ML082590076

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Post Exam Question RO-40, NRC Exam, Comments, and Reference Documents
ML082590076
Person / Time
Site: Calvert Cliffs  Constellation icon.png
Issue date: 07/31/2008
From:
Calvert Cliffs
To: David Silk
Operations Branch I
Hansell S
Shared Package
ML073040307 List:
References
Download: ML082590076 (24)
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Question #40 Q50342Points: 1.00 A SIAS has occurred on Unit 1. Which of the following is a correct statement for CAC operation?

A. The CACs can be started in Fast Speed at 1C09 AND at the load contactor panel.

B. The CACs can be shifted to Fast Speed at the load contactor panel ONLY C. The CACs can be stopped from the load contactor panel ONLY D. The CAC's can be stopped at 1C09 and at the load contactor panel.

Answer: B Answer Explanation: The CACs can be shifted to Fast Speed at the load contactor panel ONLY.

A is incorrect, with a SIAS present CACs can not be started in fast speed from the CR per LD 76 sheet 11 B is correct since CACs can be shifted to Fast Speed at the load contactor panel ONLY C is incorrect, SIAS signal seals in per LD 76 sheet 11 D is incorrect SIAS signal seals in per LD 76 Sheet 11 All of the answers require the candidate to be familiar with the logic sheets and/or control drawings for the CACS. If a candidate does not know the logic he could have the misconception that the CACs can be shifted to fast or stopped with a SIAS present since the H/S at 1C09 have a pull to lock feature to start them in slow. He could confuse this with the ability to pull to lock and stop the CACs. Some pumps ( CCW, SW, SRW) can be pulled to lock and will not start on SIAS.

This is not true for the CACs. CACs are manually started in fast speed from 1C09 when containment environment is degraded.

Question #40

  • The following is the justification for changing the examination answer key to include selection C as a correct response in addition to selection B.
  • Question #40 states the following: A SIAS has occurred on Unit 1. Which of the following is a correct statement for Containment Air Cooler (CAC) operation?
  • Selection C states the following: The CACs can be stopped from the load contactor panel ONLY.
  • During the post examination analysis it was discovered that selection C is also a correct response. During a SIAS actuation the CACs will stop then restart in low speed. If the CAC local remote handswitch is positioned to the local position and the CAC local control handswitch is selected to stop then the CAC wil stop regardless of the SIAS actuation signal.

Question #40

  • Justification Continued

- If a SIAS does occur the CAC can be secured if its respective local/remote handswitch, CS-L/R, is positioned to local and its local control handswitch, CS-L, is placed in stop and spring return to normal.

- Based upon the control circuits contact configuration in this switch alignment the CAC can be stopped, run in slow speed, or run in high speed, by use of the local handswitch. A SIAS signal present does not affect local operation.

- The following Slides highlights the control circuit contact configuration with this switch alignment.

Question #40 The next slide will display the associated Control Switches and contact Schemes for;

- the CAC local/remote selector switch (CS-L/R)

- the Local handswitch (CS-L)

- the Remote Handswitch (CS-R) at 1C09 Items to note: the Local and Remote Handswitches are both Spring return to Normal with a Pull to Low Position. Which means the handswitch will not stay in the Stop or High speed position but will stay in the slow speed, Pull to Low, position.

Question # 40 Drawing 61076SH0011D For more clarification on the CS-L/R lets explain the terminal Number System. A Contact Labeled as CS-L/R with terminal points 56 57 Means that this contact is in the 5th deck of the Handswitch and follow The scheme for contacts 6 and 7, which is OPEN in Remote and Closed in Local

Question #40 Scenario #1, Normal Switch Alignment and a SIAS Signal is Received.

  • With the CS-L and CS-R switches in NORM (Normal Position)
  • The CS-L/R Switch in Remote (Normal Position)
  • A SIAS signal present
  • The fan will run in slow speed.
  • Follow along with the flow path traced in red on the next slide

- The SIAS A-8 (B8-10 &B8-11) contact closes providing a path to energize the low speed start relay (42/L)

- which closes contact (42/L 5-6) to seal in(keep energized) the low speed start relay (42/L),

- and also closes the (42/L 3-4) contacts

- which energizes the slow speed relay (S)

- which closes the (S) contacts which starts the fan in slow speed.

Question #40 The trace with the red lines display the control circuit's contact configuration with the local / remote switch in Remote (normal) and a SIAS signal Present The Fan is running in Slow Seal in contact

Question #40 With the local and remote controls switches in NORM (Normal Position)

The Local/Remote Switch in Remote (Normal Position)

A SIAS signal present The fan is running in slow speed.

