ML20112J387

Provides Addl Details in Support of NRC Review of C/As Re Crack Indications Identified at Plant Unit 3 CS Sys.Peco to Install Repair Clamp on Each of Four CS Downcomers Prior to Returning to Operation from Current Refueling Operation

ML20112J387
Person / Time
Site:	Peach Bottom
Issue date:	10/12/1995
From:	Hunger G PECO ENERGY CO., (FORMERLY PHILADELPHIA ELECTRIC
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
IEB-80-13, NUDOCS 9606200149
Download: ML20112J387 (44)

Text

{{#Wiki_filter:- _,. Ctation Support Departmext lEB 80-13 i .4 y PECO ENERGY "'co c" '2r c -a "< Nuclear Group Headquarters 965 Chesterbroon Boulevard Wayne. PA 19087-5691 October 12,1995 Docket No. 50-278 License No. DPR-56 U.S. Nuclear Regulatory Commission Attn: Document Control Center Washington, DC 20555

Subject:

Peach Bottom Atomic Power Station, Unit 3 Core Spray in-Vessel Piping

References:

1) Letter from G. A. Hunger, Jr. (PECO Energy) to U.S. Nuclear Regulatory Commission dated November 5,1993 2) Letter from G. A. Hunger, Jr. (PECO Energy) to U.S. Nuclear Regulatory Commission dated November 10,1993 3) Letter from S. Dombeck (NRC) to G. A. Hunger, Jr. (PECO Energy) dated November 16,1993 4) Letter from G. A. Hunger, Jr. (PECO Energy) to U.S. Nuclear Regulctory Commission dated December 8,1993 5) Letter from G. A. Hunger, Jr. (PECO Energy) to U.S. Nuclear Regulatory Commission dated June 13,1995 6) Letter from G. A. Hunger, Jr. (PECO Energy) to U.S. Nuclear Regulatory Commission dated September 28,1995 7) Letter from G. A. Hunger, Jr. (PECO Energy) to U.S. Nuclear Regulatory Commission dated October 9,1995

Dear Sir:

The purpose of this letter is to provide additional details in support of the NRC's review of PECO Energy's corrective actions associated with crack indications identified in the Peach Bottom Atomic Power Station (PBAPS), Unit 3 Core Spray (CS) system, and the NRC's verbal approval to return to operation from refueling outage 3R10. The corrective actions, and PECO Energy's request for NRC approval to resume operation were submitted in Reference 7. This request was made in accordance with the requirements of IE Bulletin 80-13, " Core Spray Cracking." Additional information associated with this issue was provided in References 1 through 6. 2000G0 f /* k' 9606200149 951012 I f PDR ADOCK 05000278 '(/ I \\ G PDR

October 12,1995 l Page 2 l' i As stated in Reference 7, PECO Energy wRI be installing a repair clamp on each of the four CS l downcomers. This work is currently in progress, and wIl be completed prior to retuming to operation from the current refueling outage This repair modification was reviewed in accordance with 10 CFR 50.59. Attachment 1 to this letter includes the 10 CFR 50.59 evaluation and the supporting references. Attachment 2 to this letter provides PECO Energy's response to the NRC's request for additional Information. Based on completion of the modification, the NRC granted verbal approval to retum to operation ) from the current refueling outage. Because the modification instaus a permanent repair for each of the identified cracks, the approval was not limited to a specific cycle of. operation; however, j PECO Energy will continue to visuaNy examine the Core Spray piping in accordance with the guidance in IE Bulletin 80-13. These examinations wlN continue to monitor tha condition of welds and piping material that are not repaired as a result of the installation of the four clamps. If you have any questions please feel free to contact us. .0 - ,f. G. A. Hunger, Jr., Director Licensing Attachments cc: T. T. Martin, Administrator, Region I, USNRC W. L Schmidt, USNRC Senior Resident inspector, PBAPS P s I

\\ ~; .9 i ATTACHMENT 1 I i 10 CFR 50.59 EVALUATION, REV.1 FOR MODIFICATION P00335 i CORE SPRAY.DOWNCOMER REPAIRS i h I o t 1 L i c i l 4 I i h 1 i

~, i, Peach Bottom, Unit 3 '1-i 10CFR50.59 Review, Rcv.1 Modification P00335 Page 1 of 13 10 CIT 50.59 REVIEW for MODIFICATION P90335 INSTALLATION of CORE SPRAY LINE DOWNCOMER CLAMPS in Peach Bottom Atomic Power Station Unit 3 I. SUBJECT This 10CFR50.59 Review addresses the modification to repair of core spray line downcomers at the 7.5 degree,172.5 degree,187.5 degree and 352.5 degree shroud penetration locations. During Peach Bottom Unit 31993 refueling outage 3R09 inspections performed in response to USNRC IE Bulletin No. 80-13, identified a enck indication on the 172.5 degree core spray line downcomer. Additional crack indications were found during the 1995 refueling outage 3R10 on the 7.5,187.5 and 352.5 degree downcomers. The crack indications am located in the venical section (downcomer) of the core spray line outside the shroud but inside the Reactor Pressure Vessel (RPV) where the downcomer pipe is connected to a welded sleeve. The indications run circumferentially in the Heat Affected Zone (HAZ) of the pipe sleeve where the sleeve is welded to the downcomer line. The location of the indications are shown in Figure 1. Ultrasonic inspection of the cracks have characterized the indications as follows: DOWNCOMER CORE SPRAY CRACK LENGTH LOOP (APPROX. DEG.)* A (AZ 352.5*) A 180 B (AZ 7.5") B 128 C (AZ 187.5*) A 280 D (AZ 172.5*) B 250

• Not continuous, summation of total crack lengths.

A repair by modification was designed that addresses the identified crack indications (below weld 1, Figure 1) on the 7.5 degree,172.5 degree,187.5 degree and 352.5 degree azimuths. The repair at 172.5 degme azimuth also envelops welds 2, 3 & 4 of Figure 1. The additional design features for the 172.5 azimuth clamp were inch:Jed prior to 3R10 in vessel inspections to envelop weld locations assoc;ated with the downcomer repair on a contigency basis. The function of the modification is to ensure the structural integrity of the Core N

Peach Bottom, Unit 3 1 10CFR50.59 Review, Rev.1 Modification P00335 Page 2 of 13 Spray (CS) downcomer even if the identified defects in the HAZ below weld I were to grow to the full circumference of the sleeve. Additionally, for the 'D' downcomer the repair assures stmetural integrity with cracks at weld locations 2, 3 and 4. The modincation adds a two clamp design at the 'D' downcomer and a one clamp designs at the 'A', 'B' and 'C' downcomers in the area where the downcomer joint to the shroud inlet is located. The repairs are shown conceptually in Figure 2 (172.5 degree) and Figure 3 (7.5,187.5 and 352.5 degree). The upper clamp bears on the top of the sleeve that attaches the core spray downcomer to the core spray sparger inlet pipe. A rod locates and supports the lower clamp from the upper. The lower clamp is centered over the inlet pipe to elbow weld joint. A U-bolt that attaches to the upper clamp provides axial restraint between the sleeve and elbow, spanning the crack location (s). The proposed modiGcation is designed so as not to interfere with the potential shroud stabilizer installation or with normal mactor servicing activities. The proposed change is permanent. The change is designed for a 40 year plant life, using the ASME Boiler and Pressure Vessel Code, Subsection NG (1989 Edition) as a guide for design and analysis. Repair clamp hardware is classified as safety-related, and is designed to curmnt accepted standards. Therefore, it can withstand the same design bases loads as the current core spray line downcomer under normal and abnormal operating conditions. The installation of this hardware will not affect (degrade) other RPV internals. This review demonstrates that the clamps can be installed without impacting previously evaluated conditiens in the UFSAR, and their installation has no impact on the bases of the Technical SpeciGcation and does not involve any i unreviewed safety question. II. DETEloilNATION

