Similar Documents at Hatch |
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Category:SAFETY EVALUATION REPORT--LICENSING & RELATED ISSUES
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Acceptable Level of Quality & Safety.Considers Rev 2 to RR-4 & RR-6 Acceptable ML20206G1691999-05-0404 May 1999 SER Approving Requirements of Istb 4.6.2(b) Pursuant to 10CFR50.55a(a)(3)(ii) ML20207M1891999-03-11011 March 1999 SER Accepting Relief Request for Authorization of Alternative Reactor Pressure Vessel Exam for Circumferential Weld ML20196J4931998-12-0707 December 1998 Safety Evaluation Accepting Proposed Alternatives in Relief Requests RR-V-12,RR-V-15,RR-P-15,RR-V-7,RR-V-12,RR-V-14 & RR-V-15 ML20153G2481998-09-24024 September 1998 SE Concluding That Licensee Implementation Program to Resolve USI A-46 at Plant Adequately Addressed Purpose of 10CFR50.54(f) Request ML20239A2531998-09-0303 September 1998 SER Accepting Licensee Request for Relief Numbers RR-17 & RR-18 for Edwin I Hatch Nuclear Plant,Units 1 & 2.Technical Ltr Rept on Third 10-year Interval ISI Request for Reliefs for Plant,Units 1 & 2 Encl ML20236W3441998-07-30030 July 1998 Safety Evaluation Accepting Relief Requests for Second 10-yr ISI for Plant,Units 1 & 2 ML20236V5191998-07-28028 July 1998 Safety Evaluation Accepting Proposed License Amend Power Uprate Review ML20236L1821998-07-0707 July 1998 Safety Evaluation Accepting 980428 Proposed Alternative to ASME Boiler & Pressure Vessel Code,Section Xi,Repair & Replacement Requirements Under 10CFR50.55a(a)(3) ML20212A1981997-10-16016 October 1997 Safety Evaluation Denying Licensee Request for Relief from Implementation of 10CFR50.55a Requirements Re Use of 1992 Edition of ASME Code Section XI for ISI of Containments ML20216J8971997-09-12012 September 1997 SER Related to General Electric Nuclear Measurement Analysis & Control Power Range Neutron Monitoring Sys Upgrade Southern Nuclear Operating Co,Units 1 & 2 ML20216E9671997-09-0505 September 1997 Safety Evaluation Accepting ,As Suppl by 970902 Request for Relief to Request RR-V-11 Re IST & S/Rv ML20210S9141997-09-0303 September 1997 Safety Evaluation Accepting Licensee Request for one-time Relief from GL 88-01 for Insp of Category E Welds at Plant, Unit 1 & 2 ML20217N9381997-08-21021 August 1997 SE Re New & Revised Relief Requests Submitted by 970130,0307 & 25 Ltrs in Relation to Third 10-yr Pump & Valve IST Program ML20217N9811997-08-21021 August 1997 Safety Evaluation for Third 10-year Pump & Valve Inservice Testing Program,Southern Nuclear Operating Co,Inc,Hatch, Units 1 & 2 ML20148U6141997-07-0707 July 1997 Safety Evaluation Accepting Licensee Proposal for Third 10-yr Interval for Pump & Valve Inservice Testing Program ML20141A1981997-06-17017 June 1997 Safety Evaluation Accepting Licensee Design Criteria for Sizing ECCS Suction Strainers ML20141A1431997-06-16016 June 1997 Safety Evaluation Accepting Third 10-yr Inservice Insp Program Plan & Associated Requests for Relief.Relief Not Required for RR-08 ML20137N1811997-04-0404 April 1997 Safety Evaluation Supporting Amends 206 & 147 to Licenses DPR-57 & NPF-5,respectively ML20134P3661997-02-21021 February 