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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
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p *t* UNITED STATES E
NUCLEAR REGULATORY COMMISSION E WASHINGTON, D.C. 30006 4 001 i
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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION SUPPLEMENTAL RESPONSE TO NRC BULLETIN 88-08 " THERMAL STRESSES l IN PIPING CONNECTED TO REACTOR COOLANT LOOP SYSTEMS"
- FACILITY OPERATING LICENSE NOS. NPF-76 AND NPF-80
- HOUSTON LIGHTING & POWER CONPANY j CITY PUBLIC SERVICE BOARD OF SAN ANTONIO CENTRAL POWER AND LIGHT COMPANY i CITY OF AUSTIN. TEXAS i DOCKET NOS. 50-498 AND 50-499 l SOUTH TEXAS PROJECT. UNITS 1 AND 2 BACKGROUND l- In Reference 1, the Nuclear Regulatory Commission (NRC) provided an evaluation j of the revised response by Houston Light and Power (HL&P) to NRC Bulletin j 88-08. This response was authored by Westinghouse Electric Corporation (W) as
! contractor to HL&P (Reference 2). M based its response on an analytical
! methodology developed under a program sponsored by the Electric Power Research
! Institute (EPRI) to investigate Thermal Stratification, Cycling, and Striping l (TASCS) (Reference 3). In Reference 4, HL&P submitted its response (prepared -
1 by W) to the NRC staff safety evaluation.
' EVALUATION i
The staff has reviewed the HL&P response in Reference 4, and has concluded that I i the comments made in its evaluation, as stated in Reference 1, remain valid and l current.
! A major weakness previously identified is the lack of correspondence between the j' TASCS methodology and the observed failures at Farley and Tihange. The TASCS ,
! methodology assumes that the temperature in the unisolable pipe is the same as the I reactor coolant loop (RCL) cold leg temperature, with and without leakage, within ;
j' - the turbulent penetration length. It also assumes that the leakage through the
~
i check valve in the connected piping heats up a negligible amount over the length i of the horizontal pipe from the check valve to the cold leg, and calculates the
)
- steady state thermal stress distribution based on this temperature difference. A cyclic frequency is then postulated and the fatigue life determined.
i Reference 3 reported limited results of a proprietary high temperature simulation i test of Farley, in which the temperature along the bottom of the pipe with leakage ,
j was measured. Figure 5.3-8 of the TASCS report shows that the axial time average 1
! 97o3270250 97o324 PDR ADOCK 05000498 1 P PDR
. . * =, - -.r e .- .--r , .-r< ~v --3s- e -s =
l l- l i
temperature of the leakage at the bottom of the pipe increases as the flow approaches the elbow. This figure shows the bottom inside wall temperature history at the five-diameter distance measured from the header nozzle, which is l the location of the weld joining the elbow to the horizontal segment. It also I
shows the bottom inside wall temperature history at the six-diameter distance, which appears to be similar to that at Farley, shown in Figure 5.3-2. The mean temperature at the location of the weld is about 500*F, with very small time
! variation. No top temperature at the'same location was stated, but the top measurement at Farley indicates almost the same value. The calculated thermal stress, which is based on the top-to-bottom difference of the mean temperatures, is therefore very small at this location. Yet, the crack at-Farley occurred at this location and not at the six-diameter distance, which shows a considerably greater transient temperature variation. No explanation for this paradox has been provided. Although no temperature measurements have been reported at Tihange, it can be surmised that the cracks in the elbow, as shown in Bulletin 88-08, Supplement 2, also occurred where temperature differences were small.
The response states again, that in the application of TASCS methodology to the South Texas normal charging and alternate charging lines it was determined that:
"At other locations within the unisolable piping, where turbulent penetration cycling is possible, the alternatip stresses were determined to be below the endurance limit stress based on 10 cycles." The response concluded on this basis that no cracking would occur in these lines. However, the "other" locations referenced in HL&P's response are those between the maximum penetration length and ,
the RCL nozzle, and one of these corresponds to the locations in Farley and l Tihange where the cracks were found.
The HL&P response also states that the Farley and Tihange failures were evaluated using the TASCS methodology, and that "the TASCS methodology does predict failure i at the observed crack locations." No such calculations were provided to support i this response. The response also provides "a summary of the results of the TASCS i methodology for the Farley/Tihange cracking. The fatigue and fatigue crack growth !
analysis resulted in a prediction of failure of 3 to 6 calendar years, which was ;
conservative with respect to the Farley plant age." This result was stated in '
, Reference 7 and is therefore not a result of the TASCS methodology.