1. Does the activity involve a Technical SpeciGeations change or other Facility Operating License amendment?

No. The clamp repairs ensure the integrity of each core spray downcomer inside the RPV. Them is no unacceptable effect to any ECCS system. Current Technical Specifications (CTS) 3.5. A.1,b require an operable Gowpath of taking suction from the suppression pool and transfering the water to the spmy sparger in the RPV. The leakage assumed with the various 360" thmugh-wall cracks in the downcomers does not render the flowpath

h. i( Peach Bottom, Unit 3 10CFR50.59 Review, Rev.1- .r Modification P00335 Page 3 of 13 inoperable, since the core spray pumps are still capable of delivering design basis flow. Therefore, a change to the existing Technical Specifications or Improved Technical Specification is not required. Technical Specification sections 1.1, 2.1, 3.2, 3/4.5. A, 3/4.5.C, 3/4.5.D, 3/4.5.E and 3/4.5.F and Improved Technical Specifications section 3.5.1 were reviewed in making this determination. I

2. Does the activity make changes to the facility as described in the SAR7 Yes. Although installation of the repair clamps does not involve a change in l

the manner in which the core spray line responds to design basis loadings, j and the repairs evaluated under this 50.59 are not discussed in the SAR, the estimated leakage from the Core Spray piping in the vessel exceeds the original design allowable for the "B" loop. Therefore, installation of the clamp repair constitutes a change to the facility as described in the SAR. j i The function of the modification is to ensure the structural integrity of the CS downcomer even if the reported defects were to grow to the full circumference of the weld #1 heat affected zone of the sleeve. The modification will also ensures the structural integrity of the 'D' downcomer in - the event additional cracking (full circumferential) develops at weld locations 2 through 4 of Figure 1. The repair clamps the area where the core spray downcomer and the core spray sparger inlet pipe join. The repairs are shown conceptually in Figures 2 and 3. The upper clamp mechanically grips the downcomer, and bears on the top of the sleeve that attaches the downcomer to the core spray sparger inlet pipe. A rod is used to support and locate the L lower clamp from the upper. The lower clamp is centered over the inlet pipe to inlet elbow weld joint. A U-bolt that attaches to the upper clamp provides I axial restraint between the downcomerjoint collar and the riser elbow, l spanning the crack location (s). No other modification to the CS piping will j be required. j The maximum leakage evaluated for the 'B' loop of core spray (343 GPM) i exceeds the original design allowable of 100 GPM. However, the leakage margin evaluation is well with in margins established by the SAFER /GESTR-LOCA analysis. The maximum leakage evaluated for the 'A' loop is 78 i GPM which is within the original design margins. l UFSAR Sections 3.0,6.0,6.5 and 14.6 were reviewed in making this l detennination. [

4 t 4 1 i i ATTACHMENT 1 10 CFR 50.59 EVALUATION, REV.1 FOR MODIFICATION P00335 CORE SPRK/ DOWNCOMER REPAIRS 4 1 l l + ! l l i P i 7 I o e a...~.... g

'f Peach Bottom, Unit 3 i 1 i 10CFR50.59 Review, Rev.1 Modification P00335 Page 4 of 13

3. Does the activity make changes to procedures as described in the SAR7 No. The modification does not change any reactor or system operation, does not involve any new mode of operation, and does not involve any change to sequence of events. Therefore, the review of the UFSAR Sections 3.0,6.0, i

6.5 and 14.6 determined that the modification will not require a change to a procedure in the UFSAR.

4. Does the activity involve tests or experiments not described in the SAR?

No. The modification involves the installation of clamp hardware on the core spray downcomer. No tests or experiments are required to validate the clamp design. Therefore, the review of the UFSAR Sections 3.0,6.0,6.5 and 14.6 determined that the modification will not require a change to the UFSAR. 1 l Since the answer to question 2 is 'Yes', a safety evaluation is required. HL. SAFETY EVALUATION A. Those accidents potentially negatively impacted by this change include: 1. ECCS-LOCA, 2. UFSAR Chapter 14 Transients j 3. LOCA-Radiological, 4. Main Steamline Break (MSLB) 5. Earthquake. 1 In all cases, installing the core spray downcomer clamps has no or negligible effect on these plant safety analyses. 1. May the possibility of occurrence of an accident previously evaluated in the SAR be increased? No. Plant systems and components will be capable of perfonning their intended functions with the clamps installed. The possibility of occurrence of an accident previously identified in UFSAR Section 14.6 is not increased. Clamp installations will not adverseli affect any Code requirements imposed on the core spray system. Tlte possibility of component failure is not increased. If the cracks propagate to 360 N

/. + Peach. Bottom, Unit 3 i [' 10CFR50.59 Review, Rev.'1 l i Modification P00335 p - Page 5 of 13 degrees, the separate portions of the downcomer are captured and thus there will be no possibility of loose parts resulting from the failure. The ) modification design incorporates provisions (i.e. crimping assembly bolts) - to ensure the clamp hardware does not come loose and thus preventing any loose parts concerns. 2. May the consequences of an accident previously evaluated in the SAR be l increased? No. Systems and components used to mitigate the (radiological) consequences of the accidents in the UFSAR are not degraded by this modification. All of the events in the Peach Bottom UFSAR were examined to determine if the consequences of any of these events is increased by the installation of the repair clamps. Consequences (i.e., radiological dose) associated with the design basis accidents are evaluated in the UFSAR. The existing core spray downcomer and repair clamps do not function to mitigate the consequences of any UFSAR event except the design basis LOCA event. No UFSAR dose calculation will be impacted by this change. For the design basis LOCA event discussed in the UFSAR, the core spray line and downcomer provide the flow path inside the RPV for the ECCS flow to the core spray spargers. Maintaining this flow path is required to ensure that core cooling capability is maintained following the design basis LOCA. This repair design, through its restraint of the joint, ensures the integrity of the core spray downcomer, with a 360 degree through wall crack in the pipe sleeve, under DBA conditions. The modification will also ensure the structural integrity of the 'D' downcomer in the event additional full circumferential cracking develops at weld locations 2 through 4 of Figure 1. An assessment of the leakage through the crack in the downcomer coupling sleeve was perfomied to confinn that this leakage has no significant effect on the existing ECCS analyses. The cumulative leakage for the "A" and "B" core spray loops following clamp installation are 78 GPM and 343 GPM respectively. The greater leakage value for the 'B' loop is based on addition circumferential cracks may be allowed at the downcomer/sparger inlet pipe joint with the 'D' downcomer clamp installed. These leakage rates are within the margins allowed for the core spray injection under the SAFER /GESTR-LOCA analysis. The SAFER /GESTR-LOCA analysis demonstrated that 5,000 GPM @ 105 psig (with an associated nm out flow of 6,250 GPM @ 0 psig) of K I l l

