ML20063E040

Forwards NEDO-22171, Core Spray Sparger Crack Analysis. Eccs,Lost Parts & Structural Analyses to Support Info Submitted at 820614-15 Meeting Re Reload Licensing & Crack Propagation Study Results Encl

ML20063E040
Person / Time
Site:	Brunswick
Issue date:	07/07/1982
From:	Zimmerman S CAROLINA POWER & LIGHT CO.
To:	Vassallo D Office of Nuclear Reactor Regulation
Shared Package
ML20063E042	List: ML20063E040 ML20063E048
References
NUDOCS 8207130280
Download: ML20063E040 (16)

Text

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GP&L Carolina Power & Light Company July 7, 1982 Office of Nuclear Reactor Regulation ATTN: Mr. D. B. Vassallo, Chief Operating Reactors Branch No. 2 United States Nuclear Regulatory Commission Washington, D.C. 20555 BRUNSWICK STEAM ELECTRIC PLANT, UNIT NO. 2 DOCKET NOS. 50-324 LICENSE NOS. DPR-62 RELOAD LICENSING - SUPPLEMENTAL INFORMATION

SUMMARY

In accordance with our June 14-15, 1982 meeting with NRC staff members, Carolina Power & Light Company (CP&L) hereby submits Emergency Core Cooling System (ECCS), lost parts, and structural analyses to support information provided to the Staff in that meeting. Additionally, CP&L is also providing crack propagation study results and the design specification for the core spray sparger clamp.

DISCUSSION Carolina Power & Light Company believes the enclosed analyses address the topics discussed at the meeting and justify startup, return to power, and continued operation for Brunswick Steam Electric Plant (BSEP) Unit

. No. 2 during Cycle 5 operation. The above analyses were preceded by revised Technical Specifications (TS), dated June 28, 1982, which incorporated a uniform 8.5 percent Maximum' Average Planar Linear Heat Generation Rate (MAPLHGR) reduction voluntarily imposed pursuant to the ECCS information presented in the aforementioned meeting. The enclosed analyses demonstrate the MAPLHCR reduction is overly conservative and not needed to ensure safe operation of BSEP Unit No. 2. At present, CP&L will not pursue the elimination of the !!APLHGR reduction but intends to do so in the near future with the analyses as justification.

8207130200 820707 p DR ADOCK 05000324 '

PDR 411 FayetteviHe Street . P. O. Box 1551

• Raleigh, N. C. 27602 h

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D. B. Vassallo ADMINISTRATIVE ,

Brunswick Unit No. 2 criticality is presently anticipated to begin July 13, 1982. We request the Staff review of the June 28, 1982 revised TS submittal and the enclosed analyses be conducted to support issuance of the TS revisions to allow return to power in accordance with this schedule. We will keep your staff apprised of any changes to the schedule.

Should you require additional information, please contact our staff.

Yours very truly, aan S. amerman Manager Licensing & Permits MSC/cr (256C2T5) cc: Mr. J. P. O'Reilly (NRC - RII)

Mr. J. A. Van Vliet (NRC)

Resident Inspector (BSEP)

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SUMMARY

ASSESSMENT OF ,

BRUNSWICK STEAM ELECTRIC PIMI ,

UNIT NO. 2 CORE SPRAY SPARGER CRACKING CAROLINA POWER & LIGHT COMPANY 4

I JUNE 1982 1

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SUMMARY

Carolina Power & Light Company (CP&L), through the assistance of a contractor, has assessed the crack growth potential of a crack located in the Brunswick Steam Electric Plant (BSEP) Unit No. 2 core spray sparger. Image enhancement techniques were applied to video tapes of field inspection results. The analysis was based on bounding calculations performed for the Pilgrim Station. These results, when applied to an estimate of the BSEP crack length (found from enhancement work), indicate crack growth over the next fuel cycle' (Cycle 5) will be insufficient to compromise the structural integrity of the core spray sparger.

On this basis, it is concluded that no corrective action ;'.s required to insure structural integrity during this period.

