ML20006B277

Forwards Response to NRC 891208 Request for Addl Info Re Facility Inservice Insp Program for First 10-yr Interval.End of Insp Interval Extended to 940915 Due to Extended Shutdown Period

ML20006B277
Person / Time
Site:	Sequoyah
Issue date:	01/25/1990
From:	TENNESSEE VALLEY AUTHORITY
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
TAC-59457, NUDOCS 9002010230
Download: ML20006B277 (5)

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TENNESSEE VALLEY AUTHORITY CH ATTANOOGA. TENNESSEE 37401 i

SN 1578 Lookout Place JAN25 6  :

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

In the Matter of ) Docket No. 50-327 Tennessee Valley Authority ) l SEQUOYAH NUCLEAR PLANT (SQN) - RESPONSE TO NRC REQUEST FOR INFORMATION -

IN-SERVICE INSPECTION (ISI) PROGRAM, FIRST 10-YEAR INTERVAL  ;

References:

1. NRC letter to TVA dated December 8, 1989, " Request for i Information.- Inservice Inspection Program,' first 10-Year Interval (TAC 59457) - Sequoyah Nuclear Plant, Unit 1"

2. TVA letter to NRC dated May 5, 1989, "Sequoyah Nuclear Plant (SQN) - Augmented and Accelerated _ Inservice Inspection (ISI)

Program for Unit 1" ,

1 By Reference 1, NRC requested additional information regarding TVA's ISI [

program for SQN Unit 1. This information was requested to support the completion of NRC review of this program. Enclosed is the requested information to support NRC review of TVA's ISI program for Unit 1 that was submitted to you by Reference 2.

It is important to note that Section 1.0 of Reference I stated that the first

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10-year inspection interval for SQN's Unit 1 ends on June 30, 1991. This was the end date of the original inspection interval; however, because of SQN's extended shutdown period, the end of the 10-year inspection interval for Unit I was extended to September 15, 1994. This extension is discussed in Section 3.0 of TVA's ISI program as submitted by Reference 2.

\

Please direct questions concerning this issue to D. V. Goodin at (615) 843-7734.

Very truly yours,  !

TENNESSEE VALLEY AUTHORITY Manager, Nuclear Licensing and Regulatory Affairs Enclosure cc: See page 2 '

Of hS"*$8$38888sg5..

Ph$h An Equal Opportunity Employer

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, , 2 U.S. Nuclear Regulatory Commission g

cc (Enclosure):

Ms. S. C. Black, Assistant Director for Projects TVA Projects Division U.S. Nuclear Regulatory Commission One White Flint, North 11555 Rockville Pike Rockville, Maryland 20852 Mr. B. A. Wilson, Assistant Director for Inspection Programs TVA Projects Division U.S. Nuclear Regulatory Commission Region II 101 Marietta Street, NW, Suite 2900 Atlanta, Georgia 30323 NRC Resident Inspector Sequoyah Nuclear Plant 2600 Igou Ferry Road Soddy Daisy, Tennessee S7379 4

', ENCLOSURE

1. NRC Request

" Relief Request ISI-8 , , , requests relief from volumetric examination of pressure retaining reactor coolant pump welds. The basis for Relief Request ISI-8 is that the present capability of ultrasonic testing (UT) is not sufficient to examine the cast 304 stainless steel pump material and achieve meaningful results.

The staff and the nondestructive testing industry are in general agreement that performing ultrasonic testing of cast stainless steel (CSS) is difficult because of poor acoustical properties of the materials of construction. However, the staff has always taken the position that the liccace should stay abreast of the latest state-of-the-art developments in i,e, forming UT on the CSS.

The latest ultrasonic testing systems, developed for inspection of welds in cast austenitic pumps, use large-diameter focused beam probes and low frequency compression waves to ultrasonically examine the total wall thickness of the pump. In a recent field application of such a technique at a foreign nuclear plant, approximately 70% of the pump weld volume was successfully inspected without disassembly of the pump , . .

Please discuss the possibility of performing an ultrasonic examination of the reactor coolant pump casing weld at Sequoyah Unit 1 by the end of the current 10-year interval using this technique or any other state-of-the-art techniques deemed appropriate,"

TVA Response The reactor coolant pumps (RCPs) in question were manufactured by.

