ML20207D534

Proposed Tech Specs Authorizing Repair of Steam Generator Tubes W/Indications of Degradation as Alternative to Tube Plugging

ML20207D534
Person / Time
Site:	Farley
Issue date:	12/31/1986
From:	ALABAMA POWER CO.
To:
Shared Package
ML20207D508	List: ML20207D503 ML20207D534
References
TAC-64210, TAC-64211, NUDOCS 8612310053
Download: ML20207D534 (12)

Text

r 1 s o REACTOR COOLANT SYSTEM SURVEILLANCE REQUIREMENTS (Continued)

1. All nonplugged tubes that previously had detectable wall penetrations greater than 20% that were not repaired.

2. Tubes in those areas where experience has indicated potential problems.

3. A tube inspection (pursuant to Specification 4.4.6.4.a.8) 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.

c. The tubes selected as the second and third samples (if required by Table 4.4-2) during each inservice inspection may be subjected to a partial tube inspection provided: 1

1. The tubes selected for these samples include the tubes from those areas of the tube sheet array where tubes with imperfections were previously found.

2. The inspections include those portions of the tubes where imperfections were previously found.

The results of each sample inspections 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 than 1% of the inspected tubes are defective.

Note: In all inspections, previously degraded tubes must exhibit significant (greater than 10%) further wall penetrations to be included in the above percentage calculations.

FARLEY-UNIT 1 3/4 4-10 AMEN 0 MENT NO.

0612310053 861219 PDR ADOCK 05000340 P PDR

REACTOR COOLANT SYSTEM-SURVEILLANCE REQUIREMENTS (Continued) 4.4.6.4 Acceptance Criteria

a. As used in this Specification:

1. Imperfection means an exception to the dimensions, finish or contour of a tube fran that required by fabricati]n drawings or s peci fications. Eddy-current testing indications below 20% of the nominal tube wall thickness, if detectable, may be considered as imperfections.

2. Degradation means a service-induced cracking, wastage, wear or -

general corrosion occurring on either inside or outside of a tube.

3. Degraded Tube means a tube containing imperfections greater than or equal to 20% of the nominal wall thickness caused by degradation.

4. % Degradation means the percentage of the tube wall thickness -

af fected or removed by degradation.

5. Defect means an imperfection of such severity that it exceeds the plugging limit. A tube containing a defect is defective.

6. Plugging Limit means the imperfection depth at or beyond which the

! tube shall be removed from service or repaired and is equal to 40% '

l l

of the nominal tube wall thickness.

i 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 4.4.6.3.c, above.

l l 8. 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.

i .

9. Tube Repair refers to tube sleeving, stress relieving and/or other mechanisms that are used to maintain a tube in service or return a tube to service. This includes the removal of plugs that were installed as a corrective or preventive measure.

I FARLEY-UNIT 1 3/4 4-12 AMENDMENT NO.

I I . , ,

t REACTOR COOLANT SYSTEM

'SURVEILLANCEREQUIREMENTS(Continued) l

10. Preservice Inspection means an inspection of the full length of each tube in each steam generator performed by eddy current techniques prior to service to establish a baseline condition of the tubing. This inspection shall be performed after the field '

hydrostatic test and prior to initial POWER OPERATION using the equipment and techniques expected to be used during subsequent inservice inspections.

b. The steam generator shall be determined OPERABLE after completing the corresponding actions (plug or repair of all tubes exceeding the plugging limit) required by Table 4.4-2.

i 4.4.6.5 Reports [

l a. Following each inservice inspection of steam generator tubes, the  !

l number of tubes plugged or repaired in each steam generator shall be i reported to the Commission within 15 days.

! b. The complete results of the steam generator tube inservice inspection i shall be submitted to the Commission in a Special Report pursuant to Specification 6.9.2 within 12 months following the completion of the  ;

inspection. This Special Report shall include:

1. Number and extent of tubes inspected.

2. Location and percent of wall-thickness penetration for each l indication of an imperfection.

3. Identification of tubes plugged or repaired. <

c. Results of steam generator tube inspections which f all into Category C-3 shall be considered a REPORTABLE EVENT and shall be reported

, pursuant to 10CFR50.73 prior to resumption of plant operation. The written report shall provide a description of investigations conducted to determine the cause of the tube degradation and corrective measures taken to prevent recurrence, r

l FARLEY-UNIT 1 3/4 4-13 AMEN 0 MENT NO.

