ML25086A205
| ML25086A205 | |
| Person / Time | |
|---|---|
| Site: | Ginna  |
| Issue date: | 03/25/2025 |
| From: | Knowles J Constellation Operating Services, Rochester Gas & Electric Corp |
| To: | Office of Nuclear Reactor Regulation, Document Control Desk |
| References | |
| Download: ML25086A205 (1) | |
Text
Constellation"'
March 25, 2025 U.S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555-0001 R.E. Ginna Nuclear Power Plant Renewed Facility Operating License No. DPR-18 NRC Docket No. 50-244 200 Energy Way Kennett Square, PA 19348 www CaostellatiaoEoergy mm 10 CFR 50.55a
Subject:
Relief Request I6R-11 Concerning the Proposed Alternative for lnservice Inspection of the Containment Post-Tensioning System Components In accordance with 10 CFR 50.55a(z)(1), Constellation Energy Generation, LLC (CEG), hereby requests NRC approval of the following request for the third Containment lnservice Inspection (CISI) interval which is based on the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code,Section XI, 2013 Edition. Specifically, this proposed alternative concerns examination of containment post-tensioning components. Constellation proposes to perform only the visual examination of the accessible containment concrete surfaces and accessible tendon hardware visible without tendon cover removal during the 55th year surveillance. The details of the 1 O CFR 50.55a(z)(1) request are enclosed.
CEG requests your review and approval of this request by March 25, 2026.
There are no regulatory commitments contained in this letter.
If you have any questions concerning this letter, please contact Jesse Brown at 267-533-6355 Respectfully,
'bate: 2025.03.25 12:31 :38
-04'00' Sr. Manager - Licensing Constellation Energy Generation, LLC Attachments: 1) Proposed Alternative for lnservice Inspection of the Containment Post-Tensioning System Components
- 2) Tables and Figures
Relief Request I6R-11 Concerning the Proposed Alternative for I nservice Inspection of the Containment Post-Tensioning System Components March 25, 2025 Page2 cc:
Regional Administrator - NRC Region I NRC Senior Resident Inspector - Ginna Nuclear Power Plant NRC Project Manager - Ginna Nuclear Power Plant A. L. Peterson, NYSERDA
Relief Request I6R-11 Concerning the Proposed Alternative for lnservice Inspection of the Containment Post-Tensioning System Components March 25, 2025 Page 3 bee:
Sr. Vice President, Northeast Operations Site Vice President, Ginna Nuclear Power Plant Vice President, Licensing & Regulatory Affairs and Corp. Security Regulatory Assurance Manager, Ginna Nuclear Power Plant Licensing Manager - KSA Licensing Records - KSA Proposed Alternative in Accordance with 10 CFR 50.55a(z)(1) for lnservice Inspection of the Containment Post-Tensioning System Components Relief Request #ISR-11 Constellation Energy Generation R. E. Ginna Nuclear Power Plant Relief Request I6R-11 Revision O (Page 1 of 10)
- 1.
ASME Code Component(s) Affected:
Code Class:.
Reference:
Examination Category:
Item Number:
==
Description:==
IWL-2420, IWL-2520 L-B L2.10, L2.20, L2.30, L2.40, and L2.50 R. E. Ginna Nuclear Power Plant Concrete Containment Post-Tensioning System
- 2.
Applicable Code Edition and Addenda
The Third Containment lnservice Inspection (CISI) Interval Program is based on the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code,Section XI, 2013 Edition. The Third CISI Interval began on January 1, 2020 and is currently scheduled to end on December 31, 2029.
- 3.
Applicable Code Requirements:
IWL-2420(a) requires that "Unbonded post-tensioning systems shall be examined in accordance with IWL-2520 at 1, 3, and 5 years following the completion of the containment Structural Integrity Test and every 5 years thereafter".
IWL-2420(c) requires that '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".
- 4.
Reason for Request
ASME Section XI requires periodic visual examination of the Reactor Building concrete as well as visual examination and physical testing of any post-tensioning systems. The examinations and testing performed to-date have indicated that the post-tensioning system at Ginna is performing well and is expected to maintain its safety-related function through the end of the current operating license. This relief request proposes to perform only the visual examination of the accessible containment concrete surfaces and accessible tendon hardware visible without tendon cover removal during the 55th year surveillance, scheduled to be completed by September 10, 2026. Physical testing of the post-tensioning system will be performed during the 55th year surveillance only if the results of visual examinations performed in accordance with Table IWL-2500-1, Examination Category L-A indicate a need for such testing as determined by the Responsible Engineer (IWL-2330).
The proposed elimination of the 55th year physical testing of the post-tensioning system will continue to provide an acceptable level of quality and safety based on the performance history of the post-tensioning system, and by implementing physical testing should visual examination results indicate a need for such testing.
Relief Request I6R-11 Revision O (Page 2 of 10)
Although the proposed relief request is based on maintaining an acceptable level of quality and safety, there are additional benefits to eliminating the examinations and tests required during the 55th Year surveillance. Below are specific hazards and undesirable conditions that would be avoided by the proposed alternative:
- 1.
Tendons are located at the top of the containment structure, well above ground level, that requires working at heights and the inherent risks associated with such work.
- 2.
This work involves the use of high-pressure hydraulics.
- 3.
This work requires working with solvents and hot petroleum products and associated fumes.
- 4.
This work involves the use of containers and pressurized lines filled with heated corrosion protection medium (grease).
- 5.
This work is performed in the vicinity of high levels of stored elastic energy (> 1 million foot-pounds) in the tendons. Sudden rotation during force measurement has resulted in high-speed shim ejection at some plants.
- 6.
This work involves handling of heavy loads (test equipment) that exposes both plant equipment and the involved personnel to hazards.
- 7.
Performing examination/testing on a reduced frequency reduces the repetitive loading required for force measurement or overstress tensioning to assess inaccessible lower coupling and rock anchor performance.
- 8.
Eliminating tendon end cap removal would prevent exposing the tendon hardware to environmental conditions, and will reduce environmental waste (e.g.,
solvents, used grease, other consumables).
- 5.
Proposed Alternative and Bases for Use:
5.1 Proposed Alternative In accordance with 10 CFR 50.55a(z)(1), Constellation proposes an alternative to the scheduling requirements of IWL-2420(a) on the basis that the alternative will provide an acceptable level of quality and safety.
