlet temp change limit.
- ≤ 170°F: Limit for Turbine oil drains during continuous operation at the hottest bearing.
- ≤ 225°F: Normal turbine bearing metal temperature.
- < 125°F/hour: Normal LP turbine steam inlet temperature change limit. Short term changes limited to 250°F/hour.
What operations should be avoided to minimize MT damage with regards to vibrations?
- < 40% load with C shell ≥ 5 inches HgA (vibrations)
- < 40% load (410 MW) and C shell > 4” to < 5” HgA for 1 hour max (vibrations)
How can breaking vacuum above 1200rpm affect the turbine?
When is it allowed?
- Breaking vacuum > 1200 rpm (excessive loading on Last Stage Buckets)
- In emergencies only.
What is detrimental about maintaining vacuum without GS in service?
- Maintaining vacuum after gland seal steam lost can cause thermal shock to rotor by intake of cold air.
What can happen if excessive use of exhaust hood Sprays at low speeds and low loads is allowed?
erosion of last stage buckets
What minimum speed and load should be avoided with regards to the MT?
- Operating < 800 rpm (> 5 min). (Cause packing rub, high vibes not indicated, or bowed rotor)
- Minimize operation < 5% load (moisture erosion on last stage buckets)
What are teh exhaust hood temperature limits and what coudl happen if they are violated?
- ≤ 125°F: rapid load changes allowed
- 125 - 175°F: may operate continuously but change load slowly (0.5%/min) (avoids unnecessary thermal stress)
- 200-225°F: 15 minute max operations (turbine trips at 225°F)
State the following:
rate of turbine load reductions
normal power reductions
TG operation prior to start
continuous TG operations.
- ≤ 10%/min load reductions minimizes turbine thermal stresses.
- Limiting normal power reductions to 20%/hour (4 hour normal shutdown) will minimize turbine vibration.
- < 48 hours TG operation prior to turbine start may cause shaft bowing
- Avoid long periods of TG operations. Generator field grounds may occur from copper dust build-up. (galling of windings)
With regard to Condenser backpressure:
- State the C shell max backpressure
- C shell operations that minimizes MT vibrations
- Reactor trip setpoints
- C shell max backpressure is < 5.0” HgA.
- C shell > 2” HgA and ≤ 4” HgA minimizes Turbine vibration.
-
Trip reactor if load < 410 MW and > 4” HgA for > 1 hour
- Trip reactor if load < 410 MW and > 5” HgA
Why should the condenser vacuum be maintained as close as possible to table values?
> 40% pwr
- > 40% power: maintain average pressure as close to table values as possible (↑ turb efficiency / ↑ MWe)
- Maintain A shell pressure above the table values (↓ erosion of condenser internals from excess steam velocities)
What actions are taken to prevent exceeding 5” HgA?
- Reduce turbine load to prevent exceeding 5” HgA
State the ASI limits associated with LCO 3.2.5.
- LCO 3.2.5 ASI limits:
- COLSS Operable
- -0.18 ≤ ASΙ ≤ 0.17 (> 50%)
- -0.28 < ASI < 0.17 (> 20% and < 50%)
- COLSS out of service (CPC)
- ± 0.10 ASI (>20%)
- COLSS Operable
When should ASI dampening be performed?
- ASI dampening performed if ASI will exceed ESI by ± 0.1.
At what ASI threshold is a reactor trip performed?
-
Trip the reactor if exceeded or trending to ± 0.5 (CPC Hot Pin ASI Aux Trip).
- ASI input to CPC aux trip depends on power
- ≥ 51% (sum of the 3 NIs): uses actual power distribution (during power ascension)
- ≤ 45% (sum of the 3 NIs): uses a canned value (during power reduction)
Which of the following should be used during a downpower?
Colss asi or CPC asi?
- CPC and COLSS can calculate a large ASI difference due to design differences and calculation processes. CPCs generate an auxiliary trip prior to COLSS indicating a problem with ASI.
When is PZR boron equalization performed?
