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Category:CORRESPONDENCE-LETTERS
MONTHYEARML20138H3831999-10-25025 October 1999 Forwards Draft Model of Renewed License for Calvert Cliffs, Unit 2 to Illustrate How List of Minimum Requirements Could Be Incorporated Into License Condition ML20217M9991999-10-22022 October 1999 Forwards Response to NRC 990930 RAI Re Void Swelling Degradation Mechanism,Per License Renewal Application for Ccnpp,Units 1 & 2 ML20217M1721999-10-19019 October 1999 Forwards NRC Rept Number 17, Requal Tracking Rept Form Operator Licensing Tracking Sys.Rept Was Used by NRC to Schedule Requalification Exam for Operators & Record Requal Pass Dates ML20212M2631999-10-0404 October 1999 Informs That Staff Concluded That Licensee Responses to GL 97-06 Provides Reasonable Assurance That Condition of Util SG Internals in Compliance with Current Licensing Bases for Calvert Cliffs Nuclear Power Plant ML20216J8671999-10-0101 October 1999 Forwards Rev 52 to QA Policy for Calvert Cliffs Nuclear Power Plant. Rev Accurately Presents Changes Made Since Previous Submittal,Necessary to Reflect Info & Analyses Submitted to NRC or Prepared,Per to NRC Requirements ML20212J7811999-09-30030 September 1999 Requests That Licensee Address Potential Aging Mgt Issue Re Effects of Void Swelling of Rv Internals by Making Plant Specific Commitment to Implement Focused age-related Degradation Insp for Evidence of Void Swelling in Future ML20212J5611999-09-29029 September 1999 Informs That on 990916,NRC Completed mid-cycle Plant Performance Review of Calvert Cliffs.No Areas in Which Util Performance Warranted Addl Insp Beyond Core Insp Program Identified.Historical Listing of Plant Issues,Encl ML20216H7831999-09-28028 September 1999 Forwards Addl Info Re NRC SER for Ccnpp,Units 1 & 2,per License Renewal Application ML20212D5361999-09-20020 September 1999 Forwards Rev 1 to Calculation CA04048, Fuel Handling Accident During Reconstitution, as Agreed During 990909 Telcon ML20212C1861999-09-15015 September 1999 Requests That NRC Complete Review of TR CED-387-P,Rev 00-P, Abb Critical Heat Flux Correlations for PWR Fuel, by 000201.Util Expects to Use ABB-NV Correlation for Current non-mixing Vane Fuel in Reload Analyses in 2000 for Ccnpp ML20212A2001999-09-0808 September 1999 Forwards Insp Repts 50-317/99-06 & 50-318/99-06.Two Violations Being Treated as Noncited Violations ML20211N8971999-09-0707 September 1999 Responds to Ltr to D Rathbun of NRC Dtd 990720,in Which Recipient Refers to Ltr from Wc Batton Expressing Support on Renewal Application of Baltimore Gas & Electric Co for Calvert Cliffs Plants ML20211H9841999-08-31031 August 1999 Provides Comments Re Data Entered in Rvid for Ccnpp,Units 1 2,per GL 92-01,Rev 1,Suppl 1, Reactor Vessel Structural Integrity ML20211K3091999-08-27027 August 1999 Informs That During 990826 Telcon,L Briggs & B Bernie Made Arrangements for NRC to Inspect Licensed Operator Requalification Program at Calvert Cliffs Npp.Insp Planned for Wk of 991025 ML20211J1611999-08-17017 August 1999 Documents Bg&E Consultations with MD Dept of Natural Resources Re Potential Impacts to Chesapeake Bay Critical Area & Forest Interior Dwelling Bird Habitat,Per Ccnpp License Renewal.Telcons Ref Satisfy Consulting Requirement ML20210V1181999-08-17017 August 1999 Forwards Toxic Gases Calculations for Control Room Habitability,As Discussed During 990713 Telcon.Util Will Make Final Submittal for Toxic Gases After NRC Has Completed Review of ARCON96 ML20210T5061999-08-16016 August 1999 Forwards Rev 0 to Ccnpp COLR for Unit 2,Cycle 13, Per Plant TS 5.6.5 ML20210U2761999-08-13013 August 1999 Forwards Listed Info Re Guarantee of Payment of Deferred Premiums for Ccnpp,Units 1 & 2,IAW 10CFR140.21 Requirements ML20210S8101999-08-12012 August 1999 Forwards Application Requesting Renewal of License for Mv Seckens,License SOP-10369-2.Without