The proposed alternative from applicable ASME Section XI, Subsection IWL requirements is as follows:
- 1. In lieu of the requirement of IWL-2420(a) to perform the 55th year examinations of the containment post-tensioning system, Constellation proposes to not perform the 55th year examinations required by IWL-2520, except as noted below.
The examination and physical testing requirements of ASME Section XI, IWL-2520 and Table IWL-2500-1, Examination Category L-B, Item Numbers L2.10, L2.20, L2.30, L2.40, and L2.50 will only be performed during the 55th year physical surveillance if the Responsible Engineer determines that conditions detected during the General or Detailed Visual Examinations performed on containment accessible concrete surfaces and tendon end caps in accordance with Table IWL-2500-1, Examination Category L-A indicate possible degradation of tendon hardware (i.e., anchorheads, wires, or shims). These examinations, if required, Relief Request IGR-11 Revision 0 (Page 3 of 10) shall be completed no later than September 10, 2026. Examples of conditions that could require removal of the tendon end cap and further examination per Item Numbers L2. 10, L2.20, L2.30, L2.40, and L2.50 are as follows:
Evidence of possible damage to the enclosed post-tensioning hardware as evidenced by conditions such as end cap deformation found during external visual examination. Conditions observed by removal of the end cap will be used to determine the extent of additional examinations that may be required in accordance with Item Numbers L2.10, L2.20, L2.30, L2.40, or L2.50.
Active corrosion on a bearing plate or end cap that requires further investigation as determined by the Responsible Engineer in an engineering evaluation.
Evidence of gross leakage of corrosion protection medium.
- 2. Accept the date used for performing post-tensioning system examinations during the First CISI Interval (September 10, 2000) to establish scheduling of future examinations in accordance with IWL-2420, as modified by this request. Since establishing these dates in the First CISI Interval, Ginna has performed the examinations required by IWL-2500 at the frequency required by IWL-2420(a) [every 5 years based on the September 10, 2000 date (+/- 1 year)]. The 55th year examinations are currently scheduled for September 10, 2025 (+/- 1 year).
(Reference 7.3)
Note: 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, Table IWL-2500-1, Examination Category L-A.
5.2 Basis for Proposed Alternative The basis for use of the above proposed alternative is provided below and is supported by the examination history for this plant.
5.2.1 Adjusted Dates for Performing Physical Testing of the Containment Post-tensioning System.
Since September 10, 2000, Ginna has performed the examinations and tests required by Table IWL-2500-1, Examination Category L-B every 5 years based on the September 10, 2000 date(+/- 1 year). Although the dates for performing these examinations are not based on the date that the initial Structural Integrity Test was completed (April 14, 1969), scheduled examinations and tests since 2000 have been performed at a frequency that is consistent with that specified in IWL-2420.
5.2.2 Summary of IWL-2522 Examination Results (Item Number L2.10)
Tendon Prestress Force Measurement Figures shown in Attachment 2 illustrate the containment tendon force measurement history. All 160 of the Ginna vertical tendons have been retensioned since initial installation to address significant loss of tendon prestress that occurred early in the plant life. Most of the Ginna Relief Request I6R-11 Revision O (Page 4 of 10) containment tendons were retensioned in 1980, with the remainder being retensioned in 2005 (with the exception of Tendon V-116). The attached figures demonstrate that tendon prestress forces have remained acceptable since completion of tendon retensioning.
Figure 1 depicts the performance of Tendon V-116 since completion of retensioning in 1969.
Figure 2 depicts the performance of tendons since completion of retensioning in 1980.
Figure 3-1 depicts the performance of tendons since completion of retensioning in 2005, including data from tendons that were subsequently retested since completion of retensioning.
Figure 3-2 depicts the performance of only those tendons that were retensioned in 2005 and subsequently retested since completion of retensioning. Given the limited amount of prestress force measurements obtained subsequent to retensioning in 2005, this figure is considered to provide a better prediction of future tendon force measurements for tendons that were retensioned in 2005.
Following tendon retensioning in 1969, 1980, and 2005, the performance history of the post-tensioning system has been excellent. Figures 1, 2, and 3-2 show that tendon force measurements have remained above the minimum required value (MRV), and that the predicted mean tendon prestress forces for tendons in each retensioning group will remain above the required minimum design prestress force well beyond the end of the current operating license.
Tendon Elongation The post-tensioning system tendons at Ginna were not designed to be periodically detensioned and retensioned during surveillance testing.
During tendon surveillance liftoff testing at Ginna, tendon elongation is measured between the lift-off force and the overstress force (106% of the measured lift-off force). During this process no significant tendon elongation occurs.
The purpose of measuring tendon elongations during inservice examinations is to confirm that unacceptable degradation of the tendons has not occurred during service and that tendons are performing as expected. Although Ginna tendons are not detensioned for performing elongation measurements, the following examinations provide objective evidence that no unacceptable degradation has occurred in the tendons:
Visual examination of anchorage components, including tendon wires and buttonheads on anchorheads.
Tendon wire visual examinations and tension tests performed on untensioned, sacrificial wires removed from selected tendons. Several tendons were initially installed with extra, untensioned wires for the Relief Request I6R-11 Revision O (Page 5 of 10) purpose of removing and performing visual examination and tension testing.
Lift-off force measurements, as well as overstress force measurements at 106% of the measured lift-off force.
Testing of corrosion protection medium (tendon grease) collected from tendons selected for examination.
5.2.3 Summary of IWL-2523 Examination Results (Item Number L2.20)
Tendon Wire Visual Examinations Visual examination of all wires removed from tendons since initial tendon installation have shown no signs of corrosion or physical damage.
Tendon Wire Tension Testing Results of tension tests on all wires removed from tendons have met applicable acceptance standards, including material specification requirements for ultimate tensile strength (2: 240 ksi) and elongation at failure (2: 4%).
5.2.4 Summary of IWL-2524 Examination Results (Item Number L2.30)
Tendon Anchorage Area Concrete Examinations Cracking of concrete adjacent to bearing plates has been observed at several tendon end anchorages. These conditions have all been evaluated as acceptable, are considered typical in structures of this age, and do not represent evidence of abnormal degradation of the containment or its post-tensioning system. Maintenance has been performed, when necessary, to restore protective coatings to prevent further cracking that could result from freeze-thaw conditions.
