NRC-96-0071, Forwards Response to NRC Re Violations Noted in Insp Rept 50-341/96-04.C/A:developed Hydraulic Computer Models of SW Sys

Forwards Response to NRC Re Violations Noted in Insp Rept 50-341/96-04.C/A:developed Hydraulic Computer Models of SW Sys

ML20115H344
Person / Time
Site:	Fermi
Issue date:	07/15/1996
From:	Gipson D DETROIT EDISON CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
CON-NRC-96-0071, CON-NRC-96-71 NUDOCS 9607230070
Download: ML20115H344 (7)

Text

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G Dougiss M. Gipson Seruor Vee President Nuclear Generaten Detroit.

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6400 North Dune Highway Newport, Mch+gan 48166 (313) 586-5249 1

10 CFR 2.201 July 15,1996 NRC-96-0071 U. S. Nuclear Regulatory Commission Attn: Document Control Desk l

Washington D. C. 20555 i

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References:

1) Fermi 2 1-NRC Docket No. 50-341 NRC License No. NPF-43

2) Integrated Inspection Report No. 50-341/96004, l

l dated June 14,1996

Subject:

Reply to Notices of Violation (96004-06 and 96004-05i 4

l Enclosed is Detroit Edison's response to the Notices of Violation (NOVs) contained in Reference 2. The NOVs concern the Residual Heat Removal Service Water (RHRSW) system piping to the mechanical draft cooling towers (MDCTs).

On Febmary 23,1995, reduced flow was observed for several service water systems when the Division 2 RHRSW system was aligned to its associated MDCT. In addition, on March 31,1996, the drain lines that provide freeze protection for these pipes were found plugged. Detroit Edison acknowledges that a lack of rigor and questioning attitude was exhibited in past investigations of these system problems.

The following commitments, as noted in the response to the NOVs, are being made in this letter:

1. Plant Support Engiraering will conduct training by September 6,1996, regarding lessons learned from the RHRSW drain line plugging DER. This 4~ %"

i training will include cause determination expectations and the need to be e n awue of passive design attributes that may need to be field verified to ensure their functional intent is being maintained.

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2. Design basis documentation will be updated by October 31,1996, to include reference to the drain lines for the RHRSW lines to the MDCTs.

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9607230070 960715 PDR ADOCK 05000341 I l 4

G PDR i

4 July 15,1996 l

NRC-96-0071 l

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3. Detroit Edison is presently evaluating the addition of positive flow verification devices in the RHRSW return line drains to the RHR reservoir, After the completion of this review, appropriate procedures will be updated by October 31,1996, (irregardless if the positive flow verification devices are added) to require verification j

that the RHRSW return line drains are not plugged while the flow

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path to the MDCTs is in service.

If there are any questions related to this response, please contact Ken Riches, Compliance Engineer at (313) 586-5529.

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Sincerely, Enclosure 1

cc:

M. J. Jordan A. J. Kugler H. J. Miller A. Vegel -

Region III

J July 15,1996 NRC-96-0071 l

Page 3 l

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l I, DOUGLAS R. GIPSON, do hereby affirm that the foregoing statements are based on facts and circumstances which are tme and accurate to the best of my knowledge and belief.

l DOUGLA$ R. GIPSON Senior Vice President Nuclear Generation On this

/8 day of M

,1996, before me personally appeared Douglas R. Gipson[yeing fft duly sworn and says that he executed the foregoing as his free act and' deed.

k Notary Public ROSAUE A. ARMETTA 40TWPUBLIC MONROECOUNTY,Mi MYCOMMISSf0N EXPlRES10/1U99 L

Enclosure to NRC-96-0071 Page1 Resoonse to Notice of Violation 50-341/96004-06 Statement of Notice of Violation 10 CFR Part 50, Appendix B, Criteria XVI " Corrective Actions" requires, in part, that in the case of significant conditions adverse to quality, measures be established to assure that the cause of the condition is determined and corrective action taken to preclude repetition.

Contrary to the above, on Febmary 23,1995, a flow reduction occurred in the Division II Residual Heat Removal Service Water, Emergency Equipment Service Water, and Emergency Diesel Generator 13 Service Water systems, which was a significant condition adverse to quality, and as of May 2,1996, the licensee failed to identify the cause for the condition.