M, Peach Bottom, Unit 3 10CFR50.59 Review, Rev.1 Modification P00335 Page 6 of 13 core spray flow is sufficient to maintain adequate core cooling. Existing system requirements maintain a pump supply flow of 6,250.GPM @ 105 psig with an associated runout flow of 7,825 GPM at 0 psig per loop. Therefore, the estimated cumulative leakage for each loop remains within the established margins for ECCS-LOCA requirements. ' Variations in piping stresses associated with the additional weight of the repair hardware and with multiple downcomer cracking has been evaluated in references 1 and 2, and found acceptable. Radiological consequences of the previously identified accidents are not increased. Therefore, it is concluded that the repair clamp installations ensure that the consequences of a design basis LOCA will not be increased. The repair clamps impose a negligible change to the plant operating conditions, and thus, the ECCS-LOCA and transient analysis remain valid. 3. May the possibility of an accident of a different type than any previously evaluated in the SAR be created? No. The clamps are designed to the stmetural criteria specified in the UFSAR. All of the loads and load combinations specified in the SAR relevant to the core spray line have been evaluated and are within design allowables. The clamps do not add any new operational / failure mode or create any new challenge to safety related equipment or other equipment whose failure could cause a new type of accident. B. The components important to safety which are impacted by the modification are the core spray system and RPV internals. 1. May the probability of occurrence of a malfunction of equipment "Important to Safety" previously evaluated in the SAR be increased? No. The clamp is designed and constructed as a safety related component. No adverse equipment interactions will be created by installing the clamps. Therefore, the probability of an equipment malfunction is not increased. s,

Peach Bottom, Unit 3 10CFR50.59 Review, Rev.1 Modification P00335 Page 7 of 13 The design of the modification assumes the pmsent cracks will grow to 360 degrees through wall. The modification will also ensure the structural integrity of the 'D' downcomer in the event additional full circumferential cracking develops at weld locations 2 through 4 of Figure

1. The installation of the downcomer repairs will limit the separation between the downcomer and inlet pipe to 0.054 inch. This maximum separation results from the temporary cooling of the CS riser relative to the newly installed U-bolt. It is conservatively assumed that the U-bolt is still at 550 degrees F when the downcomer is cooled to 310 degrees F, average temperature, by the injected water from the torus (240 degree F temperature difference). After a few minutes of post LOCA core spmy system injection, the riser pipe and U-bolt temperatums will be in equilibrium. However, due to postulated displacement of a loose spool piece of pipe in the multiple crack scenario ('D' downcomer), the total width of the cracks will remain at.054 inch. For the 'A', 'B' and 'C' downcomers, the crack width will close to approximately.005 inch.

Analysis performed under reference 2 have confirmed that installation of the clamps does not impact previous repairs perfonned on the 120* and 240* azimuth T-Boxes. l 2. May the consequences of a malfunction of equipment "Imponant to Safety" previously evaluated in the SAR be increased? No. The installation of the clamps ensures that each core spray line, even if cracked, will perform its safety function to ensure adequate core cooling (protect the fuel) by limiting separation between the downcomer and sparger inlet pipe. The clamps perfonn a passive function that does not interfere with any equipment that is used to mitigate any abnonnal operating occurrence or the radiological consequences of a malfunction described in the UFSAR. Thus, the consequences of a malfunction of equipment imponant to safety is not increased. The cumulative leakage from each core spray loop will not prohibit the loops from providing adequate core cooling during a design basis LOCA. The cumulative leakage values of 78 GPM for loop "A" and 343 GPM for loop "B' are within the 1250 GPM flow margin established for each core spray loop in the SAFER /GESTR-LOCA analysis. 3. May the possibility of a different type of malfunction of equipment ) l

l Peach Bottom, Unit 3 E. 10CFR50.59 Review, Rev.1 .Y Modification P00335 Page 8 of 13 "Important to Safety" other than any previously evaluated in the SAR be created? No. All equipment assumed to operate in the trznsient analysis, and the i safety mlated structures, systems and components will not be adversely affected by the clamps. All components interacting with the clamps will perform their intended functions of ensuring adequate core cooling to j protect the fuel. The clamps do not increase challenges to or create any new challenge to equipment. The clamp does not create any new sequence of events that lead to a new type of malfunction. Therefore, the possibility of a different type of component malfunction than evaluated in the UFSAR is not created.- 1 i C. List the Technical Specifications Bases reviewed for potential reduction [ in the margin of safety. 4 The applicable Technical Specification Bases reviewed were 1.1,2.1, 3.0, 3.5. A, 3.5.B, 3.5.C, 3.5.D, 3.5.E and 3.5.F, and Improved Technical Specifications bases 3.5. These bases do not contain any margin of safety that is affected by Modification P00335.

1. Is the margin of safety as defined in the Bases of any Technical Specification reduced?

No. The Technical Specifications and their Bases are not affected by the installation of the clamps. No safety analysis referenced in a Bases will change. Therefore, the installation of the clamps will not affect the margin of safety of any Technical Specification Bases. D. CONCLUSION This evaluation has investigated the installation of clamps on the core spray lines at PBAPS. The plant licensing bases have been reviewed. This review demonstrates that clamps can be installed (1) without an increase in the probability or consequences of an accident or malfunction previously evaluated, (2) without creating the possibility of an accident or malfunction of a new or different kind from any previously evaluated and (3) and without reducing the margin of safety in the bases of a Technical Specification. Therefore, installation of the core spray line clamps does \\.

Peach Bottom, Unit 3 / i 10CFR50.59 Review, Rev.1 Modification P00335 - Page 9 of 13 not involve any unreviewed safety question. IV. REFERENCES

1. GENE-771-99-0295, Rev.2, Dated October,1995, Core Spray Line Downcomer Bracket Stress Assessment Report.

2. GENE -771-98-0295, Rev 2, Dated October 1995, Core Spray Line Seismic Assessment Report l

1 1 l 1 e -4

'f; Peach Bottom, Unit 3 d 10CFR50.59 Review, Rev.1 Modification P00335. Page 10 of 13 4 IV. . APPROVALS t' Prepared by: 14W Date: /0/B/K /' PECO, PB Design Enginpdring Prepared by: Date General Elec 'c Nuclear Energy i J 8!(I Interface Review: 4 Date: /o P8GD, PB N ;"-Engineering f i 2 Interface Review: Date: /0 96 shdd' PB CompoEent Engineering Peer Review: n Date: PECO, Nuclear Engine (singlDivision /0[o8fff Approval: Nf Date: PEDO, Nuclear Engineering Division /' ' h

m no: um,775n , OC OG~'W Gbitin1'GC YixLer,p atm Peach Bottom, Unit 3 10CFR50.59 Review, Rev.1 Modification P00335 Page 10 of 13 IV. APPROVALS [bW Date: N/BAf Prepared by: PECO, PB Dealgn Wring e Date /# ff Prepared by: General Electric Nuclear Energy Interface Review: Date: PECO, PB Design Engiacering [ Date: /O iS Interface Review: a Shd6 PB CompoEsnt Engineering II It Date: Peer Review: n-PECO, Nuclear Engine (dallDivision Approval: Date: __ PECO, Nuclear Engineering Division \\, . ~...

Peach Bottom, Unit 3 10CFR50.59 Revi;w, Rev.1 Modification P00335 Page 11 of 13 ca.eaoosMP001 TYPCRACK \\ sHnouD HEAD RANGE mpj 'N yp UPPER SHROUD F1ANGE l oj / 'G) Q j s ~ /p f 2 \\ 5I17" Figure 1. Core Spray Sparger Riser /Downcomer s.