Tendon Anchorage Hardware and Bearing Plate Examinations Visual examinations of tendon anchorage hardware (anchorheads, shims, buttonheads, and bearing plates) have met the applicable acceptance standards, except as noted below. Cracking has not been detected in any tendon anchorage component (anchorhead, shims, bearing plates).
Level Ill corrosion (visible oxidation with pitting) has been observed on bearing plates of a majority of tendons. These conditions have been detected at the base of the tendon end caps, primarily in areas beneath tendon end cap gasketing where the gasket is compressed against the bearing plate. The low-durometer gaskets used to seal grease from leaking at the grease can-to-bearing plate interference have maintained their function at the locations exhibiting corrosion/pitting. These conditions have not resulted in degradation to tendon anchorage components and have not had an adverse effect on the performance of the containment post-tensioning system.
No broken, missing, or protruding wires have been detected in any tendon, except for wires in Tendon V-075, which were damaged during surveillance activities in 1983.
Relief Request I6R-11 Revision O (Page 6 of 10) 5.2.5 Summary of IWL-2525 Examination Results (Item Numbers L2.40 and L2.50)
Tendon Corrosion Protection Medium (CPM) Analyses Results of tendon corrosion protection medium tests have met acceptance standards during all examinations.
Tendon Free Water Collection and Analysis Free water has only been detected in the following tendons:
V-026 (approx. 2 ounces)
V-087 (very small quantity attributed to condensation within the tendon cap)
V-160 (approx. 8 ounces)
CPM coverage of tendon anchorheads, wires, or shims in these tendons adequately protected the tendon anchorage components from corrosion.
5.2.6 Summary of IWL-2526 Requirements (Item Number L2.40)
Due to the design of the Ginna tendons, which are attached to rock anchors at the bottom ends, tensioning of tendons from the bottom ends is not possible, and CPM is not drained or removed from tendons during surveillances (except at the top end in the vicinity of the anchorage components). For this reason, only a relatively small quantity of CPM is removed and replaced during surveillances (approx. < 5 gallons), and measurement of grease volumes removed/replaced is not normally performed. Following completion of tendon examinations and tests, tendon end caps are refilled to ensure adequate coverage of tendon hardware components and wires.
Unacceptable anchorage or tendon conditions resulting from inadequate grease coverage have not been detected.
5.2. 7 Concrete Visual Examinations (Item Numbers L 1.11, L 1.12)
Examinations of accessible exterior surfaces of the containment concrete in accordance with Table IWL-2500-1, Examination Category L-A have been performed on accessible containment concrete surfaces since the requirements of Subsection IWL were initially imposed in the late 1990s.
These examinations have detected some areas where minor concrete degradation has been observed. No significant indications requiring repair have been identified, although corrective maintenance has been recommended to address minor conditions.
Detailed visual examination of suspect areas of accessible concrete surfaces, including surfaces adjacent to tendon anchorage areas shall continue to be performed in accordance with IWL-2511, IWL-2310(b), and Table IWL-2500-1, Examination Category L-A, Item Number L 1.12 when suspect surface areas are detected during the Examination Category L-A, Item Number L 1.11 examinations.
Relief Request IGR-11 Revision 0 (Page 7 of 10) 5.2.8 Summary of Justification for the Proposed Alternative Tendon Prestressing Forces Following tendon retensioning in 1969, 1980, and 2005, the performance history of the post-tensioning system has been excellent.
Measured tendon prestressing forces for tendons retensioned in 1980 and 2005 (and V-116 in 1969) have met acceptance standards during all surveillances conducted since completing retensioning activities.
Tendon mean prestressing forces are projected to remain above the minimum required value (MRV) well beyond the end of the current plant operating license.
Overstress Testing of Tendons During each tendon surveillance, an overstress test (at 106% of the measured lift-off force) is performed on each physical surveillance tendon to verify the ability of the tendon (and embedded rock anchors at the bottom of the tendon) to sustain the load applied during the design basis accident. These overstress tests are performed because the bottom ends of the tendons are anchored to rock and are not accessible to perform lift-off force measurement.
Tendon Wire Visual Examinations and Tension Tests Tendon wire visual examinations have not detected unacceptable conditions in wires, and tendon wire tensile testing results have met applicable acceptance standards.
Tendon Anchorage Visual Examinations Tendon anchorage hardware and bearing plate examinations have met applicable acceptance standards or have been evaluated to confirm continued acceptability. Corrosion has been identified on surfaces of bearing plates, adjacent to tendon caps. Corrective maintenance (recoating) has been performed, when necessary, to prevent further corrosion of the affected bearing plates.
Apart from Tendon V-075, significant damage or degradation has not been detected in any tendon. Damage to Tendon V-075 was the result of insufficient tensioning rod engagement during force measurement in 1983.
Tendon Corrosion Protection Medium (CPM) Leakage Tendon CPM leakage has been observed at Ginna. Only a few instances of CPM leakage have been detected at tendon end caps during IWL examinations.
Excessive CPM leakage (low grease volume) has been detected in Tendons V-009, V-045, V-050, V-066, V-071, V-081, and V-155 during previous examinations. Ginna now performs preventative maintenance to inspect tendons for CPM leakage and has inspected these seven (7)
Relief Request I6R-11 Revision O (Page 8 of 10) tendons plus sixteen (16) randomly selected tendons annually since 2005. During these inspections, CPM is added as necessary to ensure that CPM coverage remains acceptable. These inspections, performed in addition to examinations required by IWL-2524 and IWL-2525, provide additional assurance that anchorage hardware and wires remain adequately coated with CPM to protect against potential corrosion.
During visual examinations, anchorage components and wires have remained sufficiently coated with CPM to protect the components from corrosion, regardless of the level of CPM observed within the tendon end cap.
Free Water and CPM Testing Free water has been detected in only a few tendons, with a maximum volume of 8 oz. recorded for a single tendon. Other tendons with free water had amounts less than 2 oz. No evidence of tendon degradation has been detected as a result of the presence of free water.
Tendon CPM testing results have met applicable acceptance standards.
Tendon Anchorage Area Concrete Examinations Tendon anchorage area concrete examinations have been acceptable.
Concrete Visual Examinations During the Third Containment lnservice Inspection Interval, containment concrete surface areas shall be examined in accordance with the requirements of the ASME Code,Section XI, 2013 Edition, Paragraph IWL-2511 and Table IWL-2500-1, Examination Category L-A, Item Number L 1.11 during the 55th Year examinations. These surface areas, including accessible anchorage areas of tendons, shall be examined for evidence of conditions indicating damage or degradation, such as described in ACI 201.1 R and ACI 349.3R.
