ML20280A508

Submittal of Relief Request CISI-03-01 Concerning Containment Unbonded Post-Tensioning System Inservice Inspection Requirements

ML20280A508
Person / Time
Site:	Calvert Cliffs
Issue date:	10/06/2020
From:	David Helker Exelon Generation Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
CISI-03-01
Download: ML20280A508 (122)

Text

200 Exelon Way Kennett Square, PA 19348 www.exeloncorp.com 10 CFR 50.55a October 6, 2020 U.S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555-0001 Calvert Cliffs Nuclear Power Plant, Units 1 and 2 Renewed Facility Operating License Nos. DPR-53 and DPR-69 NRC Docket Nos. 50-317 and 50-318

Subject:

Submittal of Relief Request CISI-03-01 Concerning Containment Unbonded Post-Tensioning System Inservice Inspection Requirements Attached for your review is a relief request associated with the third Containment Inservice Inspection (CISI) interval for the Calvert Cliffs Nuclear Power Plant, Units 1 and 2.

CISI-03-01 concerns requirements associated with the Containment Inservice Inspection program. The third CISI interval complies with the 2013 Edition of the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel (B&PV) Code. The third CISI interval began on July 1, 2019 and is currently scheduled to end June 30, 2029.

We request your approval by October 6, 2021.

There are no regulatory commitments in this letter.

If you have any questions concerning this letter, please contact Tom Loomis at (610) 765-5510.

Respectfully, David P. Helker Sr. Manager - Licensing & Regulatory Affairs Exelon Generation Company, LLC

Attachment:

Relief Request CISI-03-01 cc: Regional Administrator, Region I, USNRC USNRC Senior Resident Inspector, CCNPP Project Manager, USNRC S. Seaman, State of Maryland

Attachment Relief Request CISI-03-01

10 CFR 50.55a Relief Request CISI-03-01 Revision 0 (Page 1 of 6)

Request for Relief CISI-03-01 for Containment Unbonded Post-Tensioning System Inservice Inspection Requirements in Accordance with 10 CFR 50.55a(z)(1)

1. ASME Code Component(s) Affected Code Class: CC

Reference:

IWL-2421, IWL-2520, Table IWL-2500-1 Examination Category: Table IWL-2500-1, Examination Category L-B Item Number: L2.10, L2.20, L2.30, L2.40, and L2.50

Description:

Examination of unbonded post-tensioning system.

Component Number: Calvert Cliffs Nuclear Power Plant (CCNPP), Units 1 and 2 Concrete Containment

2. Applicable Code Edition and Addenda

The third Containment Inservice Inspection Inservice Inspection (CISI) program is based on the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel (B&PV) Code,Section XI, 2013 Edition. The third CISI interval began on July 1, 2019 and is currently scheduled to end June 30, 2029.

3. Applicable Code Requirement

IWL-2421(b) states that when the conditions of IWL-2421(a) are met, the inspection dates and examination requirements may be as follows:

1. For the containment with the first Structural Integrity Test, all examinations required by IWL-2520 shall be performed at 1, 3, and 10 years and every 10 years thereafter. In addition, the examinations required by IWL-2524 and IWL-2525 shall be performed at 5 and 15 years and every 10 years thereafter.

2. For each subsequent containment constructed at the site, all examinations required by IWL-2520 shall be performed at 1, 5, and 15 years and every 10 years thereafter. In addition, the examinations required by IWL-2524 and IWL-2525 shall be performed at 3 and 10 years and every 10 years thereafter.

In accordance with IWL-2420(c), the 10-year and subsequent examinations shall commence not more than 1 year prior to the specified dates and shall be completed not more than 1 year after such dates. If plant operating conditions are such that examination of portions of the post-tensioning system cannot be completed within this stated time interval, examination of those portions may be deferred until the next regularly scheduled plant outage.

The 5-year examination date for each unit was determined based on the completion dates of the examinations conducted for the first CISI interval. The examinations dates for the first CISI interval were September 9, 2001 for Unit 1 and September 9, 2002 for Unit 2. Since performance of the first CISI interval examinations, CCNPP, Units 1 and 2 have performed all examinations required by IWL-2500 at the required frequency. Therefore, CCNPP, Units 1 and 2 will continue to use the first CISI interval examination date to establish the schedule for future IWL examinations in accordance with IWL-2421.

10 CFR 50.55a Relief Request CISI-03-01 Revision 0 (Page 2 of 6)

In accordance with IWL-2420(d), tendons affected by repair/replacement activities shall be examined in accordance with the requirements of IWL-2521.2.

CCNPP, Units 1and 2 are currently required to examine the post-tensioning system every 5 years alternating between units as permitted per IWL-2421.

IWL-2500 requires examinations of the unbonded post-tensioning system be performed in accordance with the requirements of Table IWL-2500-1 (L-B), "Examination Category L-B, Unbonded Post-Tensioning System," which includes the following requirements:

• Table IWL-2500-1 (L-B), Item Number L2.10 requires that selected tendon force and elongation be measured in accordance with IWL-2522.

• Table IWL-2500-1 (L-B), Item Number L2.20 requires that tendon single wire samples be removed and examined for corrosion and mechanical damage as well as tested to obtain yield strength, ultimate tensile strength, and elongation on each removed wire in accordance with IWL-2523. The selected tendons are subsequently re-tensioned as required per IWL-2523.3 because wire removal requires de-tensioning in order to safely obtain wire samples.

• Table IWL-2500-1 (L-B), Item Number L2.30 requires that a detailed visual examination be performed on selected tendon anchorage hardware and adjacent concrete extending 2 feet from the edge of the bearing plate in accordance with IWL-2524. The quantity of free water released from the anchorage end cap as well as any that drains from the tendon during examination shall be documented.

• Table IWL-2500-1 (L-B), Item Numbers L2.40 and L2.50 require that samples of selected tendon corrosion protection medium (CPM) and free water be obtained and analyzed in accordance with IWL-2525 and IWL-2526.

4. Reason for Request

ASME Section XI requires periodic visual examination of Containment concrete as well as visual examination and physical testing of post-tensioning systems. The examination and testing to date has indicated that the post-tensioning system is expected to maintain its safety-related function through the period of extended operation. This relief request proposes to perform visual examination only of the concrete Containment and accessible steel hardware visible without tendon cover removal during the 45th year surveillance. Physical testing would be performed only if visual examination results indicate a need for such testing as determined by the Responsible Engineer (IWL-2330). The 45th year surveillance is required to be completed no later than September 9, 2022 for Unit 1 and September 9, 2023 for Unit 2. The 50th year surveillance for Unit 1 would be due September 9, 2026 plus or minus 1 year. The 50th year surveillance for Unit 2 would be due September 9, 2027 plus or minus 1 year. The 50th year surveillance will be completed during the 3rd CISI interval for both units. The proposed deferral of the physical testing of the post-tensioning system will continue to provide an acceptable level of quality and safety based on projected performance and implementation of physical testing should visual examination results indicate a need for such testing.

A summary of the proposed CISI program changes can be found in Section 1.1 of Part D of the Enclosure.

Extending the interval between post-tensioning system examinations and tests from 5 years to 10 years will continue to provide an acceptable level of quality and safety based on projected performance and implementation of physical testing, should visual examination results indicate a need for such testing.

10 CFR 50.55a Relief Request CISI-03-01 Revision 0 (Page 3 of 6)

While this relief request is based on maintaining an acceptable level of quality and safety, there are additional benefits to extending the frequency of visual examination and physical testing of unbonded post-tensioning systems. Physical testing requires exposing the involved personnel to industrial safety hazards. Removing the tendon end caps and load testing or detensioning/tensioning the tendons also unnecessarily cycles the tendons and exposes the system to an unsealed environment during testing. Below are specific hazards and undesirable conditions that would be eliminated by this proposed relief request:

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

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

3. Some areas are located in difficult to reach locations that have only one small access point (confined space program application).

4. Requires working with high pressure hydraulics.

5. Requires working in the vicinity of high energy plant systems.

6. Requires working with solvents and hot petroleum products and associated fumes.

7. Requires working with containers and pressurized lines filled with heated corrosion protection medium (grease).

8. Requires working in the vicinity of high levels of stored elastic energy (>1 million foot-pounds) in the tendons. Sudden rotation during force measurement has resulted in high speed shim ejection.

9. Handling of heavy loads (test equipment) that also exposes plant equipment to hazards as well as the involved personnel to hazards.

10. While tendon testing is most often not performed in radiation areas, there are occasionally some tendons tested in areas that involve radiation fields.

Performing examination/testing on a reduced frequency reduces the repetitive loading required for force measurement or de-tensioning and re-tensioning. Reducing the population of tendon end caps removed will minimize tendon hardware exposure to environmental conditions and will reduce environmental waste (e.g.,

solvents, used grease, other consumables).

5. Proposed Alternative and Basis for Use

Proposed Alternative In accordance with 10 CFR 50.55a(z)(1), CCNPP, Units 1 and 2 are proposing alternative examination requirements on the basis that these alternative actions will provide an acceptable level of quality and safety.

The proposed alternative from applicable ASME Section XI, Subsection IWL requirements are as follows:

• Accept the dates used during the first Containment in-service inspection interval (September 9, 2001 for Unit 1 and September 9, 2002 for Unit 2) to establish scheduling of future examinations in accordance with

10 CFR 50.55a Relief Request CISI-03-01 Revision 0 (Page 4 of 6)

IWL-2421. Since establishing these dates in the first Containment in-service inspection interval CCNPP has performed the examinations required by IWL-2500 at the required frequency (5 years +/- 1 year).

• Extend the interval between post-tensioning system examinations and tests and detailed visual examination of concrete adjacent to tendon bearing plates from 5 years to 10 years.

ASME Section XI, Subsection IWL, Table IWL-Surveillance 2500-1 Examinations Category L-B Examinations /

Unit Tests (year)

L2.10a L2.20 L2.30 L2.40b L2.50 1 N/A N/A Perform Perform Perform 50th 2 Perform N/A Perform Perform Perform 1 Perform N/A Perform Perform Perform 60th 2 N/A N/A Perform Perform Perform 1 N/A N/A Perform Perform Perform 70th, c 2 Perform N/A Perform Perform Perform Note a: Lift-off measurements alternate between units per IWL-2421 Note b: CPM testing will be limited to determination of absorbed water content except that all IWL-2525.2 required testing will be completed if any of the following are met:

- active corrosion is found on anchorage components and/or tendon wires;

- Free water is identified at anchorages;

- CPM absorbed water content exceeds Table IWL-2525-1 acceptance limit.

Note c: If operation is extended to 80 years

• Eliminate requirement for sample wire removal and testing and the associated need for tendon de-tensioning/re-tensioning.

• Reduce the number of corrosion protection medium (CPM) chemical tests.

The above proposed alternatives relate only to the post-tensioning system and the associated examinations that require close-in access to tendon end anchorage areas (Examination Category L-B). 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 ASME Section XI, Subsection IWL requirements (Examination Category L-A).

The reduced frequency of physical testing of the post-tensioning system will continue to provide an acceptable level of quality and safety based on projected performance and implementation of physical testing should visual examination results indicate a need for such testing.

CCNPP, Units 1 and 2 proposes to perform a General Visual examination and Detailed Visual examination (when required) of accessible concrete and exposed steel hardware as required by ASME Section XI, Table IWL-2500-1, Examination Category L-A, Item Numbers L1.11 and L1.12, as modified by 10 CFR 50.55a and Part D, Section 1.2 of the Enclosure. The examination and physical testing requirements of ASME Section XI, Table IWL-2500-1, Examination Category L-B, Item Numbers L2.10, L2.20, L2.30, L2.40, and L2.50 will also be performed if the General Visual examination and Detailed Visual examination identify conditions indicative of possible degradation of tendon hardware, as documented by the Responsible Engineer in an engineering evaluation. Example conditions that could require removal of the tendon end cap and further examination per Item Numbers L2.10, L2.20, L2.30, L2.40, and L2.50 are:

10 CFR 50.55a Relief Request CISI-03-01 Revision 0 (Page 5 of 6)

• Evidence of possible damage to the enclosed post-tensioning hardware as indicated by conditions such as end cap deformation found during external visual examination. Conditions observed by removal of the end cap would determine the extent of additional examinations per Item Numbers L2.10, L2.20, L2.30, L2.40, or L2.50.

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

• Evidence of corrosion protection medium leakage will be evaluated, and a plan developed that requires further investigation and corrective actions as defined in an engineering evaluation documented by the Responsible Engineer. Visual examination and physical testing of post-tensioning systems will be extended from 5 to 10 years as described in the Enclosure.

CCNPP, Units 1 and 2 will report any abnormal degradation of the concrete Containment structure in the Inservice Inspection Summary Report, of the completed examinations required by the Pre-Stressed Concrete Containment Tendon Surveillance Program, in accordance with 10 CFR 50.55a and ASME Section XI as required by Technical Specifications 5.5.6, Concrete Containment Tendon Surveillance Program."

Subsection IWL Post-Tensioning System Examination and Physical Testing Requirements and Justification for Alternative The Enclosure to this submittal provides a detailed discussion of the historical basis for examination and testing of post-tensioning systems. The Enclosure also includes the CCNPP, Units 1 and 2, specific observations that provide a basis for an alternative from the ASME Section XI examination and testing requirements included in Table IWL-2500-1, Examination Category L-B. In Sections 6.2 and 6.3 of Part D of the Enclosure, it was concluded that based on examination/testing results to date, combined with implementation of continuing actions, an acceptable level of quality and safety will be maintained.

Additional Supporting Actions The ASME Section XI, Subsection IWL programs at CCNPP, Units 1 and 2 are credited for managing degradation of the Containment. The Examination Category L-A visual examinations (every 5 years) being performed are capable of identifying conditions that would allow water intrusion into the tendons and leakage of CPM which would be precursors for providing an environment that could allow corrosion of the tendon wires or inaccessible tendon hardware covered by the tendon end cap. Such conditions would be evaluated by the Responsible Engineer to identify required additional actions to assure no corrosive environmental conditions exist.

CCNPP, Units 1 and 2 implement other inspections of the Containment concrete and exposed exterior metal components. Section 7 of Part D in the Enclosure identifies additional examinations and actions. The examinations and actions provide an additional defense in depth that supports these proposed relief requests to perform Examination Category L-B examinations/tests on a less frequent basis and offer additional assurance that performing the Examination Category L-B examinations/tests on a less frequent basis will continue to provide an acceptable level of quality and safety.

Summary and Conclusions The results of the 10 post-tensioning system inservice examinations performed between 1975 and 2016 show that the system can be expected to perform its intended function through T = 100 years which is well past the presumed unit maximum operating lifetime of 80 years. Examination Category L-A visual examinations planned for the 45th and 55th year will be adequate to determine if additional physical testing and examination per Examination Category L-B are required.

10 CFR 50.55a Relief Request CISI-03-01 Revision 0 (Page 6 of 6)

6. Duration of Proposed Alternative

This relief request will remain in effect through the remainder of the current third CISI intervals for CCNPP, Units 1 and 2 and will continue until the end of the current period of extended operation for each unit or until such time as ASME Section XI requirements are revised to address similar examination scheduling that is approved in 10 CFR 50.55a. If similar ASME Section XI examination scheduling is implemented in later versions of Section XI, this relief request would be retired and the Section XI requirements as amended by 10 CFR 50.55a would be adopted as required during subsequent CISI Interval updates. The expiration of the CCNPP extended operating license is July 31, 2034 (Unit 1) and August 13, 2036 (Unit 2).

7. Precedents

• Letter from M. Markley (U.S. Nuclear Regulatory Commission) to C. Gayheart (Southern Nuclear Operating Co., Inc.), "Vogtle Electric Generating Plant, Units 1 and 2 - Inservice Inspection Alternative VEGP-ISI-ALT-19-01 For Containment Tendon Inservice Inspection Extension (EPID No. L-2019-LLR-0017)," dated July 11, 2019 (ADAMS Accession No. ML19182A077)

• Letter from J. Danna (U.S. Nuclear Regulatory Commission) to B. Hanson (Exelon Generation Company, LLC), "Three Mile Island Nuclear Station, Unit 1 - Relief From the Requirements of the American Society of Mechanical Engineers Code RE: Examination and Testing for Containment Unbonded Post-Tensioning System (EPID L-2018-LLR-0132)," dated September 19, 2019 (ADAMS Accession No. ML19226A023)

ENCLOSURE CALVERT CLIFFS NUCLEAR POWER PLANT UNITS 1 AND 2 CONTAINMENT POST-TENSIONING SYSTEM INSERVICE INSPECTION TECHNICAL REPORT BASIS FOR PROPOSED EXTENSION OF EXAMINATION INTERVAL

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9fl7,40 TITLE: Containment P<>st~Tenskming System lnservice Inspection Technical Report llasis for Proposed 1:.xiension of Examination Interval Calvert Cliffs Nuclear Power Ph:mt, Units ! & 2 REVlE\VED:

Chris Stmtbus BCP Enginet:ring and Consult.ants AJ>E'ROVED: ~ft .2;_/~~--* * ~ - -* _'_~J/17/2- o

\ViJtiam Knous 2 o Vice President; Pn~icct Ddh er;*

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Calvert Cliffs Technical Report Page 1 of 112 Revision 1 09/15/2020 CALVERT CLIFFS NUCLEAR POWER PLANT UNITS 1 AND 2 CONTAINMENT POST-TENSIONING SYSTEM INSERVICE INSPECTION TECHNICAL REPORT BASIS FOR PROPOSED EXTENSION OF EXAMINATION INTERVAL Report Prepared by:

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

BCP Engineers and Consultants Revision 1 September 15, 2020

Calvert Cliffs Technical Report Page 2 of 112 Revision 1 09/15/2020 Table of Contents PART A - INTRODUCTION, PURPOSE AND REPORT ORGANIZATION.................................... 4

1. Introduction and Purpose ................................................................................................................ 4

2. Report Organization ......................................................................................................................... 4

3. Part A References ............................................................................................................................. 5 PART B - CONTAINMENT DESCRIPTION, ISI PROGRAM and

SUMMARY

of PROPOSED PROGRAM CHANGES............................................................................................................................. 6

1. Containment Description ................................................................................................................. 6

2. Containment ISI Program Summary Description ............................................................................ 8

3. Summary of Proposed Program Changes, Visual Examination Program Enhancements and Conclusions ............................................................................................................................................. 11

4. Part B References ........................................................................................................................... 14 PART C - BACKGROUND OF CURRENT ISI REQUIREMENTS AND BASIS FOR PROPOSED PROGRAM CHANGES ................................................................................................... 15

1. Regulatory Guide 1.35 .................................................................................................................... 15

2. ASME Section XI / Subsection IWL ................................................................................................. 17

3. USNRC Regulation 10CFR50.55a .................................................................................................... 18

4. Basis for Proposed Program Changes / Relief from 10CFR50.55a and IWL Requirements ......... 19

5. Part C References ........................................................................................................................... 25

6. Part C Tables ................................................................................................................................... 26 PART D - CALVERT CLIFFS / PROPOSED ISI PROGRAM CHANGES..................................... 28

1. Summary of Proposed Program Changes, Current Program Enhancements, Vertical Tendon Repair / Replacement Program and Conclusions .................................................................................. 28

2. Tendon Force Trends and Forecasts .............................................................................................. 34

3. Wire Examination and Test Results Evaluation............................................................................. 45

4. End Anchorage Hardware / Concrete Condition ........................................................................... 49

5. Corrosion Protection Medium Testing .......................................................................................... 56

6. Overall Summary, Conclusions and Recommendations ............................................................... 60

7. Future Examinations and Testing Enhancements ......................................................................... 64

8. Part D References ........................................................................................................................... 66

9. Part D Tables and Figures ............................................................................................................... 69

Calvert Cliffs Technical Report Page 3 of 112 Revision 1 09/15/2020 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 CPM Corrosion protection medium EF Elongation at failure FSAR Final Safety Analysis Report kip Kilo-pound (1,000 pounds) ksi Kips per square inch LCL Lower confidence limit 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

Calvert Cliffs Technical Report Part A - Page 4 of 112 Revision 1 09/15/2020 CALVERT CLIFFS NUCLEAR POWER PLANT CONTAINMENT POST-TENSIONING SYSTEM INSERVICE INSPECTION TECHNICAL REPORT BASIS FOR PROPOSED EXTENSION OF EXAMINATION INTERVAL PART A - INTRODUCTION, PURPOSE AND REPORT ORGANIZATION

1. Introduction and Purpose This report provides the technical evaluation and justification supporting the Calvert Cliffs Nuclear Power Plant request for relief to allow departure from certain containment inservice inspection (ISI) requirements specified in USNRC Regulation 10CFR50.55a (Reference 3.1) and, by reference therein, ASME Section XI, Subsection IWL (Reference 3.2). The current Calvert Cliffs containment ISI program conforms to these regulatory and code requirements.

ASME Section XI, Subsection IWL addresses requirements for concrete containment ISI.

These consist of requirements for visual examination of containment exterior surfaces as well as visual examination and testing of post-tensioning system elements. Only the requirements applicable to post-tensioning system elements are addressed in this report.

The requested relief addresses changes to current regulatory / code requirements for inservice examination of the concrete containment post-tensioning system. Relief, if granted, will result in ISI program changes that enhance personnel safety, reduce radiation exposure, eliminate unnecessary cycling of pre-stressing tendon loads and allow reallocation of plant resources to activities that enhance nuclear safety and generating efficiency.

The proposed changes to the post-tensioning ISI program will not compromise nuclear or industrial safety.

