ML20217F476
| ML20217F476 | |
| Person / Time | |
|---|---|
| Site: | Prairie Island  |
| Issue date: | 10/03/1997 |
| From: | NORTHERN STATES POWER CO. |
| To: | |
| Shared Package | |
| ML20217F468 | List: |
| References | |
| NUDOCS 9710080246 | |
| Download: ML20217F476 (15) | |
Text
- _- __-_ -
TS.4.12-1 REV 30 9/25/78 4.12 STEAM GENERATOR TUBE SURVEILLANCE Applicability Applies to inservice surveillance of the steam generator tubes.
Obiective To assure the continued integrity of the steam generator tubes that are a part of the primary coolant pressure boundary.
Specification Steam generator tubes in each unit shall be determined operable by the following:
A. Steam Generator Sample Selection and Inspection Each steam generator shall be determined operable in accordance with the in-service inspection schedule in Specification 4.12.C. The in-service inapection may be limited to one steam generator on a rotating schedule encompassing 6% of the tubes in the single steam generator, provided the previous inspections indicated that the two steam generators are performing in a like manner.
B. Steam Generator Tube Sample Selection and Inspection-The steam generator tube minimum sample size, inspection result classification, and the corresponding action required shall be as specified in Tablep TS.4.12-1[4hd;TS;4jl212. The in-service inspection of steam generator trbes shall be performed at the frequencies specified in Specification 4.12.C and the inspected tubes shall be verified acceptable per the acceptance critaria of Specification 4.12.D. The tubes selected for each in service inspection shall include at least 3% of the total number of tubes in all steam generators 7andist]TsaE20Foffths@stalMumbeMoffs1seves inishEriEsMihW o W steam' generators ["the~t ses"silicieT foT ihese"'~
lEApec$1onAs snafi"Es"seficEeTon"a ' random basis except:
- 1. Where experience in similar plants with similar water chemistry indicates critical areas to be inspected, then at least 50% of the tubes inspected shall be from these critical areas.
9710080246 971c;3 -
yDR ADOCK 05G00282 PDR
TS.4.18-2 REV 119 5/15/95
-, 2. The first sample of tubes selected for each in-service inspection (subsequent to the preservice inspection) of each steam generator shall include:
(a) All tubes that previously had detectable wall penetrations
(>20%) that have not been plugged or .leeve repaired in the affected area.
(b) Tubes in those areas where experienced has indicated potential problems.
(c) A tube inspection (pursuant to Specification 4.12,D l (h))
shall be performed on each selected tube. If any selected tube does not permit the passage of the eddy current probe for a tube inspection, this shall be recorded and an adjacent tube shall be selected and subjected to a tube inspection.
- 3. In addition to the sample required in Specification 4.12,B.2.a through c, all tubes which have had the F* criteria applied will be inspected in the F* regions of the roll expanded region. The roll expanded region of these tubes may be excluded from the +
requirements of 4.12.B.2.a.
- 4. The tubes selected as the second and third samples (if required by Tableji TS.4.12-1[6MTS[4]2{2) during each inservice inspection may be subjected to a partial tube [priplesvf inspection provided:
(a) The tubes selected for these samples include the tubes from those areas of the tube sheet array where tubes with imperfections were previoasly found.
(b) The inspections include those portions of the tubes?ot pleave) where imperfections were previously found.
The results of each sample inspection shall be classified into one of the following three categories:
Category Inspection Results C-1 Less than 5% of the total tubes inspected are degraded tubes and none of the inspected tubes are defective.
C-2 One or more tubes, but not more than 1% of the total tubes inspected are defective, or between 5% and 10%
of the total tubes inspected are degraded tubes.
C-3 More than 10% of the total tubes inspected are degraded tubes or more that 1% of the inspected tubes are defective.
Note: In all inspections, previously degraded tubes must exhibit significant (>10%) further wall penetrations to be included in the above percentage calculations.
- TS.4.12-4 Acceptance Criteria REV 118 5/15/95 D.
