SER Granting Relief & Concluding That Code Required Exam Impractical to Perform to Extent Required by Code & That Limited Section XI Surface Exam Provide Results Which Demonstrated to Be Superior or Equivalent to Surface ExamML20059B828 |
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Site: |
South Texas ![STP Nuclear Operating Company icon.png](/w/images/9/9c/STP_Nuclear_Operating_Company_icon.png) |
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Issue date: |
10/21/1993 |
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From: |
Office of Nuclear Reactor Regulation |
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To: |
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Shared Package |
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ML20059B794 |
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References |
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NUDOCS 9310290109 |
Download: ML20059B828 (3) |
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Category:SAFETY EVALUATION REPORT--LICENSING & RELATED ISSUES
MONTHYEARML20217K9441999-10-15015 October 1999 SER Accepting Util Alternative Proposed Relief Request RR-ENG-2-4 for Second 10-year ISI Interval at Stp,Units 1 & 2 Pursuant to 10CFR50.55a(a)(3)(i) ML20217K9151999-10-15015 October 1999 SER Authorizing Util Relief Request RR-ENG-2-3 for Second 10-year ISI Interval of Stp,Units 1 & 2 Pursuant to 10CFR50.55a(a)(3)(i) ML20211P7811999-09-0909 September 1999 SER Approving Second 10-year Interval Inservice Insp Program Plan Relief Request RR-ENG-2-8 (to Use Code Case N-491-2) for South Texas Project,Units 1 & 2 ML20211Q6731999-09-0909 September 1999 Safety Evaluation Accepting First 10-yr Interval ISI Program Plan Request for Relief from ASME Code Case N-498 ML20211P8411999-09-0909 September 1999 Safety Evaluation Supporting Alternative Proposed by Licensee to Surface Exam to Perform Boroscopic VT-1 Visual Exam of Pump Casing Welds within Pump Pits for Welds Covered by Relief Request RR-ENG-24 ML20211F4531999-08-24024 August 1999 Safety Evaluation Supporting Licensee Proposed Alternative to Defer Partial First Period Exams of flange-to-shell Weld to Third Period & Perform Required Ultrasonic Exams,Both Manual & Automated,During Third Period ML20211F5111999-08-23023 August 1999 Safety Evaluation Supporting Licensee Proposed Alternative Contained in Request for Relief RR-ENG-30 ML20210D9161999-07-23023 July 1999 Safety Evaluation Accepting Inservice Testing Relief Request RR-56 Re Component Cooling Water & Safety Injection Sys Containment Isolation Check Valve Closure Test Frequency ML20207H6361999-07-0808 July 1999 Safety Evaluation Approving 2nd 10 Yr Interval ISI Program Plan Request to Use ASME Section XI Code Case N-546 for Licenses NPF-76 & NPF-80,respectively ML20195J6871999-06-17017 June 1999 Safety Evaluation Supporting Proposed Alternative Contained in RR-ENG-2-5.Proposed Alternative Authorized Per 10CFR50.55a(a)(3)(i) for 2nd ISI Interval ML20204B2711999-03-15015 March 1999 Safety Evaluation Authorizing 990201 Request to Authorize Alternative to Regulations Per 10CFR50.55a(a)(3)(i) That Would Revise Start of Second 120-month IST Interval to No Later than 011201 ML20203H8361999-02-17017 February 1999 Safety Evaluation Supporting Request for Relief from ASME Code Requirements for Class 3 Piping for Plant ML20202H9621999-02-0303 February 1999 SER Accepting Change to EALs Used in Classification of Emergency Conditions ML20199K7711999-01-21021 January 1999 Safety Evaluation Accepting ISI Program Request for Relief for ASME Cose Repair Requirements for Code Class 3 Piping ML20199G8161999-01-19019 January 1999 SER Accepting Util 970707 Response