RS-23-066, Containment Post-Tensioning System Inservice Inspection Basis for Proposed Extension of Examination Interval Technical Report

Containment Post-Tensioning System Inservice Inspection Basis for Proposed Extension of Examination Interval Technical Report

ML23123A221
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Site:	LaSalle
Issue date:	05/03/2023
From:	Constellation Energy Generation
To:	Office of Nuclear Reactor Regulation
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LAS RR Technical Report Page 1 of 77 Revision 0 / 20230214

LASALLE COUNTY STATION UNITS 1 & 2

CONTAINMENT POST-TENSIONING SYSTEM INSERVICE INSPECTION

BASIS FOR PROPOSED EXTENSION OF EXAMINATION INTERVAL TECHNICAL REPORT

Report Prepared by:

Howard T. Hill, PhD, P.E. (California Civil Certificate C 22265)

BCP Technical Services, Inc.

Revision 0 / 14 February 2023

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LIST OF ABREVIATIONS ACI American Concrete Institute ANS American Nuclear Society ANSI American National Standards Institute ASME American Society of Mechanical Engineers ASTM American Society for Testing and Materials CMTR Certified Material Test Report CPM Corrosion protection medium EF Elongation at failure FSAR Final Safety Analysis Report kip Kilo-pound (1,000 pounds) ksi Kips per square inch LAS LaSalle County Station LCL Lower confidence limit MRV Minimum required value NRC Nuclear Regulatory Commission ORNL Oak Ridge National Laboratory ppm Parts per million RE Responsible Engineer SIT Structural Integrity Test USNRC United States Nuclear Regulatory Commission UTS Ultimate tensile strength

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LASALLE COUNTY STATION UNITS 1 & 2 CONTAINMENT POST-TENSIONING SYSTEM INSERVICE INSPECTION BASIS FOR PROPOSED EXTENSION OF EXAMINATION INTERVAL TECHNICAL REPORT

Report Prepared by:

Howard T. Hill, PhD, P.E. (California Civil Certificate C 22265)

BCP Technical Services, Inc.

Revision 0 / 14 February 2023

1. PURPOSE, CONTAINMENT / ISI PROGRAM DESCRIPTION AND ORGANIZATION

This report provides the technical evaluation / justification supporting a request for relief to allow alternatives to certain containment Inservice Inspection (ISI) requirements specified in USNRC Regulation 10CFR50.55a (Reference 6.1) and, by reference t herein, American Society of Mechanical Engineers ( ASME)Section XI, Subsection IWL (Reference 6.2). The current LaSalle County Station (LAS) containment ISI program conforms to these regulatory and code requirements with modifications as allowed by approved relief requests.

1.1 Containment Description

The LaSalle County Station is a two-unit boiling water reactor site with Mark II (conical drywell over a cylindrical suppression chamber) prestressed concrete containment s. The essentially identical containment s serve as pressure vessels that form the final barrier (after fuel cladding and the reactor coolant system pressure boundary) against the post-accident release of radioactive material from the reactor core to the outside environment.

The design basis internal pressure for both containments is 45 psig as shown in LAS Final Safety Analysis Report (Reference 6.3) Par. 7.5.2.1.3.a.

The drawing reproduced in Attachment 2 shows a vertical section through a containment and illustrates its principal features.

The containment structures, which are supported by and connected to a conventionally reinforced common base mat, consist of a lower cylinder (suppression chamber) and an upper truncated cone (dry well). The truncated cone drywell, which houses the reactor, is closed at the top by a removable (for refueling access) dished steel head. Concrete extends vertically above the top of the pressure retaining cone (i.e., abov e the juncture of the concrete cone and the steel drywell head) as required by the refueling cavity design.

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A conventionally reinforced diaphragm slab separates the drywell and suppression chamber. The slab is penetrated by a number of open ended ver tical pipes that vent post-accident steam released from the reactor coolant system into the suppression pool.

The concrete cylinder and cone are prestressed in the hoop (circumferential) and meridional (vertical in the cylinder and inclined in the cone) directions.

The cylinder and lower cone are thickened at three equally spaced locations (two in the upper part of the cone) with vertical / inclined buttresses that provide anchorage for the hoop prestressing t endons. Buttresses are centered at Azimuths 60°, 180°, 300 ° and 0°.

The 180° buttress extends from the base mat to El. 818 ft on the outside face of the concrete extension above the top of the cone). The 60° and 300° buttresses extend from the base mat to El. 794 ft on the side of the cone. The 0° buttress extends from El. 794 ft to El. 818 ft.

Buttresses are identified by letter designations as follows.

Unit 60° Buttress 180° Buttress 300° Buttress 0° Buttress 1 A B C D 2 E F G H

Outward projections (lands) of each containment wall at various elevations provide support for reactor building floors as well as anchorage for the subgroup C (see below) vertical tendons.

Major containment dimensions (rounded to the nearest 0.1 ft) from Exelon Drawings S-831 (Reference 6.4) and 1-CISI-2000, Sheet 1 (Reference 6.5) are listed below. These are shown for general information only and are not intended to provide a detailed description of the structure.

• Top of base mat elevation: 673.3 ft (above plant datum zero reference)

• Top of cylinder elevation at the inside cylinder -cone transition: 744.2 ft

• Top of cone elevation at the inside face of the concrete extension: 815.2 ft

• Base mat thickness: 7.0 ft

• Cylinder inside radius: 43. 3 ft

• Cylinder wall thickness: 4.0 ft

• Inside height from base mat top to cylinder -cone transition: 70.9 ft

• Cone inside height above transition: ~7 0 ft (scaled)

• Cone inside radius at top of concrete: ~14.5 ft (scaled)

• Cone wall thickness: 6.0 ft LAS RR Technical Report Page 5 of 77 Revision 0 / 20230214

The cylinder and cone are post-tensioned with 90 wire BBRV (wires anchored by cold formed button heads) tendons. The ASTM A421 ( Reference 6.6) wires have a diameter of 0.250 inches and a specified minimum ultimate tensile strength of 240 ksi.

Hoop prestressing consists of 188 tendons distributed as shown on Exelon Drawing 1-CISI-2000, Sheet 2 (Reference 6.7 ) and as described below.

• Three overlapping subgroup s, each with 58 tendons that span 240° plus the width of a buttress, provide prestress ing over the full height of the cylinder as well as the lower part of the cone below El. 794 ft.

• Two overlapping subgroups, each with 7 tendons that span 360° plus the width of a buttress, provide prestressing in the upper part of the cone between El. 794 ft and the buttress tops at El. 818 ft.

Hoop tendons are identified by an alphameric code with the form H#XX or H##XX where

1. (or ##) is a number indicating t he sequential level above the base mat and XX (or X for those tendons above El. 794 ft) identifies the buttresses (or buttress) at which the tendon ends are anchored.

Wall vertical pre-stressing consists of 120 t endons anchored at the bottom of the base mat and at several levels on / above the cone as shown on Exelon Drawings 1-CISI-2000, Sheets 1, 4, 5A, 5B and 5C (References 6.5, 6.8, 6.9, 6.10 and 6.11) and as described below. Access to the lower ends of all vertical tendons is provided by a tunnel (the tendon gallery) below the base mat.

Subgroup A has 30 vertical tendons anchored in access wells at the top of the concrete extending above the cone. Top of concrete elevation at 25 of the anchorage locations is 843.5 ft (the refueling floor elevation). The remaining 5 tendons are anchored where the top of concrete is at El. 823.5 ft (in the refueling cavity ). Tendon anchorage hardware is protected from moisture intrusion by a bolted cap. The access wells are sealed by gasketed cover plates.

Subgroup B has 30 tendons anchored at the top of the cone (El. ~815 ft ; the anchorage area is inclined, sloping down toward the center of the cone). Anchorage hardware is enclosed in caps welded to the drywell cone skirt. Since the caps are welded in place, these anchorages are exempt from periodic examination requirements.

Subgroup C has 60 tendons anchored at the land supporting the El. 786 ft reactor building floor slab. A nchorages are in access wells; anchorage enclosure and well sealing are as described for the Subgroup A tendons.

Vertical tendons are identified by an alphameric code of the form V#X or V##X for Unit 1 and V20#X or V2##X for Unit 2 where # (or # #) is a sequential tendon number increasing clockwise (as viewed looking down) from the 0° azimuth and X (A, B or C) designates the subgroup.

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Tendon ducts an d anchorage end caps are filled with a microcrystalline wax (a grease-like material) that serves to prevent moisture intrusion as well as provide protection against corrosion.

Tendon forces decrease with time as a result of elastic shortening (the effect of sequential tensioning operations), concrete shrinkage, concrete creep and pre-stressing wire relaxation losses. Mean tendon forces must remain above specified minima to ensure that concrete remains in a state of membrane compression under postulated accident pressure and temperature conditions. Minimum required group mean tendon forces, as specified in Par. B.4.7.6 of the Inservice Inspection Program for Post -Tensioning Tendons (Reference 6.12), are shown below.

• Hoop Tendon Group: 575 kip

• Vertical Tendon Group: 600 kip

1.2 Containment ISI Program Summary Description

Continuing structural 1 integrity of the LAS containments is verified through regular examinations and tests (also referred to as surveillances) performed in accordance with the requirements of USNRC Regulation 10CFR50.55a ( Reference 6.1) and, by reference therein, ASME Section XI, Subsection IWL ( Reference 6.2) as modified by approved relief requests. The C ontainment ISI program, as detailed in Reference 6.12, requires visual examination of the entire accessible concrete surface and testing and / or visual examination of a sampling of tendons. Samples for each unit are selected from s eparate populations as defined below.

• Hoop tendons

• Originally installed vertical tendons

• Vertical tendons replaced in 2003-2004

Hoop and originally installed vertical tendon samples include one tendon common to consecutive surveillances and a specified number 2 randomly selected from populations that exclude those previously examined.

Replaced tendon samples do not include common tendons.

Surface visual examinations follow the applicable guidelines given in the ACI reports referenced in Subsection IWL and are not consider ed further in this report which addresses only the prestressing system.

1 Containment liner ISI, performed to assess leak tight integrity, is covered by Subsection IWE and is not addressed in this technical report.

2 Sample size may increase as a result of conditions found during the surveillance.

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Examination and testing of the post-tensioning system currently follows ASME Boiler and Pressure Vessel Code (200 7 Edition with 2008 Addenda)Section XI, Subsection IWL requirements as modified by approved relief requests. Examinations and tests,

performed on a random sampling of tendons 3, are described below.

• Visual Examination and Testing Intervals Detailed visual examination of tendon end anchorage hardware 4 and concrete surrounding the bearing plate as well as collection and testing of corrosion protection medium (CPM) and free water, if any, are performed at 5-year intervals for each of the two units.

Tendon lift-off force measurements and wire extraction / testing are performed at 5-year intervals with the tests alternating between the two units; i.e., Unit 1 tests are performed once every 10 years and Unit 2 tes ts are performed once every 10 years.

• Visual Examination Anchorage area concrete and post -tensioning system hardware are visually examined for the following indications of damage or degradation.

o Cracking or spalling at the surface of concrete adjacent to bearing plates.

o Accumulation of water in end caps.

o Lack of corrosion protection medium (CPM) coverage on anchor heads, shims and buttonheads.

o Corrosion on bearing plates, anchor heads, shims and buttonheads.

o Protruding or missing buttonheads.

o End anchorage component cracking or distortion.

• Tendon Force Measurem ent and Wire Testing The force at each end of the sample tendon is measured by applying jacking force just sufficient to loosen the shim stack (thus ensuring that all tendon load is carried by the calibrated jacks ).

Also, a single wire (in addition to any found to be broken in service) is removed from one tendon in each group, examined for damage and corrosion and tested to determine yield strength, ultimate strength and elongation at failure.

3 One tendon in each group is designated as a common tendon and examined / tested during each surveillance.

4 The upper ends of Subgroup B vertical tendons are enclosed by caps welded to the drywell cone skirt and are designated as inaccessible for examination in accordance with ASME Section XI Par. IWL-2020(b).

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• CPM Sampling and Testing Samples of CPM are collected at eac h end of each tendon and analyzed for water content, concentration of corrosive ions and reserve alkalinity.

• Free Water Collection and Testing Free water, if found in sufficient quant ity for sampling, is collected and tested to determine pH.

1.3 Report Organization

The remainder of this report consists of the following 7 parts and two attachments.

Part 2 - Summary of Proposed Alternatives Part 3 - Background of Current ISI Requirements and Basis for Proposed Alternatives Part 4 - LAS Examination History and Results Analysis / Evaluation Part 5 - Overall Summary, Conclusions and Recommendations Part 6 - References Part 7 - Tables and Figures Attachment 1 - Trend Line Parameter and Confidence Limit Value Formulae Attachment 2 - Containment Vertical Cross-Section Drawing

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2.

SUMMARY

OF PROPOSED ALTERNATIVES

The following alternatives to the currently approved Containment ISI program are proposed and evaluated in this report.

• Extend the interval for visual examination of Unit 1 and Unit 2 end anchorage areas from 5 years to 10 years as shown in the schedule below.

• Extend the interval for Unit 1 and Unit 2 post-tensioning system examinations that include tendon force measurements from 10 years to 20 years as shown in the schedule below.

Proposed Tendon Surveillance Schedule (includes the four most recent Unit 1 and Unit 2 surveillances for reference)

Units 1 & 2 Year Visual Examination, CPM Sampling Tendon Force

& Testing and Free Water Measurement Collection & Testing Unit 1 Unit 2 Unit 1 and Unit 2 2003 Performed Performed Performed 2008 Performed N/A Performed 2013-14 Performed Performed N/A 2019 Performed N/A Performed 2028 a Perform Perform N/A 2038a Perform N/A Perform 2048 a Perform Perform N/A 2058a Perform N/A Perform

Note a: For scheduling purposes, each future surveillance is considered to be due at mid-year and must be performed between 30 June of the year prior to the year shown and 30 June of the year following the year shown.

• Eliminate the requirement for de -tensioning / re-tensioning of tendons, wire removal and wire sample testing.

• Limit initial corrosion protection medium laboratory tests to that which determines absorbed water content; perform the corrosive ion and reserve alkalinity tests only on those samples that have a water content above the acceptance limit, are collected at an anchorage where free water and / or corrosion is found or if specified by the Subsection IWL Responsible Engineer 5 (RE).