1.0 INTRODUCTION

In accordance with IE Balletin 8u-13, Carolina Power & Light Company performed a visual inspection of the core spray sparger at BSEP Unit No. 2 during the May 1982 refueling outage. Underwater TV camera inspection revealed one crack indication in the top sparger adjacent to the pipe to juncture-box weld.

l 2.0 VISUAL INSPECTION The initial bulletin - required inspection was performed using a in-vessel camera (with stand) with a documented resolution of 1 mil. To avoid shipment of the official (unenhanced) videotape, a second hand-held videotape i

was made for analysis and conputer enhancement purposes. From visual inspection, CP&L has determined the crack location to be within an are length of apprcximately 120' (about 4 inches, 2 o' clock to 4 o' clock). Although video tape was obtained from use of a hand-held camera, image enhancement techniques were used to improve the available image and aid in the crack's interpretation.

Figures 1 and 2 show the " original" condition of the top and bottom of the cracks. Figures 3 and 4 show the same views after image enhancement.

Based upon contractor review of the enhanced photographs and enhancements of cracks in other BWR spargers (Pilgrim and Oyster Creek), it was estimated that BSEP Unit No. 2 sparger crack is about 0.005 inches wide and 4 inches in length.

3.0 COMPARISON OF PILGRIM AND BRUNSWICK UNIT NO. 2 SPARGER A comparison of sparg'er characteristics between BSEP and Pilgrim was made in order to establish if the Pilgrim sparger structural evaluation results could be used to extrapolate expected crack growth trends for BSEP. A comparison of sparger geometry, material supplier fabrication, fabrication methods', welding, material properties, hours of service, service' stresses, and inspection results was made. A comparison indicates the two spargers are nearly identical in these areas. Additionally, crack inspection techniques and results also show nearly identical characteristics.

A comparison of material properties and operating parameters was also made. The Brunswick sparger has slightly lower carbon content and about

15% higher yield strength. The expected trend would be a slightly faster initial crack growth rate. The effect on arrest potential of the higher yield stress is not readily predictable. The higher yield level can lead to higher residual stresses. Since these residual stresses must be self equilibrating, the result is both higher tensile stresses (which tend to aid continued crack propagation) and higher compressive stresses (which aid crack arrest).

General Electric (GE) has evaluated service stresses for sparger normal operating conditions and design conditions (water injection', for Brunswick Unit 2. Loads from water injection and seismic design are not major contributors to crack growth due to the short duration of loading. Normal operating stresses, except for the aforementioned two load types were reported to be approximately 1 ksi.

4.0 ANALYSIS OF BRUNSWICK UNIT NO. 2 CRACK Table 1 shows the growth data with concomitant predicted final crack length. The values provided are appropriate to, but not directly applicable to Brunswick since the yield stress and residual stresses have not been updated to reflect the Brunswick case. Secondly, the actual yield stress and tensile stress have not been included in the evaluation of limit load failure point.

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The results in Table 1 assume the following conditions:

1 i 1) A total residual stress state identical to the Pilgrim Plant (including weld, fabrication and installation stresses).

2) A total through-wall crack length of 4 inches.

3) Bounding service loads of 5 ksi and 10 ksi. The results indicate the following predicted final flaw lengths over the next 18 months of operation. The crack growth rate used for postulated defects away from the weld is a worst case assumption (furnace sensitized in 8 ppm 02 water at 550*F). The weld region growth rate is taken on samples that were welded and then subjected to a low temperature sensitization treatment. This, along with the fact that the growth rates were established in 8 ppm 02 reactor quality water, means that the use of these growth rate data will result in a conservative analysis.

5.0 ASSESSMENT FOR GENERATION OF LOOSE PARTS ASSUMING 360*

CRACK AT T-BOX WELD.

In order to develop a loose part, one of two approaches is possible:

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l 1) The bracket (s) fail, thus dropping the sparger. As shown by l

l structural analysis, the brackets have a factor of safety of l

about 2.5 relative to code allowable stress. Also' physical inspection confirms brackets have good quality welds. Thus, the bracket failure is not considered a viable method of generating I

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2) In the absence of bracket failure, an additional circumferential (360') crack is required to develop a section of pipe free to

drop. The following arguments do not support this phenomenon.

a) Crack propagation rates evaluated for Pilgrim spargers were presented as follows:

1) Propagation rate is 0.2 inches / year for cracks not in the heat affected zone HAZ assuming 3 inch crack length.

ii) Propagation rate is 0.8 in/ year for cracks in the RAZ assuming mean welded data an high 02 '"Vif ""*"C' Since there are no additional welds in the sparger between the assumed 360* crack and the first bracket, the generation of a loose part in this area would require a crack not in the RAZ to propagate an additional 6 inches. This rate of propagation as presented for Pilgrim was .2 in/ year. T.he 6 inch length is based on the conservative assumption that an unseen 180* crack exists on the back side of the sparger.

b) Based on industry experience, no core spray sparger cracks i

l or indications have propagated 360*. To assume that two l

cracks (one of which is postulated) both propagate 360* is contrary to observation.

