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{{#Wiki_filter:ENCLOSURE | {{#Wiki_filter:ENCLOSURE 4 MONTICELLO NUCLEAR GENERATING PLANT SUPPLEMENTAL INFORMATION REGARDING CYCLE 25 INSERVICE INSPECTION | ||
==SUMMARY== | |||
REPORT -CORE SHROUD SUPPORT FLAW EVALUATION EC-1 8095 EVALUATION OF THE MONTICELLO SHROUD SUPPORT PLATE UPLIFT LOAD WITH INDICATIONS IN THE H8 AND H9 WELDS (NON-PROPRIETARY VERSION)(15 pages follow) | |||
Non-Proprietary. | Non-Proprietary. | ||
Vendor Proprietary Information has been Redacted. | Vendor Proprietary Information has been Redacted.~ Structural Integrity Associates, Incy File No.: 1100626.301 tr Project No.: 1100626 CALCULATION PACKAGE Quality Program: E Nuclear El Commercial PROJECT NAME: Evaluation of the Monticello Shroud Support Plate Uplift Load with Indications in the H8 and H9 Welds CONTRACT NO.: 00001005 Release 27, Amendment 001 CLIENT: PLANT: XCEL Energy Monticello Nuclear Generating Plant CALCULATION TITLE: Evaluation of Shear Capacity of Monticello Shroud Welds H8 and H9 Document Affected Project Manager Preparer(s) | ||
~ Structural Integrity Associates, Incy File No.: 1100626.301 tr Project No.: | |||
E Nuclear El Commercial PROJECT NAME:Evaluation of the Monticello Shroud Support Plate Uplift Load with Indications in the H8 and H9 | |||
&D on afe Revision Description Approval Checker(s) | &D on afe Revision Description Approval Checker(s) | ||
Revision Pages Signature | Revision Pages Signature | ||
& Date Signatures | & Date Signatures | ||
& | & Date A 1 -15 Draft for Client Review Marcos. L. Herrera Preparer: MLH 4/29/11 S. S. Tang/Sandra Sowah 4/29/11 Reviewer: Hal Gustin/Jay Gillis 4/29/11 01 -15 Initial Issue Preparer: Marcos. L. Herrera S. S. Tang MLH 5/2/11 SST 5/2/11 Sandra Sowah SS 5/2/11 Reviewer: Hal Gustin 5/2/11 Jay Gillis 5/2/11 Gn.taInI Vender Proprietary I r nttil Page 1 of 15 F0306-01RI Non-Proprietary. | ||
MLH 4/29/11 S. S. Tang/Sandra Sowah 4/29/ | Vendor Proprietary Information has been Redacted.CshwC"iuhitegd* | ||
Hal Gustin/Jay | AW00Ociates b Table of Contents | ||
Marcos. L. Herrera S. S. | |||
Hal Gustin 5/2/ | |||
Vendor Proprietary Information has been Redacted. | |||
CshwC"iuhitegd* | |||
AW00Ociates | |||
==1.0 INTRODUCTION== | ==1.0 INTRODUCTION== | ||
..................................................................................................... | ..................................................................................................... | ||
4 2.0 TECHNICAL APPROACH ..................................................................................... | |||
..................................................................................... | 4 3.0 ASSUMPTIONS | ||
.................................................................................................... | .................................................................................................... | ||
5 4.0 DESIGN INPUTS ..................................................................................................... | |||
6 5.0 CALCULATIONS | |||
................................................................................................... | ................................................................................................... | ||
6 5.1 Pressure Difference across Shroud Support Plate ........................................ | |||
6 5.1.1 Top of Shroud Support Plate Pressure Calculation | |||
.................................... | .................................... | ||
6 5.1.2 Shroud Support Plate Pressure Difference Calculation | |||
................................ | ................................ | ||
7 5.2 Postulated Crack Profile .............................................................................. | |||
7 5.3 Limit Load for Shear ..................................................................................... | |||
8 5.3.1 App lied Loads .............................................................................................. | |||
8 5.4 C rack G row th ................................................................................................ | |||
9 5.4.1 Crack growth in circumferential direction | |||
.................................................. | .................................................. | ||
9 5.5 Evaluation C ases .......................................................................................... | |||
9 6.0 RESULTS OF ANALYSIS ........ ; ............................................................................ | |||
........ | 10 | ||
; ............................................................................ | |||
== | ==7.0 CONCLUSION== | ||
S AND DISCUSSIONS | S AND DISCUSSIONS | ||
................................................................. | ................................................................. | ||
10 8.0 R EFER EN C ES ...................................................................................................... | |||
10 This doeumzrnt eontains ven~der proprita~ry a nfermaition. | |||
Proprietaryifraini lindiented by a bar in the right hand margin.File No.: 1100626.301 Page 2 of | Proprietaryifraini lindiented by a bar in the right hand margin.File No.: 1100626.301 Page 2 of 15 Revision: | ||
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Non-Proprietary. | Non-Proprietary. | ||
Vendor Proprietary Information has been Redacted. | Vendor Proprietary Information has been Redacted.Cjsirucmuu h#C orY Asockites, Inc List of Tables Table 1: Load Sum m ary .................................................................................................... | ||
Cjsirucmuu h#C orY Asockites, | 12 Table 2: Design Input for Shroud Support Plate Pressure Difference Calculation | ||
............. | ............. | ||
12 Table 3: M aterial Properties at 550 0 F ............................................................................... | |||
12 Table 4: Pressure Differential across the Shroud Support Plate ......................................... | |||
13 Table 5: Uplift Load on Shroud Support Plate ................................................................. | |||
13 Table 6: V ertical Seism ic Load ......................................................................................... | |||
13 Table 7: Total Upward Shear Force ................................................................................... | |||
13 Table 8: Limit Load Evaluation Results for Compound Crack Profile .............................. | |||
14 Table 9: Limit Load Evaluation Results for Surface Crack Profile ................................... | |||
14 List of Figures Figure 1. Jet Pumps Inspection Illustration | |||
....................................................................... | ....................................................................... | ||
15 File No.: 1100626.301 Revision: | |||
0 Page 3 of 15 F0306-01 RI Non-Proprietary. | |||
Vendor Proprietary Information has been Redacted. | Vendor Proprietary Information has been Redacted.v sh4wiphw egi AssWOCIaes./ | ||
v sh4wiphw egi AssWOCIaes./ | |||
f. | f. | ||
==1.0 INTRODUCTION== | ==1.0 INTRODUCTION== | ||
During the Spring 2011 outage, inspection of the Monticello shroud support plate weld H8 and | During the Spring 2011 outage, inspection of the Monticello shroud support plate weld H8 and weld H9 was performed. | ||