5 A registered professional engineer having qualifications and responsibilities as identified in ASME Section XI Par. IWL-2330.

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The above proposed alternatives relate only to pre-stressing tendon tests and the associated examinations that require close -in access to tendon end anchorage areas.

Visual examination of the exposed areas of the containment concrete surface, exposed areas of the tendon bearing plates and tendon end caps will continue to be performed at 5-year intervals in accordance with past practice.

This report and the Relief Request that it supports address only proposed alternatives to the Inservice Inspection requirements covered by ASME Section XI, Subsection IWL Table IWL-2500- 1 Examination Category L-B. The Examination Category L-A concrete surface examinations will continue to be performed in accordance with Subsection IWL as modified by approved relief requests. Containment liner and penetration assembly examinations and tests will continue to be implemented in accordance with Subsection IWE as modified by approved relief requests.

Based on the evaluation of past examination results as discussed in subsequent sections of this report, it is concluded that implementation of the alternative Containment ISI program recommended herein will provide an equivalent level of assurance that the structural integrity of the Unit 1 and Unit 2 containment s is maintained at the highest level.

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3. BACKGROUND OF CURRENT ISI REQUIREMENTS AND BASIS FOR PROPOSED ALTERNATIVES

Containment Inservice Inspection (also referred to herein as surveillance and Inservice examination) requirements originated with the issuance of Regulatory Guide 1.35 (Reference 6. 13) in the early 1970s and are currently mandated by ASME Section XI, Subsection IWL, which is incorporated by reference into USNRC regulation 10CFR50.55a. A brief history of current requirement development is summarized in Sections 3.1, 3.2 and 3.3 bel ow. The basis for the proposed alternative program is discussed in Section 3.4.

3.1 Regulatory Guide 1.35

In February 1973 the U. S. Atomic Energy Commission issued the initial version of Regulatory Guide 1.35, Inservice Surveillance of Ungrouted Tendons in Prestressed Concrete Containment Structures. This document, drafted prior to the completion of the first pre-stressed concrete containment structures and well before the accumulation of prototype containment pre-stressing system performance data, d escribed the following as an acceptable basis for system examinations.

• Examination schedule - 1, 3 and 5 years after the pre-operational structural integrity test and every 5 years thereafter.

• Examination sample size - 6 dome, 5 vertical and 10 hoop tendons.

• Wire / strand extraction - one wire / strand from a tendon in each group ( dome, vertical, hoop); extraction requires de-tensioning.

• Visual examinations for damage, deterioration and corrosion - corrosion protection medium, end anchorage hardware, anchorage area concrete and extracted wires

/ strands.

• Physical tests - tendon liftoff force and extracted wire / strand strength and elongation at failure.

The regulatory guide does not discuss the basis for the examination interval, the sample size or the various tests and examinations to be included in an acceptable program (t hese represent consensus opinions reached among the individuals involved in guide development). Also, it does not address the possible need for changes as future operating experience accumulates.

Subsequent revisions to R egulatory Guide 1.35 added procedures for corrosion protection medium chemical analyses (added in Revision 3), substantially changed the sampling process and included numerous other additions and clarifications but retained the examination interval and wire / strand testing program as described in the original 1973 issue. The final revision, Revision 3, was issued in July 1990.

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Regulatory Guide 1.35 was withdrawn in August 2015 following the incorporation, by reference, of ASME Section XI, Subsection IWL into US NRC regulation 10CFR50.55a.

3.2 ASME Section XI / Subsection IWL

The 1989 edition of the ASME Boiler and P ressure Vessel Code included in Section XI, for the first time, Subsection IWL which provided comprehensive and detailed requirements for a concrete C ontainment ISI program. During the development of Subsection IWL 6, which commenced in the 1970s, it was concluded that US NRC acceptance and endorsement (by reference in 10CFR50.55a) of the document would be expedited if departures from the program described in R egulatory Guide 1.35 were minimized. For this reason, the examination interval, strength / elongation testing of wire

/ strand samples and relatively extensive chemical testin g of corrosion protection medium samples mandated in Subsection IWL are unchanged from those identified in R egulatory Guide 1.35, Rev. 3.

Subsection IWL has been revised numerous times since its initial incorporation into ASME Section XI in 1989. None of these revisions have altered the examination interval or the basic requirement to test wire / strand and corrosion protection medium sampl es.

3.3 USNRC Regulation 10CFR50.55a

The 1996 amendment to 10CFR50.55a incorporated, by reference and with specified exceptions and additions, the ISI requirements given in the 1992 edition, with 1992 addenda, of ASME Section XI, Subsection IWL. Subsequent amendments have referenced later editions / addenda of Subsection IWL but none have addressed changes to either the examination interval or the requirements for testing wire / strand and corrosion protection medium samples.

3.4 Basis for Proposed Deviations / Relief from 10CFR50.55a and Subsection IWL Requirements

[Note: This section of the technical report includes a generalized summary of post -

tensioning system performance observed during 4 decades of periodic examinations conducted at 24 U. S. nuclear plant sites with 41 pre-stressed concrete containments. It is intended to show that most containment post -tensioning systems are continuing to perform well and that, in general, system examination intervals could be significantly increased without compromising safe operation of the plant.]

6 The author of this technical report has been a member of the IWL working group since the 1970s (when it was still being developed as an addition, CC-9000, to ASME Section III, Division 2) and served as chair of the working group during its later development and much of the period leading up to its incorporation into ASME Section XI in 1989.

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The material covered in this section is based on the report authors experience as described below.

• Participation in containment post -tensioning system examinations at U. S. and foreign sites.

• USNRC funded research, performed under contract to ORNL, on age-related decrease in pre-stressing force and other age-related effects at ~20 U. S.

containments.

• Four decades of interacting with fellow members of the IWL working group.

• Review of USNRC informational bulletins and generic letters.

• Review of system performance history in connection with preparation of program basis documents for license renewal applications.

• Forecasting tendon forces in connection with the preparation of minimum requi red pre-stressing force calculations.

• Work on a USNRC-funded project to review and recommend updates to Regulatory Guides 1.35, 1.35.1 and 1.90, which address Inservice Inspection of pre-stressed containments.

• A three-year association with the Crystal River 3 containment repair project; assignments included evaluating the condition of tendons not affected by the repair work.

The following summary is qualitative; specific references are not cited as the bases for the generalized statements regar ding post-tensioning performance.

As noted in Sections 3.1, 3.2 and 3.3 above, the examination intervals and wire / strand testing addressed in the 1973 original issue of R egulatory Guide 1.35 are now, almost 50 years later, still incorporated effectively unchanged into the current edition of ASME Section XI, Subsection IWL.

In addition, the current edition of ASME Section XI, Subsection IWL specifies corrosion protection medium chemical testing procedures that are effectively unchanged from those described in Regulatory Guide 1.35, Revision 3 (issued in July 1990).

The results of unbonded post-tensioning system examinations performed over the last 4 decades at 24 domestic sites with a total of 41 pre-stressed containments (listed in Table

1) provide ample evidence, as discussed below, that prescriptive requirements currently in Subsection IWL are, in many cases, overly conservative. These industry results as well as LAS plant-specific operating experience as subsequently discussed, support the implementation of alternative programs with fewer prescriptive requirements.

Reducing prescriptive requirements, as addressed in this report and the associated Relief Request that it supports, has the following advantages.

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• It reduces personnel and equipment safety hazards associated with working at heights, handling of heavy loads, working with high-pressure hydraulic equipment, working close to tendon end anchorages that can suddenly release stored mechanical energy, working with hot (>150 °F) corrosion protection medium that is under pressure, working in proximity to high-energy plant systems and working in radiation controlled areas.

• It reduces the potentially deleterious cycling of tendon loads that occurs during de-tensioning / re-tensioning for wire removal and to a lesser extent during the measurement of lift -off forces.

The technical justification for the proposed deviations is based on operating experience accumulated over the past 4 decades at the 24 domestic plants with containments having unbonded post -tensioning systems and, in particular, the operating experience documented during the post -tensioning system examinations performed at LAS. The general conclusions regarding post -tensioning system performance are listed below.

Conclusions specific to LAS are addressed in detail in subsequent sections of this report.

3.4.1 Pre-Stressing Force Trend

Containment design criteria typically require that the post -tensioning system provide sufficient pre-stressing force at the end of 40 years (period of initial licensure considered to be the plant operating lifetime when design work on existing plants comm enced) to maintain membrane compression in the walls and dome under specified accident conditions.

Post-tensioning system design was based on a postulated linear decrease in pre-stressing force with the logarithm of time (log-linear decrease). The log-linear function was selected as this provided a reasonably good fit to the results of relatively short -term creep, shrinkage and relaxation tests and was consistent with expectations based on the calculated response of theoretical models that represent mat erials as an assemblage of linear springs and dashpots. Concrete creep and shrinkage tests were typically conducted for 180 days and pre-stressing steel relaxation tests for 1000 hours0.0116 days <br />0.278 hours <br />0.00165 weeks <br />3.805e-4 months <br /> (~40 days).

Designing for a 40- year plant operating lifetime required extrapolating concrete test durations by a factor of 80 and steel test durations by a factor of almost 400.

Post-tensioning system examination data have shown, with relative consistency, that the rate of change of pre-stressing force with the logarithm of time tends to decrease with time. Within 20 to 25 years after the completion of pre-stressing operations, the force time trend becomes essentially flat 7. Given this general trend, it can be stated with a high

7 As discussed in Part 4 of this report, scatter of measured tendon forces tends to obscure the true trend of the mean. The conclusion regarding flattening of the trend is based on statistical analysis rather than an observed characteristic of the plotted data.

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degree of confidence that the examination interval may be increased beyond 10 years with no compromise of safety function if the following conditions are satisfied.

• The current group (hoop, vertical, dome, inverted U, as applicable to the containment) mean pre-stressing force computed using both the trend of individual tendon force data acquired to date and the mean of the most recently acquired data exceed the minimum required level by significant margins. The margin deemed significant is established through an evaluation by the Responsible Engineer.

• The forecast group mean pre-stressing forces, determined using the data acquired to date and computed, for conservatism, at the 95% lower confidence limit, remain above the minimum required levels until well past the deadline for completion of the subsequent surveillance.

3.4.2 System Hardware Condition History

Industry wide, there have been relatively few significant issues associated with containment post-tensioning system hardware (tendon wire / strand 8, anchor heads, wedges, shims and bearing plates).

Active corrosion is typically found only on the exposed parts of beari ng plates. Free water at end anchorage areas, when found in q uantities that are sufficient to allow collection and testing, has almost never been observed to cause corrosion.

Instances of deformation / damage / degradation are rare and almost always as sociated with singular construction events.

Most exceptions to the above are the result of unique situations that are plant specific and not indicative of an industry wide problem. Two widely reported exceptions, one involving wire corrosion and the ot her, anchor head material, are described below.

Occurrences have been limited to the plants where these were first observed.

• Debris blocked the drains at the perimeter of a shallow dome resulting in flooding that submerged the caps at the upper end of the vertical tendons. The hold down bolt holes in the tops of the caps were not well sealed. Storm water entered the caps through these holes and submerged the short lengths of uncoated wire just below the anchor heads. A number of wires were severely c orroded and found to be no longer effective as pre-stressing elements.

New maintenance procedures to prevent future flooding above the ring girder were implemented. The condition has not recurred.

8 The only U. S. containments with strand tendons, anchored with hardened wedges rather than cold formed button heads, are Rancho Seco, San Onofre (2 & 3) and Vogtle (1 & 2). Of these plants, only the Vogtle units are currently operating.

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• A unique combination of steel chemistry and high hardness led to the failure of anchor heads in both units of a two-unit plant. Several failures have occurred at these same units at random times over the past 4 decades. Industry wide evaluations established that anchor heads of this type are not in use elsewher e.

The problem has been addressed by implementing an enhanced examination program. Corrective action consists of replacing failed or cracked anchor heads as these are found.

3.4.3 Wire / Strand Test Results

Wire sample tests, performed by certified laboratories using appropriate equipment and procedures as specified in the applicable ASTM standards, show that strength and elongation at failure do not degrade with time. While past industry data often show reported strength and elongation to vary sign ificantly from examination to examination, close evaluation of the data suggests that such fluctuations can generally be attributed to variations in the testing, specifically:

• Many of the earlier tests were performed using vendor procedures that differ from those specified by the applicable ASTM standards.

• Testing equipment was often vendor-fabricated and did not meet ASTM specifications.

• Personnel assigned to the testing work did not always have the necessary experience.

In general, tests that conform to ASTM specifications and that are performed by experienced technicians show that both strength and elongation are close to, but exceed, the minima (240 ksi and 4.0 %, respectively) specified for ASTM A421 (Reference 6.6) wire.

As there is no evidence that either strength or elongation (at failure) decrease with time under load, it is concluded that there is no benefit to ongoing tests for these parameters.

And, it is to be noted that there is no precedent across the broader (beyond nuclear power plants) industry to periodically evaluate the continuing mechanical properties of pre-stressing system hardware and other steel structural members.

Relaxing the requirement for wire / strand tests, when justified by evaluation of specific plant operating experience, reduces the deleterious cycling of tendon force resulting from the de-tensioning and re-tensioning needed to allow wire removal. It also reduces the industrial hazard as sociated with the de-tensioning and re -tensioning operation.

3.4.4 Corrosion Protection Medium Test Results

Effectively all US containments that have ungrouted tendons use a corrosion protection medium (CPM) product supplied by the Viscosity Oil Company. CPM formulations have LAS RR Technical Report Page 17 of 77 Revision 0 / 20230214

changed over time but the basic product remains the same, i.e., a microcrystalline wax that provides the following protective functions.

• An essentially waterproof coating on tendon wires and end anchorage hardware.

• A bulk fill to limit water intrusion into tendon ductwork.

• A chemically built-in alkalinity to neutralize acid conditions that could lead to corrosion.

There is no industry operating experience to indicate that the CPM used in US containments has degraded over time in such a manner as to result in tendon or end anchorage hardware corrosion. Such hardware problems as have been found are attributable to either gross loss of medium from the ductwork, end anchorage design features that prevent full coverage of metallic components at the time of CPM injection or, metallurgical characteristics of certain anchor-head production batches.

