ML13331B021

Proposed Change 182 to Tech Spec 4.16, Inservice Insp of Steam Generator Tubing

ML13331B021
Person / Time
Site:	San Onofre
Issue date:	03/10/1988
From:	SOUTHERN CALIFORNIA EDISON CO.
To:
Shared Package
ML13331B019	List: ML13331B018 ML13331B020 ML13331B021
References
TAC-67463, NUDOCS 8803160310
Download: ML13331B021 (17)

Text

Attachment 1 EXISTING TECHNICAL SPECIFICATION 8803160310 980310 PDR ADOCK 05000206 p

PDR

4.16 INSERVICE INSPEO N OF STEAM GENERATOR TUBING APPLICABILITY:

Applies to the inservice inspection and sampling selection for steam generator tubing.

OBJECTIVE:

To monitor the integrity of the steam generator tube primary boundary and provide guidance for corrective action when imperfections are observed.

SPECIFICATION: A. GENERAL STEAM GENERATOR TUBE SELECTION The steam generators shall be inspected when shutdown by 44 selecting steam genertor tubes on the following basis:

10/31/78

1. Tubes for the inpsection shall be selected on a random basis except where experience at San Onofre Unit 1 or experience in similar plants indicates critical areas to be inspected.

2.

Each inspection shall include at least 3% of the total number of tubes in each steam generator to be inspected.

3.

Inservice inspections may be limited to one steam generator on a rotating schedule encompassing 3% of the total tubes of steam generators in the plant if the results of previous inspections indicate that all steam generators are performing in a like manner.

4.

Every inspection shall include all non-plugged tubes in the steam generators to be inspected that previously had detected imperfections greater than 20%, except as specified in Specification C.1.

B. SUPPLEMENTARY INSPECTIONS If the inspections in Specification A indicate imperfections, additional inspections shall be required as follows:

1.

If any of the tubes inspected pursuant to Specification A.3 have imperfections greater than 20%

that were not detected during the previous inspections or have previously detected imperfections that have increased more than 10% wall-penetration since their last inspection, inspect 3% of the tubes in one of the uninspected steam generators.

4-90 Revised:

12/15/78

2 If more than 10% of the tubes 0bpected in a steam generator have imperfections greater than 20% that were not detected during the previous inspections or have previously detected imperfections that have increased more than 10% wall penetration since their last inspection, or one or more of the tubes inspected have an imperfection in excess of the plugging limit, inspect an additional 3% of the tubes in that steam generator, concentrating on tubes in those areas of the tube sheet array where tubes with imperfections were found and on that length of tube where the imperfections were found.

In addition, the 44 rest of the steam generators shall be inspected in 10/31/78 accordance with Specification A.2.

3.

If the additional inspection in Specification B.2 indicates that more than 10% of the additionally inspected tubes have imperfections greater than 20%

that were not detected during the previous inspections or have previously detected imperfections that have increased more than 10% wall penetration since their last inspection, or one or more of the additionally inspected tubes have an imperfection in excess of the plugging limit, inspect an additional 6% of the tubes in that steam generator in the area of the tubesheet array where tubes with imperfections were found and through that length of tube where the imperfections were found.

C. SPECIAL STEAM GENERATOR TUBE INSPECTIONS In addition to the general steam generator tube inspections performed in Specifications A and B, every inspection shall include the following special inspections:

1.

Every inspection shall include all nonplugged tubes in one of the steam generators that previously had been noted as having discretely quantifiable imperfections greater than 30% at antivibration bar (AVB) intersections, and all non-plugged tubes in that steam generator that previously had been noted as having imperfections at AVB intersections which were not discretely quantifiable but which were identified during previous inspections as being in the 30 to 50% range.

2.

At each steam generator inspection, all previously identified restricted tubes in either steam generator A or C shall be gauged by using eddy current probes to determine restriction sizes.

4-91 Revised:

12/15/78

D.

INOCTION FREQUENCY The inspections in Specifications A and B above shall be performed at the following frequencies:

1.

Inservice inspections shall be not less than 10 nor more than 24 calendar months after the previous inspection.

2.

If two consecutive inspections indicate that less than 10% of the tubes inspected have either (a) new imperfections greater than 20% or (b) previous imperfections that have increased more than 10% since their last inspection, the inspections shall be not less than 10 nor more than 40 calendar months after the previous inspection.

3.

