ML041040803

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Calculation MNS-02Q-301, Determination of Allowable Flaw Size and Leakgae
ML041040803
Person / Time
Site: Mcguire
Issue date: 03/18/2004
From: Weitze W
Structural Integrity Associates
To:
Office of Nuclear Reactor Regulation
References
MNS-02Q-301
Download: ML041040803 (10)
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Text

ATTACHMENT 2 Evaluation of Leaking McGuire 2 Containment Spray Piping

FILE No.: MNS-02Q-301

  • q STRUCTURAL CALCULATION INTEGRITY PACKAGE PROJECT No.: MNS-02Q Associates PROJECT NAME: Evaluation of Leaking McGuire 2 Containment Spray Piping CLIENT: Duke Energy Corporation CALCULATION TITLE: Determination of Allowable Flaw Size and Leakage Project Mgr.

Preparer(s) &

Document Affected Revision Description Approval Checker(s)

Revision Pages Signature &

Signatures &

Date Date 0

1 -9 Original Issue WF Weitze WF Weitze Computer

  • fC, Y6&C7 Files F3/1 81/64 3/18/04 AF Deardorff 3/18/04

Table of Contents 1.0 2.0 3.0 4.0 4.1 4.2 5.0 6.0 OBJECTIVE.....................

3 METHODOLOGY......................

3 INPUT AND ASSUMPTIONS.....................

4 ANALYSIS......................

4 Allowable Flaw Size......................

4 Leakage.....................

5 DISCUSSION.....................

8 REFERENCES......................

9 List of Tables Table 1. AllowableFlawSize.

5 Table 2. Leakage Rate versus Crack Length (2c) and Sustained Bending Stress (Pb).............................

7 List of Figures Figure 1. Leakage Rate versus Crack Length (2c) and Sustained Bending Stress (Pb)............................

8 Revision 0

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1.0 OBJECTIVE Develop allowable flaw size (including appropriate safety factor) as a function of applied stress for the McGuire Nuclear Station (MNS) Containment Spray Piping System (NS). Calculate leakage rates based on the allowable flaw sizes.

2.0 METHODOLOGY Using the limit load methodology described in Appendix C of ASME Section XI [1], C-3320, failure bending stress is calculated as follows:

Pb' = Z*SF (Pm + Pb + P,/SF) - Pm Pb' = SF (Pm + Pb) - Pm (For flux welds)

(For non-flux welds)

Where Z Pb' Pm Pb Pe SF

= weld type factor

= failure bending stress, psi

= primary membrane stress, psi

= primary bending stress, psi

= expansion bending stress, psi

= safety factor (2.77 for normal/upset; 1.39 for emergency/faulted (1])

Allowable flaw lengths at each weld location are determined using the methodology outlined in Appendix C of Section XI of the ASME Code [1]. For given values of Pm and half-flaw angle 0, then the angle D to the neutral axis is calculated as:

1/2= % [n - (a/t)0 - ntPd/(3Sm)], where a = flaw depth, inches t = pipe wall thickness, inches Sm = Design stress intensity, psi Based on 0 and f3, a value of failure bending stress is calculated:

Pb' = (6Sdn) [2 sin 1 - (a/t) sin 0]

.a The value of 0 is varied until Pb' based on 0 and Pm equals Pb' based on the applied stresses. For longer flaws for which 0 + 1 > 7t, a somewhat different set of equations is used to calculate 13 and Pb' based on 0, but this condition does not occur when the flaws are through-wall (alt'-= 1).

The leakage calculations are performed with the EPRI computer program PICEP [2].

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3.0 INPUT AND ASSUMPTIONS Duke has provided the following input [3]:

  • McGuire Nuclear Station, Unit 2
  • Pipe Specification MCS-1206.00-02-0002
  • Design Pressure: 170 psig
  • Design Temperature: 190'F
  • Pipe Size: 8"
  • Schedule: 10
  • Pipe Material: SA-312 TP304
  • Elbow Material: SA-403 WP304
  • Range of crack sizes to be evaluated: 0.2" - 4" The following assumptions are made:
  • Flaws assumed to be through-wall
  • Smooth fatigue-type crack assumed to maximize leakage For operability analysis, the factor of safety is chosen for Service Level C and D conditions as 1.39 from Section XI. To allow evaluation of a range of conditions, parametric evaluations are provided for the allowable flaw size and leakage.