I,. '\\, Peach Bottom, Unit 3 10CFR50.59 Review, Rev. I Modification P00335 Page 12 or.13 t Ef ErYE u"-,"eds oEcYs EY IERT W ' l 5 il el Pl= y.L + 1

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,s _s UW towan etur M AND M Figure 2. CSS Riser Repair Concept

i 3.' Peach Bottom, Unit 3 10CFR50.59 Review, Rev.1 Modification P00335 l l Page 12 0f 13 d sv40 %Ul1

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UPPE C AP BOLT FROM 1 CLAMP TO U-BOLT j 1 h ER UPPER CLAM WELO GRIPS CSL T N 1 f 3. U j O u v ,i / i i I l SHROUD HEAD BOLT LUGS U-BOLT PASSES THRU LOWER CLAMP SECTION A-A TO ENGAGE ELBOW LOWER BRACKET, SHROUD AND I 1 l l Figure 3. CSS Riser Repair Concept l l i t l s i DE 'd A963G dtimJ 39 ud10:21

56. 60 D0

i o' OENE 771-99-0295, REV ' o DRF B11-00642 l SHEET 1 CORE SPRAY LINE DOWNCOMER BRACKET STRESS ASSESSMENT REPORT for PEACH BOTTOM ATOMIC POWER STATION, UNIT 3 Modl5 cation P00335 / Pr Prepared by-D.L. Rousar, Senior Engineer Reviewed by: M.M & "///f! B. Sridhar, Senior E gi er / M f Approved by _ /oject bianager F.C. Gaylork / l 10/9/95 2/I*d ASd3J3 ES3T)niJ 39 LJa62:20 16. 60 130

M '1 O O ~ GENE-77199-0295, REV.2 DRF B11-00612 -l SHEET 5 APPENDIX A - M AXNUifATRESS

SUMMARY

U-Bolt Stresses Senice Level Calculated Stress Intensity Allowable Stress (ksi) (ksi) Normal / Upset (Primag 2.5 Sm = 29.5 Membrane) Normal / Upset (Primag 5 '7 1.55m = 44.2 Membrane + Primary Bending) Normal / Upset (Secondani 2.5 SSm - SS.4 Senice Level C - Pm 2.5 1.5Sm = 44.2 Pm + Pb 5.37 2.25Sm = 66.4 Service Level D Pm / Pm + 2.5/5.37 Sy = 32.7/.7Su = 62.9 Pb Max. Cumulative Usage 0.0 1.0 Fastener Stresses Service Level Categog Calculated Stress Allowable Stress (ksi) Intensity (ksi) Normal /Lpset (Priman Shank or Threads 22.37 .95y - 29.4 Membrane + Secondary Thread Shear 6.43 .6Sy = 19.6 Membrane including Bearing 7.66 2.7Sy = 41.72 Preload) Normal / Upset (Primary Shank or Threads 22.37 1.2Sy = 39.2 Membrane and Bending + Secondary Membrane and Bending) 1 Senice Level C - Priman U-bolt-elbow 22.37 1.5Sm = E: Membrane contact Senice Level C - Primary 22.37 2.25sm - 66.4 Membrarie + Priman-Bending i Senice Level D Pm i 22.37 j Sy = :.7 Max. Cumulative Usage .001 l1.0 l 10/9/95 us 'd A963H3 eJ3M 39 ud2E:2C si C.L.>0

GENE 77199 0295, Mv.2 DRF B11-00642 l _ SHEET 2 1. INTRODUCTION

===1. Background=== 1.1 Core Spray Sparger Downcomer Weldt Each CSS (upper and lower) includes two 6 NPS schedule 40 inlet pipes which penetrate the shroud. An elbow md vertical pipe spool are connected to these inlet pipes outside the shroud; the assembly of this elbow and the vertical pipe spoolwill be referred to as the CSS downcomer. The core spraylines (CSL) connect to the CSS dmmcomer pipes at the approximate elevation of the top of the shroud. The field welded connections between the CSL downcomer and the CSS downcomer pipe is shown at zone B 16, sheet 1 on reactor assembly drawing 2.1.f. The semi-circular CSL is a 304 stainless steel piping run internal to the reactor. Its purpose is to carry the core spray system flow from the core spray nozzle thermal sleeve (located at 472 inches elevation above vessel zero,55A at 120*, N5B at 240*, see 2.1.a and 2.1.f) to two of the CSS downcomers. The 6-inch CSLlaterals are welded to an 7.93 inch outside diameter T-box as shown on 2.1.d. The CSL T-box connection with the core spray nozzle thermal sleeve is a reactor assembly weld as shown on sheet 1, zone B-15. Each horizontal section of the CSL is supported from the vessel wall by a CSL bracket (158B8353P001) which is welded to the vessel 20 inches from the nozzle, and a CSL clamp (see 136B190SP001 and sheet 4 of 2.1.a), located at 15',165', 195', and 345'. 1.2 CSS Downcomer Modification. During the Peach Bottom Unit 31993 refueling outage and inspections done in response to IE Bulletin 80-13, circumferentialIGSCC defects were found on one of the CSS downcomer connections at 172.5', adjacent to the upper horizontal weld to the vertical downcomer pipe, see Figure 3-1. In the 1995 refueling outage, cracks were also found in the 7.5 deg.,187.5 deg. and 352.5 deg. downcomer pipes. The cracks vary in length from a minimum of 7.5 inches to 17.5 inches are in the weld heat affected zone base material, on the connector sleeve, about 1/4 inch from the weld. A repair (by modification) is designed that addresse: the identified cracking in the heat affected zone in the pipe sleeve of the downcomer sleeve /spigotjoint, including potential additional cracking in the spigot / sleeve and elbow area for the 172.5 deg. azimuth downcomer. 1.3 Modification Renair. The modification repair of the CSS downcomer (172.5 deg.) includes an external clamp assembly which will be mechanically attached to the CSS downcomer at the defect area. The clamp is placed on the CSL downcomer above thejunction with the CSS downcomer pipe and extends below the connector, as shown in Figure 1. A lower clamp is placed at the location of the pipe to lower elbow weld. This clamp encircles 360 degrees degrees of the weld. l 10/9/95 ../2'd ASd3H3 MO3TOJ 39 WdOC:20 56. 60 EC

OENE 771-99 029$, REV.2 DRF B11-00642 l SHEET 3 The upper clamp isjoined by a U-bolt to the elbow to provide vertical structural continuity across the defect area. For the 7.5 deg.,187.5 deg. and 352.5 deg. azimuths, a similar simplified modification repair is used. This repair employes an upper clamp without the extension below the connector and a half clamp at the lower weld. The remainder of the repair is identical to the 172.5 deg. clamp. 1.2 Purpose This report transmits the results of the design stress analysis which assesses the effects of the core spray system operational cycles and shroud stabilizer effects on j the modification hardware. Also included are the results of a core spray system leakage analysis. The analysis is contained in Design Record File (DRF) B11-00642. 1 2.