to NRC 970509 RAI Re GL 92-08, Thermo-Lag 330-1 Fire Barriers. NRC Finds No Significant Safety Hazards Based on Application of Util Ampacity Derating Methodology ML20198M3431998-12-28028 December 1998 SER Accepting Util Request for Relief from ASME Code Repair Requirements for ASME Code Class 3 Piping for South Texas Project,Unit 2 ML20198B4111998-12-15015 December 1998 Staff Evaluation Rept of Individual Plant Exam of External Events (IPEEE) Submittal on South Texas Project,Units 1 & 2 ML20198B3491998-12-15015 December 1998 Safety Evaluation Accepting Relief Request to Use ASME Section XI Code Cases 2142-1 & 2143-1 for Replacement SGs ML20195B9601998-11-0606 November 1998 Safety Evaluation Accepting Proposed long-term C/As for Assuring Operability of MSSVs ML20195C8581998-11-0505 November 1998 SER Accepting Order Approving Application Re Proposed Corporate Merger of Central & South West Corp & American Electric Power Co,Inc ML20154N3371998-10-15015 October 1998 Safety Evaluation Re Licensee Request for Deviation from Fire Protection Program Incorporating Requirements of Section III.G.2.c of 10CFR50,App R ML20237D5281998-08-21021 August 1998 Safety Evaluation Re Proposed Increase in Sf Pool Heat Loads for Plant ML20237D4931998-08-21021 August 1998 Safety Evaluation Approving Request to Use ASME Section XI Code Case N-498-1 at STP ML20249A1831998-06-11011 June 1998 SER Accepting Request for Temporary Relief from ASME Code, Section XI Requirements,To Repair Flaws in Essential Cooling Water Sys Piping ML20217Q6881998-05-0606 May 1998 Safety Evaluation Accepting Monitoring for Leakage in Normal & Alternate Charging & Auxiliary Spray Lines at STP ML20199D0251997-11-17017 November 1997 SER Accepting Relief Requests for Inservice Testing Program for Pumps & Valves ML20199B2751997-11-0606 November 1997 Safety Evaluation Accepting Methodology for Graded QA Initiative in Operations QA Description for Plant ML20149E0741997-07-14014 July 1997 Safety Evaluation of First ten-year Interval Inservice Insp Program Plan Request to Use ASME Section XI Code Case N-416-1,Houston Lighting & Power Co,South Texas Projects, Units 1 & 2 ML20141A8531997-05-12012 May 1997 Safety Evaluation Accepting Licensee Request to Use ASME Section XI Code Case N-546, Alternative Requirements for Qualification of VT-2 Exam Personnel,Section XI Div 1, for First 10-yr Interval Inservice Insp Program Plan ML20137U3811997-04-0808 April 1997 Safety Evaluation Approving Transfer of Operating Authority to New Operating Company ML20137E4861997-03-24024 March 1997 Safety Evaluation Accepting Revised Response to NRC Bulletion 88-08, Thermal Stresses in Piping Connected to Reactor Coolant Sys, for Plant,Units 1 & 2 ML20132B0561996-12-11011 December 1996 Safety Evaluation Accepting Licensee Structural Integrity & Operability Assessments ML20059B8281993-10-21021 October 1993 SER Granting Relief & Concluding That Code Required Exam Impractical to Perform to Extent Required by Code & That Limited Section XI Surface Exam Provide Results Which Demonstrated to Be Superior or Equivalent to Surface Exam ML20057A0161993-08-31031 August 1993 Safety Evaluation Concluding That Licensee Has Demonstrated That External Events Not Major Contributor to Core Damage Scenarios at Plant ML20056C3231993-05-10010 May 1993 Supplemental SE Accepting Util Responses Re Operator Response Times During Sgtr.Licensee Satisfied All Four Criteria Required to Complete NRC Review ML20127M7241993-01-19019 January 1993 SE Concluding That Relief Requests Submitted on 920507 Are Covered by Rulemaking on 920908,which Was Incorporated Into 10CFR50.55a(b) ML20059N7881990-09-24024 September 1990 Safety Evaluation Accepting Util