4.0 ANALYSIS 4.1 Allowable Flaw Size Excel workbook MNS02301.XLS, included in the project computer files, calculates failure bending stress and allowable flaw length based on the stress and moment values. All welds use the gas tungsten arc weld (GTAW) method, which is non-flux [3]; therefore, the non-flux equation for Pb' based on stress is used, and P, and Z are not used. For 8" schedule 10 piping, the outside diameter is D. = 8.625" and the thickness is t = 0.148". Axial stress is Pm = PD/4t = 170*8.625/(4*0.148) =

2,477 psi. For both materials Sm is 20,000 psi at 190'F [4]. Since flaws are assumed through-wall, a/t

= 1.0.

Table 1 shows allowable flaw size in radians and degrees for each value of bending stress chosen.

Flaw half length c is calculated based on the flaw half angle and the pipe outside diameter. For Revision 0

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evaluating a specific location using this table, Pb should include Service Level C and D primary bending stresses; that is, deadweight (DWV) and safe shutdown earthquake (SSE), for example.

Table 1. Allowable Flaw Size Pma.

psi Pb, psi Z

SF Pb', psi 0, rad 0, ° c, in 2477 1000 1.00 1.39 2356 1.996 114 8.6 2477 2000 1.00 1.39 3746 1.921 110 8.3 2477 3000 1.00 1.39 5136 1.853 106 8.0 2477 4000 1.00 1.39 6526 1.791 103 7.7 2477 5000 1.00 1.39 7916 1.732 99 7.5 2477 6000 1.00 1.39 9306 1.677 96 7.2 2477 7000 1.00 1.39 10696 1.625 93 7.0 2477 8000 1.00 1.39 12086 1.575 90 6.8 2477 9000 1.00 1.39 13476 1.527 87 6.6 2477 10000 1.00 1.39 14866 1.482 85 6.4 2477 11000 1.00 1.39 16256 1.438 82 6.2 2477 12000 1.00 1.39 17646 1.395 80 6.0 2477 13000 1.00 1.39 19036 1.353 78 5.8 2477 14000 1.00 1.39 20426 1.313 75 5.7 2477 15000 1.00 1.39 21816 1.274 73 5.5 2477 16000 1.00 1.39 23206 1.236 71 5.3 2477 17000 1.00 1.39 24596 1.198 69 5.2 2477 18000 1.00 1.39 25986 1.161 67 5.0 2477 19000 1.00 1.39 27376 1.125 64 4.9 2477 20000 1.00 1.39 28766 1.090 62 4.7 4.2 Leakage Although PICEP has not been qualified under SI's Quality Assurance (QA) program, it is widely accepted for use in LBB evaluations and has been evaluated by the US NRC [5]. As a check, the SI-developed program pc-LEAK, which has been qualified under SI's QA program, is used.

The previously-stated pipe section properties of D. = 8.625" and t = 0.148" are input. Maximum crack size of 4" is used [3]. Material properties are taken as follows, at a temperature of 2000F [41:

  • Modulus of Elasticity = 27,600 ksi
  • Ultimate tensile strength = 71.0 ksi
  • Yield strength = 25.0 ksi
  • Flow stress = (71.0 + 25.0)/2 = 48.0 ksi
  • a = 4.7, n = 3.8, taken at 750F [7]

Other leakage input is described as follows. The roughness is 0.000197 inch [6]. Several values of sustained bending stress are used ranging from 0 to 20 ksi. Pressure and temperature are 184.7 psia Revision Preparer/Date WFW 03/18/04 Checker/Date AFD 03/18/04 File No.

