ML072780532
| ML072780532 | |
| Person / Time | |
|---|---|
| Site: | Oyster Creek |
| Issue date: | 08/14/1997 |
| From: | AmerGen Energy Co |
| To: | NRC/SECY |
| SECY RAS | |
| References | |
| 50-219-LR, AmerGen-Applicant-45, RAS 14259 | |
| Download: ML072780532 (6) | |
Text
RA.S I4.?s'y U.S. NUCLEAR REGULATORY GONIMt'ION In theMatterof kAFVA k\\
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Docket No.J)
C21,9-L., Official Exhibit No.
F E icensec i'tren~r PPLICANT'S EXHIBIT 45 NR St ff V
OENTIFIED on*1
" Witne.*s/saneli A-M~ona~w:
ipi~iii J~E~ CTED BOILER AND PRESSU'RE VESSEL CODE CASE N-513 DOCKETED USNRC Approval Date: Ai See Numeric Inde.
and any reaffirr Case N-513 Evaluation Criteria for Temporary Acceptance of Flaws in Class 3 Piping Section XM, Division 1
- iquiry: What rules may be used for temporary ac-ceptance of flaws, including through-wall flaws, in moderate energy Class 3 piping, without repair or replacement?
Reply: It is the opinion of the Committee that the following rules may be used to accept flaws, including through-wall flaws, in moderate energy Class 3 piping, without repair or replacement for a limited time, not exceeding the time to the next scheduled outage.
1.0 SCOPE (a) These requirements apply to the ASME Section III, ANSI B31.1, and ANSI B31.7 piping, classified by the Owner as Class 3.
(b) The provisions of the Case apply to Class 3 piping whose maximum operating temperature does not exceed 200'F and whose maximum operating pressure does not exceed 275 psig.
(c) The following flaw evaluation criteria are permit-ted for pipe and tube. The flaw evaluation criteria are permitted for adjoining fittings and flanges to a distance of (Rot)" 2 from the weld centerline.
(d) The provisions of this Case demonstrate the integrity of the item and not the consequences of leakage. It is the responsibility of the Owner to demon-strate system operability considering effects of leakage.
2.0 PROCEDURE (a) The flaw geometry shall be characterized by volumetric inspection methods or by physical measure-ment. The full pipe circumference at the flaw location shall be inspected to characterize the length and depth of all flaws in the pipe section.
(b) Flaw shall be classified as planar or nonplanar.
(c) When multiple flaws, including irregular (com-pound) shape flaws, are detected, the interaction-and combined area loss of flaws in a given pipe section shall be accounted for in the flaw evaluation.
ugust 14, 1997 October 1, 2007 (10:45pm) x for expiration OFFICE-OF SECRETARY nation dates.
RULEMAKINGS AND ADJUDICATIONS STAFF (d) A flaw evaluation shall be performed to determine the conditions for flaw acceptance. Section 3.0 provides accepted methods for conducting the required analysis.
(e) Frequent periodic inspections of no more than 30 day intervals shall be used to determine if flaws are growing and to establish the time at which the detected flaw will reach the allowable size. Alterna-tively, a flaw growth evaluation may be performed to predict the time at which the detected flaw will grow to the allowable size. When a flaw growth analysis is used to establish the allowable time for temporary operation, periodic examinations of no more than 90 day intervals shall be conducted to verify the flaw growth analysis predictions.
([) For through-wall leaking flaws, leakage shall be observed by daily walkdowns to confirm the analysis conditions used in the evaluation remain valid.
(g) If examinations reveal flaw growth rate to be unacceptable, a repair or replacement shall be per-formed.
(h) Repair or replacement shall be performed no later than when the predicted flaw size from either periodic inspection or by flaw growth analysis exceeds the acceptance criteria of Section 4.0, or the next scheduled outage, whichever occurs first. Repair or replacement shall be in accordance with IWA-4000 or IWA-7000, respectively, in Editions and Addenda prior to the 1991 Addenda; and, in the 1991 Addenda and later, in accordance with IWA-4000.
(i) Evaluations and examination shall be documented in accordance with 1WA-6300. The Owner shall docu-ment the use of this Case on the applicable data report form.
3.0 FLAW EVALUATION (a) For planar flaws, the flaw shall be bounded by a rectangular or circumferenrual planar area in accord-ance with the methods described in Appendix C or Appendix H. IWA-3300 shall be used to determine when multiple proximate flaws are to be evaluated as a single flaw. The geometry of a through-wall planar flaw is shown in Fig. 1.