Encl ML20210S8131999-08-12012 August 1999 Forwards Summary of Various Open Licensing Actions for Bg&E That Were Completed During Unit 2 Refueling Outage Ending 990506 ML20210S7901999-08-12012 August 1999 Forwards semi-annual Fitness for Duty Program Performance Data for Period of 990101-990630,IAW 10CFR36.71(d) ML20210Q1941999-08-11011 August 1999 Informs That Info Submitted in 981130 Application Re CEN-633-P,Rev 03-P,dtd Oct 1998,marked Proprietary,Will Be Withheld from Public Disclosure,Per 10CFR2.790(b)(5) & Section 103(b) of AEA of 1954,as Amended ML20210N5881999-08-0606 August 1999 Forwards ISI Rept for Ccnpp,Unit 2,fulfilling Intentions & Requirements Stated in Program Plan & Commitment to Comply with ASME Code Section XI ISI Requirements ML20210N5471999-08-0505 August 1999 Requests That License SOP-10031-3,for DF Theders,Be Removed from Active Files for Ccnpp,Due to Individual Being Reassigned to Position No Longer Requiring License ML20210N5491999-08-0505 August 1999 Requests That License SOP-10371-2,for RW Scott,Be Renewed IAW 10CFR55.57.Individual Has Satisfactorily Discharged License Responsibilities Competently & Safely.Without Application ML20210N1291999-08-0505 August 1999 Forwards NRC Response to W Batton Ltr Expressing Support of Renewal Application for Calvert Cliffs Plants as Requested in Ltr ML20210N9291999-08-0404 August 1999 Forwards Clarification to Initial Response to Biennial Rept on Status of Decommissioning Funding,As Required by 10CFR50.75(f)(1) ML20211C0951999-07-30030 July 1999 Expresses Appreciation for Participation in Y2K Training & Tabletop Exercise Held on 990714 ML20211B5381999-07-30030 July 1999 Expresses Appreciation for Support in Y2K Training & Tabletop Exercise Held on 990714.Suggests Referral to NRC Y2K Web Site to View Issues & Lessons from Tabletop That Will Be Tracked by NRC ML20210J0741999-07-30030 July 1999 Expresses Appreciation for Participation in Y2K Training & Tabletop Exercise on 990714.Suggests Referral to NRC Y2K Web Site to View Issues & Lessons from Tabletop That Will Be Tracked by Nrc.Web Site Should Reflect Info within 2 Wks ML20211C3251999-07-30030 July 1999 Expresses Appreciation for Participation in Y2K Training & Tabletop Exercise Held on 990714 ML20210E4941999-07-23023 July 1999 Informs That 1999 Emergency Response Plan Exercise Objectives Is Scheduled for Wk of 991025.Exercise Scenario Will Test Integrated Capability & Major Portion of Elements Existing within Emergency Response Plan ML20210D0911999-07-22022 July 1999 Responds to to Chairman Jackson Referring to Ltr from New 7th Democratic Civic Club,Inc.Forwards Staff Response to W Batton,President of New 7th Democratic Civic Club,Inc ML20210C5011999-07-21021 July 1999 Informs That SL Walters,License OP-10096-3 & CC Zapp,License Number SOP-2188-9,have Been Reassigned within Organization & No Longer Require NRC License,Per 10CFR50.74(a).Removal of Subject Licenses from Active Files for Ccnpp,Requested ML20210A5021999-07-20020 July 1999 Responds to ,Expressing Support for Renewal of Operating Licenses for Calvert Cliffs Plant & to Concerns Re Lack of Specificity for License Renewal Regulations & Length of Time Set Aside for Public Comment ML20211N9101999-07-20020 July 1999 Forwards Correspondence Author Received from New 7th Democratic Club Civic,Inc Raising Some Serious Concerns About Renewal of Nuclear Reactor Licenses for Calvert Cliffs Power Plant ML20210C2681999-07-20020 July 1999 Forwards Certified Copy of Listed Nuclear Liability Policy Endorsement,Per 10CFR140.15(e) ML20210C8461999-07-19019 July 1999 Informs That CF Farrow,License OP-10648-1,will No Longer Be Employed with Bg&E,As of 990709,per 10CFR50.74(a).Removal of Subject License from Active Files for Ccnpp,Requested ML20209J5171999-07-16016 July 1999 Forwards Comments from Accuracy Review of License Renewal Application SER ML20210B7651999-07-15015 July 