1997 SER 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Electrical Connection to Replace Terminal Blocks in Selected Low Voltage Transmitter Measuring Loops ML20247H7261989-03-16016 March 1989 Safety Evaluation Re Use of Radioiodine Protection Factor for Sorbent Canisters ML20207M0431988-10-13013 October 1988 Safety Evaluation Denying Util 880711 Request for Relief from Hydrostatic Test Requirements of Section XI of ASME Code for Class 2 Portion of Main Steam Lines Between Outboard MSIVs & Turbine Stop Valves ML20153F9941988-05-0202 May 1988 Safety Evaluation Supporting Amend 153 to License DPR-57 ML20238A6801987-09-0404 September 1987 Safety Evaluation Re Insps & Repairs of Igscc.Plant Can Be Safely Operated for Another 18-month Fuel Cycle in Present Configuration ML20236F9831987-07-29029 July 1987 Safety Evaluation Supporting Util 831107,840229 & 860821 Responses to Generic Ltr 83-28,Items 3.1.1,3.1.2,3.2.1 & 3.2.2 ML20235X5271987-07-20020 July 1987 SER Supporting Util Response to Generic Ltr 83-28,Item 2.1, (Part 2) Re Vendor Interface Programs (Reactor Trip Sys Components) ML20235P8421987-07-14014 July 1987 Safety Evaluation Re Acceptance of Offsite Dose Calculation Manual as Updated & Corrected Through 861231 ML20215M3941987-06-22022 June 1987 Safety Evaluation Re Request for Relief from Inservice Insp Requirements ML20236F6151987-04-0101 April 1987 Safety Evaluation Re Analytical Method Used by Licensee to Evaluate Critical Stresses Re Mark I Containment Program Vacuum Breakers Adequate.Max Stress in Breakers Less than 30% of Code Allowable.Existing Design Structually Adequate ML20207U1441987-03-19019 March 1987 Undated Safety Evaluation Re Plant.Section 9, Radwaste Sys, of FSAR Also Encl ML20210S2731986-09-29029 September 1986 Safety Evaluation Re Inservice Insp Program & Requests for Relief ML20211F0241986-06-12012 June 1986 Safety Evaluation Supporting Util Listed Responses to Generic Ltr 83-28,Item 2.1 (Part 1) Re Identification & Classification of Reactor Trip Sys Components ML20211B3201986-05-30030 May 1986 SER Accepting Licensee 831107 & 840219 Responses to Generic Ltr 83-28, Items 3.1.3 & 3.2.3 Re post-maint Testing Requirements ML20205M9461986-04-24024 April 1986 Safety Evaluation Supporting Plant Operation in Present Configuration for 18-month Fuel Cycle.Plans for Insp &/Or Mod of Svc Sensitive Austenitic Stainless Steel Piping Sys Requested 3 Months Before Start of Next Refueling Outage ML20151Y4631986-01-29029 January 1986 Safety Evaluation Supporting Amend 122 to License DPR-57 ML20137M5311986-01-21021 January 1986 SER Supporting 850718 & 1127 Requests for Reconsideration of Relief from Requirements of Section XI of ASME Code Re Exam of Supports on ASME Piping ML20141F1261985-12-26026 December 1985 Safety Evaluation Supporting Amends 120 & 59 to Licenses DPR-57 & NPF-5,respectively ML20136A8461985-12-23023 December 1985 Safety Evaluation Re Responses to Generic Ltr 83-28,Items 3.1.1,3.1.2,3.2.1,3.2.2 & 4.5.1.Addl Info Requested on Items 3.1.1,3.1.2,3.2.1 & 3.2.2.Item 4.5.1 Acceptable ML20137E2191985-12-23023 December 1985 Safety Evaluation Re Util Response to Generic Ltr 83-28,Item 1.1, Post-Trip Review (Program Description & Procedure). Program & Procedures Acceptable 1999-09-13
