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2013-10-16 11:14:36

Notes from the M8107L-030 RWCU lesson plan at MNGP
Show Answers:

  1. What are the two design reasons we use a filtering and ion exchange system to maintain reactor water purity?
    - To minimize changes in the heat transfer characteristics by reducing deposition of impurities on fuel surfaces

     - To reduce beta and gamma radiation by removing corrosion products and impurities
  2. What are the three lineups of the RWCU system?
    1. Normal Mode: Water is sent through RHX, then NRHX, then Demins, then RHX.

    2. Heat Reject Mode: Water bypasses RHX, first passes through NRHX, then Demins, then RHX.

    3. Bypass Mode: Water bypasses RHX and NRHX, first passes through Demins, then RHX.
  3. What is the maximum RWCU Filter Demin water temperature, and why?

    Temperature is limited to 140F to prevent resin breakdown
  4. What is the RWCU Demin Hi Temp alarm setpoint? What automatic actions occur?

    Annunciator on C-04 comes in.
  5. What is the RWCU Demin Hi-Hi Temp alarm setpoint? What automatic actions occur?

    • RWCU flow is stopped by closure of:
    • MO-2399
    • MO-2404
    • MO-2405
  6. What automatic actions occur when MO-2399 goes full closed?
    Both RWCU pumps trip.
  7. Why does initiation of SBLC remove RWCU from service?
    We don't want the boron removed from the water.
  8. What causes a RWCU pump to trip?
    • MO-2399 full closed with dump flow <40gpm
    • MO-2397 not full open
    • MO-2398 not full open
  9. What is the full flowpath of RWCU when in Normal Mode?
    • From B Recirc Loop suction
    • Through RHX (tube side)
    • Through NRHX (tube side)
    • Through RWCU pumps
    • Through A and B Filter Demins
    • Through Filter Demin control valves
    • Through RHX (shell side)
    • Through MO-2399 outlet isolation
    • Returns via RCIC and HPCI injection lines
  10. In relation to the Normal Mode flowpath, how is the Heat Reject Mode different?
    Heat Reject bypasses the first pass through the RHXs via RC-102.

    This removes heat from the system through RBCCW.
  11. In relation to the Normal Mode flowpath, how is the Bypass Mode different?
    Bypass mode bypasses both the first pass through the RHXs as well as the NRHXs. Water flows directly to the suction of the RWCU pumps.

    This is only recommended when Reactor water has cooled down such as part of vessel draindown.
  12. What type of valve is CV-2403, and what is its purpose?
    • Two inch air operated control valve.
    • RWCU Dump Flow Control Valve.

    During startup or other special cases, CV-2403 returns water from RWCU to either the Main Condenser (MO-2404) or to Radwaste (MO-2405).
  13. How does CV-2403 fail on a loss of air?
    CV-2403, RWCU Dump Flow Control valve, fails CLOSED on a loss of air.
  14. What setpoints will cause CV-2403 (RWCU Dump Flow) to close?
    • High downstream pressure of 140 psig.
    • Low upstream pressure of 5 psig.
    • Loss of air.
  15. What are all the Group III isolation setpoints?
    • High drywell pressure of 1.84 psig
    • Low-Low RPV level of -47 inches
    • RWCU high area temp of 170F
    • RWCU system high flow of 462 gpm +10 seconds
    • RWCU system negative dP of -200 gpm + 10 seconds
  16. What valves close on a Group III isolation signal?
    • MO-2397
    • MO-2398
    • MO-2399 (which will cause pumps to trip)
    • CV-2790
    • CV-2791
  17. Which RWCU valves are PCIVs per TS
    • MO-2397 (inboard)
    • MO-2398 (outboard)
  18. What are the potential repercussions of having both MO-2404 (Dump to Main Condenser) and MO-2405 (Dump to Radwaste) open at the same time?
    A potential loss of vacuum could occur.
  19. A loss of RBCCW occurs. What is the likely effect, if any, on RWCU?
    Due to loss of RBCCW, the RWCU Filter Demin temperature will rise. At 140F: MO-2399 closes, MO-2404 gets a close signal, and MO-2405 gets a close signal.