Unscheduled inspections shall be conducted in accordance with Specification A in the event of primary-to-secondary leaks exceeding Specification 44 3.1.4.0, a seismic occurrence greater than an 10/31/78 operating basis earthquake, a loss-of-coolant accident requiring actuation of engineered safeguards, or a major steam line or feedwater line break.

E. ACCEPTANCE CRITERIA

1.

As used in this specification:

a. Imperfection means an exception to the dimensions, finish, or contour required by drawing or specification.

b. Defect means an imperfection of such severity that the tube is unacceptable for continued service.

c. Plugging limit means the imperfection depth at or 60 beyond which plugging of the tube must be 6/8/81 performed. The plugging limit is equal to or greater than 50% of the nominal tube wall thickness, except where sleeves are installed, in which case the plugging limit is equal to or greater than 40% of the nominal sleeve wall thickness.

4-92 Revised:

12/15/78

2. If. in the inspections performed under Specification A,

a. Less than 10% of the total tubes inspected have imperfections greater than 20% that were not detected during the previous inspections or have previously detected imperfections that have increased more than 10% wall penetration, and

b. No tube inspected exceeds the plugging limit, plant operation may resume.

3. If, in the inspections performed under Specification B,

a. Less than 10% of the total tubes inspected have imperfections greater than 20% that were not detected during the previous inspections or have 44 previously detected imperfections that have 10/31/78 increased more than 10% wall penetration, and

b. No more than 3 of the tubes inspected exceed the plugging limit, plant operation may resume after performance of the corrective action in Specification F.

4. If, in the Inspections performed under Specification B,

a. More than 10% of the tubes inspected have imperfections greater than 20% that were not detected during the previous inspections or have previously detected imperfections that have increased more than 10% wall penetration, or

b. More than 3 of the tubes inspected exceed the plugging limit, the situation shall be reported to the Commission in accordance with Technical Specification 6.6 for 91 approval of the proposed remedial action.

11/14/85

5. If in the inspections performed under Specification C.1, wear rates are observed at AVB intersections which are inconsistent with the 50% plugging criterion, the situation shall be reported to the Commission in accordance with Technical Specification 6.6 for approval of the proposed 91 remedial action.

11/14/85 4-93 Revised: 11/14/85

6.

If in the inspections performed under Specification C.2 progression of the denting process is observed to be recurring, the situation shall be reported to the Commission in accordance with Technical Specification 6.6 for 91 approval of the proposed remedial action.

1 11/14/85 F. CORRECTIVE ACTION All leaking tubes, defective tubes, and tubes with imperfections exceeding the plugging limit shall be repaired or plugged.

BASIS:

The Surveillance Requirements for inspection of the steam generator tubes ensure that the structural integrity of this portion of the Reactor Coolant System will be maintained. The program for inservice inspection of steam generator tubes is 44 based on Regulatory Guide 1.83, Revision 1. Inservice 10/31/78 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 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 (primary-to-secondary leakage..3 gallons per minute 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.3 gpm per steam generator can readily be detected by radiation monitors of steam generator 44 blowdown.

Leakage in excess of this limit will require 10/31/78 shutdown during which the leaking tubes will be located and plugged and additional inspections performed.

4-94 Revised:

11/14/85

If a c

t should develop in service,

• will be found during scheduled inservice steam generator tube examinations.

Plugging will be required for all tubes with imperfections 60 exceeding the plugging limit of 50% of the tube nominal wall 6/8/81 thickness, except where sleeves are installed, in which case the plugging limit is 40% of the nominal sleeve wall thickness. A plugging limit of 50% for tubes and 40% for sleeves ensures that defects will not occur between inspection intervals.

The results of tube ID gauging and dent detection conducted in San Onofre Unit I steam generators demonstrate that the denting process has been arrested. Continuing assurance of this condition can be provided by performing a program of limited tube ID gauging and dent detection in either steam generator A or C on a refueling outage frequency. Adequate surveillance of denting related tube restrictions can be maintained at refueling intervals by noting any new 44 restrictions during the conduct of general surveillance and 10/31/78 AVB inspections and by gauging tubes which have previously been noted as being restricted. Progression of denting can also be monitored in either steam generator A or C by evaluating third and fourth support plate denting data obtained from the general surveillance and AVB inspections as well as from the ID gauging program and comparing these results with those of previous inspections.

The results of AVB area inspections conducted in San Onofre Unit I steam generators demonstrate that AVB modifications installed during the Cycle VI refueling outage were successful in eliminating significant growth of tube wall penetration indications at AVE locations. Continuing assurance of this condition can be provided by performing U-bend inspections at refueling outage intervals of tubes having wall penetration indications in excess of 30% at AVB locations.