MNS-02Q-301 Page 5 of 9

and 1900F [3]. The entrance loss coefficient is chosen as 0.61, which is also the default value. The following other parameters are also input to PICEP:

  • MODE = 0 (compute critical crack length, crack opening displacement, and leakage)
  • IPLAS = 2 (perform plastic zone correction)
  • ISOL = 2 (combined tension and bending solution)
  • IFDIR = 0 (circumferential crack)
  • IFAREA = 1 (elliptical crack)
  • NDIV = 8 (number of crack length increments)
  • COD = 0 (ignored since MODE is not 1)
  • TRACT = 0 (pipe axial nonpressure load)
  • BMOM = 0 (pipe bending moment, stress is input instead)
  • PMSTR = 0 (pipe membrane stress, pressure is input instead)
  • IN = 3 (initially subcooled liquid water)
  • PB = external pressure = 14.7 psia
  • AR = ratio of the crack exit to inlet area = 1.0 N45 = number of 45 deg turns = 0
  • N90 = number of 90 deg turns = 0
  • ZF = 1.0 (assume plastic collapse)
  • SFV = 1.0 (safety factor for critical crack length)

The following input is specific to pc-LEAK. From equation 27 of the PICEP manual, the 0.61 entrance loss coefficient corresponds to a factor on pressure drop of 1/0.612 = roughly 2.7, which is the input used for pc-LEAK. The pc-LEAK case for analysis is case 5: liquid water, circumferential crack, and axial plus bending stress. The following other input is used:

  • YES for abbreviated output file
  • 0 = Initial average crack opening, inches
  • 2 = Beta for plastic zone corrections (plane stress)
  • *1 = Iterations for plastic zone correction
  • 0.2 = Increment for crack length (2c)

Table 2 shows the leakage rates calculated by PICEP, based on a range of flaw angles and bending moments, and Figure 1 plots these results. Results calculated by pc-LEAK are somewhat smaller, but similar in magnitude. For evaluating a specific location using this table, Pb should include only sustained loads, but should include secondary as well as primary loads; that is, DW, thermal expansion (TE), and thermal anchor movement (TAM), for example.

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Table 2. Leakage Rate versus Crack Length (2c) and Sustained Bending Stress (Pb)

Pt=

Pb=

Pb=

0 ksi 2.5 ksi 5 ksi Leakage, gpin Pb=

Pb=

PbP b

b=

Pb=

Pb=

7.5 ksi 10 ksi 12.5 ksi 15 ksi 17.5 ksi 20 ksi 2c, in 0.2 0.4 0.6 0.8 1.2 1.4 1.6 1.8 2

2.2 2.4 2.6 2.8 3

3.2 3.4 3.6 3.8 4

0.0001 0.0002 0.0005 0.0010 0.0018 0.0004 0.0014 0.0029 0.0066 0.0146 0.0013 0.0041 0.0100 0.0228 0.0477 0.0028 0.0096 0.0247 0.0541 0.1087 0.0053 0.0201 0.0497 0.1052 0.2043 0.0090 0.0365 0.0878 0.1805 0.3404 0.0148 0.0605 0.1418 0.2842 0.5227 0.0238 0.0938 0.2147 0.4204 0.7573 0.0362 0.1382 0.3093 0.5931 1.0495 0.0528 0.1956 0.4284 0.8067 1.4073 0.0745 0.2678 0.5751 1.0658 1.8376 0.1021 0.3568 0.7523 1.3751 2.3491 0.1366 0.4647 0.9633 1.7399 2.9509 0.1791 0.5935 1.2114 2.1664 3.6538 0.2308 0.7454 1.5002 2.6607 4.4695 0.2928 0.9227 1.8338 3.2298 5.3804 0.3665 1.1277 2.2163 3.8834 6.4205 0.4534 1.3632 2.6524 4.6282 7.6115 0.5549 1.6316 3.1473 5.4750 8.9720 0.6726 1.9360 3.7066 6.4148 10.5221 0.0041 0.0300 0.0927 0.2026 0.3679 0.5966 0.8967 1.2773 1.7482 2.3216 3.0093 3.8160 4.7416 5.8235 7.0833 8.5422 10.2266 12.1666 14.3925 16.9441 0.0084 0.0573 0.1671 0.3504 0.6176 0.9801 1.4503 2.0426 2.7707 3.6248 4.6488 5.8657 7.3019 8.9870 10.9549 13.2418 15.8939 18.9584 22.4866 26.5473 0.0163 0.1013 0.2800 0.5671 0.9773 1.5272 2.2305 3.0883 4.1434 5.4254 6.9644 8.7971 10.9646 13.5127 16.4953 19.9711 24.0128 28.6900 34.0933 40.3212 0.0292 0.1668 0.4407 0.8696 1.4752 2.2570 3.2565 4.5089 6.0497 7.9232 10.1746 12.8618 16.0414 19.7817 24.1660 29.2858