First 10-yr Inservice Insp Plan ML20248E6151989-09-21021 September 1989 Safety Evaluation Re Deletion of Dynamic Rod Drop Test, Static Rod Cluster Control Assembly (Rcca) Drop & Rcca below-bank Position Measurement Tests.Deletion Acceptable ML20246L6511989-02-22022 February 1989 Sser Accepting Util Efforts Re Action Items 1.a & 1.b of NRC Bulletin 88-011,per NRC Findings of Westinghouse & Plant Audit ML20207M4061988-10-0505 October 1988 Safety Evaluation Granting Util 880308 & 26 Requests to Increase Spent Fuel Pool Capacity Through Use of High Density Storage Racks ML20195G5531988-06-24024 June 1988 Safety Evaluation Accepting Proposed Reracking of Util Spent Fuel Storage Pools from Criticality Standpoint.Enrichment of Fuel to 4.5 Weight % U-235 May Be in Conflict W/ 10CFR51 Table S4 & Should Be Investigated by NRC ML20149M6941988-02-23023 February 1988 Safety Evaluation Supporting Proposals Re Personnel Air Lock Seal Air Sys Isolation ML20207K1081986-12-31031 December 1986 Safety Evaluation Re Cumulative Usage Factor Criterion for Pipe Break Postulation.Proposal Not to Postulate Pipe Breaks for SI Injection Lines & Pressurizer Surge Line Approved, Pending Resolution of Confirmatory Item Re Vibratory Stress ML20154M2201986-03-0707 March 1986 SER Supporting Licensee Mods,Per Generic Ltr 83-28,Item 4.3, Reactor Trip Breaker Automatic Shunt Trip ML20138N8121985-10-30030 October 1985 SER Supporting Util 850717 Response to Generic Ltr 83-28, Items 4.1,4.2.1 & 4.2.2 Re Preventive Maint Program for Reactor Trip Breakers/Maint & Trending ML20134L5551985-07-31031 July 1985 Draft Safety Evaluation Re Elimination of Arbitrary Intermediate Pipe Breaks ML20137G8061985-07-31031 July 1985 Safety Evaluation Supporting Util Proposal for Elimination of Arbitrary Intermediate Pipe Breaks in High Energy Piping Sys from Design Considerations in SRP Section 3.6.2 ML20140B7991977-06-0606 June 1977 Safety Evaluation Supporting Subcompartment Pressure Analysis & Proposed Valve Room Design,Per Low Stress Superpipe Requirements of Branch Technical Position Meb 3-1 Re Protection Against Main Steam or Feedwater Line Breaks 1999-09-09
[Table view] Category:TEXT-SAFETY REPORT
MONTHYEARML20217K9441999-10-15015 October 1999 SER Accepting Util Alternative Proposed Relief Request RR-ENG-2-4 for Second 10-year ISI Interval at Stp,Units 1 & 2 Pursuant to 10CFR50.55a(a)(3)(i) ML20217K9151999-10-15015 October 1999 SER Authorizing Util Relief Request RR-ENG-2-3 for Second 10-year ISI Interval of Stp,Units 1 & 2 Pursuant to 10CFR50.55a(a)(3)(i) NOC-AE-000676, Monthly Operating Repts for Sept 1999 for South Texas Project,Units 1 & 2.With1999-09-30030 September 1999 Monthly Operating Repts for Sept 1999 for South Texas Project,Units 1 & 2.With ML20217D0531999-09-30030 September 1999 Rev 1 to STP Electric Generating Station Unit 2 Cycle 7 Colr ML20217D0481999-09-30030 September 1999 Rev 1 to STP Electric Generating Station Unit 1 Cycle 9 Colr ML20211P8411999-09-0909 September 1999 Safety Evaluation Supporting Alternative Proposed by Licensee to Surface Exam to Perform Boroscopic VT-1 Visual Exam of Pump Casing Welds within Pump Pits for Welds Covered by Relief Request RR-ENG-24 ML20211P7811999-09-0909 September 1999 SER Approving Second 10-year Interval Inservice Insp Program Plan Relief Request RR-ENG-2-8 (to Use Code Case N-491-2) for South Texas Project,Units 1 & 2 ML20211Q6731999-09-0909 September 1999 Safety Evaluation Accepting First 10-yr Interval ISI Program Plan Request for Relief from ASME Code Case N-498 NOC-AE-000643, Monthly Operating Repts for Aug 1999 for South Texas Project,Units 1 & 2.With1999-08-31031 August 1999 Monthly Operating Repts for Aug 1999 for South Texas