Visual inspection (EVT1) coverage was obtained from jet pump JP20 to JPI | Visual inspection (EVT1) coverage was obtained from jet pump JP20 to JPI and JP10 to JP 11, as identified in Figure 1 [1]. This accounts for approximately 17% of the H8 and H9 circumference | ||
[1]. An additional 64 inches of inspection coverage was acquired with visual inspection VT-3 on the top side of the weld [1] in the area between all the jet jumps. The visual inspection revealed cracking in the shroud support legs but no indications were identified in the welds H8 and H9.This evaluation is performed to quantify the structural margin retaining the shroud support plate | [1]. An additional 64 inches of inspection coverage was acquired with visual inspection VT-3 on the top side of the weld [1] in the area between all the jet jumps. The visual inspection revealed cracking in the shroud support legs but no indications were identified in the welds H8 and H9.This evaluation is performed to quantify the structural margin retaining the shroud support plate H8 and H9 welds after one cycle of additional operation assuming plastic collapse in shear to be the applicable failure mode because the most significant loading is the uplift load due to the vertical seismic and the pressure difference across the shroud support plate.2.0 TECHNICAL APPROACH The technical approach used for this evaluation is based on the BWRVIP-76 | ||
[2], limit load approach. | [2], limit load approach.The limit load analysis for shear failure is developed based on the approach for determining the limit load for an axial crack in the shroud as presented in [2] and summarized below. Consistent with the BWRVIP methodology in [2], the failure mode of the Alloy 600 and corresponding weld materials is considered to be the net section (plastic) collapse, because of the very high ductility of these materials at reactor operating temperatures. | ||
The limit load analysis for shear failure is developed based on the approach for determining the | Also, the fluence in this region is not high enough to impact the material ductility. | ||
The limit load for an axial crack assuming tensile failure of the remaining ligament is expressed in Section E. 1.2 of [2] as: By similar approach, the shear failure limit load for a crack in a circular weld can be expressed as: (SF)S = oj Lt (2)where: S ý shear force due to uplift load SF = safety factor File No.: 1100626.301 C ontains Vener Proprietary-inf-r..atin Page 4 of 15 Revision: | |||
Also, the fluence in this region is not high enough to impact | 0 F0306-01 RI Non-Proprietary. | ||
The limit load for an axial crack assuming tensile failure of the remaining ligament is expressed | Vendor Proprietary Information has been Redacted.vIkfegdly# | ||
AWssOcjS, WOc asf = shear flow stress L = length of uncracked circumference in circular welds (H8/H9)t = thickness of shroud support plate.Using the maximum shear theory or Tresca criteria, the maximum shear stress at yield is half the maximum yield strength. | |||
Vendor Proprietary Information has been Redacted. | The shear flow stress can be expressed as: vsf = Gf/2 There are no plant specific safety factors for the Monticello shroud [1]. Per Section D.5 in Reference 2, required minimum safety factors of 2.77 for normal/upset (Level A/B) conditions and 1.39 for emergency/faulted (Level C/D) conditions are used in this evaluation. | ||
vIkfegdly# | In limit load evaluation, elastic-perfectly plastic material properties are used.3.0 ASSUMPTIONS The following assumptions are used: a. Loading in weld H8 and weld H9 is assumed to be pure shear due to the most significant loads being the vertical seismic and the pressure difference across the shroud support plate.b. Material properties of Alloy 600 compatible weld metal are assumed to be the same as the Alloy 600 base metal.c. The shear load is assumed to be evenly distribution between the weld H8 and weld H9.d. The shear load is assumed to be evenly distributed in the remaining ligament of each weld.e. For uninspected region, through-wall cracking is assumed. This is conservative since no credit is taken for the uninspected region.f. For inspected region, surface cracking with depth of 75% of the plate thickness is assumed.This assumption is based on the general evidence provided by the BWR fleet shroud cracking data. The flaws generally arrest at 2/3 of the wall thickness, so the assumption of a 75% wall flaw is conservative. | ||
The shear flow stress can be expressed as:vsf = Gf/ | |||
In limit load evaluation, elastic-perfectly plastic material properties are used.3.0 ASSUMPTIONS The following assumptions are used:a. Loading in weld H8 and weld H9 is assumed to be pure shear due to the most significant | |||
This is conservative since no | |||
: g. The SSE accelerations are twice as large as the OBE accelerations. | : g. The SSE accelerations are twice as large as the OBE accelerations. | ||
: h. The vertical flexural shear from the moment induced by the horizontal acceleration due to | : h. The vertical flexural shear from the moment induced by the horizontal acceleration due to the jet pump weight on the support plate is assumed to be negligible. | ||
It was estimated that | It was estimated that this upward flexural shear is less than 5% of the total uplift shear load.i. The material is considered to behave in an elastic-plastic manner, which is consistent with BWRVIP methodology for reactor internals in low fluence regions.j. Crack growth in the depth direction is not considered since the assumed crack depth is based on flaw depths observed from BWR fleet operating experience. | ||
Subsequent growth is | Subsequent growth is minimal due to excellent Monticello water chemistry conditions in the lower plenum.k. Seismic and LOCA are conservatively combined in order to provide added margin to the evaluation and further justify the maximum flaw depth based on BWR fleet operating experience. | ||
File No.: 1100626.301 Page 5 of | File No.: 1100626.301 Page 5 of 15 Revision: | ||
0 F0306-OIRI Non-Proprietary. | |||
Vendor Proprietary Information has been Redacted. | Vendor Proprietary Information has been Redacted.V _W9W k*#ww.Ihegl AWOSSoca, Wnc 4.0 DESIGN INPUTS The following dimensions are used in the evaluation: | ||
V _W9W k*#ww.Ihegl | |||
Reactor vessel inside diameter (ID): 17.167 ft [1]Shroud plate thickness: | Reactor vessel inside diameter (ID): 17.167 ft [1]Shroud plate thickness: | ||
2.5 inches [3]Shroud ID: 159.75 inches [4]Shroud thickness: | 2.5 inches [3]Shroud ID: 159.75 inches [4]Shroud thickness: | ||
1.75 inches [4]Design AP across shroud support plate for Levels A through D 100 psi [1]Per Reference 1, the vertical earthquake acceleration is 0.06g.The vessel internal component loads and water loads are obtained from Reference 13 and summarized in Table 1.The input used to calculate the pressure differential across the shroud support plate for different operating conditions are obtained from Reference 7 and summarized in Table 2. The maximum AP | 1.75 inches [4]Design AP across shroud support plate for Levels A through D 100 psi [1]Per Reference 1, the vertical earthquake acceleration is 0.06g.The vessel internal component loads and water loads are obtained from Reference 13 and summarized in Table 1.The input used to calculate the pressure differential across the shroud support plate for different operating conditions are obtained from Reference 7 and summarized in Table 2. The maximum AP for Level A/B is 29.03 psid for the EPU conditions | ||