. 1. As_used in this Specification:
(a) Imperfection means an exception to the dimensions, finish or contour of a tube from that required by fr.brication drawings or specifications. Eddy current testing indications below 204 of the nominal tube wall thickness, if detectable, may be considered as imperfections.
(b) 'Derradation means a service induced cracking, wastage, wear or general corrosion occurring on either inside or outside of a tube.
(c) Derraded Tube means a tube containing imperfections h20% of the nominal wall thickness caused by degradation.
(d) % Derradation means the percentage of the tube wall thickness affected.or removed by degradation.
(e) Defect means an imperfection of such severity that it exceeds the repair limit. A tube containing a defect is defective.
(f) P.eoair Limit means the imperfection depth at or beyond which the tube shall be removed from service by plugging or repaired by sleeving because it may become unserviceable prior to the next inspection and is equal to 50% of the ncminal tube vall thickness. If signiiicant general tube thinning occurs, this criteria will be reduced-to 40% wall penetration. This definition does not apply to the portion of the tube in the tubesheet below the F* distance provided the tube is not degraded (i.e., no indications of cracks) within the F*
uistanceforF* tubes.pTh&MpsirlTlimit UsQidsyy 5hilkn9M{ifskjpg6ffsnyjsljejsMsQ1 th(jydeilna$s[sepa!yall gen $fsRthQrsaanri (g). Unserviceable describes the condition of a tube if it leaks or contains a defect large enough to affect its structural integrity in the event of an Operating Basis Earthquake,_a loss-of-coolant accident, or a steam line or feedwater line
-break.
(h). 'labe Inspection means an inspection of the steam generator tube from the point of entry (hot leg side) completely around the U-berd to the top support'of the cold leg.
(1) Sleeving :::n: that tub: cle:cing in per=itted 2nly ir :::::
"::: th: cle: z: rpen: the tubech::t aren 2:.d "h :: leve r -Je4*t, 4e-et-the prierry fluid tuberh :: f :: ishthaltepairfor degradsditubsWegi67'liTusing?UnsV7MlbyT690 jusorendyinsidest6isSArentytui>ejitkijsealAd[$bing'(sleetC aQ5achiendDyj -
esidityporLE bfi replaciny the916sedws1 Min fatful1Ydepths e
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TS.4.12 5.
REV 119 5/15/95
-, -(j ) -F* Distance is the distance from the bottom of the hardroll transition toward the bottom of the tubesheet that has been conservatively determined to be 1.07 inches (not including eddy current uncertainty).
(k) F* Tube is a tube with degradation, below the-F* distance, equal to or greater than 40t, and not degraded (i.e. , no indications of cracking) within the F* distance.
- 2. The steam generator shall be determined OPERABLE after completing the
. corresponding actions (plug or repair by sleeving all tubes exceeding the repair limit-and all tubes containing through wall cracks or classify sts F*, tubes) required by Tabley TS.4.12-1[shd8TS14).}212.
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E. Reports
.. Following each in service inspection of steam generator tubes, if there are any tubes requiring plugging or sleeving, the number of tubes plugged or sleeved in each steam generator shall be reported to the Commission wJthin 15 days.
-_2 The results.of steam generator tube inservice 1,u,,ections shall'be included with the summary reports of ASME Code Section XI inspections-submitted within 90 days of the end of each -refueling outage. Results of ateam generator-tube inservice inspections not: associated with a refueling cutage chall be submitted within 90 days of the completion of the inspection. These reports shall include: (1) number and' extent of tubes-inspected, (2) location and percent of wall-thickness penetration for- eact indication of an imperfection- and (3) identification of tubes
. plugged or sleeved.
- 3. Results ofl steam generator _ tube _ inspections which fall into Category C-3 require notification to the Commission prior to_ resumption of plant
-operation, and reporting as a special report to the Commission within
-30 days. This special report shall-provide a description of
. investigations conducted to determine cause of the tube degradation and corrective measures taken to prcvent recurrence.