1999 Forwards SER Denying Licensee Proposed TS Amend Dtd 981120, to Delete TS Requirements for Tendon Surveillance & Reporting Because TS Requirements Duplication of Requirements in 10CFR50.55a.Notice of Denial Encl ML20209G2081999-07-13013 July 1999 Forwards Insp Repts 50-317/99-05 & 50-318/99-05 on 990509- 0626.No Violations Noted ML20210A6311999-07-0606 July 1999 Discusses Closure of TACs MA0532 & MA0533 Re Response to Requests for Addl Info to GL 92-01,rev1,suppl 1, Reactor Vessel Structural Integrity, for Plant,Units 1 & 2 ML20209C1391999-07-0202 July 1999 Forwards Responses to Open & Confirmatory Items Based on Review of SER for Bg&E Application for Renewal of Operating Licenses for Calvert Cliffs.Bg&E Intends to Forward Comments Based on Accuracy Verification in Near Future ML20210D1531999-06-30030 June 1999 Informs of Receipt of from New 7th Democratic Civic Club,Inc Expressing Support for License Renewal. Requests Consideration in Addressing Concerns & Recommendations ML20209B5781999-06-29029 June 1999 Submits Response to GL 98-01, Y2K Readiness of Computer Sys at Nuclear Power Plants. GL 98-01 Requested Response on Status of Facility Y2K Readiness by 990701.Disclosure Encl ML20210D1741999-06-24024 June 1999 Expresses Opinions on Renewal of Nuclear Reactor Licenses Re Plant & Support Renewal Application of Bg&E.Requests That NRC Revise Procedures to Allow Sufficient Time for Public to Review,Evaluate & Respond to Info ML20211H8431999-06-23023 June 1999 Ack Participation of Calvert Cliffs Nuclear Engineering Dept in NRC Cooperative Research Project with Univ of Virginia. Copy of Relevant Portion of NRC Cooperative Agreement with Univ of Virginia Encl ML20196C6831999-06-21021 June 1999 Discusses Proposed Alternative Submitted by Bg&E for Calvert Cliffs NPP to Requirements of 10CFR50.55a(g)(4) in Regard to Compliance with Latest Approved Edition of ASME Code,Section XI for Third Ten Year Insp Interval Beginning on 990701 ML20196C4291999-06-21021 June 1999 Forwards Rev to ERDS Data Point Library for Ccnpp,Unit 2,per 10CFR50,App E,Section VI.3.a.Table Provides Brief Summary of Changes ML20195J8271999-06-16016 June 1999 Ack Receipt of to Jackson,Chairman of NRC Re Environ Impacts of Increased Patuxtent River Complex Flight Operations on Ccnpp.Clarification & Correction of Listed Statement Found on Page Two,Provided 1999-09-08
[Table view] Category:INCOMING CORRESPONDENCE
MONTHYEARML20217M9991999-10-22022 October 1999 Forwards Response to NRC 990930 RAI Re Void Swelling Degradation Mechanism,Per License Renewal Application for Ccnpp,Units 1 & 2 ML20216J8671999-10-0101 October 1999 Forwards Rev 52 to QA Policy for Calvert Cliffs Nuclear Power Plant. Rev Accurately Presents Changes Made Since Previous Submittal,Necessary to Reflect Info & Analyses Submitted to NRC or Prepared,Per to NRC Requirements ML20216H7831999-09-28028 September 1999 Forwards Addl Info Re NRC SER for Ccnpp,Units 1 & 2,per License Renewal Application ML20212D5361999-09-20020 September 1999 Forwards Rev 1 to Calculation CA04048, Fuel Handling Accident During Reconstitution, as Agreed During 990909 Telcon ML20212C1861999-09-15015 September 1999 Requests That NRC Complete Review of TR CED-387-P,Rev 00-P, Abb Critical Heat Flux Correlations for PWR Fuel, by 000201.Util Expects to Use ABB-NV Correlation for Current non-mixing Vane Fuel in Reload Analyses in 2000 for Ccnpp ML20211H9841999-08-31031 August 1999 Provides Comments Re Data Entered in Rvid for Ccnpp,Units 1 2,per GL 92-01,Rev 1,Suppl 1, Reactor Vessel Structural Integrity ML20210V1181999-08-17017 August 1999 Forwards Toxic Gases Calculations for Control Room Habitability,As Discussed During 990713 Telcon.Util Will Make Final Submittal for Toxic Gases After NRC Has Completed Review of ARCON96 ML20210T5061999-08-16016 August 1999 Forwards Rev 0 to Ccnpp COLR for Unit 2,Cycle 13, Per Plant TS 5.6.5 