[7]. For Level C/D, the maximum AP is 47 psid | [7]. For Level C/D, the maximum AP is 47 psid from the 113% OLTP. Since it is not clear if the Level C/D reactor internal pressure difference (RIPD)considers the decompression of the annulus region following a postulated recirculation line break (RLB) event (typically the Level C/D RIPD is given as the main steam line break pressure difference), a bounding methodology is used in this calculation to calculate an uplift load on the shroud support plate.Per Reference 1, the Code of Construction is Section III, 1965 with Summer 1966 Addenda [19]. The allowable stress intensity (Sn) is 23.3 ksi [1]. The material yield strength (Sy), ultimate strength (Sj)and allowable stress intensity for Alloy 600 are obtained from Reference 8 at 550 'F for conservatism and summarized in Table 3. As compared to the allowable Sm from Reference 19 stated in Reference 1, the Sm from different Code Editions remains the same.The input used to calculate the pressure differential across the support plate is summarized in Table 4.The shroud support plate material is Alloy 600 [15].The end of evaluation period (EoEP) is 24 months [1].5.0 CALCULATIONS 5.1 Pressure Difference across Shroud Support Plate 5.1.1 Top of Shroud Support Plate Pressure Calculation The pressure at the top of the shroud support plate for normal condition, Psihoud, is a required input for determination of the pressure difference across the shroud support plate for the postulated Recirculation Outlet Break case. Considering hydrostatic pressure, this may be calculated by: File No.: 1100626.301 Page 6 of 15 Revision: | ||
a bounding methodology is used in this calculation to calculate an uplift load on the shroud | 0 F0306-OIRI Non-Proprietary. | ||
Vendor Proprietary Information has been Redacted.v sh n I h*t g A. aSciate, c.°fhrOud= Po h (3)1728. vf where PO = pressure at the water surface, psia h = water height from top of shroud support plate elevation to the water surface, in vf = specific volume of the water at the top of the shroud support plate, ft 3/lb =0.021 19ft 3/lb (based on annulus temperature, interpolated from [11]).Thus, Pshroud = 1025 + (512.5 -99.25)/(1728 x 0.02119)= | |||
1036.3 psia.The pressure in the lower head is higher than the pressure in the annulus because of the pressure added by the jet pumps. The pressure difference can be estimated from Reference 7 as the maximum differential pressure across the shroud support plate for the Level B condition, which is 29.03 psid.5.1.2 Shroud Support Plate Pressure Difference Calculation A conservative lower bound for the pressure above the support plate is the saturation pressure at the annulus temperature. | |||
A low pressure above the support plate is conservative because it maximizes lifting force on the plate due to the pressure differential across the plate. If the pressure below the plate is held constant and the pressure above the support plate is lessened, the upward force on the support plate is increased. | |||
Vendor Proprietary Information has been Redacted. | In normal operation, the lowest pressure in the reactor pressure vessel is the pressure in the steam dome. The saturation pressure at the annulus temperature is slightly less than the steam dome pressure because the annulus liquid is slightly subcooled. | ||
v sh n I h*t g A. aSciate, c.°fhrOud= Po h (3)1728. | From Reference 7, the maximum Level A/B pressure difference across the shroud support plate is given as 29.03 psid. This pressure differential is expected to exist at the instant of the postulated RLB event.A conservative lower bound for the pressure above the support plate, following the RLB event, is the saturation pressure at the annulus temperature. | ||
1036.3 psia.The pressure in the lower head is higher than the pressure in the annulus because of the pressure | Thus the bounding total pressure difference, AP, for the Level C/D conditions is given as: AP=Pshoud | ||
A low pressure above the support plate is conservative because it maximizes lifting force on the plate due to the pressure differential across the plate. If the pressure below | -Psat = (1036.3 + 29.03) -886.25 = 179.08 psid This pressure difference acts to lift the support plate upward.The pressure differentials across the shroud support plate are summarized in Table 4.5.2 Postulated Crack Profile From Reference 1, Welds H8 and H9 were inspected with EVT-1 from JP 20 to JP1 and JP10 to JP 11 (about 17% of the circumference), as shown in Figure 1 [4], with an additional 64 inches inspected File No.: 1100626.301 Page 7 of 15 Revision: | ||
In normal operation, the lowest pressure in the reactor pressure vessel is | 0 F0306-OIRI Non-Proprietary. | ||
From Reference 7, the maximum Level A/B pressure difference across the shroud support plate | Vendor Proprietary Information has been Redacted.VII~S&NOiauN Inftogi AssociatS, Inc with VT-3. The regions not inspected by VT-3 are the portion of the welds close to the jet pumps, as illustrated in Figure 1 [1].Thus, the uninspected regions are considered to be evenly distributed based on the jet pumps pattern, resulting in 10 uninspected regions as illustrated in Figure 1. These regions are conservatively to be cracked through-wall. | ||
Thus the bounding total pressure difference, AP, for | |||
-Psat = (1036.3 + 29.03) -886.25 = 179.08 | |||
as shown in Figure 1 [4], with an additional 64 inches inspected File No.: 1100626.301 Page 7 of | |||
Vendor Proprietary Information has been Redacted. | |||
VII~S&NOiauN Inftogi AssociatS, | |||
Length of weld H8 = 21rtRi=2*1rt(159.75/2+1.75)= | Length of weld H8 = 21rtRi=2*1rt(159.75/2+1.75)= | ||
2*iT(81.625) 512.865 | 2*iT(81.625) 512.865 in Length of weld H9 = 2rTRo=2*Tr(17.167* | ||
12/2)= 2*rT(103.002) | 12/2)= 2*rT(103.002) | ||
= 647.18 | = 647.18 in To simplify, an average length for welds H8 and H9 is used for evaluation. | ||
Average weld length for welds H8 and H9 = (512.865+647.18)/2 | Average weld length for welds H8 and H9 = (512.865+647.18)/2 | ||
=580.02 | =580.02 inch The inspection length inspected by VT-3 for each weld is approximately 64/2 = 32 inches.Using the average weld length, the following are obtained for each weld: Total inspected length = 0.17*580.02+32 | ||
= 130.60 | = 130.60 inches Total uninspected length = 580.02 -130.63 inches = 449.42 inches This corresponds to 449.42/10=44.94 inches for each uninspected region.5.3 Limit Load for Shear 5.3.1 Applied Loads 5.3.1.1 Uplift Load The uplift load is due to the pressure difference across the shroud support plate. The AP uplift area (UA) is calculated as: UA = 1"(Ro 2-Ri 2)=Tr(l103.002 2-81.625 2) = 12399.15 in2 The uplift loads due to the pressure difference for Level A/B and C/D are calculated and shown in Table 5.5.3.1.2 Vertical Seismic Load In Table 1, it is shown that the total weight of the jet pumps is 10 kips.. Also, the maximum water weight of 1080 kips from Table 1(b) is selected. | ||
Thus the total weight due to internal structure | Thus the total weight due to internal structure | ||
&periphery fuel, jet pumps and water weight is:Wt = 189 + 10 + 1080 =1279 | &periphery fuel, jet pumps and water weight is: Wt = 189 + 10 + 1080 =1279 kips File No.: 1100626.301 Page 8 of 15 Revision: | ||
0 F0306-OIRI Non-Proprietary. | |||
