ML20011D677
| ML20011D677 | |
| Person / Time | |
|---|---|
| Site: | Davis Besse  |
| Issue date: | 12/22/1989 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20011D674 | List: |
| References | |
| NUDOCS 8912280228 | |
| Download: ML20011D677 (4) | |
Text
,
[ge rs eg'o, UNITED STATES E ' 3,. c 7 NUCLEAR REGULATORY COMMISSION wasmcTow. o. c. nsss g
\\....+ /
SAFETY EVALUA110N BY THE OFFICE OF. NUCLEAR REACTOR REGULATION RELATED T0 AMENDMEhT NO.141 TO FACILITY OPERATING LICENSE NO. NPF-3 TOLEDO EDISON COMPANY THE CLEVELAND ELECTRIC. ILLUMINATING COMPANY i
DAVIS BESSE NUCLEAR POWER STATION. UNIT NO. I DOCKET NO. 50-346
1.0 INTRODUCTION
i In its letter dated June 12, 1989, the Toledo Edison Company (the licensee) requested an anenament to the operating license for the Davis-Besse Nuclear power Station, Unit No.1, which would increase the inspection interval required by the plant's Technical Specifications (TS) of certain surveillance requirements for the emergency diesel generators (EDGs) contained in the present TS 4.8.1.1.2.d.1.
The proposed change would extend the affected inspection interval from its present requirement of at least once per 18 months during shutdown to a maximum inspection interval not to exceed 30 months.
The present surveillances in TS 4.8.1.1.2.d.1 require that each emergency diesel generator be inspected by procedures prepared in conjunction with its manufacturer's recommendations for this class of standby service.
The subject amendment also proposes to delete the applicability of the extension provisions of Specification 4.0.2 from this particular inspection. However this request is partially superseded by Amena-ment No.140 to the Davis-Besse license dated October 27, 1989, which deleted a portion of Specification 4.0.2.
The licensee also proposes an administrative change consisting of a renumbering of the steps in Specification 4.8.1.1.2.d.
The licensee subsequently submitted supplemental information regarding its original amendment request in its letter dated August 11, 1989. This supple-mental information was a copy of the Morrison-Knudsen Report No. 6993-2 (Revision
- 2) originally issued on February lb,1989 and subsequently modified on March 2 and August 2, 1989; Morrison-Knudsen is the manufacturer et the Davis-Besse EDGs. The subject report is the manufacturer's evaluation of the proposed extension of the surveillance interval cited above.
l 8912280228 891222
{DR ADOCK0500g6
. 2.0 DISCUS $10N The present surveillance interval for the EDGs of 18 months was originally predicated on a 12-month fuel cycle followed by a refueling outage of about 2 to 3 months. Since Specification 4.0.2.a permits a 2b percent extension for this surveillance, the maximum interval allowed by the TSs is 22.5 months.
While this maximum interval provides sufficient. time for a problem-free fuel cycle and subsequent problem-free refueling outage, it leaves very little margin in the event of either an extended shutdown during a fuel cycle or an extended refueling outage af ter the fuel cycle was extended to about 18 months.
Since the surveillance requirement in TS 4.8.1.1.2.d.1 for the EDGs cannot be performed within the 72-hour perion permitted by the applicable Limiting condition of Operation (LCO), the required EDG surveillance must be performed during an extendea shutdown. The most appropriate opportunity for the required surveillance is during a refueling outage.
However, the present maximum permitteo surveillance interval of 22.5 months may not allow this if any problems occur during a fuel cycle or the subsequent refueling outage as discussed above. Accordingly, the requested extension is intended to introduce flexibility into the scheduling of the EDG surveillance requirements thereby avoiding an extended shutdown during a fuel cycle.
The modification to Specification 4.0.2 in Amendment No.140 to the Davis-Besse TS cited above removed the provision that limited the combined time interval for three consecutive surveillances to less than 3,25 times the specified l
interval. This change does not affect the amendment request being considered in this evaluation.
3.0 EVALUATION The principal safety-related concern associated with the arososed extension of the surveillance interval is whether the reliability of tie EDGs will be adversely affected by the increase in the interval from a maximum of 22.5 months to a maximum of 30 months. The normal mode of operation for an EDG is to be operable with a periodic test run about every 31 days, in accordance with Specification 4.8.1.1.2.a.
Accordingly, each EDG will have at most an additional seven load tests conducted per Specification 4.8.1.1.2.a.4 which are attributable to this proposeo increase in the surveillence interval. Since the load tests are condccted for about 1 to 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br />, each EOG will be suoject to a maximum additional running time of about 14 hours1.62037e-4 days <br />0.00389 hours <br />2.314815e-5 weeks <br />5.327e-6 months <br />. All but one of these additional loaa tests will be preheated, prelubed starts since only one fast, cold (i.e., ambient temperature) load test is required every 6 months in accordance with Specification 4.8.1.1.2.c.
Operating experience with EDGs demonstrates that the preheated, prelubed starts of an EDG and the subsequent runs at power introduce negligible wear on the internal components of the diesel. One of the main causes of wear on the internal diesel components of the EDGs is attributable to cold fast starts (i.e.,acceleratingto900revolutionsperminutewithin10 seconds).
