ML20149F179
| ML20149F179 | |
| Person / Time | |
|---|---|
| Site: | Zion File:ZionSolutions icon.png |
| Issue date: | 12/24/1987 |
| From: | COMMONWEALTH EDISON CO. |
| To: | |
| Shared Package | |
| ML20042D028 | List: |
| References | |
| 3985K, NUDOCS 8801140177 | |
| Download: ML20149F179 (10) | |
Text
o ATTAQMDf7_1 PROPOSED ZION APPENDIX A T_ECHNICAL SPEp_If,ICEION CHA@_ES TQ SECTION_1 3 .
BEACTOR COOLANT SYSTEM .
Pages Modified: 74f 74fl Page Added: 74f2 3985K P l
l, SURVEILLANCE REQUIREMENT LIMI11NG CONDITION FOR OPERATION
- 6. Pluqqinq or Regair Limit means the imperfection depth at or beyond which the tube shall be repaired (ie. sleeving) or removed from service by plugoing because it may become unserviceable prior to the next inspection and is > 40% of the nominal tube wall thickness.
Plugging Limit for sleeves means:
Combustion Engineering Sleeves ~ l
- a. for the area in the upper weld joint, anyl imperfection produced by degradation shall be plugged unless it can be clearly demonstrated by a qualified NDE technique that the imperfection is < 33% of the nominal wall thickness for I.D.
imperfections or < 40% thickness of the tube for 0.0. imperfections.
- b. for the area below the upper weld joint any imperfection > 33% of the nominal sleeve thickness shall be plugged;
- c. for the area of the tube behind the sleeve and above the upper weld joint, any imperfection produced by degradation shall be plugged unless it can be clearly demonstrated by a qualified NDE technique that tiie imperfection is < 40% of the nominal wall thickness.
Westinghouse Electric Corporation Sleeves
- d. for the area of the tube behind the sleeve, above and including the upper joint, any imperfection produced by degradation shall be plugged unless it can be clearly demonstrated by a qualified NDE technique that the imperfection is < 40%
of the nominal wall thickness.
17030/17040 74f
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SURVEILLANCE REQUIREMEN1' LIMITING CONDITICN FOR OPERATION
- e. for the entire length of the sleeve, any
, imperfection > 41% of the nominal sleeve thickness shall be plugged.
- f. for the area of the tube behind the lower joint, any imperfection produced by l
degradation shall be plugged unless it can be clearly deconstrated by a qualified NOT technique that the imperfection is < 40%
of the nominal wall thickness.
- 7. Unserviceable describes the condition of a tube if it leaks or contains a defect large enough to affect its structural integrity in the event of an Operating Basis Earthquake, a loss-of-coolant accident, or a steam line or feedwater line break as specified in 4.3.1.8.3.C above.
- 8. Tube Inspection means an inspection .
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' of the steam generator tube from the point of entry (hot leg side) completely around the U-bend to the top support of the cold leg.
- 9. Sleeve Inspection means an inspection of the '
sleeved portion of the tube.
Combustion Engineering Welded Sleeve
- a. This inspection will include the upper weld which forms the new pressure boundary and the sleeve material below the upper weld.
Westir.ghouse Electric Corp. Mechanical Sleeve
- b. This inspection will include the entire length of sleeve material.
12030/12040 74fl t ;
4 LIMITING CONDITION FOR OPERATION SURVEILLANCE REQUIREMENT ,
- 10. Repaired Tube means a tube that has undergone-a process that re-establishes 11ti serviceability. The sleeving' process utilized shal' be one of the following:
- a. The Combustion Engineering welded sleeve process as described in. Report Cin-331-P, P,ovision 1-P.
- b. The Westinghouse Electric Corporation mechanical sleeve process as-described in, ' ;
Report WCAP-11669.