    As a result of the valve closures, both RWCU pumps will trip.
  20. What are the failure positions of the following valves on a loss of air?
    F/D holding pump discharge
    F/D outlet valves
    • F/D holding pump discharges fail OPEN
    • F/D outlet valves fail CLOSED
    • CV-2403 fails CLOSED
  21. What are the power supplies for the following valves?
    • MO-2397 = MCC-133
    • MO-2398 = D-313
    • MO-2399 = MCC-143
    • CV-2790 = Y-70
    • CV-2791 = Y-20
  22. What is the expected RWCU system response on a loss of Y-10?
    MO-2399, MO-2404, and MO-2405 will close due to loss of temperature monitoring.

    This will result in a trip of the RWCU pumps.
  23. What is the expected RWCU system response on a loss of Y-70?
    MO-2397 closes due to loss of valve position.

    This will result in a trip of the RWCU pumps.
  24. What is the expected RWCU system response on a loss of Y-80?
    MO-2398 and MO-2399 close due to loss of valve position.

    This will result in a trip of the RWCU pumps.
  25. If MO-2399 is closed, what must be true to not trip the RWCU pumps?
    Flow needs to be >40 gpm with MO-2399 closed or the RWCU pumps will trip.

    This is achieved with dump flow.
  26. True or False:

    RWCU flow, inlet temperature, outlet temperature, and dump flow are inputs to calculated thermal power.
    True. Changes to these parameters will affect calculated thermal power.
  27. Why is RWCU dump flow limited to 79 gpm?
    During maximum blowdown, if all flow is routed to the Main Condenser, no colling water is available to the RHXs.

    To protect the NRHXs, flow is limited to 79 gpm.
  28. Operation of RWCU with MO-2400 open results in:

    A. Higher than indicated thermal power
    B. No effect on thermal power
    C. Lower than indicated thermal power
    A. Higher than indicated thermal power

    MO-2400 open bypasses the F/D flow instruments. As a result, thermal power could be as high as 2 MWth higher than indicated.
    (this multiple choice question has been scrambled)
  29. What are the power supplies to the RWCU pumps?
    • 11 RWCU = MCC-132
    • 12 RWCU = MCC-122
  30. What interface with Radiation Protection must occur prior to backwashing the Filter Demins (F/Ds)?
    RP Coordinator must be notified to lock and post the 985' Reactor Radwaste Pump and Tank Room as a Locked High Radiation Area prior to backwashing.
  31. If both MO-2397 and MO-2398 are closed at the same time during normal plant operation, what must be verified? Why?
    Penetration X-14 must be verified as remaining above 335F or the volume maintained less than a water solid.

    This will avoid potential thermal expansion and overpressurization.
  32. Pressure downstream of CV-2403 spiked to 145 psig and CV-2403 closed. Pressure lowered and is now 128 psig. What is the expected condition of CV-2403? Why?

    CV-2403 automatically reopens when pressure is restored to normal.
  33. Why does a 10 second time delay exist for a Group III isolation signal on flow?
    To prevent accidental isolation of the system during system changes which may result in flow perterbations.
  34. What is the temperature limit at the inlet of the RWCU pumps during normal plant operation?
  35. What are the indications of resin breakthrough?
    • High conductivity
    • Low pH
    • Rise in Sulfates
    • Slight reduction in power
    • Change in filter dP (lower for affected filter, higher for downstream filter)
  36. What RWCU valves are powered from MCC-133?
  37. What RWCU valves are powered from MCC-132?
    • MO-2400
    • MO-2401
    • MO-2404
    • MO-2405
  38. What RWCU valves are powered from D313?
  39. What RWCU valves are powered from MCC-143?
  40. If BOTH MO-2397 and MO-2398 are inoperable, what is the required action and completion time?
    Isolate the affected flowpath by use of at least one closed and de-activated automatic valve, closed manual valve, or blind flange.

    1 hour
  41. If EITHER MO-2397 or MO-2398 are inoperable due to an electrical problem, what is the required action and completion time?
    Isolate the affected flowpath.

    4 hours
  42. What modes is LCO (PCIVs) applicable?
    Modes 1, 2, and 3
  43. Because the wiring for MO-2401, CV-2403, MO-2404, and MO-2405 exists in common fire areas, what precaution do we take with MO-2401?
    When RPV temperature is >212F, breaker B3201 (for MO-2401) SHALL be open and MO-2401 SHALL be closed unless Appendix R verifications and fire watch requirements are met.
  44. Given that dump flow is 45 gpm, what would the expected system response be if MO-2399 is taken to full close?
    Dump flow would rise. The RWCU pump would NOT trip since dump flow is >40 gpm.