HNP-12-133, Relief Request I3R-10 Spent Fuel Pool Cooling Piping, Request for Additional Information Response
| ML12353A317 | |
| Person / Time | |
|---|---|
| Site: | Harris  |
| Issue date: | 12/17/2012 |
| From: | Corlett D Duke Energy Carolinas |
| To: | Office of Nuclear Reactor Regulation, Document Control Desk |
| References | |
| HNP-12-133 | |
| Download: ML12353A317 (16) | |
Text
David H. Corlett Supervisor, Licensing/Regulatory Programs Harris Nuclear Plant 5413 Shearon Harris Rd New Hill NC 27562-9300 919-362-3137 December 17, 2012 10 CFR 50.55a Serial: HNP-12-133 ATTN: Document Control Desk U.S. Nuclear Regulatory Commission Washington, DC 20555-0001 Shearon Harris Nuclear Power Plant, Unit 1 Docket No. 50-400
Subject:
Relief Request I3R-10 Spent Fuel Pool Cooling Piping Request for Additional Information Response
References:
- 1. Letter from D. H. Corlett to the U.S. Nuclear Regulatory Commission, Relief Request I3R-10 Spent Fuel Pool Cooling Piping, Serial HNP-12-099, dated November 8, 2012 (ADAMS Accession No. ML12313A442)
- 2. Letter from A. T. Billoch Colón to C. Burton, Request for Additional Information for Review Regarding Relief Request 13R-10 Spent Fuel Pool Cooling Piping, dated December 4, 2012 (ADAMS Accession No. ML12321A099)
Ladies and Gentlemen:
By letter to the U.S. Nuclear Regulatory Commission (NRC) dated November 8, 2012, Carolina Power & Light Company requested approval of a relief request for the Shearon Harris Nuclear Power Plant, Unit 1 (HNP) Inservice Inspection Program third ten-year interval (Reference 1).
Relief Request I3R-10 provided a proposed alternative for the repair of a leaking pipe in the spent fuel pool cooling system.
NRC staff reviewed the HNP submittal and determined that additional information is required to complete their review. The request for additional information (RAI) was provided to HNP in a letter dated December 4, 2012 (Reference 2). The HNP response to the RAI is provided in the enclosure to this letter.
HNP-12-133 Page 2 HNP proposes the following revised regulatory commitment upon NRC approval of the requested relief.
Leakage shall be observed by daily walkdowns. Frequent periodic physical measurements and ultrasonic thickness measurements in the vicinity of the flaws at no more than 30 day intervals shall be used to monitor flaw size. If either the flaw size or leakage exceeds the administrative limit prior to the next refueling outage in the fall of 2013, the degraded pipe will be repaired or replaced. The length of the flaw will be considered to be four times the surface length of the flaws in each weld.
Please refer any questions regarding this submittal to John Caves at (919) 362-2406.
Sincerely,
Enclosure:
Relief Request I3R-1 0 Spent Fuel Pool Cooling Piping Request for Additional Information Response cc: Mr. J.D. Austin, NRC Sr. Resident Inspector, HNP Ms. A. T. Billoch Colon, NRC Project Manager, HNP Mr. V. M. McCree, NRC Regional Administrator, Region II
U.S. Nuclear Regulatory Commission Relief Request I3R-10 RAI Response Enclosure to HNP-12-133 Page 1 of 14 Enclosure Shearon Harris Nuclear Power Plant, Unit 1 Docket No. 50-400 Relief Request I3R-10 Spent Fuel Pool Cooling Piping Request for Additional Information Response
U.S. Nuclear Regulatory Commission Relief Request I3R-10 RAI Response Enclosure to HNP-12-133 Page 2 of 14
References:
- 1. Letter from D. H. Corlett to the U.S. Nuclear Regulatory Commission, Relief Request I3R-10 Spent Fuel Pool Cooling Piping, Serial HNP-12-099, dated November 8, 2012 (ADAMS Accession No. ML12313A442)
- 2. Letter from A. T. Billoch Colón to C. Burton, Request for Additional Information for Review Regarding Relief Request 13R-10 Spent Fuel Pool Cooling Piping, dated December 4, 2012 (ADAMS Accession No. ML12321A099)
By letter to the U.S. Nuclear Regulatory Commission (NRC) dated November 8, 2012, Carolina Power & Light Company requested approval of a relief request for the Shearon Harris Nuclear Power Plant, Unit 1 (HNP) Inservice Inspection Program third ten-year interval (Reference 1).
