ML20043F926

Responds to NRC Bulletin 89-002, Stress Corrosion Cracking of High-Hardness Type 410 Stainless Steel Internal Preloaded Bolting in Anchor/Darling Model S3502 Swing Check Valves or Valves of Similar Design.

ML20043F926
Person / Time
Site:	Sequoyah
Issue date:	06/13/1990
From:	Wallace E TENNESSEE VALLEY AUTHORITY
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
IEB-89-002, IEB-89-2, NUDOCS 9006180313
Download: ML20043F926 (5)

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i 5N 157B Lookout Place JUN 131990 i U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D.C. 20555  ! ! Gentlemen. In the Matter of ) Docket Nos. 50-327 I Tennessee Valley Authority ) 50-328 i SEQUOYAH NUCLEAR PLANT (SQN) UNIT 1 - FINDINGS IN RESPONSE TO NRC BULLETIN.  ! NO. 89 STRESS CORROSION CRACKING OF HIGH-HARDNESS TYPE 410 STAINLESS STEEL INTERNAL PRELOADED BOLTING IN ANCHOR DARLING MODEL S350H SHING CHECK VALVES OR VALVES OF SIMILAR DESIGN

Reference:

NRC Bulletin No. 89-02 dated July 19, 1989, " Stress Corrosion Cracking of High-Hardness Type 410 Stainless Steel Internal Preloaded Bolting in Anchor Darling Model S350H Swing Check Valves or Valves of Similar Design" , In response to the_ referenced bulletin, TVA.has evaluated SQN's safety-related check valves for Type 410-stainless steel internal bolting. .A total of twelve valves on each unit were identified. Ten valves were Anchor Darling Model S350H swing check valves located in SQN's safety injection system, and two valves were Crane-Alloyco Model 8C54 swing check valves located in SQN's  ! residual heat removal system. The Unit i valves were disassembled and visually examined during the Unit 1 Cycle 4 refueling outage. No broken studs or bolts were encountered, and a visual examination revealed no linear indications. The internal bolting material for the Unit 1 Anchor Darling valves was replaced with American Society of Testing Material (ASTM) A564-630-ll50 stud material. The stud

                                           -material for the Unit 1 Crane-Alloyco valves was replaced with American
                                            . Society of Mechanical Engineer (ASME) SA193 Grade B6 having a correlated Rockwell Hardness (Rc) below the maximum Rc26 value recommended by the referenced bulletin.

The required inspections and bolt replacement for the Unit 2 valves are scheduled during the end of the Unit 2 Cycle 4 refueling outage. This outage is projected to begin in September 1990. Following the Unit 2 valve inspections, a report will be submitted to NRC in accordance with the 60-day reporting requirement of the bulletin. Enclosure 1 contains a list of SQN valves that are applicable to the referenced bulletin. Also enclosed is a description of the programmatic controls now in place at SQN to preclude the use of bolts susceptible to stress corrosion cracking within the Anchor Darling valves. Enclosure 2 contains commitments associated with the Unit 2 valve inspections and reporting requirements. 9006180313 900613 gg goa nnockosooggg7 , , , , , t

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         .           U.S. Nuclear Regulatory Commission                          JUN 131990 L                     Please direct questions concerning this issue to Don V. Goodin at       .

(615) 843-7734. - 1 , Very truly yours,

                                                                                            ]

j TENNESSEE VALLEY AUTHORITY k.Nuclear. t Wallace, G. Y'Licensing Manager and i Regulatory Affairs l Enclosure-- ,

                    'cc (Enclosure):                                                         i Hs. S. C. Black, Assistr.nt Director-                              !

I-IV- 1 TVA Projects Division. I

U.S. Nuclear Regulatory Commission  !

l One White Flint, North l 11555 Rockville Pike, MS 13H2  ; l- Rockville, Maryland 20852 , i NRC Resident Inspector Sequoyah Nuclear Plant 2600 Igou Ferry Road a Soddy-Daisy, Tennessee 37379 i Mr. B. A. Wilson, Assistant Director -l of TVA Projects q U.S. Nuclear Regulatory Commission ' Region II 101 Marietta Street, NW, Suite 2900 Atlanta, Georgia 30323  ; o 1

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a i s~ , i l ENCLOSURL 1 L

                    . I. Anchor Darlino Valves                                                          .