Current CPM testing requirements mandate relatively complex procedures, as described or referenced in ASME Section XI ( Reference 6.2) Table IWL-2525-1, to determine absorbed water content, corrosive ion concentration and residual reserve alkalinity. As corrosive ions cannot enter the ductwork in the absence of water intrusion and reserve alkalinity cannot be brought into play in the absence of acid i on presence in the bulk CPM, there is little or no benefit gained by testing CPM samples for ion concentrations and reserve alkalinity unless there is evidence of free or absorbed water.

Consequently, industry experience would suggest that CPM samples collected during end anchorage examinations should be initially tested only to determine absorbed water content and that additional tests should be conducted only if there is evidence of sufficient water to establish potentially corrosive conditions or, if specific unit / plant test data indicate a history of problems with the CPM. Modifying testing programs accordingly would reduce the environmental problems associated with disposal of the reagents used in these processes (the procedure for determining water content does not require use of reagents).

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4. LAS EXAMINATION HISTORY AND RESULTS ANALYSIS / EVALUATION

The visual examination results and test data used in the development of Sections 4.1 through 4.4 are extracted from References 6.14 through 6.27 and 6.33.

LAS has completed, to date, 10 surveillances of the Unit 1 post-tensioning system and 9 surveillances of the Unit 2 post-tensioning system. These were performed in the years as shown in the following table. The SIT year s as shown on p. 109 of Reference 6.28 are also listed. The examinations were conducted in accordance with Regulatory Guide 1.35,

Revision 3, or 10CFR50.55a / ASME Section XI, Subsection IWL as noted.

SIT and Year Year Surveillance Performed Performed Governing Document(s)

Number / Unit 1 Unit 2 Year SIT 1978 1983 ASME III / Div. 2 / CC-6000 1 / 1 1980 1984 Reg Guide 1.35, Revision 2 2 / 3 1982 1986 Reg Guide 1.35, Revision 2 3 / 5 1983 1988 Reg Guide 1.35, Revision 2 4 / 10 1988 1993 Reg Guide 1.35, Revision 2 (Unit 1) /

Revision 3 (Unit 2) 5 / 15 1992 1997 Reg Guide 1.35, Revision 3 6 / 20 1997 2003 (Unit 1) Reg Guide 1.35, Revision 3 (Unit 2) 10CFR50.55a / IWL 7 / 25 2003 2008 10CFR50.55a / IWL 8 / 30 2008 2013-14 10CFR50.55a / IWL 9 / 35 2013-14 2019 10CFR50.55a / IWL 10 / 40 2019 N/A 10CFR50.55a / IWL

The following sections, 4.1 thr ough 4.4, of this report provide a comprehensive evaluation of LAS post-tensioning system examination results as documented in the applicable surveillance reports.

Section 4.1 addresses tendon force trends and forecasts Section 4.2 addresses end anchorage condi tion Section 4.3 addresses extracted wire condition and mechanical properties Section 4.4 addresses corrosion protection medium chemical properties and free water analysis

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The extension of the prestressing system examination interval as proposed in Part 2 above is justified if the extension can be separately justified for each of the 4 post-tensioning system performance categories addressed in Section 4.1 through 4.4.

In this report surveillances are generally referred to by calendar year and / or time, T, since the SIT date. Plots of time-dependent parameters use T for the time axis. Tables listing time dependent parameters show both the calendar year of the surveillance and the applicable value of T.

T is calculated as the difference between the surveillance mid-point date and the SIT mid-point date, each expressed as decimal years. M id-points are determined as decimal years midway between the event (SIT or surveillance) starting and ending dates as shown in the app licable referenced documents. To simplify computations, starting and ending dates are treated as the middle of the month during which the surveillance (or SIT) begins and ends. Values of T computed for Units 1 and 2 are shown in the tables below.

LAS Uni t 1 SIT & Surve i l l ance Date s and Ti me, T, Si nce SIT Ev e n t / S tart En d T', Mi d - P o i n t T, Surveillance Ye ar Mo n t h Ye ar Mo n t hYe ar & F racti o n Ye ars Si nce SIT Ye ar SIT 1978 12 1978 12 1978. 96 0. 0 1a 1980 7 1980 7 1980. 54 1. 6 3a 1982 5 1982 5 1982. 38 3. 4 5a 1983 11 1983 11 1983. 88 4. 9 10a 1988 7 1988 7 1988. 54 9. 6 15a 1992 12 1992 12 1992. 96 14. 0 20 1997 4 1997 5 1997. 33 18. 4 25 2003 4 2003 12 2003. 63 24. 7 30 2008 9 2008 12 2008. 83 29. 9 35 2013 9 2014 2 2013. 92 35. 0 40 2019 3 2019 5 2019. 29 40. 3

Note a: Surve i l l ance date s not note d i n re port; date s shown are f rom Re f e re nce 6.15

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LAS Uni t 2 SIT & Surve i l l ance Date s and Ti me, T, Si nce SIT Ev e n t / S tart En d T', Mi d - P o i n t T, Surveillance Ye ar Mo n t h Ye ar Mon t hYe ar & F racti o nYe ars Si nce SIT Ye ar SIT 1983 6 1983 6 1983.46 0. 0 1a 1984 5 1984 5 1984. 38 0. 9 3a 1986 12 1986 12 1986. 96 3. 5 5a 1988 10 1988 10 1988. 79 5. 3 10 1990 4 1990 5 1990.33 6. 9 15 1997 5 1997 6 1997. 42 14. 0 20 2003 4 2003 12 2003. 63 20. 2 25 2008 9 2008 12 2008. 83 25. 4 30 2013 9 2014 2 2013. 92 30. 5 35 2019 3 2019 5 2019. 29 35. 8 Note a: Surve i l l ance date s not note d i n re port; date s shown are f rom Re f e re nce 6.15

4.1 Tendon Force Trends and Forecasts

In the following discussions and evaluations, all computed mean forces and LCLs are rounded to a whole kip value. Computed values ending in (.5) are rounded to the nearest even number.

Units 1 and 2 tendon forces were measured during the surveillances noted in the table below.

Unit Surveillance Year - Tendon Force Measurement Yes / No 1 3 5 10 15 20 25 30 35 40

1 Yes Yes Yes Yes Yes No Yes No Yes No 2 Yes Yes Yes No Yes No Yes No Yes N/A

Force (lift-off force or the force required to separate the anchor head from the shim stack) in designated sample tendons, and additional tendons as mandated by procedure or specified by the Responsible Engineer, is measured during the examination. Measur ed force trends and forecasts provide ample evidence that mean pre-stressing in the containment suppression chamber and drywell walls will remain at or above the lower limits shown in report Section 1.1 above until at least T = 100 years (after the SIT) and, well beyond the currently expected 80- year maximum operating lifetime of the units (end of subsequent extended licensure, if granted, would be April 2062 or T = 83.3 years for Unit 1 and December 2063 or T = 80.5 years for Unit 2).

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The purpose of a lift -off force measurement is to determine how the initial seating force in a tendon ( seating force is used as a measure of the pre-stressing force contributed by the tendon) has been reduced by elastic shorteni ng and time dependent losses.

Reported tendon force is that measured at the bottom end of a vertical tendon and the average of the forces measured at the two anchorages of a hoop tendon. The mean of a number of tendon forces then serves as a reasonable estimate of the overall mean pre-stressing force provided by the applicable tendon group (i.e., hoop or vertical).

Forces measured at tendon anchorages reflect the losses due to elastic shortening 9, concrete creep, concrete shrinkage and tendon wire stres s relaxation.

Concrete creep strain, concrete shrinkage strain and wire stress relaxation are shown by relatively short-term tests 10 to vary more or less linearly with the logarithm of time. The log-linear characteristics established by these tests are used in containment design. For this reason, mean pre-stressing force trends are treated in this report as log-linear functions.

Plots of measured lift-off forces vs log-time may exhibit a significant degree of scatter. As the number of tendons included in surveillance samples is a small fraction of the total, the mean force represented by a trend line fitted to scattered data is only an estimate of the true mean pre-stressing force provided by the tendon group. A meaningful lower limit on the true mean at any point in time is computed as the 95% lower confidence limit 11 (LCL) on the trend line ordinate.

One hoop and one vertical tendon in each of the containments were designated as common tendons at the start of the surveillance program. These tendons are included in each consecutive surveillance sample. As common ten don lift-off forces tend to exhibit relatively little scatter, the computed common tendon trend line slope (representing loss of force in kips per unit logarithmic interval) can be treated as a close approximation of the group trend line slope.

In the following evaluations (Subsections 4.1.1 through 4.1. 4) of measured tendon lift -off forces, common tendon force trends are compared to those computed for the full set of measured lift-off forces. Close agreement (with one exception as noted in Subsection 4.1.2) between the trend line slopes supports a high degree of confidence that the true

9 Elastic shortening loss is the loss in tendon force resulting from the compressive strain induced in the concrete by subsequent tendon tensioning. It is generally greatest for the first tendon in a group to be tensioned and very small (there may be some effect due to subsequent tensioning tendons in the other groups) for the last tendon in the group to be tensioned.

10 Creep and shrinkage tests are typically conducted for 6 months and relaxation tests for 1,000 hours0 days <br />0 hours <br />0 weeks <br />0 months <br /> (just under 42 days). These time frames are short relative to the expected service life of a containment (40, 60 or, possibly, 80 years if a subsequent license extension is granted).

11 The use of a 95% confidence limit to bound a safety related parameter is established in 10CFR50, Appendix J (Reference 6.29) through citation of containment leakage rate testing standard ANSI/ANS 56.8 (Reference 6.30).

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trend of group mean force is well defined and that the projected trend can be used to forecast future mean values. Subsection 4.1.5 addresses measured lift -off forces in replaced tendon samples (replacement of vertical tendons is discussed in Subsection 4.2.6). Subsection 4.1.6 includes a t endon group force trend evaluation summary and the associated conclusions.

Lift-off forces, log-linear trend lines, LCLs (as applicable) and minimum required group mean forces (as applicable) are plotted on Figures 1 through 8 as described below.

• Figure 1 shows all measured Unit 1 hoop tendon lift -off forces listed in Table 2, the associated trend line, the associated LCL curve and the 575-kip minimum required mean hoop tendon force.

• Figure 2 shows Unit 1 common hoop tendon (H48AC) lift -off forces and the common tendon trend line.

• Figure 3 shows all measured Unit 1 vertical tendon lift -off forces listed in Table 3, the associated trend line, the associated LCL curve and the 600 -kip minimum required mean vertical tendon force.

• Figure 4 shows Unit 1 common vertical tendon (V15C) lift -off forces and the common tendon trend line.

• Figure 5 shows all measured Unit 2 hoop tendon lift -off forces listed in Table 4, the associated trend line, the associated LCL curve and the 575-kip minimum required mean hoop tendon force.

• Figure 6 shows Unit 2 common hoop tendon (H48EG) lift -off forces and the common tendon trend line.

• Figure 7 shows all measured Unit 2 vertical tendon lift -off forces listed in Table 5, the associated trend line, the associated LCL curve and the 600- kip minimum required mean vertical tendon force.

• Figure 8 shows Unit 1 common vertical t endon (V215C) lift -off forces and the common tendon trend line.

The log-linear trend slope and intercept as well as LCL values, as applicable, are computed using the methods developed in Probability and Statistics for Engineers by Irwin Miller and John E. Freund (Reference 6.31). Formulae are shown for reference in.

Trend lines and LCL curves are extrapolated to T = 100 years, a major grid line on the plot abscissa and, a time that is well beyond the 80- year presumed maximum operating life of the LAS units.

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4.1.1 Unit 1 Hoop Tendon Mean Force Trend, LCL, Margins and Common Tendon

Unit 1 hoop tendon lift -off forces measured during surveillances performed to date are listed in Table 2 and plotted on Figure 1, which also shows the mean force trend line, LCL curve and 575-kip minimum required value (MRV) line. Both the trend and LCL remain above the MRV at T = 100. In addition, all measured lift -off forces are above the MRV.

The trend line equation, as computed by Microsoft Excel usi ng the Attachment 1 formulae and shown on the figure, is:

F = 681.7 - 19.52

• Log10 (T) where F is mean force in kip and T is time since the SIT in years

Projected mean force, F(100), at T = 100 is:

F(100) = 681.7 - 19.52

• Log10 (100) = 681.7 - 19.52

• 2 = 643 kips

Projected LCL at T = 100, computed by Microsoft Excel using the Attachment 1 formulae, is:

LCL(100) = 630 kips

The margins above the 575-kip minimum at T = 100 years are:

Projected trend margin = 643 - 575 = 68 kips Projected LCL margin = 630 - 575 = 55 kips

Figure 2 shows the measured common tendon ( H48AC) lift-off forces and trend line. The lift-off data exhibit relatively little scatter. The slope of the trend line is -17.69 kips per unit logarithmic interval which is close to the slope ( -19.49) computed using all Unit 1 hoop tendon data and shown o n Figure 1.

This close agreement between the trend line slopes supports a conclusion that the trend computed for all measured lift -off forces is closely representative of the true mean force trend.

Taken together, the Figure 1 and Figure 2 plots provide solid evidence that Unit 1 hoop tendon mean force will remain above the 575 -kip minimum required value (MRV) throughout the presumed 80- year maximum operating lifetime of the unit.

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4.1.2 Unit 1 Vertical Tendon Mean Force Trend, LCL, Margins and Common Tendon

Unit 1 vertical tendon lift -off forces measured during surveillances performed to date are listed in Table 3 and plotted on Figure 3, which also shows the mean force trend line, LCL curve and 600 -kip MRV line. Both the trend and LCL remain above the MRV at T = 100.

In addition, all measured lift -off forces are above the MRV.

The trend line equation, as computed by Microsoft Excel using the Attachment 1 formulae and shown on the figure, is:

F = 693.6 - 35.38

• Log 10 (T)

Projected mean force, F(100), at T = 100 is:

F(100) = 693.6 - 35.38

• Log10 (100) = 693.6 - 35.38

• 2 = 623 kips

Projected LCL at T = 100, computed by Microsoft Excel using the Attachment 1 formulae, is:

LCL(100) = 616 kips

The margins above the 600- kip minimum at T = 100 years are:

Projected trend margin = 623 - 600 = 23 kips Projected LCL margin = 616 - 600 = 16 kips

Figure 4 shows the measured common tendon (V15C) lift -off forces and trend line. The lift-off data exhibit relatively little scatter. The slope of the trend line is - 40.74 kips per unit logarithmic interval which is reasonably close to the slope ( -35.38) computed using all Unit 1 vertical tendon data and shown on Figure 3.