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I 12030/12040 74f2 s 'i
ATTACHMENT 2 Description and Justification of proposed Amendment The Zion Technical Specifications currently allow a steam generator tube to be repaired through the installation of a Combustion Engineering (CE) welded sleeve. This option was approved in the referenced letter. This proposed amendment will allow the sleeving process to be performed through the utilization of the Westinghouse Electric mechanical sleeving process. The Westinghouse process is fully described in WCAP 11669, contained in Attachment 4 to this submittal. This process has been previously utilized at Indian
( Point Unit 3, Point Beach Unit 2, and Millstone Unit 2.
The Westinghouse Electric (WB) mechanical sleeving process produces a repaired steam generator tube with an appropriate level of integrity. The A
background information supporting this statement is provided in WCAP 11669.
short summary of WCAP 11669 is provided below.
The WB steam generator sleeving program at Zion 1 and 2 involves the installation of thermally treated Alloy 690 sleeves in both the hot and cold legs of the steam generators. The steam generator tubes to be sleeved are the 7 tubes where tube degradation in the tubesheet and just above che top of the i
tubesheet has exceeded the plugoing limit of 40%. The sleeves span from the l
bottom of the tube projecting out of the tubesheet to a point above the l
secondary side of the tubesheet. The sleeves to be used in the sleeving
' process are long enough in length to span the degraded areas of the tubing in .
the tubesheet region on either the hot or cold legs. The Westinghouse l
Electric sleeve is secured in the tube by mechanical joints at the top and the I bottom of the sleeve.
To maintain sufficient tube integrity, allowable levels of tube wall degradation referred to as plugging limits are established. This determination was performed in accordance with Regulatory Guide 1.121. Tubes which have eddy current indications of degradation in excess of the plugging limits must be repaired or plugged. The information provided in WCAp 11669 defines the portion of the tube and the sleeve for which indications of wall degradation must be evaluated. This information can be summarized as follows:
- 1) Indications of degradation in the entire length of the sleeve must be evaluated against the sleeve plugging limit.
- 2) Indication of tube degradation of any type including a comp 19te guillotine break in the tube betw(ta the bottom of the upper joint and the top of the lower roll expansion does not require that the tube be removed from service.
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- 3) The tube plugging limit continues to apply to the portion of the tube in the upper joint and in the lower roll expansion. As noted above the sleeve plugging limit applies to these areas also.
- 4) The tube pluggir.g limit continues to apply to that portion of the tube above the top of the upper joint..
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i The sleeve design and installation process has been qualified through laboratory testing and actual field performance as describeo in WCAP 11669.
Analytical verification has been performed using design and operating transient parameters selected to envelope loads imposed during normal operating, upset, and accident conditions. Fatigue and stress analysis of sleeved tube assemblies have been completed in accordance with the requirements of the ASME Boiler and Pressure Vessel Code,Section III. The results of the qualification testing, analyses, and plant operating experience demonstrate that the Westinghouse mechanical sleeving process is an acceptable means of maintaining steam generator tube integrity.
The installation of a sleeve into a tube results in an additional flow restriction within the primary system with an associated increase in pressure drop in the steam generator. The effect of this flow restriction on plant operation is evaluated in the same manner that tube plugging effects are analyzed. WCAP 11669 identifies the reduction in primary coolant flow caused by the projected sleeving under normal operating conditions and identifies the number of sleeves which result in a flow reduction equivalent. to one plugged tube.
WCAP 11669 also provides an assessment of the impact of sleeving on both LOCA and non-LOCA transients. These analyses are not adversely impacted by the maximum anticipated sleeving level.
In summary, the Westinghouse Electric mechanical sleeving process, in conjunction with the plugging criteria discussed in Attachment 1, will provide a primery system boundary equivalent to that of an original steam generator tube.