Concrete surface areas are also examined for evidence of corrosion protection medium leakage. Tendon end caps are examined for evidence of deformation, and end caps are required to be removed if these conditions are detected [Ref. IWL-2511 (c)].
During the Third Containment lnservice Inspection Interval, detailed visual examination of suspect areas of accessible concrete surfaces, including surfaces adjacent to tendon anchorage areas shall be performed in accordance with the requirements of the ASME Code,Section XI, 2013 Edition, Paragraphs IWL-2511, IWL-2310(b), and Table IWL-2500-1, Examination Category L-A, Item Number L1.12 during the 55th Year examinations, if suspect conditions are detected during the Examination Category L-A, Item Number L 1.11 examinations.
Tendons Selected for Examination Relief Request IGR-11 Revision O (Page 9 of 10)
Ginna has examined at least 14 tendons during each previous tendon surveillance, exceeding the maximum number required by Table IWL-2521-1. Because the acceptance standards of IWL-3221.1 have been met for at least the previous 3 surveillances, a maximum of 5 tendons would be required by Table IWL-2521-1. Examination of the additional 9 tendons during each surveillance provides additional assurance that the post-tensioning system is performing acceptably. As of the most recent surveillance (completed in 2021 ), 60% of the 160 containment tendons have been tested subsequent to completion of tendon retensioning in 1980 and 2005.
5.2.9 Conclusion The results of the inservice examinations conducted at Ginna have demonstrated that the containment post-tensioning system is continuing to perform its intended function and can be expected to do so until well past the September 18, 2029 expiration of the current plant operating license. Visual examinations of concrete surface areas to be performed in accordance with ASME Section XI, Table IWL-2500-1, Examination Category L-A, Item Numbers L 1.11 and L 1.12 during the 55th Year surveillance are sufficient to determine if any physical testing or examinations in accordance with Table IWL-2500-1, Examination Category L-B will be required during the 55th Year surveillance. Preventative maintenance (performed annually since 2009) will continue to monitor tendons for CPM coverage and level to ensure that tendons are adequately protected from corrosion. For these reasons, Constellation requests authorization to use the proposed alternative pursuant to 10 CFR 50.55a(z)(1) on the basis that the proposed alternative provides an acceptable level of quality and safety.
- 6.
Duration of Proposed Alternatives:
The proposed alternative is requested for use during the Ginna Third Containment lnservice Inspection Interval.
- 7.
References:
7.1 ASME Boiler and Pressure Vessel Code,Section XI, 2013 Edition 7.2 R. E. Ginna Nuclear Power Plant ISi Program Plan, Sixth lnservice Inspection Interval, Document #ER-Gl-330-1001 7.3 ADAMS Accession Number ML993280389. NRC Final Rule with details regarding IWE
/ IWL Program implementation in section 2.5.2.1.
- 8.
Precedents:
8.1 ADAMS Accession Number ML23353A077. NRC approval dated January 16, 2024.
Wolf Creek Generating Station, Unit 1 - "10 CFR 50.55a Request Number Cl3R-01 for the Third Containment lnservice Inspection Program Interval for Proposed Alternative Frequency to Containment Unbonded Post-Tensioning System Components", dated May 17, 2023 (ML23137A328) 8.2 ADAMS Accession Number ML22124A241. NRC approval dated May 12, 2022. Palo Relief Request I6R-11 Revision 0 (Page 10 of 10)
Verde Nuclear Generating Station Units 1, 2, and 3, Relief Request 67 - "Request for Alternative Frequency to Containment Unbonded Post-Tensioning System lnservice Inspection", dated July 29, 2021 (ML21210A300) 8.3 ADAMS Accession Number ML20287A471. NRC approval dated October 20, 2020.
Millstone Power Station, Unit 2, "Proposed Alternative Request RR-05-05, Containment Unbonded Post-Tensioning System lnservice Inspection Requirements", dated December 17, 2019 (ML193528898).
8.4 ADAMS Accession Number ML19182A077. NRC approval dated July 11, 2019.
Vogtle Electric Generating Plant, Units 1 and 2, "Proposed ISi Alternative VEGP-ISI-ALT-19-01 for Tendon lnservice Inspection Extension", dated February 18, 2019 (ML19049A017).
8.5 ADAMS Accession Number ML19226A023. NRC approval dated September 19, 2019. Three Mile Island Nuclear Station, Unit 1, "Submittal of Relief Request RR-18-01 Concerning Containment Unbonded Post-Tensioning System lnservice Inspection Requirements", dated October 16, 2018 (ML18289A363).
8.6 ADAMS Accession Number ML21134A006. NRC approval dated August 3, 2021.
Braidwood Station, Units 1 and 2 (Relief Request I4R-11) and Byron Station, Unit Nos.
1 and 2 (Relief Request I4R-18), Alternative to Containment Unbonded Post-Tensioning System lnservice Inspection Requirements, dated July 24, 2020 (ML20206L135).
Tables and Figures Relief Request #16R-11 Tables and Figures Relief Request I6R-11 (Page 1 of 12)
Table1 / Figure 1 R.E. Ginna Vertical Tendon V-116 Force Data (Retensioned 1969)
Structural Integrity Test (S.I.T.) Date: 04/14/1969 Mi.
V =
Retensioning Su rveilla nee Average Measured Time Since Tendon Date Date Force ki s Retensionin V-116 5/1/1969 5/1/1969 757 0.00 V-116 5/1/1969 7/18/1981 690 12.21 V-116 5/1/1969 11/16/1983 693 14.54 V-116 5/1/1969 7/10/1990 685 21.19 V-116 5/1/1969 9/21/2005 682 36.39 V-116 5/1/1969 4/30/2021 683 52.00 Figure 1 Ginna Tendon V-116 (Retensioned in 1969) 7W + 757 I '
740 I
~
~
B_ 720
~
6 I
4 -693 t
Years j
700
- '\
Tendon forceTrendllne \
~ 680 I
690
- -a.- - - - - *- G_§J __ _
~
\_ 685
. - 682 SI i 660
~
640 620 0
10 Minimum Required Prestress Force= 636 kips 20 30 40 so 60 70 80 Years from 1969 Retensionlng Note: Tendon V-116 was retensioned in 1969, and the data for Tendon V-116 shows that the rate of prestress loss has reduced significantly over time, with very little prestress loss occurring in Tendon V-116 over the last 40 years of plant operation.