The reasonably close alignment of the trend line slopes supports a conclusion that the trend computed for all measured lift -off forces is closely representative of the true mean force trend.

Taken together, the Figures 3 and 4 plots provide solid evidence that Unit 1 vertical tendon mean force will remain above the 600- kip MRV throughout the presumed 80- year maximum operating lifetime of the unit.

4.1.3 Unit 2 Hoop Tendon Mean For ce Trend, LCL, Margins and Common Tendon

Unit 2 hoop tendon lift-off forces measured during surveillances performed to date are listed in Table 4 and plotted on Figure 5, which also shows the mean force trend line, LCL curve and 575-kip MRV line. Both the trend and LCL remain above the MRV at T = 100.

In addition, all measured lift -off forces are above the MRV.

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The trend line equation, as computed by Microsoft Excel using the Attachment 1 formulae and shown on the figure, is:

F = 652.5 - 8.49

• Log10 (T)

Projected mean force, F(100), at T = 100 is:

F(100) = 652.5 - 8.49

• Log10 (100) = 652.5 - 8.49

• 2 = 636 kips

Projected LCL at T = 100, computed by Microsoft Excel using the Attachment 1 formulae, is:

LCL(100) = 625 kips

The margins above the 575-kip minimum at T = 100 years are:

Projected trend margin = 636 - 575 = 61 kips Projected LCL margin = 625 - 575 = 50 kips

The above margins are close to those computed for the Unit 1 hoop tendon group.

Figure 6 shows the measured common tendon (H48 EG) lift-off forces and trend line. As is the case for both Unit 1 common tendons, t he lift-off data exhibit relatively little scatter.

The slope of the trend line is - 18.65 kips per unit logarithmic interval which is over twice that (-8.49) computed using all Unit 2 hoop tendon data and shown in Figure 5.

The hoop group trend line slopes computed using all Unit 1 surveillance lift -off data, Unit 1 common tendon data and Unit 2 common tendon data are all close to - 20 kips per unit logarithmic interval. Conservatively postulating that the slope of the Unit 2 hoop group true mean tendon force is, in fact, close to - 20 kips per unit logarithmic interval gives the following alternative and approximate (no adjustment for any difference in intercept) value for F(100).

F(100) (conservative approximation) = 652.5 - 20

• Log10 (100) = 612 kips

And, postulating that the difference between F(100) and LCL(100) remains unchanged at 636 - 625 = 11 kips, the alternative LCL at T = 100 years is:

Alternative LCL(100) = 612 - 11 = 601 kips.

The corresponding alternative margins above the 575-kip MRV are:

Alternative projected trend margin = 612 - 575 = 37 kips Alternative projected LCL margin = 601 - 575 = 26 kips

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Taken together, the Figures 6 and 7 plots, as well as the conservative alternative calculations using a hoop tendon mean force trend slope of - 20 kips per unit logarithmic interval, provide solid evidence that Unit 2 hoop tendon mean force will remain above the 575-kip MRV throughout the presumed 80- year maximum operating lifetime of the unit.

4.1.4 Unit 2 Vertical Tendon Mean Force Trend, LCL, Margins and Common Tendon

Unit 2 vertical tendon lift -off forces measured during surveillances performed to date are listed in Table 5 and plotted on Figure 7, which also shows the mean force trend line, LCL curve and 600 -kip MRV line. Both the trend and LCL remain above the MRV at T = 100.

In addition, all measured lift -off forces are above the MRV.

The trend line equation, as computed by Microsoft Excel using the Attachment 1 formulae and shown on the figure, is:

F = 660.0 - 19.82

• Log10 (T)

Projected mean force, F(100), at T = 100 is:

F(100) = 660.0 - 19.82

• Log10 (100) = 660.0 - 19.82

• 2 = 620 kips

Projected LCL at T = 100, computed by Microsoft Excel using the Attachment 1 formulae, is:

LCL(100) = 613 kips

The margins above the 600- kip minimum at T = 100 years are:

Projected trend margin = 6 20 - 600 = 20 kips Projected LCL margin = 613 - 600 = 13 kips

The above margins are close to those, 23 and 16 kips, respectively, computed for the Unit 1 vertical tendon group.

Figure 8 shows the measured common tendon ( V215C) lift-off forces and trend line. As in the previous three cases, the data exhibit relatively little scatter. The slope of the trend line is - 23.55 kips per unit logarithmic interval which is close to the slope ( -19.82) computed using all Unit 2 vertical tendon data and shown in Figure 7.

This close agreement between the trend line slopes supports a conclusion that the trend computed for all measured lift -off forces is closely representative of the true mean forc e trend.

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Taken together, the Figures 7 and 8 plots provide solid evidence that Unit 2 vertical tendon mean force will remain above the 600- kip MRV throughout the presumed 80- year maximum operating lifetime of the unit.

4.1.5 Replaced Vertical Tendon Pre-Stressing Force Evaluation

The following Unit 1 and Unit 2 vertical tendons were replaced in 2003-2004 as discussed in Section 4.2.6 below.

Unit 1: V2A, V3A, V4A, V8A, V10A, V12A, V13A, V14A, V26A, V29A Unit 2: V228A, V229A

Designated samples from th e two populations were examined during two special purpose surveillances, performed in 2006 and 2007, respectively, as well as during the Unit 2 25 th year surveillance in 2008, the Unit 1 35 th year surveillance in 2014 and the Unit 2 35th year surveillance in 2019. Lift -off forces measured during these surveillances are tabulated below.

Replaced Vertical Tendon Lift-Off forces Surveillance Year / Yearsa Tendon ID Measured Lift-off, since Tensioning kip V2A 729 V4A 738 2006 / 2.5 V8A 717 V12A 751 V29A 749 V10A 731 V14A 730 2007 / 3.5 V26A 728 V228A 725 V229A 730 2008 / 4.5 V228A 720 2014 / 10.5 V3A 704 2019 / 15.5 V229A 739 Note a: Years since tensioning approximated by assigning the tensioning date as the end of 2003 / beginning of 2004 and the surveillance date as the mid-point of the year noted.

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The measured lift-off forces listed above are all over 700 kip. The Unit 1 and Unit 2 vertical tendon lift -off forces measured durin g the 1, 3, 5, 10 and 15 -year surveillances (with elapsed times since tensioning corresponding roughly to those listed above), and shown in Tables 3 and 5, are all under 700 kip.

For given elapsed time since tensioning, the loss of force due to wire str ess relaxation should be about the same for both the originally installed and the replaced tendons.

However, loss due to concrete creep and shrinkage is much less for the replaced tendons,

which are not affected by the creep and shrinkage strains accrued over the 3-decade interval between initial tensioning in the 1970s and the 2003-2004 tensioning of the replaced tendons.

Therefore, the replaced tendon subgroup mean force is expected to always remain above the mean force in the originally installed vertical tendons and, consequently, well above the 600- kip minimum required value throughout the operating life of the units.

4.1.6 Pre-Stressing Force Trend Evaluation Summary and Conclusion s

Tendon group force trend and LCL margins developed in Subsections 4.1.1 through 4.1.4 are consolidated in the following table.

Group / Value, kip, & Margin, kip, Over MRV MRV Unit At T = 100 Years Trend Margin LCL Margin Hoop / 1 643 68 630 55 575 kips 2a 612 37 601 26 Vertical / 1 623 23 616 16 600 kips 2 620 20 613 13 Note a: Alternative values computed using a trend line slope of - 20 kips per unit logarithmic interval (conservative).

The above table, which uses conservative alternative trend and LCL values for the Unit 2 hoop group, as discussed in Subsection 4.1.3, shows hoop and vertical tendon mean force trends and LCLs remaining above the respective MRVs though T = 100 years,

which is beyond the postulated 80- year maximum operating lifetime of the uni ts.

The slopes of the trend lines computed for the Unit 1 tendon groups and the Unit 2 vertical group are in good agreement with the associated common tendon trend line slopes. As discussed above, this supports a conclusion that the computed group tren ds are close to the true trends.

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As noted in Subsection 4.1.3, the slope computed for the Unit 2 hoop tendon group trend line is less than half that of the common tendon trend line, a result that may be a consequence of data scatter. Adjusting the slope of the group trend line to a round number value somewhat greater than the slope of the common tendon trend line gives conservative, but still positive, trend and LCL margins. This supports a conclusion that the true group trend and LCL projected to T = 100 years also provide positive margins.

On the basis of the evaluations presented above, it is concluded that the interval bet ween tendon lift-off force measurements may be extended as proposed in Part 2 of this technical report with no adverse impac t on safe operation of the plant.

4.2 End Anchorage Condition

During each of the surveillances, e nd anchorage areas were visually examined for evidence of corrosion, presence of free water, broken wires or missing button heads,

damage to / distortion of load bearing components and crack s in concrete adjacent to bearing plates. Results of these examinations, as documented in References 12 6.21 through 6.27 are summarized in Subsections 4.2.1 through 4. 2.5. Replacement of corroded vertical tendons in 2003 and 2004 is addressed in Subsection 4.2.6.

Evaluations and conclusions based on end anchorage condition are presented in Subsection 4.2.7.

4.2.1 Corrosion

Severity of corrosion, as documented in surveillance reports, is documented by the numeric and alphabetic levels defined below.

2003, 2006 & 2007 Surveillances Level Definition (Levels 1 or A and 2 or B Acceptable) 1, A Bright metal with no visible oxidation 2, B Reddish-brown metal with no pitting 3 Patches of red oxide with pitting 0.000 to 0.005 4 Patches of red oxide with pitting 0.005 to 0.010 5 Heavy rusting with noticeable pitting >0.010

12 With the exception of the document (Reference 6.33) covering the 1997 Unit 2 15th year surveillance, records of visual examinations performed prior to 2003 were not located. This does not impact the conclusions developed in this report since tendon end anchorage conditions are either as these existed at the time of construction or age related. Therefore, observations documented in 2003 and during later surveillances providethe essential information needed to assess age related degradation, if any, at tendon end anchorages.

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2008 Surveillance Level Definition (Levels 1 and 2 Acceptable) 1 Bright metal with no visible oxidation 2 Reddish-brown metal with no pitting 3 Pitting 0.000 to 0.003 4 Pitting 0.003 to 0.006 5 Pitting >0.006

2014 Surveillance Level Definition (Levels 1 and 2 Acceptable) 1 Bright metal with no visible oxidation 2 Reddish-brown metal with no pitting 3 Pitting 0.000 to 0.003

2019 Surveillance Level Definition (Levels 1 and 2 Acceptable) 1 Bright metal with no visible oxidation 2 Visible Oxidation with no pitting 3 Pitting 0.000 to 0.003 A Bright, uniform in color B Partial loss of color C Major loss of color

Corrosion documented during surveillances conducted from 2003 (Unit 1 25th year and Unit 2 20th year) through 2019 (Unit 1 40th year / Unit 2 35th year is identified in the following table.

End Anchorage Corrosion Calendar Surveillance Year Year Unit 1 Unit 2 Unit 1 Unit 2 Small area of active Level 4 corrosion found on the V215A 2003 25th 20th No corrosion greater than Level 2 (B) found. field (bottom) end. No additional corrosion greater than Level 2 (B) found.

2006 N/A N/A No corrosion greater than No corrosion greater than Level 2 (B) found. Level 2 (B) found.

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End Anchorage Corrosion Calendar Surveillance Year Year Unit 1 Unit 2 Unit 1 Unit 2 2007 N/A N/A No corrosion greater than No corrosion greater than Level 2 (B) found. Level 2 (B) found.

2008 30th 25th No corrosion greater than No corrosion greater than Level 2 found. Level 2 found.

2014 35th 30th No corrosion greater than No corrosion greater than Level 2 found. Level 2 found.

2019 40th 35th No corrosion greater than No corrosion greater than Level 2 (B) found. Level 2 (B) found.

On the basis of the above descriptions, it is concluded that corrosion observed on pre-stressing system end anchorage hardware is not progressing and is not adversely impacting containment structural integrity. Therefore, it is concluded that corrosion does not constitute a constraint to extending the pre-stressing system examination interval as discussed in Part 2 of this report.

4.2.2 Free Water

Free water found at tendon end anchorages is documented in the following table. Shop and field end anchorages are designated by an (S) or (F) following the tendon ID number.

Surveillance reports identify quantities found in units of ounces (oz). Where applicable, the quantities shown in the table are rounded to the nearest whole ounce. Surveillance reports do not indicate that free water samples, other than that collected at the V28A field (bottom) end anchorage, were tested to determine pH.

Free Water Found at Anchorages Calendar Surveillance Year Year Unit 1 Unit 2 Unit 1 Unit 2 V12A(S)-1 oz, V13A(S)-2 oz, 2003 25th 20th V26A(F)-1 oz, V28A(F)-12 oz, H39GF(S)-2 oz, H72FE(F)-1 oz V58C(F)-2 oz 2006 N/A N/A No water detected. No water detected.

2007 N/A N/A No water detected. No water detected.

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Free Water Found at Anchorages Calendar Surveillance Year Year Unit 1 Unit 2 Unit 1 Unit 2 2008 30th 25th No water detected. No water detected.

2014 35th 30th V3A(F)-5 oz, V15A(F)-1 oz, V203B(F)-1 oz V7A(F)-1 oz 2019 40th 35th No water detected. V218B(F)-4 oz, V203B(F)-3 oz

Entries in the above table show that the amount of free water found at anchorages is neither excessive nor increasing over time. In addition, neither new nor ongoing corrosion greater than Level 2 (B) was observed at anchorages where free water was found. And, as the LAS containments are effectively isolated from ground wat er intrusion, it is reasonable to postulate that most, if not all, water found at the anchorage areas was present at the time of initial CPM installation.

The sample collected at the V28A field end anchorage was tested to determine pH. T he test result showed a pH of 9.02 which is alkaline and, therefore, considered acceptable.

