ML022170705

American Society of Mechanical Engineers (ASME)Section XI Inservice Inspection (ISI) Program - Revised Requests 1-ISI-20 & 2-ISI-20

ML022170705
Person / Time
Site:	Sequoyah
Issue date:	07/31/2002
From:	Salas P Tennessee Valley Authority
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
Download: ML022170705 (10)

Text

July 31, 2002 10 CFR 50.50a(g)(5)(iii)

U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D. C. 20555 Gentleman:

In the Matter of ) Docket Nos. 50-327 Tennessee Valley Authority ) 50-328 SEQUOYAH NUCLEAR PLANT (SQN) - AMERICAN SOCIETY OF MECHANICAL ENGINEERS (ASME) SECTION XI INSERVICE INSPECTION (ISI)

PROGRAM - REVISED RELIEF REQUESTS 1-ISI-20 and 2-ISI-20 Enclosed are revised relief requests 1-ISI-20 and 2-ISI-20 that were previously submitted to you by TVA letter dated August 10, 2001. The relief requests are resubmitted in their entirety (with the exception of Enclosures 3, 4, and 5) and are based on a telephone discussion with the NRC staff on July 25, 2002. In accordance with the staffs request, the relief requests are resubmitted to remove references to ASME Code Case N-435-1. TVA is also taking the opportunity to include the Examination Data Report (as Attachment 1) that contains the percentage value for examination coverage of the Unit 2 weld (examination coverage became available after the Unit 2 weld examination that was performed during the U2C11 refueling outage). Attachment 1 supplements the Enclosure 3 information from TVAs August 10, 2001 letter.

This submittal is provided in accordance with NRC RIS 2001-05. If you have any questions regarding this response, please contact me at extension (423) 843-7071 or J. D. Smith at extension (423) 843-6672.

Sincerely, Original signed by Pedro Salas Licensing and Industry Affairs Manager Enclosure

ENCLOSURE SEQUOYAH NUCLEAR PLANT REVISED AMERICAN SOCIETY OF MECHANICAL ENGINEERS (ASME) RELIEF REQUESTS FOR UNITS 1 AND 2 1-ISI-20 2-ISI-20

Revised Requests For Relief 1-ISI-20 and 2-ISI-20 Executive Summary:

TVA is requesting relief from ASME Code to address the Seal Water Filter (SWF) head-to-shell weld SWFW-2. The design configuration of the SWF head-to-shell weld precludes volumetric examination due to the vessel wall thickness being less than 0.2 inch. A 100% surface examination of the required area for the head-to-shell weld is also limited. These physical examination limitations occur when the 1989 Code examination requirements are applied in areas of components constructed and fabricated to early plant physical designs. Based on the issue date of Sequoyah Nuclear Plants (SQN) construction permit (May 27, 1970), SQN is exempt from the code requirements for providing original design and examination access provisions as allowed in 10 CFR 50.55a(g)(4).

A liquid penetrant surface examination was performed on accessible areas to the maximum extent practical, given the physical limitations of the subject weld for Unit 1 and Unit 2. The design configuration limits the best effort liquid penetrant surface examination to approximately 65% for Unit 1 and 68% for Unit 2. The design configuration for the welds are the same for both units. Performance of a volumetric examination of the subject welds is impractical due to the wall thickness being less than 0.2 inch. Performance of a surface examination of essentially 100% of the full penetration weld (SWFW-2 for both units) is also impractical due to welded support attachments. The maximum extent practical surface examination of the subject weld provides reasonable assurance of an acceptable level of quality and safety because the information and data obtained from the accessible weld surface provides sufficient information to judge the overall integrity of the weld.

Therefore, pursuant to 10 CFR 50.55a(g)(5)(iii), it is requested that relief be granted for the second inspection interval.

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Units: 1 and 2 System: Chemical Volume and Control -

System 62 Components: Seal Water Filter, Head-to-Shell Weld, Full Penetration Weld ASME Code Class: ASME Code Class 2 (Equivalent)

Section XI Edition: 1989 Edition Code Table: IWC-2500-1 Examination Category: C-A, Pressure Retaining Welds in Pressure Vessels Examination Item Number: C1.20, Head Circumferential Weld Code Requirement: ASME Section XI, Table IWC-2500-1, Examination Category C-A, Item Number C1.20 Code Requirement From Which Relief Is Requested: Volumetric Examination Coverage of Essentially 100%

of the Head-to-Shell Weld List Of Items Associated With The Relief Request: SWF Head-to-Shell Welds:

SWFW-2 (Unit 1)

SWFW-2 (Unit 2)

Basis For Relief:

The vessel wall thickness of the SWF is less than 0.20 inch. Accordingly, a surface examination is being performed in place of a volumetric examination. The design configuration of the SWF precludes a complete surface examination of the required area for the head-to-shell weld SWFW-2. The design configuration limits the surface examination to approximately 65% for Unit 1 and 68% for Unit 2 of the required examination areas as calculated in accordance with TVA procedure N-GP-28.

