ML20196L538

Forwards Final Design Description,Atws Mitigation Sys Actuation Circuitry & ATWS Mitigation Sys Actuation Circuitry Response to Unit Transients, Based on Mods to Plants to Install Modified Options 3 in Design Package

ML20196L538
Person / Time
Site:	Mcguire, Catawba, McGuire, 05000000
Issue date:	06/01/1988
From:	Tucker H DUKE POWER CO.
To:	NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM)
Shared Package
ML20196L539	List: ML20196L538 ML20196L628 ML20196L642
References
NUDOCS 8807070575
Download: ML20196L538 (2)

Text

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DUKE POWER GoxPm P.O. HOX 03180 CHARLOTrE. N.O. 28242 HAL n. TUCKER TE LEPHONE V90E Parasers?

(70l) 073-6 31 fttOLFAR PSODUCTIO15

+

' June 1, 1988 U.:S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, D. C. 20555

Subject:

Catawba Nuclear Station Docket Nos. 50-413 and 50-414 McGuire Nuclear Station Docket Nos. 50-369 and 50-370

(

Gentlemen:

Duke Power Company has in progress modifications to the above referenced plants to install a modified version of Option 3 contained in the WOG AMSAC Generic Design Package. During our normal design review process two (2) issues have been identified of which we are hereby informing NRC Staff.

The first issue concerns the number of auxiliary feedwater pumps required once an AWS event is detected. Our present design (reference Attachment I "Final Design Description") which has been reviewed and approved by the NRC (reference Attachment II "Safety Evaluation Report") requires that two motor driven pumps start.

Phone conversations with Westinghouse engineers have indicated that while the boundary of the calculation is based on a flow almost double our motor driven capacity, the sensitivity to lower flow rates is very low.

Based on the low sensitivity of an AWS event to lower levels of auxiliary feedwater flow rates, it was concluded that the present design was acceptable and that additional auxiliary feedwater capacity was not required for Duke Power Company's specific AMSAC design.

The second issue concerns a change in feedwater system operating procedures which was not covered in the Westinghouse Topical Report WCAP-10858-P-A-Revision 1.

After the original design (reference Attachment I) and NRC approval process

--(reference Attachment II) was completed, plant operating procedures at McGuire Nuclear Station were slightly modified to allow operation above 50 percent power levels with the Feedwater Control Bypass Valves (FCBVs) fully open. This operating change was found to produce an offset in the respective Feedwater l

Control Valves (FCVs) which would impact the accuracy of the)flowpath monitoring l

portion of the AMSAC design.

l The new operating procedure was analyzed (reference Attachment III "ATWAS Mitigation System Actuation Circuitry Response To Unit Transients") and found to l_

have flowpath arrangements which are very similar to those associated with the feedwater valve arrangements of the D5 model steam generators. The conclusion was reached that because of this similarity flowpath blockage can only occur if both the FCV and FCBV are closed or the Feedwater Isolation Valve (FIV) is f

l closed. From this conclusion a plant specific design alteration was made to McGuire Nuclear Station to allow for flow through the FCBVs and reduce the l

probability of spurious trips due to FCV movement during controlled transient events.-

8807070575 88060 DR ADOCK 0500

U. S. Nuclear Ragulatory Commission June 1, 1988 Page Two Westinghouse has been informed of these issues and has been requested to provide a written response in a timely manner to support the current McGuire 2 outage work.

We are providing this letter to NRC Staff for information. No specific requests for review are intended. Duke considers that this final design meets applicable requirements upon confirmation by written response from Westinghouse.

Very truly yours,

/

/

$/

w Hal B. Tucker RLG/43/sbn Attachment xc:

(w/ attachment)

Mr. Darl Hood Office of Nuclear Reactor Regulations U. S. Nuclear Regulatory Commission Washington, D. C.

20555 Mr. W. T. Orders NRC Resident Inspector l

McGuire Nuclear Station Dr. J. Nelson Grace, Regional Administrator U. S. Nuclear Regulatory Commission i

Region II i

101 Marietta Street, NW, Suite 2900 l

Atlanta, Georgia 30323 u

1-9

U.'s. Nucitar-R:guletory Commission L

Junn 1, 1988 Page Two Westinghouse. has been informed of these' issues and has been requested to provide a written response in a timely manner to-support the current McGuire 2 outage

-work.

We are providing this. letter to NRC Staff-for information. No specific requests for review are intended. Duke considers that this final design meets applicable requirements upon confirmation'by written response from Westinghouse.

Very truly :ours, p

f,Jpe#

Hal B. Tucker RLG/43/sbn Attachment xc:

(w/ attachment)

Mr. Darl Hood Office of Nuclear Reactor Regulations U. S. Nuclear Regulatory Commission Washington, D. C.

20555 Mr. W. T. Orders NRC Resident Inspector McGuire Nuclear Station t

Dr. J. Nelson Grace, Regional Administrator U. S. Nuclear Regulatory Commission Region II 101 Marietta Street,'NW, Suite 2900 Atlanta, Georgia 30323 l

J