In Reference 1, the staff stated in Evaluation Item 2 that the velocity component I which was measured in the Low Temperature Turbulent Penetration Test program was not specified. The HL&P response states that: "In the Low Temperature Penetration Test program, velocities were measured in the axial and the tangential direction; only the axial velocity was significant." This contradicts the data shown in References 5 and 6. The best fit curve of Figure 5.3-3 of the TASCS report for the 3" piping is almost the same as similar figures for all tests shown in these references. These figures are labeled " Maximum tangential velocities for-f all tests" and represent the decay of maximum (tangential) velocity with increasing distance from the tee. Very little information on the axial velocities is provided. The curves in Figure 5.3-3 and 5.3-4 are therefore tangential velocity curves. The equation of the upper bound curve in Figure 5.3-3 has the same slope as the best fit curve, and was used to determine the equation for the extent of the turbulent penetration. Therefore, the statement that "only the axial velocity was significant" is incorrect. In fact, the axial velocity does not enter into the calculations anywhere.
In the response HL&P also stated that the TASCS methodology was not intended to simulate an actual plant. Rather, it is intended to be used to generate a conservative set of thermal loadings. However, any such methodology must be able to reflect known events which are known to have occurred under. actual operating conditions. The events listed in NRC Bulletin 88-08 may be considered as benchmark problems by which to judge the adequacy and reliability of this i methodology. , l l Finally, thermal stratification cycling is a transient heat transfer process. The i L TASCS methodology is based on steady state heat transfer methods, which do not )
reflect transient thermal stress conditions. ;
1
3.0 CONCLUSION
Based on a review of the additional material submitted in Reference 4, the staff concludes that the findings stated in Reference I remain valid, namely: ,
l
- 1. The mechanism of turbulent penetration was not fully investigated under the '
1 TASCS program. Its relevance to the fatigue failures described in Bulletin 88-08 has not been clearly established.
i
- 2. The TASCS methodology does not address the observed fatigue failures l described in Bulletin 88-08. The thermal loading conditions for.the failures described in Bulletin 88-08 remain undetermined.
i The staff also concludes that some elements of the TASCS methodology are l acceptable for application to the normal charging and the alternate charging lines at South Texas, Units 1 and 2, provided HL&P commits to the following provisions: ,
l
- 1. The thermal stresses due to isolation valve leakage are based on temperature distributions determined from transient heat transfer calculations using the l largest temperature difference between the turbulence source and in-leakage or out-leakage in the unisolable sections. The temperature cyclic history i should be such as to provide the greatest stress range. ;
- 2. Fatigue failure is postulated at the nearest weld to the turbulence source in the case of a horizontal branch line attached to the RCL, or at the first ,
elbow in a branch line with a vertical segment attached to the RCL.
- 3. The American Society of Mechanical Engineers (ASME)Section III Class 1 fatigue analysis is based on the rigorous combination of design basis transients and the thermal stresses due to isolation valve leakage.
l
- 4. The time interval from start of check valve leakage to crack initiation is !
based on the ASME Section III, Class I fatigue analysis and a cycling j frequency of one cycle per minute is assumed, as recommended in Reference 3.
l 5. Monitoring provisions to determine inadvertent internal leakage through the ;
isolation valve are established and implemented. If such leakage is 4 detected, the time interval determined in step 4 establishes the allowable
! time interval to implement repairs. I r
j .
l
)
i l l
! REFERENCES
- 1. Letter of February 23, 1996, from T. W. Alexion, USNRC, to W. T. Cottle, Houston Light and Power (HL&P).
- 2. WCAP-12598, Supplement 1, "NRC Bulletin 88-08, Evaluation of Auxiliary Piping for South Texas Project Units 1 and 2," Westinghouse Electric Corporation (W), November 1993.
- 3. EPRI TR-103581, " Thermal Stratificatibn, Cycling, and Striping (TASCS),"
prepared by Westinghouse Electric' Corporation for the Electric Power Research Institute, Palo Alto, California, March 1994. (Licensable l material, proprietary and confidential).
- 4. Letter of July 15, 1996, from S. E. Thomas, HL&P, to the USNRC Document ,
Room, with attached M letter dated June 19, 1996, from M. A. Sinwell, W, to '
W. T. Cottle, HL&P, with enclosure " Response to NRC Safety Evaluation of l WCAP-12598, Supplement 1, and EPRI Report TR-103581." l
- 5. Kim, J. H., A. F.
Deardorff and R. M. Roidt,
" Thermal Stratification in Nuclear Reactor Piping System," presented at the International Conference on Nuclear Engineering, November 1991, Japan.
)
- 6. Kim, J. H., R. M. Roidt and A. F.
Deardorff,
" Thermal Stratification and Reactor Piping Integrity," Nuclear Engineering and Design 139 (1993). North l l Holland. ,
1
- 7. Westinghouse Report WCAP-11786, "J. M. Farley Unit 2 Engineering Evaluation i of the Weld Joint Crack in the 6" SI/RHR Piping," April 1988, proprietary.
Principal Contributor: Mark Hartzman Date: March 24, 1997 l
I 1
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