2. Report Organization The remainder of this report consists of the following 3 parts.

Part B - Containment Description, ISI Program and Summary of Proposed Program Changes Part C - Background of Current ISI Requirements and Basis for Proposed Program Changes Part D - Calvert Cliffs ISI Program Changes

Calvert Cliffs Technical Report Part A - Page 5 of 112 Revision 1 09/15/2020 Each part has its own section / paragraph numbering, reference section and tables and figures section.

3. Part A References 3.1 USNRC Regulation 10CFR50.55a, Codes and Standards.

3.2 ASME Boiler and Pressure Vessel Code,Section XI, Subsection IWL, 2013 Edition.

Calvert Cliffs Technical Report Part B - Page 6 of 112 Revision 1 09/15/2020 PART B - CONTAINMENT DESCRIPTION, ISI PROGRAM and

SUMMARY

of PROPOSED PROGRAM CHANGES

1. Containment Description The Calvert Cliffs Nuclear Power Plant is a 2 unit generating station on the western shore of Chesapeake Bay approximately 45 miles south of Annapolis Maryland. The reactor containment structures are reinforced and post-tensioned concrete pressure vessels that serve as the final barrier (after fuel cladding and the reactor coolant system pressure boundary failure) against release of radioactive material from the reactor core to the outside environment.

The major structural elements of each containment are a cylinder wall, a ring girder, a shallow dome roof and a flat foundation mat. The cylinder and dome are pre-stressed; the foundation mat is conventionally reinforced (not pre-stressed). The ring girder serves as a transition between the cylinder and the dome and provides anchorage for both vertical and dome pre-stressing tendons. The cylinder incorporates six equally spaced buttresses that provide anchorage for the circumferential pre-stressing tendons.

A carbon steel liner covers the inside surface of the containment and ensures a high degree of leak tightness during operating and accident conditions.

Principal containment dimensions, as listed in FSAR (Reference 4.1) paragraph 5.1.2.1 and shown on FSAR Figure 5-1, Sheets 1 & 2, are as follow.

Cylinder inside diameter: 130 - 0 Cylinder height from top of base mat to dome spring line: 136 - 0 Cylinder wall thickness: 3 - 9 Dome rise from spring line to soffit: 45 - 8 Dome central area thickness (increases at the periphery): 3 - 3 Foundation mat thickness: 10 - 0 Liner thickness: 1/4 (increased at support brackets and penetrations)

The containment pre-stressing system, as described in FSAR paragraphs 5.1.2.1 is summarized below.

The wall and dome are pre-stressed using 90 wire BBRV (wires anchored by cold formed button heads) tendons. The ASTM A421 (Reference 4.2) wires have a diameter of 0.250 inches and a specified minimum ultimate tensile strength of 240 ksi.

Calvert Cliffs Technical Report Part B - Page 7 of 112 Revision 1 09/15/2020 The cylindrical wall is pre-stressed with both vertical and circumferential (hoop) direction tendons.

Wall circumferential pre-stressing consists of 6 sub-groups each having 78 tendons that span 120 degrees plus the width of a buttress. Sub-groups are offset by 60 degrees to provide continuous overlap of pre-stressing force. Circumferential tendons anchor at the buttress faces.

Wall vertical pre-stressing consists of 204 tendons. Vertical tendons anchor at the top of the ring girder and the bottom of the base mat. A tunnel (the tendon access gallery) below the base mat provides access to the lower anchorages.

Dome pre-stressing consists of 3 layered sub-groups each having 68 parallel (in plain view) tendons. The layers intersect at 60 degrees. Dome tendons anchor at the vertical face of the ring girder.

Containment tendons were initially tensioned to a mean seating force of 70% to 71% of the specified minimum ultimate strength (current forces are less due to elastic shortening, concrete shrinkage, concrete creep and pre-stressing wire relaxation losses). Initial tendon forces are documented in References 4.3 and 4.4. After tendons were tensioned, the duct, trumpet and end anchorage caps were filled with a micro-crystalline wax for corrosion protection.

Calvert Cliffs Technical Report Part B - Page 8 of 112 Revision 1 09/15/2020

2. Containment ISI Program Summary Description The Calvert Cliffs containment post-tensioning system examination program generally conforms to the guidance in USNRC Regulatory Guide 1.35 (Reference 4.5) or the requirements of 10CFR50.55a (Reference 4.6) and, as cited therein, ASME Section XI, Subsection IWL (Reference 4.7) as noted in the table below. The program incorporates the following examination activities.

Visual examination of the concrete exterior surface (as previously discussed, this activity will continue to be performed in accordance with past practice and, with the exception of specified enhancements, is not addressed further in this report).

Measurement of force applied by the surveillance sample tendons at the end anchorage.

Testing of wires, extracted from designated tendons, to determine ongoing tensile strength and ductility.

Visual examination of sample tendon end anchorage hardware and concrete surrounding the bearing plates to detect cracking, deformation, corrosion, missing button heads or broken wires, water intrusion into tendon ductwork and other indications of possible degradation.

Testing of corrosion protection medium (CPM) samples for the presence of corrosive ions (specifically, chloride, nitrate and sulfide) and absorbed water and, to verify continuing reserve alkalinity1.

Collecting free water found in end anchorage areas and testing of water samples to determine pH.

For each surveillance, a specified number of sample tendons is selected at random from the overall population. With the exception of one tendon in each group (hoop, vertical, dome) that is common2 to consecutive surveillances, a surveillance sample excludes tendons previously examined. Additional tendons may be designated for examination /

testing if unexpected conditions are or were found during the course of current or past surveillances.

Calvert Cliffs has completed 10 pre-stressing system surveillances on each unit. These were based on Regulatory Guide 1.35 or 10CFR50.55a / ASME Section XI Subsection IWL and included examinations and tests as shown below.

1 The CPM is formulated to neutralize strong acids that would otherwise have the potential to attack post-tensioning system hardware.

2 Common tendons were not designated prior to the 25th year surveillance.

Calvert Cliffs Technical Report Part B - Page 9 of 112 Revision 1 09/15/2020 Surveillance Record Calendar Year Examinations / Tests Examination Performed Performed Governing Year Lift-off / Wirea, b Visual / CPMc Document(s)

Unit 1 Unit 2 Unit 1 Unit 2 Unit 1 Unit 2 1 1975 1977 Yes Yes Yes Yes Reg Guide 1.35 3 1976 1979 Yes No Yes Yes Reg Guide 1.35 5 1978 1981 Yes No Yes Yes Reg Guide 1.35 10 1984 1985 Yes No Yes Yes Reg Guide 1.35 15 1991 1991 Yes No Yes Yes Reg Guide 1.35 20 1997 1997 Yes Note d Yes Yes Reg Guide 1.35 25 2002 2002 No Yes Yes Yes 10CFR50.55a / IWL 30 2008 2008 Yes No Yes Yes 10CFR50.55a / IWL 35 2012 2012 No Yes Yes Yes 10CFR50.55a / IWL 40 2016 2016 Yes No Yes Yes 10CFR50.55a / IWL Note a: Lift-off measurements alternate between units as addressed in IWL-2421.

Note b: Lift-off measures tendon force; wire tests include ultimate strength and elongation.

Note c: Visual examination of anchorage hardware / area concrete and CPM chemical analysis.

Note d: Vertical tendons only.

Continuing containment structural3 integrity is verified through regular examinations and tests (also referred to herein as surveillances) performed every 5 years in accordance with plant ISI Program Plans. These program plans incorporate the requirements of 10CFR50.55a and ASME Section XI, Subsection IWL.

The ISI program requires visual examination of the entire containment concrete surface and examination and testing of small samples (nominally 2% of the tendon group population) of hoop, vertical and dome tendons. Each sample includes tendons selected at random from the population and, starting with the 25th year surveillance, one tendon common to consecutive examinations. Additional tendons may be examined and tested to address unexpected conditions found during the course of a surveillance.

Tendon examinations and tests are currently performed in accordance with the requirements of Subsection IWL. Concrete surface visual examinations (with the exception of specified enhancements) are not covered in this report and follow the 3

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

Calvert Cliffs Technical Report Part B - Page 10 of 112 Revision 1 09/15/2020 applicable guidelines given in the American Concrete Institute (ACI) reports referenced in IWL.

Tendon examinations and tests consist of the activities described above.

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3. Summary of Proposed Program Changes, Visual Examination Program Enhancements and Conclusions

[Note: This report and the Relief Request that it supports address only proposed departures from the inservice inspection requirements covered by ASME Section XI, Subsection IWL Table IWL-2500-1 Examination Category L-B. Category L-A concrete examinations will continue to be performed in accordance with Subsection IWL requirements and enhancements described in 3.2 below. Also, containment liner and penetration assembly inservice inspection requirements specified in Subsection IWE will continue to be implemented in accordance with the current ISI plan.]

Proposed containment pre-stressing system examination program changes, containment visual examination program enhancements and associated conclusions are summarized in 3.1, 3.2 and 3.3 which follow.

3.1 Proposed Program Changes The following departures from current ISI requirements are proposed and evaluated in this report.

Extend the interval between post-tensioning system examinations and tests and detailed visual examination of concrete adjacent to tendon bearing plates from 5 years to 10 years.

Eliminate requirement for sample wire removal and testing and the associated need for tendon de-tensioning / re-tensioning.

Reduce the number of corrosion protection medium (CPM) chemical tests.

The above proposed departures relate only to pre-stressing system 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.

3.2 Visual Examination Program Enhancements Procedures for the Table IWL-2500-1 Examination Category L-A visual examinations that are performed every 5 years will be enhanced to ensure that unexpected post-tensioning system problems are identified in a timely manner. Enhancements will include the following.

General visual examination, as defined in IWL-2310(a), will cover tendon end caps, bearing plates and anchorage area concrete for evidence of damage / deformation,

Calvert Cliffs Technical Report Part B - Page 12 of 112 Revision 1 09/15/2020 corrosion, cracking and corrosion protection medium leakage. Examinations will be performed from roofs, floors, platforms, ladders and other means of achieving relatively close-in access to the anchorage area and with sufficient illumination to detect deleterious conditions. If close-in access is not possible, remote examination techniques (e.g., optical aids and drone mounted cameras) will be used.

Detailed visual examination, as defined in IWL-2310(b), will be performed at those areas identified during general visual as areas with conditions requiring close-in examination.

If an end anchorage area examination uncovers a condition indicative of possible damage to the enclosed post-tensioning system hardware or an anchor head failure, the end cap will be removed and the anchorage area examined by the Responsible Engineer4 (RE). Additional actions will be taken as specified by the RE.

If an end anchorage area examination uncovers active corrosion on a bearing plate or end cap, the condition will be evaluated by the RE. Additional actions will be taken as specified by the RE.

If an end anchorage area examination uncovers concrete cracks that are considered by the RE to have potential structural significance, a detailed examination of the condition will be performed and additional actions taken as specified by the RE.

Examinations will be performed to detect CPM leakage. Observed leakage will be evaluated by the RE who will determine if corrective action (e.g., end cap gasket replacement and duct refilling / top-off) is needed. If further action is required, the RE will prepare and initiate a corrective action plan.

The top shelf of the ring girder will be visually examined at a frequency specified by the RE. Indications of water ponding, bearing plate corrosion or end cap corrosion will be evaluated by the RE who will determine if further examination or corrective action is required. If further action is required, the RE will prepare and initiate a corrective action plan.

Buttress wells will be visually examined at a frequency specified by the RE.

Indications of water ponding, bearing plate corrosion or end cap corrosion will be evaluated by the RE who will determine if further examination or corrective action is required. If further action is required, the RE will prepare and initiate a corrective action plan.

4 The Responsible Engineer is an owner designated registered professional engineer qualified, as defined in accordance with IWL-2330, to prepare concrete containment examination programs, certify examination personnel, direct examinations and evaluate examination results.

Calvert Cliffs Technical Report Part B - Page 13 of 112 Revision 1 09/15/2020 3.3 Conclusions The evaluations addressed in Parts C and D of this technical report, support the conclusion that the proposed departures from the current requirements of Subsection IWL, as described in 3.1 above, when implemented with the recommended enhancements to visual examination program listed in 3.2 , will have no adverse impact on the safe operation of the plant.

In addition, it is concluded the proposed examination interval extension, elimination of wire testing and reduction of CPM tests will enhance personnel safety, reduce radiation exposure, limit potential degradation of containment structural integrity and reduce the risk of damage to plant equipment.

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4. Part B References 4.1 Baltimore Gas and Electric Company / Calvert Cliffs Nuclear Power Plant Units 1 and 2 / Final Safety Analysis Report, Chapter 5.

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

4.3 Prestressing Report / Containment Building / Baltimore Gas and Electric Company

/ Calvert Cliffs Power Plant Unit No. 1 / Job No. 6750, Prepared by Bechtel Power Corporation / Gaithersburg, Maryland, November, 1973.

4.4 Prestressing Report / Containment Building / Baltimore Gas and Electric Company

/ Calvert Cliffs Nuclear Power Plant Unit No. 2 / Job No. 6750, Prepared by Bechtel Power Corporation / Gaithersburg, Maryland, June, 1977.

4.5 USNRC Regulatory Guide 1.35, Inservice Inspection of Ungrouted Tendons in Prestressed Concrete Containments, Revisions 1, 2 & 3.

4.6 USNRC Regulation 10CFR50.55a, Codes and Standards.

4.7 ASME Boiler and Pressure Vessel Code,Section XI, Subsection IWL, 2013 Edition.

Calvert Cliffs Technical Report Part C - Page 15 of 112 Revision 1 09/15/2020 PART C - BACKGROUND OF CURRENT ISI REQUIREMENTS AND BASIS FOR PROPOSED PROGRAM CHANGES Containment inservice inspection (also referred to herein as surveillance and inservice examination) requirements originated with the issuance of Regulatory Guide 1.35 (Reference 5.1) in the early 1970s and are currently mandated by ASME Section XI, Subsection IWL (Reference 5.2), which is incorporated by reference into USNRC Regulation 10CFR50.55a (Reference 5.3). A brief history of current requirement development is summarized in Sections 1, 2 and 3 below. The basis for the proposed departure from the current requirement is discussed in Section 4.

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 at about the time that the first pre-stressed concrete containment structures were being placed into service and well before the accumulation of prototype containment pre-stressing system performance data, described the following as an acceptable basis for system examinations.

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

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

Wire extraction - one wire 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.

Physical tests - tendon liftoff force and extracted wire 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 (these probably represent consensus opinions reached, at the time, among the individuals involved in guide development). Also, it does not address the possible need for changes as future operating experience accumulated.

Subsequent revisions to Regulatory 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

Calvert Cliffs Technical Report Part C - Page 16 of 112 Revision 1 09/15/2020 the examination interval and wire testing program as described in the original 1973 issue.

The final revision, Revision 3, was issued in July 1990.

Neither the initial issue of the regulatory guide nor later revisions addressed the use of past performance5 as a basis increasing examination intervals or reducing specific examination and testing requirements.

As Regulatory Guide 1.35 was effectively rendered obsolete when ASME Section XI, Subsection IWL was incorporated, by reference, into 10CFR50.55a (see sections 2 and 3 below), it was finally withdrawn in August 2015.

5 Appendix J to 10CFR50, which addresses containment leakage rate testing, provides an example of performance-based examination / testing requirements.

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2. ASME Section XI / Subsection IWL The 1989 edition of the ASME Boiler and Pressure Vessel Code included in Section XI, for the first time, Subsection IWL which provided comprehensive and detailed requirements for a concrete containment inservice inspection program. During the development of IWL6, which commenced in the 1970s, it was concluded that NRC acceptance and endorsement (by reference in 10CFR50.55a) of the document would be expedited if departures from the program described in Regulatory Guide 1.35 were minimized. For this reason, the examination interval, strength / elongation testing of wire samples and relatively extensive chemical testing of corrosion protection medium samples mandated in IWL are unchanged from those identified in Regulatory Guide 1.35, Rev. 3.

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

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 Section XI in 1989.

Calvert Cliffs Technical Report Part C - Page 18 of 112 Revision 1 09/15/2020

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 IWL but none have addressed changes to either the examination interval or the requirements for testing wire and corrosion protection medium samples.

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4. Basis for Proposed Program Changes / Relief from 10CFR50.55a and IWL Requirements This section of the technical report includes a generalized summary of post-tensioning system performance observed during 4 decades of periodic examinations conducted at the 25 U. S. nuclear plant sites with 41 pre-stressed concrete containments7 listed in Table 1 (included in section 6 of this part). 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.

This summary8, intended to be qualitative, is based on the 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 using performance data documented for ~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 required 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.

As noted in Sections 1, 2 and 3 above, the examination intervals and wire testing addressed in the 1973 original issue of Regulatory Guide 1.35 are now, 47 years later, still incorporated effectively unchanged into the current edition of ASME Section XI, Subsection IWL.

7 Thirty two units at 18 plant sites are currently operating.

8 As the summary is qualitative, specific references are not cited as the bases for generalized statements regarding post-tensioning system performance.

Calvert Cliffs Technical Report Part C - Page 20 of 112 Revision 1 09/15/2020 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.

The results of unbonded post-tensioning system examinations performed over the last 4 decades at the 41 nuclear units with pre-stressed containments provide ample evidence, as discussed below, that prescriptive requirements currently in IWL are, in many cases, overly conservative and that an acceptable level of quality and safety can be maintained by performing Table IWL-2500-1 Examination Category L-B examinations at intervals greater than 5 years and by relaxing certain specific testing requirements.

Containment ISI programs should be based on individual plant performance and not bound by requirements that were established without the benefit of the accumulated operating experience available today.

The lessening of certain containment ISI requirements, as addressed in this report and the associated Relief Request that it supports, provides the following benefits.

It reduces personnel radiation exposure.

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 petroleum products under pressure and working in proximity to high energy plant systems.

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 general conclusions regarding post-tensioning system performance are listed below.

Conclusions specific to the Calvert Cliffs plant are addressed in detail in Part D.

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 commenced) 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

Calvert Cliffs Technical Report Part C - Page 21 of 112 Revision 1 09/15/2020 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 materials 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 flat9. Given this general trend, it can be stated with a high degree of confidence that the examination interval may be increased beyond 5 years with no compromise of safety function if the following conditions are satisfied.

The current mean pre-stressing force (hoop, vertical or dome), computed using both the trend of individual tendon force data acquired to date and the mean of the most recently acquired data, exceeds the minimum required level by significant margins.

The margin deemed significant is established through an evaluation by the Responsible Engineer. If the trend of the mean is considered to be a log-linear function, data acquired during the year 1, 3 and 5 examinations may be omitted from the trend computation10.

The forecast mean pre-stressing forces (hoop dome and vertical), 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 examination.

Common tendon force trend line slopes, adjusted up or down, as applicable, to current group mean force levels, indicate that group means will remain above required minima with acceptable margins through the deadline for completion of the subsequent examination.

9 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.

10 Industry wide data tend to show that mean force (vs. log time) decreases significantly more rapidly during the first 10 years following completion of pre-stressing operations than it does during subsequent years.

In addition, measurements made during the early years of plant life are often known to be less accurate than those made later using improved technology.

Calvert Cliffs Technical Report Part C - Page 22 of 112 Revision 1 09/15/2020 4.2 System Hardware Condition History There have been relatively few significant issues associated with post-tensioning system hardware (tendon wire / strand11, anchor heads, wedges, shims and bearing plates).

Active corrosion is typically found only on the parts of bearing plates exposed to outside atmospheric conditions.

Instances of deformation, damage and degradation are rare and almost always associated with singular construction events. Missing button heads are occasionally reported but affect only an inconsequential fraction of the total number of wires comprising the containment tendons.

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 other, anchor head material, are described below.

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

Ponding of water on the top shelf of the ring girder, possible end cap gasket damage and inadequate sealing of end cap hold down bolting resulted in storm water and snow intrusion into a number of vertical tendon upper end caps at both units of a two-unit plant. The upper ends of many vertical tendon wires were not completely coated with CPM and were severely corroded by exposure to the water. The problem was addressed by replacing vertical tendons with severely corroded wires, installing new leak-tight end caps, refilling vertical tendon ductwork with newer formulation CPM and improving ring girder drainage.

The condition has not recurred.

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 random times over the past 4 decades. Industry wide evaluations established that anchor heads of this type are not in use elsewhere.

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.

11 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, only the Vogtle units are currently operating.

Calvert Cliffs Technical Report Part C - Page 23 of 112 Revision 1 09/15/2020 4.3 Wire 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 significantly 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 requisite experience.

In general, tests that conform to ASTM specifications and that are performed by experienced technicians show that both strength and elongation are reasonably close to, but exceed, the minima (240 ksi and 4%, respectively) specified for ASTM A421 (Reference 5.4) 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 testing to measure 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.

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

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 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.

Calvert Cliffs Technical Report Part C - Page 24 of 112 Revision 1 09/15/2020 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 5.2) Table IWL-2525-1, to determine absorbed water content, corrosive ion concentration and residual reserve alkalinity.

Corrosive ions cannot enter the ductwork in the absence of water intrusion and reserve alkalinity cannot be brought into play if there are no acid ions present in the bulk CPM.

Therefore, there is little or no benefit gained by testing CPM samples for ion concentrations and reserve alkalinity unless there is evidence of free water in end caps or ducting or a significant quantity of absorbed water in CPM samples.

Consequently, industry experience would suggest that CPM samples collected during end anchorage examinations should be initially tested only to determine absorbed water content. Additional tests should be conducted only if there is evidence of free water12 in end caps / ducting or sufficient absorbed water in CPM samples 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).

12 Free water is always collected and tested to determine pH in accordance with the requirements of Subsection IWL.

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5. Part C References 5.1 USNRC Regulatory Guide 1.35, Inservice Inspection of Ungrouted Tendons in Prestressed Concrete Containments, Revisions 1, 2 & 3.