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Alternative Examination:

In lieu of the code required volumetric examination, a best effort liquid penetrant surface examination was performed on accessible areas to the maximum extent practical given the physical limitations of the head-to-shell weld. Refer to Enclosure 3 (and Attachment 1 of this letter) for examination data reports.

Justification For The Granting Of Relief:

The wall thickness of the shell is less than 0.20 inch and is the basis for performance of a surface examination in lieu of a volumetric examination. The design configuration of the subject head-to-shell weld precludes surface examination of essentially 100% of the required examination area. In order to examine the weld in accordance with the code requirement, the SWF would require extensive design modifications. The physical arrangement of welds (SWFW-2) precludes a complete surface examination due to welded support attachments which carry the weight of the component to the floor. A total of four channel beam attachments are welded along the axial direction of the component at four equally spaced locations. Each attachment is approximately 4.4 inches in width and covers the adjoining circumferential head-to-shell weld. The complete circumference of the component is 50.25 inches. The Unit 1 unexamined area is 17.6 inches of a possible 50.25 inches. The Unit 2 weld coverage was approximately the same.

The support attachments which cover the subject weld induce negligible stresses in the head-to-shell weld.

The function of the support attachment is to carry the weight of the component.

Radiographic examination from the outside surface as an alternate volumetric examination method was determined to be impractical due to the support attachment affecting radiographic quality. Performing radiographic examination from the inside surface of the SWF would require placing a radiographic source near the center of the head. The SWF would require disassembly and access to the inner surface would result in extreme radiological conditions (high contamination and dose to personnel). Again radiographic quality is compromised due to the support attachments. Thus, radiography from the inner surface, to gain any additional coverage, is also impractical.

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Performance of an ultrasonic volumetric examination to supplement the required coverage was also deemed to be impractical. The support attachments are four-inch channel steel. An ultrasonic search unit cannot be placed on top of the outside head-to-shell weld due to the support attachment interference.

Performing a surface examination from the inside was determined to be impractical because of the following radiological factors.

The estimated radiological conditions for the inside surface of the SWF were determined to be the following:

3-4 rad/hour beta (uncorrected) 1-2 rem/hour gamma 1 rad/hour per 100 square-cm Maximum stay time to maintain exposure to < 1 rem is approximately 30 minutes. One rem is the annual administrative dose limit for an individual. Special clothing would be required for protection from the extremely high contamination levels and from the high beta dose rate. Estimates are based on actual experience inside primary components. Respiratory protection would be required.

Performing a volumetric examination on this weld would be impractical due to the wall thickness (i.e., less than 0.20 inch). Also, performing a surface examination of essentially 100% of the required area of the SWF head-to-shell weld would be impractical. In addition, it is impractical to perform radiography or surface examinations from the inside as discussed above. The maximum extent practical surface examination of the weld areas and adjacent metal and the code required visual test (VT)-2 examination for leakage will provide reasonable assurance of an acceptable level of quality and safety. Significant degradation, if present, would have been detected during the surface and VT-2 examinations that were performed on the subject weld. As a result, reasonable assurance of structural integrity for this weld is provided by the examinations that were performed.

Therefore, pursuant to 10 CFR 50.55a(g)(5)(iii), it is requested that relief be granted for the second inspection interval.

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Implementation Schedule:

This request for relief is applicable to the second inspection interval for SQN Unit 1 and 2. Weld SWFW-2 for Unit 1 and Unit 2 were examined in the second period.

References:

- Examination Data Report:

R-7609 (Unit 1) - Examination Data Report R-6358 (Unit 2) - ISI Program Drawings:

ISI-0458-C-01 (Unit 1)

ISI-0459-C-01 (Unit 2) - Nondestructive Examination Procedure N-GP-28 Calculation of ASME Code Coverage for Section XI NDE Examinations E-5

Attachment 1 Examination Data Report Request for Relief Examination Data Number Report 2-ISI-20 R-6358