ML20206B537

Safety Evaluation Supporting Util Request to Amend License Condition 2.C(10), Emergency Diesel Generator Lube Oil Surveillance Program. NRC Does Not Agree Condition Should Be Revised by Substituting for Mar 1985 Ltr

ML20206B537
Person / Time
Site:	Fermi
Issue date:	04/07/1987
From:	Office of Nuclear Reactor Regulation
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Shared Package
ML20206B526	List: ML20206B521 ML20206B537
References
NUDOCS 8704090203
Download: ML20206B537 (4)

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\*****/ SAFETY EVALUATION REPORT FERMI-2 FMERGENCY DIESEL GENERATOR ENGINE LUBE OIL / REARING SURVEILLANCE TEST PROGRAM

1.0 INTRODUCTION

As a result of the emergency diesel generator (EDG) engine bearing failure which occurred in January 1985, the Detroit Edison Company (Deco or the Licenseei proposed an EDG engine lube oil surveillance test program to en-sure the continued reliability of the EDGs. The program was described to the NRC staff by DECO in letters dated March 6, March 14, and March 15, 1985.

The NRC staff's evaluation and acceptance of the proposed program was docu-mented in Supplement No. 5 to the Fermi-? SER (NUREG-0798) and the following license condition cited in the Fermi-? Operating License No. NPF-43 under Paragraph 2.C.:

"(10) DECO shall implement its commitments regarding the surveil-lance program for the lubricating oil system of the emergency diesel generators as described in its letters dated March 6, March 14, and March 15, 1985."

The surveillance progran required quarterly disassembly and inspection of each EDG engine oil filter and spectrographic analysis of the oil filter media as a means of predicting incipient bearing failures. As a result of additicnal EDG engine bearing failures in November 1985, and December 1985, DECO proposed an augmented surveillance program which included periodic bearing inspections. In its July 16, 1986 letter accepting the augmented surveillance program proposed, the NRC staff required, among other thinos, that a gap check he performed on the thrust bearing of each EDG engine after every automatic unprelubricated (dry) start or every six months, whichever occurred first; and that a special visual inspection of the upper thrust bearing of EDG engine No.13 he performed at the next scheduled 18-month Technical Specification surveillance requirement, or at the time the envelope of engine starts established by the licensee's demonstration test program (described in DECO letter dated March 18, 19861 was exceeded. In a letter dated October 14, 1986, the licensee comitted to performing the bearing inspections as defined in the NRC staff's July 16, 1986 letter proposing that a time period of seven days be permitted to perform the bearing gap checks, and a time period of 30 days be permitted to perform the visual inspection of the EDG No.13 engine upper main thrust bearing, to allow for flexibility in scheduling and performing these special inspections, and avoid unnecessary plant shutdowns. The staff accepted DECO's proposed timing for the performance of these special inspections in a letter dated January 9, 1987, with the condition that the plant be in the appropriate EDG Technical Specification limited condition of operation (LCO) if the window 1 of test performance is exceeded. )

By letter dated January 28, 1987, DECO submitted a proposed license amend-ment, to revise License Condition ?.C(10) to delete from the EDG lube oil I surveillance ornaram, the requirement for the quarterly disassembly and )

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inspection of engine lube oil filters and the spectrographic analysis of the oil filter media; and to include in the amended license condition, the special engine bearing inspections discussed in the proceeding para-graph above. Following is a report of the staff's review, findings and conclusions relative to the January 28, 1987 license amendment proposal.

?.0 EVALUATION The current license condition (Paragraph 2.C(101 of Operating License No. NPF-43), which reouires the implementation of the Fermi-2 EDG engine lube oil surveillance program, consists of two major activities es follows:

(1) The quarterly disassembly, inspection and replacement of engine oil filters. If bearing material is found in the oil filter the main bearings of that ergine are to be inspected, i.e, a gap check per-fomed. In addition, a spectrographic analysis is to be perfomed of the cil filter media and deposits that are found during the quar-terly inspection of the filter.

(2) The aralysis of engine oil samples on a monthly basis for trend determinations. i By letter dated January 28, 1987, the licensee proposed deletion of surveillances relating to the lube oil disassembly, filter inspection and analysis. The justification for this deletion was based on the accumulated data that have been obtained from the inspections per-fomed to date. Deco's evaluation of these data indicates that the lube oil filter inspections performed were ineffective in predicting incipient bearing failure. It was for this reeson that the lube oil filter disassembly, inspection, and oil filter media analyses were initially proposed.