(b) For planar-flaws in austenitic piping, the evalua-tion procedure in Appendix C of Section XI, Division 1, shall be used. Flaw depths up to 100% of wall 765 rFelrAP (cfe=5 -C_ y'- 0 6 9
CASE (continued)
N-513 CASES OF ASME BOILER AND PRESSURE VESSEL CODE a,= (Sy + S&)12 (3) where p = is pressure for the loading condition D0 = is pipe outside diameter of= is the flow stress Sy= is the code yield strength S,= is the code tensile strength and SF= is the safety factor as specified in C-3420 of Appendix C Material properties at the temperature of interest shall be used.
(c) For planar flaws in ferritic piping, the evaluation procedure in Article H-7000 of Appendix H,Section XI, Division 1, shall be used. Flaw depths up to 100%
of wall thickness may be evaluated. When through-wall flaws are evaluated, the formulas for evaluation given in Articles H-7300 and H-7400 of Appendix H may be used, but with values for F0,, Fb, and F applicable to through-wall flaws. Relations for Fm, Fb, and F that take into account flaw shape and pipe geometry (R11 ratio) shall be used. The appendix to this Code Case provides equations for F, Fb, and F for a selected range of Rit. Geometry of a through-wall crack is shown in Fig. 1.
(d) For nonplanar flaws, the pipe is acceptable when the remaining pipe thickness (tp) is greater than or equal to the minimum wall thickness trai):
(a) Circumferential Flaw
-t pDo 2(S + 0.4p)
(4)
(b) Axial Flaw FIG. 1 THROUGH-WALL FLAW GEOMETRY thickness may be evaluated. When through-wall circum-ferential flaws are evaluated, the formulas for evaluation given in Articles C-3320 of Appendix C may be used, with the flaw penetration (alt) equal to unity.
When through-wall axial flaws are evaluated, the allow-able flaw length is:
-~t
= l.58',-
1 (1) o F(SF)pOf/
(2)
=- pD0I2t (2) where p = is the maximum operating pressure at flaw lo-cation S = is the allowable stress at operating temperature Where appropriate, bending load at the flaw location shall be considered in the determination of t*,.
When t, is less than trai, an evaluation shall be performed as given below. The evaluation procedure is a function of the depth and the extent of the affected area as illustrated in Fig. 2.
(1) When the width of wall thinning that exceeds tmi,, Win, is less than or equal to 0.5 (Rotmi,,)2, where R,, is the outside radius and Wm is defined in Fig. 2, the flaw can be classified as a planar flaw and evaluated under para. 3(a) through pari. 3(c). When the above requirement is not satisfied, (2) shall be met.
(2) When the transverse extent of wall thinning that exceeds tmji, Lm(,), is not greater than (Rotmn, )t2,
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CASE (continued)
N-513 CASES OF ASME BOILER AND PRESSURE VESSEL CODE
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FIG. 2 ILLUSTRATION OF NONPLANAR FLAW DUE TO WALL THINNING taroc is determined from Curve 1 of Fig. 3, where L,,qO is defined in Fig. 2. When the above requirement is not satisfied, (3) shall be met.
(3) When the maximum extent of wall thinning that exceeds t j, L,,, is less than or equal to 2.65 (Rotmli)t2 and t,,,m is greater than 1.13t,,,aoc is determined by satisfying both of the following equa-tions:
When the above requirements are not satisfied, (4) shall be met.
(4) When the requirements of (1),
(2) and (3) above are not satisfied, ta* is determined from Curve 2 of Fig. 3. In addition, ta shall satisfy the following equation:
to10C m.5*
+
(7) tm.1.8 I 1-- o
+1.0 t0r,.
0.353L,.
t-->j,,
(5) where o-b is the nominal pipe longitudinal bending stress resulting from all primary pipe loadings.
(6)
(e) For nonferrous materials, nonplanar and planar flaws may be evaluated following the general approach 767
CASE (continued)
N-513 CASES OF ASME BOILER AND PRESSURE VESSEL CODE 1.0 0.8 0.6 0.4 0.2 0
2 0
1 2
3 4
5 6
7 8
Lma)/I f
n FIG. 3 ALLOWABLE WALL THICKNESS AND LENGTH OF LOCALLY THINNED AREA of (a) through (d) above. For ductile materials, the approach given in (b) may be used; otherwise, the approach given in (c) and (d) should be applied. Safety factors provided in Section 4.0 shall be used. It is the responsibility of the evaluator to establish conservative estimates of strength and fracture toughness for the piping material.
4.0 ACCEPTANCE CRITERIA The piping containing a circumferential planar flaw is acceptable for continued temporary service when flaw evaluation provides a safety margin, based on load, of a factor of 2.77 for Level A and B and 1.39 for Level C and D service loading conditions. Piping containing a nonplanar flaw is acceptable for continued temporary service if tp,
taloc, where td., is determined from Section 3(d).