Tendon V-001 V-002 V-U03 V-004 V-~
V-006 V--007 V-008 V-009 V-010 V-011 V-012 V-013 V-014 V-015 V-016 V-017 Y.-018 V-019 V-020 V-021 V-022 V-023 V-024 V~Q25 V-026 V-027 V-028 V-029 V-030 V-031 V-040 V-041 V-042 V-043 V-044 V-045 y.,.045 V-047 V-04-8 V-049 V-050 V-051.
Tables and Figures Relief Request 16R-11 (Page 2 of 12)
Table 2 Gfnna Vertical Tendon Force Data (Tendons Retensioned 1980)
Structurallntegrity Test (S.I.T.) Date: 04/14/1969 Tendon Minimum Requtred Prestress Force (MRV) = 636 kips Retensiooing surveillance Average Measured Time Since Retensioning Date Date Force {kips)
{Years}
6/18/1980 6/1811980 773 o_oo 6/18!1980 6/18/1980 758 o_oo 6/18/1980 6/18i19BO 769 o_oo 6/18/1980 6/18/1980 765 o_oo 6/18/1980 6/18/1980 765 0.00 6118/1980 6/18/1980 769 o_oo 6/18/1980 6116/1980 758 o_oo 6.118/1980 6/18/1980 769 o_oo 6/1811980 6/18/1980 758 0.00 6.118/1980 6/18/1980 758 0.00 6/18/1980 6/18/1980 761 0.00 6/18/1980 6/18/1980 758 0.00 6/18/1980 6/18/1980 761 0.00 6/18/1980 6/18/1980 758 0.00 6{18/1980 6/18/.1980 769 0.00 611.8/1980 6118/1980 758 0.00 6/18/1980 6/18/1980 776 0.00.
6.118/1980 6/18/1980 773 0.00 6/18/1980 6/18/1980 761 0.00 6.118/1980 6/18/1980 773 0.00 6/18/1980 6/18/1980 765 OJlO 6118/1980 6/18/1980 754 0.00 6/18/1980 6/18/1980 750 0.00 6118/1980 6/18/1980 761 0.00 61tB/19aD 6/18/1980 761 0.00 6/18/1980 6/18/1980 769 0.00 6/1811980 6/18/1980 769 0.. 00 6{18/1980 6{16/1980 765 0.00 6/1811980 6/18/1980 769 o~oo 6/18/1980 6/18/1980 761 0.00 6/18/1980 6/18/1980 754 o_oo 6/1811980 6118/1980 765 o_oo 6/18/1980 6118/1980 769 0.00 6/18/1980 6/18/1980 758 0.00 6/18/1980 6/18/1980 761 Q_(}O 6/18/1980 6/18/1980 750 0.00 6/18/1980 6/18/1980 765 0.00 6/18/1980 6/18/1980 769 0.00 6118/1980 6/1811980 758 0.00 6/18/1980 6/18/1980 746 0.00 6118/1980 6/18/1980 754 0.00 6118/1980 6118/1980 765 OJXl 6/1811980 6/18/1980 765 0.00
Tendon V-052 V-053 V-054 V--055 V-057 V-058 V-059 V-060 V-061 V-062 V-063 V-064 V-065 V-066 V-067 V-068 V-069 V-070 V-071 V-072 V-074 V-075 V-076 V-077 V-078 V-079 V-080 V-081 V-082 V-083 V-064 V-085 V-086 V-087 V-088 V-089 V-090 V-091 V-092 V-093 V--094 Tables and Figures Relief Request I6R-11 (Page 3 of 12)
Table 2 Ginna Vertical Tendon Force Data {Tendons Retensioned 1980)
Structural Integrity Test. (S.I. T,) Date: 04114/1969 Tendon Minimllm Required Prestress Force (MRV) = 636 kips Retensfoning Surveillance Average Measured Time Since Retensioning Date Da~
Force {kips)
(Years)
'6/'18/1980 6/1811980 758 0.00 6/18/1980 6/18/1980 761 0.00 6118/1980 6/1811980 761 0.00 6/18/1980 6/18/1980 754 0.00 6'1811980 6/.18/1980 769 0,00
'6/18/1980 6118/1980 754 0.00 6118/1980 6/16/1980 761 0.00
'6118/1980 6/18/1980 761 0.00 6/18/1980 6/18/1980 769 0,00 6/18/1980 6/16/1980 773 Q_QO 61'1811980 6/18/1980 769 0.00 6/18/1980 6/18/1960 761 0.00
,6/f8/1980 6/18/1980 768 0,00 6/18/1980 6/18/1980 761 0,00 6/1811980 6/18/1980 753 0.00 6/18/1980 6/18/1980 761 0.00 6118/1980 6/181'1980 761 0,00 6.118/1980 6/18/1980 761 0.00 6/18/1980 6118/1980 768 0,00 6/18/1980 6/18/1980 765 0.00 6118/1980 6/18/1980 746 0,00 6'18/1980 6/18/1980 761 0.00 6/1811980 6/18/1980 754 0.00 6/18/1980 6/18/1980 761 0,00 6118/1980 6/18/1980 753 0.00 6/18/1980 6/18/1980 746 0.00 6/1811980 6/18/1980 768 0.00 6/TS/1980 6118/1980 768 0.00 6'18/1980 6/18/1980 753 0.00 6/18/1980 6/18/1980 753 0.00 6/18/1980 6/18/1980 753 0.00 snB/1980 6/18/1980 761 0.00 6'18/1980 6/16.11980 746 0.00 6/18/1980 6/113/1980 768 0.00 6/18/1980 6/18/1980 751 0,00 6'18/1980 6118/1980 1n 0,00 6/18/1980 6/18/1980 7fil 0.00 6118/1980 6/18/1980 750 0.00 6/18/'1980 6/18/1980 772 0.00 61'18/1980 6/18/1980 761 0.00 6118/1980 6/18/19.80 761 0.00
Tendon V--wo V-096 V-097 V--098 V-099 V-100.