Vendor Proprietary Information has been Redacted. | Vendor Proprietary Information has been Redacted.hxtegdl ~Y AociatS, Inc.The vertical seismic acceleration is 0.06g. This is assumed to be for OBE.The total vertical seismic load for OBE and SSE is summarized in Table 6.The total upward shear force is summarized in Table 7.5.4 Crack Growth Crack growth in the depth direction is not included since the depth used in the evaluation is consistent with the depths based on BWR fleet operating experience. | ||
hxtegdl ~Y AociatS, Inc.The vertical seismic acceleration is 0.06g. This is assumed to be for OBE.The total vertical seismic load for OBE and SSE is summarized in Table 6.The total upward shear force is summarized in Table 7.5.4 Crack | |||
In addition, due to Monticello's excellent water chemistry in the lower plenumn, subsequent crack growth will not be significant. | In addition, due to Monticello's excellent water chemistry in the lower plenumn, subsequent crack growth will not be significant. | ||
5.4.1 Crack growth in circumferential direction Per Reference 2, the crack growth rate is 5x1 0-5 in/hr. This is used for conservatism regardless of | 5.4.1 Crack growth in circumferential direction Per Reference 2, the crack growth rate is 5x1 0-5 in/hr. This is used for conservatism regardless of plant specific water chemistry. | ||
For 10 uninspected | For 10 uninspected regions, with 2 crack fronts for each region since a through-wall crack is used, the total crack growth Al for 24 months is: AI= 1O*2*5xl0 5*2*365*24 | ||
= 17.52 inches Therefore, the remaining length of un-cracked circumference at the EoEP is L =130.60 -17.52 = 113.08 inches 5.5 Evaluation Cases Two crack profiles are used to evaluate the structural margin retaining the shroud support plate weld H8 and weld H9. Each of these contains significant conservatisms, which compensate for any uncertainty in the flaw depths. It is important to note that BWR shroud cracking history, of which there is a significant amount, has shown that typically cracks in shroud welds grow to approximately two-thirds of the shroud wall and then appear to become essentially inactive. | |||
= 17.52 | This is particularly expected for Monticello's case because of the excellent water chemistry experienced in the vicinity of the indications on the lower side of H8 and H9. These two crack profiles are: (a) Multiple Cracks: A through-wall crack is postulated in the uninspected regions and a remaining ligament of 1/3 of the plate thickness in the inspected region is postulated since inspection was performed on the top side only. The 1/3 wall remaining ligament is based on field experience for BWR shroud welds.(b) Full Circumferential Surface Crack: A surface crack at the bottom plate surface extending along the circumferential length of Weld H8 and H9 with a crack depth at 75% of the support plate thickness is postulated. | ||
This corresponds to a remaining ligament of 0.625 inches in the support plate.File No.: 1100626.301 Page 9 of 15 Revision: | |||
This is particularly expected for Monticello's case because of the excellent water chemistry experienced in the vicinity | 0 F0306-OIRI Non-Proprietary. | ||
This corresponds to a remaining ligament of 0.625 inches in | Vendor Proprietary Information has been Redacted.Vjj~hVucuhfIW latoil AWOMOctS, Wnc 6.0 RESULTS OF ANALYSIS The limiting shear force due to limit load failure criteria can be calculated using Eq. (2). The flow stress is taken as 3 Sm per Reference 9 as used in Reference 20.The analysis results are summarized in Tables 8 and 9 for the two crack profiles described in Section 5.5. It is shown that the safety factors are 14.96 and 2.77 for Levels A/B and C/D, respectively for the multiple crack case. For the surface crack case, the safety factors are 57.58 and 10.67 for Levels A/B and CD, respectively. | ||
Vendor Proprietary Information has been Redacted. | |||
Vjj~hVucuhfIW latoil AWOMOctS, | |||
These are higher than the required safety factors of 2.77 and 1.39 per Reference 2. | These are higher than the required safety factors of 2.77 and 1.39 per Reference 2. | ||
==7.0 CONCLUSION== | ==7.0 CONCLUSION== | ||
S AND DISCUSSIONS An analysis was performed to evaluate the capacity of the remaining length in the Welds H8 and H9 | S AND DISCUSSIONS An analysis was performed to evaluate the capacity of the remaining length in the Welds H8 and H9 to prevent the up lift of the core shroud. It is shown that, for an EoEP of 24 months, the calculated safety factors of for Levels A/B and C/D conditions in Weld H8 and H9 are significantly above the required safety factors of 2.77 and 1.39, respectively, for both conservative flaw configurations analyzed.These results demonstrate that, even with the postulated flaws in welds H8 and H9, the structural integrity of the shroud support plate is assured. | ||
These results demonstrate that, even with the postulated flaws in welds H8 and H9, the structural integrity of the shroud support plate is assured. | |||
==8.0 REFERENCES== | ==8.0 REFERENCES== | ||
: 1. Xcel Energy Design Information Transmittal (DIT), "Shroud Support Plate Uplift Analysis," | : 1. Xcel Energy Design Information Transmittal (DIT), "Shroud Support Plate Uplift Analysis," Tracking Number EC, Date 5/2/2011, DIT No. 3, S1 File 1100626.207. | ||
Tracking Number EC, Date 5/2/2011, DIT No. 3, S1 File 1100626.207. | : 2. BWR Vessel and Internals Project: BWR Core Shroud Inspection and Flaw Evaluation Guidelines (BWRVIP-76), EPRI, Palo Alto, CA, BWRVIP 1999, TR-1 14232.3. Chicago Bridge & Iron Co. Drawing 35 Rev 5, "Plan of Shroud Support 17'2" ID, 63'-2" INS Heads Nuclear Reactor," No. NX-9310-28, SI File 1100626.201. | ||
: 2. BWR Vessel and Internals Project: | : 4. General Electric Drawing 886D487, "Reactor Vessel," No. NX7831-7-2, SI File 1100626.201. | ||
BWR Core Shroud Inspection and Flaw Evaluation Guidelines (BWRVIP-76), | : 5. Not used.6. Not used.7. GEH Report, "Task T0304: Reactor Internal Pressure Differences, Fuel Life Margin, CRGT lift Force, Acoustic and Flow Induced Loads," GE-Hitachi-Nuclear Energy Report GE-NE 0000-0060-9039-TR-R1, DRF 0000-0060-9027, Revision 1, Class III, November 2008.8. ASME Boiler and Pressure Vessel Code, Section II, Part D, 1998 Edition with no Addenda.9. ASME Boiler and Pressure Vessel Code, Section XI, 1995 Edition with Addenda through 1996.10. Not used.11. NIST Chemistry WebBook, http://webbook.nist.gov/chemistry/fluid/. | ||
EPRI, Palo Alto, CA, BWRVIP 1999, TR-1 14232.3. Chicago Bridge & Iron Co. Drawing 35 Rev 5, "Plan of Shroud Support 17'2" ID, 63'-2" | : 12. Monticello Drawing No. NX7831-197-1 Revision D, "Monticello Nuclear Generating Plant Reactor Vessel & Internals," SI File No. 1100626.201. | ||
No. NX-9310-28, SI File 1100626.201. | File No.: 1100626.301 Page 10 of 15 Revision: | ||
: 4. General Electric Drawing 886D487, "Reactor Vessel," | 0 F0306-OIRI Non-Proprietary. | ||
No. NX7831-7-2, SI File 1100626.201. | Vendor Proprietary Information has been Redacted.VjSftnPWb l Itegfy* AWOMSoi ftsIc 13. MonticelloDrawing No. NX7831-7-7 (GE Drawing No. 886D482, Revision 10), "Reactor Vessel," SI File No. 1100626.201. | ||
: 5. Not used.6. Not used.7. GEH Report, "Task T0304: Reactor Internal Pressure Differences, Fuel Life Margin, CRGT | : 14. Not used.15. Xcel Energy DIT No. EC 18095, "Shroud Support Plate Uplift Evaluation," Rev.1, SI File 1100626.206. | ||
: 16. Not used.17. BWR Vessel and Internals Project: Evaluation of Crack Growth in BWR Stainless Steel RPV Internals (BWRVIP-14A), EPRI, Palo Alto, CA, BWRVIP, 2003, TR-105873. | |||
