ET 23-0006, CFR 50.55a Request Number CI3R-01 for the Third Containment Inservice Inspection Program Interval for Proposed Alternative Frequency to Containment Unbonded Post-Tensioning System Components

CFR 50.55a Request Number CI3R-01 for the Third Containment Inservice Inspection Program Interval for Proposed Alternative Frequency to Containment Unbonded Post-Tensioning System Components

ML23137A328
Person / Time
Site:	Wolf Creek
Issue date:	05/17/2023
From:	Boyce M Wolf Creek
To:	Office of Nuclear Reactor Regulation, Document Control Desk
References
ET 23-0006
Download: ML23137A328 (1)

Text

Michael T. Boyce Vice President Engineering May 17, 2023 ET 23-0006 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001

Subject:

Docket No. 50-482: 10 CFR 50.55a Request Number CI3R-01 for the Third Containment Inservice Inspection Program Interval for Proposed Alternative Frequency to Containment Unbonded Post-Tensioning System Components Commissioners and Staff:

Pursuant to 10 CFR 50.55a(z)(1), Wolf Creek Nuclear Operating Corporation (WCNOC) hereby requests Nuclear Regulatory Commission (NRC) approval of 10 CFR 50.55a Request Number CI3R-01 for the third ten-year interval of WCNOCs Containment Inservice Inspection (CISI)

Program.

The enclosure requests an alternative inspection frequency from 5 to 10 years from the requirements of Section XI, Subsection IWL-2420(a) in accordance with IWL-2520 of the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel (BPV) Code.

The proposed alternative is for the unbonded post-tensioning system associated with the containment structure at Wolf Creek Generating Station (WCGS).

WCNOC requests approval by December 18, 2023, to allow appropriate time for planning containment related inspection work.

This letter contains no commitments. If you have any questions concerning this matter, please contact me at (620) 364-8831 x8687, or Dustin Hamman at (620) 364-4204.

Sincerely, Michael T. Boyce P.O. Box 411 l Burlington, KS 66839 l 620-364-8831

ET 23-0006 Page 2 of 2 MTB/jkt

Enclosure:

Relief Request Serial # CI3R-01, Proposed Alternative in Accordance with 10 CFR 50.55a(z)(1) for Inservice Inspection of the Containment Post-Tensioning System Components.

cc: S. S. Lee (NRC), w/e R. J. Lewis, (NRC), w/e G. E. Werner (NRC), w/e Senior Resident Inspector (NRC), w/e

Enclosure to ET 23-0006 Wolf Creek Nuclear Operating Corporation (WCNOC)

Wolf Creek Generating Station, Unit 1 Relief Request Serial # CI3R-01 Proposed Alternative in Accordance with 10 CFR 50.55a(z)(1) for Inservice Inspection of the Containment Post-Tensioning System Components

Relief Request Serial # CI3R-01 Enclosure to ET 23-0006

1. ASME Code Component(s) Affected:

Code Class: CC

Reference:

IWL-2420, IWL-2520, Table IWL-2500-1 Examination Category: Table IWL-2500-1, Category L-B Item Number: L2.10, L2.20, L2.30, L2.40, and L2.50

Description:

Examination of Unbonded Post-tensioning System Component Number: Wolf Creek Generating Station (WCGS) Unit 1 Concrete Containment Building

2. Applicable Code Edition and Addenda

The 2013 Edition of the ASME Code,Section XI is applicable during the Third Containment Inservice Inspection Interval, which began on September 10, 2018 and is currently scheduled to end on September 9, 2028.

3. Applicable Code Requirements

IWL-2420(a) requires that Unbonded posttensioning systems shall be examined in accordance with IWL-2520 at 1, 3, and 5 years following the completion of the containment Structural Integrity Test and every 5 years thereafter.