Therefore, it is concluded that amounts and trend of water found at tendon anchorage areas, as well as water pH, do not constitute a constraint to extending the pre-stressing system examination interval as discussed in Part 2 of this report.

4.2.3 Broken / Protruding Wires and Missing Button Heads

Broken wires and a count of missing button heads (BH) not previously documented are noted in the follow ing table. Shop and field end anchorages are designated by an (S) or (F) following the tendon ID number.

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Protruding Button Heads, Missing Button Heads and Broken Wires not Previously Documented Calendar Surveillance Year Year Unit 1 Unit 2 Unit 1 Unit 2 V12A(S) - 7 protrudinga V2A(S) - 10 protrudinga V3A(S) - 17 protruding &

53 missing / brokena V219A(F) - 1 missing / broken 2003 25th 20th V10A(S) - 4 broken V228A(S) - 3 protrudinga V13A(S) - 17 protruding & V229A(S) - 9 protrudinga 59 missing / brokena V247C(F) - 1 missing / broken V14A(S) - (?) brokena,b V29A(S) - 28 protruding &

31 missing / brokena

No new protruding button No new protruding button 2006 N/A N/A heads, missing button heads heads, missing button heads or or broken wires noted. broken wires noted.

No new protruding button No new protruding button 2007 N/A N/A heads, missing button heads heads, missing button heads or or broken wires noted. broken wires noted.

No new protruding button No new protruding button 2008 30th 25th heads, missing button heads heads, missing button heads or or broken wires noted. broken wires noted.

V212C(F) - 1 protruding, NCR-No new protruding button N1090- 001 2014 35th 30th heads, missing button heads V204C(F) - 1 missing, NCR-or broken wires noted. N1090- 002 V204C(S) - 1 missing, NCR-N1090-003 No new protruding button No new protruding button 2019 40th 35th heads, missing button heads heads, missing button heads or or broken wires noted. broken wires noted.

Note a: Tendon replaced; see discussion in Subsection 4.2.6.

Note b: Per the 2003 surveillance report, an unspecified number of wires were found to be broken during re-tensioning; tendon replaced in 2004.

Only 3 wires were found with protruding or missing button heads dur ing the examinations subsequent to 2003 (see discussion of corroded and broken vertical tendon wires and replacement of vertical tendons in Subsection 4.2.6 below). This represents a minisc ule fraction of the total number of button heads examined. And, there is no indication that the rate of wire damage is increasing over time.

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Therefore, it is concluded that extending the pre-stressing system examination interval as discussed in Part 2 of this report will not result in a failure to find tendon damage that impairs containment structural integrity.

4.2.4 Anchor Head, Bushing, Shim and Bearing Plate D istortion / Damage

No anchor heads, bushings 13, shims or bearing plates were found to be distorted or damaged.

4.2.5 Concrete Cracking Adjacent to Bearing Plates

Concrete extending out 24 inches from the edges of tendon bearing plates was visually examined for cracking. No c racks exceeding 0.01 inches in width were recorded.

4.2.6 Broken Wires Found During the 2003 Surveillance

During the 2003 surveillance (Unit 1 25 th year and Unit 2 20 th year) a number of subgroup A vertical tendons were found to have broken wires as shown in the table in Subsection 4.2.3 above. The broken wires were severely corroded near the upper ends. A root cause evaluation, documented in Root Cause Report Number A/R 00157920 (Reference 6.32), concluded that the corrosion was due to a combination of wat er intrusion and insufficient CPM coverage on the wires.

Water is postulated to have entered the upper ends of the tendons through faulty floor cover gaskets. Insufficient CPM coverage was considered to be due to one of two possible causes; insufficient initial fill or loss of CPM through faulty gaskets at the bottom end caps.

Corrective action, summarized in the 2003 surveillance report, included replacement of designated tendons, replacement of CPM in accessible subgroup A tendons, replacement of access well floor cover gaskets and replacement of lower end cap gaskets 14 observed to be leaking.

The following tendons were replaced in 2003 and 2004 as noted below.

2003 Replacement: V3A, V12A, V13A & V29A 2004 Replacement: V2A, V4A, V8A, V10A, V14A, V26A, V228A & V229A

13 Bushings are separate load bearing components threaded onto shop anchor heads.

14 Due to inaccessibility of, and inability to vent at, the upper ends of subgroup B tendons, CPM leaks observed at the bottom ends of V4B and V20B were eliminated by tightening the end cap hold down bolts. Additional CPM was not injected.

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With the minor exceptions noted in the Subsection 4.2.3 table, no additional protruding button heads, missing button heads or broken wires were found during the surveillances performed in 2006, 2007, 2008, 2014 and 2019.

4.2.7 End Anchorage Condition Evaluation and Conclusions

Tendon end anchorage hardware and adjacent concrete have performed well throughout the life of the plant (through the most recent surveillance i n 2019) and show no trends of deteriorating condition.

With one minor exception (the small area of active Level 4 corrosion found on the V215A bottom bearing plate during the 2003 surveillance), there have been no findings of corrosion greater than Level 2 (or B) on bearing plates, anchor h eads, shims or button heads.

Only minor amounts of free water have been found in anchorage areas and no corrosion has been associated with such water as has been found.

The vertical tendon broken wires documented in the 2003 surveillance report were addressed in a root cause evaluation and concluded to have been the result corrosion due to water intrusion at the upper end access well floor plates in conjunction with insufficient CPM coverage. The root cause was eliminated by replacement of floor plate gaskets (with ongoing periodic replacement as deemed necessary), replacing lower anchorage end cap gaskets (or tightening subgroup B tendon end cap hold down bolts) where CPM leaks are observed and refilling vertical tendons with CPM.

Since completion of the tendon replacement activity in 200 4, only 3 new unseated or missing button heads have been documented at the 210 end anchorage areas examined during the period. These three represent only a miniscule fraction of the 210

• 90 = 18,900 button head locations at the examined end anchorages.

No damage, cracking or distortion has been found during visual examinations of bearing plates, anchor heads, wedges and shims.

No concrete cracks 0.010 inches or greater in width have been found at tendon anchorage areas.

End anchorage visual examination trends, as discussed above, show that the condition of both post-tensioning system hardware and concrete adjacent to tendon end anchorage bearing plates is stable and unlikely to experience significant cha nge over the operating lifetime of the plant.

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Therefore, it is concluded that the results of tendon end anchorage examinations performed to date support the extension of system examination intervals as presented in Part 2 of this technical report.

4.3 Wire Examination and Test Results Evaluation

Test wires (one from one tendon in each group) were extracted from surveillance tendons and tested to verify continuing strength and ductility. Test results, which are typical of those reported for tests on wires extracted from tendons at other nuclear plants, are shown in Tables 6a, 6b, 7a and 7b.

4.3.1 Test Results Summary

Test results are summarized below.

Test Wire Sample Ultimate Strength (ksi) Summary Exam Unit 1 Unit 2 Year Min Mean Max Min Mean Max 1st 245 254 260 240 248 253 3rd 246 252 257 242 248 255 5th 247 252 257 237 244 248 10th 240 246 256 N/A N/A N/A 15th 243 249 256 248 254 261 25th 256 265 274 256 261 263 35th 244 248 252 244 248 251 Overall Mean 252 250

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Test Wire Sample Elongation at Failure (%) Summary Exam Unit 1 Unit 2 Year Min Mean Max Min Mean Max 1st 4.5 5.4 6.3 4.5 4.8 5.0 3rd >4 >4 >4 >4 >4 >4 5th >4 >4 >4 4.0 4.7 5.5 10th 4.0 4.9 5.7 N/A N/A N/A 15th 3.4 4.2 5.1 4.2 4.7 5.0 25th 4.3 5.4 6.3 4.0 4.2 4.4 35th 3.9 4.3 4.8 4.0 4.4 5.0 Overall Mean 4.8 4.5

Test wires were, where corrosion levels are noted in the applicable referenced documents, all found to be Level 1 (or A).

4.3.2 Results Evaluation

Strength and ductility are evaluated against the applicable ASTM A421 acceptance criteria, 240 ksi minimum tensile strength and 4% minimum elongation at failure.

The results shown in the tables and summarized above exhibit significant variations from surveillance to surveillancebut no apparent trend for wire strength and ductility to change over time.

The mechanical properties of wire are expected to vary over a small range from heat to heat, which can account for some of the variations in minimum, mean and maximum tensile strength and elongation at failure listed above.However, the ranges of both tensile strength (237 to 274 ksi) and elongation at failure (3.4 to 6.3%) seem excessive for wire manufactured to meet a single ASTM standard (ASTM A421). The certified material test report (CMTR) data documented in Reference 6.16 show tensile strengths between 240.4 to 256.6 ksi (rounded to 240 and 257 ksi in subsequent discussions) and elongations at failure between 4.5 and 5.7% (however, with many noted only as >4.0%).

As the sample wire tests were performed at different times and, often, by different technicians working with a variety of equipment at different laboratories, it can be concluded that much, if not all, of the presumed excessive variation is attributable to differences in testing techniques and equipment. This conclusion is supported by the spreads in the results shown for tests performed in any given year (presumed to be performed by the same laboratory and technicians) as noted below.

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Calendar Surveillance Yeara Spread Year Unit 1 Unit 2 Strength, ksi Elongation, %

1980 1st N/A 15 1.8 1982 3rd N/A 11 No data 1983 5th N/A 10 No data 1984 N/A 1st 13 0.5 1986 N/A 3rd 11 No data 1988 10th 5th 19 1.7 1992 15th 10th Visual 13 1.7 1997 20th Visual 15th 13 0.8 2003 25th 20th Visual 18 2.0 2008 30th Visual 25th 7 0.4 2013-14 35th 30th Visual 8 0.9 2019 40th Visual 35th 7 1.0 Note a: N/A - no surveillance performed; Visual - no wire extraction / test.

Maximum spreads shown for tests performed in a given year are 19 ksi and 2.0%. These are closer to the Reference 6.16 CMTR test spreads (17 ksi and 1.2%) than to the spreads (37 ksi and 2.9%) computed using all test data.

Five of the entries in Table 6b and one entry in Table 7a are highlighted to indicate test results that do not meet acceptance criteria. The low Unit 2 tensile strength, 237 ksi, measured in 1992 (the 5 th year Unit 2 surveillance) is addressed in Reference 6.15. The low Unit 1 elongat ion, 3.9% measured in 2013-14 (the 35th year Unit 1 surveillance), is covered in NCR-FN1090- 004 as cited in the surveillance report, Reference 6.26.

The low Unit 1 elongations (3.4 to 3.8%) measured in 1992 (the Unit 1 15 th year surveillance) were not addressed in the associated reference (6.17). As these tests involved wires extracted from two different tendons, it is not unreasonable to conclude that testing equipment / procedures, and not limited wire ductility, are responsible for the low values reported. Evaluation of results from tests on wires from tendons at other nuclear power plants has, in many cases, led to similar conclusions.

Other than those reported results presumed erroneous and one that might represent a singular condition, wire tests showed that acceptable levels of tensile strength and ductility are ongoing. The surveillance year mean values of strength and elongation shown above (and in Tables 6a / 6b and 7 a / 7b) do not show that these values are trending up or down. This is typical of tests performed over the years on specimens from the tendons in containments at other nuclear plants.

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4.3.3 Conclusion and Recommendation

On the basis of the above evaluations, it is concluded that wire strength and ductility are not degrading with time. Therefore, it is recommended that requirements for routine testing of tendon wire, and the associated de-tensioning of tendons to allow extraction of test wires, be deleted from the post-tensioning system surveillance program. But, if routine wire testing is deleted from the program, the Responsible Engineer may still specify such tests when conditions (e.g., broken wires, active corrosion or low pH water) found at an anchorage indicate the possibility of wire degradation.

4.4 Corrosion Protection Medium Testing

Corrosion protection medium (CPM) was collected at the ends of sample tendons during each surveillance. Each CPM sample was tested for the presence of three corrosive ions (chlorides, nitrates and sul fides), absorbed water content and, since 1997 (Unit 1 20 th year surveillance), reserve alkalinity (expressed as neutralization number or base number).

4.4.1 Test Procedures and Early (1997 and Earlier) Test Results Evaluation

Tests were performed as specified in ASME Section XI, Subsection IWL, Table IWL-2525-1 15.

Absorbed water content and base number are determined for bulk samples of CPM. The laboratory procedure used to determine water content is standardized and easily performed. It should yield reasonably accurate results. That used to determine base number is fairly complex; results tend to exhibit more variability than would be expected for the material being analyzed.

Corrosive ion concentrations are not determined for bulk samples of CPM but, rather, for water maintained in contact with a defined CPM surface area under specified conditions.

More recently conducted tests tend to yield the expected results; i.e., that corrosive ions are essentially absent from the CPM samples. T ests (52 samples) performed in 1997, and documented in Reference 6.20, yielded erratic results for nitrate ion concentrations with a maximum of 5.97 ppm. C hloride and sulfide ion concentrations reported for the same samples are all below the 0.50 ppm limit of detection for the analytical technique employed. T he 1980 test results (56 samples), documented in Reference 6.14, show chloride concentrations in 52 samples that are over 1 ppm (with a maximum of 2.4 ppm).

But, all 56 samples tested in 1980 yielded nitrate ion concentrations (as well as sulfide ion concentrations) below the 1 ppm limit of detection.

15 Early CPM tests are assumed to have been performed per procedures developed by the supplier, Viscosity Oil Co. These procedures were subsequently incorporated into Subsection IWL.

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The pattern of variability exhibited by the early (1997 and earlier) CPM tests suggests that results may reflect errors resulting from incorrect application of the procedures developed for the Viscosity Oil product. For this reason, evaluation of CPM test results is limited to those documented in the 2003 ( Unit 1 25th year and Unit 2 20 th year surveillances) and later surveillance reports.

4.4.2 Acceptance Criteria and Test Results (2003 and Later Tests)

All CPM test results documented in the 2003 through 2019 reports met the following ASME Section XI, Subsection IWL (and LAS) acceptance criteria.

Corrosion Protection Medium Test Acceptance Criteriaa Parameter Chloride Ion Sulfide Ion Nitrate Ion Water Base Concentration Concentration Concentration Content Number Acceptance 10 ppm 10 ppm 10 ppm 10% by 17.5b Criterion Wg Note a: Ion concentration limit is for a water extract prepared per Subsection IWL, Table IWL-2525-1.

