ML20082T265

Responds to Concerns Noted in Insp Rept 50-361/91-19 Re Salt Water Cooling Sys,Backflush Repair During Apr-May Outage,Consequences of June Heat Treatment,Swc Sys Matl Condition & Insufficient Questioning Personnel Attitude

ML20082T265
Person / Time
Site:	San Onofre
Issue date:	09/06/1991
From:	Ray H SOUTHERN CALIFORNIA EDISON CO.
To:	Zimmerman R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V)
References
NUDOCS 9109180179
Download: ML20082T265 (4)

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Imc REGl0ll y Southem Califomia Edison Company ful D -? Cl 7: 38 23 PARKER STREET IFo% L, C ALIF ORNI A 92768

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September 6, 1991 Mr. Roy Zimmerman, Director Division of Reactor Safety and Projects U. S. Nuclear Regulatory Commission, Region V 1450 Maria Lane, Suite 210 Walnut Creek, California 94596-5368

Subject:

Docket No. 50-361 Response to NRC Inspection Report Concerns San Onofre Nuclear Generating Station, Unit 2 Your letter dated August 2,1991, forwarded NRC Inspection Report (IR) 91-19 and identified two areas of particular concern. The purpose of this letter is to respond to these concerns and to indicate the actions which we are taking.

Salt Water Coolina System The General Conclusions and Specific Findings of IR 91-19 include the following:

"A concern was also identified regarding repeated removal of the Unit 2 Train A salt water cooling (SWC) heat exchanger from service for cleaning since mid-June 1991. The backwash capability for the Train A heat exchanger was taken out of service in December 1990 because of valve operability concerns. Repair of this backwash capability was not accomplished during the April-May-1991 Unit 2 outage because of schedule constraints and the licensee's understanding that necessary parts were not available. However, the licensee learned after the end of this inspection period that the parts necessary to repair the backwash valves had been available in the warehouse at the time of that outage.

It appears that additional attention to planning could have enabled the licensee to maintain higher availability of this important system."

This concern was then underscored in your forwarding letter which included the conclusion that:

"These outages have resulted in significant (approximately 20%)

unavailability of one train of an important safety-related system. The backflush capability you provided for this heat exchanger in the mid-1980s would have avoided this need for frequent cleaning.

However, this feature has been inoperable since December 1990, even though repairs could have been accomplished during the April-May 1991 Unit 2 outage.

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Mr. Roy Zimmerman, Cirector September 6, 1991 These SWC system train outages, along with corrosion and housekeeping discrepancies discussed in the enclosed report, indicate that additional planning and management attention are warranted to minimize train unavailability in this important system."

Backflush Repair Durina the April-Ja_y 0utigg Based on experience with the existing valves, a modification had been planned for the August refueling outage.

This modification includes a material substitution for the valve stem bushings to enhance bushing and ster wear resistance.

At the time of the unplanned RCP outage, material to perform the modification was not available, however, valve stem bushings of the original design were on-site.

Use of the original design bushings would have corresponded to an interim repair pending impeementation of the modification during the August refueling.

For the reasons stated below, SCE decided not to perform the backflush valve repairs during the unplanned outage.

1.

From the time of the removal of the backflush capability from service in December 1990 until +he RCP outage, the heat exchanger had been removed from service three times for cleasiing, a rate of Icss than once a month.

The average amount of time the heat exchanger remained out of service for cleaning was about 37 hours4.282407e-4 days <br />0.0103 hours <br />6.117725e-5 weeks <br />1.40785e-5 months <br /> per occurrence. This resulted in an overall unavailability of less than 4%

It was considered reasonable to expect the Train A heat exchanger cleaning requirements and resultant unavailability of the SWC system for the remaining time until the refueling would be similar to that experienced during the five months prior to the RCP outage.

This rate of heet exchanger cleaning was consistent with our experience prior to implementation of the backflush capability in 1985 and was not considered unacceptable, although of course, any reduced unavailability is desirable.

2.

Because material to perform the modification was not available, and since the upgrade was already scheduled for the August refueling outage, SCE's decision concerning repairs to restore the backflush to service de aended on our judgement concerning the Sr.fety benefit -

to be gained )y an irterim repair.

