ML18046A769

Application for Amend to License DPR-20,changing Tech Spec 4.14 Re Steam Generator Insp Program.Summary Comparison of Current & Proposed Tech Spec Requirements Encl

ML18046A769
Person / Time
Site:	Palisades
Issue date:	07/02/1981
From:	Reynolds J CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.)
To:
Shared Package
ML18046A766	List: ML18046A765 ML18046A769
References
NUDOCS 8107070235
Download: ML18046A769 (9)

Text

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.,. (.. .e CONSUMERS POWER COMPANY Docket 50-255 Request for Change to the Technical Specifications License DPR-20 For the reasons hereinafter set forth, it is requested that the Technical Specifications contained in the Provisional Operating License DPR-20, Docket 50-255, issued to Consumers Power Company on October 16, 1972, for the Palisades Plant be changed as described in Section I below:

I. Changes Change Section 4.14 in its entirety to read as follows:

"4 .14 AUGMENTED INSERVICE INSPECTION PROGRAM FOR STEAM GENERATORS Applicability Applies to the tubes within both steam generators.

Objective To. provide assurance of continued integrity of the steam generator tubes over their service lifetime.

Specification

4. 14. 1 General Inspections will be made at a frequency of not less than 12 nor more than 24 calendar months after the previous inspection.

For the purpose of this Technical Specifications, "Tubes" refers to that portion of the steam generator U-tube from the point of entry on the hot leg side completely around the U-bend to the top support of the cold leg, or from the point of entry on the cold leg side to the top support of the cold leg.

If inspection of unplugged tubes with ET indications of greater than or equal to 30% (which are obstructed by ET and repair equipment) leads to significant added personnel radiation exposure, alternate tubes may be selected for examination. In any event, unplugged tubes with ET indications greater than or equal to 30% will be inspected within three consecutive inspections.

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2 "4.14.2 Inspection Tubes requiring ET inspection for flaw surveillance are divided into three categories as follows:

Category A - This inspection sample .consists of all tubes which contain ET indications greater.than or equal to 45%

in either of the previous two inspections.

Category B - This inspection sample consists of a percentage of tubes containing ET indications greater than oi equal to 30% and less than 45% in either of the previous two inspections and do not meet the requirements of Category A.

Category C - This inspection sample consists of a random sample of 2% of the unplugged tubes .in the hot leg and 1%

of the unplugged tubes in the cold leg in each steam generator. The tuoes selected to fulfill the Category C examinations shall contain ET indications less than 30% in both the previous two inspections.

In addition, all previously installed sleeves shall be inspected or plugged during each steam generator tube inspection.

Inspection methods shall be qualified for detecting and sizing flaws in all. unblocked tube lengths chosen for inspection. Table 4.14.1 summarizes the inspection populations and the applicable inspection method.

TABLE 4.14.1 Inspection Plan and ET Techniques Inspection Sample Inspection Technique Technique A Technique B (Equivalent to the Standard Qualified for determining

.540" dia probe 400 KHz flaw size in the presence single frequency technique.) of denting in which Tech-nique A's results are uninterpretable.

Category A 100% of Inspection Sample Those tubes in this sample

(~ 45%) in which Technique A pro-duces uninterpretable results.

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3 Inspection Sample Inspection Technique Technique A Technique B "Category B 33% of inspection sample. Those tubes in this sample

(~ 30% and < 45%) Tubes shall be selected such in which the ET results of that a similar percentage of Technique A are uninter-tubes* not previously pretable.

inspected shall be required until 100% of the Category B sample has been inspected.

Category C Random sample consisting of

(< 30%) 2% of the hot leg tubes and 1% of the cold leg tubes.

NOTE: Technique B may be used to fulfill Technique. *A requirements provided that all Technique A requirements are met.

4.14.3 Additional Inspection If the mean wastage increases over the period since the previous steam generator inspection is greater than 2%,

100% of the tubes in Category B above shall be examined.

4.14.4 Repair Criteria A tube shall require repair when inspection reveals that:

(1) Tube degradation exceeds 58% of the tube wall for indications other than multiple ET indications. If the mean wastage increases over the period since the previous steam generator inspection is less than +1%

(essentially no wastage), the operating allowance listed above shall be applicable. If the mean wastage increase is greater than or equal to +1%, the NRC shall approve new operating allowance.