4. Reason for Request

4.1 ASME Section XI requires periodic visual examination of the Reactor Building concrete as well as visual examination and physical testing of the post-tensioning system. The examinations and testing performed to-date have indicated that the post-tensioning system is performing well and is expected to maintain its safety-related function through the period of extended operation. This relief request proposes to perform only the visual examination of the concrete containment and accessible steel hardware visible without tendon cover removal during the 40th year surveillance. Physical testing of the post-tensioning system would be performed only if visual examination results indicate a need for such testing as determined by the Responsible Engineer (IWL-2320). The 40th year physical surveillance of the post-tensioning system is required to be performed between December 18, 2023 and December 18, 2025. The 40th year visual examination of the concrete accessible surfaces and tendon end caps is also scheduled to be performed during this time. This one-time deferral of the physical testing of the post-tensioning system will continue to provide an acceptable level of quality and safety based on the projected performance of the post-tensioning system and implementation of physical testing should visual examination results indicate a need for such testing.

4.2 While this relief request is based on maintaining an acceptable level of quality and safety, there are additional benefits to deferring physical testing one surveillance cycle. Physical testing requires exposing personnel to industrial safety hazards.

Removing the tendon end caps and load testing or detensioning/tensioning the tendons also unnecessarily cycles the tendons and exposes the system to an unsealed environment during testing. Below are specific hazards and undesirable conditions that would be eliminated by the proposed alternative:

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Relief Request Serial # CI3R-01 Enclosure to ET 23-0006

1. Most tendons are located at heights well above ground level that requires working at heights and the inherent risks associated with such work.

2. This work is often performed from hanging platforms open to outside weather conditions. These platforms must be moved to a parked location in order for personnel to exit the platforms.

3. This work involves the use of high-pressure hydraulics.

4. Some post-tensioning system examinations and tests are performed in the vicinity of high energy plant systems.

5. This work requires working with solvents and hot petroleum products and associated fumes.

6. This work involves the use of containers and pressurized lines filled with heated corrosion protection medium (grease).

7. This work is performed in the vicinity of high levels of stored elastic energy

(> 1 million foot-pounds) in the tendons. Sudden rotation during force measurement has resulted in high-speed shim ejection at some plants.

8. This work involves handling of heavy loads (test equipment) that also exposes plant equipment to hazards as well as the involved personnel to hazards.

9. Performing examination/testing on a reduced frequency reduces the repetitive loading required for force measurement or detensioning and retensioning.

10. Eliminating tendon end cap removal would prevent exposing the tendon hardware to environmental conditions, and will reduce environmental waste (e.g., solvents, used grease, other consumables).

5. Proposed Alternative and Bases for Use:

5.1 Proposed Alternative In lieu of the requirement of IWL-2420(a), the concrete containment unbonded post tensioning system shall be examined in accordance with IWL-2520 at 35 years following the completion of the containment Structural Integrity Test and every 10 years thereafter. This alternative would eliminate the IWL-2520 examinations currently scheduled during the Third Containment Inservice Inspection Interval at 40 years (+/- 12 months) following the completion of the containment Structural Integrity Test. The examination and physical testing requirements of Section XI Table IWL-2500-1 Item Numbers L2.10, L2.20, L2.30, L2.40, and L2.50 will only be performed at 40 years (+/- 12 months) following the completion of the containment Structural Integrity Test if the Responsible Engineer determines that conditions detected during the General Visual Examination and Detailed Visual Examination performed on containment accessible concrete surfaces and tendon end caps in accordance with Table IWL-2500-1, Examination Category L-A indicate possible degradation of tendon hardware. Tendon physical testing, if required, shall be completed no later than December 18, 2025. Examples of conditions that could require removal of the tendon end cap and further examination per Item Numbers L2.10, L2.20, L2.30, L2.40, and L2.50 are:

• Evidence of possible damage to the enclosed post-tensioning hardware as evidenced by conditions such as end cap deformation found during external visual Page 3 of 16

Relief Request Serial # CI3R-01 Enclosure to ET 23-0006 examination. Conditions observed by removal of the end cap would determine the extent of additional examinations that may be required in accordance with Item Numbers L2.10, L2.20, L2.30, L2.40, or L2.50.