Reason for the Violation On February 23,1995, the Division 2 Residual Heat Removal Service Water (RHRSW) was aligned to the Mechanical Draft Cooling Tower (MDCT) to facilitate chemical treatment of the RHR reservoir. At this time, both RHRSW pumps, one emergency diesel generator service water (EDGSW) pump and one emergency equipment service water (EESW) pump were all operating in Division 2. Simultaneous operation of the RHRSW, EESW and EDGSW systems in this configuration is rare. During this evolution, a reduction in flow for the operating systems was observed. While a reduction in flow was expected due to increased system flow resistance for this operating configuration, the magnitude of the actual flow reduction had not been determined. A deviation event report (DER) was initiated to document the event. The DER operability evaluation determined, based on the ambient and reservoir temperatures, that all systems were functioning with sufficient flow to ensure their design function was maintained and evidence of mechanical malfunctioning was not readily apparent.

The DER documented that design basis verification hydraulic computer models of the involved systems were under development and that field validation would be performed. Plant design personnel believed that the February 23,1995, observed service water system flows were within the expected flows for this alignment. Accordingly, the recommended DER corrective action was to revise various procedures to include a caution that starting multiple service water pumps and aligning to the MDCT may impact operating system flow characteristics. The action to revise the procedures was transferred to another DER that was being used to resolve service water related issues. The February 23,1995, event DER was closed, without a cause statement being completed, based upon this proposed action. The DER closure without a cause determination does not meet Fermi 2 expectations for DER processing.

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Enclosure to ~

l' NRC-96-0071 l

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l A comparison of the field validated computer model flows to the February 23, 1995, documented that lower system flows would be experienced, but not to the extent of those observed on February 23,1995. The low flow DER was not reopened to address this difference between validated hydraulic model -

flows and the actual flows observed on February 23,1995. In retrospect, the most probable cause of the February 23,1995, flow reduction was due partly to blockage of the RHRSW flow path to the MDCT. The potential that the l

l partial flow blockage was due to the formation ofice within the pipe cannot i

be mied out.

Corrective Actions Taken and the Results Achieved Hydraulic computer models of the service water systems were developed and field validated. Based on the results of the computer model field validations, various procedures have been revised to reflect the expected flow conditions.

The DER process has been restructured since February 23,1995, and more f

guidance has been provided on cause determination for DERs with potential j

significant conditions adverse to quality.

Corrective Actions Taken to Prevent Recurrence Plant Support Engineering will conduct training by September 6,1996, regarding lessons learned from the RHRSW Febmary 23,1995, low flow l

DER. This training will include cause determination expectations.

The corrective actions described in the response to NOV 96004-05 will i

preclude the potential for partial blockage of the RHRSW return line to the MDCTs due to ice formation from reducing flow in the line.

Date When Full Compliance Will Be Achieved Detroit Edison is presently in full compliance.

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Enclosure to c'

NRC-96-0071 Page 3 4

Response to Notice of Violation 50-341/96004-05 i

Statement of Notice of Violation 1

l 10 CFR Part 50, Appendix B, Criteria XI, " Test Control," requires, in part, 1

that all testing required to demonstrate that stmetures, systems, and j

components will perform satisfactorily in service is identified and performed.

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Contrary to the above, since initial startup testing, no testing was performed by the licensee to demonstrate that the one inch drain lines on the Division I l

i and II Residual Heat Removal Service Water return lines to the mechanical draft cooling towers would perform their design function satisfactorily.

i Reason for the Violation The drain lines for the RHRSW lines to the MDCT perform a passive function of preven +ing the lines from being maintah ed filled when the lines are not alignec#r ervice. This is a preventive measure from a freezing standpoint, j

but no credit was taken for these drain lines in any accident analyses nor was their function explicitly described in any design basis document.

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i Based on various system oriented reviews (e.g., design basis reviews, technical specification surveillance reviews) Detroit Edison believes that safety-significant active and passive design basis accident mitigation functions have been addressed Fom a periodic monitoring perspective.

Corrective Actions Taken and the Results Achieved 1

The drain lines for the RHRSW lines to the MDCTs have been unplugged and l

verified to function properly. As an interim measure, the drain lines have been included in the routine System Engineering walkdown checklist fce ceriodic monitoring.

Corrective Actions Taken to Prevent Recurrence Plant Tupport Engineering will conduct training by September 6,1996, regarug lessons learned from the RHRSW drain line plugging DER. This traisi is will include the need to be aware of passive design attributes that J

may need to be field verified to ensure their functional intent is being maintained.

Design basis documentation will be updated by October 31,1996, to include reference to the drain lines for the RHRSW lines to the MDCTs.

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Enclosure to c'

NRC-96-0071 Page 4 Detroit Edison is presently evaluating the addition of positive flow verification devices in the RHRSW return line drains to the RHR reservoir. After the completion of this review, appropriate procedures will be updated by October 31,1M6, (irregardless if the positive flow verification devices are added) to require verification that the RHRSW return line drains are not plugged while the flow path to the MDCTs is in sersice.

Date When Full Compliance Will Be Achieved Detroit Edison is presently in full compliance.

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