5.2 ASME Boiler and Pressure Vessel Code,Section XI, Subsection IWL, 1989 and later editions / addenda).

5.3 USNRC Regulation 10CFR50.55a, Codes and Standards.

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

Calvert Cliffs Technical Report Part C - Page 26 of 112 Revision 1 09/15/2020

6. Part C Tables Tables cited in Part C follow.

Calvert Cliffs Technical Report Part C - Page 27 of 112 Revision 1 09/15/2020 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 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 BWR Mark II (cylinder - cone) containment w / hoop & vertical tendon LaSalle 1 & 2 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.

Calvert Cliffs Technical Report Part D - Page 28 of 112 Revision 1 09/15/2020 PART D - CALVERT CLIFFS / PROPOSED ISI PROGRAM CHANGES

[Note: Much of the material in Part D is based on data taken from numerous completed surveillance procedures and surveillance reports. In many instances, data as well as the results of computations that incorporate the data are rounded to a consistent number of significant figures. When a value to be rounded ends in 5, it is rounded up or down to the nearest even number (an unbiased process).]

1. Summary of Proposed Program Changes, Current Program Enhancements, Vertical Tendon Repair / Replacement Program and Conclusions 1.1 Proposed Program Changes The following changes from current ISI requirements are proposed and evaluated in this report.

Extend the interval between post-tensioning system examinations and tests as well as detailed visual examination of concrete adjacent to tendon bearing plates from 5 years to 10 years.

Eliminate de-tensioning / re-tensioning of tendons, sample wire removal and sample wire testing except as specified by the Responsible Engineer.

Reduce the number of corrosion protection medium (CPM) chemical tests.

The above proposed departures relate only to pre-stressing system 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.

1.2 Visual Examination Program Enhancements Procedures for the Table IWL-2500-1 Examination Category L-A visual examinations that are performed every 5 years will be enhanced to ensure that unexpected post-tensioning system problems are identified in a timely manner. Enhancements will include the following.

General visual examination, as defined in IWL-2310(a), will cover all tendon end caps, bearing plates and anchorage area concrete for evidence of damage / deformation, corrosion, cracking and corrosion protection medium leakage. Examinations will be performed from roofs, floors, platforms, ladders and other means of achieving relatively close in access to the anchorage area and with sufficient illumination to

Calvert Cliffs Technical Report Part D - Page 29 of 112 Revision 1 09/15/2020 detect deleterious conditions. If close in access is not possible, remote examination techniques (e.g., optical aids and drone mounted cameras) will be used.

Detailed visual examination, as defined in IWL-2310(b), will be performed at those areas identified during general visual as areas with conditions requiring close in examination.

If an end anchorage area examination uncovers a condition indicative of possible damage to the enclosed post-tensioning system hardware or an anchor head failure, the end cap will be removed and the anchorage area examined by the Responsible Engineer (RE). Additional actions will be taken as specified by the RE.

If an end anchorage area examination uncovers active corrosion on a bearing plate or end cap, the condition will be evaluated by the RE. Additional actions will be taken as specified by the RE.

If an end anchorage area examination uncovers concrete cracks that are considered by the RE to have potential structural significance, a detailed examination of the condition will be performed and additional actions taken as specified by the RE.

Examinations will be performed to detect CPM leakage. Observed leakage will be evaluated by the RE who will determine if corrective action (e.g., end cap gasket replacement and duct refilling / top-off) is needed. If further action is required, the RE will prepare and initiate a corrective action plan.

In addition to the above, the following examinations will be performed at more frequent intervals, as specified by the RE, assess conditions in areas where severe corrosion has been observed during past surveillances.

The top shelf of the ring girder will be visually examined at least for indications of water ponding, bearing plate corrosion or end cap corrosion. Observed corrosion will be evaluated by the RE who will determine if further examination or corrective action is required. If further action is required, the RE will prepare and initiate a corrective action plan.

Buttress sumps will be visually examined for indications of flooding, bearing plate corrosion or end cap corrosion. Observed corrosion will be evaluated by the RE who will determine if further examination or corrective action is required. If further action is required, the RE will prepare and initiate a corrective action plan.

1.3 Vertical Tendon Repair / Replacement Program During the 20th year (Units 1 and 2) surveillance, which commenced in May 1997, major corrosion was found at the upper ends of many vertical tendon wires. The corrosion, attributed to a combination of factors, as discussed below, was extensive and resulted in

Calvert Cliffs Technical Report Part D - Page 30 of 112 Revision 1 09/15/2020 expanding the surveillance scope to include visual examination of all Unit 1 and Unit 2 vertical tendon anchorages as well as measurement of force in all vertical tendons.

Following the completion of this surveillance, about one third of the Unit 1 and Unit 2 tendons were either replaced or re-tensioned in 2002.

A detailed evaluation of the condition and description of proposed corrective measures are included in ESP No. ES199800135 (Reference 8.4). These are summarized in the following paragraphs.

1.3.1 Cause of Condition Wire corrosion is postulated to have resulted from water intrusion into the upper anchorage end caps which were prone to in-leakage through the hold-down stud holes as well as through breaches in the gaskets.

Following tensioning of the vertical tendons in the early 1970s, corrosion protection medium (CPM) was pumped into the tendon gallery end caps and through the vertical duct work. The vent opening at the upper ends of many tendons was close to the bearing plate rather than the anchor head, resulting in void of several inches below the head. This left the upper ends of these tendons without a coating of CPM and, as a consequence, vulnerable to corrosion.

As no significant degree of corrosion was found during the 15th year and earlier surveillances, it is presumed that most of the corrosion found in 1997 occurred after the 1991 completion of the 15th year surveillance.

1.3.1 Extent of Condition and Repair Corrosion found on the wires of 47 Unit 1 tendons and 46 Unit 2 tendons was considered sufficiently severe to dictate replacement. These tendons, listed in Tables 1a & 1b, were replaced in a specified sequence. The cited tables also list the as-found lift-off force measured during the 20th year surveillance and the as-left lock-off force in the replaced tendons.

In addition, 20 Unit 1 and 30 Unit 2 tendons were re-tensioned (but not replaced) to a force greater than the as-found. These tendons, with as-found lift-off force (measured during the 20th year surveillance) and as-left lock-off force, are also listed in Tables 1a &

1b.

The repair / replacement program included improving ring girder top shelf drainage, replacing all vertical tendon end caps with a leak tight design, purging the original CPM

Calvert Cliffs Technical Report Part D - Page 31 of 112 Revision 1 09/15/2020 from the ductwork and injecting new CPM13 into each tendon to ensure complete fill.

These actions have effectively eliminated vertical tendon water intrusion and corrosion as discussed in Sections 3 and 4 below. In addition, replacing the bottom end caps has effectively eliminated leakage of CPM from vertical tendons.

1.3.2 Effect of Increasing Vertical Pre-Stressing Force The as-left lock-off forces in replaced and re-tensioned tendons were significantly greater than the as-found lift-off forces measured during the 20th year surveillance in 1997. The as-found and as-left forces and summations are listed in Tables 1a (Unit 1) and 1b (Unit 2). The resulting elastic shortening of the cylinder wall reduced force in the remaining vertical tendons which has an effect on computed trends and trend forecasting. The magnitude of this reduction and its impact on vertical tendon force trending are computed

/ evaluated in subsequent paragraphs.

The summations shown in Tables 1a and 1b are listed, with net changes, below.

Replaced / Re-Tensioned Tendon Force Summation / Net Change Unit As-Found, kip As-Left, kip Net Change, kip 1 39,742 50,122 10,380 2 47,623 56,584 8,961 The containment wall (both units) has an outside diameter of 137.5 ft and an inside diameter of 130.0 ft as shown in Part B, Section 1. Plan area of the wall (with buttress area neglected) is ( / 4) * (137.52 - 130.02) = 1,575.7 ft2. The increase in concrete compressive stress, , resulting from the higher as-left tendon forces is:

Unit 1 - 1 = 10,380 / 1,575.7 = 6.588 kip / ft2 = 0.046 kip / in2 Unit 2 - 2 = 8,961 / 1,575.7 = 5.687 kip / ft2 = 0.039 kip / in2 Force in those tendons that were not replaced / re-tensioned decreased as a result of this increase in concrete compressive stress and consequent elastic shortening of the wall.

The decrease in force, F, in each of these tendons is reasonably approximated by the following expression that treats wall height and tendon length as the same (i.e., effects of the stiffer ring girder and base mat are neglected).

F = 4.42

• 29,000 / 4,000 * = 32.0

• where 4.42 in2 is tendon area (90 - 1/4 inch diameter wires) 13 The original Visconorust 2090P CPM was replaced with a later formulation, 2090P-4, that provides improved corrosion protection and has a higher melting point, making it less prone to leakage.

Calvert Cliffs Technical Report Part D - Page 32 of 112 Revision 1 09/15/2020 29,000 ksi is tendon steel modulus of elasticity 4,000 ksi is concrete modulus of elasticity (postulated value)

The loss in force (elastic shortening loss) in those Unit 1 and Unit 2 tendons that were not replaced / re-tensioned is:

F1 (Unit 1) = 0.046

• 32.0 = 1.5 kip F2 (Unit 2) = 0.039

• 32.0 = 1.2 kip The above losses are quite small relative to the nominal 600+ kip force remaining in those tendons and will have a negligible impact on vertical tendon force trend construction and forecasting. Therefore, these small losses are neglected in subsequent computations.

1.4 Conclusions The evaluations addressed in Sections 2 through 5 below, with the visual examination program enhancements discussed in 1.2, support the conclusion that the proposed departures from the current requirements of Subsection IWL, as described in 1.1, can be implemented with no adverse impact on the safe operation of the plant.

In addition, it is concluded the proposed examination interval extension, elimination of wire testing and reduction of CPM tests will enhance personnel safety, reduce radiation exposure, limit potential degradation of containment structural integrity and reduce the risk of damage to plant equipment.

Sections 2 through 5 provide a comprehensive evaluation of Calvert Cliffs post-tensioning system examination results as documented in completed surveillance procedures and reports (References 8.5 through 8.23). These address the following aspects of examination results.

Section 2 - Tendon Force Trends and Forecasts14 2.1 - Hoop Tendon Force Trends and Forecasts 2.2 - Vertical Tendon Force Trends and Forecasts 2.3 - Dome Tendon Force Trends and Forecasts 2.4 - Tendon Mean Force Trend Summary and Conclusions 2.5 - Replaced / Re-tensioned Vertical Tendon Force Trends 14 As discussed in Section 2, the Calvert Cliffs containment inservice inspection program conformed to an early revision of Regulatory Guide 1.35 through the 20th year surveillance, which was performed between May 1997 and January 1998. In conformance with the 1.35 guidelines, the program required only visual examination of the Unit 2 post-tensioning system and did not require measurement of tendon force.

Calvert Cliffs Technical Report Part D - Page 33 of 112 Revision 1 09/15/2020 Section 3 - Wire Examination and Test Results Evaluation 3.1 - Wire Visual Examination and Condition 3.2 - Wire Tensile Strength 3.3 - Wire Elongation at Failure 3.4 - Wire Visual Examination and Test Summary Section 4 - End Anchorage Hardware / Concrete Condition 4.1 - Corrosion 4.2 - Free Water 4.3 - Missing / Discontinuous Wires 4.4 - Load Bearing Component Damage / Distortion 4.5 - Concrete Cracking Adjacent to Bearing Plates 4.6 - End Anchorage Condition Summary and Conclusions Section 5 - Corrosion Protection Medium Testing 5.1 - Corrosive Ion Concentrations 5.2 - Reserve Alkalinity / Neutralization Number 5.3 - Absorbed Water Content 5.4 - CPM Test Summary and Conclusion The proposed extension of the tendon surveillance interval to 10 years is justified if it can be shown with a high degree of confidence that the post-tensioning system with its several components will continue to perform its intended function and meet examination acceptance criteria until well beyond the deadline for completion of the next surveillance if the interval is extended to 10 years.

In addition, the proposed elimination of wire testing and reduction in the number of tests on each CPM sample is justified if it can be can be shown with a high degree of confidence that wire and CPM characteristics are effectively stable over time.

Justification for the above proposed program changes from Subsection IWL requirements is demonstrated by the evaluations and analyses presented below.

Calvert Cliffs Technical Report Part D - Page 34 of 112 Revision 1 09/15/2020

2. Tendon Force Trends and Forecasts

[Note: Surveillance documentation addresses both measured and normalized (to account for differences in initial tendon seating force and elastic shortening losses) tendon lift-off force. Normalizing may be justified if examination samples are small and there is a significant potential for bias in the mean force computed for each of the tendon groups (hoop, vertical and dome). The following computations use large data samples (lift-off forces recorded during surveillances completed to date) which are only minimally affected by the bias that results from differences between sample and population means and, therefore, are based only on measured lift-of forces.]

As previously noted, the Calvert Cliffs containment inservice inspection program in force before 2001 required only visual examination of the Unit 2 post-tensioning system in accordance with the guidance provided in the early (prior to the July 1990 issue of Revision 3) revisions of Regulatory Guide 1.35. The requirement to measure Unit 2 tendon forces, as specified by ASME Section XI, Subsection IWL, was implemented starting with the 25th year surveillance, performed in late 2002 and early 2003.

While there was no requirement to measure Unit 2 tendon forces prior to 2002, these were measured during the 1st year surveillance (1977) after certain Unit 1 3rd year surveillance tendon forces were found to have fallen below prediction limits. Forces in Unit 2 tendons, other than verticals as discussed 1.3 above, were not measured again until the 25th year.

The material presented in 2.1 through 2.3 below incorporates a number of parameters, defined where first used, derived from the surveillance data shown in Tables 4 through 9.

These parameters are listed, for reference, in Table 2.

The time parameter, T, shown in Tables 4 - 9, is years (rounded to the nearest tenth) from the applicable unit structural integrity test (SIT) to the mid-point of a surveillance.

Surveillance mid-point is the date mid-way between the starting and ending dates noted in each of the surveillance reports or, for the early surveillances, the dates of the first and last recorded examination. For starting and ending dates noted only by month, T is computed by treating the surveillance as extending from the beginning of the initial month through the end of the final month. Applicable dates and computed values of T are shown in Tables 3a and 3b.

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, were measured during unit examinations. The purpose of a lift-off force measurement is to determine how the initial seating force in a tendon (used as a measure of the pre-stressing force contributed by the tendon) has been reduced by elastic shortening and time dependent losses. Reported tendon force is the

Calvert Cliffs Technical Report Part D - Page 35 of 112 Revision 1 09/15/2020 single lift-off force measured at the upper end of a vertical tendon15 or the average of the lift-off forces measured at the two anchorages of a hoop or dome 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, vertical or dome).

The Unit 1 and Unit 2 measured force trends and forecasts provide ample evidence that mean pre-stressing in the containment wall and dome will remain above the lower limits shown in design calculation CA06062 (Reference 8.24) until well after the deadline for completion of the next surveillance if the interval is extended to 10 years.

Lift-off forces measured at Calvert Cliffs, exhibit more scatter16 than those measured at the newer plants that have been the subject of recent prestressing force trend analyses.

Reasons for this are not well understood but may be related to tendon size among other factors. Calvert utilizes tendons with 90 wires and a cross-sectional area of 4.42 in2. The other plants recently evaluated for examination interval extension utilize tendons with 170 wires or 55 strands, both of which have cross-sectional areas over 8 in2.

Because of this data scatter, which is well illustrated in Figure 1, trends based on the results of the 10th year and later surveillances (which normally provide a more realistic trends) do not provide a good basis for prestressing force trend analysis and forecasting.

Figure 2 shows Unit 1 hoop tendon forces and the associated log-linear trend using data acquired in the 10th through 40th year surveillances. The calculated trend is positive (mean force increasing slowly with time) which is not realistic. The positive trend is attributed to data scatter.

Given the impact of scatter, it was decided to base the forecasts of mean pre-stressing force on trends and lower confidence limits (LCLs) that incorporate the results of all surveillances from the 1st year on. This approach is conservative in that it factors the more rapid early prestressing losses into an overall log-linear trend.

Also, as the early surveillances were based on guidance provided in Regulatory Guide 1.35 Revisions 1 and 2, common tendons were not designated until the 25th year surveillance which was performed in late 2002 and early 2003. As a consequence, there are insufficient common tendon data points to allow establishing meaningful trends. For this reason, alternative prestressing force forecasts using computed common tendon trend line slopes are not developed in this report.

15 Several vertical tendons that deviate around penetrations were tensioned at both ends; force at the bottom anchorage of these tendons was not measured during surveillances.

16 Scatter is the result of variations in initial seating force and elastic shortening loss as well as factors such as anchorage temperature (affects the thickness of the shim stack which has a direct bearing on the force in the short length of tendon between the anchor head and inflection point) that are generally not quantified. Normalization, discussed in the section 2 introductory note, should, in theory, significantly reduce scatter. In practice it does not consistently do so and, in some cases, results in greater scatter.

Calvert Cliffs Technical Report Part D - Page 36 of 112 Revision 1 09/15/2020 The use of a log-linear function to show prestressing force trends is consistent with the way creep, shrinkage and relaxation test results are presented as well as the material models that represent concrete and steel with an assemblage of linear springs and dash pots. Concrete creep strain, concrete shrinkage strain and pre-stressing steel stress relaxation are shown by relatively short-term tests17 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.

Postulating that true pre-stressing force follows a log-linear trend results in the trend lines shown representing, in the statistical sense, the expected relationship between true mean force and the logarithm of time. The actual relationship will differ from the statistically expected relationship, with the degree of difference accounted for, again in the statistical sense, by confidence limits.

This report uses the 95%18 lower confidence limit as a reasonable lower limit on mean force at any point in time and considers a forecast force to meet the acceptance criterion if the LCL exceeds the minimum required pre-stressing force specified for the tendon group (the minimum force line is plotted on the figures).

As shown on the Figures 1 - 7 plots, hoop, vertical and dome pre-stressing force trends and LCLs remain above group minimum required mean force levels beyond T = 100 (100 years following the applicable unit SIT) and well beyond the presumed 80-year upper limit on operating lifetime of each unit. Therefore, the following mean force trend and LCL evaluations are conservatively related to conditions at T = 100.

The trend line parameters and LCL values shown on the above cited figures and discussed in the subsequent paragraphs are computed using the methods developed in Reference 8.25.

Hoop, vertical and dome force trends are addressed separately in sub-sections 2.1 through 2.3 below (with replaced / re-tensioned tendons covered in 2.5).

17 Creep and shrinkage tests are typically conducted for 180 days 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 even 80 years if a second license extension is granted).

18 Containment integrated leakage rate, a safety related parameter, is calculated at the 95% (upper) confidence limit in accordance with the requirements of industry standards cited by reference in 10CFR50, Appendix J. This provides the basis for computing other safety related parameters at the 95%

confidence level.

Calvert Cliffs Technical Report Part D - Page 37 of 112 Revision 1 09/15/2020 2.1 Hoop Tendon Force Trends and Forecasts Unit 1 and Unit 2 hoop tendon force trends and forecasts are evaluated in 2.1.1 through 2.1.3.

2.1.1 Unit 1 Hoop Tendon Mean Force Trend Unit 1 hoop tendon forces measured during surveillances performed to date are listed in Table 4 and plotted in Figure 1. The plot includes the log-linear trend line fitted to the data points using the method of least squares. In addition, it shows the 95% lower confidence limit curve and a line representing the 536 kip minimum required hoop prestressing force.

While there is a considerable degree of data scatter, the plot does show that the overall trend is relatively flat and, that the mean of the forces measured during any given surveillance is well above the 536 kip minimum19. The log-linear trend line, defined by the equation FH (kip) = 644.4 - 20.0 Log10 (T), crosses the T = 100 years ordinate at 604 kips, or, 68 kips above the minimum. The LCL crosses at just over 590 kips, again well above the 536 kip minimum.

Figure 2 is a plot showing the lift-off forces measured during the 10th year and subsequent surveillances and includes the fitted log-linear trend line. The calculated trend is positive (force increasing with time) with a slope of 60.2 kips per unit logarithmic interval. The computed trend is not realistic; the calculated slope is ascribed to data scatter. Since the computed trend is not subject to any meaningful analysis, it is concluded that the Unit 1 hoop prestressing trend forecast should be based (conservatively as noted above) on the results of all 10 surveillances.

2.1.2 Unit 2 Hoop Tendon Mean Force Trend Unit 2 hoop tendon forces measured during surveillances performed to date are listed in Table 5 and plotted in Figure 3 (as previously discussed, Unit 2 hoop tendon forces were measured only during the 1st, 25th and 35th year surveillances). The figure also includes the log-linear trend line, the 95% LCL curve and the 536 kip minimum required mean hoop prestressing force line.

The Unit 2 data exhibit considerably less scatter than the data shown for Unit 1. However, as there are only 2 sets of surveillance results following the 1st year, it is impractical to attempt a trend analysis without using the 1st year data.

19 The minimum required mean pre-stressing force line represents the lower limit on the group mean. It does not represent a lower limit on individual measured lift-off force. There is no significance attached to individual lift-off forces that fall below the group mean lower limit.

Calvert Cliffs Technical Report Part D - Page 38 of 112 Revision 1 09/15/2020 The plot provides convincing evidence that the Unit 2 hoop prestressing force trend is relatively flat and that it will remain well over the 536 kip minimum beyond T = 100 years.

Using all of the data shown (again considered to be a conservative approach) yields a trend line, represented by the expression FH (kip) = 636.8 - 8.4 Log10 (T), and LCL curve that cross the T = 100 years ordinate line at 620 and 610 kips, respectively. The LCL, the controlling value, is 74 kips above the minimum at T = 100.