: 12. Monticello Drawing No. NX7831-197-1 Revision D, "Monticello Nuclear Generating | : 18. Not used 19. ASME, Boiler and Pressure Vessel Code, Section III, 1965 Edition with Addenda to and including Summer 1966 Addenda.20. SI Calculation, "Evaluation of the Monticello Shroud with Indications at Welds H8 and H9," SI File 1100560.301, Rev. 0.File No.: 1100626.301 Revision: | ||
SI File No. 1100626.201. | 0 Page 11 of 15 F0306-OIR1 Non-Proprietary. | ||
File No.: 1100626.301 Page 10 of | Vendor Proprietary Information has been Redacted.jS"1"c Wl egi AssocAtes, Wc?Table 1: Load Summary (a) Loads Supported by Internal Shroud Support [13]Component Weight (kips)Internal Structure | ||
& Periphery Fuel 189 Guide loads (all fuel, drives, control rods, guide tubes) 397 for horizontal earthquake loads only Jet Pumps 10 (b) Water Loads [13]Operating Conditions Water Weight (kips)Normal Full Power 353.1 Hot, Stand By 381.4 Cold Vessel, Full 729.2 Refueling (water level 927") 1080 Refueling (water level 655") 651 Table 2: Design Input for Shroud Support Plate Pressure Difference Calculation Design Variable Value Units Reference Normal water level elevation, above vessel 512.5 in. 12 zero Recirculation Nozzle centerline elevation, 150 in. 12 above vessel zero Top of the shroud support plate elevation, 98.75 in. 13 above vessel zero (1)Annulus Temperature 530.2 OF I Annulus Saturation Pressure 886.25 psia 11 Dome Pressure 1025 psia I Note : (1) Calculation based on 108.5" -11.75"+2" from Reference 13.Table 3: Material Properties at 550 'F Alloy 600 Base Metal Yield Strength (ksi) 30.1 Ultimate Strength (ksi) 80 Stress Intensity Sm (ksi) 23.3 File No.: 1100626.301 Revision: | |||
Vendor Proprietary Information has been Redacted. | 0 Page 12 of 15 F0306-O1RI Non-Proprietary. | ||
VjSftnPWb l Itegfy* AWOMSoi | Vendor Proprietary Information has been Redacted.T a bdl e 4 :A P rssuo c ra e i for Table 4: Pressure Differential across the Shroud Support Plate Level Pressure Differential (psid)A/B 29.03 [7]C/D 179.08 Table 5: Uplift Load on Shroud Support Plate Level Area (in 2) Pressure Differential (psid) Up Force (Ibs)A/B 12399.15 29.3 363295 C/D 12399.15 179.08 2220440 Table 6: Vertical Seismic Load Level Coefficient Total Wt (kips) Up Force (kips)A/B 0.06 1279 76.74 C/D 0.12 1279 153.48 Table 7: Total Upward Shear Force Pressure Vertical Seismic Total Level Differential Load (kips) (kips)_________ | ||
SI File No. 1100626.201. | kips Load___(kips)__ (kips)_____(kips)A/B 363.295 76.74 440.04 C/D 2220.44 153.48 2373.92 File No.: 1100626.301 Revision: | ||
: 14. Not used.15. Xcel Energy DIT No. EC 18095, "Shroud Support Plate Uplift Evaluation," | 0 Page 13 of 15 F0306-O1RI Non-Proprietary. | ||
Rev.1, SI | Vendor Proprietary Information has been Redacted.VskkID&W h*y AWOCW~SS, W~Table 8: Limit Load Evaluation Results for Compound Crack Profile Level A/B Level C/D (1) EoEP uncracked length (in) 113.08 113.08 (2) Support plate thickness (in) 2.5 2.5 (3) Remaining ligament (in) 0.833 0.833 (4) Available shear area (in') (=(1)*(3)) | ||
: 16. Not used.17. BWR Vessel and Internals Project: | 94.20 94.20 (5) Total applied shear load (kips) 440.04 2373.92 (6) Applied shear in each weld (kips) (=(5)/2) 220.02 1186.96 (7) Tensile Flow Stress (ksi) 69.9 69.9 (8) Shear Flow Stress (ksi) 34.95 34.95 (9) Shear limited load (kips) (=(8)*(4)) | ||
Evaluation of Crack Growth in BWR Stainless Steel | 3292.29 3292.29 (10) Safety Factor (=(9)/(6) 14.96 2.77 (11) Required Safety Factor 2.77 1.39 Table 9: Limit Load Evaluation Results for Surface Crack Profile Level A/B Level C/D (1) EoEP uncracked length (in) 580.02 580.02 (2) Support plate thickness (in) 2.5 2.5 (3) Remaining ligament (in) 0.625 0.625 (4) Available shear area (in 2) (=(1)*(3)) | ||
EPRI, Palo Alto, CA, BWRVIP, 2003, TR-105873. | 362.51 362.51 (5) Total applied shear load (kips) 440.04 2373.92 (6) Applied shear in each weld (kips) (=(5)/2) 220.02 1186.96 (7) Tensile Flow Stress (ksi) 69.9 69.9 (8) Shear Flow Stress (ksi) 34.95 34.95 (9) Shear limited load (kips) (=(8)*(4)) | ||
: 18. Not | 12669.7 12669.7 (10) Safety Factor (=(9)/(6) 57.58 10.67 (11) Required Safety Factor 2.77 1.39 File No.: 1100626.301 Revision: | ||
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Vendor Proprietary Information has been Redacted. | Vendor Proprietary Information has been Redacted.nrW"uWu h*Oy A Css , I ,'~I50~ ~' 'D'~1~i srp~Ii~,,r | ||
jS"1"c Wl egi AssocAtes, Wc?Table 1: Load Summary(a) Loads Supported by Internal Shroud Support [13]Component Weight (kips)Internal Structure | * 4 I~f!.~: ~Y'1 ""~U tins c~ Ii. I Figure 1. Jet Pumps Inspection Illustration File No.: 1100626.301 Revision: | ||
& Periphery Fuel | 0 Page 15 of 15 F0306-OIRI}} | ||
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T a bdl e 4 :A P rssuo c ra e i | |||
kips Load___(kips)__ | |||
(kips)_____ | |||
(kips)A/B 363.295 76.74 440. | |||
Vendor Proprietary Information has been Redacted. | |||
VskkID&W h*y AWOCW~SS, W~Table 8: Limit Load Evaluation Results for Compound Crack | |||
94.20 94.20(5) Total applied shear load (kips) 440.04 2373.92(6) Applied shear in each weld (kips) (=(5)/2) 220.02 1186.96(7) Tensile Flow Stress (ksi) 69.9 69.9(8) Shear Flow Stress (ksi) 34.95 34.95(9) Shear limited load (kips) (=(8)*(4)) | |||
3292.29 3292.29(10) Safety Factor (=(9)/(6) 14.96 2.77(11) Required Safety Factor 2.77 1. | |||
362.51 362.51(5) Total applied shear load (kips) 440.04 2373.92(6) Applied shear in each weld (kips) (=(5)/2) 220.02 1186.96(7) Tensile Flow Stress (ksi) 69.9 69.9(8) Shear Flow Stress (ksi) 34.95 34.95(9) Shear limited load (kips) (=(8)*(4)) | |||
12669.7 12669.7(10) Safety Factor (=(9)/(6) 57.58 10.67(11) Required Safety Factor 2.77 1. | |||
Vendor Proprietary Information has been Redacted. | |||
nrW"uWu h*Oy A Css ,I,'~I50~ ~' 'D'~1~i srp~Ii~,,r | |||
* | |||
Revision as of 03:25, 14 July 2018
ML13191A039 | |
Person / Time | |
---|---|
Site: | Monticello |
Issue date: | 05/02/2011 |
From: | Sowah S, Tang S S Structural Integrity Associates |
To: | Office of Nuclear Reactor Regulation |
References | |
L-MT-13-040 | |
Download: ML13191A039 (16) | |
Text
ENCLOSURE 4 MONTICELLO NUCLEAR GENERATING PLANT SUPPLEMENTAL INFORMATION REGARDING CYCLE 25 INSERVICE INSPECTION
SUMMARY
REPORT -CORE SHROUD SUPPORT FLAW EVALUATION EC-1 8095 EVALUATION OF THE MONTICELLO SHROUD SUPPORT PLATE UPLIFT LOAD WITH INDICATIONS IN THE H8 AND H9 WELDS (NON-PROPRIETARY VERSION)(15 pages follow)
Non-Proprietary.
Vendor Proprietary Information has been Redacted.~ Structural Integrity Associates, Incy File No.: 1100626.301 tr Project No.: 1100626 CALCULATION PACKAGE Quality Program: E Nuclear El Commercial PROJECT NAME: Evaluation of the Monticello Shroud Support Plate Uplift Load with Indications in the H8 and H9 Welds CONTRACT NO.: 00001005 Release 27, Amendment 001 CLIENT: PLANT: XCEL Energy Monticello Nuclear Generating Plant CALCULATION TITLE: Evaluation of Shear Capacity of Monticello Shroud Welds H8 and H9 Document Affected Project Manager Preparer(s)
&D on afe Revision Description Approval Checker(s)
Revision Pages Signature
& Date Signatures
& Date A 1 -15 Draft for Client Review Marcos. L. Herrera Preparer: MLH 4/29/11 S. S. Tang/Sandra Sowah 4/29/11 Reviewer: Hal Gustin/Jay Gillis 4/29/11 01 -15 Initial Issue Preparer: Marcos. L. Herrera S. S. Tang MLH 5/2/11 SST 5/2/11 Sandra Sowah SS 5/2/11 Reviewer: Hal Gustin 5/2/11 Jay Gillis 5/2/11 Gn.taInI Vender Proprietary I r nttil Page 1 of 15 F0306-01RI Non-Proprietary.