- 4. The results of inspections performed under Specification 4.12.B for all tubes that hwe defects below the .F* distance, and were not plugged,-
shall be reported to the Commission within 15 days following the inspection. The report shall include:
- a. Identification of F* tubes, and
- b. Location and extent of degradation.
l l
Tabis5TSi4:1272 S. tssa"G.e.nsidto.
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e.UMIss.pecties 1stisampleI;Inspesti6s 2nd? Sample.~Inspsetics 1
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- - separat. e. : po...p~u.la._t_ ion - -Tor..n.et. .e,r.mi._nati_on.~i ob_.w._op,e._e.xp_an.si..o. n.
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- B.6.13 1 REV 91 10/27/89 4.12 STEAM CENERATOR TUBE SURVEILLANCE Bases The Surveillance Requirements for inspection of the steam generator tubes ensure that the structural integrity of this portion of the RCS will be maintained. The program for inservice inspection of steam generator tubes is based on a modification of Regulatory Guide 1.83, Revision 1.
In service inspection of steam generator tubing is essential in order to maintain surveillance of the conditions of the tubes in the event that there is evidence of mechanical damage or progressive degradation due to design, manufacturing errors, or in service conditions - that lead to corrosion. In-service inspection of steam generator tubing also provides a means of characterizing the nature and cause of any tube degradation so that corrective measures can be taken.
A tC thei re qu es tTo f {th61NRC 7a'? rs 4diremeriti fo r71n7s eWid elinspse tioh?o f fh t leasti 20s ; oft theS totali number of[sleeveshin service}in? both : steam generat6rs wasladded;to TS14.12.Bh fInfadditibnb TablelTS/4112'.-22was added Ltoiprov.ide: samp1s expansionfrequirements? basedkonithe resultsjof; the initial (sampleiinspectionisimilarito:TableJ4},12-1SThisLtvpejofsample sizefandfexpansion requirementhisTeo'nsistent with the:EPRKPWRTSteam Generator: Examination Guideline'sh 1The :sampleQalectiorGisf appliedjtoj esch type f o.f j aleevej LTypesfofisle aves are s categorized . byfstich characteris tics as the tins tallation; vendorn the; sleeve fma terial', ? theftype Xo flj oint {suchlad
~
lower? edge Cweld;or flowerj hard rollsj oints;f the psleef61ocation(suchias tubefaupportl platef ois tubsshee t( andl whethergot;thd gidedfj oints[have rec e.tved;pos it veldj hoatj ereatmentj The plant is expected to be operated in a manner such that the secondary coolant will be maintained within those parameters found to result in negligible corrosion of the steam generator tubes. If the secondary coolant chemistry is not maintained within these parameters, localized corrosion would most likely result in stress corrosion cracking.
The extent of cracking during plant operation would be limited by-the limitation of steam generator leakage between the primary coolant system and the secondary coolant system (primary-to secondary leakage -
1.0 gpm). Cracks having a primary-to-secondary leakage less than 1.0 gpm during operation will have an adequate margir cf safety against failure due to loads imposed by design basis accidents (Reference 1) . Operating
-plants have demonstrated that primary-to-secondary leakage as low as 0.1 gpm will be detected by radistion monitors of steam generator blowdown. Leakage in excess of 1.0 gpm will require plant shutdown and an unscheduled eddy current inspection, during which the leaking tubes will be located and plugged or sleeved.
Wastage-type defects are unlikely wi.th proper chemistry treatment of secondary coolant. However, even if this type of defect occurs it will be found during scheduled in-service sceam generator tube inspections.
Repair or plugging will be required of all tubes with imperfections that could develop defects having less than the minimum acceptable wall thickness prior to the next inservice inspection which, by the definition of Specification 4.12.D.1.(f), is 50% of the tube or sleeve nominal wall thickneas. Wastage type defects having a wall thickness greater than 0.025 inches will have adequate margins of safety against failure due to loads imposed by normal plant operation and design basis accidents (Reference 1). Steam generator tube inspections of operating
B.4.12-2 REV 119 5/15/95 4.12 STEAM GENERATOR TUBE SURVEILIANCE
_g continued
.JhsAs plants have demonstrated the capability to reliably detect wastage type defects that have penetrated 20% of the original 0.050 inch wall thickness (Reference 2).