TABLE 40 4-2 STEAM GENERATOR TUBE INSPECTION

~

32 x . - - -

F; IST SAMPLE INSPECTION 2ND SAMPLE IhSPECTION 3RD SAMPLE INSPECTION

?

EE Sacple Size Result Action Required Result Action Required Result Action Required O

A mininua of C-1 None N/A N/A N/A N/A S Tubes per S.G. C-2 Plug or repair C-1 None N/A N/A defective tubes and inspect additional C-2 Plug or repair C-1 None 25 tu3es in this defective tubes and S.G. inspect additional C-2 Plug or repair 45 tubes in this defective tubes S.G.

C-3 Perform action for C-3 result of first sample w

]s C-3 Perform action for N/A N/A i

,, C-3 result of first

2. sample l w l C-3 Inspect all tubes All other l in this S.G., plug S.G.s are None N/A N/A l or repair defective C-1 l tubes and inspect l 25 tubes in each Some S.G.s Perform action for N/A N/A l cther S.G. C-2 but no C-2 result of additional second sample S.G.s are C-3 3; Notification to Additional Inspect all tubes N/A N/A C2 NRC pursuant to S.G. is in each S.G. and

$! 10CFR50.73 C-3 plug or repair f5 defective tubes.

Si Notification to g NRC pursuant to

- 10CFR50.73 S = 3 N % Where N is the number of steam generators in the unit, and n is the number of steam generators ii inspected during an inspection l -

REACTOR COOLANT SYSTEM BASES 3/4.4.6 STEAM GENERATORS 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. Inservice 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 inservice conditions that lead to corrosion. Inservice 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.

The plant is expected to be operated in a manner such that the secondary coolant will be maintained within those chemistry limits found to result in negligible corrosion of the steam generator tubes. If the secondary coolant chemistry is not maintained within these limits, localized corrosion may likely result in stress corrosion cracking. The extent of cracking during plant operation would 3e limited by the limitation of steam generator tube leakage between the primary coolant system and the secondary coolant system (primary-to-secondary leakage = S00 gallons per day per steam generator).

Cracks having a primary-to-secondary leakage less than this limit during operation will have an adequate margin of safety to withstand the loads imposed during normal operation and by postulated accidents. Operating plants have demonstrated that primary-to-secondary leakage of 500 gallons per day per steam generator can readily be detected by radiation monitors of steam generator blowdown. Leakage in excess of this limit will require plant shutdown and an unscheduled inspection, during which the leaking tubes will be located and plugged or repaired.

Wastage-type defects are unlikely with proper chemistry treatment of the secondary coolant. However, even if a defect should develop in service, it will be found during scheduled inservice steam generator tube examinations.

Plugging or repair will be required for tubes with imperfections exceeding 40% of the tube nominal wall thickness. Steam generator tube inspections of operating plants have demonstrated the capability to reliably detect degradation that has penetrated 20% of the original tube wall thickness.

Whenever the results of any steam generator tubing inservice inspection fall into Category C-3, these results will be reported to the Commission pursuant to 10CFR$0.73 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 necessa ry.

FARLEY-UNIT 1 B3/4 4-3 AMENDMENT NO.

REACTOR COOLANT SYSTEM SURVEILLANCE REQUIREMENTS (Continued)

1. All nonplugged tubes that previously had detectable wall penetrations greater than 20% that were not repaired.

2. Tubes in those areas where experience has indicated potential problems.

3. A tube inspection (pursuant to Specification 4.4.6.4.a.8) 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.

c. The tubes selected as the second and third samples (if required by Table 4.4-2) during each inservice inspection may be subjected to a partial tube inspection provided:

1. The tubes selected for these samples include the tubes from those areas of the tube sheet array where tubes with imperfections were previously found.

2. The inspections include those portions of the tubes 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 than 1% of the inspected tubes are defective.

Note: In all inspections, previously degraded tubes must exhibit significant (greater than 10%) further wall penetrations to be included in the above percentage calculations.