Vendor Proprietary Information has been Redacted.CshwC"iuhitegd*
AW00Ociates b Table of Contents
1.0 INTRODUCTION
.....................................................................................................
4 2.0 TECHNICAL APPROACH .....................................................................................
4 3.0 ASSUMPTIONS
....................................................................................................
5 4.0 DESIGN INPUTS .....................................................................................................
6 5.0 CALCULATIONS
...................................................................................................
6 5.1 Pressure Difference across Shroud Support Plate ........................................
6 5.1.1 Top of Shroud Support Plate Pressure Calculation
....................................
6 5.1.2 Shroud Support Plate Pressure Difference Calculation
................................
7 5.2 Postulated Crack Profile ..............................................................................
7 5.3 Limit Load for Shear .....................................................................................
8 5.3.1 App lied Loads ..............................................................................................
8 5.4 C rack G row th ................................................................................................
9 5.4.1 Crack growth in circumferential direction
..................................................
9 5.5 Evaluation C ases ..........................................................................................
9 6.0 RESULTS OF ANALYSIS ........ ; ............................................................................
10
7.0 CONCLUSION
S AND DISCUSSIONS
.................................................................
10 8.0 R EFER EN C ES ......................................................................................................
10 This doeumzrnt eontains ven~der proprita~ry a nfermaition.
Proprietaryifraini lindiented by a bar in the right hand margin.File No.: 1100626.301 Page 2 of 15 Revision:
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Non-Proprietary.
Vendor Proprietary Information has been Redacted.Cjsirucmuu h#C orY Asockites, Inc List of Tables Table 1: Load Sum m ary ....................................................................................................
12 Table 2: Design Input for Shroud Support Plate Pressure Difference Calculation
.............
12 Table 3: M aterial Properties at 550 0 F ...............................................................................
12 Table 4: Pressure Differential across the Shroud Support Plate .........................................
13 Table 5: Uplift Load on Shroud Support Plate .................................................................
13 Table 6: V ertical Seism ic Load .........................................................................................
13 Table 7: Total Upward Shear Force ...................................................................................
13 Table 8: Limit Load Evaluation Results for Compound Crack Profile ..............................
14 Table 9: Limit Load Evaluation Results for Surface Crack Profile ...................................
14 List of Figures Figure 1. Jet Pumps Inspection Illustration
.......................................................................
15 File No.: 1100626.301 Revision:
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f.
1.0 INTRODUCTION
During the Spring 2011 outage, inspection of the Monticello shroud support plate weld H8 and weld H9 was performed.
Visual inspection (EVT1) coverage was obtained from jet pump JP20 to JPI and JP10 to JP 11, as identified in Figure 1 [1]. This accounts for approximately 17% of the H8 and H9 circumference
[1]. An additional 64 inches of inspection coverage was acquired with visual inspection VT-3 on the top side of the weld [1] in the area between all the jet jumps. The visual inspection revealed cracking in the shroud support legs but no indications were identified in the welds H8 and H9.This evaluation is performed to quantify the structural margin retaining the shroud support plate H8 and H9 welds after one cycle of additional operation assuming plastic collapse in shear to be the applicable failure mode because the most significant loading is the uplift load due to the vertical seismic and the pressure difference across the shroud support plate.2.0 TECHNICAL APPROACH The technical approach used for this evaluation is based on the BWRVIP-76
[2], limit load approach.The limit load analysis for shear failure is developed based on the approach for determining the limit load for an axial crack in the shroud as presented in [2] and summarized below. Consistent with the BWRVIP methodology in [2], the failure mode of the Alloy 600 and corresponding weld materials is considered to be the net section (plastic) collapse, because of the very high ductility of these materials at reactor operating temperatures.
Also, the fluence in this region is not high enough to impact the material ductility.
The limit load for an axial crack assuming tensile failure of the remaining ligament is expressed in Section E. 1.2 of [2] as: By similar approach, the shear failure limit load for a crack in a circular weld can be expressed as: (SF)S = oj Lt (2)where: S ý shear force due to uplift load SF = safety factor File No.: 1100626.301 C ontains Vener Proprietary-inf-r..atin Page 4 of 15 Revision:
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Vendor Proprietary Information has been Redacted.vIkfegdly#
AWssOcjS, WOc asf = shear flow stress L = length of uncracked circumference in circular welds (H8/H9)t = thickness of shroud support plate.Using the maximum shear theory or Tresca criteria, the maximum shear stress at yield is half the maximum yield strength.
The shear flow stress can be expressed as: vsf = Gf/2 There are no plant specific safety factors for the Monticello shroud [1]. Per Section D.5 in Reference 2, required minimum safety factors of 2.77 for normal/upset (Level A/B) conditions and 1.39 for emergency/faulted (Level C/D) conditions are used in this evaluation.
In limit load evaluation, elastic-perfectly plastic material properties are used.3.0 ASSUMPTIONS The following assumptions are used: a. Loading in weld H8 and weld H9 is assumed to be pure shear due to the most significant loads being the vertical seismic and the pressure difference across the shroud support plate.b. Material properties of Alloy 600 compatible weld metal are assumed to be the same as the Alloy 600 base metal.c. The shear load is assumed to be evenly distribution between the weld H8 and weld H9.d. The shear load is assumed to be evenly distributed in the remaining ligament of each weld.e. For uninspected region, through-wall cracking is assumed. This is conservative since no credit is taken for the uninspected region.f. For inspected region, surface cracking with depth of 75% of the plate thickness is assumed.This assumption is based on the general evidence provided by the BWR fleet shroud cracking data. The flaws generally arrest at 2/3 of the wall thickness, so the assumption of a 75% wall flaw is conservative.
- h. The vertical flexural shear from the moment induced by the horizontal acceleration due to the jet pump weight on the support plate is assumed to be negligible.
It was estimated that this upward flexural shear is less than 5% of the total uplift shear load.i. The material is considered to behave in an elastic-plastic manner, which is consistent with BWRVIP methodology for reactor internals in low fluence regions.j. Crack growth in the depth direction is not considered since the assumed crack depth is based on flaw depths observed from BWR fleet operating experience.
Subsequent growth is minimal due to excellent Monticello water chemistry conditions in the lower plenum.k. Seismic and LOCA are conservatively combined in order to provide added margin to the evaluation and further justify the maximum flaw depth based on BWR fleet operating experience.