Therefore, based on the above, the development of a loose l

piece between the assumed 360* crack and the first bracket during a fuel cycle is not credible.

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6.0 CONCLUSION

Based upon the 1982 BSEP Unit No. 2 inspection results and the correlations indicated between Pilgrim and Brunswick spargers, it can be concluded that the extrapolation of Pilgrim data Irov' ides a semi quantitative basis for predicting crack growth trends for the BLunswick sparger. However, the sic, ,arities between the two spargers indicate that the amount of crack growth expected during cycle 5 operation is much less than that necessary to compromise the integrity of the sparger.

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TABLE 1 Region Growth Data Service Predicted Final Stress (ksi) Crack Length (in. )

(for initial flaw 4")

Near weld As-welded 5 5.0 As-welded 10

• Away from Furnace 5 4.0 Weld Sensitized Furnace 10 4.5 Sensitized

• Data not available from Pilgrim Evaluation Upper bound crack size at the next outage is predicted to occur near the weld at approximately 5.0" for the 5 kai stress level. Away from weld, the equivalent lengths for 5 kai and 10 kai are approximately 4.0" and 4.5" for the two stress levels. These lengths are shorter than the critical length to cause failure by limit load criteria.

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BUSINESS CPERATl3Ns GEN ER AL O sticTaic r.sv o

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1.1 Purpose. His specification provides engineering requirements for the design, fabrication and installation of a planned modification to the core l spray sparger in the Brunswick 2 reactor pressure vessel.

2. APPLICABLE DOCDENTS 2.1 General Electric Documents. H e following documents form a part of this specification to the extent specified herein:

l'.1.1 Snoportinz Documents

a. 730E854 - Core Spray Sparger

b. 729E762 - Reactor normal Cycles

o. 135B9990 - Nozzle normal Cycles 2.2 Codes and Standards. n e following codes and standards (issue in effect at the date of the purchase order, or as specified in this specification or its supporting documents) form a part of this specification to the oztent specified herein.

2.2.1 American Society of Mechanical Enrineers ( AM) Boiler and Pressure Vessel Code

a.Section III, Division I, Nuclear Power Plant Components, Subsection MI, Core Support Structures,1974 Edition with Addenda to and including Summer, 1975 Addenda

b.Section II, In-Service Inspection of Nuclear Reactor Coolant Systems, 1977 Edition with Addenda to and including Summer 1978 Addenda

c.Section II, Yelding Qualifications,1980 Edition 2.2.2 U.S. Federal Resister Code of Federal Rennistions (GR)

a. 10 CFR 50 - Title 10, Energy; Chapter 1, Nuclear Regulatory Commission; Part 50, Licensing of Production and Utilization Facilities (1[ Appendiz A General Design Criteria eeno seta inev. gefe 3

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~~* 22ds447 ,, ,0. 3 NUCLEAR ENER3Y BUSINESS OPERATIONS G E N E R AL ((() E LE CTRIC REV 0 s.

3. DESC1IPTION 3 .1 The sore spray sparser is an internal structure located within the reactor vessel. The original design basis document referenced in Para-graph 2.1.1.a defines the sparger assembly as circular pair of pipe half rings which are mounted at two levels inside the shroud wall for the purpose of distributing core cooling water through the unitiple spray nozzles located evenly along the sparger lengths. This modification is planned to provide additional structural margin to the apper sparger at vessel azimuth 172 degrees where a crack exists. This crack is located approximately 0.5 inch from junction box on the long header side and is greater than 180 degrees of length in the aparger hesdwr circumferential direction. This modification is also intended to prevent significant opening (greater than .062 inch) of the crack under normal or core spray actuation conditions.

