ML20206Q822
| ML20206Q822 | |
| Person / Time | |
|---|---|
| Site: | Wolf Creek  |
| Issue date: | 04/16/1987 |
| From: | Withers B WOLF CREEK NUCLEAR OPERATING CORP. |
| To: | NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM) |
| References | |
| WM-87-0127, WM-87-127, NUDOCS 8704220043 | |
| Download: ML20206Q822 (5) | |
Text
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WOLF CREEK NUCLEAR OPERATING CORPORATION April 16, 1987 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D.C.
20555 Letter: WM 87-0127 Re:
Docket No. 50-482 Ref:
Letter WM 87-0100 dated 3/20/87 from BDWithers, WCNOC, to NRC Subj:
Response to NRC Questions Concerning AMSAC Gentlemen:
The enclosure to this letter provides responses to staff questions discussed on March 31, 1987 concerning the Anticipated Transient Without Scram (ATWS)
Mitigation System Actuation Circuitry (AMSAC) design described in the referenced letter.
A copy of this letter is being provided to Mr.
A.
E.
Nolan of EG&G Idaho, Inc.
If you have any questions concerning this topic, please contact me or Mr. O. L. Maynard of my staff.
Very truly yours, e
,x
=
Bart D. Withers President and Chief Executive Officer BDW:jad Enclosure cc:
P0' Conner (2)
JCummins itDMartin AENolan h
O P
P.O. Box 411/ Burington. KS 66839 / Phone: (316) 364-8831 g
4 Equal oecertun4y Emoleyer M C HC VET
Enclosure to WM 87-0127 Page 1 of 4 April 16,1987 Response to Questions Concerning ATUS Mitigating System Actuation Circuitry for Wolf Creek Generating Station Question 1 Will the AMSAC system have a variable timer in accordance with addendum 1 to WCAP 10858?
Response 1 The additional requirements for variable time delays discussed in Reference 1 are not applicable to the steam generator level logic option chosen by Union Electric (UE) and Wolf Creek Nuclear Operating Corporation (WCNOC).
The variable time delays are applicable to the low feedwater flow logic and the feedwater pump and valve status logic.
As stated in Reference 2, the AMSAC signal will be delayed approximately 25 seconds to permit the Reactor Protection System (RPS) to provide the first trip signal.
This statement was based upon information contained in WCAP-10858.
Section 11.0 on page 3-6 of WCAP 10858 requires AMSAC to trip the turbine within 30 seconds.
This 30 second response time is defined as the time interval following a step input in steam generator water level from 5%
above to 5% below the ?-ip setpoint until the turbine is tripped.
Section 12.2 discusses the use er an AMSAC signal delay to ensure that the RPS will provide the first trip signal.
Section 13.0 on page 3-8 requires the AMSAC signal adjustable delay to have a range of 0-60 seconds.
UE and WCNOC intend to meet the above requirements.
Twenty-five (25) seconds was chosen to allow a 5 second margin for sensor / electronics delay and still meet the 30 second requirement.
This setpoint will be adjustable to allow changes to be made in accordance with any future guidance from the Westinghouse Owners Group.
Question 2 Will isolation devices be qualified in accordance with Appendix A to the SER for WCAP-108587
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-Enclosure to WM 87-0127 Page 2 of 4 April 14 1987 Response 2 AMSAC requires isolation between Class IE and non-Class IE circuits on the 4
~ steam generator level inputs from the RPS and on the actuation outputs to-the Balance o f.
Plant-Engineered Safety: Features Actuation System (BOP-ESFAS).-
Isolated outputs on the instrument loop power supplies in the RPS isolate the steam generator level inputs to AMSAC.
Westinghouse qualified
-the power supplies as an isolation device in_WCAP-8892-A.. The. testing done meets the requirements of. Appendix A and has been reviewed and approved by NRC.
. The AMSAC outputs to BOP-ESFAS will be isolated using Struthers-Dunn 219 frame general purpose relays.
The Struthers-Dunn Qualification Test Report demonstrates that the 219 frame general purpose relay qualifies as an isolation device and meets the requirements of IEEE 279-1971 and RG 1.75.'
The Struthers-Dunn relays remained functional (relay coils did not short, ground-out or open-circuit) as demonstrated by the specified environmental i
and functional testing per IEEE 323 after aging.
Therefore, relay failure is not postulated to be a credible common mode failure during the 40 year
- qualified life of these relays.
These relays successfully passed dielectric strength functional testing.
Under this testing, a voltage potential of 2200 V ras (as determined per ANSI C37.90) was applied to the relays between the coil and contacts, the coil and case, and the contacts and case. There was no arc-over, flash-over or breakdown observed.
The potential applied during this testing-well exceeds the maximum credible fault potential present in the AMSAC cabinet.
The maximum credible fault is from the 125 VDC power supply to the AMSAC cabinet.
In addition to the electrical isolation provided by the coil to contact configuration of these relays, physical separation between the terminals for L
the Class IE side and the non-Class IE side provides at least 6 inches of air space or its equivalent in tracking distance by means of barriers.
The ' Struthers-Dunn Qualification Test Report meets the requirements of IEEE 323-1974 and IEEE 344-1975.
i The Class IE contacts will be powered from BOP-ESFAS Class IE circuits.
AMSAC provides BOP-ESFAS with a dry contact through the isolation relay.
Since this is an on/off device, there will be no electrical interference propogating.from the coil to the contacts which would affect the Class IE 4
BOP-ESFAS circuits.
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Encle;;urs to WM 87-0127-Page 3 of 4 April-1987 Question 3 Provide more detail relating to the AMSAC logic and IE/non-IE interfaces (Figure 1).
Response 3 Attachment 1 is a logic drawing depicting the Callaway and Wolf Creek AMSAC system.
Isolated inputs from the RPS enter the logic cabinet and are compared to the AMSAC steam generator water level setpoint.
These signals are processed through a 3 out of 4 logic gate and are delayed 25 seconds to permit RPS actuation prior to initiating any AMSAC function.
Turbine impulse pressure signals are input to block AMSAC below 405 power.
Three logic schemes are connected in a 2 out of 3 configuration to protect against any inadvertent actuation. also indicates the Class IE/non-Class IE interfaces.
Input isolation is provided by the RPS power supplies in the Westinghouse 7300 Process Protection System cabinets.
Output isolation is provided by Struthers-Dunn isolation relays.
Question 4 Will different power levels affect the steam generator level transmitters?
Response 4 The Callaway and Wolf Creek plants employ a constant water level control scheme.-
The control system maintains a 50% steam generator narrow range water level at any power level. In addition, the level transmitters used by AMSAC are different than those used to control steam generator level.
References:
1.
Letter OG-87-10 dated 2/26/87 from RANewton, WOG, to the NRC 2.
Letter ULNRC-1472 dated 3/19/87 from DFSchnell, UE, to the NRC
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