2.1.3 Hoop Tendon Force Evaluation Summary and Conclusions Unit 1 and Unit 2 hoop tendon lift-off forces are used to develop log-linear trends and 95%

lower confidence limits on trend ordinates. Values of hoop tendon mean force at T = 100 years computed for each trend and the LCL on the trended force are tabulated below.

Mean force, kip, @ T = 100 Trend or LCL Unit 1 Unit 2 Log-linear trend ordinate 604 620 95% LCL on trend ordinate 590 610 It is concluded, based on the statistical analyses and other evaluations discussed in the preceding paragraphs, that Unit 1 and Unit 2 hoop tendon mean force will, with a high degree of probability, remain above the 536 kip minimum past T = 100 years and well past the 80 year presumed upper limit on the operating lifetime of the units.

The foregoing analyses and evaluations of hoop tendon force trends, and the conclusions derived therefrom, support the proposed extension of the interval between containment post-tensioning system examinations to 10 years from the current 5 years.

2.2 Vertical Tendon Force Trends and Forecasts Unit 1 and Unit 2 vertical tendon trends and forecasts are evaluated in 2.2.1 through 2.2.3 below.

2.2.1 Unit 1 Vertical Tendon Mean Force Trend Unit 1 vertical tendon forces measured during surveillances performed to date are listed in Table 620 and plotted in Figure 4. The plot includes the log-linear trend line fitted to the data points, the 95% LCL and a line representing the 622 kip minimum required vertical prestressing force.

20 As previously noted, the as-found lift-off force in all vertical tendons was measured during the 20th year surveillance. The forces listed in Table 6 (and plotted in Figure 3) are those in the originally designated sample of 5 tendons.

Calvert Cliffs Technical Report Part D - Page 39 of 112 Revision 1 09/15/2020 While there is a considerable degree of data scatter, the plot does show that the overall trend is relatively flat and, that the mean of the forces measured during any given surveillance is well above the 622 kip minimum. The log-linear trend line, defined by the equation FV (kip) = 703.0 - 12.0 Log10 (T), crosses the T = 100 years ordinate at 679 kips or, 57 kips above the minimum. The LCL which is considered to be controlling, crosses 649 kips, 27 kips above the minimum.

The mean force calculated for the time (T = 23.8 years since the Unit 1 SIT) of the 20th year surveillance using the trend lined equation is 686.5 kips. The mean as-found force determined for all Unit 1 vertical tendons as shown in Reference 8.17 is 686 kips. The close correspondence between these two values suggests that the computed Unit 1 trend line is close to the true trend of mean vertical prestressing force.

2.2.2 Unit 2 Vertical Tendon Mean Force Trend Unit 2 vertical tendon forces measured during surveillances performed to date are listed in Table 721 and plotted in Figure 5. The figure also includes the log-linear trend line, the 95% LCL curve and the 622 kip minimum required mean prestressing force line.

As is case for hoop tendons, the Unit 2 data generally exhibit less scatter than the data shown for Unit 1.

The plot provides convincing evidence that the Unit 2 vertical prestressing force trend is relatively flat and that it will remain above the 622 kip minimum beyond T = 100 years.

Using all of the data shown (again considered to be a conservative approach) yields a trend line, represented by the expression FV (kip) = 679.2 - 9.6 Log10 (T), and LCL curve that cross the T = 100 years ordinate line at 660 and 639 kips, respectively. The LCL, considered to be controlling, is 17 kips above the minimum at T = 100 years.

The mean force calculated for the time (T = 21.5 years since the Unit 2 SIT) of the 20th year surveillance using the trend lined equation is 666.4 kips. The mean as-found force determined for all Unit 2 vertical tendons as shown in Reference 8.18 is 664 kips. The close correspondence between these two values suggests that the computed Unit 2 trend line is close to the true trend of mean vertical prestressing force.

21 As previously noted, the as-found lift-off force in all vertical tendons was measured during the 20th year surveillance. The forces listed in Table 7 (and plotted in Figure 5) are those in the originally designated visual examination sample of 9 tendons.

Calvert Cliffs Technical Report Part D - Page 40 of 112 Revision 1 09/15/2020 2.2.3 Vertical Tendon Force Evaluation Summary and Conclusions Unit 1 and Unit 2 vertical tendon lift-off forces are used to develop log-linear trends and 95% lower confidence limits on trend ordinates. Values of vertical tendon mean force at T = 100 years computed for each trend and the LCL on the trended force are tabulated below.

Mean force, kip, @ T = 100 Trend or LCL Unit 1 Unit 2 Log-linear trend ordinate 679 660 95% LCL on trend ordinate 649 639 It is concluded, based on the statistical analyses and other evaluations discussed in the preceding paragraphs, that Unit 1 and Unit 2 vertical tendon mean force will, with a high degree of probability, remain above the 622 kip minimum beyond T = 100 years and well past the 80 year presumed upper limit on the operating lifetime of the units.

The foregoing analyses and evaluations of vertical tendon force trends, and the conclusions derived therefrom, support the proposed extension of the interval between containment post-tensioning system examinations to 10 years from the current 5 years.

2.3 Dome Tendon Force Trends and Forecasts Dome tendon trends and forecasts are evaluated in 2.3.1 through 2.3.3 below.

2.3.1 Unit 1 Dome Tendon Mean Force Trend Unit 1 dome tendon forces measured during surveillances performed to date are listed in Table 8 and plotted in Figure 6. The plot includes the log-linear trend line, the 95% LCL curve and a line representing the 555 kip minimum required dome prestressing force.

The plotted data exhibit considerably less scatter than that shown for the Unit 1 hoop and vertical tendon forces in Figures 1 and 4. The overall trend is relatively flat and the mean of the forces measured during any given surveillance is well above the 555 kip minimum.

The log-linear trend line, defined by the equation FD (kip) = 662.2 - 16.3 Log10 (T), crosses the T = 100 year ordinate at 630 kips, or, 75 kips above the minimum. The LCL, considered to be controlling, crosses at 619 kips, also well above the 555 kip minimum.

Calvert Cliffs Technical Report Part D - Page 41 of 112 Revision 1 09/15/2020 2.3.2 Unit 2 Dome Tendon Mean Force Trend Unit 2 dome tendon forces measured during surveillances performed to date are listed in Table 9 and plotted in Figure 7. The figure also includes the log-linear trend line, the 95%

LCL curve and the 555 kip minimum required mean prestressing force line.

The Unit 2 dome tendon data, like the Unit 1 data, exhibits relatively little scatter.

The plot provides convincing evidence that Unit 2 dome prestressing force trend is relatively flat and that it will remain above the 555 kip minimum beyond T = 100 years.

Using all of the data shown (again considered to be a conservative approach) yields a trend line, represented by the expression FD (kip) = 657.8 - 3.3 Log10 (T), and LCL curve that cross the T = 100 years ordinate line at 651 and 640 kips, respectively. The LCL, considered to be controlling, is 85 kips above the minimum at T = 100.

2.3.3 Dome Tendon Force Evaluation Summary and Conclusions Unit 1 and Unit 2 dome tendon lift-off forces are used to develop log-linear trends and 95% lower confidence limits on trend ordinates. Values of dome tendon mean force at T

= 100 years computed for each trend and the LCL on the trended force are tabulated below.

Mean force, kip, @ T = 100 Trend or LCL Unit 1 Unit 2 Log-linear trend ordinate 630 651 95% LCL on trend ordinate 619 640 It is concluded, based on the statistical analyses and other evaluations discussed in the preceding paragraphs, that Unit 1 and Unit 2 dome tendon mean force will, with a high degree of probability, remain above the 555 kip minimum beyond T = 100 years and well past the 80 year presumed upper limit on the operating lifetime of the units.

The foregoing analyses and evaluations of dome tendon force trends, and the conclusions derived therefrom, support the proposed extension of the interval between containment post-tensioning system examinations to 10 years from the current 5 years.

2.4 Tendon Mean Force Trend Summary and Conclusions The trend of mean force is analyzed separately for the hoop, vertical and dome tendon groups. The analyses cover the results of the following computations, all based on the postulate that mean force varies linearly with the logarithm of time.

Calvert Cliffs Technical Report Part D - Page 42 of 112 Revision 1 09/15/2020 Log-linear trend based of measured forces recorded during all surveillances completed to date.

95% lower confidence limit (LCL) on the trend of measured forces.

The margins between the forecast group mean force / LCL and the group lower limit (minimum required mean prestressing force) are summarized in the table below. Margins are shown for T = 100 years which is well past the presumed maximum unit operating lifetime of 80 years.

Margins between Forecast and Minimum Required Mean Forces @ T = 100 Group / Forecast Minimum, Margin, Forecast Basis Unit Force, kip kip kip Hoop / Log-linear trend 604 68 Unit 1 95% LCL on trended mean 590 54 536 Hoop / Log-linear trend 620 84 Unit 2 95% LCL on trended mean 610 74 Vertical / Log-linear trend 679 57 Unit 1 95% LCL on trended mean 649 27 622 Vertical / Log-linear trend 660 38 Unit 2 95% LCL on trended mean 639 17 Dome / Log-linear trend 630 75 Unit 1 95% LCL on trended mean 619 64 555 Dome / Log-linear trend 651 96 Unit 2 95% LCL on trended mean 640 85 All of the above margins, which range from a minimum of 17 kips to 96 kips, are positive at T = 100 years. This provides a strong measure of assurance that mean pre-stressing forces provided by the hoop, vertical and dome tendon groups will remain above the minimum required levels well past the presumed 80-year maximum unit operating lifetime.

The above margin summary fully supports the proposed extension of the Calvert Cliffs post-tensioning system examination interval from 5 years to 10 years with tendon force measurements (ASME Section XI Table IWL-2500-1, Examination Category L-B, Item L2.10) alternating between Unit 1 and Unit 2 as shown in Section 1.1 above.

2.5 Replaced / Re-tensioned Vertical Tendon Force Trends As discussed in 1.3 above, a number of Unit 1 and Unit 2 vertical tendons were replaced or re-tensioned in 2002. This work was completed just prior to the 25th year surveillance.

Calvert Cliffs Technical Report Part D - Page 43 of 112 Revision 1 09/15/2020 Individual replaced and re-tensioned tendons are identified in Tables 1a and 1b.

Quantities of each are listed below.

Unit 1 Unit 2 Number Replaced 47 46 Number Re-Tensioned 20 30 Total Replaced / Re-Tensioned 67 76 ASME Section XI, Subsection IWL paragraph IWL-2521.2 treats the replacement and re-tensioning as a Repair / Replacement (R & R) activity and specifies that a separate sample of these tendons be examined during surveillances subsequent to the completion of the work. The replaced and re-tensioned tendon lock-off forces are significantly higher than the as found lift-off forces (see Tables 1a & 1b) and are, therefore, addressed separately when evaluating trends and UCLs.

Samples of Unit 1 R & R tendons were examined during the 30th, 35th and 40th year surveillances. Lift-off forces measured during these surveillances, 2002 lock-off forces and force loss since lock-off are tabulated below. The time parameter, T, is computed using a replacement / re-tensioning date of 01 July 2002 and surveillance mid-point dates as shown in Tables 3a & 3b.

Surveillance T, Years Since 2002 Lock-Off FM, Measured Loss, Tendon Year Re-Tensioning Force Force, kip kip 12V13 750 741 9 34V25 771 745 26 30 5.9 56V09 743 739 4 61V26 761 736 25 Mean Loss Since 2002 Lock-Off 16 12V07 755 739 16 34V13 738 741 -3 35 10.3 34V16 748 736 12 Mean Loss Since 2002 Lock-Off 8 45V10 748 735 13 40 14.2 56V32 749 732 17 Mean Loss Since 2002 Lock-Off 15 The mean loss shows no trend with time.

Samples of Unit 2 R & R tendons were examined during the 35th and 40th year surveillances. Lift-off forces measured during these surveillances, 2002 lock-off forces and force loss since lock-off are tabulated below. The time parameter, T, is the same as shown above for Unit 1.

Calvert Cliffs Technical Report Part D - Page 44 of 112 Revision 1 09/15/2020 Surveillance T, Years Since 2002 Lock-Off FM, Measured Loss, Tendon Year Re-Tensioning Force Force, kip kip 34V03 753 741 12 45V10 734 710 24 35 10.3 45V16 734 718 16 56V33 749 769 -20 Mean Loss Since 2002 Lock-Off 8 34V25 756 735 21 40 14.2 56V03 760 755 5 Mean Loss Since 2002 Lock-Off 13 Two mean loss data points are insufficient to define a meaningful trend. However, the mean losses at surveillance years 35 (8 kip) and 40 (15 kip & 13 kip) are effectively the same for both units.

While there is an insufficient number of data points to define individual unit trends or even a combined trend, measured forces in the replaced / re-tensioned vertical tendons are all above 700 kip and well above the minimum required vertical pre-stressing force of 622 kip. Also, current (as of the 40th year surveillance in 2016) R & R sample tendon forces are all well above the trend means shown on Figures 4 and 5 for the non-R & R tendons.

Evaluation the above aspects support the conclusion that the pre-stressing provided by the replaced and re-tensioned vertical tendons will exceed the 622 kip minimum by a wide margin throughout the operating lifetimes of the units.

Therefore, it is concluded that the R & R tendon surveillance results as discussed above support extension of the containment post-tensioning system ISI interval from the current 5 years to 10 years in accordance with the examination schedule proposed in 1.1.

Calvert Cliffs Technical Report Part D - Page 45 of 112 Revision 1 09/15/2020

3. Wire Examination and Test Results Evaluation During each surveillance in which Unit 1 or Unit 2 tendon lift-off forces were measured, sample wires were extracted from one designated tendon in each group, visually examined for damage / corrosion and tested to determine ultimate tensile strength (UTS) and elongation at failure. In addition, broken wires were extracted from the same or different tendons to assess the cause of breakage. Also, wires were extracted from replaced vertical tendons during the 30th, 35th and 40th year surveillances. Reported UTS values are shown in Tables 11a (Unit 1) and 11b (Unit 2); elongations at failure are shown in Tables 12a and 12b.

Tests were typically performed on three specimens cut from each of the wires. Two of the specimens were located close to the sample wire ends. A third specimen was cut at a location near the center of the wire. As show in the cited tables, 1 or 2 more specimens from a given wire were tested. This was done to assess the effect of observed corrosion or determine the extent of low strength / elongation regions (Unit 1 tendon 42H52).

3.1 Wire Visual Examination and Condition The entire length of each extracted wire was visually examined for signs of damage and corrosion. The corrosion condition of most extracted wires was judged to be Level 1 (A) or 2 (B); these corrosion levels are defined in the table below. There is no indication in any of the surveillance reports that observed corrosion was active22.

Levela Characteristicb 1 or A Bright metal 2 or B Light rust with no pitting 3 or C Rust with pitting up to 0.003 in depth 4 or D Rust with pitting 0.003 to 0.006 in depth 5 or E Rust with pitting greater than 0.006 in depth Note a: The alphabetic designations are shown for information only; these are not used in Calvert Cliffs reports.

Note b: While the above corrosion characteristic definitions are typical, these are not the same in all surveillance reports. Variations across reports are, however, relatively minor.

22 Many vertical tendon wires that were not initially designated for extraction / testing were found to be severely corroded during the 20th year surveillance. Much of this corrosion was active. This is addressed in subsection 1.3 above.

Calvert Cliffs Technical Report Part D - Page 46 of 112 Revision 1 09/15/2020 Level 3 and higher corrosion was found on 5 of the 48 wires extracted from designated sample tendons during surveillances completed to date. Surveillance year, unit, tendon and condition are noted below.

Surveillance Unit Tendon Condition Year Level 3 corrosion reported over a 4 ft length near one end (end 1 2 62H64 not noted) of the extracted wire.

Pitting (corrosion level not specified) over a 31 ft length near 1 2 56V13 one end (end not noted) of the extracted wire.

Level 4 corrosion at one end (end and extent not noted) 3 1 51H62 reported for the extracted wire.

Level 3 corrosion (extent not noted) reported at the upper end 10 1 45V25 of the extracted wire; corrosion ascribed to water infiltration. No indication that the corrosion was active at the time found.

Level 3 corrosion (location and extent not noted in the 40 1 3D03 contractor summary report) reported for the extracted wire; NCR FN1123-004.

Only one instance of Level 3 (and nothing greater than Level 3) corrosion has been reported since the Unit 1 10th year surveillance which was performed in late 1984.

Therefore, it is concluded that tendon wire corrosion is not a significant issue (see further discussion in subsection 4.1 below).

3.2 Wire Tensile Strength Tables 11a (Unit 1) and 11b (Unit 2) list the ultimate tensile strength (UTS) found for the test specimens cut from each extracted wire, the mean of the 3, 4 or 5 UTS values listed for each wire (Wire Mean) and the mean of all UTS values listed for the examination year (Exam Mean).

With the exceptions discussed below, the tensile strength of all specimens exceeds the 240 ksi minimum specified in ASTM A421 (Reference 8.26).

The Unit 1 table lists 238 ksi as the UTS for Specimen 4 cut from the 51H62 wire extracted during the 3rd year surveillance. This specimen was cut from the region of the wire with reported Level 4 corrosion. It is concluded, without the benefit of a metallurgical evaluation, that corrosion is the proximate cause of the low UTS.

Four specimens cut from Unit 1 tendon 42H52 wires during the 10th year surveillance had UTS values ranging from 187 to 204 ksi. As discussed in 3.3 below, these wires also experienced brittle failure at total elongations of about 1%, well below the specified minimum of 4%. A metallurgical report included with the Unit 1 10th year surveillance documentation (Reference 8.14) concluded that the low strength and embrittlement were due to a localized condition resulting from an excessively high percentage of phosphorous

Calvert Cliffs Technical Report Part D - Page 47 of 112 Revision 1 09/15/2020 in the affected sections of wire. An inclusion in the billet from which the wire was fabricated may have been the proximate cause of the condition.

All other test specimens (136 of the 141 tested), including 2 cut from the 42H52 extracted wires and 3 from the 51H62 wire met UTS (and elongation) criteria.

There is no significant difference between the strength of Unit 1 and Unit 2 specimens.

Also, there is no significant difference between the strength of wires from tendons installed during construction and that of wires from replaced tendons.

Figures 8 and 9 are log-time based plots of Unit 1 and Unit 2 wire specimen tensile strength. To limit bias, the plots include only the results of tests on originally installed wire and exclude the results of the on the specimens with the high phosphorous content.

The plots include log linear trend lines for reference. As expected, there is no consistent trend to the UTS values; the trend lines shown are not considered meaningful given the nature of the data. The Unit 1 UTS values plotted on Figure 8 trend to be relatively tightly grouped in any given surveillance year. However, the groupings shift up and down in a seemingly random pattern from year to year. This type of pattern has been observed during evaluations of tests performed on wires extracted from tendons at other plants and is postulated to be the result of variations in testing equipment and techniques.

Given the overall appearance of the UTS plots, it is concluded (as it was in the IWL interval extension reports prepared for other plants) that wire UTS does not vary with time.

In consideration of the above evaluations, it is concluded that further tests to determine tensile strength are not needed and should be eliminated from the containment ISI program unless specified by the Responsible Engineer.

3.3 Wire Elongation at Failure Tables 12a (Unit 1) and 12b (Unit 2) list the elongation at failure, EF, documented during wire tensile testing. These tables also list the mean elongation determined for each extracted wire (Wire Mean) and the mean computed for each examination year (Exam Mean). Most of the reported elongations exceed the 4% minimum specified in ASTM A421. The only exceptions are the 1.0% EF values shown on Table 12a for the 10th year surveillance specimens discussed in 3.2 above. The metallurgical report ascribed both the low strength and the embrittlement to a localized high phosphorous content.

As stated in the table footnotes, a number of EF values are shown in test reports as >4.0%

rather than the actual elongation at failure. The laboratory conducting these tests apparently did not have functioning extensometers (perhaps some were damaged by over

Calvert Cliffs Technical Report Part D - Page 48 of 112 Revision 1 09/15/2020 ranging) with a range sufficient to measure greater elongations. As the actual EF values are unknown, these are shown in the tables as 4.0% (and not >4.0%) for conservatism.

The Table 12a 5th year surveillance EF values are unrealistically high and are considered to represent a testing laboratory error in measurement. The remaining test results show that the replacement tendon wire is somewhat more ductile than the original wire, a probable result of improvements in production techniques.

Figures 10 and 11 are log-time based plots of EF values excluding those shown in the laboratory reports as >4.0% and the replacement tendon wires. The 5th year surveillance results are plotted on Figure 10 to illustrate that these are well outside the expected range.

The remaining EF values, both for Unit 1 and Unit 2, are quite consistent and with one exception (the 6.8% shown for the 3rd year surveillance on Figure 12a) fall into a 4.0% to 6.0% band. This supports the conclusion that wire ductility does not vary with time.

In consideration of the above evaluations it is concluded that further tests to determine wire ductility are not needed and should be eliminated from the containment ISI program.

3.4 Wire Visual Examination and Test Summary The above tabulations, plots, analyses and evaluations, when taken together with results of tests on wire from other post-tensioned containments, support the conclusion that tendon wire strength and ductility are essentially invariant with time. In addition, visual examination of 48 wires extracted from designated23 hoop, vertical and dome tendons between 1975 and 2016 has uncovered no evidence of in-service damage (damage other than that occurring prior to or at the time of initial tensioning or re-tensioning) or identified active corrosion. Further, with one exception (Level 3 found on Unit 1 dome wire designated for extraction during the 40th year surveillance), no Level 3 or higher corrosion has been found on the wires extracted from designated tendons since the 10th year Unit 1 surveillance was completed in 1984.