Plugging or sleeving is not required for tubes meeting the F* criteria.
The F* distance will be controlled by a combination of eddy current inspection and/or process control. For a new additional roll expansion, the requirement will be at least 1.2 inches of new hard roll. This is controlled by the length of the rollers (1.25 inch effective lengtn). The distance from the original roll transition zone is also controlled by the process in that the lower end of the new roll expansion is located one inch above the original roll expansion. In the case of the new roll, eddy current examination will confirm there are no indications in the new roll region and that there is a new roll region with wall defined upper and i lower expansion transitions, n
When eddy current examination, alone, must determine the F* distance, such as in the existing hard roll region, or when multiple lengths of additional hard rolls have been added, the eddy current uncertain" is qualified by testing against known standards. That value is expected to be 0.18 inches. Therefore, the F* distance measured by eddy current (sum j of 1.07 and 0.18) will be conservatively set at 1.3 inches.
When more than one Alternate Repair Criteria are used, the summation of leakage from all tubes left in service by all repair criteria must be less than the allowable leakage for the most limiting of those Alternate Repair Critoria.
Whenever the results of any steam generator tubing in service inspection fall into Category C-3, these results will be promptly reported to the Commission prior to resumption of plant operation. Such cases will be considered by the Commission on a case-by case basis and may result in a requirement for analysis, laboratory examinations, tests, additional eddy-current inspection, and revision of the Technical Specifications, if necessary.
Degraded steam generator tubes may be repaired by the installation of sleeves which span the section of de6taded eteam generator tubing. A steam generator tube with a sleeve installed meets the structural requirements of tubes which are not degraded.
The following sleeve designs have been found acceptable by the NRC Staff;
- b. Westinghouse Brazed Sleeves (WCAP-10820)
forfslee'ves Lins talled l pri'orf toJ 0ctobers171997) d.] Combustion l Engineering!1A$TighsSleevis((CEN-629{Pjfforisleevey installediafterloctober21M1997)
. Attachment 2 Revised Technical Specification Pages i
G
// . .________;
TS.4.12-1 REV l
l .
L 4.12 STEAli GENERATOR TUBE SURVEILiANCE Applicability Applies to inservice surveillance oi the steam generator tubes.
Obiective To assure the continued integrity of the steam generator tubes that are a part of the primary coolant pressure boundary.
Specification Steam generator tubes in each unit shall be determined operable by the following:
A. Steam Generator Sample Selection and Inspection-Each steam generator shall be determined operable in accordance with the in-service inspection schedule in Specification 4.12.G. The in service inspection may be limited to one steam generator on a rotating schedule encompassing 6% of the tubes in the single steam generator, provided the previous inspections indicated that the two steam generators are performing in a like manner.
B. Steam Generator Tube Sample Selection and Inspection-The steam generator tube minimum sample size, inspection result classification, and the corresponding action required shall be as specified in Tables TS.4.12 1 and TS.4.12-2. The in-service inspection of steam Senerator tubes shall be performed at the l frequencies specified in Specification 4.12.C and the inspected tubes shall be verified acceptable per the acceptance criteria of Specification 4.12.D. The tubes selected for each in-service inspection shall include at least 3% of the total number of tubes in all steam generators and at least 20% of the total number of sleeves in service in both steam generators; the tubes selected for these inspections shall be selected on a random basis except:
- 1. Where experience in similar plants with similar water chemistry indicates critical areas to be inspected, then at least 50% of the tubes inspected shall be from these critical areas.
, TS.4.12-2 REV
- 2. The first sample of tubes selected for each in-service inspection (subsequent to the preservice inspection) of ench steam generator shall include:
(a) All tubes that previously had detectable wall penetrations
(>20%) that have not been plugged or sleeve repaired in the affected area.