Follow along with the flow path traced in Blue on the next slide If we Take the Remote control switch CS-R at 1C09 to High;

- The CS-R (1-1C) contact closes,

- however, the SIAS A-8 (B8-8 &B8-9) contact is open preventing a path to energize the high speed start relay (42/H)

The current path to the low speed relay (42/L) is not interrupted due to CS-R (2-2C) being closed in both NORM and HIGH, and the CAC will still be running in Slow.

Question #40 With a SIAS Signal in, will operation of the Remote Handswitch affect Operation of the CAC?

This SIAS contact is open with SIAS signal present 42/H never gets energized.

So the Fast Speed windings Remain deenergized.

Question #40 With the local and remote controls switches in NORM (Normal Position)

The Local/Remote Switch in Remote (Normal Position)

A SIAS signal present The fan is running in slow speed.

If we take the CS-R at 1C09 to Stop Follow along with the flow path traced in red on the next slide; All of the CS-R contacts Open which will de-energize the Relays, which will cause the Load Contacts to Open which will Stop the CAC.

However, the CS-R Spring returns to Normal which will re-close the CS-R (2-2C) contact, which will cause the CAC to start in slow speed as described in Slide 3

Question #40 With a SIAS Signal in, will operation of the Remote Handswitch affect Operation of the CAC?

Question #40

  • The circled contacts shown in the next slide are all contacts associated with the Local/Remote Switch.
  • The solid light blue circles/lines indicate the CS-L/R contacts which change states when CS-L/R is in Local. This will remove the SIAS contacts from the circuit and cause the CAC to stop.

Question #40 The CS-L/R contacts are identified by the BLUE lines and circles when the Local remote switch is taken to Local.

Question #40

  • With the CS-L AND CS-R switches in NORM
  • The CS-L/R Switch in Local
  • A SIAS signal present
  • To Start the fan in Slow speed at the local panel, follow along with the flow path traced in red on the next slide;

- We take CS-L to pull-to-low position

- which, via the CS-L (5-6) contacts, will energize the low speed start relay (42/L)

- which closes the (42/L 3-4) contacts

- which energizes the slow speed relay (S)

- which closes the (S) contacts which starts the fan in slow speed.

Question #40 This slide shows the Slow speed Local flow path

Question #40 With the CS-L and CS-R switches in NORM (Normal Position)

The Local/Remote Switch in Local A SIAS signal present To Start the fan in Fast speed at the local panel Follow along with the flow path traced in red on the next slide We take CS-L to high position which will close the CS-L (1-2) contacts Due to the CS-L/R being in Local the CS-L/R 62-63 and 66-67 contacts are closed (these are the Contacts that bypass the SIAS Contact in the Fast speed circuit)

This will energize the high speed start relay (42/H) which closes contact (42/H 5-6) to seal in the Fast speed start relay (42/H) and also closes the (42/H 3-4) contacts which energizes the Fast speed relays (F1 & F2) which closes the (F1 & F2) contacts which starts the fan in Fast speed.

The handswitch spring returns to normal which will open the CS-L (1-2) contacts, however a flow path is still available due to the Seal in contact (42/H 5-6).

Question #40 This slide shows the Fast speed Local flow path

Question #40

  • With the local and remote controls switches in NORM (Normal Position)
  • The Local/Remote Switch in Local
  • A SIAS signal present
  • To Stop the fan at the local panel
  • Follow along with the flow path traced in red on the next slide
  • We take CS-L to Stop
  • All CS-L contacts OPEN and interrupts current flow to the Start relays which opens all Load contacts which stops the CAC

Question #40 This slide shows the Stop Local flow path

Question #40 The trace with the red lines display the control circuit's contact configuration with the local/remote switch in local and the local control switch in stop/normal.

In this control circuit alignment power is not supplied to the SIAS A8 contact if it is shut.

Question #40

  • Question #40 answer explanation states that selection C is incorrect due to the SIAS signal sealing in and preventing securing the CACs from its load contactor panel using the Containment Cooling Fan Logic Diagram (60617 SH0011).
  • An examination of the CAC logic diagram shows that SIAS does not seal itself in preventing securing the CAC if the remote/local handswitch is in the remote position.
  • If the remote/local selector switch is in local and the local control handswitch is selected to stop then its respective CAC will stop.

Question #40 60617SH0011

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