ML20210U2761999-08-13013 August 1999 Forwards Listed Info Re Guarantee of Payment of Deferred Premiums for Ccnpp,Units 1 & 2,IAW 10CFR140.21 Requirements ML20210S7901999-08-12012 August 1999 Forwards semi-annual Fitness for Duty Program Performance Data for Period of 990101-990630,IAW 10CFR36.71(d) ML20210S8131999-08-12012 August 1999 Forwards Summary of Various Open Licensing Actions for Bg&E That Were Completed During Unit 2 Refueling Outage Ending 990506 ML20210S8101999-08-12012 August 1999 Forwards Application Requesting Renewal of License for Mv Seckens,License SOP-10369-2.Without Encl ML20210N5881999-08-0606 August 1999 Forwards ISI Rept for Ccnpp,Unit 2,fulfilling Intentions & Requirements Stated in Program Plan & Commitment to Comply with ASME Code Section XI ISI Requirements ML20210N5491999-08-0505 August 1999 Requests That License SOP-10371-2,for RW Scott,Be Renewed IAW 10CFR55.57.Individual Has Satisfactorily Discharged License Responsibilities Competently & Safely.Without Application ML20210N5471999-08-0505 August 1999 Requests That License SOP-10031-3,for DF Theders,Be Removed from Active Files for Ccnpp,Due to Individual Being Reassigned to Position No Longer Requiring License ML20210N9291999-08-0404 August 1999 Forwards Clarification to Initial Response to Biennial Rept on Status of Decommissioning Funding,As Required by 10CFR50.75(f)(1) ML20210E4941999-07-23023 July 1999 Informs That 1999 Emergency Response Plan Exercise Objectives Is Scheduled for Wk of 991025.Exercise Scenario Will Test Integrated Capability & Major Portion of Elements Existing within Emergency Response Plan ML20210C5011999-07-21021 July 1999 Informs That SL Walters,License OP-10096-3 & CC Zapp,License Number SOP-2188-9,have Been Reassigned within Organization & No Longer Require NRC License,Per 10CFR50.74(a).Removal of Subject Licenses from Active Files for Ccnpp,Requested ML20211N9101999-07-20020 July 1999 Forwards Correspondence Author Received from New 7th Democratic Club Civic,Inc Raising Some Serious Concerns About Renewal of Nuclear Reactor Licenses for Calvert Cliffs Power Plant ML20210C2681999-07-20020 July 1999 Forwards Certified Copy of Listed Nuclear Liability Policy Endorsement,Per 10CFR140.15(e) ML20210C8461999-07-19019 July 1999 Informs That CF Farrow,License OP-10648-1,will No Longer Be Employed with Bg&E,As of 990709,per 10CFR50.74(a).Removal of Subject License from Active Files for Ccnpp,Requested ML20209J5171999-07-16016 July 1999 Forwards Comments from Accuracy Review of License Renewal Application SER ML20209C1391999-07-0202 July 1999 Forwards Responses to Open & Confirmatory Items Based on Review of SER for Bg&E Application for Renewal of Operating Licenses for Calvert Cliffs.Bg&E Intends to Forward Comments Based on Accuracy Verification in Near Future ML20210D1531999-06-30030 June 1999 Informs of Receipt of from New 7th Democratic Civic Club,Inc Expressing Support for License Renewal. Requests Consideration in Addressing Concerns & Recommendations ML20209B5781999-06-29029 June 1999 Submits Response to GL 98-01, Y2K Readiness of Computer Sys at Nuclear Power Plants. GL 98-01 Requested Response on Status of Facility Y2K Readiness by 990701.Disclosure Encl ML20210D1741999-06-24024 June 1999 Expresses Opinions on Renewal of Nuclear Reactor Licenses Re Plant & Support Renewal Application of Bg&E.Requests That NRC Revise Procedures to Allow Sufficient Time for Public to Review,Evaluate & Respond to Info ML20196C4291999-06-21021 June 1999 Forwards Rev to ERDS Data Point Library for Ccnpp,Unit 2,per 10CFR50,App E,Section VI.3.a.Table Provides Brief Summary of Changes ML20195J6591999-06-16016 June 1999 Submits Proposed Alternative to Requirements of 10CFR50.55a(g)(4) (Automatic Compliance with Latest Approved Edition of ASME Code Every 120 Months).Proposal Will Apply Third ten-year ISI Interval,Scheduled to Begin 990701 ML20207F0201999-06-0101 