-
≥ 50 ppm RCS Boron conc. change: perform PZR boron equalization
- Maintain until ≤ 10 ppm difference (RCS vs PZR)
Who is notified if Rx power is < 85% for more than 10 days?
- Power < 85% for > 10 days: notify nuclear fuel groups for evaluation.
Who is notified if a power change is required or ASI dampening is performed and why?
When is the sample required?
- Chemistry notified of any power change or ASI dampening (sample for iodine spikes)
- LCO requires sample within 2-6 hours of a ≥ 15% / hour power change
What is required from section 6.1 prior to raising power > 20%?
- 20% mode change checklist complete (ZZ11)
- Maintain Power Ascension Rate Limits (App. A)
- Unit Ops Manager permission required if SBCS, PLCS, PPCS, or FWCS are NOT in Auto.
- Monitor AZTILT (LOC limit and CPC value < actual tilt)
- Place MSRs in-service
When are both HDPs placed in service?
- 20-25% plant power: place both HDTPs in-service
When are extr steam drains and turbine drains closed?
- 250 MWe: close extraction steam drains and turbine drains
What happens at 30, 50 and 90% on power ascension?
- 30%, 50%, 90%: chemistry hold points
When is the 3rd CDP started?
40%
When is the second MFP started?
40-60% reactor power
When is RPCB placed in service and when are subgroups selected?
- 70% reactor power: place RPCB in-service with NO subgroups selected
- 74% reactor power: select RPCB subgroups
When is SBCS placed in remote auto?
75%
Define Axial Offset Anomoly and what adverse effects it will cause core operations.
-
Axial Offset Anomaly (CIPS): CRUD builds up on the high power fuel pins. Lithium boron absorbed in the CRUD (plates out). Causes power shifts to bottom of core.
- – AOA: more flux in bottom of core (opposite of ASI)
- ↓ SDM and ↑ power peaking
State the following Generator limits for normal operations:
- Vterm
- Buck
- Boost
- ECC max voltage
- max H2 cold gas temp
- H2 min/max press
- limits associated with the capability curve.
- 22.8 – 25.2 kV (Generator Terminal Voltage band 24 kV ± 5%)
- - 310 MVARs (max Buck Limit to minimize low voltage conditions on the buses)
- + 560 MVAR (max Boost Limit)
- 535.5 kV: ECC max voltage limit
- ≤ 48°C (118.4°F): Max inlet H2 cold gas temp. Ensure adequate generator cooling.
- 30 psig: Min H2 pressure. Ensure adequate density of the gas for cooling the generator. (Max load 940 MW (~ 67%))
- 75 psig: Max H2 pressure.
- Capability curve: AB (field heating), BC (armature heating), CD (armature core end heating)
How can RG 4 be used to control ASI?
- Use RG 4 to control ASI if heavily top peaked
- ASI cannot be maintain with ± 0.05 of ESI and < 70% (< 55% if COLSS OOS)
- RG4 can be inserted beyond normal overlap
- Maintain RG 5 > 75”
- Maintain RG 4 ≥ 10” above RG 5 (if RG4 < RG5, an out of sequence CPC trip will occur)
- Track time that RG 4 is between ARO and transient RIL
What is the desired band for RTP and by what indication?
What is licensed power based on?
How should the crew adjust hourly power if 100% is exceeded?
- Desired control band for RTP is between 99.8% and 100% using hourly average calorimetric power (JSCALORH).
- License limit is the 12 hour average
- If hourly exceeds 100%, reduce to < 100% in the next hour. Monitor 10 minute average.
What minimizes MFW imbalances?
maintaining MFP biasing ≤ 100 rpm difference minimizes MFW imbalances
What is MFP bias adjustment based on?
Why is 100 psid at 100% maintained?
- Lower MFP speed (- bias) until MFP discharge pressure is 100 psig > SG pressure or – 500 rpm
- Maintain ~ 100 psid at 100% (sufficient FF to SGs, low enough to minimize ECCV oscillations, low enough to improve MWe output / efficiency)
What limit to rated power exists if using NKBDELTC for > 12 hrs?