Project,Units 1 & 2.With ML20212E5191999-08-31031 August 1999 Rev 3 to SG-99-04-005, STP 1RE08 Outage Condition Monitoring Rept & Final Operational Assessment ML20211F4531999-08-24024 August 1999 Safety Evaluation Supporting Licensee Proposed Alternative to Defer Partial First Period Exams of flange-to-shell Weld to Third Period & Perform Required Ultrasonic Exams,Both Manual & Automated,During Third Period ML20211F5111999-08-23023 August 1999 Safety Evaluation Supporting Licensee Proposed Alternative Contained in Request for Relief RR-ENG-30 ML20210C9411999-07-31031 July 1999 Rev 1 to SG-99-07-002, South Tx,Unit 1 Cycle 9 Voltage- Based Repair Criteria 90-Day Rept, Jul 1999 ML20210R3631999-07-31031 July 1999 Monthly Operating Repts for July 1999 for South Tx Project, Units 1 & 2.With ML20210D9161999-07-23023 July 1999 Safety Evaluation Accepting Inservice Testing Relief Request RR-56 Re Component Cooling Water & Safety Injection Sys Containment Isolation Check Valve Closure Test Frequency ML20210D4821999-07-21021 July 1999 1RE08 ISI Summary Rept for Steam Generator Tubing of South Texas Project Electric Generating Station Unit 1 ML20210D4491999-07-21021 July 1999 Revised Chapters to Operations QA Plan, Including Rev 9 to Chapter 1.0, Organization & Rev 6 to Chapter 16.0, Independent Technical Review NOC-AE-000583, LER 99-S03-00:on 990619,failure to Revitalize Sdg Number 11 Was Noted.Caused by Failure to Communicate Status of Sdg. Subject Sdg Revitalized on 990619 & Licensee Will Develop Security Force Instruction Re Sdgs.With1999-07-15015 July 1999 LER 99-S03-00:on 990619,failure to Revitalize Sdg Number 11 Was Noted.Caused by Failure to Communicate Status of Sdg. Subject Sdg Revitalized on 990619 & Licensee Will Develop Security Force Instruction Re Sdgs.With ML20207H6361999-07-0808 July 1999 Safety Evaluation Approving 2nd 10 Yr Interval ISI Program Plan Request to Use ASME Section XI Code Case N-546 for Licenses NPF-76 & NPF-80,respectively ML20216D7481999-07-0707 July 1999 1RE08 ISI Summary Rept for Welds & Component Supports of STP Electric Generating Station,Unit 1 NOC-AE-000593, Monthly Operating Repts for June 1999 for Stp,Units 1 & 2. with1999-06-30030 June 1999 Monthly Operating Repts for June 1999 for Stp,Units 1 & 2. with NOC-AE-000570, LER 99-S01-00:on 990527,discovered That Unescorted Access Had Been Inappropriately Granted.Caused by Failure to Follow Procedure.Util Verified That Individual Did Not Have Current Unescorted Access at STP or Any Other Util.With1999-06-28028 June 1999 LER 99-S01-00:on 990527,discovered That Unescorted Access Had Been Inappropriately Granted.Caused by Failure to Follow Procedure.Util Verified That Individual Did Not Have Current Unescorted Access at STP or Any Other Util.With ML20196G5821999-06-23023 June 1999 LER 99-S02-00:on 990601,failure to Maintain Positive Control of Vital Area Security Key Was Noted.Caused by Lack of Attention to Detail.Discussed Event with Operator Involved IAW Constructive Discipline Program ML20195J6871999-06-17017 June 1999 Safety Evaluation Supporting Proposed Alternative Contained in RR-ENG-2-5.Proposed Alternative Authorized Per 10CFR50.55a(a)(3)(i) for 2nd ISI Interval ML20196A2391999-06-15015 June 1999 Change QA-042 to Rev 13 of Operations QAP, Reflecting Current Organizational Alignment for South Texas Project & Culminating Organizational Realigment That Has Been Taking Place During Past Several Months NOC-AE-000563, Monthly Operating Repts for May 1999 for Stp,Units 1 & 2. with1999-05-31031 May 1999 Monthly Operating Repts for May 1999 for Stp,Units 1 & 2. with ML20206U5411999-05-18018 May 1999 Non-proprietary Errata Pages for Rev 2,Addendum 1 to WCAP-13699, Laser