4-95 Revised:

6/23/81 PROPOSED TECHNICAL SPECIFICATION 4.16 INSERVICE INSPECTION OF STEAM GENERATOR TUBING APPLICABILITY:

Applies to the inservice inspection and sampling selection for steam generator tubing.

OBJECTIVE:

To monitor the integrity of the steam generator tube primary boundary and provide guidance for corrective action when imperfections are observed.

SPECIFICATION:

A. GENERAL STEAM GENERATOR TUBE SELECTION The steam generators shall be inspected when shutdown by selecting steam generator tubes on the following basis:

1. Tubes for the inspection shall be selected on a random basis except where experience at San Onofre Unit 1 or experience in similar plants indicates critical areas to be inspected.

2. Each inspection shall include at least 3% of the total number of tubes in each steam generator to be inspected.

3. Inservice inspections may be limited to one steam generator on a rotating schedule encompassing 3% of the total tubes of steam generators in the plant if the results of previous inspections indicate that all steam generators are performing in a like manner.

4. Every inspection shall include all non-plugged tubes, in the steam generator(s) to be inspected, that previously had detected imperfections greater than 20%, except as specified in Specification C.l.

5. Every inspection shall include an inspection in the tubesheet region of all tubes in service, in the steam generator(s) to be inspected, with defects below the F* distance.

B. SUPPLEMENTARY INSPECTIONS If the inspections in Specification A indicate imperfections, additional inspections shall be required as follows:

1. If any of the tubes inspected pursuant to Specification A.3 have imperfections greater than 20% that were not detected during the previous inspections or have previously detected imperfections that have increased more than 10%

wall penetration since their last inspection, inspect 3% of the tubes in one of the uninspected steam generators.

2. If more than 10% of the tubes inspected in a steam generator have imperfections greater than 20% that were not detected during the previous inspections or have previously detected imperfections that have increased more than 10% wall penetration since their last inspection, or one or more of the tubes inspected have an imperfection in excess of the plugging limit, inspect an additional 3% of the tubes in that steam generator, concentrating on tubes in those areas of the tube sheet array where tubes with imperfections were found and on that length of tube where the imperfections were found. In addition, the rest of the steam generators shall be inspected in accordance with Specification A.2.

3. If the additional inspection in Specification B.2 indicates that more than 10% of the additionally inspected tubes have imperfections greater than 20%

that were not detected during the previous inspections or have previously detected imperfections that have increased more than 10% wall penetration since their last inspection, or one or more of the additionally inspected tubes have an imperfection in excess of the plugging limit, inspect an additional 6% of the tubes in that steam generator in the area of the tubesheet array where tubes with imperfections were found and through that length of tube where the imperfections were found.

C. SPECIAL STEAM GENERATOR TUBE INSPECTIONS In addition to the general steam generator tube inspections performed in Specifications A and B, every inspection shall include the following special inspections:

1. Every inspection shall include all nonplugged tubes in one of the steam generators that previously had been noted as having discretely quantifiable imperfections greater than 30% at antivibration bar (AVB) intersections, and all non-plugged tubes in that steam generator that previously had been noted as having imperfections at AVB intersections which were not discretely quantifiable but which were identified during previous inspections as being in the 30 to 50% range.

2. At each steam generator inspection, all previously identified restricted tubes in either steam generator A or C shall be gauged by using eddy current probes to determine restriction sizes.

D. INSPECTION FREQUENCY The inspections in Specifications A and B above shall be performed at the following frequencies:

1. Inservice inspections shall be not less than 10 nor more than 24 calendar months after the previous inspection.

2. If two consecutive inspections indicate that less than 10% of the tubes inspected have either (a) new imperfections greater than 20% or (b) previous imperfections that have increased more than 10%

since their last inspection, the inspections shall be not less than 10 nor more than 40 calendar months after the previous inspection.

3. Unscheduled inspections shall be conducted in accordance with Specification A in the event of primary-to-secondary leaks exceeding Specification 3.1.4.C, a seismic occurrence greater than an operating basis earthquake, a loss-of-coolant accident requiring actuation of engineered safeguards, or a major steam line or feedwater line break.