4. REQUTD M NIS 4.1 Codes 4.1.1 The core spray sparsers are not classified as ASME code items.

Accordingly, this modification is not a oods item but the design shall take guidance from ASME Code,Section III, Subsection NG, as specified in Para-graph 2.2.1.a.

4.1.2 The requirements of ASME Code Article 1TA-7000, as specified in Para-graph 2.2.1.b, shall apply.

4.2 Safety 4.2.1 The core spray sparger modification has been classified by GE as

! essential to the safety of the plant according to the definition of Criteria I l

of the NRC General Design Criteria,10 CFR 50, Appendix A (refer to Paragraph 2.2.2). This classification is based on the core spray sparger function of providing core cooling.

4.2.2 The core spray sparger modification shall be designed by GE to meet the requirmnents of NEC General Design Criteria,10 CFR 50, Appendix A (refer to Paragraph 2.2.2) .

4.3 Functional i

4.3.1 The design of this sparger modification shall consider the fact that installatism will be done underwater using remote handling and installation tooling.

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NUCLEAR INEROY 22As447 sm 4 BUSINESS OPERATIONS G EN ER AL @ ELECTRICREV 0 4.3.2 Modification design shall be structn' rally adequate to hold s'parger together in the event the existing crack were to propagate through the entire sparger oross section. This may be demonstrated by analysis per Para-graph 4.5.

4.3.3 Sparser crack 12akage or the ikstalled modification hardware shall not interfere with the spray distribution when the core spray is operated. '~~~

4.3.4 All core structure assemb.17 interfaces shall be considered in the modification design.

4.4 Desian 4.4.1 The reactor vessel design pressure is 1250 psig and design temperature is 575'F. The reactor vessel operating conditions are as defined by the document referenced in Paragraph 2.1.1.b. Additional core spray piping design and operating conditions are as defined by the document referenced in Para-graph 2.1.1.c.

4.4.2 Anstenitic stainless eteel exposed surfaces shall have a minimum corrosion allowance of 0.003 inch based on 40 years life.

4.4.3 The design vaine of the fast neutron finance (> 1.0 Mev) at the core spray sparger is 1 x 10 ' n/cm .

4.5 Analysis 4.5.1 Stress analysis of the sparger modification shall be performed. The resnits shall be compared to allowable stresses given in the ASME code (reference Paragraph 2.2.1.a). Loads shall be calculated based on the Nozzle Thermal Cycles (reference Paragraph 2.1.1.c). Core spray actuation shall be considered a normal event in this analysis. Initial assembly loadings on the sparger and the modifications shall be considered in this analysis.

l 4.6 Materials and Fabrication 4.6.1 Tho ' components required by this specification shall be f abricated from materials that are procured and processed according to the appropriate GE (eg, 550YPII) specifications. These materials shall meet the ASME and/or AS'Di specifications referenced therein. Material shall be controlled within the f abricator's shops under a quality assurance program which has been determined by GE survey /andit to meet material traceability and safety grade manuf acturing practices as required by the Code of Federal Reguistions 10 CFR 50, Appendix B, and 10 CFR, Part 21. Piece part identification shall be in accordance with Paragraph NG-4122 of the document referenced in Para-graph 2.2.1. s . '

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NdCLEAR ENEROY 22As447 5 BUSINESS OPERATIONS GEN ER AL h ELECTRIC REV 0 FINAL

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4.6.1.1 A11 materials shall be constructed'from Type 304, 304L, 31'6 or 316L stainless steel with the carbon content controlled to be equal to or less than 0.02 percent except that materials that will not be welded or otherwise heated above 800*F during f abrication may contain up to 0.050 percent carbon.

4.6.1.2 Yolders and weld procedures shall be qualified to ASME Section II as referenced by Paragraph 2.2.1.c.

5. PAGAGING, SEIPPING, AND STORAGE REQUTumgrs 5 .1 General. Equipment shall be packaged to protect it from damage' during handling, shipment, and storage at the construction site. Equipment shall be boxed, securely held in place and packaged to maintain the degree of cleanliness required during manuf acturing. Handling equipment, strapping, or hold-down devices shall be applied so the equipment is not damaged in any way.

Site storage vill be inside heated warehouses. .

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