ML20059F371
| ML20059F371 | |
| Person / Time | |
|---|---|
| Site: | Fermi  |
| Issue date: | 10/26/1993 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20059F366 | List: |
| References | |
| NUDOCS 9311040269 | |
| Download: ML20059F371 (4) | |
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i SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO. 94 TO FACILITY OPERATING LICENSE NO. NPF-43 DETROIT EDISON COMPANY FERMI-2 DOCKET NO. 50-341
1.0 INTRODUCTION
By letter dated March 23, 1993, the Detroit Edison Company, the licensee, proposed to amend its operating license for Fermi Unit 2 (Fermi). The amendment consisted of modifying License Condition 2.C.(10) which pertains to the Emergency Diesel Generators (EDGs). This license condition requires the following activities:
(1) Perform gap checks on each EDG after each automatic unprelubricated engine start, or every six months, whichever occurs first.
(2) Obtain and analyze, once each month, an engine lube oil sample from each EDG except when an EDG is unavailable for service.
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In its letter, the licensee proposed to eliminate the first activity requiring EDG main engine bearing gap checks. The license condition was specified in i
Amendment 12 to the Fermi operating license as a result of several upper i
crankline main bearing problems encountered with the Fermi QGs during the initial plant startup in 1985. The licensee stated that, since the issuance j
of Amendment 12 in 1987, the performance of this activity has revealed no adverse bearing conditions, and has resulted in high EDG unavailability. The licensee thus concluded that this requirement is no longer warranted.
2.0 DISCUSSION l
The standby AC power system for Fermi consists of four Fairbanks Morse 1
opposed-piston EDGs.
Each EDG is a 12-cylinder, turbocharged engine, and is rated for continuous duty at 3967 horsepower. During initial plant startup in January of 1985, the licensee reported problems with the main bearings on several of the engines. Although the root cause of the problems was never identified with certainty, it is generally believed that the major contributor was inadequate bearing lubrication during unprelubricated fast starts of the engines. Before the occurrence of the bearing problems, the licensee did not manually prelube the engines prior to planned starts such as surveillance testing. The licensee subsequently revised its EDG testing procedures to include manual prelubing prior to all planned starts. Unplanned starts, such 1
as those in response to loss-of-offsite power and spurious or actual accident signals, are not manually prelubricated. Fermi encountered additional bearing problems in November of 1985. Again, the root cause of the problems could not 9311040269 931026 I
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be definitively detemined; however, several likely contributing factors were 4
identified (e.g., alsalignment of bearing caps, adequacy of the brand of lube oil, and possible contamination of the lube oil), and corrective actions were implemented.
Following the problems encountered in November of 1985, the licensee perfomed a Reliability Demonstration Test Program to confirm the operability of the EDGs.
In addition, the licensee proposed to perform a gap check inspection of the upper and lower crankline main bearings every six months in order to more closely monitor bearing conditions. Unprelubricated engine starts were not included in the Demonstration Test Program since the licensee and the staff agreed that such starts were detrimental to the engine and should be l
minimized. To address the concern with unprelubricated starts, the licensee j
was required to add a provision to its proposed EDG inspection program which required that bearing gap checks be performed after every unprelubricated engine start. The EDG main bearing gap check inspection program was subsequently included as part of License Condition 2.C.(10).
In its March 23, 1993, submittal, the licensee stated that since License Condition 2.C.(10) became effective, the Fermi EDGs have undergone a total of approximately 60 bearing gap checks, approximately 22 of which were performed following unprelubricated fast starts. The licensee stated that the gap checks have not revealed any signs of bearing distress on the upper or lower crankline main Wings of any of the four EDGs. The licensee further stated that, since eacu uu must be taken out of service for approximately 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> in order to perform the gap checks, the license condition has resulted in high EDG unavailability. The licensee also noted that the Fermi Technical Specifications require an 18-month inspection of each EDG in accordance with the manufacturers recommendations, and that this requirement includes engine main bearing gap checks.
i 3.0 EVALUATION The current license condition requiring bearing gap checks after every unprelubricated engine start or every six months, whichever occurs first, was imposed because of the inherent uncertainties in determining the root cause(s) of the 1985 bearing problems, and because of the limitations of the subsequent Demonstration Test Program. Although the root cause of the problems was not definitively determined, it was generally believed that the problems were i
likely due to the excessive number of unprelubricated engine starts in combination with some of the additional contributing factors which were identified and corrected by the licensee.
The potential detrimental effects of unprelubricated fast starts of EDGs have been addressed by the staff in previous generic correspondences. Generic Letter 83-41, " Fast Cold Starts of Diesel Generators", requested that i
licensees provide information related to the frequency of fast cold starts (i.e., unprelubricated fast starts) and the potential for diesel generator degradation. Generic Letter 84-15, " Proposed Staff Actions To Improve And
2 Maintain Diesel Generator Reliability" suggested changes in Technical Specifications and EDG testing procedures to improve diesel generator reliability, and specifically requested that licensees reduce the number of unprelubricated fast cold test starts. According to a study conducted by the Fermi licensee in 1985, all other nuclear plants which employ this type of engine manually prelubricate the engine prior to all planned starts.
In addition, the EDG manufacturer, Coltec Industries, strongly recomends prelubing prior to planned engine starts.
In its March 23, 1993, submittal, the licensee indicated that, since the j
implementation of the corrective actions in 1985 and 1986, the Fermi EDGs have not experienced any engine bearing problems. The manner in which the licensee now operates its EDGs appears consistent with the manufacturers recommendations, and with the manner in which other utilities operate similar EDGs.
It is also noted that the licensee's Technical Specifications require that the EDGs be maintained in accordance with the manufacturers recommendations. As such, the licensee will continue to perform EDG bearing gap checks about every 18 months.
Based on the above, the staff agrees with the licensee that continuing to perform the bearing gap checks in accordance with License Condition 2.C.(10) results in high EDG unavailability with no j
apparent increase in engine reliability. The staff finds that continuation of the special bearing gap checks in accordance with License Condition 2.C.(10) is not warranted.
Therefore, the licensee's request to amend its operating i
license to eliminate the special bearing gap check requirement is acceptable.
4.0 STATE CONSULTATION
in accordance with the Commission's regulations, the Michigan State official was notified of the proposed issuance of the amendment. The State official had no comments.
5.0 ENVIRONMENTAL CONSIDERATION
The amendment changes a requirement with respect to the installation or use of a facility component located within the restricted area as defined in 10 CFR 3
3 art 20, and changes surveillance requirements. The staff has determined that the amendment involves no significant increase in the amounts, and no significant change in the types, of any effluents that may be released offsite, and that there is no significant increase in individual or cumulative occupational radiation exposure. The Commission has previously issued a proposed finding that the amendment involves no significant hazards consideration and there has been no n"blic comment on such finding (58 FR 28054). Accordingly, the amendment meets the eligibility criteria for categorical exclusion set forth in 10 CFR 51.22(c)(9).
Pursuant to 10 CFR 51.22(b), no environmental impact statement or environmental assessment need be prepared in connection with the issuance of the amendment.
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6.0 CONCLUSION
The staff has concluded, based on the considerations discussed above, that:
1 (1 there is reasonable assurance that the health and safety of the public wi 1 not be endangered by operation in the proposed manner, (2) such activities will be conducted in compliance with the Commission's regulations,.
and (3) the issuance of the amendment will not be inimical to the common defense and security or.to the' health and safety of the public.
Principal Contributor:
M. McBrearty Date:
October 26, 1993 i
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