(b) Tubes in those areas where experienced has indicated potential problems. -
(c) A tube inspection (pursuant to Specification 4.12.D.l.(h))
shall be performed on each selected tube. If any selected tube does not permit the passage of the eddy current probe for a tube inspection, this shall be recorded and an adjacent tube shall be selected and subjected to a tube inspection.
- 3. In addition to the sample required in Specification 4.12.B.2.a
, through c, all tubes Faich have had the F* criteria applied will l be inspected in the F* regions of the roll expanded region. The roll expanded region of these tubes may_be excluded from the requirements of 4.12.B.2.a.
- 4. The tubes selected as the second and third samples (if required by Tables TS.4.12-1 or TS.4.12-2) during each inservice inspection may be subjected to a partial tube or sleeve ,
inspection provided:
(a) The tubes selected for these samples include the tubes from those areas of the tube sheet array where tubes with imperfections were previously found.
(b) The inspections include those portions of the tubes or sleeves where imperfections were previously found.
The results of each sample inspection shall be classified into one of the following three categories:
Category Inspection Results C-1 Less than 5% of the total tubes inspected are degraded tubes and none of the inspected tubes are defective.
C-2 One or more tubes, but not more than 1% of the total tubes inspected are defective, or between 5% and 10%
of the total tubes inspected are degraded tubes.
C-3 More than 10% of the total tubes inspected are-degraded tubes or more that 1% of the inspected tubes are defective.
Note: In all inspections, previously degraded tubes must exhibit significant-(>10%) further wall penetrations to be included in the above percentage calculations.
. TS.4.12-4 REV O D. Acceptance Criteria g 1. 'As used in this Specification:
(a) Imoerfection means an exception to the dimensions, finish or contour of a tube from that required by fabrication drawings or specifications. Eddy-current testing indications below 20% of-the nominal tube wall thickness, if detectable, may be considered as imperfections.
.(b) Derradation means a service-induced cracking, wastage, wear or
-general corrosion occurring on either inside or outside of a tube.
(c) Derraded Tube means a-tube containing imperfections n20% of the nominal wall thickness caused by degradation.
(d) % Derradation means the percentage of the tube wall thickness affected or removed by degradation.
(e) Defect means an imperfection of such severity that it exceeds the repair limit. A tube containing a defect is defective.
l (f) Repair Limit means the imperfection depth at or beyond which the tube shall be removed from service by plugging or repaired by sleev3ng because it may become unserviceable prior to the
{ next inspection and is equal to 50% of the nominal tube wall j thickness. If significant general tube thinning occurs, this 1
criteria will be reduced to 40% wall penetration. This definition does not apply to the pcrtion of the tube in the tubesheet-below the F* distance provided the tube is not degraded (i.e. , no indications of cracks) within the F*
distance for F* tubes. The repair limit for the pressure boundary region of any sleeve is 31% of the' nominal sleeve wall 3 thickness.
(g) Unserviceable describes the condition of a tube ifuit leaks or contains a defect large enough to affect its structural integrity in the eve nt of an Operating Basis Earthquake, a loss-of-coolant accident, or a steam line or feedwater line break.
(h) Tube Inspection means an inspection 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.
(1) Sleevinz is the repair of degraded-tube regions using a new Alloy 690 tubing sleeve inserted inside the parent tube and ,
sealed at each end by welding or by replacing the lower weld in a' full depth tubesheet sleeve with a hard rolled joint. The new sleeve becomes the pressure boundary spanning the original degraded tube region.
I
, TS.4.12-5 REV t-l , ' (j ) F* Distance is the distance from the bottom of the hardroll transition toward the bottom of the tubesheet that has been conservatively determined to be 1.07 inches (not including eddy current uncertainty) .
(k) F* Tube is a tube with degradation, below the F* distance, equal to or greater than 40%, and not degraded (i.e., no indications of cracking) within the F* distance.