E. ACCEPTANCE CRITERIA

1. As used in this specification:

a. Imperfection means an exception to the dimensions, finish, or contour required by drawing or specification.

b. Defect means an imperfection of such severity that the tube is unacceptable for continued service.

c. Plugging limit means the imperfection depth at or beyond which plugging of the tube must be performed. The plugging limit is equal to or greater than 50% of the nominal tube wall thickness, except where sleeves are installed, in which case the plugging limit is equal to or greater than 40% of the nominal sleeve wall thickness. This definition does not apply to the region of the tube below the F* distance, provided the tube has no indications of cracking within the F* distance.

d. Tube roll expansion means that portion of the tube which has been increased in diameter by a rolling process such that no crevice exists between the outside diameter of the tube and the tubesheet.

e. F* Distance means the minimum length of the roll expanded portion of the tube which cannot contain any defects in order to ensure the tube does not pull out of the tubesheet. The F*

distance is 1.0 inches and is measured from the top of the roll expansion of the tube down toward the bottom of the tubesheet.

2. If, in the inspections performed under Specification A,

a. Less than 10% of the total tubes inspected have imperfections greater than 20% that were not detected during the previous inspections or have previously detected imperfections that have increased more than 10% wall penetration, and

b. No tube inspected exceeds the plugging limit, plant operation may resume.

3. If, in the inspections performed under Specification B,

a. Less than 10% of the total tubes inspected have imperfections greater than 20% that were not detected during the previous inspections or have previously detected imperfections that have increased more than 10% wall penetration, and

b. No more than 3 of the tubes inspected exceed the plugging limit, plant operation may resume after performance of the corrective action in Specification F.

4. If, in the inspections performed under Specification B,

a. More than 10% of the tubes inspected have imperfections greater than 20% that were not detected during the previous inspections or have previously detected imperfections that have increased more than 10% wall penetration, or

b. More than 3 of the tubes inspected exceed the plugging limit, the situation shall be reported to the Commission in accordance with Technical Specification 6.6 for approval of the proposed remedial action.

5. The results of inspections performed under specifications A or B for all tubes in service which have defects below the F* distance shall be reported to the Commission in a Special Report pursuant to Technical Specification 6.9.2 at least seven days prior to the resumption of plant operation. The report shall include:

a. Identification of applicable tubes, and

b. Location and size of the degradation.

6. If in the inspections performed under Specification C.1, wear rates are observed at AVB intersections which are inconsistent with the 50% plugging criterion, the situation shall be reported to the Commission in accordance with Technical Specification 6.6 for approval of the proposed remedial action.

7. If in the inspections performed under Specification C.2 progression of the denting process is observed to be recurring, the situation shall be reported to the Commission in accordance with Technical Specification 6.6 for approval of the proposed remedial action.

F. CORRECTIVE ACTION All leaking tubes, defective tubes, and tubes with imperfections exceeding the plugging limit shall be repaired or plugged.

BASIS:

The Surveillance Requirements for inspection of the steam generator tubes ensure that the structural integrity of this portion of the Reactor Coolant System will be maintained. The program for inservice inspection of steam generator tubes is based on 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 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 fou'nd 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 (primary-to-secondary leakage =.3 gallons per minute 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.3 gpm per steam generator can readily be detected by radiation monitors of steam generator blowdown. Leakage in excess of this limit will require shutdown during which the leaking tubes will be located and plugged and additional inspections performed.

If a defect should develop in service, it will be found during scheduled inservice steam generator tube examinations.

Plugging will be required for all tubes with imperfections exceeding the plugging limit of 50% of the tube nominal wall thickness, except where sleeves are installed, in which case the plugging limit is 40% of the nominal sleeve wall thickness. A plugging limit of 50% for tubes and 40% for sleeves ensures that defects will not occur between inspection intervals. Tubes with defects below the F*

distance may remain in service, provided there are no indications of cracking in the F* distance. The F* distance is 1.0 inches and includes a safety factor of 3 to tube pullout under normal operating conditions and a 0.25 inch eddy current measurement uncertainty.

The results of tube ID gauging and dent detection conducted in San Onofre Unit I steam generators demonstrate that the denting process has been arrested. Continuing assurance of this condition can be provided by performing a program of limited tube ID gauging and dent detection in either steam generator A or C on a refueling outage frequency. Adequate surveillance of denting related tube restrictions can be maintained at refueling intervals by noting any new restrictions during the conduct of general surveillance and AVB inspections and by gauging tubes which have previously been noted as being restricted. Progression of denting can also be monitored in either steam generator A or C by evaluating third and fourth support plate denting data obtained from the general surveillance and AVB inspections as well as from the ID gauging program and comparing these results with those of previous inspections.