Welded Sleeves for 3/4 Inch Diamete Tube Feedring Type & W Preheater SGs Generic Sleeving Rept ML20206A7721999-04-30030 April 1999 STP Electric Generating Station Unit 1 Cycle 9 Colr NOC-AE-000543, Monthly Operating Repts for Apr 1999 for Stp,Units 1 & 2. with1999-04-30030 April 1999 Monthly Operating Repts for Apr 1999 for Stp,Units 1 & 2. with ML20205H0321999-03-31031 March 1999 Change QA-040 to Rev 13 of Operations QA Plan NOC-AE-000507, Monthly Operating Repts for Mar 1999 for Stp,Units 1 & 2. with1999-03-31031 March 1999 Monthly Operating Repts for Mar 1999 for Stp,Units 1 & 2. with ML20205A3781999-03-22022 March 1999 STP Electric Generating Station Simulator Certification Four Yr Rept for Units 1 & 2 ML20204B2711999-03-15015 March 1999 Safety Evaluation Authorizing 990201 Request to Authorize Alternative to Regulations Per 10CFR50.55a(a)(3)(i) That Would Revise Start of Second 120-month IST Interval to No Later than 011201 ML20207M9231999-03-12012 March 1999 Amended Part 21 Rept Re Cooper-Bessemer Ksv EDG Power Piston Failure.Total of 198 or More Pistons Have Been Measured at Seven Different Sites.All Potentially Defective Pistons Have Been Removed from Svc Based on Encl Results NOC-AE-000468, Monthly Operating Repts for Feb 1999 for South Texas Project Electric Generating Station.With1999-02-28028 February 1999 Monthly Operating Repts for Feb 1999 for South Texas Project Electric Generating Station.With ML20207D1101999-02-24024 February 1999 Change QA-039 to Rev 13 of Operations QA Plan, for STP ML20203H8361999-02-17017 February 1999 Safety Evaluation Supporting Request for Relief from ASME Code Requirements for Class 3 Piping for Plant ML20202H9621999-02-0303 February 1999 SER Accepting Change to EALs Used in Classification of Emergency Conditions ML20202E8471999-01-31031 January 1999 2RE06 ISI Summary Rept for SG Tubing of STP Electric Generating Station,Unit 2 ML20216G2011999-01-31031 January 1999 City Public Svc of San Antonio Annual Rept 1998-1999 ML20199G5961999-01-31031 January 1999 Cycle 7 Voltage-Based Repair Criteria Rept for Jan 1999 ML20199K7711999-01-21021 January 1999 Safety Evaluation Accepting ISI Program Request for Relief for ASME Cose Repair Requirements for Code Class 3 Piping ML20199G8161999-01-19019 January 1999 SER Accepting Util 970707 Response to NRC 970509 RAI Re GL 92-08, Thermo-Lag 330-1 Fire Barriers. NRC Finds No Significant Safety Hazards Based on Application of Util Ampacity Derating Methodology ML20199H4981999-01-11011 January 1999 2RE06 ISI Summary Rept for Welds & Component Supports of Stp,Unit 2 ML20206Q3751999-01-0404 January 1999 2RE06 ISI Summary Rept for Sys Pressure Tests (Class 1 & 2) ML20206Q3721999-01-0404 January 1999 2RE06 ISI Summary Rept for Repairs & Replacements ML20216G2171998-12-31031 December 1998 Houston Industries 1998 Annual Rept. App a 1998 Financial Statements & Us Securities & Exchange Commission Form 10-K Encl NOC-AE-000403, Monthly Operating Repts for Dec 1998 for South Texas Project Unit 1 & 2.With1998-12-31031 December 1998 Monthly Operating Repts for Dec 1998 for South Texas Project Unit 1 & 2.With ML20216G1521998-12-31031 December 1998 Central & South West Corp 1998 Summary Annual Rept & Securities & Exchange Commission Form 10-K ML20198M3431998-12-28028 December 1998 SER Accepting Util Request for Relief from ASME Code Repair Requirements for ASME Code Class 3 Piping for South Texas Project,Unit 2 1999-09-09
[Table view] |
Text
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/ E UNITED STATES
. ! NUCLEAR REGULATORY COMMISSION
<;p g ..v;4y/ WASHINGTON, D.C. 20555-0001