Since examinations and tests conducted over more than 3 decades have shown that wire condition, strength and ductility are not changing over time, it is concluded that there is no merit to retaining the current requirement for wire examination / testing and for the associated de-tensioning of tendons to extract test wires. It is recommended, on the basis of the foregoing conclusion, that this aspect of post-tensioning system surveillance be discontinued. Testing may be specified by the Responsible Engineer if conditions indicative of wire degradation are found in the course of future end anchorage visual examinations or force measurements.

23 The vertical tendon wire corrosion found during the 20th year surveillance is a separate issue discussed in Subsection 1.3.

Calvert Cliffs Technical Report Part D - Page 49 of 112 Revision 1 09/15/2020

4. End Anchorage Hardware / Concrete Condition During each of the surveillances, sample tendon end anchorage areas were visually examined for evidence of corrosion, presence of free water, discontinuous wires, damage to / distortion of load bearing components and cracks in concrete adjacent to bearing plates. Examination results, excluding the 20th year surveillance expanded scope tendon examination results, are summarized in subsections 4.1 through 4.5.

More than 450 tendons, exclusive of the 20th year expanded scope tendons, were examined (complete examinations including lift-off measurements as well as visual only) during the 10 surveillances completed to date. In almost all cases, both tendon anchorages were examined (in a few cases, only one anchorage was accessible) giving a total of more than 900 anchorage examinations.

A complete listing of the tendons (exclusive of the small replaced / re-tensioned tendon samples) examined during the 10 surveillances is distributed across several tables as shown below.

Surveillance Year Unit 1 Unit 2 1 Tables 4, 6 & 8 Tables 5, 7 & 9 3 Tables 4, 6 & 8 Table 10 (visual exam only) 5 Tables 4, 6 & 8 Table 10 (visual exam only) 10 Tables 4, 6 & 8 Table 10 (visual exam only) 15 Tables 4, 6 & 8 Table 10 (visual exam only) 20 Tables 4, 6 & 8 Table 10 (visual exam only) 25 Table 10 (visual exam only) Tables 5, 7 & 9 30 Tables 4, 6 & 8 Table 10 (visual exam only) 35 Table 10 (visual exam only) Tables 5, 7 & 9 40 Tables 4, 6 & 8 Table 10 (visual exam only) 4.1 Corrosion Load bearing components were visually examined for corrosion and, with exceptions as noted, assigned a condition level as defined in the table included in subsection 3.1 above.

Corrosion documented in the surveillance reports is summarized in Tables 13a (Unit 1) and 13b (Unit 2).

Other than the wide spread corrosion found on vertical tendon components during the 20th year surveillance, there have been relatively few observations of Level 3 and higher corrosion. And, with the exceptions noted below, no Level 3 or higher corrosion has been reported since the 20th year.

Calvert Cliffs Technical Report Part D - Page 50 of 112 Revision 1 09/15/2020 Surveillance Unit Tendon / End Condition Year Level 5 corrosion reported on bearing plate in area 25 2 35H19 / B5 outside the gasket; NCR FN778B-010.

Level 5 corrosion reported on the bearing plate; NCR 35 2 51H13 / B5 N1073-001.

Two discontinuous wires were reported to have 40 1 3D03 / Note a Level 5 corrosion at the break locations; NCR FN1123-004.

Level 3 corrosion reported on test wire; NCR 40 1 3D03 / Note a FN1123-004.

Note a: Tendon end not noted in contractor summary report.

Bearing plate corrosion will be monitored by the Table IWL-2500-1 Category L-A visual examinations performed at 5-year intervals. No other significant corrosion, with the exception of that on the 3D03 wires as described above, has been found over the 14-year period covered by the last 4 surveillances. As the 3D03 anchorages were not examined prior to the 40th year surveillance, the time frame for corrosion development is not known.

It is possible that the corrosion reported was present at the time of construction and that the discontinuous wires broke during or shortly after the initial tensioning.

The above discussions and evaluations support the conclusion that it is acceptable to extend the interval between enclosed end anchorage items to 10 years from the current 5 years. It is unlikely that extending the time between these examinations will result in a failure to uncover an unacceptable condition that has developed over the extended interval.

4.2 Free Water Quantities of free water found at tendon anchorages are shown on Tables 14a and 14b.

These tables identify the surveillance year, tendon ID, anchorage location and quantity of water collected.

4.2.1 Unit 1 Free water in amounts varying from traces or water observed to approximately 1 gallon has been noted (and, presumably, collected if quantified) at 129 tendon anchorages including the anchorages of the 20th year surveillance expanded scope vertical tendons.

Since the 20th year surveillance, only 9 observations of water have been reported. Of the amounts identified, 6 were reported as drops to 1 oz. The remaining 3 amounts were quantified as noted below.

Calvert Cliffs Technical Report Part D - Page 51 of 112 Revision 1 09/15/2020 Surveillance Year Tendon / End Quantity Reported 35 1D29 / South end 20 oz.

35 34V13 / Bottom end 6 oz.

40 3D16 / North end 76 oz.

Quantities of 3 oz or less (i.e., <0.1 liter) are deemed too small to result in significant corrosion and are not considered further in this report. All of the vertical tendons (both units) were well sealed by new end caps in 2002, just prior to the 25th year surveillance.

For this reason, it is presumed that the 6 oz. quantity shown above for 34V13 was present and trapped in a CPM pocket when the original CPM was drained prior to replacing of the end caps and refilling.

Water at the 2 dome tendon anchorages probably accumulated prior to completion of the 2002 drainage improvement work at the top of the ring girder. While the quantities are significant, there was no report of Level 3 or higher corrosion at these anchorages. CPM sample water contents (see section 5) were on the high side, 5.2% at the 1D29 anchorage and 7.1% at the 3D16 anchorage, but still below the 10% acceptance limit.

4.2.2 Unit 2 Free water in amounts varying from traces or water observed to approx. 2 - 3 gal has been noted (and, presumably, collected if quantified) at 106 tendon anchorages including the anchorages of the 20th year surveillance expanded scope (all) vertical tendons.

Since the 20th year surveillance, only 4 observations of water have been reported. Of these, 3 were reported as 3 oz. or less. The only quantity considered significant is the 10 oz. collected at the Buttress 6 end of 62H03 during the 30th year surveillance as shown in Table 14b. The CPM sample water content was on the high side at 4.7% but still below the 10% acceptance limit. Corrosion found at the anchorage was limited to Levels 1 and 2.

4.2.3 Free Water pH Analysis Reports documenting surveillances through the 25th year do not address testing of free water samples to determine pH. Results of tests performed on water samples collected during the 30th, 35th and 40th year surveillances are shown below.

Surveillance Year Number of Samples Tested pH Value or Range 30 1 7.72 35 2 7.19 - 8.70 40 3 7.40 - 8.41

Calvert Cliffs Technical Report Part D - Page 52 of 112 Revision 1 09/15/2020 All sample pH values are basic (>7) showing that the water collected is not corrosive.

4.2.4 Conclusion Regarding Free Water On the basis of the evaluations and discussions in 4.2.1 through 4.2.3 above, it is concluded that the post-tensioning system examination interval can be extended to 10 years with little risk of missing deleterious conditions that have developed over the greater interval as a result of free water accumulation in tendon ductwork. This conclusion is supported by the following observations and surveillance requirements.

There have been few observations of free water during the 25th year and later surveillances.

Water intrusion into vertical tendon ductwork has been effectively ended by replacement of the end caps prior to the 25th year surveillance.

Free water samples tested during the 30th, 35th and 40th year surveillances have all had pH levels above 7 and are, therefore, basic and non-corrosive.

Water found in tendon ductwork during the 25th year and later surveillances caused no significant corrosion (Levels of 3 or greater) of tendon wire, anchor heads, bushings or shims.

Therefore, it is concluded that future free water intrusion will not have a significant impact on post-tensioning system load bearing items and, that the examination of post-tensioning system items enclosed by the end caps can be extended to 10 years with little risk of missing free water induced conditions that could impair system integrity.

4.3 Missing / Discontinuous Wires Missing or discontinuous (broken / missing button heads) wires found during a surveillance and not previously documented (i.e., at the time of initial tensioning, re-tensioning or a prior surveillance) are, with the exception of those found at vertical tendon anchorages during the 20th year surveillance, listed in Tables 15a (Unit 1) and 15b (Unit 2). Vertical tendon conditions found during that surveillance are addressed separately in subsection 1.3 above.

Calvert Cliffs Technical Report Part D - Page 53 of 112 Revision 1 09/15/2020 Relatively few missing / protruding button heads and discontinuous wires have been documented as noted below.

Missing button heads: 14 Protruding button heads (wire shown or presumed to be continuous): 3 Discontinuous wires: 8 Missing wires: 1 The wire reported as missing from Unit 1 tendon 62H24 during the 20th year surveillance is presumed to have been missing at the time of initial installation. However, this is based on observation of an empty hole in each of the anchor heads. Since there is no report of testing for continuity of the remaining wires, the observed condition is conservatively treated as 2 additional missing button heads and, therefore, 2 additional ineffective wires.

If the wires with protruding button heads are also treated as ineffective, the total number of ineffective wires found over the course 10 surveillances is 27 (treating the wire reported as missing during the 20th year surveillance as 2 discontinuous wires), exclusive of vertical tendon wires found to be ineffective during the 20th year surveillance.

Exclusive of vertical tendons examined during the 20th year surveillance, approximately 420 different tendons (i.e., counting only once common tendons and others examined 2 or more times) have been examined over the course of the 10 surveillances completed to date. These are comprised of 420

• 90 = 37,800 wires. Of the 37,800 wires, 27, or 0.07% are considered ineffective. This percentage is too small to be considered structurally significant.

As the percentage of ineffective wires documented over the 41 year interval between the first (1975) and most recent (2016) surveillances is very small, it is concluded that wire breakage / button head detachment in service can be adequately monitored by examinations performed at intervals of 10 years rather than the current 5 years.

4.4 Load Bearing Component Damage / Distortion During the 1st year Unit 1 surveillance, two hoop tendon anchor heads were found to have minor damage as described below.

Tendon 42H36 / Buttress 4 - A crescent shaped sliver (found in the CPM) was sheared off the outside edge of the anchor head bearing face. The reduction in bearing area was computed and, following an engineering evaluation, the damage was concluded to be insignificant. The condition was accepted as is.

Calvert Cliffs Technical Report Part D - Page 54 of 112 Revision 1 09/15/2020 Tendon 42H74 / Buttress 2 - The anchor head (report does not indicate which face) had a peened area about 1/8 x 2-1/2 at the outside edge. Following an evaluation, the damage was concluded to be minor and the condition was accepted as is.

Both of the above conditions must have existed at the time that initial tensioning of these tendons was completed.

Other than the above, no load bearing component (anchor head, shims, bearing plates) damage or distortion has been reported. In addition, no cracks have been found in load bearing components.

Therefore, it is concluded that load bearing component damage / distortion (as well as cracking) is not a significant issue and, that detailed examinations of anchorage components to assess damage can be performed at intervals of 10 years.

4.5 Concrete Cracking Adjacent to Bearing Plates No anchorage area concrete cracks wider than 0.01 inches have been reported.

Therefore, it is concluded that cracking of concrete adjacent to tendon end anchorage bearing plates is not an issue and that close in examinations of these areas at intervals of 10 years is adequate to monitor this condition.

4.6 End Anchorage Condition Summary and Conclusions Tendon end anchorage hardware and adjacent concrete have performed well throughout the life of the plant (through the most recent surveillance in 2016) and show no trends of deteriorating condition.

Free water has been found during end anchorage examinations as documented above, but has not resulted in a significant amount of corrosion except at the upper ends of vertical tendons as documented in the 20th year surveillance reports and discussed in subsection 1.3. All samples of free water that have been tested to date have shown the water to be alkaline with a pH greater than 7 and, therefore, noncorrosive.

Water intrusion into the vertical tendon ductwork was effectively eliminated by the installation of newly designed end caps prior to the 25th year surveillance and no significant corrosion of vertical tendon enclosed anchorage items or wires has been reported since.

Calvert Cliffs Technical Report Part D - Page 55 of 112 Revision 1 09/15/2020 Major corrosion has been observed on hoop tendon bearing plate areas outside the end cap gasket. This will continue to be monitored and corrected during quintennial concrete surface examinations as well as the enhanced visual examinations addressed in Section 7 below.

Significant corrosion has been found at several hoop and dome broken wire fracture locations. Since there is no indication as to when corrosion was initiated and when the fractures occurred, there is no way to associate the conditions with post-construction water intrusion. It is possible that additional broken wires with corroded fracture zones will be found during future hoop and dome tendon examinations but, based on past experience, such observations are expected to be few.

Only 27 ineffective wires (exclusive of vertical wires examined during the 20th year surveillance) not previously reported have been found. These represent only a miniscule fraction (<0.07%) of the ~37,800 wires comprising the ~420 tendons examined.

No major damage, no cracking and no distortion have been found during visual examinations of bearing plates, anchor heads and shims. Minor damage reported for 2 anchor heads in the Unit 1 1st year surveillance report is concluded to have been caused during original tendon installation / tensioning but not noted and documented at that time.

No cracks wider than 0.01 inches have been found on the surface of the concrete adjacent to tendon bearing plates.

Considering the above, it can be concluded that end anchorage conditions are relatively stable and unlikely to change significantly before the deadline for completion of the next surveillance if the interval is extended to 10 years. And therefore, it can be concluded that the end anchorage examination interval can be extended to 10 years, with enhanced intermediate visual examinations of the ring girder top shelf and buttress well areas as described in Section 7, without compromising the safety of the plant.

Calvert Cliffs Technical Report Part D - Page 56 of 112 Revision 1 09/15/2020

5. Corrosion Protection Medium Testing Corrosion protection medium (CPM) test samples were collected at the ends of sample tendons during each of the 10 surveillances. Each CPM sample was tested for the presence of three corrosive ions (chlorides, nitrates and sulfides), absorbed water content and neutralization number.

Corrosion protection medium test results are summarized below and addressed in detail in 5.1 through 5.3. Conclusions and recommendations for future testing are included in 5.4.

With one exception, considered to be the result of sample contamination or a laboratory error as subsequently discussed, all tested samples met the Table IWL-2525-1 10 ppm upper limit on chloride, nitrate and sulfide ion concentration24.

All tested samples are concluded to have met the Table IWL-2525-1 neutralization number criterion for reserve alkalinity.

With two exceptions (documented during the Unit 1 3rd year surveillance), all tested samples met the Table IWL-2525-1 10% upper limit on water content.

5.1 Corrosive Ion Concentrations Tables 16a (Unit 1) and 16b (Unit 2) list, for each surveillance year, the following data applicable to the ion concentrations documented for CPM samples.

Surveillance year Number of samples tested Number of samples with chloride concentrations 1 ppm and the maximum concentration Number of samples with nitrate concentrations 1 ppm and the maximum concentration Number of samples with sulfide concentrations 1 ppm and the maximum concentration All concentrations, with the exception of those shown in Table 16b for nitrate and sulfide ions on the 40th year line, are below the 10 ppm limit. As stated in the note (Note d) below 24 Ion concentrations are determined for a water extraction prepared in accordance with the procedures described in Subsection IWL Table IWL-2525-1 and do not represent concentration in the bulk CPM sample.

Calvert Cliffs Technical Report Part D - Page 57 of 112 Revision 1 09/15/2020 the tables, the 25 ppm values shown for these concentrations are concluded to represent either sample contamination, testing errors or data transcription errors.

There is no trend to any corrosive ion concentration values listed in the tables.

Based on the above discussion, it is concluded that the presence of corrosive ions in surveillance tendon CPM is not a concern. And, it is concluded that there is no need to continue testing CPM samples for corrosive ions unless the Responsible Engineer specifies such tests following observations of corrosion, water intrusion into tendon end anchorage areas or ducting or, a significant level of absorbed water in CPM samples.

5.2 Reserve Alkalinity / Neutralization Number Tables 17a (Unit 1) and 17b (Unit 2) list, for each surveillance year, the following data applicable to the neutralization (or base) numbers documented for CPM samples.

Surveillance year Number of samples tested Maximum base number Minimum base number All tendons were initially filled with Visconorust 2090P casing filler which has a low as-compounded base number (on the order of 5). Subsequently, many tendons have been refilled or topped off with a later product formulation, 2090P-4, which has a minimum as-compounded base number of 35. Samples taken from tendons with a mixture of the two formulations may contain all of one, all of the other or any combination of the two.

The minimum required base number as specified by Table IWL-2525-1 is either half the as-installed number or zero if the as-installed number is 5 or less. Table IWL-2525-1 treats mixtures as being governed by the component with the lowest as-installed number.

Therefore, the base number acceptance limit for all CPM samples is considered to be zero.

All samples, with a few exceptions, have a reported base number greater than zero.

Several samples that apparently did not meet the criterion were retested for acid number using a procedure that was not specified in the surveillance contractor reports. Table IWL-2525-1 does not address acid number testing. Considering the questionable results documented for base number tests on CPM samples taken at other plants, it is concluded that all of the Calvert Cliffs samples do, in fact, have an acceptable base number. In any event, the few acid numbers reported by the laboratory are small (3.42 is the largest) which is close to effective neutrality.

Calvert Cliffs Technical Report Part D - Page 58 of 112 Revision 1 09/15/2020 Neither minimum nor maximum base numbers show a definitive trends indicating that CPM composition is relatively stable over time.

Based on the above discussion, it is concluded that degradation of CPM neutralization capacity is not a concern. And, it is concluded that there is no need to continue testing CPM samples for neutralization number unless the Responsible Engineer specifies such tests following observations of corrosion or acidic water intrusion into tendon end anchorage areas or ducting.

5.3 Absorbed Water Content Tables 18a (Unit 1) and 18b (Unit 2) list, for each surveillance year, the following data applicable to CPM sample water content.

Surveillance year Number of samples tested Surveillance year maximum reported water content Number of samples with water content >1%

With three exceptions, all tested samples had a water content of less than 10%. The exceptions are 28.06% and 19.21% values recorded for Unit 1 samples collected during the 3rd year surveillance and an 11.7% value recorded for a Unit 2 vertical tendon sample collected during the 20th year surveillance. These are not evaluated in the surveillance reports. At the time of the 3rd year surveillance the tests were not addressed in Regulatory Guide 1.35 (then at Revision 2) and there were no applicable acceptance criteria. The 11.7% value recorded during the 20th year surveillance is noted in the Unit 2 report as exceeding the 10% acceptance limit. The report does not cite an NCR.

Maximum water contents do not show definitive trends. However, as absorbed water content provides an early indication of potentially corrosive conditions, the requirement to collect and test CPM samples for absorbed water during each future surveillance will be retained.

5.4 CPM Test Summary and Conclusions Corrosive ion (chlorides, nitrates, sulfides) concentration in sample extractions is below the 10 ppm limit and shows no trend of increasing over time.

Calvert Cliffs Technical Report Part D - Page 59 of 112 Revision 1 09/15/2020 Sample neutralization number (base number) samples are concluded to have met the acceptance criterion and show no trend indicating that the corrosion protection capacity of the CPM is degrading over time.

Absorbed water content, with the two early exceptions noted above, is below the 10%

(of dry weight) limit and shows no trend of increasing over time.

The CPM test results summarized above support to the conclusion that the interval between such tests can be extended to 10 years with no adverse consequences.

In addition, unless evidence of active corrosion is found during visual examinations of end anchorage hardware and extracted wires, there is evidence of free water intrusion or the quantity of absorbed water is found to have increased over time, there should be no need to perform the tests for corrosive ions and neutralization number. It is concluded that these tests need be done only if corrosion or moisture conditions favoring corrosion are found, in which case tests will be performed as specified by the Responsible Engineer.

Calvert Cliffs Technical Report Part D - Page 60 of 112 Revision 1 09/15/2020

6. Overall Summary, Conclusions and Recommendations A summary of post-tensioning system surveillance results, conclusions based thereon and recommendations for surveillance program scope reductions and supporting enhancements follow.

6.1 Summary of Calvert Cliffs Surveillance Results The results of the 10 post-tensioning system inservice examinations performed between 1975 and 2016 show that the system can be expected to perform its intended function through T = 100 years which is well past the presumed unit maximum operating lifetime of 80 years. Performance of the system, determined by evaluations of the visual examination findings / test results as detailed in the preceding sections, is summarized below.

6.1.1 Tendon Force The mean force in each of the tendon groups is projected by log-linear regression and 95% confidence limit computations to remain above the specified minimum through T =

100 years.

6.1.2 End Anchorage Condition, Free Water and Discontinuous Wires Other than the extensive corrosion found on vertical tendon wires during the 20th year surveillance there have been relatively few documented instances of end anchorage hardware and wire damage or degradation. As discussed in the preceding sections, water intrusion into and consequent corrosion of vertical tendon wires was effectively eliminated prior to the 25th year surveillance by the corrective actions taken in 2002.

Observations of Level 3 and greater corrosion during the 25th year and subsequent surveillances are limited to that on two bearing plates, two discontinuous wires and one wire extracted for tensile testing as shown on Tables 13a and 13b.

No end anchorage area concrete cracks wider than 0.01 inches have been reported.

Free water was collected or only observed (quantity too small to collect) at 13 tendon anchorages during the 25th year and subsequent surveillances. Quantities considered significant (over 3 oz. or 0.1 liter) were found at 4 of these anchorages. Level 3 or greater corrosion (on discontinuous wires and the wire extracted for tensile testing) was reported for only one of the anchorages where free water was collected.

All free water samples tested for pH were basic (pH >7) and, therefore, not corrosive.

Calvert Cliffs Technical Report Part D - Page 61 of 112 Revision 1 09/15/2020 Eight discontinuous wires were found during the 25th year and subsequent surveillances.