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ATTACHMENT 3
, EVALUATION __OF SIGNIFICANT HAZARDS CONSIDERATION _
PROPOSED CHANGES TO ZION TECHNICAL SPECIPICATION APPENDIX A - SECTION 4.3 R_.EA_CTOR_ COOLANT SY_ STEM
-pBSCRIPTICN OF AMENDMENT REOUEST pm amendment to the Zion Facility Operating license 13 proposed to allow the use of the Westinghouse Electric mechanical sleeving process to repair defective steam generator tubes.
BACKGROUND 10 CFR 50.92 states that a proposed amendment will involve a no significant hazards consideration if the proposed amendment does not:
(1) Involv1 a significant increase in the probability or consequences of an accident previously evaluated; or (2) Create the possibility of a new or different kind of accident from any accident previously evaluated; or (3) Involve a significant reduction in a margin of safety.
Tne discussion below addresses each of these three criteria and demonstrates that the prcposed amendment involves a no significant hazards consideration.
BASIS FOR NO SIGNIFICANT HAZARDS CONSIDERATION DETER!iI.N_ATION Does the proposed amendment (1) Involve a significant increase in the probability or consequences of an accident previously evaluated; or (2) Create the possibility of a new or different kind of accident from any accident previously evaluated; or (3) Involve a significant reduction in a margin of safety?
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U DISCUSSION - ITEM #1 The creation of the option to utilize the Westinghouse Electric (WE) mechanical sleeving process to repair a defective steam generator tube has no effect on either the probability or consequences of any accident previously evaluated. As discussed in WCAP 11669 and Attachment 2, the integrity of the steam generator tubes will be equivalent to that of an original tube or a tube sleeved by the NRC - approved CE process. The continued integrity of the sleeves will be verified by the inspection program required as a result of this change. Thus, since the structural integrity of the tubes will not be affected by this change, there is no increase in the probability of any accident previously evaluated.
Specifically, the probability of a steam generator tube rupture will be unaltered.
In addition, the steam generator will remain capable of performing its required heat transfer function. The information provided in section 3.5.9 of WCAP 11669 demonstrates that the diffsrence in the sleeve induced primary flow reduction resulting from the use of a WE sleeve as contrasted with the currently approved CE process is not significant. As a result, the choice to install a WB sleeve, as opposed to a CE sleeve, will have no significant effect on the steam generator's heat transfer ability.
The sleeving process will allow a repaired steam generator tube to remain in service, rather than completely blocking tr.e tube's flow with plugs. Thus, the act of placing either aiCE or WB sleeve in a steam generator tube actually results in a more efficient steam generator relative to plugging the tube.
Based upon the above discussion, the consequences of any accident previously evaluated will be unaffected because the heat transfer capability of the steam generators will not be significantly altered.
DISCUSSION - ITEM #2 As discussed above, both the structural integrity and the heat transfer capability of Zion steam generators will not be significantly affected by the use of the Westinghouse Electric mechanical sleeving process instead of the CE welded sleeve process. In addition, the steam generator tube sleeves do not interact with any ot Zion's systems. The ability of Zion's safety Systems to perform their function will not be altered. Thus, there is no potential for a new or different kind of accident due to the use of a sleeving process to repair Zion steam generators.
F 1 DISCUSSION - ITEM #3 The heat transfer capabilities of Zion's steam generators will not be significantly altered through the utilization of WE mechancal sleeves as opposed to the currently approved CE sleeves. The sleeving process in general, whether the CE or WE process is utilized, results in a more efficient steam generator when compared to the plugging alternative.
As discussed above and in WCAP 11669, the structural integrity of the steam generator tubes will be unaltered. Either the CE or the WE sleeving process produces a primary systam boundary with the appropriate integrity.
Since both the structural integrity and heat transfer capability of Zion's steam generators will not be significantly altered by the choice of sleeving processes, the margin of safety will not be affected.
Therefore, since the application for amendment satisfies the criteria specified in 10 CFR 50.92 Commonwealth Edison Company has made a determination that the application involves no significant hazards consideration.
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7 ATTACHMENT 4 WCAP 11669 Proprietary and Non-Proprietary Versions 3985K J