Note b: 17.5 is 50% of the minimum base number specified for new Visconorust 2090P -4 material.

4.4.2.1 Corrosive Ions

Corrosive ion test results are summarized below.

CPM Sample Corrosive Ion Concentrations (Lower Limit of Resolution for All Ions Is 0.50 ppm except as Noted)

Number Chloride Ion Nitrate Ion Sulfide Ion Calendar of Concentration, ppm Concentration, ppm Concentration, Year Samples ppm Tested Min Max Min Max Min Max 2003 45 <0.50 1.0a <0.50 <0.50 <0.50 <0.50 2006b 11 <0.50 0.50 <0.50 <0.50 <0.50 <0.50 2007b 10 <0.50 0.50 <0.50 <0.50 <0.50 <0.50 2008 49 <0.50 1.0c <0.50 <0.50 <0.50 <0.50 2013-14 70 <0.50 <0.50 <0.50 <0.50 <0.50 <0.50 2019 34 <0.50 <0.50 <1.0d,e <1.0d <0.50e <0.50e Note a: One sample result at 1 ppm; all others 0.50 ppm.

Note b: New 2090P-4 material injected into ductwork of tendons replaced in 2003-2004.

Note c: Four sample results at 1 ppm; all others 0.50 ppm.

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Note d: The lower limit of resolution for nitrate ions was increased to 1.0 ppm for the 2019 test series.

Note e: Sulfide ion concentrations for the two samples from tendon 48AC are listed in the 2019 report Table 3-1 as <1.0 ppm; all others are <0.50 ppm. Nitrate ion concentrations for these samples are listed as <0.5 ppm; all others are <1.0 ppm. The report table entries are apparently reversed; presumed correct values are shown above.

With the exception of the 1.0 ppm concentration shown for 5 chloride ions, all concentrations listed in the 2003 through 2019 surveillance reports are at or below the lower limit of resolution (1.0 ppm for nitrate ion tests performed in 2019; otherwise, 0.50 ppm) and significantly les s than the 10-ppm upper acceptance limit applicable to all three ions.

As there is no indication that corrosive ion concentration is increasing over time, it is concluded that there is no need to continue routine tests for these ions. In the future, such tests should only be performed at the direction of the Responsible Engineer (RE).

4.4.2.2 Water Content

Water content test results are summarized below.

CPM Sample Water Content

Water Content, %

Calendar Year Number of Samples Tested (Lower Limit of Resolution Is 0.1%)

Min Max 2003 45 <0.10 7.20f 2006b 11 <0.10 0.67 2007b 10 <0.10 0.19 2008 49 <0.10 1.60g 2013-14 70 <0.10 2.9h 2019 33 <0.10 0.93 Note b: New 2090P-4 material injected into ductwork of tendons replaced in 2003-2004.

Note f: One sample at 7.20%, one at 3.10% and 6 from 1.00% to 2.50%; others

<1.00%.

Note g: One sample at 1.6%; all others <1.00%.

Note h: One sample at 2.9 %; all others <1.00%.

All sample water contents are below the 10% by weight upper limit and all but 1 (at 7.20%)

are less than one third of the limit.

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4.4.2.3 Reserve Alkalinity

Reserve alkalinity (as measured by base number) test results are summarized below.

CPM Sample Base Number Calendar Year Number of Base Number Samples Tested Min Max 2003 45 31.0 63.6 2006b 11 35.9 49.6 2007b 10 6.05i 10.4i 2008 49 18.0 73.3 2013-14 70 10.1j 73.6 2019 33 31.8 78.6 Note b: New 2090P -4 material injected into ductwork of tendons replaced in 2003-2004.

Note i: Results considered to be erroneous.

Note j: Three sample base numbers, 17.2, 16.3 and 10.1 are below the 17.5 lower acceptance limit.

Base number variations, other than those shown for the 2006 samples, do not see m reasonable for the Visconorust 2090P -4 CPM used at LAS. The excessively high (above 50 or 60) and low (below 20) max imum and minimum sample base numbers listed above are concluded to be the result of variations in the techniques / procedures used to prepare and test the CPM specimens and not representative of true specimen reserve alkalinity.

And, there is nothing in the data reproduced above that would indicate an age-related degradation of CPM reserve alkalinity. Both the maximum and minimum report ed base numbers have varied in a somewhat erratic manner and show no consistent trend. And, as documented in the 2019 surveillance report, base numbers are currently well above the 17.5 lower acceptance limit.

4.4.2.4 CPM Test Conclusion / Recommendation

On the basis of the above evaluations, as well as the results of examinations for corrosion, it is concluded that the CPM is retaining its corrosion protection potential over time and no longer requires testing to determine corrosive ion concentration or base number unless such tests are specified by the Responsible Engineer.

Therefore, it is recommended that the post -tensioning system C ontainment ISI program retain only the requirement for determining CPM water content but delete that for routine testing to determine corrosive ion concentration and base number. However, the LAS RR Technical Report Page 43 of 77 Revision 0 / 20230214

Responsible Engine er may specify additional tests if deemed necessary. It is expected that such additional tests would, at a minimum, be performed to assess the cause of observed corrosion or the effect of free or absorbed water on CPM properties.

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5. OVERALL

SUMMARY

, CONCLUSIONS AND RECOMMENDATIONS

A summary of surveillance results, conclusions based thereon and recommendations for future changes to the surveillance program are outlined Sections 5.1, 5.2 and 5.3 below.

5.1 Surveillance Results Overall Summary

The results of the post -tensioning system surveillances conducted at LAS between 1980 and 2019 show that the Unit 1 and Unit 2 system s are continuing to perform the intended functions and can be expected to do so until well beyond the maximum expected 80- year operating lifetime of the units. P erformance of the system s, determined by evaluations of the visual examination findings / test results as detailed in Part 4 of this technical report,

is summarized below.

5.1.1 Tendon Force

The mean force in each of the originally installed Unit 1 and Unit 2 tendon groups is projected by log-linear regression to remain above the specified minimum required values through T = 100 years (after the unit SIT) until well beyond the maximum expected 80-year operating lifetime of the units. In addition, the 95% lower confidence limits on group mean force also remain above the minimum required values through T = 100 years.

Forces in the Unit 1 and Unit 2 replaced tendons are expected to remain well above those in the originally installed tendons.

5.1.2 Condition of End Anchorage Hardware / Concrete and Extracted Wires

Enclosed end anchorage hardware and tendon wire s extracted for tensile testing show no signs of corrosion. Only one small area of Level 4 corrosion was found on a vertical tendon bottom end bearing plate. Else, reported c orrosion levels either 1 (A) or 2 (B).

With the exception covered in the following paragraph, broken wires and missing /

protruding button heads represent only a miniscule fraction of the number of installed tendon wires. And, since completion of the 2003- 04 tendon replacement work (see below), only 3 new (not previously documented) protruding / missing button heads or broken wires have been found.

During the 2003 surveillance, 6 Unit 1 and 2 Unit 2 vertical tendons were found to have multiple broken wires. Wire failure was ascribed to corrosion resulting from a combination of water intrusion through damaged / degraded end anchorage access well cover plate gaskets and insufficient CPM coverage. Tendons with broken wires were replaced in 2004- 05, new CPM was injected, cover plate gaskets were replaced and bottom end cap CPM leaks were seal ed. Examinations performed since the completion of these corrective actions have uncovered no recurrence of water intrusion, corroded wire or, with LAS RR Technical Report Page 45 of 77 Revision 0 / 20230214

the exception noted in the above paragraph, broken / missing wires that were not previously documented.

Free water was documented at only 13 surveillance tendon anchorage areas ; in all cases, quantities were estimated at 12 oz or less. The 12 oz sample was tested for pH and found to be alkaline with a pH of 9.02 which is consider ed acceptable.

No end anchorage hardware was found to be cracked or distorted.

No anchorage area concrete cracks wider than 0.01 inches were reported.

5.1.3 Tendon Wire Strength and Ductility

Tensile tests on samples cut from extracted wires show, with unique exceptions attributed to probable misapplication of test procedures and equipment, that ultimate strength and ductility (quantified by the measured elongation at failure) remain above specified minimum values. Test results also show that strength and ductility are not decreasing over time.

5.1.4 Corrosion Protection Medium Characteristics

Results of corrosion protection medium (CPM) tests to determine corrosive ion concentrations and absorbed water content confirm that acceptance criteria have been met. T hese parameters exhibit no discernible trends that would indicate a degradation of the CPM over time.

Results of tests to determine base number spread across a range that do not appear reasonable for the Visconorust 2090P -4 product used at LAS. As the base number test is relatively complex, it is concluded that the extreme high and low values reported are probably attributable to the incorrect use of the analytical procedures specified. When the extreme base number values are eliminated from consideration, the remaining test results meet the acceptance criterion and exhibit no discernible trends that would indicate a degradation of the CPM corrosion protection function over time.

5.2 Conclusions

Based on the evaluations detailed in Part 4 of this technical report and summarized above, it is concluded that the LAS post-tensioning system will continue to perform its design function until well beyond the maximum expected operating lifetime of the uni ts.

And, specifically that:

• Tendon group mean forces will remain above the specified minim a; LAS RR Technical Report Page 46 of 77 Revision 0 / 20230214

• End anchorage hardware and tendon wire will remain free of active corrosion.

Corrosion on exposed surfaces of bearing plates will remain minor. (Condition will be verified during Subsection IWL mandated concrete surface visual examinations) ;

• Tendon wire strength and ductility will not change over time and will remain acceptable throughout the operating lifetime of the plant ;

• Corrosion protection medium will ret ain its protective properties with no unacceptable degradation over time;

• And, free water will not be a concern.

5.3 Recommendations

On the basis of the above conclusions, it is recommended that the inter val between post -

tensioning system surveillances, which include examinations identified in Reference 6.2, Table IWL-2500- 1, Examination Category L-B, Items L2.10 through L2.50, be increased in accordance with the schedule presented in Part 2 of this report and replicated below.

Proposed Tendon Surveillance Schedule (includes the four most recent Unit 1 and Unit 2 surveillances for reference)

Units 1 & 2 Visual Examination, CPM Sampling Tendon Force Year & Testing and Free Water Measurement Collection & Testing Unit 1 Unit 2 Unit 1 and Unit 2 2003 Performed Performed Performed 2008 Performed N/A Performed 2013-14 Performed Performed N/A 2019 Performed N/A Performed 2028 a Perform Perform N/A 2038 a Perform N/A Perform 2048a Perform Perform N/A 2058a Perform N/A Perform Note a: For scheduling purposes, each future surveillance is considered to be due at mid-year and must be performed between 30 June of the year prior to the year shown and 30 June of the year following the year shown.

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Implementing this change will provide the following safety and related benefits.

• Reducing personnel exposure to a number of industrial safety hazards associated with system examination / testing. These include:

o Working at heights ;

o Working on open platfor ms with no ready means of egress or rescue in the event of sudden changes in weather or an injury accident ;

o Working in a de facto confined space (the tendon gallery) ;

o Working with high-pressure hydraulic systems; o Working around high-energy plant systems; o Working around solvent and hot petroleum product fumes ;

o Working around containers and lines filled with hot petroleum products ;

o Close in exposure to high levels of stored elastic energy in tendons (sudden rotation during force measurement has resulted in rapid shim ejection);

o Handling heavy loads, often in the vicinity of critical plant components.

• Reducing potentially damaging repetitive loading on tendons during de-tensioning / re-tensioning as well as during implementation of force measurement procedures.

• Reducing end anchorage exposure to the elements during periods when end caps are removed for examination, force measurement and wire extraction.

• Reducing radiation exposure.

It is also recommended that removal and testing of tendon wires be done only when specified by the Responsible Engineer. This will eliminate the routine need to de-tension and re-tension tendons and the consequent possible damage to the remaining wires.

In addition, it is recommended that routine CPM testing be limited to determination of absorbed water content and that additional tests for corrosive ion concentration and neutralization number be performed only if:

• Active corrosion is found on anchorage components and / or tendon wires;

• Free water is found at anchorages;

• CPM absorbed water content exceeds the Table IWL-2525-1 acceptance limit;

• And, otherwise if specified by the Responsible Engineer.

Eliminating routine ion concentration and neutralization number testing has the benefit of reducing the quantity of hazardous reagents to be disposed of by the testing laboratory.

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6. REFERENCES

6.1 USNRC Regulation 10CFR50.55a, Codes and standards.

6.2 ASME Boiler and Pressure Vessel Code,Section XI, Subsection IWL, Requirements for Class CC Concrete Components of Light -Water-Cooled Plants, (2007 Edition with 2008 Addenda).

6.3 LaSa lle Station, Final Safety Analysis Report, Par. 7.5.2.1.3.a, Page 7.5-2a Revision 21, July 2015.

6.4 LaS alle Station Unit 2 Drawing S-831, Reactor Containment / Post-Tensioning Tendons, Revision E.

6.5 LaS alle Station Unit 2 Drawing 1-CISI-2000, Sheet 1, IWE/IWL Component Drawing / Reactor Containment / Post Tension system & Vent / System General Arrangement, Revision B.

6.6 ASTM A421, Specification for Uncoated Stress Relieved Wire for Prestressed Concrete, Published by the American Society for Testing and Materials.

6.7 LaS alle Station Unit 1 Drawing 1-CISI-2000, Sheet 2, IWE/IWL Component Rollout

/ Outside Containment / 0° to 360° Azimuth, Revision A.

6.8 LaS alle Station Unit 1 Drawing 1-CISI-2000, Sheet 4, IWL Component Drawing /

Tendon Gallery Ceiling / Bearing Plate Locations, Revision B.

6.9 LaS alle Station Unit 1 Drawing 1-CISI-2000, Sheet 5A, IWL Component Drawing /

Reactor Containment / Group A Vertical Tendon / Upper Bearing Plate Locations,

Revision A.

6.10 LaS alle Station Unit 1 Drawing 1-CISI-2000, Sheet 5B, IWL Component Dr awing /

Reactor Containment / Group B Vertical Tendon / Upper Bearing Plate Locations,

Revision B.