SUMMARY

AND CONCLUSIONS 2.1 Scope This report covers only the modification hardware and localized stresses, if any, imposed on the core sprayline. For the purposes of this analysis, the structural j integrity at weld locations other than the crack location is considered to be j complete. At the crack location, crack propagation to 360 degrees ir credered for both stress and 'eakage evaluation. 2.2 ASTIE III Code Compliance's The clamp stresses satisfy the requirements of the ASME Code, Section III. Sub-section NG. A summary of the results obtained by solution of Sub-section NG j equations for all significant locations is contained in Appendix A of the stress analysis located in DRF B11-00642 for both clamp designs and contained herein as Appendix A. The stresses reported herein are the maxima for each cl:usification. The U-Bolt section stresses are evaluated to the requirements of paragraph NGS222 for both repair designs. The preload imposed on the U-bolt at installation is greater than the cyclical loadings and as a result, the maximum usage factor for the U-bolt is 0. The maximum primary plus bending stress is 5,370 psi compared to an allowable stress of 44175 psi and occurs in the cur ed section of the bolt. Threaded fastener stresses are evaluated to the requirements of paragiaph NG3232. The maximum primary membrane plus secondary membrane including l preload is 22,370 psi compared to an allowable of 29,400 psi and occurrs cross sectional area of the 1 inch bolt. The preload imposed on the bolting l10S'95 ../E*d ASd3H3 MS37Dnu 35 W:!tE:20 36. 60 1D0

l GENE-771-99-0295. REV.2 o DRF B11-00642 l SHEET 4 l l exceeds the cyclicalloadings and as a result, the fastener maximum fatigue usage is.001. Although the LOCA event is considered a Service Level C condition. Senice Level A and B allowables are easily met for allload conditions as shown in the Appendix. Evaluation of possible leakage is based on the assumption that the identified crack propagates to 360 degrees with another potential crack existing also for 360 degrees within the connector region for the 172.5 degree location. Upon the activation of the core spray system, the core spray line is assumed to contract to the extent that a total.054 inch crack width will be present. Due to possible mis-alignment of the isolated pipe segment preventing crack closure upon l temperature equilibrium, the gap is assumed to remain constant. At the remaining downcomer locations, the cracks are assumed to be no larger than.005 inch. The normal system leakage through the CSL vent when added to the connector region crack leakage amounts to 343 gpm for the "A" loop and 78 GPM for the "B" loop in the steady state condition. t i 4 i 4 4 i 9 l 10/9/95 ut 'd A963t13 MS3 U t1 39 WdIE:E0 56, 60 DO

GENE.77199 0295, fGV.2 l DRF B11006J2 f l SHEET 6 l APPENDIX A cont'd. Upper Clamp Stresses (172.5 degrees) Senice Level Calculated Stress Intensity Allowable Stress (ksi) (ksi) Normal / Upset (Primary 2.2 Sm = 17.5 Membrane) Normal / Upset (Primary 2.9 1.5Sm = 26.25 Membrane + Primary Bending) - Normal / Upset (Secondary) 42.8 SSm = 52.5 Service Level C - Pm 2.4 1.5Sm = 26.25 P_m + Pb 3.1 2.25Sm = 39.37 Senice Level D Pm / Pm + 4.7/5.8 Sy - 30/.7Su - 75 Pb Max. Cumulative Usage .31 1.0 Flowrates System Operation Flowrate (gpm) w/ leakage Required Flowrate (based on 0250 GPM (gpm) Design Flow) LOCA j5907 5000 l 10/9/95 ASd3G ' S3TOJ 39 tid?E :20 26, 60 DO 1/9'd d

t GENE-771 99-0295, REV.2 l DRF B11-0064: l~ $HEET 7 l kvD o BOLT FROM UPPER CLAMP TO U BOLT UPPER CLAMP 1 UPPER CLAMP i GRIPS CSL N' LOWER BRACKET FOR VERTICAL e CENTERED OVE9 RESTRAINT WELD i l ( b< k 8 d $ B / t k ./ / fil + j/ / 1 I w i, ,7 / - / I gp[ rN]- 4, +.% O p,# \\

n

[ ^ 9 /a, ". N nc G '/, O / 'l' $//, i / l ~Y Y h / '/,//;) y g' 9,c / '- i ,/ Q'k \\ 4'$,' ~ d /j/// ','/ f / / SHROUD HEAD / </ / 2 O BOLT LUGS U SOLT PAS $ES SECTION A. A THRU LOWE9 CLAY LOWER CLAMP, SHROUD AND RPV TO ENGAGE ELBOW ) Figure 1. CSS Riser Repair Concept i l 109.'95 2/2*d A983G MS3TOJ 39 L1 DSS:20 S6. 60 1:0

OCT 08 '95 04:31Pf1 GE f0 CLEAR Er4ERGY P.2/8 i GENE-771-98 0295, REV.1 an DRF B1100642 ' WJ SHEET 1 + CORE SPRAY LINE SE5MIC AS ESSMENT REPORT for i PEACH BOTTOM ATOMIC POWER STATION, UNIT S I Modificadon P00SS5 i l ) i i i f 1 I i Prepared by:_ N LI M % \\C/GbI H.L.Hwang Principal Enginedy Verified by: N M bev' 'Y8/56 K K Fujikawa Senik.Ehgineer g/gr Approved by# - h/f/9.s' F.C. Gaylord }roject Manager i 1 4 l s.

,,- OCT 08 '95 07* 17Pt1 GE i(JCLEAR ElIERGY. P.2/4 s' GENE 771-98-0295, REV.3, mas DRF B11-00642 SHEET 2

1.0 INTRODUCTION

1.1 - Background Peach Bottom Atomic Power Station Unit 3 has two Core Spray Lines (CSL) which enter the reactor pressure vessel (RPV) at the 120 degree and 240 degree azimuth locations. A set of two 316L Stainless Steel (SS)l reinforcement brackets were-previously added to connect the T-box to the CSL pipes to prevent pipe separation from the T-box. This connection is $ade by applying fillet welds on both sides of the brackets. In addition, the CSLjoint near the shroud penetration is assumed to be cracked (as discussed in the assumptions below), the bracket ) (Modification P00335) shall be added to the 7.5 172.5,187.5 and 352.5 degree CSL downcomer (4 locations total) to provide re)inforcement at the locatio downcomer weldjoint connection. This modification is a bolted design utilizing clamps which attach to the CSL. i 1.2 Purpose I This report transmits the results of the design sttess analysis which assesses the effects of the new brackets (Modification P00335) on the existing modified CSL and brackets. The purpose of the analysis is to demonstrate the seismic structural adequacy of the CSL and reinforcement brackets at Peach Bottom Unit 3. The analysis is contained in Design Record Files (DRF) B13-01732 and 31100642. This revision incorporates the relative seismic displacement (design carthquake) at the shroud penetration to be 0.400 inches. The total number of equivalent cycles is 50 cycles. 2.0 ASSUMPTIONS The following assumptions were sed in the CSL structural analysis:

1. The CSL downcomer sleeve / spigot assembly near the shroud penetration is assumed to have a 360' through wall crack. No creditis taken for any remaining ligament at the postulated crack location.

2. The connection at the four repairjoints, which includes the CSL downcomer sleeve / spigot assembly and the repair bracket,is' assumed to have a moment carrying capability equivalent to 10% of th_c original moment ofinertia for an eight inch length of the core spray pipe above the short radius elbow near the shroud. -

i ) 6 J

OCT 08 '95 07:17PM GE 10 CLEAR Ef EPGY P.3/4 GENE 771-98-0295, REV.1 m i i l DRF B11-00542 M SHEET 3 -

3. Fifty stress cycles is assumed for the seismic event.

4. Displacements associated with the core shroud stabilizers installed are utilized.

i

5. The fatigue usage includes the thermal effects due to both the uncracked and cracked CSL configurations. This is conservative because, the thermal case is counted twice in the fatigue analysis, plus the th'ermal stresses for the uncracked configuration are much less than the stresses fof the cracked configuration.

6. The CSL is analyzed consistent with the requirements of Class 1 pipe per ASME III Subsection NB 3600. This includes the stress' indices per NB-3600.

