ML19254F184
| ML19254F184 | |
| Person / Time | |
|---|---|
| Site: | Palisades  |
| Issue date: | 10/15/1979 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML19254F181 | List: |
| References | |
| NUDOCS 7911070274 | |
| Download: ML19254F184 (4) | |
Text
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o UNITED STATES g
8 NUCLEAR REGULATORY COMMISSION o
WASHINGTON, D. C. 20655 g
%...../
SAFETY EVALUATIGi RY THE OFFICE OF NUCLEAR REACTOR REGULATION SUPPORTING AMENDMENT NO. 52 TO PROVISIONAL OPERATING LICENSE NO. DPR-20 CONSUMERS POWER COMPANY ALISADES PLANT DOCKET N0. 50-255
1.0 INTRODUCTION
By letter dated July 26, 1979, Consumers Power Company (the licensee) sutmitted proposed Technical Specification changes for the Palisades steam generator inservice inspection requirements.
As a result of discussions between the NRC staff and the licensee, a revised proposal was sutmitted by letter dated September 11, 1979.
The proposed chances would establish operating allowances for steam generator tube degradation based on the mean wastage increase during the previous operating cycle.
For mean degradation rates less than 1%, the current operating allowances will apply. For mean degradation rates greater than 1%, new operatina allowances will have to be approved by the NRC.
In addition, special inspection requirements for steam generator tubes which are obstructed by eddy current and repair equipment would be approved.
2.0 BACKGROUND
The Pelisades Technical Specifications require that the steam generator be inspected at a frequency not less than 12 nor more than 24 calendar months af ter the previous inspection. All unplugged tubes with an Eddy Current Test (EDT) indication of greater than or equal to 30% in either of the previous two inspections must be inspected in additior.
to a random sample of 2% of the hot leg tubes and 1% of the cold leg tu bt s.
Tube plugging or sleeving must be performed when the indicated tube degradation plus an NRC approved operating allowance and allowance for eddy current testing error exceeds the maximum allowable degradation specified in Table 4.14.2 of the Technical Specifications.
License Amendment 39, dated April 7,1978, revised the Technical Specifications for Palisades to include NRC approved operating allowances (in Table 4.14.1) applicable to tubes last it,spected through January 1978.
The specified 6% operating allowance for tubes inspected in January 1978 (without multiple ECT indications) accounts for statistical scatter and uncertainties in the eddy current testing technique.
No allowance was made for wastage increase during the next operating interval on the 7911070
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. basis of the January 1978 inspection results which indicated that the mean incremental ECT indication increase was essentially zero during the previous operating interval of approximately 20 months.
For tubes with multiple indications, a conservative 35% operating allowance is specified to ensure adequate safety margins in the event of coalescence of the degraded locations.
3.0 DISCUSSION The licensee has proposed that the specified operating allowances for tubes inspected in January 1978 be made applicable to future steam generator inspections (i.e., those inspections performed af ter January 1978) provided the mean wastage increase during the previous operating cycle is'less than 1%.
If a mean wastage increase equal to or greater th n 1% is observed, the operating allowance for the next 9
cycle will be determined by the licensee and approved by NRC.
The licensee has also proposed modified inspection requirements for steam generator tubes which are obscured by eddy current testing or sleeving equipment and redundant supports. The Palisades Technical Specifications currently require inspection of all tubes with an ECT indication of equal to or greater than 30% in either of the previous two inspection periods.
When these inspections involve the 20 to 30 tubes obscured by test and repair equipment, significant radiation exposure (approximately 6 to 9 Man-Rem) is incurred.
This added exposure results from multiple entries that must be made to the steam generator's access openings to perform a manual inspection.
The obscured tubes are located near the center stay in a region of low corrosion degradation.
The licensee proposes that if inspections of unpluqqed tubes with an ECT indication of greater than or equal to 30% leads to significant added radiation exposure, alternate tubes may be selected for inspection.
The affected (obstructed) tubes, however, would be inspected during the next steam generator inspection.
4.0 EVALUATION Operating Experience at the Palisades Plant indicates that the change from coordinated phosphate to all volatile secondary chemistry control has apparently arrested corrosion degradation.
No tube leaks have occurred since June 1974.
Results of the most recent steam generator inspection in January 1978 indicated that the incremental wastage increase since February 1976 has been essentially zero.
On the basis of zero mean wastage increase observed during the previous operating interval, the specified operating allowances for tubes inspected in January 1978 account for only the statistical scatter and uncertainties of the eddy current technique (plus additional allowance for multiple 1289 C"
ECT indications), with no allowance for mean wastage increase during the next operating interval.
These operating allowances were evaluated in our Safety Evaluation supporting Amendment 39 to the Operating License dated April 7,1978. We find that these allowances and the supporting Safety Evaluation renain equally valid for application to future steam generator inspections provided thr' the mean wastage increase during the previous operating interva? is found to be less than 1%, which we consider to be essentially zero. Therefore, the April 7,1978 Safety Evaluation Report is hereby incorporated into this Safety Evaluation by reference.
If a mean wastage increase equal to e <?reater than 1% is observed, the proposed changes would require the operating allowances to be submitted for NRC approval.
5.0
SUMMARY
We find that the proposed use of specified operating allowances in Table 4.14.1, and restriction governing their use, for future inspections (af ter January 1978) will provide reasonable assurance that tube degradation will not exceed the limits in Table 4.14.2 of the Technical Specifications and that any changes in mean wastage will be identified.
However, to facilitate the NRC in monitoring the condition in the steam generators it will be required that the licensee report statistical parameters including the distribution of degradation, the mean degradation rate, and the variation in degradation rate along with a description of how these parameters were detennined in their 30-day report of steam generator inspection results.
With regard to tubes obstructed by ECT and repair equipment, and which involve significant added radiation exposure to inspect, the licensee proposes that alternate tubes be inspected, and that the affected (obstructed) tubes be inspected during the next inspection.
We interpret " alternate tubes" to mean alternate tubes in the proximity of the affected tubes.
Considering that the affected tubes are located in a region of low corrosion degradation and that recent operating experience indicates that the rate of degradation is very small if not exactly zero, we find that the proposed changes would assure a reasonable level of surveillance of the affected tubes and are acceptable.
We note, however, that should an increase in mean wastage equal to or greater than 1% be observed in future inspections, the proposed operating allowances which would be subnitted for NRC approval should take into account the obstructed tubes which were not inspected.
Based on the above, we conclude that the proposed changes to the Palisades Technical Specifications regarding steam generator inspections are accepta ble.
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. 6.0 ENVIR0tNENTAL CONSIIT 1
'4e have detennined that the amendment does not involve a change in effluent types or total amounts not an increase in power level and will not result in any significant environmental impact.
Having made this determination, we have further concluded that the amendment involves an action which is insignificant frog the standpoint of envirormental impact and, pursuant to 10 CFR 551.5(d)(4), that an environmental impact statenent or negative declaration and environ-mental impact appraisal need not be prepared in connection with the issuance of this amendment.
7. ')
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 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.
Date:
October 15, 1979 1289 T
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