6.11 LaS alle Station Unit 1 Drawing 1-CISI-2000, Sheet 5C, IWL Component Drawing

/ Reactor Containment / Group C Vertical Tendon / Upper Bearing Plate Locations, Revision A.

6.12 LaSalle Station / Unit 1, Unit 2 Common / Administrative Procedure, Inservice Inspection Program for Post -Tensioning Tendons, LAP-100- 51, Revision 9, June 29, 2018.

6.13 USNRC Regulatory Guide 1.35, Inservice Inspection of Ungrouted Tendons in Prestressed Concrete Containments, Revision 3.

6.14 29 December 1980 letter from Wiss, Janney, Elstner and Associates to Sargent &

Lundy Engineers, Grease and Wire Testing for LaSalle Station, WJE No. 80122Q.

6.15 Response to US NRC Staff Request for Additional Information, LaSalle County Station Units 1 and 2, CECo Request for Amendment to Post -Tensioning ISI Technical Specification, RAI dated 02 December 1993.

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6.16 Engineering Evaluation Report for Containment Tendon Wire Strength / LaSalle County Station Units 1 & 2 / Job No. 8406-20, report prepared for Commonwealth Edison Company by Sargent & Lundy Engineers, September 20, 1988.

6.17 LTS-1000- 1, 1992 Tendon Surveillance for Unit 1, Document No. 0002851633, Document Date 01 January 1992, File Location LAQAVT / Roll 002535, (Beginning) Frame 2648, Quantity 0226 (Frames), Archived 18 May 2001. [Unit 1 15th Year surveillance]

6.18 [Unit 2 10th Year Surveillance] Work Request / Work Package No. L20600, Assist Tech. Staff in Performing Grease Sam ples and Visual Inspections on the Tendons Listed on the Attached Work Requestto Be Performed per Applicable Portions of Attached Procedure LTS -1000- 1 Sections 2 & 4, Revision 0, Approved 07 October 1993.

6.19 Tensile Test of 0.250 In. Diameter Tendon Wire for Bechtel Power Corporation /

Commonwealth Edison, report prepared by Wiss, Janney, Elstner Associated, Inc.,

WJE No. 972580Q, December 9, 1997.

6.20 Procedure # LTS -1000-1, Unit 1, PM ID 0000068308, V isual ISI of Containment Post Tensioning Tendons, Due Date: 09/12/1997.

6.21 Twenty-Fifth Year Physical Surveillance of Unit 1 and Twentieth Year Visual Surveillance of Unit 2 at the LaSalle Nuclear Generating Station / Post Tensioning Surveillance Report, report prepared by Precision Surveillance Corporation, Final Revision, 08 September 2004.

6.22 Exelon Nuclear / LaSalle Station: Unit 1 and 2 / Tendon Inspection and Replacement Project / 2004, report prepared by Precision Surveillance Corporation.

6.23 Exelon Nuclear / LaSalle Station: Unit 1 and 2 / Tendon Inspection Project / 2006, report prepared by Precision Surveillance Corporation, ( revision & date not noted in report).

6.24 Exelon Nuclear / LaSalle Station: Unit 1 and 2 / Tendon Inspection Project / 2007, report prepared by Precision Surveillance Corpor ation, 11 December 2007.

6.25 Final Report / LaSalle Station Unit 1 Visual 30 th Year (8th Period) & Unit 2 Physical 25th Year (7th Period) Containment Building Tendon Surveillance, Document No.

LS-N1030- 500, report prepared by Precision Surveillance Corporation, Revision 1, 08 November 2010.

6.26 Final Report for the 35th Year Unit 1 and 30 th Year Unit 2 Tendon Surveillance at LaSalle Nuclear Power Plant, report prepared by Precision Surveillance Corporation, Revision 1, 10 September 2014.

6.27 Final Report for the 40th Year Unit 1 and 35 th Year Unit 2 Tendon Surveillance at LaSalle, report prepared by Precision Surveillance Corporation, Revision 0, 31 July 2019.

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6.28 ISI Classification Basis Document / LaSalle County Generating Station Units 1 &

2 / Fourth Interval, document prepared by True North Consulting, LLC, Document No. LS8743R06- 03, Revision 0.

6.29 United States Code of Federal Regulations / Title 10 / Part 50 / Appendix J, Primary Reactor Containment Leakage Testing for Water -Cooled Power Reactors.

6.30 ANSI/ANS 56.8-1992 (or later issue), Containment System Leakage Testing Requirements, an American National Standard published by the American Nuclear Society.

6.31 Miller, Irwin and John E. Freund, Probability and Statistics for Engineers, Prentice-Hall, Englewood Cliffs, NJ, 1965.

6.32 AR 00157920, Degraded Tendon, Originated 08 May 2003.

6.33 LTS-1000- 1, Physical ISI of Post Tensioning Tendons [for Unit 2], Document No.

0005977597, Document Date 25 June 1997 (Work Completed), File Location LAQAVT / Roll 005499, (Beginning) Frame 0525, Quantity 0200 (Frames),

Archived 18 May 2001 (Physical); and LTS -1000- 1, Visual ISI of Post Tensioning Tendons [for Unit 2], Document No. 0005977737, Document Date 25 June 1997 (Work Completed), File Location LAQAVT / R oll 005499, (Beginning) Frame 0725, Quantity 0002 (Frames), Archived 18 May 2001 (Visual). [Unit 2 15 th Year surveillance]

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7. TABLES AND FIGURES

Tables and figures cited in the above text follow.

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Table 1 - List of US Containments1 with Ungrouted Pre-stressing Systems Plant / Unit Containment Type2 / Notation3 Millstone 2 Shallow dome w / hoop, vertical & dome tendon groups; B Ginna Vertical tendons only; anchored in rock; B TMI 1 Shallow dome w / hoop, vertical & dome tendon groups; B; N Calvert Cliffs 1 & 2 Shallow dome w / hoop, vertical & dome tendon groups; B V. C Summer Shallow dome w / hoop, vertical & dome tendon groups; B Oconee 1, 2 & 3 Shallow dome w / hoop, vertical & dome tendon groups; B Vogtle 1 & 2 Hemispherical dome w / hoop & inverted U tendon groups; S Crystal River 3 Shallow dome w / hoop, vertical & dome tendon groups; B; N Turkey Point 3 & 4 Shallow dome w / hoop, vertical & dome tendon groups; B Farley 1 & 2 Shallow dome w / hoop, vertical & dome tendon groups; B Palisades Shallow dome w / hoop, vertical & dome tendon groups; B; N Zion 1 & 2 Shallow dome w / hoop, vertical & dome tendon groups; B: N Braidwood 1 & 2 Shallow dome w / hoop, vertical & dome tendon groups; B Byron 1 & 2 Shallow dome w / hoop, vertical & dome tendon groups; B LaSalle 1 & 2 BWR Mark II (cylinder - cone) containment w / hoop & vertical tendon groups; B Point Beach 1 & 2 Shallow dome w / hoop, vertical & dome tendon groups; B Callaway Hemispherical dome w / hoop & inverted U tendon groups; B ANO 1 & 2 Shallow dome w / hoop, vertical & dome tendon groups; B South Texas 1 & 2 Hemispherical dome w / hoop & inverted U tendon groups; B Wolf Creek Hemispherical dome w / hoop & inverted U tendon groups; B Ft. Calhoun Shallow dome with spiral and dome tendon groups; B; N Palo Verde 1, 2 & 3 Hemispherical dome w / hoop & inverted U tendon groups; B San Onofre 1 & 2 Hemispherical dome w / hoop & inverted U tendon groups; S; N Rancho Seco Shallow dome w / hoop, vertical & dome tendon groups; S; N Trojan Hemispherical dome w / hoop & inverted U tendon groups; B; N Note 1: Bellefonte 1 & 2, which are still under construction, Midland 1 & 2, which were terminated prior to fuel load and Robinson & TMI 2, which have grouted tendon systems, are not listed.

Note 2: All units are PWRs except LaSalle (BWR).

Note 3: B - BBRV system with button headed wires; S - strand system with wedge anchors; N - unit(s) are no longer in operation.

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Table 2 - Summary of Unit 1 Hoop Tendon Forcesa, Sh. 1 Surveillance T, Time

/ Calendar Since SIT, Tendon FM, Measured Force, kip Year Years H1CB 694 H12AC 675 H12CB 694 H20CBc 652 1 / 1980 1.6 H21AC 671 H48ACb 697 H56BA 681 H56CB 709 H70B 698 H2CBc 662 H14AC 654 H24BA 666 3 / 1982 3.4 H37CB 658 H47CB 672 H48ACb 676 H57CB 702 H60B 684 H3BA 676 H12BA 650 H21CB 643 H23BAc 628 5 / 1983 4.9 H38CB 643 H48ACb 669 H49AC 658 H68B 658 H4BAc 643 10 / 1988 9.6 H41CB 676 H48ACb 678 H50AC 667

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Table 2 - Summary of Unit 1 Hoop Tendon Forcesa, Sh. 2 Surveillance T, Time

/ Calendar Since SIT, Tendon FM, Measured Force, kip Year Years H57AC 666 H48ACb 663 15 / 1992 14.0 H53BA 647 H50CBc 665 20 / 1997 18.4 Visual examination only H1BA 629 H47ACc 644 25 / 2003 24.7 H48ACb 661

H57BA 654 30 / 2008 29.9 Visual examination only H48ACb 674 35 / 2013 - H49CB 665 2014 35.0 H51BAc 668 H58BA 659 40 / 2019 40.3 Visual examination only Note a: Surveillance year 1-25 measured force data from Reference 6.21, pp.

92-93; year 35 data from Reference 6.26.

Note b: Common tendon.

Note c: T endon de-tensioned for test wire removal.

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Table 3 - Summary of Unit 1 Vertical Tendon Forcesa, Sh. 1 Surveillance T, Time

/ Calendar Since SIT, Tendon FM, Measured Force, kip Year Years V15A 690 V15Cb 690 1 / 1980 1.6 V20A 690 V29A 678 V47Cc 690 V6C 683 V15Cb 690 3 / 1982 3.4 V17A 675 V32C 683 V42Cc 675 V5B 673 V15Cb 677 V23A 666 5 / 1983 4.9 V27A 688 V28A 628 V29A 658 V31Cc 673 V15Cb 648 10 / 1988 9.6 V22Ac 666 V30B 651 V19Ac 631 V21Ac 667 15 / 1992 14.0 V13B 643 V15Cb 657 V18A 653 V20A 634

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Table 3 - Summary of Unit 1 Vertical Tendon Forcesa, Sh. 2 Surveillance T, Time

/ Calendar Since SIT, Tendon FM, Measured Force, kip Year Years V5Cc 645 V12C 635 V15Cb 645 V1A 643 V2A 630 V4A 645 V5A 660 V6A 629 V7A 644 V8A 660 V9A 651 V10A 651 25 / 2003 24.7 V11A 651 V14A 638 V15A 645 V16A 618 V17A 632 V18A 657 V19A 636 V20A 635 V26A 639 V27A 657 V28A 624 V30A 669 V58C 651

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Table 3 - Summary of Unit 1 Vertical Tendon Forcesa, Sh. 3 Surveillance T, Time

/ Calendar Since SIT, Tendon FM, Measured Force, kip Year Years 30 / 2008 29.9 Visual examination only V15A 681 V15Cb 643 35 / 2013-V35Cc 640 2014 35.0 V52C 640

V56C 637 40 / 2019 40.3 Visual examination only Note a: Surveillance year 1-25 measured force data from Reference 6.21, pp.

95-97; year 35 data from Reference 6.26.

Note b: Common tendon.

Note c: T endon de-tensioned for test wire removal.

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Table 4 - Summary of Unit 2 Hoop Tendon Forcesa, Sh. 1 Surveillance T, Time

/ Calendar Since SIT, Tendon FM, Measured Force, kip Year Years H1GF 677 H12EG 635 H12GF 639 H20GFc 650 1 / 1984 0.9 H48EGb 666

H56GF 649 H56FE 647 H70F 666 H2GFc 675 H14EG 618 H24FE 626 H37GF 648 3 / 1986 3.5 H46GF 630 H47GF 631 H48GF 649 H48EGb 660 H57GF 634 H60F 638 H3FE 650 H12FE 633 H21GF 650 H23FEc 641 5 / 1988 5.3 H38GF 664 H48EGb 662 H49EG 665 H68F 659 10 / 1993 10.4 Visual examination only H48EGb 653 H50GFc 660 15 / 1997 14.0 H53FE 645

H57EG 666 20 / 2012 20.2 Visual examination only

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Table 4 - Summary of Unit 2 Hoop Tendon Forcesa, Sh. 2 Surveillance T, Time

/ Calendar Since SIT, Tendon FM, Measured Force, kip Year Years H1FE 631 H47EGc 627 25 / 2008 25.4 H48EGb 636

H57FE 630 30 / 2013-30.5 Visual examination only 2014 H48EGb 640 35 / 2019 35.8 H49GF 633 H51FEc 638 H60F 641 Note a: Data from Reference 6.27, Table 12-1.

Note b: Common tendon.

Note c: T endon de-tensioned for test wire removal.

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Table 5 - Summary of Unit 2 Vertical Tendon Forcesa, Sh. 1 Surveillance T, Time

/ Calendar Since SIT, Tendon FM, Measured Force, kip Year Years V214A 667 V215A 637 V215Cb 663 1 / 1984 0.9 V216A 667 V220A 655 V229A 644 V247Cc 667 V206C 646 V215Cb 649 3 / 1986 3.5 V217A 646 V232C 659 V242Cc 654 V205B 666 V215Cb 651 5 / 1988 5.3 V223A 666 V228A 651 V231Cc 659 10 / 1993 10.4 Visual examination only V215Cb 628 15 / 1997 14.0 V219Ac 644 V213B 667

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Table 5 - Summary of Unit 2 Vertical Tendon Forcesa, Sh. 2 Surveillance T, Time

/ Calendar Since SIT, Tendon FM, Measured Force, kip Year Years V201A 614 V202A 642 V203A 627 V204A 650 V205A 609 V212A 624 V213A 651 V214A 625 V215A 628 V216A 645 V217A 632 20 / 2003 20.2 V218A 624 V220A 626 V221A 630 V222A 623 V223A 650 V224A 624 V225A 630 V226A 606 V227A 624 V228A 612 V229A 618 V230A 642 V247C 622

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Table 5 - Summary of Unit 2 Vertical Tendon Forcesa, Sh. 3 Surveillance T, Time

/ Calendar Since SIT, Tendon FM, Measured Force, kip Year Years V204A 646 V212A 619 V225A 625 25 / 2008 25.4 V204Cc 660 V205C 649 V215Cb 623 V257C 632 30 / 2013-30.5 Visual examination only 2014 V215Cb 634 35 / 2019 35.8 V230A 658 V235Cc 634

Note a: Data from Reference 6.27, Table 12-3.