• Active corrosion on a bearing plate or end cap that requires further investigation as determined by the Responsible Engineer in an engineering evaluation.

Evidence of gross leakage of corrosion protection medium will be evaluated and a plan developed for corrective actions as defined in an engineering evaluation documented by the Responsible Engineer.

5.2 Basis for Proposed Alternative The basis for use of the above proposed alternative is provided below, and is supported by the excellent examination history for this plant. A summary of the examination history is provided below.

5.2.1 Summary of IWL-2522 Examination Results (Item Number L2.10)

Tendon Prestress Forces and Force Trending Figures shown in Attachment 2 illustrate the tendon force measurement history.

The data shows that tendon force measurements have remained above the minimum required value (MRV), and that the predicted mean tendon forces for each type of tendon will remain above the required minimum design prestress force well beyond the end of the current operating license.

Tendon Elongation Measured tendon elongations have met the applicable acceptance standards during all surveillances.

5.2.2 Summary of IWL-2523 Examination Results (Item Number L2.20)

Tendon Wire Visual Examinations Visual examination of all wires removed from tendons since initial tendon installation have shown no signs of corrosion or physical damage.

Tendon Wire Tension Testing Results of tension tests on all wires removed from tendons have met applicable acceptance standards, including material specification requirements for ultimate tensile strength ( 240 ksi) and elongation at failure ( 4%).

5.2.3 Summary of IWL-2524 Examination Results (Item Number L2.30)

Tendon Anchorage Area Concrete Examinations Cracking of concrete adjacent to bearing plates has been observed at a number of tendon end anchorages, and crack mapping has been documented when such cracking has been detected. These conditions have all been evaluated as acceptable, are considered typical in structures of this age, and do not represent evidence of abnormal degradation of the containment or its post-tensioning system.

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Relief Request Serial # CI3R-01 Enclosure to ET 23-0006 Tendon Anchorage Hardware and Bearing Plate Examinations Visual examinations of tendon anchorage hardware (anchorheads, shims, buttonheads, and bearing plates) have met the applicable acceptance standards, except as noted below. Cracking has not been detected in any tendon anchorage component (anchorhead, shims, bearing plates).

Broken, missing, or protruding wires have been detected in the following tendons:

Year 5 Surveillance:

• Tendon 7BA (shop end) was found to have one protruding wire previously not reported at installation.

• Tendon 20AC (field end) had one protruding wire previously reported at installation. This wire was removed for testing after detensioning and continuity test. Results of wire examinations and tests were acceptable.

Year 25 Surveillance:

• Tendon V7 (shop end) had two broken wires and five protruding buttonheads after a lift-off of the tendon was performed. These conditions were evaluated and accepted.

The affected wires were on the periphery of the anchorhead and were damaged during the surveillance when the shim stack rotated and contacted these wires.

• Tendon V65 (shop end) had two broken buttonheads, discovered after a lift-off of the tendon end. These conditions were evaluated and accepted. The affected wires were located on the periphery of the anchorhead and were damaged during the surveillance when the shim stack rotated and contacted these wires.

Year 30 Surveillance:

• Tendon 40BA (field end) had one buttonhead protruding 1/2.

Instances of broken wires or protruding buttonheads have been attributed to conditions that occurred during initial installation of tendon wires (e.g.,

malformed buttonheads), or as a result of tendon retensioning. The number of broken, missing, or protruding wires identified above are a very small fraction of the total number of button-headed wires examined since initial installation. These conditions have not been attributed to degradation of tendon wires and have an insignificant effect on the performance of the containment post-tensioning system.

5.2.4 Summary of IWL-2525 Examination Results (Item Numbers L2.40 and L2.50)

Tendon Corrosion Protection Medium (CPM) Analyses Results of tendon corrosion protection medium tests have met acceptance standards during all examinations.

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Relief Request Serial # CI3R-01 Enclosure to ET 23-0006 Tendon Free Water Collection and Analysis Free water has only been detected in a single tendon end cap (Tendon V30) during the 20th Year surveillance. The volume of free water detected was reported to be less than one ounce.