[Table view] Category:TEXT-SAFETY REPORT
MONTHYEARML20217D3061999-10-13013 October 1999 SER Accepting Licensee Proposed Changes to Edwin I Hatch Nuclear Plant Emergency Classification Scheme to Add Emergency Action Levels Related to Operation of Independent Spent Fuel Storage Installation HL-5845, Monthly Operating Repts for Sept 1999 for Ei Hatch Nuclear Plant.With1999-09-30030 September 1999 Monthly Operating Repts for Sept 1999 for Ei Hatch Nuclear Plant.With ML20217A1691999-09-22022 September 1999 Part 21 Rept Re Engine Sys,Inc Controllers,Manufactured Between Dec 1997 & May 1999,that May Have Questionable Soldering Workmanship.Caused by Inadequate Personnel Training.Sent Rept to All Nuclear Customers ML20212A6641999-09-13013 September 1999 Safety Evaluation Authorizing Relief Request RR-V-16 for Third 10 Yr Interval Inservice Testing Program HL-5836, Monthly Operating Repts for Aug 1999 for Edwin I Hatch Nuclear Plant.With1999-08-31031 August 1999 Monthly Operating Repts for Aug 1999 for Edwin I Hatch Nuclear Plant.With ML20210J9631999-08-0202 August 1999 SER Finding That Licensee Established Acceptable Program to Verify Periodically design-basis Capability of safety-related MOVs at Edwin I Hatch Nuclear Plant,Units 1 & 2 ML20210J9271999-08-0202 August 1999 SER Finds That Licensee Performed Appropriate Evaluations of Operational Configurations of safety-related power-operated Gate Valves to Identify Valves at Plant,Susceptible to Pressure Locking or Thermal Binding HL-5818, Monthly Operating Repts for July 1999 for Ei Hatch Nuclear Plant,Units 1 & 2.With1999-07-31031 July 1999 Monthly Operating Repts for July 1999 for Ei Hatch Nuclear Plant,Units 1 & 2.With HL-5805, Monthly Operating Repts for June 1999 for Ei Hatch Nuclear Plant,Units 1 & 2.With1999-06-30030 June 1999 Monthly Operating Repts for June 1999 for Ei Hatch Nuclear Plant,Units 1 & 2.With ML20207E7631999-06-0303 June 1999 Safety Evaluation Concluding That Licensee Proposed Alternative to Use Code Case N-509 Contained in RR-4 Provides Acceptable Level of Quality & Safety.Considers Rev 2 to RR-4 & RR-6 Acceptable HL-5795, Monthly Operating Repts for May 1999 for Ehnp Units 1 & 2. with1999-05-31031 May 1999 Monthly Operating Repts for May 1999 for Ehnp Units 1 & 2. with ML20206G1691999-05-0404 May 1999 SER Approving Requirements of Istb 4.6.2(b) Pursuant to 10CFR50.55a(a)(3)(ii) HL-5784, Monthly Operating Repts for Apr 1999 for Ei Hatch Nuclear Plant,Units 1 & 2.With1999-04-30030 April 1999 Monthly Operating Repts for Apr 1999 for Ei Hatch Nuclear Plant,Units 1 & 2.With HL-5766, Monthly Operating Repts for Mar 1999 for Ei Hatch Nuclear Plant,Units 1 & 2.With1999-03-31031 March 1999 Monthly Operating Repts for Mar 1999 for Ei Hatch Nuclear Plant,Units 1 & 2.With ML20207M1891999-03-11011 March 1999 SER Accepting Relief Request for Authorization of Alternative Reactor Pressure Vessel Exam for Circumferential Weld HL-5755, Monthly Operating Repts for Feb 1999 for Ei Hatch Nuclear Plant,Units 1 & 2.With1999-02-28028 February 1999 Monthly Operating Repts for Feb 1999 for Ei