TVA conducted a review of SQN's check valve maintenance program database to id6ntify Anchor Darling Model S350H swing check valves with internal - bolting. From this review, ten valves per unit were identified. These valves are located in SQN's safety injection system and are listed below. Valve Identifier. Size (inches) Description 1-VLV-63-561 10 Loop 2 CLSI' .;~ 1-VLV-63-623 10 Accumulator 2 CLSI 1-VLV-63-560 10 Loop 1 CLSI. 1-VLV-63-622 10 Accumulator 1 CLSI , VLV-63-562 10 Loop 3 CLSI 1-VLV-63-624 10 Accumulator.3 CLSI l-VLV-63-563 10 Loop 4 CLSI l-VLV-63-625- 10 Accumulator 4 CLSI l-VLV-63-640 8 Loop 1 HLSI' ' l-VLV-63-643 8 Loop 3 HLSI CLSI - Cold leg safety injection

                          *HLSI - Hot leg safety injection                                              i The Unit 2 valve list is identical to the Unit i valve list with the exception of the Unit 2 prefix associated with the valve identifier.

II. Other Safety-Related Check Valves of Similar Design TVA conducted a review of SQN's vendor-drawings to identify other safety-related valves similar in design to the Anchor Darling Model S350W valves. From this review,-two valves per unit were identified. These valves are manufactured by Crane-Alloyco and are located in SQN's~ residual heat removal (RHR) system. These valves are listed below. Valve Identifier Size (inches) Description 1-VLV-74-514 8 RHR Pump 1A-A Discharge 1-VLV-74-515 8 RHR Pump 18-B Discharge I The Unit 2 valve list is identical to Unit 1 list above with the exception of the Unit 2 prefix associated with the valve identifier and RHR pump' designation. III. SON Action - Unit i Inspection and changeout of the internal bolting on the ten Anchor Darling swing check valves were accon,plished under SQN Design Change Notice (DCN) 1520. This work activity occurred during the Unit 1

                         . Cycle 4 refueling outage (April 8-21, 1990). No broken studs or bolts were encountered, and a visual examination revealed no linear indications.

a. l l The internal bolting material was replaced with American Society of  ! Testing Material (ASTM) A564-630-1150, which is a Type 17-4PH stainless steel. To provide programmatic control, vendor drawings for the Anchor  ; Darling valves have been revised to specify ASTM A564-630-1150 material = for future stud replacement. Inspection and changeout of the. internal bolting on the two Crane-Alloyco check valves-were accomplished under Work Requests (WRs)  ; B268182 and B268181. __This work activity also occurred during the Unit 1 Cycle 4~ refueling outage (April 11-12, 1990). No broken studs or' bolts were encountered, and a visual examination revealed no linear- , indications. The internal bolting material was replaced with American i Society of Mechanical Engineer (ASME) SA193 Grade B6 with proper heat

                      ' treatment. The material test report provided by the bolt manufacturer indicated _that the replacement bolts were tempered at 1100 degrees Fahrenheit for 3 hours and had a tensile strength of 115,100 pounds per                       !

square inch. This correlates to a Rockwell Hardness (Rc) value between Rc22 and Rc23 (below the maximum Rc26 value recommended by Bulletin 89-02). -The bolt material procurement process for this material was revised to include an evaluation of maximum allowable , tensile strength during receipt inspection. Because properly heat-treated SA193 Grade B6 has a low probability for stress corrosion cracking in a borated water environment, TVA considers this material to be a suitable replacement for these valves. 1 IV SON Action - Unit 2 Inspection and changeout of the internal bolting on the ten Anchor Darling and two Crane-Alloyco check valves are scheduled for Unit 2 Cycle 4 refueling outage projected to begin in. September 1990. The Anchor Darling valves will be worked under SQN DCN 1519, and the Crane-Alloyco valves will be worked under WRs B268184 and B268183. Findings from the Unit _2 valve inspection 'al' be-submitted to.NRC in accordance with the 60-day reporting requir went of the bulletin.

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y', .- ENCLOSURE , Iji TVA Comm'ltment;

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\ :. l a 1_. Inspection and changeout of,the internal. bolting l:for. ten Anchor Darling and;two: Crane-Alloyco check. valves.'on.-Unit 2~will be-' conducted.during_the-

                                                   - Unit 2 Cycle 4: refueling outage.
                                 , , 2.                 Findings from'the : Unit-2 valve inspection?wiL11 be sutimitted to NRC within '

ll ' - 60 days.following-l completion of the inspections.  :-{ u  ! b) l i.- - 7

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