3.0 MODEL DESCRIPTION A finite element model of the CSL was created which included the CSL pipe from the thermal sleeve at the RPV nozzle to the CSL' supports near the shroud penetration. The model includes the reinforcement bracket at the T-box connection and the elbows to the penetration sleeve, but excludes the penetration sleeve. Thejoint at the U-bolt clamps were approximated by assuming the moment ofinertia at lower pipe element to 10% of the original moment ofinertia. Figure 1A shows a sketch of the model. Beam elements were used for the CSL pipe, thin shell elements were used to model the T box, reinforcement brackets at the T box and a portion of the pipe near the T-box. Boundary elements were used to simulate the CSL pipe supports. 4.0 LOAD CASES Thirteen different cases were analyzed and are listed in Table 1. 5.0

SUMMARY

AND CONCLUSIONS 5.1 ASME III Code Compliance The brackets and the piping attachment stresses are analyzed according to NB-3200 requirements. The results are tabulated in Appendix A-1 and A-2. The T-box had the maximum stresses which are briefly summarized as follows. The maximum fatigue usage factor is 0.324. This is at the T-box bracket fillet weld to the pipe. The main contribution to the fatigue usage is due to combination of OBEl and OBED. The maximum primary stress'is the Senice Level B condition. The primarpmembrane stress plus-primary-bending-stress is 21,100 psi. The stress is within the allowable limit of 25,500 psi The maximum stress for Senice Level D is 38,500 psi (maximum local stress)as compared to 3 Sm-51,000 psi. The analysis also assumes SSE is twice OBE, which is consenative. A conservative stress s,

,, ocT es '95 07:18PM GE f 0 CLEAR EFERGY P.4/4 i GENE-77198-0295, REV.'J, g DRF B1100642 SHEET 4 concentration value of 4.0, which includes a 1.2 factor for bending components and 3.53 for peak stresses is used for the fatigue analysis. I In the analysis it was assumed that there are 50 cycles with total separation between T-box and core spray pipes. j. I This analysis simulates the cracked condition eqpivalent to 10% moment ofinertia exist for 8 inches length of the core spray pipe above the short elbow near the shroud.- i The CSL pipe stresses satisfy the requirements of Article NB-3600 of ASME Section . III. A summary of the results obtained by the sojution of Subarticle NB 3650 equations for all significantjoints in the piping system is contained in Appendix D of the analysis located in the referenced DRF's, and contained herein as Appendix A 3. The maximum primary stress ratio is the primary membrane stress for the -Service Level B condition. The stresa value for Service Level B is 5,952 psi as compared to the allowable stress of 25,500 psi. The maximum thermal expansion stress (Equation 12) for pipe elementper NB 3600 is 20,902 psi with a stress ratio of 0.41. The maximum Equation 13 stress is 5,486 psi. The maximum fatigue usage factor is 0.001. The piping model at the sleeve crack causes moment relief at thejoints. The analysis model assumes that 10% moment ofinertia at the sleeve is existing. This assumption is considered reasonable because the both of OBED and OBEI can cause loads on the elbows and thy T box brackets. 5.2 Conclusions The results of the stress analysis shows that the core spray line with the repair brackets is structurally adequate to withstand the operating load conditions. i L i i I l i l

OCT 00 '95 04 ?&M GE f 0 CLEAR Ef ERGY 8

GENE 77l 9B4295,REV.1 g i DRF B11-00642 _ SHEET 5 l Table L Analysis Cases RUN # Load Types Case Condition T-box both ends separation 1 Therrnal 1 Normal NO 2 Thermal 2 Normal YES I 3 Weight 1 Normal YES I 4 OBEIX 1 Static g YES I 5 OBEIY l 2 Static g YES i 6 OBEIZ l 3 Static g YES i 7 OBED-X l 1 Static YES 8 OBED-Z l 3 Static 'YES 9 LOCA Y l Static YES DISP 10 OBED-X 1 Static NO 11 OBED-Z 3 Static NO 12 OBEI-X 1

Response

YES spectrum 13 OBElZ .3

Response

YES 8 l spectrum Note : All cases assume the CS # is cracked at the bolted clamp locations. boxacom s uetaE l s Psucr-- meas &f, s,

CCT 08 '95. 04:34Fl1 GE f UCLEAR ElERGY FM I,.. GENE 771-98-0295, REV.2 DRFBil 00642 SHEET 6 APPENDTX A - STRESS

SUMMARY

A-1: T-box Bracket Stresses per NB-3200 Senice Leve! Calculated Stress Intensity Allowable Stress (ksi). (ksi) Normal /Upsct (Primary) 21.1 1.5Sm - 25.5 Normal /Upsec (Primary + 35.7 3.0Sm = 51.0 Sec. excluding thermal bending) Normal / Upset (Primary t 64.6 N/A Secondary) Service Level C 21.1 2.25Sm = 38.25 Senice Level D 38.5 3.0Sm = 51.0 Max. Cumulative Usage 1 0.324 1.0 -A-2: Pipe Elements to T-box Bracket per NB-3200 Senice Lcvel Calculated Stress Intensity Allowable Stress (ksi) (ksi) Normal /Uoset (Primarv) 17.5'- 1.5Sm = 25.5 Nonnal/ Upset (Primary t 25.5 3.0Sm = 51.0 l Sec. excluding thermal bending) Normal / Upset (Primary v 35.0 N/A 1 Secondarv) Senice Level C 17.5 2.25Sm = 3 8.25 Senice Level D 23.0 3.0Sm = 51.0 Max. Cumulative Usage 0.021 l1.0

• Element local stres - the averap stress across the s:ction is 15.1 ksi<25.5 ksi.

A-3: Pipe. Elbows and Components per NB-3600 Senice Level Calculated Stress Intensity Allowable Stress (ksi) (ksi) Normal /Ucset (Primand 6.0 1.5Sm = 25.5 Normal / Upset (Primary - 5.5 3.0Sm = 51.0 Sec. excluding thermal bending) ' Normal / Upset (Primary - 63.I N/A Secondan-) i Senice Level C 6.0 2.25Sm = 38.25 Senice Level D i 12.0 3 OSm = 51.0 Max. Cumulathe Usage 1 0.001 11.0 _ Thermal Exo. (Ec.12) l 20.9 l 3.0Sm = 51.0 N j

Ma e 4 3 n ?e M 3 hD rn a ~ 4

• O*s A

I :,- ce @d) (i) 0 @Ni

a

= M N / "# a/@ e O s 1 k_ x j. Ab z p ~ e g ~ .O 2 1EE Ia> $ r= = a 1 E' g a y 4 w t am

-. ~. - - 4-

. c.

i ATTACHMENT 2 i ADDITIONAL INFORMATION IN SUPPORT OF NRC'S REVIEW OF PECO ENERGY'S REQUEST TO RESUME OPERATION J ie i' l h. 5 I. I i i i a t t ? J f i l ) h I i l i. J i t l .i i + h A 4 I i a I

i I s.. 's Provide the development of the loads during normal operation and paahn accident . conditions that were used to establish the structural integrty of the Core Spray Line (CSL) l clamp design at Peach Bottom Atomic Power Station (PBAPS) Unit 3. i

Response

The loads applied to the finite element model (FEM) were obtained from the analysis of the j core spray pipe. The core spray model is provided in Figure 1 A of GENE 771-080296, Rev.