Hatch Nuclear Plant,Units 1 & 2.With ML20206P6981999-01-0707 January 1999 Ehnp Intake Structure Licensing Rept HL-5726, Monthly Operating Repts for Dec 1998 for Ei Hatch Nuclear Plant,Units 1 & 2.With1998-12-31031 December 1998 Monthly Operating Repts for Dec 1998 for Ei Hatch Nuclear Plant,Units 1 & 2.With ML20196J4931998-12-0707 December 1998 Safety Evaluation Accepting Proposed Alternatives in Relief Requests RR-V-12,RR-V-15,RR-P-15,RR-V-7,RR-V-12,RR-V-14 & RR-V-15 HL-5714, Monthly Operating Repts for Nov 1998 for Ei Hatch Nuclear Plant,Units 1 & 2.With1998-11-30030 November 1998 Monthly Operating Repts for Nov 1998 for Ei Hatch Nuclear Plant,Units 1 & 2.With HL-5706, Monthly Operating Repts for Oct 1998 for Hatch Nuclear Plant Units 1 & 2.With1998-10-31031 October 1998 Monthly Operating Repts for Oct 1998 for Hatch Nuclear Plant Units 1 & 2.With ML20155B6121998-10-28028 October 1998 Safety Evaluation of TR SNCH-9501, BWR Steady State & Transient Analysis Methods Benchmarking Topical Rept. Rept Acceptable HL-5691, Monthly Operating Repts for Sept 1998 for Ei Hatch Nuclear Plant,Units 1 & 2.With1998-09-30030 September 1998 Monthly Operating Repts for Sept 1998 for Ei Hatch Nuclear Plant,Units 1 & 2.With ML20153G2481998-09-24024 September 1998 SE Concluding That Licensee Implementation Program to Resolve USI A-46 at Plant Adequately Addressed Purpose of 10CFR50.54(f) Request ML20239A2531998-09-0303 September 1998 SER Accepting Licensee Request for Relief Numbers RR-17 & RR-18 for Edwin I Hatch Nuclear Plant,Units 1 & 2.Technical Ltr Rept on Third 10-year Interval ISI Request for Reliefs for Plant,Units 1 & 2 Encl HL-5675, Monthly Operating Repts for Aug 1998 for Ei Hatch Nuclear Plant,Units 1 & 21998-08-31031 August 1998 Monthly Operating Repts for Aug 1998 for Ei Hatch Nuclear Plant,Units 1 & 2 ML20238F7131998-08-31031 August 1998 9,change 2 to QAP 1.0, Organization HL-5667, Monthly Operating Repts for July 1998 for Ei Hatch Nuclear Plant,Units 1 & 21998-07-31031 July 1998 Monthly Operating Repts for July 1998 for Ei Hatch Nuclear Plant,Units 1 & 2 HL-5657, Ro:On 980626,noted That Pami Channels Had Been Inoperable for More than Thirty Days.Cause Indeterminate.Licensee Will Replace Automatic Function W/Five Other Qualified Pamis of Like Kind in Drywell & Revised Procedures1998-07-30030 July 1998 Ro:On 980626,noted That Pami Channels Had Been Inoperable for More than Thirty Days.Cause Indeterminate.Licensee Will Replace Automatic Function W/Five Other Qualified Pamis of Like Kind in Drywell & Revised Procedures ML20236W3441998-07-30030 July 1998 Safety Evaluation Accepting Relief Requests for Second 10-yr ISI for Plant,Units 1 & 2 ML20236V5191998-07-28028 July 1998 Safety Evaluation Accepting Proposed License Amend Power Uprate Review ML20236N6751998-07-0909 July 1998 Part 21 & Deficiency Rept Re Notification of Potential Safety Hazard from Breakage of Cast Iron Suction Heads in Apkd Type Pumps.Caused by Migration of Suction Head Journal Sleeve Along Lower End of Pump Shaft.Will Inspect Pumps ML20236L1821998-07-0707 July 1998 Safety Evaluation Accepting 980428 Proposed Alternative to ASME Boiler & Pressure Vessel