V-101 V-102 V-103 V-104 V-105 V-106 V-107 V-108 V-109 V-110 V-*123 V-124 V-125 V-127 V-128 V-129 V-130 V-131 V-132 V-133 V-134 V-135 V-1.Jo V-'137 V-138 V-13.9 V-140 V-1:41 V-142 V-143 V-144 V-145 V-146 V-147 Tables and Figures Relief Request 16R-11 (Page 4 of 12)
Table 2 Ginna Vertical Tendon Force Data (Tendons Retensioned 1980) structural fntegrtty Test (SJ.T.) Date: 0411411969 Tendon Minimum Requited Prestress Force {MRV) = 636 'ktps Retensioning survemance Average Measured Time Since Retensioning Date Date Force {~ips)
(Years) 6f18/1YOO 6116/1980 772 n.oo 6/18/1980 6/16/1980 761 0.00 6/18/1980 6/18/1980 753 0.00 6/18/1980 6/18/1980 746 0.00 6/18/1980 6/18/1980 746 0.00 6'16/1980 6/18/1980 753 0.. 00 6/1811980 6/18/1980 746 0.00 6/18/1980 6/18/1980 768 0.00 6/18/1980 6/18/1980 757 0.00 6/18/198(1 6/18/1980 753 tlOO 6/18/1980 6/18/1980 746 0.00 6/18/1980 6/18/1980 746 0.00 6/18/1980 6/18/1980 761 0.00 6/1811980 6/18/1980 753 0.00 6/18/1980 6/18/1980 750 0.00 6/1811980 6/18/1980 753 0.00 6/18/1980 6/18/1980 757 0.00 6/18/1980 6/18/1980 753 0.00 6/18/1980 6/18/1980 768 0.00 6/18/1980 6/18/1980 761 0.00 6/18/1980 6/1811980 753 0.00 6/18/1980 6/18/1980 753 0.00 6/18/1980 6/18/1980 746 0.00 6'18/1980 6118/1980 768 0.00 6/18/1980 6/18/1980 768 0.00 6/1811980 6/18/1980 757 0,00 6/18/1980 6/18/1980 753 0.00 6118/1980 6/18/1980 753 0.00 6/18/1980 6/18/1980 757 0.00 6118/1980 6/18/1980 753 0.00 6/18/1980 6/18/1980 753 0.00 6118/1980 6/18/1980 761 0.00 611B/1980 6/18/1980 765 0.00 6/18/1980 6/18/1980 753 0.00 6/18/1980 6/18/1980 746 0.00 6/1811980 6/18/1980 753 o_oo 6/18/1980 6/18/1980 761 0.00 6/1811980 6/18/1980 768 0.00 6/18/1980 6/18/1980 753 0.00 6/1811980 6118/1980 746 0.00
Tendon V-148 V-149 V-150 V-151 V-152 V-153 V-154 V-155 V-156 V-157 V-158 V-159 V-160 V-001 V-002 V-003 V-004 V-004 V-005 V-005 V-006 V-007 V-008 V-009 V~10 V-011 V-01-1 V-013 V-013 V-014 V-015 V-016 V-016 V-017 V-017 V-018 V-0'18 V-019 V-021 V-021 V-021 Tables and Figures Relief Request ISR-11 (Page 5 of 12)
Table 2 Ginna Vertical Tendon Force Data (Tendons Retensioned 1980)
Structural Integrity Test (S.L T.} Date: 04/1411969 Tendon Minimum.Required Prestress.Force (M.RV) = 636 kips Retensioning Surveillance Average Measured Time Since Retensioning Date Date Force (kips)
{Years) 6/18/1980 6/16/1980 76T 0.00 6118/1980 6/18/1980 768 0.00 6/*18/1980 6/18/1980 761 0.00 6/18/1980 6/18/1980 761 0.00 6/18/1980 6/16/1980 758 0.00 6/1811980 6/16/1980 761 0.00 6118/1980 6/18/1980 761 0.00 6/18/1980 6/18/1980 754 0.00 6/18/1980 6/18/1980 761 0.00 6/18/1980 6/18/1980 758 0.00 6118(1980 6/16/1980 768 0.00 6/18/1980 6/18/1980 761 0.00 6/18/1980 6/18/1980 761
-0.00 6/18/1980 B/2311995 729 15.18 6/W/1980 12113/2000 685 20.49 6118/1980 4113/2011 708 30.82 6/18/1980 719/1990 712 10.06 6118/1980 12113/2000 698 20.49 6/18/1980 9113/2005 687 25.24 6/18/1980 6/24/2010 697 30.02 6/18/1980 6/2412010 697 30.02 6/18/1980 B/23/1995 694 15:18 6/19/1980 6/2412010 731 30.01 6/18/1980 12/13/2000 696 20.49 6/18/1980 12/13J2000 699 20.49 6/18/1980 4/13/2011 702 30.82 6tl8/1980 5/18/2021 702 40.91 6118/1980 7/18/1981 730 1.08 6/1.8/1980 7125/1983 730 3.10 6/18/1980 9/1412005 699 25.24 6/18/1980 6/2412010 701 30.02 6/18/1980 9/1412005 711 25.24 6/18/1980 4/11/2016 707 35.81 6118/1980 7/18/1981 727 1.08 6118/1980 8/31/1985 7'17 520 6/18/1980 7/25/1983 727 3.10 6/18/1980 8/31/1985 705 520 6/18/1980 4/13/2011 717 30.82 6118/1980 7/18/198*1 725 1.08 6/18/1980 8/3'1/1985 723 5.20 6/18/1980 7/9/1990 712 10.06
Tendon V-022 v~023 V-025 V-025 V-D.26 V-027 V.:027 V-029 V-030 V--040 V-040 v~OAo V-041 V-OA2 V-042 V-043 V-043 V-048 V-051 V-051 V-D51 V-052 V-053 V-053 V-053 v~o54 V-057 V-O58 V-059 V-060 V-060 V-060 V-062 V--062 V-063 V-063 V-063 V--065 v~ooo V-067 V-'070 Tables and Figures Relief Request IGR-11 (Page 6 of 12)
Table 2 Ginna Vertical Tencion Force Data {Tendons Retensioned 1980)
Structural Integrity Test (SJ.T,) Date: 04/14/1969
,en don Minimum Required Prestress Force- {MRV) = 636 kips.