)
i I
f r Since the proposed increase in surveillance interval will add at most one additional cold fast start to each EDG, there will be relatively little additional wear on the diesel internal components and therefore, there will be a negligible effect on the reliability of the EDGs attributable to the proposed amendment.
Nevertheless the licensee has proposed to institute a performance trending of sevensetsofselectedEDGparemeters. These particular parameter sets are listed on pages 3 and 4 in the Morrison-Knudsen Report No. 6993-2. The data which will be trended by the licensee will be primarily compiled from the monthly EDG load tests required by Specifications 4.8.1.1.2.a and 4.8.1.1.2.c end include such items as the diesel cylinder exhaust temperatures, the diesel crankcase pressure readings, the generator temperature, power output, voltage and frequency.
A monthly diesel lube oil analysis will also be performed and trended; about 20 different lube oil characteristics and potential lube oil cnntaminants will be monitored. This monitoring will alert the licensee to a number of potential diesel engine component problems.
For example, a rapid increase in-lead concentration in the lube oil or a leed concentr6 tion greater than 75 parts per million would be indicative of bearing distress. Whilean EDG monitoring propram cannot provide absolute assurance of reliebility, major problem areas such as excessive bearing wear or water leaks which could contribute to a decrease in EDG reliability, will be detected. The net effect of this performance trending will be to provide 3ssurance that the limited ancunt of additional operating time and the potential for one additional cold fast start for each EDG do not degrade reliability.
As a turther effort to increase the reliebility of the EDGs, certain of the i
surveillance requirements (about 20 percent) such es filter changes on the diesel will be required to be performed more frequertly.
As an example, these preventative maintenance steps will be performed annually rather than at the 18-month surveillance interval. Considering that the present TSs permit these preventative maintenance measures to be taken at e maximum of 22.5 months, this is e significent improvement.
In support of its proposed change, the licensee cites in its submittal dated l
June 12, 1989, the excellent reliability of both of its two EDGs.
Specif-l itally, EDG 1-1 had only one failure to start in its 1est 100 starts and there were no f ailures to start for EDG 1-2 in its last 100 starts as of the date of l
this submittal. This yields a combined averace reliability of 0.995 per demand j
which exceeds the industry average for EDG reiiability of 0.98 per demand cited in the staff's Generic Letter 84-15.
The licensee also cites its recent experience with operating both EDGs for about 27 months between surveillance inspections as permitted by Amendment No.
105 to the Davis-Besse license.
The EDG surveillance inspection on both EDGs after 27 months showed no indications of unusual wear of the diesel internal components. While this is not a sufficient basis in itself to support the requested chance, it does support the licensee's assertion that an extra few months of EDG operation do not reduce the reliability of the EDGs as evidenced by the f act that there were no f ailures to start for either EDG in the pest 50 starts as of the date of its submittal.
I,.
.. The manuf acturer, Morrison-Knudsen, has reviewed and approved the licensee's proposal for extending the surveillance interval for certain portions of the LDG preventative maintenance program as documented in its Report No. 6993-2.
This approval is based on both the performance program trending which will be conducted by the licensee and on its own field service experience with diesels and on its engineering judgement.
The staff agrees with the licensee and the vendor of the EDGs that there is reasonable assurance that the proposed increase in the surveillance interval for certain specified parts of the preventative maintenance program will not adversely affect the reliability of the Davis-Besse EDGs based on: (1)the
)erformance trending of certain EDG performances parameters; (2) the present 11gh reliability of the EDGs; (3) the experience and judgement of Morrison-Knudsen as it relates to the preventative maintenance program; and (4) the increased frequency of certain other preventative maintenance measures. Based on these considerations, the staft concludes that the proposed increase in the EDG surveillance interval to a maximum of 30 months is acceptable; the 25 percent extension allowed by TS 4.0.2 will not apply. Accordingly, the deletion of the present specification 4.8.1.1.2.d.1 and the addition of Specification 4.8.1.1.2.e including its associated footnote is acceptable.
4.0 ENVIRONMENIAL CONSIDERATION This amendment involves a change to a requirement with respect to the instal-lation or use of a facility component located within the restricted area as defined in 10 CFR Part 20 or a change to a surveillance requ1rement. 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 comission has previously issued a proposed finding that this amendment involves no significant hazards consideration and there has been no public comment on such finding. Accord-ingly, this amendment meets the eligibility criteria for categorical exclusion set forth in 10 CFR 51.22(c)(9).
Pursuantto10CFR51.22(b)noenvironmental impact statement or environmental assessment need be prepared in connection with the issuance of the amendment.
5.0 CONCLUSION
The staff has concluded, based on the considerations discussed above, that:
(1) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the )roposed manner, and (2) such activities will be conducted in compliance with tie Commission's regulations, and the issuance of this amendment will not be inimical to the common defense and security or to the health and safety of the public.
Principal Contributor:
M.D. Lynch Dated: December 22, 1989
"