FARLEY-UNIT 2 3/4 4-10 AMENOMENT NO.

REACTOR COOLANT SYSTEM i

SURVEILLANCE REQUIREMENTS (Continued) 4.4.6.4 Acceptance Criteria

a. As used in this Specification:

1. Imperfection 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.

2. Degradation means a service-induced cracking, wastage, wear or general corrosion occurring on either inside or outside of a tube.

3. Degraded Tube means a tube containing imperfections greater than or equal to 20% of the nominal wall thickness caused by degradation.

4. % Degradation means the percentage of the tube wall thickness af fected or removed by degradation.

' . Defect means an imperfection of such severity that it exceeds the a

plugging limit. A tube containing a defect is defective.

l 6. plugging Limit maans the imperfection depth at or beyond which the l

tube snall be removed from service or repaired and is equal to 40%

of the naninal tube wall thickness.

7. Unserviceable describes the condition of a tube if it leaks or contains a defect larga 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 4.4.6.3.c. above.

8. _ 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.

9. _ Tube Repair refers to tube sleeving, stress relieving and/or other mechanisms that are used to maintain a tube in service or return a tube to service. This includes the removal of plugs that were installed as a corrective or preventive measure.

l l

FARLEY-UNIT 2 3/4 4-12 AMENDMENT NO.

7 REACTOR COOLANT SYSTEM SURVEILLANCE REQUIREMENTS (Continued)

10. Preservice Inspection means an inspection of the full length of each tube in each steam generator performed by eddy current techniques prior to service to establish a baseline condition of the tubing. This inspection shall be performed after the field hydrostatic test and prior to initial POWER OPERATION using the equipment and techniques expected to be used during subsequent inservice inspections.

b. The steam generator shall be determined OPERABLE after completing the corresponding actions (plug or repair of all tubes exceeding the plugging limit) required by Table 4.4-2.

4.4.6.5 Reports

a. Following each inservice inspection of steam generator tubes, the number of tubes plugged or repaired in each steam generator shall be reported to the Commission within 15 days.

b. The complete results of the steam generator tube insarvice inspection shall be submitted to the Commission in a Special Report pursuant to Specification 6.9.2 within 12 months following the completion of the inspection. This Special Report shall include:

1. Number and extent of tubes inspected.

2. Location and percent of wall-thickness penetration for each indication of an imperfection.

3. Identification of tubes plugged or repaired.

c. Results of steam generator tube inspections which fall into Category C-3 shall be considered a REPORTABLE EVENT and shall be reported pursuant to 10CFR50.73 prior to resumption of plant operation. The written report shall provide a description of investigations conducted to determine the cause of the tube degradation and corrective measures taken to prevent recurrence.

FARLEY-UNIT 2 3/4 4-13 AMENUMENT NO.

. TABLE 4.4-2 STEAM GENERATOR TUBE INSPECTION N

F, IST SAW LE INSPECTION 2ND SAWLE INSPECTION 3RD SAW LE INSPECTION 7

E Sample Size Result Action Required Result Action Required Result Action Required Z

m A nininua of C-1 None N/A N/A N/A N/A 5 Tubes per S.G. C-2 Plug or repair C-1 None N/A N/A defective tubes and inspect additional C-2 Plug or repair C-1 None l 25 tubes in this defective tubes and S.G. inspect additional C-2 Plug or repair 45 tubes in this defective tubes S.G. l C-3 Perform action for C-3 result of first ta sample f C-3 Perform action for M/A N/A

C-3 result of first sample C-3 Inspect all tubes All other in this S.G., plug 5.G.s are None N/A N/A or repair defective C-1 tubes and inspect 25 tubes in each Some S.G.s Perform action for N/A N/A other S.G. C-2 but no C-2 result of l additional second sample S.G.s are C-3 l

l a Notification to Additional Inspect all tubes N/A N/A 6 NRC pursuant to S.G. is in each S.G. av.d j 10CFR50.73 C-3 plug or repair c defective tubes.