... 4 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO THE INSERVICE INSPECTION PROGRAM RELIEF REQUESTS HOUSTON LIGHTING & POWER COMPANY SOUTH TEXAS PROJECT. UNITS 1 AND 2 DOCKET NOS. 50-498 AND 50-499 1.0 MIE90VCTION ;
Technical Specification 4.0.5 for South Texas Project, Units 1 and 2, states l that the inservice inspection and testing of the American Society of !
Mechanical Engineers (ASME) Code Class 1, 2, and 3 components shall be performed in accordance with Section XI of the ASME Boiler and Pressure Vessel Code and applicable Addenda as required by.10 CFR 50.55a(g), except where specific written relief has been granted by the Commission pursuant to 10 CFR 50.55a(g)(6)(i). 10 CFR 50.55a(a)(3) states that alternatives to the requirements of paragraph (g) may be used, when authorized by the NRC, if (i) the proposed alternatives would provide an acceptable level of quality and safety, or (ii) compliance with the specified requirements would result in hardship or unusual difficulties without a compensating increase in the level of quality and safety.
Pursuant to 10 CFR 50.55a(c.)(4), ASME Code Class 1, 2, and 3 components (including sLpports) shall meet the requirements, except the design and access provisions and the preservice examination requirements, set forth in the ASME Code,Section XI, " Rules for Inservice Inspection of Nuclear Power Plant ,
Components," to the extent practical within the limitations of design, l geometry, and materials of construction of the components. The regulations I require that inservice examination of components and system pressure tests I conducted during the first ten-year interval comply with the requirements in the latest edition and addenda of Section XI of the ASME Code incorporated by reference in 10 CFR 50.55a(b) on the date twelve months prior to issuance of the operating license, subject to the limitations and modifications listed therein. The applicable edition of Section XI of the ASME Code for the South Texas Project, Units I and 2, first 10-year inservice inspection (ISI) interval is the 1983 Edition, through Summer 1983 Addenda. The components (including supports) may meet the requirements set forth in subsequent editions and addenda of the ASME Code incorporated by reference in 10 CFR 50.55a(b) subject to the limitations and modifications listed therein. ,
1 Pursuant to 19 CFR 50.55a(g)(5), if the licensee determines that conformance with an examination requirement of Section XI of the ASME Code is not practical for its facilities, information shall be submitted to the Commission in support of that determination and a request made for relief from the ASME Code requirement. After evaluation of the determination, pursuant to '
10 CFR 50.55a(g)(6)!i), the Commission may grant relief and may impose 9310290109 931021
l
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alternative requirements that are determined to be authorized by law, will not endanger life, property, or the' common defense and security, and are otherwise '
in the public interest, giving due consideration to the burden upon the licensee that could result if the requirements were imposed.
The licensee, Houston Lighting & Power (HL&P), submitted Relief Request No. RR-ENG-12, by letter dated December 9, 1992, for the first 10-year ISI interval, which began August 25, 1988 (Unit 1) and June 19, 1989 (Unit 2).
The staff, with technical assistance from its contractor, the Idaho National Engineering Laboratory (INEL), has evaluated the subject request for relief in the following section.
2.0 DISCUSSION The information provided by the licensee in support of the request for relief from impractical requirements has been evaluated and the bases for granting relief from those requirements are documented below.
