ML20214G886
| ML20214G886 | |
| Person / Time | |
|---|---|
| Site: | Beaver Valley |
| Issue date: | 05/04/1987 |
| From: | Carey J DUQUESNE LIGHT CO. |
| To: | Murley T NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I) |
| References | |
| 2NRC-7-105, 87-08, 87-8, NUDOCS 8705270206 | |
| Download: ML20214G886 (4) | |
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'Al6 2NRC-7-105 Beaver Valley No. 2 Unit Project Organization Telecopy (
) 1 Ext.160 S.E.G. Building P.O. Box 328 May 4, 1987 Shippingport, PA 15077 United States Nuclear Regulatory Commission Region I 631 Park Avenue King of Prussia, PA 19406 ATTENTION: Dr. Thomas E. Murley Administrator
SUBJECT:
Beaver Valley Power Station - Unit No. 2 Docket No. 50-412 CIB - Initiated Timers for Control Room Emergency Pressurization Fans Potential Significant Deficiency Report 87-08 Gentlemen:
This final report is in reference to potentially reportable Signifi-cant Deficiency 87-08 relating to "CIB-Initiated Timers for Control Room Emergency Pressurization Fans."
Pursuant to the requirements of 10CFR50.55(e), the attached final report substantiates that the initially reported condition has been evaluated as not report able.
No additional information or reports on this item are, therefore, anticipated.
DUQUESNE LIGHT COMPANY f/
By
/,'
~
J. Warey t.
Sr. Vice President DLC/ijr NRC/DLC/SDR/8708 Attachment AR/NAR l
cc: Mr. P. Tam, Project Manager (w/a)
Mr. J. M. Taylor, Director (3) (w/a)
Mr. J. Beall, Sr. Resident Inspector (w/a)
Mr. L. Prividy, NRC Resident Inspector (w/a)
INP0 Records Center (w/a)
NRC Document Control Desk (w/a) g5270206870504 S
ADOCK 05000412 PDR I
167 I
e ATTACHMENT 1.
Summary Timers initiated by Containment Isolation Phase B (CIB) signals which divert the Control Room Emergency pressurization system one hour after a CIB initiation, were powered from the respective fan control circuit. The circuitry was revised (ACN-C-174) to supply power to the timers from an uninterruptible source to insure that the timer would not reset if a loss of power occurred at some point after a CIB.
Loss of power would cause the timer to reset to beginning of the timing cycle and would not begin its cycle until power had been restored to the emergency AC buses.
This would prevent the fans from starting after one hour.
When the change was implemented on the drawings, the power source assigned was not uninter-ruptible as had been stated in the ACN.
2.
Immediate Action Taken E&DCR D-5169-506 was issued to revise the circuitry and power the CIB timers from the CAT IE 125VDC battery system.
Mr. L. M. Rabenau, Lead Compliance Engineer, Beaver Valley Power Station Unit No. 2, contacted Mr. Dave Limroth, NRC Region I, of this concern on March 27,1987.
On April 24, 1987, Mr. Rabenau contacted Mr. L. Tripp, NRC Region I, to request a one week extension on the filing date for the report for SDR 87-08.
This extension was to allow for further evaluation of reportability, and was granted by Mr. Tripp.
3.
Description of Deficiency CIB timers which require uninterruptible power to prevent resetting the timers on a loss of offsite power subsequent to a CIB are powered from an emergency AC distribution panel which is fed from an emergency MCC.
Loss of power will interrupt power to the MCC and the distribution panels.
4.
Analysis of Safety Implication The Loss of Offsite Power (LOOP) design basis for BVPS-2 is consistently identified throughtout the BVPS-2 FSAR as LOOP coincident with any postu-lated event.
This assumption is a design requirement consistent with NRC regulations.
It defines the set of equipment which can be credited for accident mitigation.
It is not used to define a dynamic transient concur-rent with or following an accident. Loss of offsite power events at times t > 0 are not universally evaluated or assumed. Within this design basis, the emergency diesel generators start on either a safety injection signal
oe
.. (SIS), or a loss of preferred power to the emergency buses and thus pro-vide a backup power source to safety-related loads.
Given the original design and a LOOP coincident with an SIS, the referenced timers would receive power from the emergency diesel generators upon receipt of the CIB signal.
Since the design basis did not assume an intermediate loss of power to these buses, the timers would cause the start of the emergency pressurization fans 60 minutes after receipt of the CIB signal.
Because the postulated sequence of events is beyond the design basis for BVPS-2 and the design as originally provided would function correctly within the parameters defined by design oasis assumptions and events, there is no deficiency in plant design and the modification of the timer power source to a DC power supply is an enhancement to safety system reli-ability.
5.
Corrective Action The power supplies were changed to a DC source as described in E&DCR D-5169-506, which was closed on April 11, 1987.
6.
Additional Report No Additional Reports are expected.
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