Code,Section Xi,Repair & Replacement Requirements Under 10CFR50.55a(a)(3) HL-5653, Monthly Operating Repts for June 1998 for Ei Hatch Nuclear Plant,Units 1 & 21998-06-30030 June 1998 Monthly Operating Repts for June 1998 for Ei Hatch Nuclear Plant,Units 1 & 2 HL-5640, Monthly Operating Repts for May 1998 for Ei Hatch Nuclear Plant,Units 1 & 21998-05-31031 May 1998 Monthly Operating Repts for May 1998 for Ei Hatch Nuclear Plant,Units 1 & 2 ML20248B8651998-05-15015 May 1998 Quadrennial Simulator Certification Rept HL-5628, Monthly Operating Repts for Apr 1998 for Ei Hatch Nuclear Plant1998-04-30030 April 1998 Monthly Operating Repts for Apr 1998 for Ei Hatch Nuclear Plant HL-5604, Monthly Operating Repts for Mar 1998 for Edwin I Hatch Nuclear Plant,Units 1 & 21998-03-31031 March 1998 Monthly Operating Repts for Mar 1998 for Edwin I Hatch Nuclear Plant,Units 1 & 2 ML20216B2711998-02-28028 February 1998 Extended Power Uprate Safety Analysis Rept for Ei Hatch Plant,Units 1 & 2 HL-5585, Monthly Operating Repts for Feb 1998 for Ei Hatch Nuclear Plant,Units 1 & 21998-02-28028 February 1998 Monthly Operating Repts for Feb 1998 for Ei Hatch Nuclear Plant,Units 1 & 2 HL-5571, Monthly Operating Repts for Jan 1998 for Edwin I Hatch Nuclear Plant,Unit 11998-01-31031 January 1998 Monthly Operating Repts for Jan 1998 for Edwin I Hatch Nuclear Plant,Unit 1 HL-5551, Monthly Operating Repts for Dec 1997 for Ei Hatch Nuclear Plant,Units 1 & 21997-12-31031 December 1997 Monthly Operating Repts for Dec 1997 for Ei Hatch Nuclear Plant,Units 1 & 2 ML20199B0561997-12-31031 December 1997 Rev 0 GE-NE-B13-01869-122, Jet Pump Riser Weld Flaw Evaluation Handbook for Hatch Unit 1 HL-5581, Annual Operating Rept for 1997, for Ei Hatch Nuclear Plant Units 1 & 21997-12-31031 December 1997 Annual Operating Rept for 1997, for Ei Hatch Nuclear Plant Units 1 & 2 HL-5533, Monthly Operating Repts for Nov 1997 for Ei Hatch Nuclear Plant,Units 1 & 21997-11-30030 November 1997 Monthly Operating Repts for Nov 1997 for Ei Hatch Nuclear Plant,Units 1 & 2 HL-5514, Monthly Operating Repts for Oct 1997 for Edwin I Hatch Nuclear Plant,Units 1 & 21997-10-31031 October 1997 Monthly Operating Repts for Oct 1997 for Edwin I Hatch Nuclear Plant,Units 1 & 2 ML20212A1981997-10-16016 October 1997 Safety Evaluation Denying Licensee Request for Relief from Implementation of 10CFR50.55a Requirements Re Use of 1992 Edition of ASME Code Section XI for ISI of Containments ML20211M6491997-10-0808 October 1997 Addenda 1 to Part 21 Rept Re Weldments on Opposed Piston & Coltec-Pielstick Emergency stand-by Diesel gen-set lube-oil & Jacket Water Piping Sys.Revised List of Potentially Affected Utils to Include Asterisked Utils,Submitted ML20211H5311997-10-0101 October 1997 Rev 2 to Unit 1,Cycle 17 Colr ML20211H5251997-10-0101 October 1997 Rev 3 to Unit 1,Cycle 17 Colr 1999-09-30
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p# "% l g- 4 UNITED STATES g
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't NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001
%, f SAFETY EVALUATION REGARDING THE REINSPECTION RESULTS OF THE CORE SHROUD VERTICAL WELDS GEORGIA POWER COMPANY. ET AL.