Reauest for Relief No. RR-ENG-12 (Units 1 & 2). Examination CateaorY 1 B-G-1. Item B6.10. Reactor Vessel Closure Head Nuts Code Reauirement: Table IWB-2500-1, Exa.mination Category B-G-1, Item Number B6.10 requires a 100 percent surface examination of all reactor vessel (RV) closure head nuts during the 10-year interval.
Licensee's Code Relief Reauest: Relief is requested from the surface examination requirements for the inside surface (threaded area) of the reactor vessel closure head nuts. The licensee states that although there is no description or figure referenced in Section XI depicting the area of the examination, it has been interpreted to include all surfaces of the nut (i.e.,
top, bottom, outside, inside threads).
Licensee's Basis for Reauestina Relief: The licensee states that typically a fluorescent magnetic particle (MT) examination is performed on threaded areas because of its suitability for revealing relevant indications in the root of the thread. Due to the poor viewing angle and limited access to the threaded surface with the MT equipment and black light, a meaningful MT examination can not be performed.
1 Licensee's Proposed Alternative Examination: The licensee will conduct an NT 1 examination on the outside surfaces of the RV nuts. In lieu of the Code- l required surface examination of the threaded surfaces of the RV nut, the licensee will perform an ultrasonic (UT) examination of the threaded region from the outside and end surfaces of the nut. The UT examination provides coverage of the thread root area in two directions. A 0-degree UT (UTC) examination is performed 360 degrees around the nut end surface to examine the threaded area for circumferential flaws. A 43-degree UT (UT43) I examination from the outside surface is used to examine the threaded area in l clockwise and counterclockwise directions to detect axial flaws.
1 l
d
. ~
g 4 A spare RV nut will be used for the calibration block. Circumferential notches cut 0.115 inch deep and an axial notch cut through the threads to the -
thread root will be used to establish the sensitivity for the UT examinations.
No limitations are encountered with the UTO examinations. Scanning for the UT43 examinations is limited by the six wrench slots located on the upper end of the nut. These slots reduce the UT43 coverage of the threaded region by approximately 7.5 percent.
3.0 EVALUAIJ03 The Code requires a surface examination of all surfaces associated with the reactor vessel head closure nuts. As a result of the nut design, it is impractical to perform a meaningful surface examination of the threaded region. The UT43 examination is sensitive to critical, axially orientated fl aws. The combined UT43 and UTO examinations provide a qualitative examination of the nut inside thread region. Imposition of the Code requirement on the licensee would cause a burden because redesign or replacement of the nut would be required in order to yield meaningful results.
In addition, in NRC Inspection Report 50-498/92-28; 50-499/92-28 dated October 28, 1992, the inspector discusses his c'. syations and findings regarding the licensee's proposed alternative m nation. The inspector found that based on the observed sensitivi* , , was achieved in calibration of the ultrasonic equipment, he considerN ' na ultrasonic examination method to be an acceptable alternative to surfac6 examination of the inner diameter surface of the reactor vessel closure head nuts.
The licensee's proposed UT technique, in addition to the surface examination of the accessible surfaces of the reactor pressure vessel head closure nuts, provides an acceptable level of quality and assurance of the nut (s) structural .
integrity. The proposed UT technique may be substituted for the surface i examination of the nut thread region provided the results are demonstrated to be equivalent or superior to those of the surface examination. Based on the above and pursuant to 10 CFR 50.55a(g)(6)(1), relief may be granted as l requested. ,
4.0 CONCLUSION
Based on the above evaluation, it is concluded that the Code-required examination is impractical to perform to the extent required by the Code and that the limited Section XI surface examination, in conjunction with the proposed volumetric examination, provide results which are demonstrated to be equivalent or superior to those of a surface examination. The staff has determined that granting relief, pursuant to 10 CFR 50.55a(g)(6)(1) is authorized by law and will not endanger life or property, or the common defense and security and is otherwise in the public interest.
Principal Contributor: T. K. McLellan Date: October 21, 1993