File No.: 1100626.301 Page 5 of 15 Revision:
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Vendor Proprietary Information has been Redacted.V _W9W k*#ww.Ihegl AWOSSoca, Wnc 4.0 DESIGN INPUTS The following dimensions are used in the evaluation:
Reactor vessel inside diameter (ID): 17.167 ft [1]Shroud plate thickness:
2.5 inches [3]Shroud ID: 159.75 inches [4]Shroud thickness:
1.75 inches [4]Design AP across shroud support plate for Levels A through D 100 psi [1]Per Reference 1, the vertical earthquake acceleration is 0.06g.The vessel internal component loads and water loads are obtained from Reference 13 and summarized in Table 1.The input used to calculate the pressure differential across the shroud support plate for different operating conditions are obtained from Reference 7 and summarized in Table 2. The maximum AP for Level A/B is 29.03 psid for the EPU conditions
[7]. For Level C/D, the maximum AP is 47 psid from the 113% OLTP. Since it is not clear if the Level C/D reactor internal pressure difference (RIPD)considers the decompression of the annulus region following a postulated recirculation line break (RLB) event (typically the Level C/D RIPD is given as the main steam line break pressure difference), a bounding methodology is used in this calculation to calculate an uplift load on the shroud support plate.Per Reference 1, the Code of Construction isSection III, 1965 with Summer 1966 Addenda [19]. The allowable stress intensity (Sn) is 23.3 ksi [1]. The material yield strength (Sy), ultimate strength (Sj)and allowable stress intensity for Alloy 600 are obtained from Reference 8 at 550 'F for conservatism and summarized in Table 3. As compared to the allowable Sm from Reference 19 stated in Reference 1, the Sm from different Code Editions remains the same.The input used to calculate the pressure differential across the support plate is summarized in Table 4.The shroud support plate material is Alloy 600 [15].The end of evaluation period (EoEP) is 24 months [1].5.0 CALCULATIONS 5.1 Pressure Difference across Shroud Support Plate 5.1.1 Top of Shroud Support Plate Pressure Calculation The pressure at the top of the shroud support plate for normal condition, Psihoud, is a required input for determination of the pressure difference across the shroud support plate for the postulated Recirculation Outlet Break case. Considering hydrostatic pressure, this may be calculated by: File No.: 1100626.301 Page 6 of 15 Revision:
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Vendor Proprietary Information has been Redacted.v sh n I h*t g A. aSciate, c.°fhrOud= Po h (3)1728. vf where PO = pressure at the water surface, psia h = water height from top of shroud support plate elevation to the water surface, in vf = specific volume of the water at the top of the shroud support plate, ft 3/lb =0.021 19ft 3/lb (based on annulus temperature, interpolated from [11]).Thus, Pshroud = 1025 + (512.5 -99.25)/(1728 x 0.02119)=
1036.3 psia.The pressure in the lower head is higher than the pressure in the annulus because of the pressure added by the jet pumps. The pressure difference can be estimated from Reference 7 as the maximum differential pressure across the shroud support plate for the Level B condition, which is 29.03 psid.5.1.2 Shroud Support Plate Pressure Difference Calculation A conservative lower bound for the pressure above the support plate is the saturation pressure at the annulus temperature.
A low pressure above the support plate is conservative because it maximizes lifting force on the plate due to the pressure differential across the plate. If the pressure below the plate is held constant and the pressure above the support plate is lessened, the upward force on the support plate is increased.
In normal operation, the lowest pressure in the reactor pressure vessel is the pressure in the steam dome. The saturation pressure at the annulus temperature is slightly less than the steam dome pressure because the annulus liquid is slightly subcooled.
From Reference 7, the maximum Level A/B pressure difference across the shroud support plate is given as 29.03 psid. This pressure differential is expected to exist at the instant of the postulated RLB event.A conservative lower bound for the pressure above the support plate, following the RLB event, is the saturation pressure at the annulus temperature.
Thus the bounding total pressure difference, AP, for the Level C/D conditions is given as: AP=Pshoud
-Psat = (1036.3 + 29.03) -886.25 = 179.08 psid This pressure difference acts to lift the support plate upward.The pressure differentials across the shroud support plate are summarized in Table 4.5.2 Postulated Crack Profile From Reference 1, Welds H8 and H9 were inspected with EVT-1 from JP 20 to JP1 and JP10 to JP 11 (about 17% of the circumference), as shown in Figure 1 [4], with an additional 64 inches inspected File No.: 1100626.301 Page 7 of 15 Revision:
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Vendor Proprietary Information has been Redacted.VII~S&NOiauN Inftogi AssociatS, Inc with VT-3. The regions not inspected by VT-3 are the portion of the welds close to the jet pumps, as illustrated in Figure 1 [1].Thus, the uninspected regions are considered to be evenly distributed based on the jet pumps pattern, resulting in 10 uninspected regions as illustrated in Figure 1. These regions are conservatively to be cracked through-wall.
Length of weld H8 = 21rtRi=2*1rt(159.75/2+1.75)=
2*iT(81.625) 512.865 in Length of weld H9 = 2rTRo=2*Tr(17.167*
12/2)= 2*rT(103.002)
= 647.18 in To simplify, an average length for welds H8 and H9 is used for evaluation.
Average weld length for welds H8 and H9 = (512.865+647.18)/2
=580.02 inch The inspection length inspected by VT-3 for each weld is approximately 64/2 = 32 inches.Using the average weld length, the following are obtained for each weld: Total inspected length = 0.17*580.02+32
= 130.60 inches Total uninspected length = 580.02 -130.63 inches = 449.42 inches This corresponds to 449.42/10=44.94 inches for each uninspected region.5.3 Limit Load for Shear 5.3.1 Applied Loads 5.3.1.1 Uplift Load The uplift load is due to the pressure difference across the shroud support plate. The AP uplift area (UA) is calculated as: UA = 1"(Ro 2-Ri 2)=Tr(l103.002 2-81.625 2) = 12399.15 in2 The uplift loads due to the pressure difference for Level A/B and C/D are calculated and shown in Table 5.5.3.1.2 Vertical Seismic Load In Table 1, it is shown that the total weight of the jet pumps is 10 kips.. Also, the maximum water weight of 1080 kips from Table 1(b) is selected.
Thus the total weight due to internal structure
&periphery fuel, jet pumps and water weight is: Wt = 189 + 10 + 1080 =1279 kips File No.: 1100626.301 Page 8 of 15 Revision:
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Vendor Proprietary Information has been Redacted.hxtegdl ~Y AociatS, Inc.The vertical seismic acceleration is 0.06g. This is assumed to be for OBE.The total vertical seismic load for OBE and SSE is summarized in Table 6.The total upward shear force is summarized in Table 7.5.4 Crack Growth Crack growth in the depth direction is not included since the depth used in the evaluation is consistent with the depths based on BWR fleet operating experience.
In addition, due to Monticello's excellent water chemistry in the lower plenumn, subsequent crack growth will not be significant.
5.4.1 Crack growth in circumferential direction Per Reference 2, the crack growth rate is 5x1 0-5 in/hr. This is used for conservatism regardless of plant specific water chemistry.
For 10 uninspected regions, with 2 crack fronts for each region since a through-wall crack is used, the total crack growth Al for 24 months is: AI= 1O*2*5xl0 5*2*365*24
= 17.52 inches Therefore, the remaining length of un-cracked circumference at the EoEP is L =130.60 -17.52 = 113.08 inches 5.5 Evaluation Cases Two crack profiles are used to evaluate the structural margin retaining the shroud support plate weld H8 and weld H9. Each of these contains significant conservatisms, which compensate for any uncertainty in the flaw depths. It is important to note that BWR shroud cracking history, of which there is a significant amount, has shown that typically cracks in shroud welds grow to approximately two-thirds of the shroud wall and then appear to become essentially inactive.
This is particularly expected for Monticello's case because of the excellent water chemistry experienced in the vicinity of the indications on the lower side of H8 and H9. These two crack profiles are: (a) Multiple Cracks: A through-wall crack is postulated in the uninspected regions and a remaining ligament of 1/3 of the plate thickness in the inspected region is postulated since inspection was performed on the top side only. The 1/3 wall remaining ligament is based on field experience for BWR shroud welds.(b) Full Circumferential Surface Crack: A surface crack at the bottom plate surface extending along the circumferential length of Weld H8 and H9 with a crack depth at 75% of the support plate thickness is postulated.
This corresponds to a remaining ligament of 0.625 inches in the support plate.File No.: 1100626.301 Page 9 of 15 Revision:
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Vendor Proprietary Information has been Redacted.Vjj~hVucuhfIW latoil AWOMOctS, Wnc 6.0 RESULTS OF ANALYSIS The limiting shear force due to limit load failure criteria can be calculated using Eq. (2). The flow stress is taken as 3 Sm per Reference 9 as used in Reference 20.The analysis results are summarized in Tables 8 and 9 for the two crack profiles described in Section 5.5. It is shown that the safety factors are 14.96 and 2.77 for Levels A/B and C/D, respectively for the multiple crack case. For the surface crack case, the safety factors are 57.58 and 10.67 for Levels A/B and CD, respectively.