Overall, 204 tendons with 18,360 wires were examined during these surveillances.

Discontinuous wires represent only 0.04% of the total. There is no indication that the number of discontinuous wires is increasing over time.

6.1.3 Tendon Wire Strength and Ductility With a few exceptions, tests on samples cut from extracted wires show that ultimate tensile strength and elongation at failure meet the ASTM A421 (Reference 8.26) acceptance criteria and are essentially unchanged over time. The exceptions are a single tensile strength of 238 ksi (2 ksi below the 240 ksi limit) reported for a test on a possibly corroded section of the test wire and low values of both tensile strength and elongation reported for 4 tests on specimens from 2 wires (both extracted from the same tendon).

The low strength and ductility were ascribed by the metallurgical report on break evaluation to embrittlement resulting from localized phosphorous inclusions, an unusual, and extremely rare, condition.

6.1.4 Corrosion Protection Medium Characteristics Results of corrosion protection medium (CPM) tests to determine absorbed water content, corrosive ion concentrations and neutralization number confirm that acceptance criteria, with few exceptions, have been met and that there are no discernible trends over time.

In particular:

All reported absorbed water content values except 3, are below the 10% (of dry weight) upper limit. The 3 exceptions are 28.06% and 19.21% values reported for samples collected at 2 upper hoop tendon anchorages during the Unit 1 3rd year surveillance and 11.7% reported for a sample collected from a Unit 2 vertical tendon bottom anchorage during the 20th year surveillance. The two larger values are suspect and may have resulted from sample contamination or a laboratory error. The vertical tendon sample water content seems reasonable given the extensive water intrusion found during the 20th year surveillance.

With two exceptions, all corrosive ion concentrations are below the 10 ppm upper limit and many are below the indicated limit of resolution applicable to the ion. The exceptions are <25 ppm nitrate and sulfide concentrations reported for a sample collected at an upper hoop tendon anchorage during the 40th year surveillance. As the normal limit of resolution for these ions is 0.5 ppm, values reported as <25 ppm are suspect and may represent transcription or typographical errors. There are no discernible trends to the reported ion concentrations.

All neutralization numbers are deemed to be acceptable. There is no apparent trend to the neutralization number data which leads to the conclusion that the corrosion protection capacity of the CPM is not degrading with time.

Calvert Cliffs Technical Report Part D - Page 62 of 112 Revision 1 09/15/2020 6.2 Conclusions Based on the evaluations detailed in sections 2 through 5 and summarized above, it is concluded that the Calvert Cliffs Unit 1 and Unit 2 containment post-tensioning systems will continue to perform the specified design functions until well beyond the deadline for completion of the next surveillance if the interval is extended to 10 years. And, in particular:

Tendon group mean force will remain above the specified minimum.

End anchorage hardware and tendon wire will remain free of detrimental effects due to active corrosion.

Tendon wire tensile strength and ductility will not change over time.

Structurally significant cracks will not develop in the vicinity of tendon end anchorage areas.

Corrosion protection medium will retain its protective properties with no degradation over time.

Free water will not be a concern.

6.3 Recommendations On the basis of the above conclusions it is recommended that the post-tensioning system examination and testing interval be extended to 10 years and that the requirement for wire extraction and testing be eliminated. This extension and the elimination of wire tests will maintain an acceptable level of quality and safety as well as provide the following benefits.

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

o Working at heights; o Reducing time worked in radiation and contamination areas; o Working in a de facto confined space (the tendon gallery);

o Working with high pressure hydraulic systems; o Working near high energy plant systems; o Working around solvent and hot petroleum product fumes; o Working close to containers and pressurized lines filled with hot petroleum products;

Calvert Cliffs Technical Report Part D - Page 63 of 112 Revision 1 09/15/2020 o Close in exposure to high levels of stored elastic energy in tendons (sudden rotation during force measurement has resulted in high speed shim ejection);

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

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

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 need only be performed 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.

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.

The above recommendation for overall examination interval extension to ten years will be supported by additional local area examinations and enhancements to the Subsection IWL containment exterior examination as described in the following section.

Calvert Cliffs Technical Report Part D - Page 64 of 112 Revision 1 09/15/2020

7. Future Examinations and Testing Enhancements In conjunction with implementing the proposed program changes from the current post-tensioning system examination program, Calvert Cliffs will initiate the local area visual examinations and enhancements to the Subsection IWL containment exterior visual examination program as described below.

7.1 Local Area Visual Examinations Ponding of water on the top shelf of the ring girder and flooding of buttress sumps has resulted in leakage of water into tendon ductwork and corrosion of post-tensioning system components. Timely detection and correction of water accumulation in these areas as well as the resulting corrosion of exposed hardware will be ensured by the following local area examinations.

7.1.1 Ring Girder Examinations The top shelf of each ring girder will be visually examined at a frequency specified by the Responsible Engineer (RE). Examinations will focus on evidence of water ponding, corrosion at visible edges of bearing plates, corrosion at the edges of gasket retainer plates, end cap corrosion and CPM leakage from end caps.

If evidence of ponding, corrosion or CPM leakage is detected, the condition will be evaluated by the RE who will determine if further examination and / or corrective action is needed. The RE will develop plans for, and oversee, additional examinations and corrective action as deemed necessary.

7.1.2 Buttress Access Well Examinations Each buttress sump area will be visually examined at a frequency specified by the RE.

Examinations will focus on evidence of flooding, corrosion of bearing plates, end cap corrosion and CPM leakage from end caps.

If evidence of flooding, corrosion or CPM leakage is detected, the condition will be evaluated by the RE who will determine if further examination and / or corrective action is needed. The RE will develop plans for, and oversee, additional examinations and corrective action as deemed necessary.

Calvert Cliffs Technical Report Part D - Page 65 of 112 Revision 1 09/15/2020 7.2 Subsection IWL Containment Exterior Examination Enhancements As noted in Part B of this technical report, visual examinations of the containment exterior will continue at intervals of 5 years in accordance with Subsection IWL-2410. This examination program will include enhanced procedures that address more comprehensive coverage of tendon end anchorage areas. The enhanced visual examinations will focus on detecting corrosion, damage distortion and crack development at end caps, bearing plates and anchorage area concrete as well as CPM leakage.

General visual examination, as defined in IWL-2310(a), of tendon end caps, bearing plates and anchorage area concrete for evidence of damage / deformation, corrosion, cracking and corrosion protection medium leakage will be performed from roofs, floors, platforms, ladders and other means of achieving relatively close in access to the anchorage area and with sufficient illumination to detect deleterious conditions. If close in access is not possible, remote examination techniques (e.g., optical aids and drone mounted cameras) will be used.

Detailed visual examination, as defined in IWL-2310(b), will be conducted at those areas identified by the RE during general visual as areas with conditions requiring close in examination.

If an end anchorage area examination uncovers a condition indicative of possible damage to the enclosed post-tensioning system hardware or an anchor head failure, the end cap will be removed for further examination and evaluation by the (RE). Following the evaluation, additional actions will be taken as specified by the RE.

If an end anchorage area examination uncovers active corrosion on a bearing plate or end cap, the condition will be evaluated by the RE who will specify corrective measures as deemed appropriate.

The RE will evaluate end anchorage area concrete cracks for structural significance and perform a detailed examination of any judged to be structurally significant. Following this examination, the RE will perform additional evaluations, specify further analysis and specify corrective measures as deemed appropriate.

Visual examinations will also focus on leakage of CPM. Observed leakage will be evaluated by the RE who will determine whether or not corrective action is needed. If needed, a corrective action (e.g., end cap gasket replacement and duct refilling / top-off) plan will be prepared by, and implemented under the direction of the RE.

Calvert Cliffs Technical Report Part D - Page 66 of 112 Revision 1 09/15/2020

8. Part D References 8.1 ASME Boiler and Pressure Vessel Code,Section XI, Subsection IWL, 2013 Edition.

8.2 Calvert Cliffs Nuclear Power Plant / Baltimore Gas and Electric Company /

Structural Integrity Test Report / Containment Structure / Unit 1, report prepared by Bechtel Power Corporation / Gaithersburg, Maryland, February 1974.

8.3 Calvert Cliffs Nuclear Power Plant / Baltimore Gas and Electric Company /

Structural Integrity Test Report / Containment Structure / Unit 2, report prepared by Bechtel Power Corporation / Gaithersburg, Maryland, June 1976.

8.4 ESP No. ES199800135, an engineering evaluation report documenting evaluation of Unit 1 and Unit 2 vertical tendon corrosion found during the 20th year surveillance and the subsequent corrective actions, Revision 0, approved 27 December 2002.

8.5 Baltimore Gas and Electric Company / Calvert Cliffs Nuclear Power Plant Unit 1 /

Containment Structure Post-Tensioning System One-Year Surveillance, report by Bechtel Power Corporation, Gaithersburg, Maryland, July 1975.

8.6 STP No. M-672-2, Unit 2 Containment Tendon Surveillance, completed test procedure documenting the 1st year Unit 2 surveillance, signed complete 27 September 1977 and approved 26 September 1979.

8.7 Calvert Cliffs Nuclear Power Plant / Baltimore Gas and Electric Company / Unit No. 1 / Containment Tendon Surveillance / Three-Year Surveillance / (Three Years After SIT), report by Bechtel Power Corporation, Gaithersburg, Maryland, May 1977.

8.8 STP No. M-663-2, Containment Tendon Surveillance - Unit 2, completed test procedure documenting the 3rd year Unit 2 surveillance, signed complete 02 November 1979.

8.9 Untitled test report and data package attached to a 05 April 1979 memorandum from B. C. Rudell (BG&E) to D. T. Ward (BG&E); subject Calvert Cliffs Nuclear Power Plant Unit No. 1 / Containment Structure Post-Tensioning System / Five-Year Surveillance.

8.10 Calvert Cliffs Nuclear Power Plant Unit 1 5th year containment post-tensioning system surveillance original data; maintained in a ring binder titled STP 1-T-2 /

Unit 1 / Five Year Survey / New STP # M-663-1.

8.11 STP No. M-663-2, Containment Tendon Surveillance - Unit 2, completed test procedure documenting the 5th year Unit 2 surveillance, approved with Change #1 29 July 1981.

Calvert Cliffs Technical Report Part D - Page 67 of 112 Revision 1 09/15/2020 8.12 Calvert Cliffs Nuclear Power Plant / Baltimore Gas and Electric Company / Unit 1

/ Containment Tendon Surveillance / Ten-Year Surveillance / Ten Years After SIT, undated report.

8.13 STP-M-663-1, Containment Tendon Surveillance, completed test procedure documenting the 10th year Unit 1 surveillance, approved 24 July 1985.

8.14 STP No. M-663-2, Containment Tendon Surveillance - Unit 2, completed test procedure documenting the 10th year Unit 2 surveillance, approved 26 February 1986.

8.15 STP-M-663-1, Containment Tendon Surveillance - Unit 1, completed test procedure documenting the 15th year Unit 1 surveillance, signed complete 27 May 1991.

8.16 STP No. M-663-2, Containment Tendon Surveillance - Unit 2, completed test procedure documenting the 15th year Unit 2 surveillance, signed complete 10 October 1991.

8.17 Precision Surveillance Corporation report, 20th Year Surveillance of the Unit 1 Containment Building Post Tensioning System at Calvert Cliffs Nuclear Plant, 1997.

8.18 Precision Surveillance Corporation report, 20th Year Surveillance of the Unit 2 Containment Building Post Tensioning System at Calvert Cliffs Nuclear Plant, 1997.

8.19 Precision Surveillance Corporation report, Twenty-Fifth Year Visual Surveillance of the Calvert Cliffs Nuclear Power Plant, Unit 1 Containment, Revision 0, 03 March 2004.

8.20 Precision Surveillance Corporation report, Calvert Cliffs Nuclear Power Plant Twenty-Fifth Year Unit 2 Physical Containment Tendon Surveillance, Revision 0,

[not dated].

8.21 Precision Surveillance Corporation report (Document CC-N1019-501), Final Report for the 30th Year Containment IWL Inspection at Calvert Cliffs Nuclear Power Plant Units 1 and 2, Revision 0, 19 March 2009.

8.22 Precision Surveillance Corporation report (Document REP-1073-510), Final Report for the 35th Year Tendon Surveillance at Calvert Cliffs, Revision 2, 04 December 2014.

8.23 Precision Surveillance Corporation report (Document 1123-501), Final Report for the 40th Year Tendon Surveillance at Calvert Cliffs, Revision 0, 13 February 2017.

8.24 DCALC No. CA06062, Containment Tendon Force Versus Time Curves - Units 1

& 2, Revision 2, approved 06 January 2003.

Calvert Cliffs Technical Report Part D - Page 68 of 112 Revision 1 09/15/2020 8.25 Miller, Irwin and John E. Freund, Probability and Statistics for Engineers, Prentice-Hall, Englewood Cliffs, NJ, 1965.

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

8.27 Prestressing Report / Containment Building / Baltimore Gas and Electric Company

/ Calvert Cliffs Power Plant Unit No. 1 / Job No. 6750, report prepared by Bechtel Power Corporation, Gaithersburg, Maryland, November 1973.

8.28 Prestressing Report / Containment Structure / Baltimore Gas and Electric Company / Calvert Cliffs Nuclear Power Plant Unit No. 2 / Project No. 6750, report prepared by Bechtel Power Corporation, Gaithersburg, Maryland, June 1977.

Calvert Cliffs Technical Report Part D - Page 69 of 112 Revision 1 09/15/2020

9. Part D Tables and Figures Tables and figures cited in Part D follow.

Calvert Cliffs Technical Report Part D - Page 70 of 112 Revision 1 09/15/2020 Table 1a - Unit 1 New / Re-Tensioned Tendon As-Found and As-Left Force New or New or Tendon As-Found As-Left Tendon As-Found As-Left Re- Re-ID Force, kip Force, kip ID Force, kip Force, kip tension tension 12V02 637 750 61V06 N/A 743 12V03 645 797 61V09 N/A 745 12V07 N/A 755 61V10 824 750 12V09 669 776 61V11 681 748 12V13 675 750 61V12 742 750 12V17 658 747 61V14 737 754 12V21 701 752 61V15 New 720 756 12V23 734 750 61V19 741 754 12V25 700 752 61V21 712 763 12V30 707 745 61V23 697 742 12V33 637 756 61V26 567 761 23V07 587 752 61V30 593 756 23V17 704 751 61V31 N/A 749 23V29 611 754 12V06 642 738 23V33 669 747 12V18 564 733 34V05 720 747 23V19 646 738 34V07 690 750 23V21 631 734 New 34V11 N/A 750 23V22 636 737 34V16 N/A 748 23V25 617 736 34V23 661 747 23V28 512 738 34V24 706 756 34V01 624 742 34V25 591 771 34V02 637 737 45V10 647 748 34V06 615 737 Re-tension 45V22 673 753 34V13 687 738 45V23 622 747 45V04 632 727 56V05 656 758 45V17 571 737 56V09 683 743 56V02 586 732 56V22 609 749 56V12 628 726 56V26 573 751 56V14 612 739 56V28 669 757 56V15 613 732 56V29 630 749 56V27 643 732 56V31 588 753 56V33 590 736 56V32 694 749 61V20 643 748 61V03 653 744 Total Force, kip 39,742 50,122

Calvert Cliffs Technical Report Part D - Page 71 of 112 Revision 1 09/15/2020 Table 1b - Unit 2 New / Re-Tensioned Tendon As-Found and As-Left Force New or New or Tendon As-Found As-Left Tendon As-Found As-Left Re- Re-ID Force, kip Force, kip ID Force, kip Force, kip tension tension 12V03 656 746 61V01 671 756 23V01 512 753 61V12 676 746 23V05 654 748 61V13 673 750 23V06 609 748 61V17 670 744 New 23V19 550 752 61V21 617 746 23V21 650 748 61V26 656 748 23V25 682 750 61V28 689 755 23V26 625 753 61V34 650 752 23V28 620 756 12V01 584 739 34V03 659 753 12V13 555 729 34V07 670 751 12V24 626 735 34V09 521 751 12V30 629 728 34V11 690 744 12V33 640 733 34V14 654 748 23V02 633 732 34V15 633 756 23V14 646 738 34V18 663 746 23V15 525 739 34V22 685 754 23V30 639 732 34V23 668 756 34V17 632 736 34V25 585 756 45V05 631 731 New 45V07 600 747 45V06 540 733 45V19 614 754 45V08 524 730 45V25 625 755 45V09 641 727 45V33 644 744 45V10 500 734 Re-tension 56V01 608 745 45V12 604 736 56V03 641 760 45V13 585 739 56V09 667 745 45V14 602 738 56V11 649 753 45V16 632 734 56V13 613 756 45V18 562 738 56V18 673 750 45V27 463 730 56V19 656 746 45V32 635 735 56V22 624 749 56V06 644 732 56V23 650 753 56V07 644 729 56V24 641 756 56V08 633 763 56V25 654 755 56V21 638 735 56V27 645 743 56V31 639 734 56V29 625 759 61V11 632 733 56V32 674 749 61V20 645 742 56V33 694 749 61V29 635 738 Total Force, kip 47,623 56,584

Calvert Cliffs Technical Report Part D - Page 72 of 112 Revision 1 09/15/2020 Table 2 - Trend Line Parametersa Tendon Unit Tendons / Data Range a b tm Fm F100 LCL100 Group All / From 1st yr ISI 644.4 --20.0 1.0195 624.0 604 591 1

Hoop All / From 10 yr ISI th 529.3 +60.2 1.4003 613.5 650 623 2 All / From 1 yr ISI st 636.8 -8.4 1.0209 628.2 620 610 1 All / From 1 yr ISI st 703.0 -12.0 1.0218 690.7 679 649 Vertical 2 All / From 1st yr ISI 679.2 -9.6 1.1795 667.8 660 639 1 All / From 1st yr ISI 662.2 -16.3 1.0017 645.9 630 619 Dome 2 All / From 1 yr ISI st 657.8 -3.3 0.9887 654.6 651 640 Note a: Parameters are defined below.

a - Trend line ordinate, kip, at T = 1 (Log T = 0); T is time in years since the unit SIT b - Trend line slope, kip per unit logarithmic interval tm - Mean of Log T values over the data range Fm - Mean of F (lift off force) values over the data range F100 - Trend line ordinate at T = 100; LCL100 - 95% lower confidence limit, kip, on F100.

Calvert Cliffs Technical Report Part D - Page 73 of 112 Revision 1 09/15/2020 Table 3a - SIT & Surveillance Datesa Unit 1 Unit 2 Event Start Mid-point End Start Mid-point End SITb N/A 24 Nov 73 N/A N/A 01 Apr 76 N/A 1st year ISI 08 Jan 75 12 Mar 75 17 Apr 75 21 Mar 77 13 Apr 77 6 May 77 3rd year ISI 14 Sep 76 16 Nov 76 19 Jan 77 07 Sep 79 04 Oct 79 01 Nov 79 5 year ISI th 17 Aug 78 02 Nov 78 19 Jan 79 23 Jul 81 03 Sep 81 16 Oct 81 10th year ISI 05 Nov 84 19 Nov 84 04 Dec 84 17 Sep 85 26 Sep 85 05 Oct 85 15th year ISI 16 Apr 91 06 May 91 27 May 91 25 Sep 91 01 Oct 91 08 Oct 91 20th year ISI 01 May 97 15 Sep 97 31 Jan 98 01 May 97 15 Sep 97 31 Jan 98 25th year ISI 01 Oct 02 01 Dec 02 31 Jan 03 01 Oct 02 01 Dec 02 31 Jan 03 30 year ISI th 13 May 08 11 Jun 08 11 Jul 08 13 May 08 11 Jun 08 11 Jul 08 35th year ISIc 15 Aug 12 02 Oct 12 19 Nov 12 15 Aug 12 02 Oct 12 19 Nov 12 40th year ISI 08 Aug 16 23 Sep 16 09 Nov 16 08 Aug 16 23 Sep 16 09 Nov 16 Note a: As shown in Unit SIT reports (References 8.2 & 8.3). Surveillance procedure packages and reports (References 8.5 through 8.23).

Note b: SIT date is the date at the start of containment de-pressurization from peak pressure.

Note c: Unit 2 hoop tendon 42H06 examination deferred to the 1014 outage. All other surveillance activities completed between the start and end dates shown.

Calvert Cliffs Technical Report Part D - Page 74 of 112 Revision 1 09/15/2020 Table 3b - T Calculation Summarya, b, c Unit 1 Unit 2 Event Year Month Day Base T T Year Month Day Base T T SIT 1973 11 24 2.90 0.0 1976 04 01 0.0 1st year ISI 1975 03 12 4.20 1.3 1977 04 13 6.29 1.0 3rd year ISI 1976 11 16 5.88 3.0 1979 10 04 8.76 3.5 5 year ISI th 1978 11 02 7.84 4.9 1981 09 03 10.68 5.4 10th year ISI 1984 11 19 13.89 11.0 1985 09 26 14.74 9.5 15th year ISI 1991 05 06 20.35 17.5 1991 10 01 5.25 15.5 20th year ISI 1997 09 15 26.71 23.8 1997 09 15 26.71 21.5 25th year ISI 2002 12 01 31.92 29.0 2002 12 01 31.92 26.7 30 year ISI th 2008 06 11 37.45 34.5 2008 06 11 37.45 32.2 35th year ISI 2012 10 2 41.76 38.9 2012 10 2 41.76 36.5 40th year ISI 2016 09 23 45.73 42.8 2016 09 23 45.73 40.5 Note a: For consistency and simplicity, T is treated as time in years between the unit SIT and the mid-point of a surveillance. The mid-point is treated as the point mid-way between surveillance beginning and ending dates.