- 2. The steam generator shall be determined OPERABLE after completing the corresponding actions (plug or repair by sleeving all tubes exceeding the repair limit and all tubes containing through-wall cracks or classify as F* tubes) required by Tables TS.4.12-1 and TS.4.12 2.
- 3. Tube repair, after October 1, 1997, using Combustion Engineering welded sleeves shall be in accordance with the methods described in the following:
CEN-629-P, Revision 2, " Repair of Westinghouse Series 44 and 51 Steam Generator Tubes Using Leak Tight Sleeves";
CEN 629-P, Addendum 1, Revision 1, " Repair of Westinghouse Series 44 and 51 Steam Generator Tubes Using Leak Tight Sleeves" E. Reports
- 1. Following each in-service inspection of s;eam generator tubes, if there are any tubes requiring plugging or sleeving, the number of tubes plugged or sleeved in each steam generator shall be reported to the >
Commission within 15 days.
- 2. The results of steam generator tube inservice inspections shall be included with the summary reports of ASME Code Section XI inspections submitted within 90 days of the end of each refueling outage. Results of steam generator tube inservice inspections not associated with a refueling outage shall be submitted within 90 days of the completion of the inspection. These reports shall include: (1) number and extent of tubes inspected, (2) location and percent of wall-thickness penetration for each indication of an imperfection and (3) identification of tubes plugged or sleeved.
- 3. Results of steam generator tube inspections which fall into Category C-3 require notification to the Commission prior to resumption of plant operation, and reporting as a special report to the Commission within 30 days. This special report shall provide a description of investigations conducted to determine cause of the tube degradation and corrective measures taken to prevent recurrence.
- 4. The results of inspections performed under Specification 4.12.B for all tubes that have defects below the F* distance, and vere not plugged, shall be reported to the Commission within 15 days following the inspection. The report shall include:
- a. Identification of F* tubes, and
- b. Location and extent of degradation.
J
-l
. Table TS.4'.12-2 Steam Generator Tube Sleeve Inspection ,
'lst Sample Inspection 2nd Sample Inspection Sample' Size . Result Action Required Result Action Required' A minimum of 20% of 'C-1 None. N/A N/A Tube Sleeves (1) C-1 None.
C-2 Inspect all remaining tube sleeves in this S.G. and plug or repair defective sleeved tubes. C-2 Plug or repair' defective sleeved tubes C-3 Perform action-for C-3 result of first sample C-3 Inspect all tube sleeves in this The other None S.G., inspect 20% of the tube S.G. is C-1 sleeves in the other S.C., and plug or repair defective sleeved The other Perform action for C 2 tubes S.G. is C-2 results of first sample The other Inspect all tube sleeves in S.C is C-3 each S.G. and plug or repair defective sleeved tubes (1) Each type of sleeve is considered a separate population for determination of scope expansion E..
L
~
. B.4.12-1 REV 4.12 STEAM GENERATOR TUBE SURVEILLANCE Bases The Surveillance Requirements for inspection of the steam generator tubes ensure that the structural integrity of this portion of the RCS will be maintained. The program for inservice inspection of steam generator tubes is based on a modification of Regulatory Guide 1.83, Revision 1.
In service inspection of steam generator tubing is essential in order to maintain surveillance of the conditions of the tubes in the event that there is evidence of mechanical damage or progressive degradation due to design, manufacturing errors, or in-service conditions that lead to corrosion. In-service inspection of steam generator tubing also providas a means of characterizing the nature and cause of any tube degradation so that corrective measures can be taken.
At the request of the NRC, a requirement for in service inspection of at least 20% of the total number of sleeves in service in both steam generators was added to TS 4.12.B. In addition, Table TS 4.12.-2 was added to provide sample expansion requirements based on the results of the initial sample inspection similar to Table 4.12-1 This type of sample site and expansion requirement is consistent with the EPRI PWR Steam Generator Examination Guidelines. The sample selection is applied to each type of sleeve. Types of sleeves are categorized by such characteristics as the installation vendor, the sleeve material, the type of joint such as lower edge weld or lower hard roll joints, the sleeve location such as tube support plate or tubesheet and whether not the welded joints have received post weld heat treatment.