June 1999 Forwards Third Interval Inservice Insp Program Plan for Ccnpp,Units 1 & 2, for NRC Review.Plan Satisfies Commitment Contained in Licensee to NRC 05000317/LER-1999-002, Requests That Cover Page for LER 99-002,dtd 990525,be Corrected to Indicate Rept Is Submitted Per Requirements of 10CFR20.2201(b)1999-05-28028 May 1999 Requests That Cover Page for LER 99-002,dtd 990525,be Corrected to Indicate Rept Is Submitted Per Requirements of 10CFR20.2201(b) ML20195B3751999-05-25025 May 1999 Forwards ECCS Codes & Methods Rept, as Required by 10CFR50.46(a)(3)(ii) ML20195B2521999-05-25025 May 1999 Submits Response to RAI Re LAR for Tube Repair Using Leak Limiting Alloy 800 Sleeves for Ccnpp,Units 1 & 2.Test Repts Encl ML20195B2271999-05-24024 May 1999 Forwards Certified Copy of Nuclear Liability Policy NF-216, Endorsement 128 ML20206U3051999-05-19019 May 1999 Submits Written Rept as Required follow-up to Verbal Rept Given to NRC Regional Administrator on 990419 of SG Tube Insps Conducted,Cause of Tube Degradation & Corrective Measures Taken as Result of Insp Findings ML20206U8281999-05-18018 May 1999 Forwards Missing Pages C-30,C-31,C-114 & C-115 from 990319 Response to NRC RAI, Wind Tunnel Modeling of Calvert Cliffs NPP Cpp Project 94-1040. Complete Copy of 1985 Rept, Wind Flows & Dispersion Conditions of Calvert Cliffs, Encl ML20212G9751999-05-12012 May 1999 Forwards Draft write-up Re OI 16 for F Grubelich to Consider ML20206K6921999-05-10010 May 1999 Forwards Certified Copy of Listed Nuclear Liability Policy Endorsements,In Compliance with 10CFR140.15(e).Without Encl ML20206K1711999-05-0707 May 1999 Informs That on 990430 Util Filed Encl Articles of Share Exchange with Maryland Dept of Assessments & Taxation to Form Holding Company,Constellation Energy Group,Inc (Ceg). CEG Is Parent Company of Bg&E ML20206C7521999-04-29029 April 1999 Provides Rept of Number of Tubes Plugged in Calvert Cliffs Unit 2 SGs During Recently Completed Isi,As Required by Calvert Cliffs Unit 1,TS 5.6.9.a ML20212G9891999-04-28028 April 1999 Forwards Current Draft Response to Ci 3.3.2.2-1 to Be Used as Example for OI Vs License Condition Vs Commitment Situation ML20206C7271999-04-28028 April 1999 Forwards Occupational Radiation Exposure Repts for 1998, as Required by Units 1 & 2 Tech Specs 5.6.1 & 6.1 of Isfsi. Repts Contain Tabulation of Number of Station,Util & Other Personnel Receiving Exposures Greater than 100 Mrem ML20206C7211999-04-27027 April 1999 Forwards Addl Info Which Is Being Made Available in Encl Licensed Operators Fitness for Duty Questionnaire.Encl Specifics of Personal Info Are Withheld,Per 10CFR2.790 ML20212G9851999-04-26026 April 1999 Provides Proposed Response to OI 4.1.3-1 for B Elliott to Consider ML20206U6691999-04-26026 April 1999 Advises That Documents Re Operation of Calvert Cliffs Nuclear Power Plant Should Be Addressed to Listed Natl Marine Fisheries Svc Office ML20205F8851999-04-0202 April 1999 Provides First Annual Amend to Bg&E License Renewal Application for Ccnpp,Units 1 & 2,as Required by 10CFR54 ML20205J0691999-04-0202 April 1999 Forwards Response to NRC 990129 RAI Re GL 96-05, Periodic Verification of Design-Basis Capability of Safety-Related Movs ML20205G2971999-04-0101 April 1999 Requests That NRC Complete Review of Rev 0 to CENPD-396-P, Common Qualified Platform TR & Rev 0 to CE-CES-195-P, Software Program Manual for 'Common Q' Sys, by 990930 ML20205D7471999-03-30030 March 1999 Forwards Biennial Rept on Status of Decommissioning Funding, IAW 10CFR50.75(f)(1) ML20207G4391999-03-30030 March 1999 Responds to from Cl Miller,Requesting Assistance of FEMA in Addressing Concerns Received by NRC Involving Offsite Emergency Preparedness at Plant NPP ML20205C4091999-03-26026 March 1999 Submits Info Related to Scope,Risk Mgt & Summary of Risk for Performing Preventive Maintenance on P-13000-2 Unit Transformer Re License Amend 205 1999-09-28