1 EDWIN I. PLANT HATCH. UNIT 1 DOCKET NO. 50-j!]_1.
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1.0 INTRODUCTION
1.1 Purpose 4
The purpose of this safety evaluation is to assess the reinspection results and flaw evaluations submitted by Georgia Power Company, et al. (GPC or the licensee) for the Hatch Unit 1 core shroud vertical welds.
1.2 Backaround The shroud was repaired at Hatch Unit 1 in the fall of 1994. The repair was intended to structurally replace the horizontal welds from H1 through H7.
Therefore, these welds were not required to be inspected before the repair.
However, because the repair did not structurally replace the vertical welds, they were required to be inspected. in view of the small cracks observed in the Industry, the inspection performed in the fall of 1994 for the vertical welds at Hatch I was limited to visual inspection of 12 inches of the V3, V4, V5 and V6 welds near the intersection with the H4 weld. The actual length inspected for these welds was 18 inches. No indications were seen during this limited inspection and the unit was returned to service.
j During the spring 1996 refueling outage, the vertical welds were examined
. again visually and more extensively in accordance with the recently issued BWRVIP guidelines on shroud reinspection (EPRI TR-105747, February 1996, "BWR Vessel and Internals Project - Guidclines for Reinspection of BWR Core Shrouds (BWRVIP-07)"). All accessible areas of all the vertical welds were inspected i visually by enhanced VT-1 examination according to the BWRVIP inspection guidelines (EPRI TR-105696, October 1995, "BWR Yessel and Internals Project -
- Reactor Pressure Vessel and Internm Evaluation Guidelines (BWRVIP-03)") from 1 the outside (0D). Welds V5 and V6 were examined both from the inside (ID) and the OD. Two indications, 2 inches and 12 inches in length, were seen in V5, and upon sample expansion in accordance with the guidelines, one indication 32 inches long and four small (1/2 inch) axial indications were observed in the V6 weld, both on the OD. Inspections on the ID showed no cracking for both the V5 and V6 welds. In its submittal, dated May 7,1996, GPC evaluated the significance of these indications.
Enclosure 9610290218 961024 PDR ADOCK 05000321 O PDR
l By letter dated June 27, 1996, the NRC staff requested the fracture mechanics analysis used by GPC for the above evaluation and a fracture mechanics analysis using a crack growth rate of 5 x 10(exp)-5 inches per hour instead of the 2.5 x 10(exp)-5 inches per hour that the licensee had used. GPC responded in a letter dated July 10, 1996.
2.0 DISCUSSION AND EVALUATION Licensee's Submittal GPC stated, among other things, that:
The axial cracking in itself is not new; axial weld cracks have been seen in several plants, but the observed length at Hatch 1 in the V-6 weld seems to be somewhat larger. Most of the cracks in other plants have been around 3 in, with one case where it was about 15 in. So the 32 in. indication is longer than those seen elsewhere. Of greater interest is that at least a part of the region of the V-6 indication was visually inspected in 1994 and found to be uncracked. Unless indications were missed before, one has to conclude that the observed indication is new.
Hatch I has operated with excellent hydrogen water chemistry (HWC) during the last cycle, with calculated ECP [ electro-chemical potential] levels below the -230 mV SHE [ standard hydrogen electrode] threshold in the region of the H4 weld, the apparent
'new' initiation (if it is) is surprising. Review of the videotape by materials experts at GE [ General Eletric] was inconclusive on the question of whether the indications represent actual shroud cracks. Some experts suggested that the indications may not be cracks at all and that they could be due to changes in the structure of the oxide film as a result of HWC. Similar indications were seen in the region of the access hole cover in another BWR operating under HWC. Subsequent UT [ ultrasonic testing] showed no cracking. Others felt that shallow cracking existed during the prior outage, and the HWC induced changes in the oxide structure could have made the preexisting cracks visible. HWC also makes the surface topography more clear.