5.2.5 Summary of IWL-2526 Requirements (Item L2.40)

There have been several surveillances during which the difference in the amount of CPM installed and that removed from a tendon exceeded 10% of the tendon net duct volume (3rd, 10th, and 20th Year Surveillances). In these cases, an evaluation was performed to document the acceptability of these conditions, and tendons have been refilled to ensure that tendon wires and anchorage components are adequately protected from corrosion.

Unacceptable anchorage or tendon conditions resulting from inadequate grease coverage have not been detected.

5.2.6 Additional Information Tendon Corrosion Protection Medium (CPM) Leakage Tendon CPM leakage has not been a significant issue at WCGS. Only a few instances of CPM leakage have been detected at tendon end caps during IWL examinations.

Wolf Creek Generating Station has implemented a condition monitoring program that requires a walkdown of the containment tendon gallery to identify and monitor tendon grease leakage from tendons anchored to the underside of the containment base mat. Examinations performed in accordance with this condition monitoring program from 2016 to 2022 have not detected any significant grease leakage.

Although examinations performed in accordance with IWL-2526 have detected some tendon sheaths where the grease void volume exceeded procedural acceptance standards, these void volumes have not been attributed to significant grease leakage from tendons.

Sheathing filler grease void volumes in excess of ASME Code,Section XI, Subsection IWL acceptance standards have been attributed to one or more of the following:

• Thermal contraction of the hot grease initially installed in each tendon sheath.

• Existence of voids between tendon wires that were not completely filled as a result of grease cooling during pumping through relatively cool tendon sheaths and tendon wire bundles.

• Pumping operations that can introduce air into the sheathing filler grease during installation.

Concrete Visual Examinations (Item Numbers L1.11, L1.12)

Examinations of accessible exterior surfaces of the containment concrete in accordance with Table IWL-2500-1, Examination Category L-A have detected some areas where minor concrete repairs have been required.

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Relief Request Serial # CI3R-01 Enclosure to ET 23-0006 These repairs have not been significant and did not require subsequent pressure testing in accordance with IWL-5000.

Detailed visual examination of suspect areas of accessible concrete surfaces, including surfaces adjacent to tendon anchorage areas (limited to hoop tendons) shall continue to be performed in accordance with IWL-2511, IWL-2310(b), and Table IWL-2500-1, Examination Category L-A, Item L1.12 when suspect surface areas are detected during the Category L-A, Item L1.11 examinations.

5.2.7 Summary and Conclusions The results of the inservice examinations conducted at WCGS have demonstrated that the containment post-tensioning system is continuing to perform its intended function and can be expected to do so until well past the March 11, 2045 expiration of the plant operating license. Visual examinations performed every five years in accordance with ASME Section XI, Table IWL-2500-1, Item Numbers L1.11 and L1.12 are sufficient to determine if additional physical testing and examination per Examination Category L-B is required.

For these reasons, WCNOC requests authorization to use the proposed alternative pursuant to 10 CFR 50.55a(z)(1) on the basis that the proposed alternative provides an acceptable level of quality and safety.

6. Duration of Proposed Alternatives:

The proposed alternative is requested for use during the WCGS Unit 1 Third Containment Inservice Inspection Interval.

7.

References:

7.1 ASME Boiler and Pressure Vessel Code,Section XI, 2013 Edition 7.2 Containment Inservice Inspection (CISI) Program Plan, Wolf Creek Generating Station, Interval 3, Document #WCRE-36

8. Precedents

8.1 ADAMS Accession Number ML22124A241. NRC approved dated May 12, 2022.

Palo Verde Nuclear Generating Station Units 1, 2, and 3, Relief Request 67 -

Request for Alternative Frequency to Containment Unbonded Post-Tensioning System lnservice Inspection, dated July 29, 2021 (ML21210A300) 8.2 ADAMS Accession Number ML20287A471. NRC approved dated October 20, 2020. Millstone Power Station, Unit 2, Proposed Alternative Request RR-05-05, Containment Unbonded Post-Tensioning System Inservice Inspection Requirements, dated December 17, 2019 (ML19352B898).

