RPV Instrumentation

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heidin
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140706
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RPV Instrumentation
Updated:
2012-03-15 10:43:10
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RPV Instrumentation ILC
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  1. Unit One is at rated power when a scram signal is received.

    Reactor water level drops and RWCU isolates.

    Which one of the following level indicators, if any, was indicating on scale and available for use when RWCU isolated?


    A. Fuel Zone (N036/N037) instruments only
    B. Wide range (N026A/B) instruments only
    C. Both Fuel Zone (N036/N037) and Wide Range (N026A/B) instruments
    D. Neither Fuel Zone (N036/N037) nor Wide Range (N026A/B) instruments were available.
    C. Both Fuel Zone (N036/N037) and Wide Range (N026A/B) instruments


    RWCU isolates at LL2 (105 inches) with the Wide Range (N026A &B) indications from 0-210 inches and the Fuel Zone (N036 & 37) indicators onscale due to the Recirc pumps tripping at LL2.
  2. Unit One has shutdown for an outage and is in the process of transitioning from Cold Shutdown to Refueling. Actions are in progress to realign level indicating loops B21-L1-R605NB from transmitters B21·LT·N027NB to B21-LT-7468NB in preparation for cavity flood up. Why are level transmitters N027A(B) taken out of service for refueling operation?

    A. N027NB variable leg piping is to be disconnected.
    B. N027NB are calibrated for post accident conditions.
    C. N027NB reference leg piping is to be disconnected.
    D. N027NB are calibrated for normal operating conditions.
    C. N027NB reference leg piping is to be disconnected.

    N027NB are calibrated for shutdown conditions (not normal operating or post accident). During vessel disassembly, the normal reference leg piping for N027NB is disconnected in preparation for removing the RPV head since N027NB share a condensing pot from the RPV head. Disconnecting and removing a portion of this reference leg piping would require recalibration of the N027NB instrument loops to account for this condition to provide accurate level indication. To eliminate the need for this instrument loop recalibration during vessel disassembly and reassembly, alternate level transmitters are installed.
  3. Following a steam leak in the Unit 2 Secondary Containment, a manual reactor Scram has been inserted. Plant conditions:

    RPV pressure 1000 psig
    Drywell ref leg area temp 197F
    Rx Bldg 50’ temp 145F
    Recirculation Pumps Running
    RPV water level +150” (N036/N037)
    RPV water level +170” (N026A/B)
    RPV water level +155” (N004A/B/C)
    RPV water level +160” (N027A/B)

    RPV water level may be determined using N004A/B/C:

    A. Only
    B. and N026A/B only.
    C. and N027A/B only.
    D. and NO36/N037 only.
    A. Only



    • Rx Bldg 50’ temp 145F disqualifies the N026A/B (>140F)
    • Recirculation Pumps Running disqualifies the N036/37 (pegged upscale)
    • Caution 1 graph 1000#/160” disqualifies the N027A/B (UNSAFE area)
  4. Unit Two was operating at 100% power when a steam line break caused drywell pressure to rise.

    Which one of the following identifies the normal temperature relationship between compensated and uncompensated level instrument legs and also identifies the level instruments that will first be affected as drywell temperature rises due to the steam leak?


    A. The compensated level instrument legs are at a higher temperature than the uncompensated legs, the compensated level instrument legs will boil first.
    B. The uncompensated level instrument legs are at a higher temperature than the compensated legs, the uncompensated level instrument legs will boil first.
    C. Both instrument legs are at the same temperature. The compensated level instrument legs will boil first.
    D. Both instrument legs are at the same temperature. The uncompensated level instrument legs will boil first.
    A. The compensated level instrument legs are at a higher temperature than the uncompensated legs, the compensated level instrument legs will boil first.




    If an accident should occur that causes drywell temperature to increase and reactor pressure to decrease, boiling can take place in the level instrument legs. The question is; which arrangement, compensated or uncompensated, will boiling most likely occur in first? Since the compensated level instrument legs are at a higher temperature than the uncompensated legs, they will reach a higher temperature first. It should be pointed out that the legs do not heat up to drywell temperature immediately, as there is a thermal time constant that can be 4 to 6 minutes. A time constant is the amount of time required for a signal or a parameter to reach 63.21 % of the final value. After 5 time constants, the signal is > 99% of the final value. A 4 to 6 minute time constant means that it can take from 20 to 30 minutes for the reference legs to heat up to drywell temperature.
  5. Unit One shutdown is in progress with the following plant conditions:

    RWCU is in service.
    Recirc Pump B is running.
    SDC A Loop has been lost.
    Feed and bleed has been established.
    Reactor Coolant Temperature is 190° F and lowering slowly.

    Given this condition in progress, which one of the following identifies the PREFERRED indication to use to determine vessel metal temperature response in accordance with 1PT-01.7, Heatup/Cooldown Monitoring, including the reason?


    A. Bottom head metal temperature;
    metal temperature response leads the coolant temperature response during a cooldown.