The fact that there were no indications on the ID of the V-5 and V-6 welds is good, and suggests that the OD indication could have been due to other reasons such as cold work. There was general agreement that the indications did not have clear opening, and appeared to be tight suggesting that they are shallow.
GPC reviewed possible causes. It determined that vibration was not a credible cause. It reviewed the stresses due to the shroud repair and found them to be small and not high enough to cause cracking. It also decided that irradiation-assisted stress corrosion cracking (IASCC) was not a significant
P factor since the indications were on the outside surface of the shroud where the fluence is lower than that at the inside surface and the extent of branching observed was not consistent with that for IASCC. The consensus of opinion of GE experts was that the change in oxide structure due to HWC was the most likely cause of seeing cracklike indications that might have been there during the last outage, and that even if the indications did represent cracking, they were tight and likely to be shallow. .
1 GPC determined allowable crack lengths based on both linear elastic fracture I mechanics (LEFM) and limit load analysis; LEFM was governing for welds V5 and l V6. GPC determined the allowable through wall crack length to be 66.4 inches, i The allowable crack length is less than the width of the shell course for V5 2
and V6 (98.8 inches). Alternatively, the required uncracked ligament is 32.4 1 inches. Under BWRVIP criteria for reinspection of shrouds, allowances are added for crack growth based on an assumed crack growth rate of 5 x 10 (exp)-5 inches /hr, for growth at ooth ends of the crack, a-d for inspection uncertainties. These allowances total 7.6 inches, a value that is added to the uncracked ligament length.
GPC stated in its justification for continued operation that:
The allowable through thickness crack length for the V-5 and V-6 '
welds is 66.4 inches, including the safety factor. It [the analysis] also considers accident conditions and assumes that both .
H4 and H5 welds are fully cracked (360 degree through thickness l cracking). If inspection uncertainty and crack growth for one I cycle is considered, the allowable crack length is (66.4 - 7.6) -
58.8 in. This compares against the as found part through indication of 32 in. Alternatively, the required ligament is 40 in. compared to the available uncracked ligament of 98 32 -
66.4 in. Clearly, there is sufficient margin to justify continued operation beyond one cycle.
The licensee stated that (1) its analyses were conservative because its HWC would reduce the growth rate further, (2) that for the more realistic case of no through thickness crack at H4 and H5, the critical crack length for an axial crack length is expected to be longer than the weld itself, and (3) that it conservatively assumed through wall cracking and separate cylinders for each shell course.
Furthermore GPC concluded that:
Thus continued operation for at least one cycle is justified.
Additional inspections can be performed at the next outage to provide the basis for future inspections at that time.
Staff Evaluation The staff determined that the licensee's inspections meet the BWRVIP criteria and the flaw evaluation is acceptable for the following reasons. The licensee's actions are in accordance with current industry practice and the BWRVIP's guidelines for reinspection of BWR core shrouds. The staff has
- . . - -. . _ . _ . - ._- - . . . . _=_ - - -. . .. - .. .
1 accepted the BWR Owners Group's commitments to follow these guidelines in the
, interim period until the NRC completes its review of them.
The fracture mechanics analyses were performed in accordance wit' ff-d approved methods using staff-accepted growth rates. The analy. c y h i applied the appropriate conservatisms, showed the cracks were i'3 p*:t = by a wide margin.
t 1
2
3.0 CONCLUSION
The staff finds that the core shroud flaw evaluations performed by GPC are acceptable and that continued operation for this cycle which ends in the fall of 1997 is justified. Additional inspections will be performed at the next a
outage which can provide the basis for assessing the growth of the indications.
l 4
Principal Contributor: Merrilee Banic, NRR r
- Date
- October 24, 1996 i
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