The plant is expected to be operated in a manner such that the secondary coolant will be maintained within those parameters found to result in negligible corrosion of the steam generator tubes. If the secondary coolant chemistry is not maintained within these parameters, localized corrosion would most likely result in stress corrosion cracking.
The extent of cracking during plant operation would be limited by the limitation of steam generator leakage between the primary coolant system and the secondary coolant system (primary-to-recondary leakage -
1.0 gpm). Cracks having a primary-to-secondary leakage less than 1.0 gpm during operation will have an adequate margin of safety against failure due to loads imposed by design basis accidents (Reference 1). Operating plants have demonstrated that primary-to-secondary leakage as 1o1 as 0.1 gpm will be detected by radiation monitors of steam generator blowdown. Leakage in excess of 1.0 gpm will require plant shutdown and an unscheduled eddy current inspection, during which the leaking tubes will be located and plugged er sleeved.
Wastage-type defects are unlikely with proper chemistry treatment of secondary coolant. However, even if this type of defect occurs it will be found during scheduled in-service steam generator tube inspections.
Repair or plugging will be required of all tubes with imperfections that could develop defects having less than the minimum acceptable wall thickness prior to the next inservice inspection which, by the definition of Specification 4.12.D.1.(f), is 50% of the tube or sleeve nominal wall thickness. Wastage type defects having a wal thickness greater than 0.025 inches will have adequate margins of safety against failure due to loads imposed by normal plant operation and design basis accidents (Reference 1). Steam generator tube inspections of operating l
, B.4.12 2 REV 4.12 STEAM CENERATOR TUBE SURVEILLANCE
, Base's continued plants have demonstrated the capability to reliably detect wastage type defects that have penetrated 20% of the original 0.050-inch wall thickness (Reference 2).
Plugging or sleeving is not required for tubes meeting the F* criteria.
The F* distance will be controlled by a combination of eddy current inspection and/or process contrcl. For a new additional roll expansion, the requirement will be at least 1.2 inches of new hard roll. This is controlled by the length of the rollors (1.25 inch effective length). The distance from the original roll transition zone is also controlled by the process in that the lower end of the new roll expansion is located one inch above the original roll expansion, In the case of the new roll, eddy current examination will confirm there are no indications in the new roll region and that there is a new roll region with well defined upper and lower expansion transitions.
When eddy current examination, alone, must determine the F* distance, such as in the existing hard roll region, or when multiple lengths of additional hard rolls have been added, the eddy current uncertainty is qualified by testing against known standards. That value is expected to be 0.18 inches. Therefore, the F* distance measured by eddy current (sum of 1.07 and 0.18) will be conservatively set at 1.3 inches.
When more than one Alternate Repair Criteria are used, the summation of leakage from all tubes lef t in service by all repair criteria must be less than the allowable leakage Eor the most limiting of those Alternate Repair Criteria.
Whenever the results of any steam generator tubing in-service inspection fall into Category C 3, these results will be promptly reported to the Commission prior to resumption of plant operation. Such cases will be considered by the Commission on a case-by-case basis and may result in a requirement for analysis, laboratory examinations, tests, additional eddy-current inspection, and revision of the Technical Specifications, if necessary. >
. Degraded steam generator tubes may be repaired by the installetion of sleeves which span the section of degraded steam generator tubing. A steam generator tube with a sleeve installed meets the structural requirements of tubes which are not degraded.
The following sleeve designs have been found acceptable by the NRC Staff:
- b. Westinghouse Brazed Sleeves (WCAP-10820)
- c. Combustion Engineering Leak Tight Sleeves (CEN-294-P, for sleeves installed prior to October 1, 1997)
- d. Combustion Engineering Leak Tight Sleeves (CEN-629-P, for sleeves installed after October 1, 1997)
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