    B. Bottom head metal temperature;
    coolant temperature response leads the metal temperature response during a cooldown.

    C. Bottom drain coolant temperature;
    metal temperature response leads the coolant temperature response during a cooldown.

    D. Bottom drain coolant temperature;
    coolant temperature response leads the metal temperature response during a cooldown.
    D. Bottom drain coolant temperature; coolant temperature response leads the metal temperature response during a cooldown.


    During cooldown, Bottom Head coolant temperature is the preferred source due to coolant temperature response leading vessel metal temperature response. If RWCU flow exists, then use vessel bottom drain coolant temperature. If RWCU does not exist and recirc pumps are running, then use recirc pump suction temperature. If RWCU and Recirc are not running, then use bottom head metal temperature. Steam dome temperature would be used to determine coolant temperature if psat >212° F. As stated in the procedure the coolant temperature will lead the metal temperatures.
  6. A steam line break in primary containment has caused a reactor scram. Twelve control rods are not full in. Reactor water level was 150 inches when erratic level indication was observed on all available level indications during depressurization.

    Which one of the following predicts the response of the available level indication as the reactor depressurizes and also identifies the required procedures when reactor water level cannot be determined?

    Level indication will eventually fail ______________.

    The SCO is required to _______________.


    A. downscale;
    completely exit LPC flowchart and enter RxFP flowchart for power, pressure, and level control.


    B. downscale;
    execute only the power leg of the LPC flowchart and the RxFP flowchart concurrently.


    C. upscale;
    completely exit LPC flowchart and enter RxFP flowchart for power, pressure, and level control.


    D. upscale;
    execute only the power leg of the LPC flowchart and the RxFP flowchart concurrently.
    D. upscale; execute only the power leg of the LPC flowchart and the RxFP flowchart concurrently.


    Instrument leg flashing causes pressure transients within the lines which can cause indications to fluctuate widely from high to low. If reactor water level indication cannot be determined, the Reactor Flood Procedure is entered. The power leg of LPC is executed with RxFP, level and pressure legs of LPC are exited.
  7. The reactor vessel indications on the P601 and P603 are a measure of:

    A. The water level in the downcomer region using the lower tap as instrument reference 0.
    B. The water level within the shroud including level in the steam separator area. C. The water in the downcomer region for all of the instruments except the N036 and N037, Fuel Zone Instruments, which measure water level in the Shroud area.
    D. The water level in the downcomer region for all of the instrument except the N026A and N026B, Wide Range Instruments, which measure water level in the Shroud area.
    C. The water in the downcomer region for all of the instruments except the N036 and N037, Fuel Zone Instruments, which measure water level in the Shroud area.
  8. Which range of RPV level indication on the RTGB is most affected by a high energy line break in the Reactor Building?


    A. Wide Range (N026A/B)
    B. Narrow Range (N004A/B/C)
    C. Fuel Zone Range (N036/N037)
    D. Shutdown Range (N027A/B)
    A. Wide Range (N026A/B)
  9. During a reactor start up, RPV pressure was being increased from 250 psig to rated when a small break LOCA occurred. Groups 2, 6, & 8 isolation signals were received. The Scram hard card actions were completed with no further operator actions taken.

    Plant conditions are as follows:

    RPV Level 180 inches (steady)
    RPV pressure 50 psig
    Drywell temperature 240°F (average)
    Drywell temperature 310°F (reference leg area)

    The RTGB level indicators that should be used are the:

    A. N004A/B/C, N026A/B, and N027A/B ONLY
    B. N004A/B/C and N026A/B ONLY
    C. N0 N004A/B/C, N026A/B, and N027A/B ONLY
    D. N026A/B ONLY
    B. N004A/B/C and N026A/B ONLY
  10. During a Unit Two (2) reactor start up, RPV pressure is being increased from 250 psig to rated when a small break LOCA occurs in the drywell. Plant conditions are as follows and the STA advises the crew that there are no indications of reference leg flashing.

    Plant conditions are as follows:

    RPV Level 180 inches (steady)
    RPV pressure 50 psig
    Drywell temperature 240°F (average)
    Drywell temperature 310°F (reference leg area)

    The RTGB level indicators that should be used are the:

    A. N004A/B/C, N026A/B, and N027A/B ONLY
    B. N004A/B/C and N026A/B ONLY
    C. N0 N004A/B/C, N026A/B, and N027A/B ONLY
    D. N026A/B ONLY
    B. N004A/B/C and N026A/B ONLY
  11. A Unit Two (2) reactor scram occurred. Current plant conditions are:

    Reactor water level +230”, rising on the N027A and B
    Reactor pressure 350 psig, steady
    Drywell ref leg temp 195°F

    Based on these conditions, what is the lowest reactor water level that requires closing the MSIVs?


    A. 240”.
    B. 245”.
    C. 250”.
    D. 255”.
    B. 245”.

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