Westinghouse Electric Corporation and are classified as a Type F: style as depicted in figure INB-2500-16 of the American Society of Mechanical Engineers (ASME) Code, Section XI. The weld and adjacent base metal are in the thickness range of approximately S inches, Current ultrasonic technology available in the United States does not offer significant improvements in examining CSS in this thickness range. Recent technological advancements in ultrasonic examination of CSS piping ha offered considerable improvement in thicknesses up to approximately 3 inches, These advancements have been achieved through improved search units, pulser / receivers and computer-aided imaging and signal-processing (e.g., spatial averaging) techniques. TVA has acquired advanced-ultrasonic equipment to provide improvements in the examination of CSS piping. While these advancements are significant, the thickness limitation of the SQN RCP casing welds has prevented the application of a suitable ultrasonic technique, which complies with Section XI requirements and establishes meaningful baseline data. In order to stay abreast of state-of-the-art ultrasonic techniques for the examination of.RCP Welds, TVA regularly communicates with the Electric Power Research Institute (EPRI), other utilities with similar pump designs, and several In-service Inspection (ISI) vendors regarding their current ultrasonic methods for the subject examinations.

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, , Based on information provided, it appears that at least one vendor has 'i successfully applied ultrasonic examination to RCP welds in combination ,

with double-wall source radiography performed without pump disassembly.

However, the examinations have been limited to Byron Jackson pumps with  !

" snail shell" type casings comprised of two circumferential and one vertical weld. In addition, the thinner casings have allowed ultrasonic  :

testing to be conducted up through approximately 2.9 inches. The SQN pump configuration and associated thickness ranges do not fall within these  ;

parameters and are therefore not a candidate for these examination '

techniques.

TVA is currently seeking and acquiring information relative to the ultrasonic-examination techniques utilized by a vendor at a foreign "

plant. EPRI is assisting TVA in acquiring technical, code, and pump j configuration information in response to the examination of French RCP by Vincotte of Belgium. As of this time, there appears to be no ultrasonic-examination technique available in the United States to perform a Section XI code examination using ultrasonic techniques on the SQN RCPs.  ;

TVA is aware that radiography techniques utilizing a remotely operated ,

miniature linear accelerator (MINAC) or source could provide an acceptable Section XI code examination. However, because of costs, personnel radiation exposure, and pump disassembly, these methods do not offer a viable option without risks associated with complete RCP disassembly.

TVA has three remaining outages in the first 10-year interval for SQN Unit 1. During the interim, TVA will continue to assimilate information s regarding advanced ultrasonic techniques that may be applied to the RCP configuration as described herein.

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2. NRC Reauest

. . . Relief Request ISI-14 related to this augmented inspection program i was submitted in the Sequoyah Unit 2 ISI plan, Revision 13 . . . but a '

similar reller request has not been submitted for Sequoyah Unit 1.

Please discuss the applicability of Relief _ Request ISI-14 to Sequoyah

• Unit 1."

TVA Response Relief Request 151-14 submitted in the SQN Unit 2 ISI plan (Revision 13),

does not apply to the Sequoyah Unit 1 ISI plan as related to the accelerated field weld inspection program. ISI-14 requests relief from-the code percentage requirements of Tables IHB-2412-1 and IHC-2412-1 of ASME Code, Section XI, because of the implementation of the accelerated-field weld progrem. Based on the present schedule of refueling outages,.

the code percentage requirements will be maintained for SQN. Unit 1 with implementation of the accelerated field weld program.

1 J

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,,,o g , 3 The commitment to complete this accelerated program requires that inspections for field welds be compicted in the two consecutive refueling outages following restart from the extended shutdown period. The following time lines show the schedule of outages following restart and-the inspection period schedule at the time of commitment to the accelerated field weld program.

Note: The complete inspection period schedule is discussed in Section 3.0 of both ISI plans.

Seouoyah Unit l' Second Inspection- Third Inspection Period  ! Period

).........*............*..................!....*......(

Start-up Cycle 4 Cycle 5 Outage Outage Sequoyah Unit 2 Second Inspection Period  !

).........*........*.....'............. ....... ! ..._...(

Start-up Cycle 3 Cycle 4 Outage Outage As shown on the Unit 1 time line, the Cycle 4 and-Cycle-5 outages are the two consecutive refueling outages following start-up and occur during the-second and third inspection periods respectively, By completing all_ '

required field weld inspections during the Cycle 4'and 5 outages, the required inspection period percentages are maintained. However, as shown on the Unit 2. time line, the two consecutiv'e refueling outages following start-up, Cycles 3 and.4, both occur during the second' inspection period.

Because the Unit 2 outages occur in the second inspection period, field welds scheduled during the third inspection pe_rlod are required'to be inspected during the second inspection period, thus requiring r_el_lef from the code percentage requirements.