(2) Tube degradation exceeds 35% of the tube wall for multiple ET indications.

(3) Passage of a 0.540" ET probe is prohibited.

Acceptable repair techniques for (1) and (2) above are plugging the affected tube or sleeving the tube region

• containing the defect. For tubes containing sleeves, the acceptance criteria in Table 4.14.2 shall apply.

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4 "4.14.5 Sleeving Sleeves shall be installed such that, considering the axial location tolerances, swagging does not take place in an area of known degradation. A baseline ET inspection of all newly installed sleeves shall be performed.

4.14.6 Reporting A steam generator inspection report shall be submitted to the NRG within 90 days of completion of the inspection and.

any required repairs.

Basis Consumers Power has concluded that the change from coordinated phosphate to volatile chemistry control for the secondary side of the steam gener-ators has reduced the previous corrosion rate to essentially zero.

Palisades has not observed any tube leakage since June 1974. Further-more, mean wastage increase.has been essentially zero since since February 1976. The continuing ispection program provides for verifying that the co~rosion has been arrested.

The inspection program is also consistent with current industry practices and includes.appropriate measures to identify additional degradation of the Palisades steam generators.

Calculations have been performed to demonstrate that a tube uniformly thinned to 36% of its original nominal wall thickness (64% degradation) can withstand a differential pressure of 1380 psid. Likewise, a sleeved tube can withstand the same differential pressure when the limits in Table 4.14.2 are observed. Combustion Engineering, Inc Report

1. CEN-59(P) "Palisades Steam Generator Tube Repair by Sleeving," dated August 26, 1977, contains the analytical and test results of tube sleeving.

In dented regions when the presence of a tube support plate tends to cause interference in the eddy current signals, the standard ET inspec-tion technique will not be able to detect flaws embedded in these regions. However, there are several advanced inspection probes under development which have been s.hown to be effective in detecting flaws by screening out the interference signals caused by the presence of the tube support plates or dents.

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"TABLE 4.14.2 Maximum Allowable Degradation Location Maximum Allowable Degradation(S)

Unsleeved Sections Degradation = 64%

Sleeved Section Region 1 ( l) Sleeve degradation = 34% and tube degradation exceeding the maximum allowable degradation for an unsleeved section. C4 )

Region 2( 2 ) Either (a) sleeve degradation = 25% when tube de-gradation in Region 1 exceeds the maximum allowable degradation for an unsleeved section; or (b) tube degradation to Region 2 equal to the maximum

• allowable degradation for an unsleeved tube. < ) 4 Region 3C 3 ) Tube degradation equal to the maximum allowable degradation for an unsleeved section.

Footnotes:

(l)The undeformed region of the tube/sleeve assembly containing the original imperfection requiring sleeving.

(Z)The region containing the expansion joint. Specifically, the region of the tube/sleeve assembly bounded by lines approximately 1/4 inch and 2 inches inboard from the sleeve ends.

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( )The region of the tube/sleeve assembly containing approximately 1/4 inch of each end of the assembly.

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• C )Degradation occurring in the parent tube at any location in a region and degradation occurring in the sleeve at any location in the same region that exceeds the applicable maximum allowable degradation will require tube plugging.

(S)Subtracted from these Maximum Allowable Degradation values shall be an approved operating_ allowance of 6%."

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6 II. Discussion The Technical Specifications revision is proposed to reflect the unchanging degradation status of the steam generators and improved inspection capabilities. The two major areas involved in this change request are:

A. Modify eddy current test (ET) tube sampling requirements to reflect current steam generator conditions.

B. Establish a standard operating allowance and repair criteria.

A summary of current and proposed Technical Specifications requirements is presented in Table 1. As shown in Table 1, the maximum period for reinspection of unplugged tubes containing ET indications greater thazi, or equal to 30% but less than 45% tube wall degradation would be increased from one to three inspection intervals. Tube sampling would be selected so that 100% of the total sample would be examined within three inspections by a technique qualified for detecting and sizing flaws in the presence of dents. Iri contrast to previous inspections, valid flaw readings were frequently not obtained for indications in this category due to the presence of denting.

Inspection and sampling requirements for unplugged ET indications equal to or greater than 45~~ are unchanged.

