ML19331E166
| ML19331E166 | |
| Person / Time | |
|---|---|
| Site: | Rancho Seco |
| Issue date: | 08/23/1977 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML19331E165 | List: |
| References | |
| NUDOCS 8009080672 | |
| Download: ML19331E166 (5) | |
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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION SUPPORTING AMENDMENT NO.13 TO FACILITY OPERATING LICENSE NO. DPR-54 SACRAMENTO MUNICIPAL UTILITY DISTRICT RATICHO SECO NUCLEAR GENERATING STATION DOCKET NO. 50-312 Introduction By letter dated October 9,1974, the Sacramento Municipal Utility District (SMUD) agreed to perform an eddy currert inspection of steam generator tubes during the first refueling outage of Rancho Seco Nuclear Generating Station. By letter dated Septenber 21, 1976, we forwarded reconinended revised techiiical specifications based upon revised Regulatory Guide 1.83, "In".ervice Inspection of Pressurized Water Reactor Steam Generator Tubes." SMUD answered this request by letters dated Noventer 26, 1975 and June 21,1977, which forwarded revised technical specifications. The proposed change would add technical specification provisions for steam generator tube inspection to be consistent with the guidance containad in Regulatory Guide 1.83, Revision 1, dated July 1975.
Modifications to the proposed amendment were necessary to assure compliance with our regulatory position. These modifications were discussed with and agreed to by the SMUD staff.
Evaluation Structures, systems, and components important to safety of a nuclear power plant are designed, fabricated, constructed, and tested so as to provide reasonable assurance that the facility can be operated without undue risk to the tealth and safety of the public. To continuously maintain such assurance, General Design Crit?rion 32 requires that components which are part of the reactor coolant pressure boundary be designed to pennit periodic inspection and testing of important areas and features to assess their structural and leaktight integrity. The steam generator tubing is part of the reactor coolant system pressure boundary and is an important part of a major barrier against fission product release to the environment.
It also acts as a barrier against 8009080 h Q
steam release to the containment in the event of a loss-of-co For this accident (LOCA).
free of cracks, perforations, and general deterioration.
d reason, a program of periodic inservice inspection is being establishe to assure the continued integrity of the steam generator tubes over the service life of the piant.
Generally, the major elements of the proposed steam generator tube (a) sample insp(ction program for Ranche Seco consist of specified:
selection, (b)(examination methods, (c) inspection int Each of these major elements e) reporting requirements.
criteria, and of the program is separately evaluated below.
Sample Selection (a)
The proposed samoling scheme is generally patterned after Regula Guide 1.83, Revision 1, " Inservice Inspection of Pressurized Water Reactor Steam Generator Tut.es".
from Regulatory Guide 1.83 that we require to improve the program and/or reduce the potential radiation exposure of personnel that The principal devictions from must perform the inspectinns.
Regulatory Guide 1.83 supplementary sampling requirements are evaluated below:
Regulatory Position C.5.a, " Supplementary Sampling Require recommends that if the eddy current inspection results during (i) an inservice inspection indicate any tubes with previously undetected imperfections of 20% or greater depth, additional In other steam generators, if any, should be inspected.
words, because of a single tube in one steam generator with previously undetected imperfection of 20% or gre Although the detection in the plant should be inspected.
of any defect warrants further inspection to determine the extent of degradation in the steam generators, we the extent of any further degradation in the steam generator If the expanded inspection indicates more Y
under inspection.
extens,ive defect conditions, then expansion to the other g
steam generator is requirede This approach will p of successive. steps, while tending to minimize the exposure of inspection personnel resulting from initial positioningThis inspection
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of inspection equipment in a steam generator.
approach 1s appropriate for this facility in which sy to perfern in a similar manner.
Regulatory Guide 1.83, Revision 1, requires additional inspsetions if the initial inspection results indicate (ii) that more than 10% of the inspected tubes have detectable wall penetration of greater than 20% or that one or more The additional inspections require a complete tube inspection of an additional 3% and if required a third in-The progr limit.
spection of 6% of the tubes. Rancho Seco Technical Specifications r doubling the number of tubes inspected in the first sample.
Again if more than 10% of the tubes show a detectable pene-tration greater than 20% or 1" are defective tubes l
In the first sample, sampling is to in the second sample.
concentrate on areas of the tube array where prior inspections or experience have indicated potential problems, and full For a length traverse of each inspected tube is required.
J second or third sample, if required, the inspection may con-centrate on areas of the tube array and portions of the tube in which the first sample or the second sample indicated potential problems.
Based on the considerations discussed above, we have concluded that J
i the sample selection scheme is acceptable.
(b) Examination Method The proposed examination methods include nondestructive examination The specified methods are capable of by addy current testing. locating and identifying stress corrosion cracks a thinning from chemical wastage, mechanical damage or other causes.
Based on our review of these methods, and experience gained using these methods by the industry, we have concluded that the examination methods are acceptable.
(c)
Inspection Intervals The proposed inspection intervals are compatible with tho SMUD has proposed to perform the fjrst inservice inspection at the first refueling outage, which will be more than 24 calendar l
We conclude that the in-months after initial criticality.
spection intervals are acceptable.
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y Acceptance Criteria f
(d)
The principal parameter used to determine whether any one ste d
generator tube is acceptable for continued service is the The imperfection depth.
is acceptable, a tube " plugging ifmit" is established.
" plugging limit" is defined in the Technical Specifications as d
the imperfection depth beyond which the tube m For Rancho Seco the " plugging next scheduled inspection. limit" is 40% of the nominal tube wall th SMUD and the NRC staff have mutually o) reed upon this 40%
l plugging limit in the definitions section of the TechnicaAll to the present time exhibited any wastage co Specifications.
protection against wastage corrosion tube degradation.
Based on our review, the acceptance criterit are satisfactory, Reporting Requirements ort (e) Regulatory Guide 1.83, Revision 1, requires a licensee t l of the to the Commission and to await resolution a ed the i
In the limits specified in the Guide.
sampling and more frequent inspection may be required.
ht proposed Technical Specifications, it is clearly stated i
to additional inspection SMUD must perform without report ng f tubes the NRC and requires (1) a prempt report ator j
tion in the tube. inspection, (2) a complete report on the inspec s
next annual operating report, and (3) in the i
of the NRC must be made together with a written followup.
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. It is our position that the reporting requirements are reasonable and will facilitate reporting of pertinent information without unnecessarily increasing plant downtime. Therefore, they are-acceptable.
In summary, we have concluded that the proposed steam generator tube inservice inspection program will provide added assurance of the continued integrity of the steam generator tubes, and thus is acceptable.
Environmental Considerations We haYe determined that the amendment does not authorize a change in effluent types or total amounts nor an increase in power level and will not result in any significant environmental impact.
Having made this determinstion, we have further concluded that the amendment involves an action which is insignificant from the standpoint of environmental impact and pursuant to 10 CFR 551.5(d)(4), that an environmental impact statement or negative declaration and environmental impact appraisal need not be prepared in connection with the issuance of this amendment.
Conclusion We have concluded, based on the considerations discussed above, that:
(1) because the amendment does not involve a significant increase in the probability or consequences of accidents previously considered and does not involve a significant decrease in a safety margin, the amendment does not involve a significant hazards consideration, (2) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner, and (3) such activities will be conducted in compliance with the Commtssion's regulations and the issuance of this amendment will not be inimical to the common dafense and security or to the health and safety of the public.
Date: August 23,-1977 4
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