ML18043A865
| ML18043A865 | |
| Person / Time | |
|---|---|
| Site: | Palisades  |
| Issue date: | 07/26/1979 |
| From: | Dewitt R CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.) |
| To: | |
| Shared Package | |
| ML18043A864 | List: |
| References | |
| NUDOCS 7907310308 | |
| Download: ML18043A865 (6) | |
Text
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CONSUMERS POWER COMPANY Docket 50-255 Request for Change to the Techncal Specifications License DPR-20 1
For the reasons hereinafter.set forth, it is requested that the Technical Speci-fications contained in 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 II.
A.
Replace present Table 4.14.1 with the following Table 4.14.1:
B.
ECT Indications Other Than Multiple ECT Indications 6% + MWI*
"TABLE 4.14.1 Operating Allowances Multiple ECT Indications 35%
- Mean Wastage Increase (MWI) over the period since the last steam generator inspection if~+ 1%."
Delete.the words "NRC approved" from the first sentence of Section 4.14.3.
- c.
Renumber Table 4-14 on Page 4-69 to 4.14'. 2.
D.
Chang~ the first paragraph of the Basis for Section 4.14 to read:
"Consumers Power has concluded that the change from coordinated phosphate to volatile chemistry control for the secondary side of the steam generators has reduced-. the* previous"* corrosion *rate. to essentially zero.
This reduction in corrosion rate has* also been demonstrated by other ut-ilities making the same chemistry control conversion.
Palisades has observed no tube leakage since June 1974.
Furthermore, mean wastage increase has-been. essentially zero since February 1976."
E.
Delete the words "as approved by the NRC" from Footnote 5 of Table 4.14.2.
Discussion Consumers Power has concluded that the change from coordinated phosphate to volatile chemistry control has arrested previous corrosion.
This has also been demonstrated by other utilities making the same chemistry control
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conversion.
Since June 1974 no tubes have leaked, and since February 1976 mean wastage increase has been essentially zero which further confirms the satisfactory performance of the steam generators.
The operating allowance for 1978 of 6% is considered applicable tQ all past and future data as long as the mean wastage increase for the previous cycle is less than 1%.
If a mean wastage increase equal. to or greater than 1%
is observed, the operating allowance for the next cycle shall be the sum of the actual mean wastage increase over the previous cycle plus the 6%
allowance for ECT uncertainty.
It is important to note that in 1978 the.sleeving and plugging which re-sulted from the application of the* repair criteria was dependent solely on the 1978 ECT data.
Therefore, it is not necessary to list separate operating allowances to be applied to previous years' inspection results.
Current inspection requirements. provide assurance that any tubes approaching the Maximum Allowable Degradation of 64% and any changes in mean wastage *in-crease will be identified.
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 JE/6 ~d RB DeWitt,_Vice President Nuclear Operations Sworn and subscribed to before me this 26th day of July 1979.
~~~p;~~
Dorothy HBartkus, Notary Public Jackson County, Michigan My commission e.xpires March 26, 1983.
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4.14.2 Inspection techniques, capable of detecting flaws in the presence of tube support plates, shall be used to inspect all accessible tube/tube support plate intersections where an EC.T..
indication was present during the last inspection which was greater than or equal to 45% but cannot be interpreted in the current inspection due* t'o the presence of dents.
- In addition, the following shall apply for areas which could not be inspected due to dents in the last inspection.
Additional intersections shall be selected for special examination to assure that all accessible previous ECT indications are
. inspected when their last recorded ECT reading plus the. appro-priate operating allowance from Table 4.14.1 exceeds the Maximum Allowable Degradation specified in Table 4.14.2, If such indications, regardless of accessibility, are not inspected, the repair criteria of 4.14.3 shall apply for sleeving or
- plugging.
4.14.3 When inspection reveals that the tube degradation plus an appropriate op_erating allowance (for future deg;adation) is greater than the maximum allowable degradation specified in Table 4.14. 2, the tube'* sha'll b*e* declared* to be defective and tube plugging or sleeving shall be performed.
In determining that a defect exists at a given tube location,
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indications from several ECT's may be averaged during a given inspection, but such averaging shall be based on not less than three ECT's.
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4.14.4 Operating allowances for future degradation are tabulated in Table 4.14.1.
4.14.5 Sleeves will be installed such that, considering the axial location tolerances, swaging does not take place in an area of known degrada-tion.
A base line ECT inspection of all newly installed sleeves shall be performed.
In addition, all previously installed sleeves shall be inspected or plugged during subsequent steam generator
- tube inspections.
Basis Consumers Power has concluded that the change from coordinated phosphate to volatile chemistry control for the secondary side of the steam generators has reduced the previous corrosion rate to essentially zero.
This reduction in corrosion rate has also been demonstrated by other utilities making the same chemistry control conver-sion.
Palisades has observed no tube leakage since June, 1974.
Furthermore, mean wastage increase has been essentially zero since February, 1976.
O,:ur inspection program is consistent with current industry practices and includes appropriate measures to identify additional degradation of the Palisades steam generators.
The operating allowance will be and the repair criteria has been developed based on comparative results between steam generator inspections with consideration given to defect type, location, past corrosion rate observed, etc.
Calculations have been performed to demonstrate that a tube uniformly thinned to 3'6%- or-* its; ori-ginal nomfha:l wB:ll thickness* ( 64%' degradation)* can' wi'thsta:nd-a:
differential pressure of-1380 psi.
Likewise, a sleeved tube can withstand. the same differential pressure when the limits in Table 4.14.2are observed.
Combustion Engineering, Inc Report No CEN-59(p) "Palisades Steam Generator Tube Repair by Sleeving,"' dated August 26\\ 1977', contains* -the*- analyti*cal and test results of tube sleeving.
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In dented regions when the presence of a tube support plate tends to cause* interference in the eddy current signals, the standard ECT inspection technique will not be able to detect flaws embedded in these regions.
However, there are several advanced inspection probes under *development which have been shown to be effective in detecting flaws by screening out the interference sfgnaJ.:s cause'd by the presence of the tube s*upport plates or dents.
ECT Indications Other Than Multiple ECT Indications 6% + MWI*
TABLE 4.14.1 Operating Allowances Multiple ECT Indications 35%
- Mean Wastage Increase (MWI) over the period since the last steam generator inspection if > + 1%.
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Locatton Unsleeved Sections Sleeved Section Region l(l)
Region 2( 2 )
Region 3( 3 )
Footnotes:
TABLE 4.14.2 Maximum Allowable Degradation Maximum Al*lowable Degradation ( 5)
Degradation = 64%
Sleeve degradation = 34% and tube degradation exceeding the maximum allowable degradation for an unsleeved section.(4)
Either (a) sleeve degradation = 25% when tube degradation in Region l 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)
Tube degradation equal to the maximum allowable degradation for an. unsleeved section.
(l)The undeformed region of the tube/sleeve assembly containing the original imperfection requiring sleeving.
(2 )The region containing the expansion joint: Specifically, the region of the. tube/ slee.Ve.. ass.embly bo.unded. by. lines.. approximately 1/4 inch and.
- 2. inches inbo.ard from the. sleeve ends..
( J)'The region o.f the tube/sleeve* ass.embly containing. approximately 1/4 inch of each end of* the assembly*.
(4 )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 vaiues shall be an,
appropriate allowance for future degradation as identified in 4.14.3.
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