ML20082N157
| ML20082N157 | |
| Person / Time | |
|---|---|
| Site: | Millstone  |
| Issue date: | 09/03/1991 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20082N154 | List: |
| References | |
| NUDOCS 9109090013 | |
| Download: ML20082N157 (4) | |
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,g SAFETY EVALUATION BY T}{E OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO. 62 TO FACILITY OPERATING LICENSE NO. NPF-49 NORTHEAST NUCLEAR ENERGY COMPANY, ET AL.
MILLSTONE NUCLEAR POWER STATION, UNIT NO. 3 DOCKET NO. 50-423 i
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1.0 INTRODUCTION
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By letter dated June 25, 1991 the Northeast Nuclear Energy Cocoany submitted a request for changes to the Millstone Nuclear Power Station, thit No. 3 Technical Specifications (TS). The prcposed amendment would resise the Millstone Unit 3 visual inspection surveillance requirementr. (Technical Specifications 4.7.10.a and 4.7.10.b) and acceptance criteria (Technical Specification 4.7.10.() associated with seismic sway arresters (snubbers).
l 2.0 EVALUATION By letter dated December 11, 1990, the NRC staff issued Generic Letter (GL) 90-09, " Alternative Requirements for Snubber Visual Inspection Intervals and l
Corrective Actions." Generic Letter 90-09 addresses TS which impose l
surveillance requiremer.ts for visual inspection of all safety-related snubbers.
A visual inspection is the observation of tne condition of installed snubbers to identify those that are damaged, degraded, or inoperable as caused by
-physical means, leakage, corrosion, or environment exposure. To verity that a snubber can operate within specific performance limits, the licensee performs funttional testing that typically involves removing the snubber and testing it l
on a specially-designed test stand.
Functional testing provides a 95 percent L
l confidence level that 90 percent to 100 percent of the snubbers operate within the specified acceptance limits.
The performance of visual examinations is a separate _ process that complements the functional testing program and provides i
additional confidence in snubber operability.
The TS specifies a schedule for snubber visual inspections that is based on the number of inoperable snubbers found during the previous visual inspection. The schedules for visual inspections and for the fi. tional testing assume that refueling intervals will not exceed 18 months, Because the current schedule for snubber visual inspections is based only on the number of inoperable snubbers found during the previous visual inspection, irrespective of the size of the snubber population, licensees having a large i
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--2 pumber of snubbers find that the visual inspection schedule is excessively res t ri ct ive. Some licensees have spent a significant amount of resources and have subjected plant personnel to unnecessary radiological exposure to comply with the visual examination requirements.
J To alleviate this situation, the NRC staff has developed an alternate schedule for. visual inspections that maintains the same confidence level as the existing schedule and generally will allow the licensee to perform visual inspections and corrective actions during plant outages.
Because this line-item TS improve-ment will reduce future occupational radiation exposure and is highly cost effective, the alternative inspection schedule is consistent with the Commission's policy statement on TS improvements.
An alternate method for determining the next interval for the visual inspection of snubbers is provided based upon the number of unacceptable snubbers found during the previous inspection, the total population or category size for each snubber type, and the previous inspection interval. A snubber is considered unacceptable if it fails to satisfy the acceptance-criteria of the visual inspection. Snubbers may be categorized, based upon their accessibility during power operation, as accessible or inaccessible.
These categories may be examined separately or jointly.
However, the licensee must make and document that decision before any inspection and shall us~e that decision as_ the basis upon which to determine the next inspection interval for
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the category.
-li a licensee's t review and evaluation cannot justify continued operation.
with an unacceptable snubber, the licensee shall declare the snubl :
inoperable and shall meet the applicable action requirements. To determine the next surveillance interval, the licensee may reclassify an unacceptable snubber as acceptable if it can be demonstrated that the snubber is operable in its as-found condition by the performance of a functional test and if it satisfies the.accep'.ance criteria for functional testing.
The next visual inspection interval may be twice, the same, or reduced by as much as two-thirds of the previous inspection interval.
This interval depends on the number of unacceptable snubbers found in proportion to the size of the population or category for each type of snubber included in the previous inspection. A table in the:TS replaces the existing TS requirements for
- determining the next visual inspection interval. The existing hillstone Unit 3 TS requirements establish inspection intervals of 18 months (the length of a nominal fuel cycle) or a fraction thereof based on the number of inoperable snubbers of each type for the previous inspection period.
- The alternttive TS allows inspection intervals to be compatible with a 24-month fuel cycle. Also, the interval may be increased to every other refueling outage for plants on a 24-month fuel cycle or up to 48 months for j
plants with other fuel cycles if few unacceptanle snubbers were found from the 9
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i previous inspection.
The TS establishes three limits for determining the next visual inspection interval corresponding to.the population or category size for a given type of snubber. The three limits are listed in Columns A, B, and C of_the TS Table for representative sizes of snubber. populations or-J categories. For a population or category that differs from the representative size provided, the values for the limits may be found by interpolation from the' limits provided in Columns A, B, and C for determining the next inspection interval. Where the limit for unacceptable snubbers in Columns A, B, or C is i.
determined by interpolation and includes a fractional value, the limit may be
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reduced to the next lower integer.
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The limits in columns A, B, and C of the TS Table are applied as follows to determine the next inspection interval.
If the number of unacceptable snubbers is less then or equal to the number in Column A, the next inspection i
interval may be twice the previous interval but not greater than 48 months, i
excluding the TS provisions to extend surveillance intervals.
If the number
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of unacceptable snubbers is greater than the number in Column A but less than or equal to the number in Column B, the next inspection interval shall be the same as the previous interval.
If the number of unacceptable snubbers is equal to or greater than the number in Column C, the next inspection interval t
shall be reduced to two-thirds of the previous interval. However, if the number of unacceptable snubbers is less than the number in Column C and greater than the number in Column B, the next inspection interval shall be i
reduced proportionally-by a factor that is one-third of the ratio of the j
dif ference between the number of unacceptable snubbers and the number in Column B to the difference between the numbers of Columns B and C.
e By letter dated June 25, 1991, the licensee responded to GL 90-09 by proposing to change the Millstone Unit 3 TS. The proposed TS would incorporate the alternate visual inspection schedult in TS Table 4.7-2, " Snubber Visual Inspection Interval." We have reviewed the licensee's proposed changes to the TS and conclude that they conformed tc the model TS contained in Enclosure B to GL 90-09.
Accordingly, the proposed changes to the TS are acceptable.
3.0 STATE CONSULTATION
In accordance with the Commission's regulations, the Connecticut State of ficial was notified of the proposed issuance-of the amendment.
The State official had no comments.
4.0 ENVIRONMENTAL CONSIDERATION
The amendment changes a requirement with respect to installation or use of a facility component located within the restricted area as defined in 10 CFR Part 20 and changes surveillance requirements. The NRC s ta f f has determined that the amendment involves no significant increase in the amounts, and no significant change in the types, of any ef fluents that may be released 4
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. occupational radiation expoture.
The Commission has previously issued a proposed finding that the amendment involves no significant hazards consideration, and there has been no public comment on such finding:(56 FR 33959). 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.
5.0 CONCLUSION
The Commission has concluded, based on the consideratious discussed above, that:
(1) there is reasonable assurance that the health and safety of the public vill 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:
D. ii. Jaffa Date: -September 3, 1991 l.
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