The operating allowance is set at 6% by the proposed Technical Specifications, which correlates to a plugging or repair criteria of 58%

tube wall degradation for ET indications as was used in previous inspections (maximum allowable tube degradation remains unchanged at 35~~

for multiple ET indications). No changes are proposed for sleeved tube inspection sampling or acceptance criteria as shown in Table 4.14.2.

NOTE: An editorial change has been made to Footnote 5 of Table 4.14.2.

The number of tubes (based on the latest inspection results) which require inspection by various ET techniques under current and proposed Technical Specifications requirements are shown in Table 2. As indicated, the p:r;oposed Technical Specifications should result in a significant increase in the number and percentage of valid ET readings in the greater than or equal to 30~~ but less than 45% category. The increase in valid ET readings would be obtained from interpretable inspections of dented intersections achieved by utilization of multifrequency ET equipment and process developments, which were not available durin~ previous inspections.

Personnel radiation exposure and time required for ET of the Palisades steam generators is estimated to be reduced by approximately 20~~ by the proposed Technical Specifications and ET technique developments.

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7 As concluded in the reports of ET inspections of the Palisades steam generators in 1978 and 1979, adherence to strict secondary water purity limits and the policy of keeping the secondary side in wet lay-up when the steam generators are not operating has essentially stopped the tube corrosion previously experienced. Therefore, we believe the requested Technical Specifications changes are in accordance with ALARA concepts and also provide the information required to assess the unchanging conditions of the Palisades steam generator tubing.

III. Conclusion Based on the foregoing, both the Palisades Plant Review Committee and the Safety and Audit Review Board have reviewed these changes and find them acceptable.

CONSUMERS POWER COMPANY By ynolds, Executive Vice Energy Supply Sworn and subscribed to before me this 2nd day of July 1981.

Jackson County, Michigan My commission expires December 14, 1983.

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8 TABLE 1 Summary Comparison of Current and Proposed Tech Spec Requirements (Section 4.14)

Requirement Current Tech Spec Proposed Tech Spec ET Inspection Frequency Every 12-24 months Every 12-24 months Maximum period for reinspection One inspection Three inspections of unplugged tubes with ET (1Wo is allowed if indications greater than significant in-or equal to 30% crease in radiation exposure results)

Inspection sample for unplugged 100~~ 100%

tubes containing ET indications equal to or greater than 45~~ using ET techniques qualified for p.roducing interpretable results Inspection sample for unplugged 100; 33-1/3%

tubes with ET indications great.er NOTE: Chosen so than or equal to. 30% but l.ess than 100% tubes inspec-45% ted within three inspections Random sample using pull-through 2% hot leg 2% hot leg technique for tubes with ET 1% cold leg 1% cold leg indication less than 30%

Operating allowance for multiple 35%

ET indications Operating allowance for ET 6% for inspection 6%

indications other than multiple after 1976 ET indications 10% for tubes last inspected in 1976 20% for tubes last inspected in 1975 Plugging criteria for denting Failure to pass Failure to pass 0.540" probe 0.540" probe Interval between completion of 30 days 90 days inspection and repair and sub-mission of inspection report NOTE: Sleeve inspection frequency and acceptance criteria unchanged.

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• 9 TABLE 2 Effect on Tubes To Be Inspected of Revised Technical Specifications (Based on Latest Inspection Results From 1979)

Inspection Sample Current Tech Spec Proposed Tech Spec SG-A SG-B SG-A SG-B Number of unplugged tubes/ 283/296 214/247 283/296 214/247 indications with previous ET results equal to or greater than 45% to be inspected Number/percent of unplugged 296/100~~ 247/100% 296/100% 247/100%

ET indications equal to or greater than 45% which (Using previous ET (Using new ET are expected to be given techniques) techniques) interpretable inspection Number of unplugged tubes/ 987/1601 720/1251 329/534 240/417 indications with ET results equal to or greater than (1/3 (1/3 30% but less than 45% to sample) sample) be inspected Number/percent of unplugged 1102/68.8%. 716/57.2% *534/100% *417/100%

ET indications equal to or greater than 30% but less (Using previous ET (Using new techniques) than 45% which are expected techniques) to be given an interpretable *1601 over *1251 over inspection 3 inspec- *3 inspec-tions tions Tubes included in random 132 hot leg 136 hot leg 132 hot leg 136 hot leg sample 53 cold leg 69 cold leg 53 cold leg 69 cold leg nu0481-0220c-43