[Table view] |
Text
PETER E. KATE Baltimore Gas and Electric Company l
Plant General Manager Calvert Cliffs Nuclear Power Plant l Calven Cliffs Nuclear Power Plant 1650 Calvert Cliffs Parkway j Lusby, Maryland 20657 1 410 495-4101 August 4,1998
- u. S. Nuclear Regulatory Commission Washington, DC 20555 ATTENTION: Document Control Desk
SUBJECT:
Calvert Cliffs Nuclear Power Plant Unit Nos.1 & 2; Docket Nos. 50-317 & 50-318 American Society of Mechanical Engineers Boiler and Pressure Vessel Code Reauired Submittal Related to the Unit 2 Pressurizer Instrument Nozzle Reoair
REFERENCE:
(a) American Society of Mechanical Engineers Boiler and Pressure Vessel Code,Section XI, Division 1,1983 Edition, through Summer 1983 Addenda In accordance with the requirement American Society of Mechanical Engineers Boiler and Pressure Vessel Code,Section XI, IWB-3610 (Reference a), Baltimore Gas and Electric Company hereby submits the attached evaluation of a postulated Haw in the weld of the Unit 2 pressurizer instrument nozzle for your review.
Should you have questions regarding this matter, we will be pleased to discuss them with you.
Very truly yours, Sa h
PEK/JKK/bjd
Attachment:
American M. ;iety of Mechanical Engineers Boiler and Pressure Vessel Code Required Evaluation Related to the Unit 2 Pressurizer Instrument Nozzle Weld Crack Repair
.T cc: (Without Attachment) 0' r 9 R. S. Fleishman, Esquire J. E. Silberg, Esquire II. J. Miller, NRC Resident inspector, NRC h
S. S. Bajwa, NRC R. I. McLean, DNR A. W. Dromeru k, NRC J. II. Walter, PSC 9808070294 980804~
PDR P ADOCK 05000318 PDR
1 ATTACHMENT American Society of Mechanical Engineers Boiler and Pressure Vessel Code Required Evaluation Related
'te the Unit 2 Pressurizer Instrument Nozzle Weld Crack Repair I
l Haltimore Gas and Electric Company Calvert Cliffs Nuclear Power Plant August 4,1998
1 l
1 MEMORANDUM l
AlechanientEngineering Unit l
TO: J. M. Osbome l
1 k
FROM: C. J. Ludlow i R. O. Hardies I &l O2 , O I4 I
SUBJECT:
- EVALUATION OF PRESSURIZER UPPER LEVEL TAP LEAK )
1 DATE: August 4,1998 )
This document provides the basis for a bounding evaluation of a postulated flaw in the pressurizer. A flaw of this magnitude was not detected and is not believed to exist. However, )
it was decided that it is appropriate to submit the analysis to the NRC since it utilizes ASME !
Boiler and Pressure Vessel Code,Section XI, Appendix A for the bounding condition.
SUMMARY
The pressurizer upper level tap at the 7-1/2" location on the Unit 2 pressurizer upper head has bee.1 found leaking. The only plausible cause of the current leakage is failure of the J-groove weld material. The most probable mechanism for failure of the weld is concluded to be Primary Water Stress Corrosion Cracking (PWSCC).
The portion of the leakage path remaining attached to the pressurizer shell has been evaluated and does not present a challenge to the long term structural integrity of the shell.
I. DESCRIPTION OF EVENT A. INITIAL DISCOVERY At approximately 1700 hours0.0197 days <br />0.472 hours <br />0.00281 weeks <br />6.4685e-4 months <br /> on July 25,1998, during a walkdown in the Unit 2 pressurizer doghouse an operator heard the sound of a steam leak coming from the 71\2 pressurizer upper level tap (Instrument nozzle 2-LT-110-X). The leakage identified was considered Reactor Coolant System (RCS) pressure boundary leakage. Technical Specification 3.4.6.2 requires that RCS leakage includes no pressure boundary leakage. This Technical Specification is applicable in MODES 1-4 and the Action requirement requires taking the plant to cold shutdown. At the time of discovery Unit 2 was in hot standby (MODE 3). The Unit was promptly brought to MODE 5. On July 26,1998 the location of the small steam plume was confirmed coming from the annular region between the 7-l/2' nozzle and the bore thr6 ugh the pressurizer shell.
