ML20082Q998
| ML20082Q998 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 09/10/1991 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20082Q994 | List: |
| References | |
| GL-90-09, GL-90-9, NUDOCS 9109130168 | |
| Download: ML20082Q998 (2) | |
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%... *,p ENCLOSURE 3 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENOMENT f40.153 TO FACILITY OPERATING LICENSE NO. OPR-77 AND_ AMENDMENT NO.143 TO FACILITY OPERATING LICENSE NO. OPR-79 TENNESSEE VALLEY AUTHORITY SEQUOYAH NUCLEAR PLANT, Uh1TS 1 AND 2 DOCKET NOS. 50-3P7 AND 50-3?8
1.0 INTRODUCTION
By letter dated May 24, 1991, the Ternessee Valley Authority (the licensee) submitted a request for chances to the Sequoyah Nuclear plan's Units 1 and 2 TechnicalSpecifications(TS).
The requested changes would permit the licensee to revise its TS-required visual examination programs for safety-related snubbers in accordance with the guidelines set forth in Generic Letter 90-09,
" Alternative Requirements for Snubber Visual inspection Intervals and Corrective Action," of December 11, 1990.
2.0 EVALUATION The present snubber visual examination schedule in the TS is based on the number of inoperable snubbers identified in the previous visual examination.
The schedule is determined only by an absolute number of inoperable snubbers discovered during the previous visual examination irrespective of the size of the snubber population.
Therefore, licensees with a large snubber population find the schedule excessively restrictive.
Generic Letter 90-09 provides an acceptable alternative visual examination schedule that permits licensees to perform visual examinations and corrective actions during refueling outages without reducing the confidence level provided by the existing _ surveil'ance requirements. The basic examination interval is the normal fuel cycle up to 24 months. This interval may be extended to as long as twice the fuel cycle or reduced to as small as two-thirds of the fuel cycle depending on the number of unacceptable snubbers found during the visual examination. The examination interval may vary by +25 percent to coincide with the actual outage.
If one or more snubbers are found inoperable during a visual examination, the present TS Limiting Conditions for Operation (LCO) require the licensee to restore or replace the inoperable snubber (s) to operable status within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />, or declare the att9ched system inoperable and follow the appropriate action statement ior that system. This LCO will remain in the TS.
- However, this proposed amendnent would allow the permissible number of inoperable snubber (s), and the subsequent visual ex eination interval, to be determined 9109130168 Y10910 PDR-ADOCK 05000327 P
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using the new visual examination schedule (proposed Table 4.7.9.1).
As noted in the guidance of Generic Letter 90-09 for this line item TS improvement, certain corrective actions may have to be performed depending on the number of inoperable snubbers found. /11 requirements for corrective actions and evalua-tions associated with the use of the visual examination schedule, as stated in Footnotes 1 through 7 (Table 1 of Generic Letter 90-09), is proposed to be included in the TS. Therefore, we find these proposed changes acceptable.
The licensee also proposed to delete the 50 percent drag force increment as an acceptance limit for functional testing.
This requirement was established to trend the mechanical snubber's performance, not to cetermire operability. In the past, the recommended limit for the change in mechanical snubber drag force was 0.5 percent of the snubber's rated load, and the 50 percent increment of drag force between two consecutive tests was believed to be the maximum dete-rioration rate that can be tolerated by mechanical snubbers.
However, the manufacturer has periodically revised its recommended drag acceptance value.
The latest reconmended cumulative limit is 3 percent of the snubber's rated load with no restriction on deterioration rate instead of the originally recommended 0.5 percent coupled with the 50 percent drag force increment.
In i
addition, monitoring to determine if a deteriorating trend is developing between surveillance inspections it required by Surveillance Requirement 4.7.9.i.
This specification requires the determination of the maximum service life using engineering information. Also, it specifies that an increase in the drag force greater than 50 percent from the previous test is an indicatiun of impending failures of the snubber which shall be evaluated. As a result, the use of 50 percent as the deterioration rate limit required by the TS :s not appropriate.
Therefore, deletion 0f the 50 parcent change as a limit for the drag force is acceptable.
The requested revision of the bases for the TS is related to the itcensee's internal approval procedure of adding and deleting snubbers te the service list, and revises the number of snubbers to reflect the present population level. We find these changes to be acceptable, in summary, the licensee has proposed changes to TS 3/4.7.9 t5at are consistcnt with the guidance provided in Generic Letter 90-09 for the replacenent of the snubber visual examination schedule with Table 1 (including Footnotes 1 through
- 7) of Generic Letter 90-09.
The staff has reviewed the proposed amendments and finds that the proposed changes are acceptable.
3.0 STATE CONSULTATION
In accordance with the Commission's regulations, the Tennessee State official l
was notified of the prnposed issuance of the amendment. The State official had l
no comments.
4.0 ENVIRONMENTAL CONSIDERATION
l The amendment changes a requirement with respect to installation or use of a facility component located within the restricted area as defined in l
10 CFR Part 20. The NRC staff has determined that the amendment involves no l
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