Retensioning Surveillance Average Measured Time Since Retens1oning Date Date Force (kips)
(Years) 6118/1~
8123/1995 684-15.18 6/18/1980 4/11/2016 685 35.81 6118/1980 7/611990 711 10.05 61't8/198.0 4/11/2016 690 35.81
!:,/18/1980 51"1812021 690 40,91 6/18/1980 6/24/2010 716 30.02 61t8/1980 4/13/201-1 694 30.82 6/1-8/198fJ
.5/19/202*1 697 40.92 6118/1980 9/14/2005 696 25.24 6/18/1980 7rl1/1983 731 3.10 6/18/1980 8/31/1985 724 5.20 6118/1980 716/1990 716 10.05 6118/1980 515/202*1 692 40.86 6118/1980 8/23/1995 677 15.18 fi/"t8/1980 6/24/2010 686 30.02 61t8/1980 8i24/1995 700 15.18 6/18/1980 4113/2011 693 30,82 6/18/1980 417/2016 680 35.80 6'18/1980 7118/1981 no 1.08 6/18/1980 7/27/1983 709 10 6l18/1980 4/13/2011 679 30.82 6118/1.980 417/2016 678 35.80 6'*f8/1980 711811981 734 1..08 6(18/1980 7/27/1983 731 3.10 6118/1980 7/6/1990 715 10.05 6/f8l1980 5/19/2021 697 40.92 6/18/1980 12114/2000 709 20.49 6/18/1980 9113/2005 681 25.24 6/18/1980 4/13/2011 702 30.82 6/18/1980 7/27/1983 711 3."10 6/18/1980 8/31/1985 702.
5.20 6/1'8/1980 6/2412010 682 30.02 6"18/1980 7/18/1981 716 1.08 6/18/1980 7/27/1983 715 3-10 6118/1980 7/16/1981 7'22 1.08 6'18/1980 8/31/'1985 713' 5.20 6118/1980 417/2016 690 35.80 6/18/1980 5/19/2021 690
-40~92 6/t8/1980 12114/2000 691 20.49 6lt8/1980 4/13/2011 693 30.82 6/18/1980 4/6/2016 685 35.80
Tendon V-071 V-071 V..fJ72 V-074 V-074 V-074 V-074 V-076 V-076 V-076 V-076 V-076 V-Oll V-OTT V-077 v:,oa1 V-081 V-083 V-084 V-:084 V-084 V--085 V-087 V-087 V-090 V-091 V-093 V-093 V-093 V-094 V-099 V-099 V-100 V-101 V-103 V-105 V-105 V-107 V-108 V-110 V-123 V-123 Tables and Figures Relief Request IGR-11 (Page 7 of 12)
Table 2 GiMa Vertical Tendon Force Data. (Tendons Retensioned 1980)
Structural Integrity Test (S.t.T.) Date: 04/1411969 Tendon Minimum Required Prestress Force {MRV) = 636 kips Retensioning surveillance Average Measured Time Since Retensioning Date Date Force {kips}
{Years) 6/'18/1980 8/31/1985 705 5.20 6/'18/1980 9/13'2005 695 25.24 6(18/1980 9/13!2005 695 25.24 6/'18/1980 7/18/1.981 731
't.08 6/18/1980 8/31/1985 7'10 5.20 6'18/1980 9127.12005 690 25.28 6118/1980 4/13/2011 685
.30.82 6'18/1980 7/18/1981 713 1.08 6'18/1980 11/17/1983 700 3.41 6'18/1980 8/31/1985 703 5.20 6/18/1980 7/511990
.698 10.05 6.118/1980 4/1;3f20l1 672 30.82 6/1811980 8.131/1985 723 5.20 6'18/1980 12/11/2000 701 20.48 6/1811980 5/19J2021 700 40.92 6'1811980 8/24/1995 7D1 15.18 6/18/1980 416/2016 690 35.80 6/18/1980 4113/2011 694 30.82 6118/1980 7/18/1981 714
'f.08 6/18/1980 8/31/1985 710 5~20 6/18/1980 7/5/1990 703 10.05 6/18/1980 6/24/2010 706 30.02 6'18/1980 8/24/1995 718
- J5.W 6118/1980*
416'.2016 697 35.80 6/18/1980 6/1412021 697 40.99 6'18/1980 4/13/2011 687 30.82 6/18/1980 7/18/1981 713.
t.08 6'18/1980 7/2711983 706 3.10 6'18/1980
- 6/23/2010 697 30.01 6/1811980 6/2312010 708 30.01 6118/1980 8124/1995 707 1.5.18 6118/1980 4/13/2011 693 30.62 6'18/1980 6121r.mm 701 30.m 6118/1980 7/5/1990 697 10.05 6/18/1980 8/3111985 703 5.20 6.'18/1980 7/10/1990 700 10.06 6118/1980 12/612000 695 20.47 6/18/1980 4113/2011 690 30Ji2 6/18/1980 8122/1995 714 15.18 6/18/1980 12/612000 716 2R47 6/18/1980 8/22/1995 699 15.18 6/18/1980 4113/2011 685 30c82
Tendon V-125 V-125 V-125 V-128 V-128 V-128 V-129 V-129 V~129 V-131 V-132 V-133 V-133 V-134 V-136 V-'139 V-'I42 V-143 V-145 V-147 V-147 V-151 V-*152 V-155 V-155 v~155 V-155 V-156 V-156 V-157 V-159 V-160 V-160 V-160 Tables and Figures Relief Request 16R-11 (Page 8 of 12)
Table 2 Ginna Vertical Tendon Force Data (Tendons Retensioned 1980)
Structural Integrity Test (S.I.T.J Date: 0411411969 Tendon Mfnimum Required Prestress Force (MRV) = 636 kips Retensfoning Surveillance Average Measured Time Since Retensionmg Date Date Force (kips)
(Years) 611611980 7/18/1981 705 1.08 6118/1980 11/16/1983 702 3.41 6118/1980 4/1212016 690 35.82 6/lB/1980 11/17/1983 709 3.41 6/18/1980 8/31/1985 711 5.20 6/18/1980 12/11/2000 693 20.48 6/18/1980 6/2211995 711 15.18 6/18/1980 12/11/2000 686.