- If controlling power with NKBDELTC for > 12 hours, reduce power to 96.6%
When is CEDMCS placed in AS?
- Placed in AS when > 40%
How is EOL coastdown performed, big picture?
- EOL Coast down (↓ turbine load as Tavg drops OR Tcold coastdown)
- CEDMCS Not in AS if performing Tcold coastdown
How should Tave-Tref be maintained when >90% power?
What does this accomplish?
- Maintain Tavg/Tref ± 3°F
- When > 90%, maintain Tavg as close to Tref as possible.
- Minimize potential for VOPT pre-trip alarms when Tavg is high or MSIS pre-trip alarm when Tavg is low.
What must be met to stop HDPs after taking the turbine off-line?
HDT level are stable and pumps are operating on mini-flow
Whose permission does it take to go above 20% if SBCS, PLCS< PPCS, FWCS are not in AUTO?
- Unit Ops Manager permission required if SBCS, PLCS, PPCS, or FWCS are NOT in Auto.
When is the UFM placed in service on power ascension?
- 93%: UFM placed in-service
Why must power ascension rates be strictly adhered to and when do they apply?
- Prevents fuel damage / voiding fuel warrenties. Applies > 20%.
- Initial start-up limits below 20% are covered by 72PA-9ZZ07, “Reload Power Ascension Test.”
Whose permission is requried for the following:
- Maneuvering plan predicts ASI will exceed LCO limit during power reduction.
- SBCS, PLCS, PPCS, or FWCS are NOT in Auto.
- Unit Ops Manager permission required if plan predicts ASI will exceed LCO limit during power reduction.
- Unit Ops Manager permission required if SBCS, PLCS, PPCS, or FWCS are NOT in Auto.
At what hotwell level should HDPs be stopped?
- 46-48” Hotwell level prior to stopping HDTPs
How are NAN-S01 and S02 powered if reactor power is to be reduced < 20%?
From offsite power via the SU XFMRs
Ensure not more than 1 Unit is powered from 1 SU XFMR.
Ensure other unit’s DG’s are not in parallel with off-site power.
What actions are taken at < 70% on shutdown?
- < 70%: remove RPCB from service (40OP-9SF04 - Auto Actuate OOS and Test/Reset PBs)
- < 70%: place HDT LICs in Local-Auto (7’ setpoint)
When <60% power, which MFP is removed from service first and why?
- < 60%: stop 1st MFP (preferably A MFP due to water intrusion issues)
What should be removed from service if the MT is being shutdown?
- Remove MSRs from service if generator is being shutdown
With regards to the SGBDs, what must be ensured at ~ 25%?
- < 25%: ensure SGBD is NOT aligned to the SGBD demins
How is the plant stabilized if 20-30% power is to be maintained with the MT tripped?
- Place one SBCV in Manual permissive (1001)
- Place SBCS in Local-Auto. Adjust SBCS master controller to open 1001
- ↓ turbine load to 50 MWe
- Place more SBCVs in manual as needed for load reduction
- Trip the turbine when ≤ 50 MWe
- Shutdown the generator (open disconnects)
- Reclose the generator PCBs within 2 hours
Why should only 2 charging pumps be running prior to tripping the reactor?
prevent lifting the letdown relief CHN-PSV-345.
Briefly describe the process to stop Condensate pumps per 40OP-9ZZ14.
- Throttle open SGBD HX condensate outlet valves to maximize flow (suction pressure) to MFPs (500 gpm max per path)
- Throttle open Cond Demin bypass (PDV-195) to maximize MFP suction pressure
- Close the Condensate pump discharge valve and stop the pump
Briefly describe the process of stopping the first MFP per 40OP-9FT01/02.
- Reduce speed on the MFP (use Bias or manual speed control) until discharge pressure is below the other MFP
- Close the MFP discharge MOV
- Trip the MFP
- Place on turning gear, re-open discharge MOV, adjust lube oil and seal pressures
