L-2017-069, Special Report - Containment Tendon Corrosion Protection Medium Volume Reduction

Special Report - Containment Tendon Corrosion Protection Medium Volume Reduction

ML17108A581
Person / Time
Site:	Turkey Point
Issue date:	04/17/2017
From:	Summers T Florida Power & Light Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
L-2017-069
Download: ML17108A581 (3)

Text

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APR 1 7 2017 L-2017-069 U.S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, D .C. 20555-0001 Re: Turkey Point Unit 4 Docket Nos. 50-251 Special Report - Containment Tendon Corrosion Protection Medium Volume Reduction The attached Special Report is provided in accordance with Turkey Point Units 3 and 4 Technical Specifications 6.9.2 and 3.6.1.6, Action c.

Should there be any questions regarding this information, please contact Mr. Mitch Guth, Licensing Manager at (305) 246-6698.

Sincerely,

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Thomas Summers Regional Vice President - Southern Region Attachment cc: Regional Administrator, Region II, USNRC Senior Resident Inspector, USNRC, Turkey Point Plant Florida Power & Light Company 9760 SW 344 St Homestead, FL 33035

L-2017-069 Attachment Page 1 of 2 SPECIAL REPORT

Purpose:

Florida Power and Light Company (FPL) submits this special report in accordance with Turkey Point Technical Specification (TS) 3.6.1.6, Action c., Containment Structural Integrity. Unit 4 entered Action c. on April 3, 2017 because the acceptance criterion in Surveillance Requirement (SR) 4.6.1.6.1.e.2 for corrosion protection medium (grease) volume in two containment tendons was not met.

Event and Action Taken:

The Turkey Point Unit 4 containment structure is a post-tensioned reinforced concrete structure.

The post tensioning feature of the structure is achieved by a system of vertical, dome and hoop tendons that are preloaded in accordance with structural requirements to attain a certain level of pre-stress to keep the concrete in compression. Each individual tendon consists of ninety 1/4 inch diameter steel wires encapsulated inside a tendon sheathing that in turn is filled with corrosion preventing grease.

Turkey Point TS Section 3/4.6.1.6 establishes Limiting Conditions for Operation and Surveillance Requirements (SRs) for the containment structural integrity, including corrosion protection medium (grease) leakage (SR 4.6.1.6.1.e). The SRs state that structural integrity of the containment buildings shall be demonstrated in accordance with ASME Code Section XI, Subsection IWL. The Tendon Surveillance IWL Inspection Program represents a systematic approach for assessing the continued operability and structural integrity of the containment post-tensioning system and concrete structure.

During each tendon surveillance period, as part of the scope of the inspection program, all accessible tendon caps are visually inspected for grease leakage and cap deformation.

On April 3, 2017, during the 45th year containment tendon surveillance for Turkey Point Unit 4, the absolute difference between the amount of grease removed from Unit 4 vertical tendons 56V2, and 23V6, and the amount of grease replaced exceeded 10% of the net duct volume. The specific data for each tendon is tabulated below:

Tendon Total Grease Volume Total Grease Volume Net Duct Grease  % of Net Duct Removed/Lost (gal) Replaced (gal) Volume (gal) Volume 56V2 16 46.03 89.36 33.6%

23V6 24.25 52.21 88.94 31.44%

The results of the examination indicated that the absolute difference between the amount removed and the amount replaced exceeded 10% of the tendon net duct volume, and as such the acceptance criterion of TS SR 4.6.1.6.1.e.2 was not met. The grease was replenished with the required grease volumes as part of the inspection activities. As such, upon replenishment of the grease volume, these tendons were restored to an acceptable condition, an engineering evaluation was performed in

L-2017-069 Attachment Page 2 of 2 accordance with the pertinent articles of IWL, and a special report is submitted herein in accordance with the requirements of TS 6.9.2, Special Report.

Article IWL-3221.4, Corrosion Protection Medium, states that The absolute difference between the amount removed and the amount replaced shall not exceed 10% of the tendon net duct volume.

Article IWL-3222, Acceptance by Evaluation, states that items with examination results that do not meet the acceptance standards of IWL-3221, Acceptance by Examination, shall be evaluated as required by Article IWL-3300, Evaluation.

In accordance with the requirements of IWL-3300, FPL has performed the acceptance evaluation in Condition Report 2196366. The subject tendons were identified as leaking from the gasket at the bottom end, located inside the tendon gallery. There was no evidence of unusual grease stains on the exterior containment surface. Corrosion was not observed on any of the tendon components due to the grease loss, and the reported grease volume reduction did not introduce any concerns pertaining to the operability or structural integrity of the subject tendons nor did it affect the integrity of the Unit 4 containment structure.

Cause:

The most probable cause of the differences in grease volume for tendons 56V2, and 23V6 was leakage from the bottom end tendon caps due to leaking cap gaskets.

Schedule for Restoration:

The end cap gaskets for tendons 56V2, and 23V6 were replaced. The grease was replenished with the required grease volumes as part of the inspection activities. As such, upon replenishment of the grease volume, these tendons were restored to an acceptable condition, and thus in compliance with the requirements of the TS.