Repair of the valva was estimated to require a SWC/CCW system outage, in Mode-4 or 5, of about seven days. -In light of the current heightened awareness of shutdown risks (especially durin mid-loop operation), we believe that repair of the valves, which required substantial Mode 4 ur 5 unavailability would not provide a

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Mr. Roy Zimmerman, Director-

-3 September 6, 1991 significant safety bent: * <!.*n contrasted with the expected 3 to 4 days of Mode 1 SWC syste mailability (4% of the period until the refueling) to be expected.. the interim repair was not made.

3.

To have performed the repair during the RCP oatage following return of the steam generators to service would have extended this unplanned outage by about ten days and reduced the already short interval between the upcoming Unit 2 and Unit 3 scheduled refuelings.

Conscau_ sages of June Heat Treatment Although-Train A had experienced an unavailability for cleaning of less than 4% in the five months from December 1990 to April 1991, following the heat treatment on June 22 (over a month after the end of the unplanned outage) frequent removal from service was required, as discussed on Page 11 of IR 91-19. The overall unavailaollity rate between the June heat treatment and the commencement of the refueling outage was in excess of 20%.

As' a-result of the Unit 2 trip in March, the reduced power operation in late March to early April for the main circulating water r"mp motor repairs, and the RCP Seal outage, a scheduled heat treatment evolution for Unit 2 was e

delayed. Although SCE expected some additional marine growth as a result of this delay -in heat treatment, based on previous ex,erience we did not expect a significant increase in the need to clean the WC leat exchangers.

Contrary to our espectations, however, the narine growth problem was so severe that the Train A-heat exchanger required cleaning nine times duri,ig the period from th completion of_the RCP outage until the start of the refueling outage, (six of those cleanings were required during a five week period from mid-June tomid-July).

As an indication of the severity of this marine ingress, even with the backflush capability in operation, the Unit 2 SWC syst6m Train B heat-exchanger was removed from service for cleaning during this period.

The increased influx of merine organisms which caused this substantial increase in unavailability was used by an unusual marine condition, which

.was not anticipated at-the time our decision concerning repair of the backflush valves during the unplanned outage.

SCE has in!tiated an evaluation into the unusual marine 'rowth activity during this period to better understand the observed conditions and to provide

uldelines for future planning.

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I Mr. Roy Zimmerman, Director-September 6, 1991 SWC System Material' Condition following an NRC-Team Inspection in 1986 Edison established a Routine

' Maintenance Order which provides for-inspection and surface preservation of the SWC system on a regular basis. A Maintenance Order was established in February 1991-to provide for performing preservation work during the August refueling outage. -That work is now ongoing and has not identified a significant degradation of system fasteners or supports due to corrosion.

Insufficient 1v Ouestionina-Attitude by Personnel Your letter'. identified a concern in that the IR findings " indicate a need for

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a more questioning attitude in the conduct of safety-related activities". We are highly conscious of the 'need for alertness-and attention to detail by all personnel and-have reviewed each of the items discussed in the IR-with respect to indicating a lack of1a questioning attitude.

We continue'to seek-improving performance with res)ect to this issue.

For example,- in the Maintenance organization, we have 3een in the process of developing specific training for craftsmen to enhance the "self-checking" work ethic. The professionalism program in Operations and emphasis on-plant monitoring' have:resulted in noted improvements in. operator performance and further: improvement continues to be our expectation in this area.

In the Technical Division, we have been evaluating-the cognizant engineer job function with an expectation of altering its structure.

Included in this

effort will be an emphasis on attention to detail and the questioning attitude within th!s organization.

We appreciate your identification of the concerns addressed above. - If you have any: questions concerning our response, or if you require additional-information, please let me know.-

Sincerely, nn U.bQ-W n

cc:

J.: B.? Martin, Regional Administrator, NRC Region q 1

K. E. Perkins, Jr., Deputy Director, NRC Region V L. E. Kckajko, Project Manager, San Onofre Units 2&3

_C.-W.-Caldwell, NRC Senior' Resident I.1spector, San Onofre Units 1, 2&3

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