These are higher than the required safety factors of 2.77 and 1.39 per Reference 2.
7.0 CONCLUSION
S AND DISCUSSIONS An analysis was performed to evaluate the capacity of the remaining length in the Welds H8 and H9 to prevent the up lift of the core shroud. It is shown that, for an EoEP of 24 months, the calculated safety factors of for Levels A/B and C/D conditions in Weld H8 and H9 are significantly above the required safety factors of 2.77 and 1.39, respectively, for both conservative flaw configurations analyzed.These results demonstrate that, even with the postulated flaws in welds H8 and H9, the structural integrity of the shroud support plate is assured.
8.0 REFERENCES
- 1. Xcel Energy Design Information Transmittal (DIT), "Shroud Support Plate Uplift Analysis," Tracking Number EC, Date 5/2/2011, DIT No. 3, S1 File 1100626.207.
- 2. BWR Vessel and Internals Project: BWR Core Shroud Inspection and Flaw Evaluation Guidelines (BWRVIP-76), EPRI, Palo Alto, CA, BWRVIP 1999, TR-1 14232.3. Chicago Bridge & Iron Co. Drawing 35 Rev 5, "Plan of Shroud Support 17'2" ID, 63'-2" INS Heads Nuclear Reactor," No. NX-9310-28, SI File 1100626.201.
- 4. General Electric Drawing 886D487, "Reactor Vessel," No. NX7831-7-2, SI File 1100626.201.
- 5. Not used.6. Not used.7. GEH Report, "Task T0304: Reactor Internal Pressure Differences, Fuel Life Margin, CRGT lift Force, Acoustic and Flow Induced Loads," GE-Hitachi-Nuclear Energy Report GE-NE 0000-0060-9039-TR-R1, DRF 0000-0060-9027, Revision 1, Class III, November 2008.8. ASME Boiler and Pressure Vessel Code,Section II, Part D, 1998 Edition with no Addenda.9. ASME Boiler and Pressure Vessel Code,Section XI, 1995 Edition with Addenda through 1996.10. Not used.11. NIST Chemistry WebBook, http://webbook.nist.gov/chemistry/fluid/.
- 12. Monticello Drawing No. NX7831-197-1 Revision D, "Monticello Nuclear Generating Plant Reactor Vessel & Internals," SI File No. 1100626.201.
File No.: 1100626.301 Page 10 of 15 Revision:
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Vendor Proprietary Information has been Redacted.VjSftnPWb l Itegfy* AWOMSoi ftsIc 13. MonticelloDrawing No. NX7831-7-7 (GE Drawing No. 886D482, Revision 10), "Reactor Vessel," SI File No. 1100626.201.
- 14. Not used.15. Xcel Energy DIT No. EC 18095, "Shroud Support Plate Uplift Evaluation," Rev.1, SI File 1100626.206.
- 16. Not used.17. BWR Vessel and Internals Project: Evaluation of Crack Growth in BWR Stainless Steel RPV Internals (BWRVIP-14A), EPRI, Palo Alto, CA, BWRVIP, 2003, TR-105873.
- 18. Not used 19. ASME, Boiler and Pressure Vessel Code,Section III, 1965 Edition with Addenda to and including Summer 1966 Addenda.20. SI Calculation, "Evaluation of the Monticello Shroud with Indications at Welds H8 and H9," SI File 1100560.301, Rev. 0.File No.: 1100626.301 Revision:
0 Page 11 of 15 F0306-OIR1 Non-Proprietary.
Vendor Proprietary Information has been Redacted.jS"1"c Wl egi AssocAtes, Wc?Table 1: Load Summary (a) Loads Supported by Internal Shroud Support [13]Component Weight (kips)Internal Structure
& Periphery Fuel 189 Guide loads (all fuel, drives, control rods, guide tubes) 397 for horizontal earthquake loads only Jet Pumps 10 (b) Water Loads [13]Operating Conditions Water Weight (kips)Normal Full Power 353.1 Hot, Stand By 381.4 Cold Vessel, Full 729.2 Refueling (water level 927") 1080 Refueling (water level 655") 651 Table 2: Design Input for Shroud Support Plate Pressure Difference Calculation Design Variable Value Units Reference Normal water level elevation, above vessel 512.5 in. 12 zero Recirculation Nozzle centerline elevation, 150 in. 12 above vessel zero Top of the shroud support plate elevation, 98.75 in. 13 above vessel zero (1)Annulus Temperature 530.2 OF I Annulus Saturation Pressure 886.25 psia 11 Dome Pressure 1025 psia I Note : (1) Calculation based on 108.5" -11.75"+2" from Reference 13.Table 3: Material Properties at 550 'F Alloy 600 Base Metal Yield Strength (ksi) 30.1 Ultimate Strength (ksi) 80 Stress Intensity Sm (ksi) 23.3 File No.: 1100626.301 Revision:
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Vendor Proprietary Information has been Redacted.T a bdl e 4 :A P rssuo c ra e i for Table 4: Pressure Differential across the Shroud Support Plate Level Pressure Differential (psid)A/B 29.03 [7]C/D 179.08 Table 5: Uplift Load on Shroud Support Plate Level Area (in 2) Pressure Differential (psid) Up Force (Ibs)A/B 12399.15 29.3 363295 C/D 12399.15 179.08 2220440 Table 6: Vertical Seismic Load Level Coefficient Total Wt (kips) Up Force (kips)A/B 0.06 1279 76.74 C/D 0.12 1279 153.48 Table 7: Total Upward Shear Force Pressure Vertical Seismic Total Level Differential Load (kips) (kips)_________
kips Load___(kips)__ (kips)_____(kips)A/B 363.295 76.74 440.04 C/D 2220.44 153.48 2373.92 File No.: 1100626.301 Revision:
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Vendor Proprietary Information has been Redacted.VskkID&W h*y AWOCW~SS, W~Table 8: Limit Load Evaluation Results for Compound Crack Profile Level A/B Level C/D (1) EoEP uncracked length (in) 113.08 113.08 (2) Support plate thickness (in) 2.5 2.5 (3) Remaining ligament (in) 0.833 0.833 (4) Available shear area (in') (=(1)*(3))
94.20 94.20 (5) Total applied shear load (kips) 440.04 2373.92 (6) Applied shear in each weld (kips) (=(5)/2) 220.02 1186.96 (7) Tensile Flow Stress (ksi) 69.9 69.9 (8) Shear Flow Stress (ksi) 34.95 34.95 (9) Shear limited load (kips) (=(8)*(4))
3292.29 3292.29 (10) Safety Factor (=(9)/(6) 14.96 2.77 (11) Required Safety Factor 2.77 1.39 Table 9: Limit Load Evaluation Results for Surface Crack Profile Level A/B Level C/D (1) EoEP uncracked length (in) 580.02 580.02 (2) Support plate thickness (in) 2.5 2.5 (3) Remaining ligament (in) 0.625 0.625 (4) Available shear area (in 2) (=(1)*(3))
362.51 362.51 (5) Total applied shear load (kips) 440.04 2373.92 (6) Applied shear in each weld (kips) (=(5)/2) 220.02 1186.96 (7) Tensile Flow Stress (ksi) 69.9 69.9 (8) Shear Flow Stress (ksi) 34.95 34.95 (9) Shear limited load (kips) (=(8)*(4))
12669.7 12669.7 (10) Safety Factor (=(9)/(6) 57.58 10.67 (11) Required Safety Factor 2.77 1.39 File No.: 1100626.301 Revision:
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Vendor Proprietary Information has been Redacted.nrW"uWu h*Oy A Css , I ,'~I50~ ~' 'D'~1~i srp~Ii~,,r
- 4 I~f!.~: ~Y'1 ""~U tins c~ Ii. I Figure 1. Jet Pumps Inspection Illustration File No.: 1100626.301 Revision:
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