  • 35.2494 42.1508 50.1464 59.3774 Revision 0

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100 10 Ea x!

0 1!

~

c ~ l'

-- 4 7 -1-

I 1.1 -

,,f.

-.-0,..E~

It~ if I, I

I ma'-%

.lv-.

-

. I..- 'k





41, -

'. c",

-""

.-j"', "- ' " e '-.

0.

i F

I I

II I

L 77'7

-4 Pb=0 ksi

-U-- Pb=2.5 ksl

- - Pb-5 ksi

-+-.

Pt,=7.5 ksi

-*( Pt,=1ksi Pt=-12.Skcii Pb=15 ksl P-Pb1 7.5 MIl

-Pbb=20 kiD 0.001

^ ALAS

  • '.s4P.*be.I'I+I9kS>'
t. or 0.1 Flaw length (2c, In 10 Figure 1. Leakage Rate versus Crack Length (2c) and Sustained Bending Stress (Pb) 5.0 DISCUSSION The allowable flaw sizes show that the piping is very flaw tolerant as the pressure stress is very low.

Austenitic stainless steel welded by GTAW (MIG welding) fails in a very ductile manner, such that the Appendix C approach is applicable to evaluate the flaws in the piping. It is conservative to add the length of any actual flaw indications to compare against the calculated single flaws, in terms of assessing the margin.

The assumption of a smooth crack is conservative in that it minimizes the flow loss; therefore, the calculated leakage rates are conservatively high. PICEP generally calculates higher leakage than pc-LEAK because the inclusion of plasticity (which is handled only through a plastic zone correction factor in pc-LEAK) produces larger crack opening areas. For this calculation, that is conservative.

Note that the value of Pb for calculating allowable flaw size should include Service Level C and D primary bending stresses (typically DW + SSE), while Pb for calculating leakage should include primary plus secondary stresses due to sustained loads (typically DW + TE + TAM).

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6.0 REFERENCES

1. ASME Boiler and Pressure Vessel Code,Section XI, 1998 Edition with 2000 Addenda.
2. Norris, D. M., and Chexal, B., PICEP: Pipe Crack Evaluation Computer Program, EPRI Report No. NP-3596-SR, Revision 1.
3. E-mail from Hoang Dinh (Duke) to Art

Deardorff and Bill Weitze (SI) dated 3/16/2004 12:

07 PM (PST),

Subject:

Re: Design Input for Crack and Leakage Calculations, SI File No. MNS-02Q-201.

4. ASME Boiler and Pressure Vessel Code,Section III Appendices, 1989 Edition.
5. NUREG/CR-5128, Evaluation and Refinement of Leak-Rate Estimation Models, Battelle for USNRC, April 1991.
6. Calculation of Leak Rates Through Cracks in Pipes and Tubes, EPRI Report No. NP-3395, December 1983.
7. Zahoor, Akram, Ductile Fracture Handbook, EPRI Report No. NP-6301-D, Volume 3, January 1991 (Research Project 1757-69, prepared for Novetech Corporation and the Electric Power Research Institute).
8. pc-LEAK, Version 2.0-8/20/98, Structural Integrity Associates.

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