8.3 ADAMS Accession Number ML19182A077. NRC approved dated July 11, 2019.

Vogtle Electric Generating Plant, Units 1 and 2, Proposed ISI Alternative VEGP-ISI-ALT-19-01 for Tendon Inservice Inspection Extension, dated February 18, 2019 (ML19049A017).

8.4 ADAMS Accession Number ML19226A023. NRC approved dated September 19, 2019. Three Mile Island Nuclear Station, Unit 1, Submittal of Relief Request RR-18-01 Concerning Containment Unbonded Post-Tensioning System Inservice Page 7 of 16

Relief Request Serial # CI3R-01 Enclosure to ET 23-0006 Inspection Requirements, dated October 16, 2018 (ML18289A363).

8.5 ADAMS Accession Number ML21134A006. NRC approved dated August 3, 2021. Braidwood Station, Units 1 and 2 (Relief Request I4R-11) and Byron Station, Unit Nos. 1 and 2 (Relief Request I4R-18), Alternative to Containment Unbonded Post-Tensioning System Inservice Inspection Requirements, dated July 24, 2020 (ML20206L135).

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Relief Request Serial # CI3R-01 Enclosure to ET 23-0006 Attachment 1 (Tables)

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Relief Request Serial # CI3R-01 Enclosure to ET 23-0006 Table 1: Regression Input Data - Cylinder Hoop Tendons Page 10 of 16

Relief Request Serial # CI3R-01 Enclosure to ET 23-0006 Table 2: Regression Input Data - Vertical Hoop Tendons Page 11 of 16

Relief Request Serial # CI3R-01 Enclosure to ET 23-0006 Table 3 Wolf Creek Generating Station, Unit 1 Dome Hoop Tendon Liftoff Data Dome Hoop Prestressing Surveillance Surveillance Installation Surveillance Surveillance Surveillance Tendon Date Date Year Net Lockoff Shop End Field End Mean Liftoff Force (kip) Liftoff Force Liftoff Force Force (kip)

(kip) (kip)

H51BA 10/15/1982(1) 02/24/1986 Year 1 1387 1325 1372 1349 H47BA 10/15/1982 (1) 09/03/1987 Year 3 1392 1252 1359 1306 No dome hoop tendons were examined Years 5, - - - -

during these surveillances 10, 15, and 20 H52BA 10/15/1982(1) 08/24/2010(2) Year 25 1397 1256 1325 1291 No dome hoop tendons were examined Years 30 - - - -

during these surveillances and 35 Notes:

(1) The initial installation of all tendons was completed on this date. Using the completion date for all tendon installations will result in a conservative analysis of dome hoop tendon force loss trending.

(2) The 25th Year Surveillance was performed between July 27, 2010 and September 22, 2010.

An average date of August 24, 2010 is used in this table for this tendon.

(3) The minimum required prestress force (MRV) for the dome hoop tendons is 1119 kips.

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Relief Request Serial # CI3R-01 Enclosure to ET 23-0006 Attachment 2 (Figures)

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Relief Request Serial # CI3R-01 Enclosure to ET 23-0006 Figure 1: Cylinder Hoop Tendon Regression Graph Notes:

1. Figure 1 excludes force measurement data from the dome hoop tendons. Dome hoop force measurement data is shown in Figure 3.

2. The minimum design preload for the cylinder hoop tendons is 1227 kips.

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Relief Request Serial # CI3R-01 Enclosure to ET 23-0006 Figure 2: Vertical Tendons Regression Graph Notes:

1. The minimum design preload for the vertical tendons is 1159 kips.

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Relief Request Serial # CI3R-01 Enclosure to ET 23-0006 Notes:

1. Figure 3 was plotted using data obtained from Table 3.

2. Tendon prestress force losses are expected to follow a log-linear curve, similar to that shown in Figure 1. However, the predicted prestress force loss curves in Figure 3 are conservative and are plotted linearly because of the limited amount of data that has been collected since tendon installation.

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