Note b: Base T (years since 01 Jan 1980) = Year - 1980 +1 + [(Month - 1 + Day / 30] / 12 (All months considered to have 30 days for fractional year computations.

Note c: T (years since unit SIT) = Event Base T - SIT Base T

Calvert Cliffs Technical Report Part D - Page 75 of 112 Revision 1 09/15/2020 Table 4, Sheet 1 of 4 - Summary of Unit 1 Hoop Tendon Forces Surveillance Year T, Years Since SIT Tendon FM, Measured Force, kip 62H24 674 64H22 695 64H36 679 42H36 689 62H51 666 1 1.3 42H74 652 42H49 643 51H51 643 51H71 665 35H71 659 51H42 617 51H59 617 51H60 584 51H61 587 51H62 608 51H63 590 51H64 610 51H65 582 51H71 637 35H60 627 35H76 657 62H54 626 62H64 654 62H74 653 64H38 630 3 3.0 64H50 636 64H71 619 13H22 703 13H70 640 42H53 623 42H61 618 51H69 595 51H70 597 51H73 580 51H74 581 51H76 613 62H59 627 62H63 630 62H65 640 64H02 648

Calvert Cliffs Technical Report Part D - Page 76 of 112 Revision 1 09/15/2020 Table 4, Sheet 2 of 4 - Summary of Unit 1 Hoop Tendon Forces Surveillance Year T, Years Since SIT Tendon FM, Measured Force, kip 62H70 674 24H55 654 31H50 675 51H45 611 35H65 651 5 4.9 31H02 728 31H01 677 53H04 756 26H04 666 64H40 610 24H37 626 42H51 596 42H52 583 42H53 605 10 11.0 46H04 656 51H72 629 62H54 634 64H50 631 31H23 644 51H13 603 51H15 609 51H16 572 51H17 585 51H18 581 51H20 575 51H21 569 51H22 583 51H23 538 51H24 555 15 17.5 51H25 585 51H26 548 51H27 586 51H28 583 51H29 598 51H30 535 51H31 585 51H32 564 51H33 618 51H71 622 64H24 610

Calvert Cliffs Technical Report Part D - Page 77 of 112 Revision 1 09/15/2020 Table 4, Sheet 3 of 4 - Summary of Unit 1 Hoop Tendon Forces Surveillance Year T, Years Since SIT Tendon FM, Measured Force, kip 35H06 724 42H35 622 42H71 607 51H14 560 62H21 604 20 23.8 62H52 614 62H71 725 64H04 a 648 64H15 630 64H66 647 25 b N/A N/A N/A 13H04 731 13H21 644 13H52 615 24H06 611 24H30 558 24H67 609 62H21 604 62H22 597 62H23 603 62H24 607 62H25 606 62H27 631 30 34.5 62H72 694 62H76 632 64H04a 649 24H29 626 24H34 546 24H35 608 24H36 677 24H63 615 24H64 606 24H65 586 24H66 603 24H68 591 24H69 616

Calvert Cliffs Technical Report Part D - Page 78 of 112 Revision 1 09/15/2020 Table 4, Sheet 4 of 4 - Summary of Unit 1 Hoop Tendon Forces Surveillance Year T, Years Since SIT Tendon FM, Measured Force, kip 35b N/A N/A N/A 31H55 654 35H01 758 35H55 627 42H28 617 42H38 602 51H11 615 40 42.8 51H12 606 51H13 609 51H55 589 64H04 a 666 64H48 629 64H76 627 Note a: Common tendon.

Note b: Beginning with the 25th surveillance year, lift-off forces were measured only in alternate surveillance years in accordance with the schedule defined in IWL-2421.

Calvert Cliffs Technical Report Part D - Page 79 of 112 Revision 1 09/15/2020 Table 5 - Summary of Unit 2 Hoop Tendon Forces Surveillance Year T, Years Since SIT Tendon FM, Measured Force, kip 24H54 638 24H49 640 31H24 596 53H70 612 62H54 662 1 1.0 51H72 671 51H62 632 53H60 648 64H22 632 31H70 642 62H64 627 3 N/A N/A N/A 5 N/A N/A N/A 10 N/A N/A N/A 15 N/A N/A N/A 20 N/A N/A N/A 13H37 592 35H57 632 51H30 626 62H30 606 25 26.7 64H01 654 64H13 638 64H53 630 64H71 648 64H72a 651 30b N/A N/A N/A 31H48 614 35H03 644 42H06 610 42H26 604 42H27 609 42H28 597 42H29 605 35 36.5 42H36 627 51H13 627 51H42 634 62H23 598 64H23 632 64H63 635 64H72a 645 40b N/A N/A N/A Notes a & b: See Table 4 notes.

Calvert Cliffs Technical Report Part D - Page 80 of 112 Revision 1 09/15/2020 Table 6- Summary of Unit 1 Vertical Tendon Forces Surveillance Year T, Years Since SIT Tendon FM, Measured Force, kip 56V13 649 61V10 784 1 1.3 61V25 804 45V06 648 34V16 697 45V04 635 56V06 693 3 3.0 56V30 658 61V23 703 12V12 665 12V31 710 23V08 745 61V01 775 5 4.9 65V28 642 54V14 652 43V08 740 61V02 701 10 11.0 56V14 649 45V25 739 23V08 694 15 17.5 34V06 649 45V08 c 665 34V01 618 45V09 515 20 23.8 61V02 685 61V08 708 61V24 758 25b N/A N/A N/A 23V04 721 23V18 659 34V03 677 30 34.5 34V29 698 45V11 668 56V18a,c 685 35b N/A N/A N/A 12V10 710 12V34 713 23V12 c 696 40 42.8 45V18 680 45V32 776 56V18 a,c 675 Notes a & b: See Table 4 notes.

Note c: Double end stressed; FM listed is top end only measurement.

Calvert Cliffs Technical Report Part D - Page 81 of 112 Revision 1 09/15/2020 Table 7 - Summary of Unit 2 Vertical Tendon Forces Surveillance Year T, Years Since SIT Tendon FM, Measured Force, kip 45V04 712 61V25 669 1 1.0 12V26 690 56V13 685 45V32 661 3 N/A N/A N/A 5 N/A N/A N/A 10 N/A N/A N/A 15 N/A N/A N/A 12V13 555 12V18 707 23V17a 717 34V17 632 20d 21.5 34V34 696 56V01 608 56V05 683 56V11 649 61V21c 617d 12V19 624 23V17a 665 23V34 626 34V20 647 25 26.7 34V33 690 45V20 c 704 56V28 667 61V18c 678 61V19c 671 30 b N/A N/A N/A 12V16 687 12V23 685 23V17a 693 35 36.5 34V01 661 45V15 690 45V24c 698 40b N/A N/A N/A Notes a & b: See Table 4 notes.

Note c: Double end stressed; FM listed is top end only measurement.

Note d: Tendons listed are those initially designated for visual only examination.

Calvert Cliffs Technical Report Part D - Page 82 of 112 Revision 1 09/15/2020 Table 8, Sheet 1 of 2 - Summary of Unit 1 Dome Tendon Forces Surveillance Year T, Years Since SIT Tendon FM, Measured Force, kip 3D35 690 1D34 658 1D18 665 1 1.3 2D17 685 2D35 648 3D18 669 1D27a,c 643 1D51 640 2D26 635 3 3.0 2D50 639 3D17 647 3D50 614 3D43 664 1D40 656 1D24 668 5 4.9 2D21 666 3D14 696 2D45 647 1D27 a 629 10 11.0 2D28 626 3D04 676 1D12 609 15 17.5 2D37 624 3D10 627 1D01 627 2D06 652 20 23.8 2D28 608 2D44 630 3D05 629 25 b N/A N/A N/A

Calvert Cliffs Technical Report Part D - Page 83 of 112 Revision 1 09/15/2020 Table 8, Sheet 2 of 2 - Summary of Unit 1 Dome Tendon Forces Surveillance Year T, Years Since SIT Tendon FM, Measured Force, kip 1D07 639 1D27 a 621 1D44 647 30 34.5 2D51 627 2D57 621 3D20 680 35b N/A N/A N/A 1D27a 629 1D50 631 3D01 650 40 42.8 3D03 640 3D05 650 3D09 654 3D16 672 Notes a & b: See Table 4 notes.

Note c: Re-tensioned in 3rd year; as-found lift-off not a valid common tendon data point

Calvert Cliffs Technical Report Part D - Page 84 of 112 Revision 1 09/15/2020 Table 9 - Summary of Unit 2 Dome Tendon Forces Surveillance Year T, Years Since SIT Tendon FM, Measured Force, kip 2D47 676 2D37 639 3D45 688 1 1.0 1D46 648 3D23 653 1D34 647 3 N/A N/A N/A 5 N/A N/A N/A 10 N/A N/A N/A 15 N/A N/A N/A 20 N/A N/A N/A 1D21 639 1D22 634 1D23 639 25 26.7 1D25 635 3D22 662 3D38 658 3D47 a 659 30b N/A N/A N/A 1D40 647 2D12 681 35 36.5 2D36 656 3D47a 666 3D62 656 40b N/A N/A N/A Notes a & b: See Table 4 notes.

Calvert Cliffs Technical Report Part D - Page 85 of 112 Revision 1 09/15/2020 Table 10, Sheet 1 of 2- Tendons Designated for Visual Only Examination Surveillance Unit 1 Unit 2 Year 1 N/A N/A 31H35 31H55 1D19 42H67 23V17 1D30 35H24 34V18 2D08 35H48 3 N/A 45V17 2D18 64H72 56V22 3D23 51H02 61V10 3D47 51H27 62H24 62H47 13H22 13H77 24H67 1D11 53H05 12V26 1D18 46H49 34V25 2D49 5 N/A 46H60 45V19 2D57 46H72 56V03 3D18 51H20 61V09 3D54 51H40 62H03 62H75 12V31 3D61 42H76 12V32 10 N/A 1D31 51H23 12V33 2D21 62H50 23V21 56V30 1D40 64H33 23V23 15 N/A 2D56 64H72 34V06 3D66 51H37 45V01 13H36 13H37 13H59 1D39 24H64 1D62 24H70 20a N/A 3D32 N/A 35H13 3D47 51H10 3D59 51H48 51H73 64H72

Calvert Cliffs Technical Report Part D - Page 86 of 112 Revision 1 09/15/2020 Table 10, Sheet 2 of 2- Tendons Designated for Visual Only Examination Surveillance Unit 1 Unit 2 Year 13H40 12V15 1D27 13H64 12V27 2D28 13H69 23V08 1D34 24H53 23V16 2D45 24H64 25 23V34 N/A 2D58 35H26 56V18 3D52 51H63 56V23 3D60 62H31 61V02 64H04 61V32 64H65 24H03 24H58 23V04 24H63 23V17 1D16 35H63 34V10 1D31 51H08 45V26 30 N/A 2D16 62H03 56V10 3D47 62H27 56V27 3D49 64H27 61V21 64H64 61V22 64H72 61V29 64H77 31H48 35H02 1D27 35H03 23V05 1D29 35H35 23V14 1D60 42H27 23V31 35 N/A 2D07 42H44 34V15 2D13 51H53 45V20 3D37 62H58 56V18 64H04 64H25 35H25 42H21 12V06 42H48 12V20 2D65 51H32 23V17 2D68 51H46 23V31 40 N/A 3D13 51H53 34V12 3D20 62H77 34V13 3D47 64H10 34V25 64H36 56V03 64H72 Note a: Originally designated Unit 2 sample; sample expanded during the surveillance to include all vertical tendons.

Calvert Cliffs Technical Report Part D - Page 87 of 112 Revision 1 09/15/2020 Table 11a Calvert Cliffs Unit 1 Wire Test Results / Ultimate Tensile Strength Ultimate Tensile Strength, ksi Wire Exam Exam Year T, Yr Tendon Specimen Specimen Specimen Specimen Specimen Mean, Year Mean, ksi 1 2 3 4 5 ksi 64H22 254 255 256 253 N/A 255 62H24 253 254 253 N/A N/A 253 1 1.3 64H22 257 256 256 N/A N/A 256 252 3D35 248 245 245 N/A N/A 246 56V13 247 248 247 N/A N/A 247 51H62 243 250 244 238 N/A 244 51H60 241 243 244 242 N/A 243 3 3.0 51H69 250 254 254 N/A N/A 253 248 3D50 255 256 257 N/A N/A 256 a

56V13 246 245 248 N/A N/A 246 23V08 248 247 247 N/A N/A 247 43V08 246 247 246 N/A N/A 246 5 4.9 3D14 243 243 243 N/A N/A 243 247 23V08 254 254 254 N/A N/A 254 24H37 244 244 242 N/A N/A 243 b

42H52 189 204 N/A N/A N/A 197 b

10 11.0 42H52 257 187 254 204 N/A 226 234 45V25 263 263 261 N/A N/A 262 3D04 254 252 252 N/A N/A 253 1D12 254 254 254 N/A N/A 254 51H22 254 256 254 N/A N/A 255 15 17.5 256 23V08 255 256 255 N/A N/A 255 31H23 261 262 258 N/A N/A 260 34V01 250 250 252 N/A N/A 251 20 23.8 2D44 245 245 246 246 245 245 250 51H14 253 252 253 N/A N/A 253 2D51 263 259 259 N/A N/A 260 c

12V13 277 268 268 N/A N/A 271 30 34.5 269 45V11 269 266 267 N/A N/A 267 62H72 275 279 279 N/A N/A 278 c

35 38.9 12V07 266 266 265 N/A N/A 266 266 3D03 259 260 256 258 N/A 258 64H48 251 250 250 N/A N/A 250 40 42.8 254 12V10 250 251 249 N/A N/A 250 c

56V32 258 257 259 N/A N/A 258 Note a: Results for 10" gage length retest. 100" gage length specimen broke at <240ksi.

Note b: 2 wires tested. Low tensile and elongation due to localized phosphorous inclusion.

Note c: Replacement (2002) vertical tendon.

Calvert Cliffs Technical Report Part D - Page 88 of 112 Revision 1 09/15/2020 Table 11b Calvert Cliffs Unit 2 Wire Test Results / Ultimate Tensile Strength Ultimate Tensile Strength, ksi Wire Exam Exam T, Yr Tendon Specimen Specimen Specimen Specimen Specimen Mean, Year Year 1 2 3 4 5 ksi Mean, ksi 56V13 252 249 255 252 N/A 252 64H22 261 257 259 N/A N/A 259 1 1.0 62H64 253 254 253 253 N/A 253 255 31H24 252 258 253 N/A N/A 254 2D47 256 256 256 N/A N/A 256 3D38 266 277 277 N/A N/A 273 25 26.7 51H30 260 259 261 N/A N/A 260 262 45V20 241 263 257 N/A N/A 254 2D12 264 262 264 N/A N/A 263 62H23 242 243 244 N/A N/A 243 35 36.5 256 12V23 251 252 250 N/A N/A 251 a

56V33 268 268 268 N/A N/A 268 a

40 40.5 34V25 267 265 265 N/A N/A 266 266 Note a: Replacement (2002) vertical tendon.

Calvert Cliffs Technical Report Part D - Page 89 of 112 Revision 1 09/15/2020 Table 12a Calvert Cliffs Unit 1 Wire Test Results / Elongation at Failure Elongation at Failue, % Wire Exam Exam T Tendon Specimen Specimen Specimen Specimen Specimen Mean, Year Year 1 2 3 4 5  % Mean, %

64H22 5.8 5.4 5.1 4.4 N/A 5.2 62H24 4.6 5.1 5.0 N/A N/A 4.9 1 1.3 64H22 4.6 5.2 5.4 N/A N/A 5.1 5.2 3D35 5.9 5.6 5.8 N/A N/A 5.8 56V13 5.1 5.1 5.0 N/A N/A 5.1 51H62 4.4 4.8 4.6 4.6 N/A 4.6 51H60 5.3 5.4 5.0 5.1 N/A 5.2 3 3.0 51H69 4.6 5.1 5.1 N/A N/A 4.9 5.3 3D50 6.0 5.8 5.6 N/A N/A 5.8 a

56V13 6.8 4.6 5.8 N/A N/A 5.7 23V08 6.6 8.5 7.6 N/A N/A 7.6 43V08 5.6 7.8 6.9 N/A N/A 6.8 5 4.9 3D14 7.0 7.1 6.7 N/A N/A 6.9 7.1 23V08 7.3 6.8 7.3 N/A N/A 7.1 24H37 7.5 6.8 7.5 N/A N/A 7.3 b

42H52 1.0 1.0 N/A N/A N/A 1.0 b

4.0 1.0 4.0 1.0 N/A 2.5 10 d

11.0 42H52 2.9 45V25 4.0 4.0 4.0 N/A N/A 4.0 3D04 4.0 4.0 4.0 N/A N/A 4.0 1D12 4.0 4.0 4.0 N/A N/A 4.0 d 51H22 4.0 4.0 4.0 N/A N/A 4.0 15 17.5 4.0 23V08 4.0 4.0 4.0 N/A N/A 4.0 31H23 4.0 4.0 4.0 N/A N/A 4.0 34V01 4.0 4.0 4.0 N/A N/A 4.0 d

20 23.8 2D44 4.0 4.0 4.0 4.0 4.0 4.0 4.0 51H14 4.0 4.0 4.0 N/A N/A 4.0 2D51 5.5 5.2 5.2 N/A N/A 5.3 c

12V13 5.8 6.1 6.1 N/A N/A 6.0 30 34.5 5.4 45V11 5.5 4.6 4.3 N/A N/A 4.8 62H72 5.1 5.9 5.5 N/A N/A 5.5 35 38.9 12V07c 6.7 7.0 6.1 N/A N/A 6.6 6.6 3D03 4.5 5.0 5.5 4.3 N/A 4.8 64H48 6.0 5.5 5.0 N/A N/A 5.5 40 42.8 5.4 12V10 5.0 5.0 4.4 N/A N/A 4.8 c

56V32 6.0 6.3 6.8 N/A N/A 6.4 Note a: Results for 10" gage length retest. 100" gage length specimen broke at <240ksi.

Note b: 2 wires tested. Low tensile and elongation due to localized phosphorous inclusion.

Note c: Replacement (2002) vertical tendon.

Note d: Elongations >4.0% reported as 4.0% (limit of extensometer range).

Calvert Cliffs Technical Report Part D - Page 90 of 112 Revision 1 09/15/2020 Table 12b Calvert Cliffs Unit 2 Wire Test Results / Elongation at Failure Elongation at Failue, % Exam Exam Wire T Tendon Specimen Specimen Specimen Specimen Specimen Year Year Mean, %

1 2 3 4 5 Mean, %

b 56V13 4.0 4.3 4.0 4.0 N/A 4.1 64H22 5.4 5.7 5.9 N/A N/A 5.7 1 1.0 b 5.1 62H64 4.0 4.0 5.2 4.0 N/A 4.3 31H24 5.0 5.4 6.0 N/A N/A 5.5 2D47 6.0 5.4 5.9 N/A N/A 5.8 3D38 4.0 4.3 4.8 N/A N/A 4.4 25 26.7 51H30 4.2 4.3 4.1 N/A N/A 4.2 4.5 45V20 5.0 4.9 4.5 N/A N/A 4.8 2D12 4.8 5.6 5.5 N/A N/A 5.3 62H23 5.0 4.7 5.4 N/A N/A 5.0 35 36.5 5.6 12V23 5.0 6.0 4.5 N/A N/A 5.2 a

56V33 6.0 7.2 7.3 N/A N/A 6.8 a

40 40.5 34V25 6.0 7.0 7.5 N/A N/A 6.8 6.8 Note a: Replacement (2002) vertical tendon.

Note b: Elongations reported as >4.0 shown as 4.0 (i.e., not greater than 4.0) for conservatism.

Calvert Cliffs Technical Report Part D - Page 91 of 112 Revision 1 09/15/2020 Table 13a - Unit 1 Anchorage Area Corrosion Surveillance Year Documented Corrosion 1st Level 1 & 2 only.

Level 3 found on uncoated areas of 51H62 / B5 button heads and anchor head; ascribed to water infiltration. Level 4 (extend not specified) found on test wire 3rd extracted from this tendon.

Else Level 1 & 2 only.

5th Level 1 & 2 only.

Level 3 found at upper end of test wire extracted from 45V25; ascribed to water 10th infiltration.

Else Level 1 & 2 only.

15th Level 1 & 2 only.

Extensive heavy corrosion found on many vertical tendon wires and load bearing components as discussed in 1.3.

Level 3 found on: 62H22 / B2 bearing plate; 62H24 / B6 button heads; 62H52 /

20th B2 anchor head; 62H52 / B6 bearing plate; 62H71 / B6 bearing plate; and, 3D20 (gasket repair tendon) / Shop end bearing plate.

Heavy corrosion found on 64H01 (end not noted) end cap.

Else, only Level 1 & 2 found on hoop and dome tendon components.

25th Level 1 & 2 only.

30th Level 1 & 2 only.

35th Level 1 & 2 only.

Two discontinuous wires extracted from 3D03 (documented in Table 15a) had Level 5 corrosion at the break locations (NCR FN1123-004.

40th Level 3 corrosion found on test wire extracted from 3D03 (NCR FN1123-004).

Else, Level 1 & 2 only.

Calvert Cliffs Technical Report Part D - Page 92 of 112 Revision 1 09/15/2020 Table 13b - Unit 2 Anchorage Area Corrosion Surveillance Year Documented Corrosion Areas of Level 3 found on: 45V32 (end not noteda) anchor head; and on 61V25 (end not noteda) anchor head.