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! B. EQU)PMENT DESCRIPTION The level tap instrument nozzles extend through a 1.325 inch diameter horizontal penaration in the upper head of the pressurizer. The upper head is a 48-7/16 inch Uside radius hemispherical head fabricated from A-533, Grade B, Class I steel. The upper head is 3-7/8 inch thick A stainless steel weld overlay,1/8 inch minimum thickness, was applied to the inside surface of the upper head. The inside of the vessel around the penetration holes for the instrument nozzles were machined to prepare for welding the nozzles at the inside of the vessel. The machined " weld preps" were " buttered" with Alloy 600 type weld metal (Alloy 600 type weld metal is known as " Alloy 82 or 182") prior to final stress relief of the vessel. The botering was performed using a manual are process. Originally, the instrument nozzles were Alloy 600 (SB-16643) drilled bar stock. The initial dimensions of the nozzle ss 1-5/8 inch outer diameter (OD) and 19/32 inch inner diameter (ID). After stress relief of tl.e vessel, the instrument nozzles were inserted into the upper head and an Alloy 600 type "J" shaped partial penetration weld (J-groove weld) was made between the Alloy 600 type buttering weld and the Alloy 600 nozzle.
The original nozzle at the 7-l/2 location was found leaking in 1989 due to axial Primary Water Stress Corrosion Cracking (PWSCC). This prompted the replacement of all four Unit 2 pressurizer upper head instrument nozzles with Alloy 690 nozzles. The replacement nozzles were welded in place from the inside of the pressurizer. Alloy 600 type weld metal was used to attached the new Alloy 690 sleeves to the original Alloy 600 type buttering.
II. INVESTIGATION Calvert Cliffs experienced cracking of pressurizer heater sleeves and an instrument nozzle by PWSCC on Unit 2 in 1989. Since the middle 1980s numerous instances of axial cracking of partial penetration welded Alloy 600 nozzles have been discovered around the world. As a result, BGE has developed an Alloy 600 Program Plan that evaluates the PWSCC susettptibility of all Alloy 600 penetrations in both Units. The 7-1/2* nozzle found leaking on July 25,1998 was the same nozzle found leaking during 1989. The replacement nozzle was I fabricated of Alloy 690, an alloy developed specifically for its resistance to Stress Corrosion Cracking (SCC). Alloy 690 has never been cracked by PWSCC in numerous laboratory tests, and has never cracked in field service. It is the standard material for replacement steam 1 I
generator tubes. Because they were fabricated from Alloy 690, the Unit 2 replacement nozzles were considered in the Alloy 600 Program Plan to be immune to PWSCC and resultant leakage.
With very few exceptions, cracking of wrought Alloy 600 nozzles is expected to manifest itself as short, axial cracks on the ID of the Alloy 600 penetration material, adjacent to the location of the J-groove weld.
In laboratory tests, Alloy 600 type weld metal has been sh(,wn to be susceptible to PWSCC, although much less so than tubing, pipe, or bar stock. Three instances of domestic service failure of Alloy 600 weld metal have been reported. San Onofre in 1992 and St. Lucie in 1993 discovered pressurizer upper level nozzles leaking due to PWSCC with traditional l short, axial cracks in the nozzle material. At St. Lucie the nozzle was replaced with one made from Alloy 690, and was welded into place using the original construction weld geometry with
Alloy 600 type weld filler material. In March 1994, a leak was discovered in the vicinity of that nozzle. Non-Destructive Examination (NDE) of the ID of the nozzle indicated the nozzle was intact, with no cracks or indications. Penetrant Examination (irr) of the weld revealed a number of rejectable indications. St. Lucie did not perform corroborating metallurgical analysis, but concluded the weld contained defects, and the defects grew by PWSCC to provide a leakage path through the J-groove weld.
A. EXAMINATIONS AND DETERMINATION OF CAUSE Upon discovery of the leaking 7-1/2* nozzle, PWSCC of the Alloy 600 type weld metal was immediately suspected as the cause. Penetrant inspection (Irr) of the ID of the nozzle proved the cause of the leak was not within the Alloy 690 nozzle material. The nozzle ID and the nozzle to vessel weld were visually examined and showed no noticeable indications.