20.48 6/18/1980 5118/2021 692 40.91 6/'l8/1980 4113120H 690 30.82 6/18/1980 9/1212005 705 25.23 6/18/1980 7/18/1981 734 1-08 6/18/1980 7/9/1990 720 10.06 6/18/1980 8J2211995 697
- 15.18 6118/1980 4/12/2016 694 35.82 6/-18/1980 4113/2011 694 30.82 6/18/1980 5118/2021 685 40.91 6/18/1980 8/23/1995 699 15.18 6/18/1980 911212005 710 25.23 6/18/1980 8/23/1995 709 15.18 6/18/1980 4/1312011 687 30.82 6/18/1980 5118/2021 685
-40.91 6118/1980 9/15/2005 705 25.24 6/18/1980 7/18/1981 738 1.08 6/18/1980 7/27/1983 745 3.10 6/18/1980 4/1312011 724 30.82 6/18/1980 4/1212016 711 35.82 6/18/1980 7{9{1990 710 10.06 6/18/1980 5118/2021 692 40.91 6118/1980 6/25/2010 708 30.02 6118/1980 9/14/2005 715 25.24 6/18/1980 7/26/1983 721 3.10 6/18/1980 8/31/1985 705 5.20 6118/1980 12/12/2000 696 20.48
750 740 730
~ 720 Q.
~ -
~
- 1.
i
"'CJ C
~
l i *
~
710 700 690 680 670 660 650 640 630 J!!.
Tables and Figures Relief Request 16R-11 (Page 9 of 12)
Figure 2 Ginna Tendons (Retensioned in 1980)
~.
JI I
I ~ ~ - ';... - - - - - --
- =
/--
- . /
Tendon Mean Pratress Force Tr.endfine /
,_ _____________________ Minimum Req11iredPNNtJws5fane~6361dps ------------ ---- ---1 I
1 10 100 Years frvm 1980 Retensloning Note: The measured tendon forces since 1980 show that the tendon forces have remained acceptable and that the predicted average tendon forces in this group (1980 Retensioning Group) will remain well above the minimum required prestress for well beyond the end of the current plant operating license.
Tendon V-032 V-033 V-034 V-035 V-03(>
V-037 V-038 V-039 V-056 V-073 V-111 V-1t2 V-113 V-114 V-115 V-H7 V-118 V-119 V-120 V-121 V-122 V-126 V-034 V-035 V-115 V-U38 V--038 V-112 V-113.
Tables and Figures Relief Request IGR-11 (Page 10 of 12)
Table 3 Ginna Vertical Tendon Force Data (Tendons Reten-sioned 2006)
Structural Integrity Test (S.LT.) Date: 04/1411969 Tendon Minimum Required Prestress Force (MRV) = 636 kips Average Time Since Retensioning Swveillance Measured Force Retensioning Date Dates
{kips)
(Years) 9/23/2005 9/2312005 693 0.00 9/28/2005 9/28/2005 705 0.00 9/28/2005 9/28/2005 715 0,00 9/15/2005 9/1512005 703 0.00 9/28/2005 9/26/2005 708 0.00 9/27/2005 9/27/2005 703 0.00 9/15/2005 9/1512005 703 0.00 9127/2005 9/27/2005 690 0.00 9/23/2005 9/23/2005 723 0.00 9/23/2005 9/23/2005 700 0.00 W-ZULUU5 9/2212005 688 0.00 9/22/2005 9/22/2005 698 0.00 9/22/2005 9/22/2005 697 0.00 9/22/2005 912212005 700 0.00 912.212005 9/22/2005 705 0.00 9/19/2005 9/19rLU05 700 (lOO 9/21/2005 9/21/2005 725 0.00 9/21/2005 9/21/2005 687 0.00 9/21/2005 9/21/2005 705 0.00 9/20/2005 9/20/2005 700 0.00 9/20/2005 9/20J2005 685 0.00 9/19/2005 9/19/2005 718 0.00 9/28/2005 6/24/2010 720 4.74 9/15/2005 4/13/2011 699 5.57 9/22/200p 4/13/2011 697 5.56
';:J/1!"1J >fl II f!"l ou.. /LUIU o~t 4.lf 9115/2005 4f7/20'16 694 10.56 9122/2005 411.2/2016 694
- 10_55 9l22/2005 5/18/2021 6?8 15.tib
750 740 V-1.lB V--056 Tables and Figures Relief Request I6R-11 (Page 11 of 12)
Figure 3-1 Ginna Tendons (Retensioned in 2005)'
730 ____ V-126 -*i------i-----1t-----1t-----1i-----1-----1-----;-----;-------1 II/
. v-m, t;
10 lt-----
~ t ~
I
=
i,10 i :~--:~:::::
v-I ti V-038
,700 ~.* ~~-:<'
- Vtu I
I 16':lo, * ~
.. m
~
J I
V,.033 i
\
- V-114 1*-m
! 680 V-117 V--tll
. V-121
- E 670 V-032 --*-* V*U2 V-039
-~~--+----~-----~- ~~~~~~~~~~-~~~~+------t----7 --
,660 V~111 -j Tendon Mean PrestJ:esBforce Trendline V-119
~-
650
..,~
640 --------------1~---------- Minimum Required Prewess Forre.~636 kip~
I
... "'t-.. _... c I I
V-122 630 I
I J
0 10
.10 30 40 50 60 70 80 90 100 Years from 2005 Retensioning Note:
Due to limited amount of data collected on tendons in this group (2005 Retensioning Group) since 2005, the tendon force trendline has been constructed linearly, The rate of tendon prestress force loss is expected to decrease with time, so projecting tendon forces linearly is conservative,
730 720 710 700 Q, a. *
~..
690 0...
C 0
"lJ C
680 I-,,
670
~
660 650 640 630 Tables and Figures Relief Request I6R-11 (Page 12 of 12)
Figure 3-2 Ginna Tendons (Retensioned in 2005 and Subsequently Retested)
V-CU V-034
\1-115 V-<135
~
- V-038
- V-035 V-115 t
J*"'......
v...,...
- ...
- V-112 V-112.
V-113 V-1U Ten don Mean P.restress Force Trendlintt
- Minimum Required Prutress Fon:a = 636 kips I'... -
I 0
10 20 30 40 50 60 70 Years from 2005 Retensioning 80 90 Note:
Due to limited amount of data collected on tendons in this group (2005 Retensioning Group) since 2005, the tendon force trendline has been constructed linearly. The rate of tendon prestress force loss is expected to decrease with time, so projecting tendon forces linearly is conservative. This chart was constructed to show the performance of only those tendons retensioned in 2005 that have been subsequently retested. The mean prestress forces for the tendons retensioned in 2005 are projected to remain higher than the Minimum Required Prestress Force for at least 70 years from the 2005 retensioning date.