Note b: Common tendon.

Note c: T endon de-tensioned for test wire removal.

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Tab l e 6a - U ni t 1 W i re Te st Re sul ts / U l ti mate Te nsi l e Stre ngth Ex am U l ti mate Te nsi l e Stre ngth, ksi W i re Ex am Y e ar / Te ndon Spe ci me n 1 Spe ci me n 2 Spe ci me n 3 Spe ci me n 4 M e an, ks i M e an, ks i Y e ar 1a / H20C B 259 259 260N/A 259254 1980 V 47C 252 251 245 N/A 249 3a / H2C B 257 255 257N/A 256252 1982 V 42C 250 249 246 N/A 248 5a / H23B A 256 257 257N/A 257 252 1983-84 V 31C 247 248 248 N/A 248 10a / H4B A 250 248 256N/A 251246 1988 V 22A 240 242 240 N/A 241 H50C B 256 255 255 N/A 255 15b / V 19A 246 249 251 N/A 249249 1992 V 21A 243 244 244 N/A 244

25c / H47A C 256 260 259 N/A 258265 2003 V 5C 274 271 271 N/A 272 35c / H51B A 250 244 247 246 247248 2013-14 V 35C 251 248 252 N/A 250

Note a: Data from Refrence 6.16.

Note b: Data from Reference 6.17.

Note c: 25th and 35th ye ar data f rom appl i cabl e surve i l l ance re ports.

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Tab l e 6b - Unit 1 Wire Test Results / Elongation at Failure

( Hi ghl i ghte d ce l l s contai n val ue s not me e ti ng the 4.0% mi ni mum e l ongati on cri te ri on)

Ex am Elongation at Failure, % W i re Ex am Y e ar / Te ndon Spe ci me n 1 Spe ci me n 2 Spe ci me n 3 Spe ci me n 4 M e an, % M e an, %

Y e ar 1a / H20C B 4. 5 4.8 5. 2N/A 4. 85. 4 1980 V 47C 6. 3 6.3 5. 1 N/A 5. 9 3a / H2C B >4. 0 >4. 0 >4. 0N/A >4. 0>4. 0 1982 V 42C >4. 0 >4. 0 >4. 0 N/A >4. 0 5a / H23B A >4. 0 >4. 0 >4. 0N/A >4. 0>4. 0 1983-84 V 31C >4. 0 >4. 0 >4. 0 N/A >4. 0 10a / H4B A 5. 7 4.8 5. 2N/A 5. 24. 9 1988 V 22A 4. 0 4.5 5. 3 N/A 4. 6 H50C B 5. 0 5.1 5. 0 N/A 5. 0 15b / V 19A 4. 4 3.8 4. 1 N/A 4. 14. 2 1992 V 21A 3. 8 3.4 3. 4 N/A 3. 5

25c / H47A C 4. 3 5.2 4. 5 N/A 4. 75. 4 2003 V 5C 6. 3 6.2 5. 8 N/A 6. 1 35c, d / H51B A 4. 8 3.9 4. 3 4. 34. 34. 3 2013-14 V 35C 4. 2 4.6 4. 2 N/A4. 3 Note a: Data from Reference 6.16.

Note b: Data from Reference 6.17.

Note c: 25th and 35th ye ar data f rom appl i cabl e surve i l l ance re ports.

N o t e d : H 51B A s p e c i m e n 3 e l o n g a t i o n a t f a l l u r e a d d r e s s e d i n N C R - F N 1090- 004.

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Tab l e 7a - U ni t 2 W i re Te st Re sul ts / U l ti mate Te nsi l e Stre ngth

( Hi ghl i ghte d ce l l contai ns val ue not me e ti ng the 240 ksi mi ni mum stre ngth cri te ri on)

Ex am U l ti mate Te nsi l e Stre ngth, ksi W i re Ex am Y e ar / Te ndon Spe ci me n Spe ci me n Spe ci me n Spe ci me n Spe ci me n M e an, ks i M e an, ks i Y e ar 1 2 3 4 5 1a / H20GF 250 253 252 250250 251248 1984 V 247C 240 246 240 N/A N/A 242 3a / H2GF 255 252 250N/A N/A 252248 1986 V 242C 244 246 242 N/A N/A 244 5a / H23F E 248 248 248N/A N/A 248244 1988 V 231C 240 240 237 N/A N/A 239 15b / H50GF 256 260 261 N/A N/A 259254 1997 V 219A 250 249 248 N/A N/A 249 25 / H47EG 263 262 263 N/A N/A 263261 2008c V 204C 256 260 263 N/A N/A 260

35 / H51F E 244 248 250 N/A N/A 247248 2019c V 235C 251 248 247 N/A N/A 249

Note a: Data from Reference 6.16.

Note b: Data f rom Re f e re nce s 6.19 ( te st re sul ts) and 6.33 ( te ndon ID)

Note c: 25th and 35th ye ar data f rom appl i cabl e surve i l l ance re ports.

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Table 7b - Unit 2 Wire Test Results / Elongation at Failure Ex am Elongation at Failure, % W i re Ex am Y e ar / Te ndon Spe ci me n Spe ci me n Spe ci me n Spe ci me n Spe ci me n M e an, % M e an, %

Y e ar 1 2 3 4 5 1a / H20GF 5. 0 5. 0 4.5 5. 04. 5 4. 84. 8 1984 V 247C 5. 0 4. 5 5.0 N/A N/A 4. 8 3a / H2GF >4. 0 >4. 0 >4. 0N/A N/A >4. 0>4. 0 1986 V 242C >4. 0 >4. 0 >4. 0 N/A N/A >4. 0 5a / H23F E N/A 4. 0 N /AN/A N/A 4. 04. 7 1988 V 231C 4. 8 5. 5 4.4 N/A N/A 4. 9 15b / H50GF 4. 2 4. 9 4.9 N/A N/A 4. 74. 7 1997 V 219A 4. 3 5. 0 4.7 N/A N/A 4. 7 25 / H47EG 4. 1 4. 2 4.1 N/A N/A 4. 14. 2 2008c V 204C 4. 4 4. 2 4.0 N/A N/A 4. 2

35 / H51F E 4. 4 4. 0 4.6 N/A N/A 4. 34. 4 2019c V 235C 4. 2 5. 0 4.0 N/A N/A 4. 4

Note a: Data from Reference 6.16.

Note b: Data f rom Re f e re nce s 6.19 ( te st re sul ts) and 6.33 ( te ndon ID)

Note c: 25th and 35th ye ar data f rom appl i cabl e surve i l l ance re ports.

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Figure 1 - Unit 1 Hoop Tendon Force Trend & LCL

750

Lift-Off Force Data Point (Typ)

700 Hoop Tendon Mean Force Trend Line F (kip) = 681.7 - 19.52

• Log10 (T)

650

600 Minimum Required Mean Hoop Tendon Force FMin = 575 kip 95% LCL on Mean Force

550 1 10 100 T, Time Since SIT, Years (Logarithmic Scale)

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Figure 2 - Unit 1 Hoop Common Tendon H48AC Force Trend

750

700 Hoop Common Tendon Mean Force Trend Line F (kip) = 690.4 - 17.69

• Log10 (T)

650 Lift-Off Force Data Point (Typ)

600

550 1 10 100 T, Time Since SIT, Years (Logarithmic Scale)

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Figure 3 - Unit 1 Vertical Tendon Force Trend & LCL

750

Vertical Tendon Mean Force Trend Line F (kip) = 693.6 - 35.38

• Log10 (T) Lift-Off Force 700 Data Point (Typ)

650 95% LCL on Mean Force

600

Minimum Required Mean Verticall Tendon Force FMin = 600 kip

550 1 10 100 T, Time Since SIT, Years (Logarithmic Scale)

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Figure 4 - Unit 1 Vertical Common Tendon V15C Force Trend

750

Vertical Common Tendon Mean Force Trend Line F (kip) = 702.1 - 40.74* Log10 (T)

700

Lift-Off Force Data Point (Typ)

650

600

550 1 10 100 T, Time Since SIT, Years (Logarithmic Scale)

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Figure 5 - Unit 2 Hoop Tendon Force Trend & LCL

750

Hoop Tendon Mean Force Trend Line F (kip) = 652.5 - 8.49

• Log10 (T) 700

Lift-Off Force Data Point (Typ)

650

600 Minimum Required Mean Hoop Tendon Force 95% LCL on Mean Force FMin = 575 kip

550 0.1 1 10 100 T, Time Since SIT, Years (Logarithmic Scale)

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Figure 6 - Unit 2 Hoop Common Tendon H48EG Force Trend

750

Hoop Common Tendon Mean Force Trend Line F (kip) = 669.4 - 18.65

• Log10 (T)

700

Lift-Off Force Data Point (Typ)

650

600

550 0.1 1 10 100 T, Time Since SIT, Years (Logarithmic Scale)

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Figure 7 - Unit 2 Vertical Tendon Force Trend & LCL

750

700 Vertical Tendon Mean Force Trend Line F (kip) = 660.0 - 19.82

• Log10 (T)

Lift-Off Force Data Point (Typ)

650

95% LCL on Mean Force

600

Minimum Required Mean Verical Tendon Force FMin = 600 kip

550 0.1 1 10 100 T, Time Since SIT, Years (Logarithmic Scale)

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Figure 8 - Unit 2 Vertical Common Tendon V215C Force Trend

750

700

Vertical Common Tendon Mean Force Trend Line F (kip) = 662.2 - 23.55

• Log10 (T)

650

600 Lift-Off Force Data Point (Typ)

550 0.1 1 10 100 T, Time Since SIT, Years (Logarithmic Scale)

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Attachment 1 - Trend Line Parameter and Confidence Limit Formulae

The following regression line parameter and confidence limit formulae are those developed in Reference 6.31.

Values of Fi and Ti documented in lift-off force / time data sets are represented by y i and xi, respectively, in the formulae summarized below. The number of lift -off force / time data sets used to construct the trend line (regression line) and 95% lower confidence limit (LCL) curve is represented by n.

Summations used to compute regression line slope (b), intercept (a), and LCL curve are (with all summations from 1 to n):

Sxx = n * ( xi

• xi ) - ( xi)2

Syy = n * (y i

• yi ) - ( yi)2

Sxy = n * (x i

• yi ) - ( xi) * ( y i)

xm = ( x i) / n

ym = ( y i) / n

Regression line slope, b = S xy / Sxx

Regression line intercept, a = y m - b

• xm

The standard error of estimate, s e, used to compute ordinates on the LCL curve defined by the following expression.

se = {[Sxx

• Syy - (Sxy)2 ] / [n * (n - 2)

• Sxx]}1/2

The curve representing the 95% LCL is constructed using the following expression where yLCLi is the ordinate of the curve at an abscissa value of x i and t0.05 is Students t statistic16 for a confidence level of 95% and n - 2 degrees of freedom.

yLCLi = (a + b

• xi) - t0.05

• se * [(1 / n) + n * (xi - xm)2 / Sxx]1/2

16 Values of t0.05 for selected values of v = n - 2 are listed Table IV of Reference 6.31. Values of t0.05 used in this report were obtained from an online calculator which was verified by comparing calculator output to Table IV entries.

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Attachment 2 - Containment Vertical Cross-Section Drawing

Exelon Drawing 1-CISI-2000 / Sheet 1 (Reference 6. 5) is reproduced on the following page.

8 7

'HS 000<'.-ISIJ-l

---

7 I I I I I I 1-r--..._J I I I I 6 i

1-CISI-2000, SH. 5A A DRYER SEPERATOR i---r- - "'1-..j : j' STORAGE POOL I I I

1-CISl-2000. SH. 58 tB EL. 823'-6" I I EL. 818'-0" GROUP "8" VERTICAL TENDON UPPER BEARING PLATES GROUP "C:' VERTICAL TENDON UPPER BEARING PLATES 1-CISI-2000, SH. SC rc VACUUM BREAKER LINES SEE DWGS 1-CISl-1000, SHEETS 1JA, 136, 13C & 130 8 EL. 710*-6" FOR LOWER VERTICAL TENDON BEARING PLATES SEE DRAWING 1-CISl-2000, SH. 4 7 EL. 807'-0"

'.(I

\\CON i FIL

),

CONTAINMENT REACTOR CONTAINMENT 6 5 GROUP ",.;' VERTICAL TENDON UPPER BEARING PLATES GROUP "B" VERTICAL TENDON UPPER BEARING PLATES ;.

SPENT FUEL STORAGE POOL 4 EL !HJ'-6" B__EfUEL _ _FLOOR EL. 815'-2V2" EL. 804'-9" GROUP "(:' VERTICAL TENDON UPPER BEARING PLATES 5 EL. 786'-6" c1 CONCRETE CONTAINMENT EXTERIOR SURFACE ROLLOUT SEE DRAWING 1-CISI-2000, SH. 2 (NOTE 1)

EL. 761'-:-0" EL. 740*-0*

VENT SYSTEM DOWNCOMMERS SEE DRAWING 1-CISl-1000, SHTS. 12A & 12B FLOOR EL. 710'-6" El. 710"-0" GRADE LINE EL. 673'-4" 4 3 3 2 NOTES:

1. FOR HORIZONTAL TENDON BEARING PLATE LOCATIONS SEE DRAWING 1-CISl-2000, SH. 2.

REFERENCE DWG'S:

S-325 S-331 LAS RR Technical Report Page 77 of 77 Revision 0 / 20230214 xeJs,-

.aSalleSTation I Un,L J

• 2 IWE/IWL COMPONENT DRAWH REACTOR CONTAINMENT POST TENSION SYSTEM & VEI SYSTEM GENERAL ARRANGEMEI 12/21/Q,g 1-c1s1-200e SHEET NO: 1 ISIZE: F