As discussed in the staff's SER dated iluly 16, 1986 EDG Nos. 11 and 13 experienced bearing failures in late 1985. The lube oil filter in-spections/ analyses prior to the bearing failures did not indicate any adverse conditions. In addition, the inspection following the bearing failures revealed that numerous metallic fragnents were visible prior to removing the lube oil filters from the filter vessel. Upon completion of the disassembly of the filter redia and subsequent spectro- l oraphic analysis, it was fcund that the detailed aralysis was no more J infomative that the visual inspection of the exterior of the filter

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media. Inspections performed since repairs o' the EDGs were made, have 1 also not revealed any new infomation concerning bearing status.

Additionally, the EDG vendor has recommended that the quarterly filter inspections be performed, without the disassembly of the filter media and subsequent replacement of the filter.

DECO has indicated that there is also an advantage to diesel operation with the elimination of the freover.t filter replacement. Elimination of unnecessary filter changes will reduce the likelihood of contanipating the lube oil system.

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! The licensee, although proposing deletion of the ' detailed filter media j inspection, plans to continue the lube oil monitoring program.

in an attempt to understand the significance o' the licensee's proposal l relative to the modification of the License Condition, one must first  !

understand when bearing gap checks are required. Currently, when a lube.-

oil analysis or' oil filter analysis reveals unfavorable results (i.e.,

specified limits are exceeded), a EDG bearing gap check is required to bc 4

performed. . This is in addition to the normally required 18 month bearing -

gap inspection. Also, following the late 1985 bearing failures, DECO com-mitted to perform a EDG bearing gap check every 6 months or a gep check-

after every unplanned start, whichever occurs first, and an inspection of

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EDG No. 13 upper thrust bearing as described in the staff's SER dated l July 16, 1986. It should be noted that the Fermi-2 License Condition does l not reference any of these required gap checks other than those that are identified through the lube oil surveillance program.

In summary, the licensee's rationale to support the' modified and augmented j EDG surveillance program is a follows:

i The lube oil filter redia inspection has not been e#fectiv4 in l

monitoring bearing condition; i'

Examination of the filter exterior media will continue to be conducted l on a periodic basis to provide information on the gereral condition of the filter; a

i The increased frecuency of gap checks as' discussed above would be more i effective in providing information about incipient bearing failure than j would the quarterly disassembly and inspection of-filter and filter media; i

Engine lube oil sampling will' continue to be performed and will provide  !

l revelant information on the condition of the oil; I Elimination of quarterly filter replacement will reduce the l potential for introducing contamination into the lube oil system.

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3.0 CONCLUSION

i s Based on its review of the information contained in the licensee's

{ February 28, 1987 submittal, the staff agrees that there appears to 4 be no safety benefit to continue to require the licensee to disassemble i the EDG engine oil filters cuarterly as a means of predicting incipient i bearing failure. The modified surveillance program proposed; i.e. the monthly sampling of engine lube oil and the augmented bearing gap checks, I should be sufficient for monitoring ergine bearing conditions _ However,

! the staff does not agree that License Condition 2.C(10) be revised by j simply substituting, by reference, the February 28, 1987 letter for the'

March 1985 letters currently specified in the plant operating license.

The sta'f believes that the license condition should be self-explanatory to the maximum extent possible, and recommends that the following license condition, which would eccompass the modified and augmented EDG surveil-lance program proposed, be consider by the licensee as an_' alternative:

l (10) Emeroency Diesel Generator (EDG) Enoine Inspection Proaram (a' DECO shall perform gap checks on each EDG engine thrust bearing after every automatic, unprelubricated engine start or every six months, whichever occurs first, within seven days of the engine start. The plant shall be in the appropriate Technical Specific-ations LCO if the window of test performance is exceeded.

(h) DECO shall perform a visual inspection of the EDG No.13 engine upper main thrust bearing at the next scheduled 18-month Technical Specification surveillance requirement, or at'the time the envelope of engine starts established in the demonstratier. test program (des-cribed in DECO letter dated March 18,1986) is exceeded, whichever occurs first, within 30 days from the time the inspection is scheduled to be performed.

(c) DECO shall anclyze EDG engine lube oil samples nonthly. Should 4 the samples analy7ed identify foreign matter / deposits which could  :

degrade engine bearing performance, DECO shall inform the NRC immedittely and suhrit a report of analysis results and the detail corrective action to be taken within 15 working days following such notification.

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