2. The CSL was modeled in conjunction with the core spray nozzle thermal sleeve, the T-l box, and the reinforcement bracket to the pipe support joint just before the shroud penetration location.

i. The analysis included the cases as (1) design condition (no crack) and (2) with full t separation of the CSL and T-box. To simulate the separation condition, all the plate elements,300 degree circumference, between the T-box and the cort spray pipe, before the weld of the bracket, are assigned with negligible Young modulus. The model has also i considered that the downcomer has cracked and is tied together by a link at the location I of the clamp modification. The force can be transferred through the joint, but the moment is released. Weight of the linkage (300lb) was included in the analysis model The Engineering Computer Program SAP 4G07 was used to calculate the affect of the piping system due to thermal expansion, weight and seismic loads. 9 Thirteen load cases are analyzed. The analysis cases are summarized in Table 1 of GENE-l 771-960295, Rev 2. Description of each analysis case are in the following paragraphs. THERMAL CASES { The first case assumes the core spray pipes are connected to the T-box as the original l design condition. This is normal operating condition in which the Reactor Pressure Vessel (RPV) expands radially with carbon steel expansion coefficient and the core spray line ] expands with stainless steel expansion coefficient. The second case is the same as Thermal Case 1 except full separation of T box and CSL pipe is assumed. WElGHT ANALYSIS Weight analysis as applied to normal operating conditions has been performed Full #pe separations at the T-box is assumed to calculate the maximum loads on the brackets. 1 SEISMIC LOADS BY STATIC ANALYSIS Seismic loads acting on the piping system are caused by the response of the reactor building structure and reactor pressure vessel. The seismic loads are defined as the static i seismic coefficients. The Safety Shutdown Earthquake (SSE) accelerations,1.25g and 0.3 g for the horizontal and vertical SSE loads, are calculated to compare with the results from response spectrum analysis. The greater values are used in the load calculations. SEISMIC ANCHOR DISPl.ACEMENTS Static analyses are performed for the relative displacements between the shroud penetration movement and the CSL nozzle due to Operational Base Earthquake (OBE) event, which is 1.2* In both E-W and N-S directions. This load is the major contribution to the fatigue usage factor of the pipe, the brackets, and the clamp. Run #7 and #8 assume that the T-box and core spray pipe are separated. Run #10 and #11 assumed no separation. I v ..,_.i_, -

HYDRAUUC TRANSIENT LOADS The hydraulic transient is shown in design specification, 25A5341, Sheet 5 of this specification, and specifies that the core spray flow is drdW ilnearly in 20 seconds. The load in the piping system is very small. A hydraulic transient analysis was performed using 10 seconds instead of 20 seconds, which is conservative. The maximum pipe segment force amplitude is less than 20 lb. An example d pipe segment force time history is shown in Figure 1. The transient load is negligible for the piping analysis in the finite element of the downcomer clamp, the vertical distance form the horizontal centerline of the downcomer pipe at the shroud location to the free end of the pipe was made to coincide with the location of node 318 d element 181 of the piping analysis model. The forces and moments at node 318 were applied to the end of the vertical pipe of the FEM used in this analysis. Two load direction combinations were considered due to non-symmetry of the FEM about the x-axis: 1 (+)x and (+)y, and 2 (+)x and (-)y; the FEM is symmetric about the y-axis. The horizontal force in the x-direction (Fx) and the moment about the y-axis (My) were applied together, and the horizontal force in the y-direction (Fy) and the n:oment about the x-axis (Mx) were applied together. The absolute value of the magnitude of the forces and moments are provided below. Load Type Fx [ kips] Fy [ kips] Fz [ kips] Mx [in-kips] My [in-kips] Thermal 0.4 0.1 1.0 1.4 9.9 Weight 0 0 0.1 0.1 0.2 OBEL-X 0 0 0 0.7 0.3 OBEL-Z 0 0 0 0.1 0.5 OBED-X 0.3 0.8 0.4 20.3 7.1 OBED-Z 1.1 0.3 1.3 7.4 28.2 LOCA 0.6 0.1 0.9 1.7 14.6 SSEl-X 0 0 0 0.9 0.4 SSEl-Z 0 0 0 0.2 0.7 UNIT LOADS 1.0 1.0 1.0 10.0 10.0 It is noted that the load applied to the clamp design for OBED-X and OBED-Z are the maximum loads in the design. These loads are calculated based on the assumption that the relative displacements between the shroud to RPV nozzle is 1.20 inches. Later analysis of the shroud assuming partial crack was performed and the calculated relative displacements is reduced to 0.397 inches. This is only about one third of the forces and moments used in the calculation. l ~

. s QUESTION #2 If some loads were considered negligible, provide the basis for the assumptions. RESPONSE #2 The negligible loads were included in the previous response. QUESTION #3 Provide the back-up stress calculations related to the threaded fasteners to demonstrate ASME code compliance. RESPONSE #3 The threaded fastener design of the CSL clamp was performed using the ASME Code, Section NG as a guide. This design information was included in as part of the CSL Downcomer Bracket Stress Assessment Report, GENE-771-99-0295, Rev 2. Appendix A, to this Attachment, consists of the supporting calculations for the threaded fasteners design. The calculated stress intensity values included in the Stress Assessment Report have been highlighted in Appendix A. QUESTION #4 Provide the basis for the assumed crack width upon activation of in core spray system. RESPONSE #4 Upon activation of the Emergency Core Cooling System (ECCS), the hot riser pipe (304 material) is cooled to a temperature well below the initial high 1 temperature of 550' F. However, the clamp hardware itself (U-bolt) is made of a different material, namely XM 19, with a lower coefficient of thermal expansion than that the 304 riser pipe. The clamp hardware remains at a temperature of 550' F during this event. Thus, the riser pipe between the base of the upper i clamp and U-bolt restraint on the bottom elbow contracts relative to the clamp hardware between the same distance. This, in turn, causes the crack in the upper weld to open up. Thus, the amount of this initial crack opening is calculated based on the length over which the differential expansion acts during the event. The differential thermal movement described, applies to the clamp hardware on j all four core spray line risers.

I i e e , e.. QUESTION #5 Provide justification for using a dual clamp design at one location and a single clamp design at the other three locations. RESPONSE #5 ' The dual clamp design to be installed on the 'D' downcomer was designed and fabricated prior to refueling outage 3R10 (fall 1995). The design repairs the crack indications identified in the Heat Affected Zone (HAZ) of the sleeve, below the J l pipe / sleeve weld. This design also provided for contingencies if any additional-crack indications were identified in the 'D' downcomer (or any other downcomer) during 3R10. The single clamp design, to be installed on the 'A', "B", and 'C', downcomers, also repairs the crack indications identified in the HAZ of the sleeve, below the - pipe / sleeve weld. This design was the original design for the "D" downcomer l Indication, developed prior to adding in additional contingencies. Fabrication and ' i installation of the single clamp design is adequate to repair the downcomer Indications found cn 'A', 'B", and 'C' downcomers. The contingencies are~not needed because all cracks found on the "A", "B", 'C', and "D" downcomers were in the same location. Use of the double clamp is not necessary, it is a much more conservative repair than needed, and is being used since it is available. l ~.

e e e 6 e APPENDIX A - - ATTACHMENT 2 BACK UP STRESS DATA FOR THE THREADED CONNECTORS f t Z Y -.e s J I i 4 s .,a w ~ e---- ~ - r4--w-- +wo- ->-vr w, w ,- ~, -, - ---v -r

5.4 Bolt Dimensions and Loads I ? Applied Profonds 100ftlbf 75.ft.Jbf Preload Preload clamp _ halves * (.20)-(.75 in) Ubolt * (.29)-(.75 in) Ubolt = 600d lbf Prcload clamp, halves - 8000.lbf Preload 100 ft Ibf Preload connecting _ rod * (,20).(},oo.in) Preload connecting _ rod = 6000.lbf 5.4.1 Thread Dimensions (Connecting Rod) The thread dimensions for 1.00-12UNF ar,e obtained from ANSI B 1.1-1982. En_, max. 9535 in (maximum pitch diameter of intemall thread) Ds,. min. 9368.In (minimum major diameter of extemal thread) Es_tain. 9332 in (minimum pitch diameter of extemal thread) Kn_ max. 925 in (maximum minor diameter of intemal thread) dm. 8990 - 1.00 in (Mean Diameter) d.1.00 in (Major Diameter) 7 I (number of thread i 1 Le, !.00 !n n, m perinch) g, 12 in (Laad) (length of thread engagement) The thread dimensions for 0.75-16UNF are obtained from ANSI 81.1-1982. En_mec :.7159in (maximum pitch diameter of intamal' thread) Ds_ min i.7'91in (minimum maior diameter of extemal thenad) Es_c.m.. < 029-in (minimum pitch diameter of extemaf thread) Kn_ max. 696 in (maximum minor diameter of intamal thread) .640-0.75 dm i In (Mean Diameter) d a 0.75 in .(Major Ofameter) 3 16 (number of thread g j 1 in (Lead) j g, y3,.a n. in per inch) 16 (length of thread engagement) m l.