Lower safety factors may be used, provided that a detailed engineering evaluation of continued operation demonstrates that lower safety factors are justified.
5.0 AUGMENTED EXAMINATION An augmented volumetric examination or physical measurement to assess degradation of the affected sys-tem shall be performed as follows:
(a) From the engineering evaluation, the most suscep-tible locations shall be identified. A sample size of at least five of the most susceptible and accessible loca-tions, or, if fewer than five, all susceptible and accessible locations shall be examined within 30 days of detecting the flaw.
(b) When a flaw is detected, an additional sample of the same size as defined in 5(a) shall be examined.
(c) This process shall be repeated within 15 days for each successive sample, until no significant flaw is detected or until 100% of susceptible and accessible locations have been examined.
6.0 NOMENCLATURE c = half crack length D, = outside pipe diameter F= nondimensional stress intensity factor for through-wall axial flaw under hoop stress Fb= nondimensional stress intensity factor for through-wall circumferential flaw under pipe bending stress Fro= nondimensional stress intensity factor for through-wall circumferential flaw under mem-brane stress
= total crack length = 2c eui = allowable axial through-wall length 768
CASE (continued)
N-513 CASES OF ASMFE BOILER AND PRESSURE VESSEL CODE L= maximum extent of a local thinned area with t
<tnom LL, = maximum extent of a local thinned area with t
< tmin L,,(a,)= axial extent of wall thinning below trmi L,(= circumferential extent of wall thinning below train p = maximum operating pressure at flaw location R = mean pipe radius R, = outside pipe radius S=.allowable stress at operating temperature S, = code specified ultimate tensile strength S, = code specified yield strength t= wall thickness tto,= allowable local thickness for a nonplanar flaw that exceeds t,,i, tmln = minimum wall thickness required for pressure loading t,,om = nominal wall thickness t,= minimum remaining wall thickness W,. = maximum extent of a local thinned area perpen-dicular to Lm with t < t m A = nondimensional half crack length for through-wall axial flaw of= material flow stress o'h = pipe hoop stress due to pressure o-b = nominal longitudinal bending stress for primary loading without stress intensification factor 0= half crack angle for through-wall circumferen-tial flaw 769
CASE (continued)
N-513 CASES OF ASME BOILER AND PRESSURE VESSEL CODE APPENDIX I RELATIONS FOR Fm, Fb, AND F FOR THROUGH-WALL FLAWS
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1-1.0 DEFINITIONS For through-wall flaws, the crack depth (a) will be replaced with half crack length (c) in the stress intensity factor equations in Articles H-7300 and H-7400 of Section XI, Appendix H. Also, Q will be set equal to unity in Article H-7400.
1-2.0 CIRCUMFERENTIAL FLAWS For a range of Rit between 5 and 20, the following equations for Fm and Fb may be used:
F. = 1 + Am (011f)'-" +
m (e/"tr)2"5 + C. ((9") 3"5 Fb = 1 + A, (l/.r)I"5
+ B, (t/f7) 2 "5 + Cb (e/ir)3"5 where e= Half crack angle = c/R R= Mean pipe radius t= Pipe wall thickness and Am= -2.02917 + 1.67763 (RIt) - 0.07987 (R/t)2
+ 0.00176 (R/t)3 B,,= 7.09987 - 4.42394 (RIt) + 0.21036 (R/t)2
- 0.00463 (R/t) 3 Cm = 7.79661 + 5.16676 (RIt) - 0.24577 (R/t)2
+ 0.00541 (R/t)3 Ab= -3.26543 + 1.52784 (R =It) - 0.072698 (R/t)2
+ 0.0016011 (R/t)3 Bb= 11.36322 - 3.91412 (RIt) +.0.18619 (R/t)2
- 0.004099 (R/t)3 Cb= -3.18609 + 3.84763 (RI) - 0.18304 (R/t) 2
+ 0.00403 (R/t)3 Equations for F,,, and Fb are accurate for Rlt between 5 and 20 and become increasingly conservative for RI t greater than 20. Alternative solutions for Fm and Fb may be used when Rit is greater than 20.
1-3.0 AXIAL FLAWS For internal pressure loading, the following equation for F may be used:
F= I + 0.072449A + 0.64856A2 m- 0.2327A3 +
0.038154A 4 - 0.0023487A5 where A= c/(Rt)l 2 c = half crack length The equation for F is accurate for A between 0 and
- 5. Alternative solutions for F may be used when A is greater than 5.
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