Level 3 found along a ~4 ft length at one end of test wire extracted from 62H64.

1st Pitting (level not specified) found a ~31 ft length at one end of test wire extracted from 56V13.

Else, Level 1 & 2 only.

3rd Level 1 & 2 only.

5th Level 1 & 2 only.

10 th All items noted as SAT (satisfactory). Numerical corrosion level not addressed.

15th All items noted as SAT (satisfactory). Numerical corrosion level not addressed.

Extensive heavy corrosion found on many vertical tendon wires and load bearing components as discussed in 1.3 above.

20 th Level 5 found on 51H10 / B5 bearing plate (NCR FN606-2002).

Else, only Level 1 & 2 found on hoop and dome tendon components.

Level 5 found on 35H19 / B5 bearing plate in the area outside the gasket (NCR 25th FN778B-010).

Else, Level 1 & 2 only.

30t Level 1 & 2 only.

Level 5 found on the 51H13 / B5 bearing plate; NCR N1073-001.

35th Else, Level 1 & 2 only.

40th Level 1 & 2 only.

Note a: Data sheet diagram shows a bottom (field) end anchor head with center hole and no bushing.

Calvert Cliffs Technical Report Part D - Page 93 of 112 Revision 1 09/15/2020 Table 14a - Unit 1 End Anchorage Free Water Surveillance Year Tendon / End Water, description or quantity 1st 2 vertical tendons Reported as traces 3 rd 7 tendons Reported as small amounts 35H65 / Buttress 5 Water reported but quantity not noted 5 th 31H02 / Buttress 3 Reported as some water present 54V14 / Top Reported as some ice on top of tendon 42H51 / Buttress 4 Water reported but quantity not noted 10 th 45V25 / Top Water reported but quantity not noted 45V25 / Bottom Water reported but quantity not noted 51H15 / Buttress 5 Water reported but quantity not noted 51H24 / Buttress 1 Water reported but quantity not noted 15 th 51H27 / Buttress 5 Water reported but quantity not noted 51H28 / Buttress 1 Reported as approximately 1 gallon 51H28 / Buttress 5 Water reported but quantity not noted 20th Original Scope 61V08 / Bottom Reported as 44 oz.

23V28 / Top Reported as 1 oz.

34V13 / Bottom Reported as 20 oz.

20 Expanded th 34V16 / Top Reported as 2 oz.

Scope 56V12 / Top Reported as 1 oz.

3D20 / Shop end Reported as 49 oz. (gasket repair tendon) 94 vertical tendon ends Reported as drops to <1 oz..

13H64 / Buttress 1 Reported as <0.5 oz.

25 th 12V27 / Top Reported as 1 oz.

61V32 / Top Reported as <1 oz.

30th N/A No water reported 1D29 / South end Reported as 20 oz.

35th 34V13 / Bottom Reported as 6 oz.

1D27 / N Reported as 1 oz.

3D03 / N Reported as drops 40th 3D16 / N Reported as 76 oz.

35H01 / Buttress 5 Reported as drops

Calvert Cliffs Technical Report Part D - Page 94 of 112 Revision 1 09/15/2020 Table 14b - Unit 2 End Anchorage Free Water Surveillance Year Tendon / End Water, description or quantity 1D34 / near Buttress 6 Water reported but quantity not noted 51H72 / Buttress 1 Water reported but quantity not noted 45V32 / end not noted Water reported but quantity not noted 45V32 / other end Water reported but quantity not noted 1st 56V13 / Bottom Water reported but quantity not noted 61V25 / Top Water reported but quantity not noted None noted at cap removal; Reported at re-tensioning 61V25 / Bottom During the stressing procedure approx. 2 - 3 gal water poured out of the tendon 51H02 / Buttress 5 Reported as 3% with no explanation 51H02 / Buttress 1 Water reported but quantity not noted 3rd 64H22 / Buttress 6 Water reported but quantity not noted 31H35 / Buttress 1 Reported as 1% in grease 46H49 / Buttress 4 Water reported but quantity not noted 53H5 / Buttress 3 Reported as Yes small amount 62H3 / Buttress 6 Water reported but quantity not noted 5th 62H3 / Buttress 2 Reported as Yes some 45V19 / Bottom Water reported but quantity not noted 61V9 / Top Water reported but quantity not noted 46H72 / Buttress 6 Water reported but quantity not noted 23V21 / Top Water reported but quantity not noted 23V21 / Bottom Water reported but quantity not noted 56V30 / Top Water reported but quantity not noted 62H50 / Buttress 2 Water reported but quantity not noted 10th 62H50 / Buttress 6 Water reported but quantity not noted 1D11 / near Buttress 6 Water reported but quantity not noted 1D11 / near Buttress 4 Water reported but quantity not noted 12V26 / Bottom Water reported but quantity not noted 45V19 / Top Reported as Very little 15th N/A None reported 56V05 / Bottom Reported as 32 oz.

61V21 / Bottom Reported as 32 oz.

20th 56V13 / Top Reported as 2 oz.

72 vertical tendon ends Reported as drops 25th 37H57 / Buttress 3 Reported as 3 oz.

30th 62H03 / Buttress 6 Reported as 10 oz.

35th 35H03 / B5 Reported as 2 oz.

40th 2D68 / West end Reported as 3 oz.

Calvert Cliffs Technical Report Part D - Page 95 of 112 Revision 1 09/15/2020 Table 15a - Unit 1 Missing / Protruding Button Heads Not Previously Documented Surveillance Year Tendon / Anchorage & Observation 1st Nothing noted in reports / on data sheets.

64H71 / B4 - 2 button heads missing.

51H70 / B5 - 1 button head missing.

3rd 2D50 / near B1 - 1 button head missing.

61V23 / Bottom - 1 button head missing.

62H70 / B2 - 1 button head missing.

5th 23V8 / Top & Bottom - 2 discontinuous wires (removed).

24H52 / B2 & B4 - 2 discontinuous wires (removed).

10th 62H54 / B2 - 1 button head missing.

23V08 / Bottom - 1 button head protruding 1/8.

15th 51H22 / B1 - 1 button head protruding 5/16 (shown continuous).

51H23 / B1 - 1 button head protruding 1-3/16 (shown continuous).

(Excluding vertical tendons which are addressed in 1.3) 20th 62H24 / B2 & 6 - 1 missing wire; no wire found so presumed to have been overlooked during initial examination at the time of pre-stressing.

25th Nothing noted in reports / on data sheets.

30th 24H67 / B2 - 1 missing button head; NCR FN1019-001.

35th None 3D03 / North - 2 protruding discontinuous wires broken close to the north 40th anchorage; NCR FN1123-002.

Calvert Cliffs Technical Report Part D - Page 96 of 112 Revision 1 09/15/2020 Table 15b - Unit 2 Missing / Protruding Button Heads Not Previously Documented Surveillance Year Tendon / Anchorage & Observation 1st 31H24 / B1 - 1 discontinuous wire removed.

3rd Nothing noted in reports / on data sheets.

5th Nothing noted in reports / on data sheets.

12V32 / Bottom - 1 discontinuous wire protruding 2-1/2.

10th 12V32 / Top - 1 button head missing.

15th Nothing noted in reports / on data sheets.

(Excluding vertical tendons which are addressed in 1.3) 20th None observed at hoop and dome anchorages.

25th 1D25 / Field end near B4 - 1 missing button head; NCR FN778B-002.

1D31 / end near B1 - 1 missing button head; NCR FN1019-010.

30th 24H03 / B2 - 1 missing button head; NCR FN1019-007.

35th 42H28 / B4 - 1 missing button head; NCR N1072-005.

40th 35H25 / B3; 1 missing button head; NCR FN1123-003.

Calvert Cliffs Technical Report Part D - Page 97 of 112 Revision 1 09/15/2020 Table 16a - Unit 1 CPM Corrosive Ion Concentrations Ion Concentration in Water Extraction, ppm Surveillance Samples Cl NO3 S Year Tested No. 1 ppm Max No. 1 ppm Max No. 1 ppm Max 1 22 1 1.7 2 1.37 0 0.35 3 35 0 0.2 0 0.22 0 0.75 5 23 0 0.1 0 0.89 0 0.20 10 13 2 1.42 0 0.85 8 4.1 15 28 9 2.48 4 1.74 0 <0.5 20 a 39 5 4.99 3 2.72 0 <0.50 25 50 3 1.0 0 <0.50 0 <0.50 30 65 4 1.0 0 <0.50 0 <0.50 35 49 0 <0.50 0 0.52 0 <0.50 40 55 5 2.0 15 <5.0 13 <10.0 Table 16b - Unit 2 CPM Corrosive Ion Concentrations Ion Concentration in Water Extraction, ppm Surveillance Samples Cl NO3 S Year Tested No. 1 ppm Max No. 1 ppm Max No. 1 ppm Max 1 24 0 0.3 0 0.10 5 2.8 3 21 3 3.42 0 0.24 1 2.1 5 Note b - - - - - -

10 11 1 8.69 c 1 4.28 c 0 0.39 15 9 5 1.0 0 <0.5 0 0.9 20 a 48 0 <0.50 21 6.41 0 <0.50 25 57 0 0.50 0 <0.50 0 <0.50 30 47 0 <0.50 0 <0.50 0 <0.50 35 51 0 <0.50 0 <0.50 0 <0.50 40 43 6 2.5 ,d 4 <25 d 4 <25.0d Note a: Results shown only for the originally designated sample of 10 hoop, 5 dome and 5 Unit 1 or 9 Unit 2 vertical tendons.

Note b: Unit 2 5th year CPM lab report not found.

Note c: Both results for the single 1D31 sample.

Note d: The Max Cl , NO3 and S values shown are for a single specimen (42H48 B4) which has a reported water content of 1.9% and a reported base number of 3.70. As the water content and base number are reasonable and as no water was found at either 42H48 anchorage, it is concluded that the concentrations shown represent either sample contamination, testing errors or data transcription errors.

Calvert Cliffs Technical Report Part D - Page 98 of 112 Revision 1 09/15/2020 Table 17a - Unit 1 CPM Sample Neutralization (Base) Number Surveillance Year Samples Tested Max Min 1 22 3.40 0.54 3 35 2.78 0.17 5 23 0.519 0.043 10 13 1.01 <0.11 15 28 43.9 0.0 20 a 39 50.8 <0.50 25 32 Hoop / Dome 26.40 1.51 25 18 Vertical 35 2.02 30 45 Hoop / Dome 59.6 0.55 30 20 Vertical 59.6 4.15 35 31 Hoop / Dome 62.2c / 34.1c <0.50 35 18 Vertical 66.3 37.7 40 39 Hoop / Dome 41.2 <0.500b 40 12 Vertical 68.3 9.61 General note: All vertical tendon CPM, except residual adhering to wires and duct during draining and pneumatic purge, replaced with Visconorust 2090P-4 during / following the 20th year surveillance; vertical tendon sample test results shown separately to enable trend evaluation.

Note a: Results shown only for the originally designated sample of 10 hoop, 5 dome and 5 Unit 1 or 9 Unit 2 vertical tendons.

Note b: Acid number (procedure not identified) determined for 11 samples with base number shown as <0.500. Maximum acid number reported is 3.42.

Note c: The 62.4 base number is for a sample from common tendon 64H04 which was refilled with 2090P-4 CPM during earlier examinations. The 34.1 base number is the maximum for samples other than those from the common hoop and dome tendons.

Calvert Cliffs Technical Report Part D - Page 99 of 112 Revision 1 09/15/2020 Table 17b - Unit 2 CPM Sample Neutralization (Base) Number Surveillance Year Samples Tested Max Min 1 24 1.62 0.26 3 21 0.26 0.03 5 Note c N/A N/A 10 11 2.02 0.03 15 9 25.76 0.0 20 a 48 34.4 <0.50 25 39 Hoop / Dome 21.80 <0.50 25 18 Vertical 16.00 <0.50 30 31 Hoop / Dome 51.2 <0.50 30 17 Vertical 54.0 18.2 35 31 Hoop / Dome 56.2d / 42.9d <0.50 35 20 Vertical 63.1 39.0 40 27 Hoop / Dome 60.8 <0.500b 40 16 Vertical 72.1 16 General note: All vertical tendon CPM, except residual adhering to wires and duct during draining and pneumatic purge, replaced with Visconorust 2090P-4 during / following the 20th year surveillance; vertical tendon sample test results shown separately to enable trend evaluation.

Note a: Results shown only for the originally designated sample of 10 hoop, 5 dome and 5 Unit 1 or 9 Unit 2 vertical tendons.

Note b: Acid number (procedure not identified) determined for 5 samples with base number shown as <0.500. Maximum acid number reported is 2.26.

Note c: Unit 2 5th year CPM lab report not found.

Note d: The 56.2 base number is for a sample from common tendon 64H72 which was refilled with 2090P-4 CPM during earlier examinations. The 42.9 base number is the maximum for samples other than those from the common hoop and dome tendons.

Calvert Cliffs Technical Report Part D - Page 100 of 112 Revision 1 09/15/2020 Table 18a - Unit 1 CPM Sample Water Content Number of Max Water No. of Samples Surveillance Year Samples Content, % 1%

1 22 1.10 1 3 35 28.06 9 5 23 1.9 2 10 13 7.0 5 15 28 8.26 3 20a 30 Hoop / Dome 2.79 2 20a 9 Vertical 6.95 6 25 32 Hoop / Dome 1.2 1 25 18 Vertical 0.97 0 30 45 Hoop / Dome 1.9 4 30 20 Vertical 0.72 0 35 31 Hoop / Dome 5.2 2 35 18 Vertical 1.9 1 40 39 Hoop / Dome 7.1 5 40 12 Vertical 0.94 0 General note: All vertical tendon CPM, except residual adhering to wires and duct during draining and pneumatic purge, replaced with Visconorust 2090P-4 during / following the 20th year surveillance; vertical tendon sample test results shown separately to enable trend evaluation.

Note a: Results shown only for the originally designated sample of 10 hoop, 5 dome and 5 Unit 1 or 9 Unit 2 vertical tendons.

Calvert Cliffs Technical Report Part D - Page 101 of 112 Revision 1 09/15/2020 Table 18b - Unit 2 CPM Sample Water Content Number of Max Water No. of Samples Surveillance Year Samples Content, % 1%

1 24 8.2 3 3 21 0.65 0 5 Note b N/A N/A 10 11 3.6 9 15 9 <0.2 0 20a 30 Hoop / Dome 3.3 2 20a 18 Verticals 11.7 10 25 39 Hoop / Dome 5.30 2 25 18 Vertical 0.62 0 30 31 Hoop / Dome 4.7 1 30 17 Vertical 2.0 1 35 31 Hoop / Dome 2.7 4 35 20 Vertical 0.84 0 40 27 Hoop / Dome 4.4 2 40 16 Vertical 1.1 1 General note: All vertical tendon CPM, except residual adhering to wires and duct during draining and pneumatic purge, replaced with Visconorust 2090P-4 during / following the 20th year surveillance; vertical tendon sample test results shown separately to enable trend evaluation.

Note a: Results shown only for the originally designated sample of 10 hoop, 5 dome and 5 Unit 1 or 9 Unit 2 vertical tendons.

Note b: Unit 2 5th year CPM lab report not found.

Calvert Cliffs Technical Report Part D - Page 102 of 112 Revision 1 09/15/2020 Figure 1 Calvert Cliffs Unit 1 Hoop Tendon Force Trend & LCL / 1 40 Year Surveillance Results 800 Hoop Tendon Mean Force Trend Line LiftOff Force FH (kip) = 644.4 20.0

• Log10 (T) Data Point (Typ) 750 700 F, Tendon Force, kip 650 600 95% LCL on Mean Force 550 Minimum Required Mean Hoop Tendon Force FMinH = 536 kip 500 1 10 100 T, Time Since SIT, Years (Logarithmic Scale)

Calvert Cliffs Technical Report Part D - Page 103 of 112 Revision 1 09/15/2020 Figure 2 Calvert Cliffs Unit 1 Hoop Tendon Force Trend & LCL / 10 40 Year Surveillance Results 800 LiftOff Force Data Point (Typ) 750 700 F, Tendon Force, kip Hoop Tendon Mean Force Trend Line FH (kip) = 529.3 + 60.2

• Log10 (T) 650 600 550 Minimum Required Mean Hoop Tendon Force FMinH = 536 kip 500 1 10 100 T, Time Since SIT, Years (Logarithmic Scale)

Calvert Cliffs Technical Report Part D - Page 104 of 112 Revision 1 09/15/2020 Figure 3 Calvert Cliffs Unit 2 Hoop Tendon Force Trend & LCL / 1 35 Year Surveillance Results 800 750 Hoop Tendon Mean Force Trend Line FH (kip) = 636.8 8.4

• Log10 (T)

LiftOff Force 700 Data Point (Typ)

F, Tendon Force, kip 650 600 95% LCL on Mean Force 550 Minimum Required Mean Hoop Tendon Force FMinH = 536 kip 500 1 10 100 T, Time Since SIT, Years (Logarithmic Scale)

Calvert Cliffs Technical Report Part D - Page 105 of 112 Revision 1 09/15/2020 Figure 4 Calvert Cliffs Unit 1 Vertical Tendon Force Trend & LCL / 1 40 Year Surveillance Results 850 Vertical Tendon Mean Force Trend Line LiftOff Force 800 FV (kip) = 703.0 12.0

• Log10 (T) Data Point (Typ) 750 F, Tendon Force, kip 700 650 95% LCL on Mean Force 600 Minimum Required Mean Vertical Tendon Force FMinV = 622 kip 550 500 1 10 100 T, Time Since SIT, Years (Logarithmic Scale)

Calvert Cliffs Technical Report Part D - Page 106 of 112 Revision 1 09/15/2020 Figure 5 Calvert Cliffs Unit 2 Vertical Tendon Force Trend & LCL / 1 35 Year Surveillance Results 850 LiftOff Force 800 Data Point (Typ) 750 Vertical Tendon Mean Force Trend Line FV (kip) = 679.2 9.6

• Log10 (T)

F, Tendon Force, kip 700 650 95% LCL on Mean Force 600 Minimum Required Mean Vertical Tendon Force FMinV = 622 kip 550 500 1 10 100 T, Time Since SIT, Years (Logarithmic Scale)

Calvert Cliffs Technical Report Part D - Page 107 of 112 Revision 1 09/15/2020 Figure 6 Calvert Cliffs Unit 1 Dome Tendon Force Trend & LCL / 1 40 Year Surveillance Results 800 750 Dome Tendon Mean Force Trend Line FD (kip) = 662.2 16.3

• Log10 (T)

LiftOff Force Data Point (Typ) 700 F, Tendon Force, kip 650 600 95% LCL on Mean Force Minimum Required Mean Dome Tendon Force FMinD = 555 kip 550 500 1 10 100 T, Time Since SIT, Years (Logarithmic Scale)

Calvert Cliffs Technical Report Part D - Page 108 of 112 Revision 1 09/15/2020 Figure 7 Calvert Cliffs Unit 2 Dome Tendon Force Trend & LCL / 1 35 Year Surveillance Results 800 750 Dome Tendon Mean Force Trend Line FD (kip) = 657.8 3.3

• Log10 (T)

LiftOff Force 700 Data Point (Typ)

F, Tendon Force, kip 650 600 95% LCL on Mean Force Minimum Required Mean Dome Tendon Force FMinD = 555 kip 550 500 1 10 100 T, Time Since SIT, Years (Logarithmic Scale)

Calvert Cliffs Technical Report Part D - Page 109 of 112 Revision 1 09/15/2020 Figure 8 Calvert Cliffs Unit 1 Wire Test Results / Ultimate Tensile Strength 300 290 Specimen Test Data Point (Typ.)

280 UTS Trend LIne UTS (ksi) = 247.1 + 6.1

• Log10 (T)

Test Specimen Ultimate Strength, UTS, ksi 270 260 250 240 230 Minimum Required UTS = 240 ksi 220 210 200 1 10 100 Time Since SIT, T, Years (Logarithmic Scale)

Calvert Cliffs Technical Report Part D - Page 110 of 112 Revision 1 09/15/2020 Figure 9 Calvert Cliffs Unit 2 Wire Test Results / Ultimate Tensile Strength 300 Specimen Test Data Point (Typ.)

290 280 Test Specimen Ultimate Strength, UTS, ksi 270 UTS Trend LIne UTS (ksi) = 254.9 + 1.5

• Log10 (T) 260 250 240 230 Minimum Required UTS = 240 ksi 220 210 200 1 10 100 Time Since SIT, T, Years (Logarithmic Scale)

Calvert Cliffs Technical Report Part D - Page 111 of 112 Revision 1 09/15/2020 Figure 10 Calvert Cliffs Unit 1 Wire Test Results / Elongation at Failure 10.0 Elongation Trend LIne 9.0 Elongation (%) = 5.73 0.16

• Log10 (T) 8.0 Specimen Test Data Point (Typ.)

Test Specimen Elongation at Failure, %

7.0 6.0 5.0 4.0 3.0 Minimum Required Elongation = 4 %

2.0 1.0 0.0 1 10 100 T, Time Since SIT, Years (Logarithmic Scale)

Calvert Cliffs Technical Report Part D - Page 112 of 112 Revision 1 09/15/2020 Figure 11 Calvert Cliffs Unit 2 Wire Test Results / Elongation at Failure 10.0 9.0 8.0 Specimen Test Data Point (Typ.)

Elongation Trend LIne Test Specimen Elongation at Failure, %

7.0 Elongation (%) = 4.94 0.07

• Log10 (T) 6.0 5.0 4.0 3.0 Minimum Required Elongation = 4 %

2.0 1.0 0.0 1 10 100 T, Time Since SIT, Years (Logarithmic Scale)