ML20065N645
| ML20065N645 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 12/07/1990 |
| From: | Wallace E TENNESSEE VALLEY AUTHORITY |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| IEB-89-002, IEB-89-2, NUDOCS 9012120227 | |
| Download: ML20065N645 (4) | |
Text
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s TENNESSEE VALLEY AUTHORITY l
CH ATT ANOOG A. TENNESSEE 374o1 5B Lookout Place DEC 071990 U.S. Nuclear Regulatory Commission ATTN Document Control Desk Washington, D.C.
20555 Gentlemen:
In the Matter of
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Docket No. 50-328 Tennessee Valley Authority
)
SEQUOYAH NUCLEAR PLANT (SQN) - UNIT 2 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 S350W SWING CHECK VALVES OR VALVES OF SIMILAR DESIGN
References:
1, NRC Bulletin No. F7-02 dated July 19, 1989 " Stress Corrosion Cracking of High-Hardness Type 410 Stainless Steel Internal Preloaded Bolting in Anchor Darling Model S350W Swing check Valves or Valves of Similar Design" 2.
TVA letter to NRC dated June 13, 1990, "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 S350W Swing Check Valves or Valves of similar Design" By Reference 2, TVA submitted the response to NAC Bulletin 89-02 for SQN.
Reference 2 contained TVA's evaluation of SQN's safety-re'sted check valves for Type 410 stainless cieel internal bolting. A total ot twelve valves on each unit were id;uitfled. Ten valves were Anchor Darling Model S350W 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.
Findings from the Unit 1 inspection and bolt changeout that took place during the Unit 1 Cycle 4 refueling outage (April 1990) were provided in Enclosure 1 of-Reference 2.
This letter provides the results of the findings on SQN Unit 2.
Twelve SQN Unit 2 valves were disassembled and visually examined during the Unit 2 Cycle 4 refueling outage (September - November 1990). Visual examination revealed that one Anchor Darling valve (63-640) had a broken
. retaining block e*ud.
One Crane-Alloyco valve (74-514) experienced stud failure during rem.tal. No broken studs or bolts were encountered on the remaining Unit 2 valves. The internal bolting material for the ten Unit 2 Anchor Darling valves was replaced with American Society of Testing Material (ASTM) A564-630-ll50 stud material. The stud material-for the two Unit 2 Crane-Alloyco valves was replaced with American Society of Mechanical Engineer (ASME) SA193 Grade B6 having a correlated Rockwell hardness (Rc) below the maximum Rc 26 value recommended by t he subject bulletin.
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An Equal Opportunity Employer
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DEC 071990.
U.S. Nuclear Regulatory Commission The enclosure contains a list of SQN's Unit 2 valves that are applicable to the subject bulletin and a descripti.. of the programmatic controls now in place at SQN to preclude the use of.s' t= susceptible to stress corrosion cracking within the Anchor Darling val, This letter provider 3.fication to NRC that all actions required by Bulletin 89-02 are no, ensplete for SQN.
Please direct questiori.
a.. erning this issue to Don V. Goodin at (615) 843-7734.
Very truly yours, TENNESSEE VALLEY AUTHORITY
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& U-E. G. Wallace, Manager Nuclear Licensing and Regulatory Affairs
_c. tosure ec (Enclosure):
Ms. S. C. Black, Deputy Director Project Directorate II-4 U.S. Nuclear Regulatory Commission One White Flint, North 11555 Rockville Pike Rockvi41e. Maryland 20852 Mr. J. N. Donohew Project Manager U.S. Nuclear Regulatory Commission One White Flint, North 11555 Rocksille Pike Rockville, Maryland 20852 NRC Resider t In.<ector Sequeyah Nuclear Plant 2600 Igou Ferry Road Soddy Daisy, Tennessee 37379 Mr. B. A. Wilson, Project Chief U.S. Nuclear Regulatory Commissi n Region II 101 Marietta Street, NW, Suite 2900 Atlanta, Georgia 30323
e ENCLOSURE I.
Anchor Darling Valves-TVA conducted a review of SQN's check valve maintenance program database to identify Anchor Darling Model S350W 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 2-VLV-63-561 10 Loop 2 CLSI' 2-VLV-63-623 10 Accumulator 2 CLSI 2-VLV-63-560 10 Loop 1 CLd4 2-VLV-63-622 10 Accumulator i cLSI 2-VLV-63-56 2 10 Loop 3 CLSI 2-VLV-63-624 10 Accumulator 3 CLSI 2-VLV-63-563 10 Loop 4 CLSI 2-VLV-63-625 10 Accumulator 4 CLSI 2-VLV-6 3-640 8
Loop 1 HLSI*
2-VLV-63-643 8
Loop 3 HLSI
'CLSI - Cold leg safety injection
'HLSI - Hot leg safety injection The Unit. 1 valve list is identical to the Unit 2 valve list with the exception of the unit 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 2-VLV-74-514 8
RHR Pump 2A-A Discharge 2-VLV-74-515 8
RHR Pump 2B-B Discharge The Unit 1 valve list is identical to the Unit 2 list above with the exception of the unit prefix associated with the valve identifier and RHR pump designation.
III. SQN Action - Unit 2 Inspection and changcout of the internal bolting on the ten Anchor Darling swing check valves were accomplished under SQN Design Change Notice (DCN) 1519. This work activity occurred during the Unit 2 Cycle 4 refueling outage (October 1990). Visual examination revealed that one Anchor Darling valve (63-640) had a broken r6.alning block stud.
No broken studs or bolts were encountered on the remaining Unit 2 Anchor Darling valves.
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 interna". bolting on the two Cranc-Alloyco check valves were accomplished under Work Requests (WRs)
B268183 end B268184. This work activity also occurred during the Unit 2 Cycle 4 ret':teling outage. One Crane-Alloyco valve (74-514) experienced stud failure during removal. No broken studs or bolts were encountered on the second valve (74-515). The internal bolting material was replaced with American 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 degreca Fahrenheit for 3 hours3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br /> and had a tensile strength of 11%: 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.
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