Ultrasonic examination of the vessel shell was performed to look for gross (large volumetric) defects in the ehell. No gross defects were found, therefore, a leakage path is not considered to exist through the shell material. Since neither the nozzle, nor the pressurizer shell, had indications (or mechanisms) that would permit leakage through them, it is concluded that the leakage was through the weld.
A root cause logic analysis was performed to identify potential and probable root causes. It was concluded that leakage was probably through the weld due to a combination of preexisting welding defects and PWSCC.
Due to the voluminous amount of industry and laboratory experience, and to the difficulty, expense and dose required to perform a surface exam of the Alloy 600 J-groove weld, surface examination was not performed. Due to the high radiological, engineering and practical difficulties associated with recovery of a portion of the weld leak path, a sample for corroborating metallurgical analysis was not removed.
DISCUSSION OF THE FAILURE MECHANISM PWSCC of Alloy 600 nozzles is normally driven by high residual hoop stresses in the nozzle that originate from weld residual stress. In an internally J-groove welded nozzle, the weld metal cannot contract in the hoop direction while the weld bead is cooling because of the constraint from the massive vessel wall; instead, contraction pulls the nozzle wall out radially, leaving high residual hoop stresses in the nozzle. Ti;> weld filler has residual stresses in the radial direction which to some extent are relieved by yielding of the weld metal while it is still hot.
The residual stresses in Alloy 600 nozzles installed during original fabrication received some degree of stress relief from the shop hydro performed at 1.5 times normal operating
- pressure. The shop hydro caused some yielding of the nozzle and weld metal in the radial
- l. direction. However, the nozzle still retains a high level of residual hoop stress which produces stress corrosion cracking in the nozzle after several operating cycles, relieving the residual stress. The shop hydro made the initial construction nozzles and welds less likely to crack.
Alloy 600 nozzles installed in the field as replacements using a J-groove weld do not receive the benefit of this shop hydro. Experience with field installed Alloy 600 nozzles has shown that they experience PWSCC in a comparatively short time (1-2 cycles) compared to E-_----_-- _ --_------ ------_----- - - _ - _ - - - - - _ _ _ - - - - - - - - _ _ _ _ - - - - - _ . - . - - - - - - - - - - - _ _ _ - - - - - - - _ _ _ - -
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! original nozzles which last 10-20 years or much longer. When BGE installed the 690 i replacement nozzles in the Unit 2 pressurizer upper head, the nozzle and weld filler were left with a high state of residual stress. Because the nozzle could not crack by PWSCC to relieve the residual stress, the failure location would more likely move to the weld filler.
Defects in the remaining original or replacement weld filler may have assisted in the initiation of PWSCC by creating a stress concentration. Defects would also act to accelerate PWSCC, since it has been shown the weld fillers are more susceptible to PWSCC in the l
creviced condition.
IMPLICATIONS OF WELD SIZE During the previous replacement, the nozzle was removed by drilling and grinding out the J-groove weld metal adjacent to the nozzle. The original Alloy 600 buttering material was left in place. A much larger J-groove weld was required for the 7-1/2* nozzle because of the method of extraction. Because BGE wanted the entire nozzle removed intact for destructive analysis, it was removed by drilling a series of closely spaced holes in the J-groove weld metal, burring out the ligaments, then extracting it with a slide hammer. The drilling / burring operation removed a substantial amount of the original weld, therefore, the repair J-groove i weld for the 7-1/2' nozzle was much larger than the repair J-groove welds on the other three I nozzles, with a width of at least 1/2" and a depth nearing 3/4".
i CRACK GROWTH CONSIDERATIONS 1
During the evaluation of the leaking 7-1/2" nozzle, extension of the weld crack into the alloy steel pressurizer shell base material was evaluated. Since the base material is not susceptible to PWSCC, and is not significantly degraded by deaerated reactor coolant, the only mechanism for propagating a crack into the pressurizer shell is low cycle fatigue. A l conservative fracture mechanics analysis indicates a hypothetical corner crack slightly larger than 1 inch (through the weld and just into the base material) would survive more than 2600 heat up and cool down cycles without growing to a critical size. (Ref. Framatome Technologies Calculation No. 32-5002086-00, attached). Since the vessel design life is 500 heat up and cool down cycles, it is concluded the hypothetical corner crack does not represent a challenge to the vessel structural integrity.
copies: G. L. Detter B. C. Rudell S. W. Welp
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