The results of AVB area inspections conducted in San Onofre Unit 1 steam generators demonstrate that AVB modifications installed during the Cycle VI refueling outage were successful in eliminating significant growth of tube wall penetration indications at AVB locations. Continuing assurance of this condition can be provided by performing U-bend inspections at refueling outage intervals of tubes having wall penetration indications in excess of 30% at AVB locations.

Eddy Current Test (ECT) Program For Tubesheet Roll-Region Flaw Identification San Onofre Unit 1 The ECT inspection program in use at San Onofre Unit 1 includes the following features:

1. A "MIZ-18" data acquisition system, and multifrequency data analysis with a "DDA-4" data analysis system is being used.

2. Bobbin-probe tests of the tubes in the steam generators as required by Technical Specifications.

3. Bobbin-probe tests of additional tubes in regions of previously detected degradation.

4. Tests with special probes when appropriate to enhance inspection results.

5. Independent data analysis and conservative resolution of discrepancies by experienced Level III analysts is utilized.

6. The use of ECT data analysts qualified on a plant-specific basis.

Roll-Region Flaw Identification When a review of ECT data from the last inspection revealed distorted signals in a few tubes on the inlet end in the transition zone between the rolled portion of the tube and the unexpanded tube, the following program was implemented for the current outage.

1. The roll-region of the inlet end of 100% of the non-sleeved tubes in service was inspected with a bobbin probe.

2. The roll-region of the outlet end of 31% of the tubes in service were inspected with a bobbin probe. In addition 4% of the sleeves in service (including the roll and roll transition) were inspected with a bobbin probe and a cross-wound probe as part of the Technical Specification inspection scope.

3. All flaw indications and distorted or questionable signals were further evaluated using a rotating pancake coil (RPC) probe.

4. Evaluation of the results of these inspections demonstrated that roll-region flaws are limited to the inlet end of non-sleeved steam generator tubes.

5. All tubes with flaws in the roll transition zone were removed from service by plugging. Further, if any tube contained a questionable signal which was not positively resolved by the bobbin-probe or RPC-probe inspections, it was removed from service as a conservative corrective measure.

-2

6. The steam generator vendor was requested to determine the minimum length of roll acceptable for the San Onofre, Westinghouse Model 27, steam generators. This value was determined to be 0.75 inches plus an allowance for ECT error as it had been for the Haddam Neck Unit which has the same model steam generators.

7. Special probes, identical to those used at Haddam Neck in September 1987, were used to determine if flows in the roll-region were within the uppermost inch (0.75 inches + 0.25 inch for eddy current error) of the sound roll.

Further, the same contractor, CONAM Inspection, and the same procedures used at Haddam Neck were used to evaluate flaw locations.

8. All tubes with flaws in the uppermost inch of sound roll and the roll transition zone were removed from service. This resulted in the plugging of 7, 59, and 81 tubes in steam generators A, B and C respectively.

Further, 2, 2 and 40 tubes in steam generators A, B and C respectively, remain in service with flaws below the uppermost inch of sound roll.

As discussed above, the San Onofre Unit 1 ECT inspection program utilizes practices that go well beyond Technical Specification requirements and Regulatory Guide 1.83 provisions. This provides a high level of assurance that all defects or significant flaws have been identified and removed from service.

Future Roll-Region ECT Programs Future roll-region inspection programs at the San Onofre Unit 1 will include the program described above, or the equivalent, for unflawed tubes.

In addition, future inspection programs at the San Onofre Unit 1 will continue to feature the prudent, conscientious inspection programs and the proactive safety philosophy currently being followed by Southern California Edison and will include the following practices:

1. Assessment of new developments regarding the San Onofre Unit 1 inspection experience, and applicable industry inspection experience.

2. Assessment and evaluation of the San Onofre Unit 1 ECT results to define the nature and mechanism of the tube degradation processes.

3. Special inspections and examinations, including tube removal/destructive examination, as appropriate, to ensure that the nature and mechanism of the tube degradation process is accurately defined.

4. Application of appropriate ECT equipment technology, for defining tube degradation conditions known to exist in the San Onofre Unit 1 steam generators or similar PWR steam generators.

5. Utilization of a data analysis program to provide a high level of assurance that all significant flaws are properly identified.

6. Utilization of an inspection strategy that provides a high level of assurance of identification of all significant defects, as appropriate.