4 Notification to g NRC pursuant to 10CFR50.73 S = 3 N % Where N is the rumber of steam generators in the unit, and n is the number of steam generators ri inspected daring an inspection I . - _, - - - _ - . - - ..- - . - . - , - _ - - - - , - . _ . .- .- .- . - _ - - . _ .

REACTOR COOLANT SYSTEM BASES 3/4.4.6 STEAM GENERATORS 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 l based on a modification of Regulatory Guide 1.83, Revision 1. Inservice 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 inservice conditions that lead to corrosion. Inservice 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.

The plant is expected to be operated in a manner such that the secondary coolant will be maintained within those chemistry limits found to result in negligible corrosion of the steam generator tubes. If the secondary coolant chemistry is not maintained within these limits, localized corrosion may likely result in stress corrosion cracking. The extent of cracking during plant operation would be limited by the limitation of steam generator tube leakage between the primary coolant system and the secondary coolant system l (primary-to-secondary leakage = 600 gallons per day per steam generator).

! Cracks having a primary-to-secondary leakage less than this limit during operation will have an adequate margin of safety to withstand the loads imposed during normal operation and by postulated accidents. Operating plants have demonstrated that primary-to-secondary leakage of 500 gallons per day per steam generator can readily be detected by radiation monitors of steam generator blowdown. Leakage in excess of this limit will requira plant shutdown and an unscheduled inspection, during which the leaking tubes will be located and plugged or repaired.

Wastage-type defects are unlikely with proper chemistry treatment of the secondary coolant. However, even if a defect should develop in service, it will be found during scheduled inservice steam cenerator tube examinations.

Plugging or repair will be required for tubes with imperfections exceeding 40% of the tube nominal wall thickness. Steam generator tube inspections of

! operating plants have demonstrated the capability to reliably detect I degradation that has penetrated 20% of the original tube wall thickness.

l Whenever the results of any steam generator tubing inservice inspection fall into Category C-3, these results will be reported to the Commission pursuant to 10Cf RbO.73 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.

l l

l FARLEY-UNIT 2 H3/4 4-3 AMENDMENT NO.

I

(

ATTACHMENT 2 Significant Hazards Evaluation Pursuant to

, 10CFR50.92 for the Proposed Steam Generator l Tube Repair Technical Specification Change Proposed Change Allow for the corrective or preventive repair of steam generator tubes as an alternative to tube plugging. A definition of tube repair is provided.

)

l

Background

Currently Farley Nuclear Plant Technical Specification Section 3/4.4.6 requires whenever a steam generator tube is found to have imperfection depth at or beyond 40 percent of the naninal tube wall thickness the tube must be plugged. Techniques such as tube sleeving are now available which can repair a defective section of a tube thus allowing the tube to remain in service.

Analysis Question: Does the proposed amendment involve a significant increase in the probability or consequences of an accident previously evaluated?

Response: No. The proposed amendment to the technical specification only allows for an alternative to plugging a defective steam generator tube. For any repair technique utilized, Alabama Power Company will perform a 10CFR50.59 safety evaluation prior to implementation. This evaluation must satisfactorily demonstrate that the probability or consequences of an accident previously evaluated is not increased by any repairs to be performed.

Question: Does the proposed amendment create the possibility of a new or dif ferent kir.d of accident from any accident previously evaluated?

Response: No. Alabama Power Company will perform a safety evaluation in accordance with 10CfHbO.S9 prior to implementing any steam generator tube repair process. The safety evaluation must satisfactorily demonstrate that the possibility of a new or dif ferent kind of accident fran any accident previously evaluated is not created by any repairs to be performed.

Question: Does the proposed amendment involve a significant reduction in a margin of safety?

Significant Hazards Evaluation Pursuant to 10CFR50.92 for the Proposed Steam Generator Tube Repair Technical Specification Change Page 2 Response: No. Regardless of the tube repair method utilized, Alabama Power Company will demonstrate prior to implementation in the 10CFR50.59 safety evaluation that no reduction in safety margin, as defined in the plant technical specifications, will result from the repair.

Conclusion The satisfactory completion of a 10CFR50.59 safety evaluation prior to implementation of any steam generator tube repair process will demonstrate that no adverse safety concern will be created by the repair. Therefore, Alabama Power Company has determined the proposed technical specification is not a significant safety hazard.

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