...i. PAA'Md4AW S'f Me?" AAPL/tAftf E i i 1 i i i 5.6 Bolt / Nut Thread Stress Analysis / The thread shear area was calculated using the methodology and equqtions pven in Appondix B, Paragraph B2 of Reference 13. 5.6.4 Internal Thread Shear Area (Nut) ~1 ASn.. n n Le Ds_ min. g .37733-(Ds_ min - En_ max) A5nl= 1.244 in: 5.6.2 Nut Thread Shear Stress The applied bolt loads for all operating conditions aro less than the applied preload. Therefore, the applied preload condition stresses bound all Normal, Upset, condition stresses. 9 \\ 1

a s a 5.6.2.1 Normauupset/ Emergency Condition Nut Thread Shear Sness Preload clamp halves M 'NNU IM' T bi"I* L*"*! A B C. 6 Sy_XM19 t palcad

• Mn (Reference 2, Paragraph 6 8 3232.1(b))

^ 43I F85 T preload - t,,, Limit _ Level _A_B_C - 1.059 104. psi 1 5.6.3 External Thread Shear Area (Bolt) l i 1 2 ass n n Le Kn_ max- .57735-(Es_ min - Kn_ max), ass = 0.924.In i 5.G.4 Belt Thread Shear Stress 5.6.4ci Normal / Upset / Emergency Condition Bolt Thread shear Stress t_ Limit _Leve!_A_B_C :=.6 Sy_X 119 Preload clamp _ halves preload

• ass

{ T preload = 8653. psi t_ Limit _ Level _A_.B_C - 1.95910 psi T 5.7 Bolt Section Property Calculations 5.7.1.75 " Dia Bolt Shank 5.7.2 1.00 " Dia Conne'pting Rod j Section Section 2 .75 2 A shank. n 7 in 3 ,y, ,g A shank = 0.42.@ 2 A rod = 0.785.in n-(.75 in)# n.(l.0 in)4 I shank

• g j g, I shank - 0.016.In

!,.gg - 0.049.lu# 4 i l ....-{ - . _. =....,...

3 s. 5.7.3 1.75 " Dia circular Section 5.7.4 1.75 " Dia circular Section with .75" internal thread 2 1 2i 1.75 [1.75 .75 Ubolt2

• K'[ - y in

'In A

-,7 in A Ubolti ' ~' 2 j

2 2 i A Ubolt! = 2.405.is AUbolt2 = 1.963.in x-(1.75 in)4 x ; (1.75 in)# (.75 in)"i I Ubolt2 g I Ubolti 64 d I Ubolti = 0.46.in' I Ubold = 0.445.in I Ubolt! I Ubolt2 3 2 Ubolti = 0.526.in Z Ubolt2 = 1,75.in 2 Ubolt2 = 0.508.id Z Ubolt1 ' l.75 in 2 2 E.0 U-BOLT STRESS CALCULATION Determing the required O.D. for the threaded section to equal a exial stfength of the.75" "* diameter bolt. d g. 75 in bolt O. D. d 1 =.75 in bolt hole diameter in U bolt o. fd -d d a = 1.061.in required O.D. of threaded section of U-bok 2 2 d i / The actual diameter of the U-bolt is 1.75 with a minimum dimension of 1.5 being accepted on NCR No: 1EXFN-N-02, 6.1 Stress Calculations - curved section Thio calculation conservatively assumes that me U-bolt is cantilevered fr'cm its center and that that !s the only point supported by the riser elbow. Preload Ubolt 4.265 in Ubolt_ bending ' ~~ z Uboltl O II bending = 48636. psi U Preload Ubolt ' U b olt

• 00II

^ Ubolti t k 6 ].

3 + o t 2 SI. 2.'! 8 Ubolt_ bending 2 2 - 4* bolt 5I ~ 48891. psi 1.5 Sm_XM19 =44175. psi [CeMSf f Wa NV8 Since this approach resulted in a stress intensity slightly higher than the 1.5 Sm for Pm + P stress, the fact that the U-bolt contacts the riser elbow was taken into acccunt. A fmite element model using beam elements to represent the Ubolt and elastip boundary elements to represent ow was created. The results from the finite element analysis gave Pm + Pb results o si. 6.2 Stress Calculations straight section at lower clamp This calculation efetermines the stresses resulting from the U-bolt contpeting the elbows radius and 6.625 Length of the moment arm neglecting the short distance the length 7 in - 6.0 in U-bolt's contact pointis above the bottern point of the riser elbow. Load. Preload Ubolt The approximate angle of the tangent at the point where the U-bolt contacts 0,15.0 deg the elbow (at the center of the elbow). mponent of the fdtce trying the bend El Preload Ubolt sin 0 F1 = 1552.9.lbf the U-bolt around th'e lower clamp. M. length F1 M = 14462.in lbf 1 M a bending ' z Ubottl bending = 27435. psi Preload Ubolt tension *@ hN* N 8 tension ' A Ubolti U total

• O tention ' G bending total - 2.998. t 0* pst

< 1.5 Sm for XM-19 a 1.5 Sm_XM19 = 4.415 10'. psi j -. -i

1 ye o t 7,0 BEARING STRESS EVALUATION Per Subsection NG-3227 of Reference 2, the average bearing stress for at: Service i Loadings shall bc limited to Sy at temperatureexcept the bearing stress ;under bolt heads which is limited to 2.7Sy. 7.1 Nut to Clamp Dearing Stress \\ 7.1.1 NormalIUpset/ Emergency /Faultad/ Acoustic Condition Bearing Stress i '.812 2}! [j - (1.25 in)2 A bearing * { -K'j 3 in 3 2 Preload clamp _ halves i G bean *ng * .4., si < 2,7Sy for 304L,316L and XM19 a bdg 10.0 TENSILE STRESS AREA threads per inch D.. 75 in basic major pftch diameter 16 n7 inside diameter of externally threaded part, d. 0 in d = zero for a solid part Ks_rnin.. (.6763 .0015) In minimum minor diameter of external th' read 2 0.9743 2 As. 0.7854 D - M== 0.373 4 11.0 DIRECT TENSILE STRESS AND TORSIONAL STRESS (Reference 13, / Appendix B) (F = preload applied on externally threaded part) F = Preload clamp _ halves At. o.755'l l'.s_rnin d .v - 0.3 5 8. In (Ar - pres at the mittfrriutts wriir eor diwri t,ter I 2 2 St. (St = direct tensile stress) 5t -Msi < Sm for XM19 t he direct torstonal stress is calculatec tor a'thresced part operating witnin tne etastic limit. (T1 = wrench tcrque t ansmitted through the thread,ed section, r 100 12 approximately equal to half of the total wrench torque. Reference 14 in lbf Tg 2 page 249) ,}}