Relief Request I3R-10 provided a proposed alternative for the repair of a leaking pipe in the spent fuel pool cooling system.
NRC staff reviewed the HNP submittal and determined that additional information is required to complete their review. The request for additional information (RAI) was provided to HNP in a letter dated December 4, 2012 (Reference 2). The HNP response to the RAI is provided below.
Request 1 The licensee submitted the relief request based on the impracticality argument pursuant to Title 10, Code of Federal Regulations (10 CFR), Part 50, paragraph 50.55a(g)(5)(iii).
The NRC staff understands that it would be more appropriate if the relief request were submitted based on hardship and unusual difficulties pursuant to 10 CFR 50.55a(a)(3)(ii).
Discuss why the relief request was submitted under 10 CFR 50.55a(g)(5)(iii) and not 10 CFR 50.55a(a)(3)(ii).
Response 1 The relief request was submitted under impracticality per 10 CFR 50.55a(g)(5)(iii).
Guidance in Generic Letter 90-05, Guidance for Performing Temporary Non-Code Repair of ASME Code Class 1, 2, and 3 Piping, indicates the inability to perform a repair within a required time frame supports a conclusion by the staff that the repair is impractical. Due to the time needed for design, fabrication, procurement, testing, and planning associated with the use of a mechanical plug to isolate the repair location from the spent fuel pool, it is impractical to complete the code repair during the 30 days considered typically reasonable for the repair activity.
Implementation of Code Case N-513 normally uses volumetric inspection for initial characterization of flaws, monitoring of flaw growth, and extent of condition inspections.
The use of volumetric inspection is not practical because the surface conditions are not acceptable for a qualified volumetric inspection, and surface profiling the welds could propagate or worsen the extent of the flaws. Causes of impracticality include potential damage to a system or component.
U.S. Nuclear Regulatory Commission Relief Request I3R-10 RAI Response Enclosure to HNP-12-133 Page 3 of 14 Prior to submittal of the HNP relief request, NRC staff recommended HNP review a relief request submitted by Florida Power and Light for Turkey Point, Unit 3 (ML110830895) for a similar condition where a code repair could not be completed due to plant conditions. In the approval of that relief, NRC staff cited that impracticality was more appropriate than the alternative based on hardship because it was impractical to perform the necessary repair on the degraded piping when the degraded piping was required to be used. That condition also applies to the HNP relief request, because the spent fuel piping must remain connected to the spent fuel pool until a mechanical plug is available.
An alternative basis for relief that would also be valid is hardship or unusual difficulty without a compensating increase in level of quality or safety in accordance with 10 CFR 50.55a(a)(3)(ii). Hardship is caused by the need for a hardware change, the fabrication of a mechanical plug to isolate the repair location from the spent fuel pool to provide conditions allowing the code repair. Regulatory commitments described herein to monitor the flaw and take corrective action in the event that the flaw sizes approach limits provide reasonable assurance that structural integrity will be maintained.
Therefore, there is no compensating increase in level of quality or safety.
Request 2 Section 4 of the relief request, Impracticality of Compliance, states that volumetric inspections per ASME Code Case N-513-3 are impractical and the code case will not be invoked. However, Section 6, Proposed Alternative and Basis for Use, requires that the flaw evaluation be performed in accordance with ASME Code Case N-513-3, Section 3.
Clarify whether the relief request follows ASME Code Case N-513-3. If the relief request follows the code case, discuss the deviations and exceptions from the code case.
If the relief request is not based on the code case, discuss the technical basis of the relief request.
Response 2 The relief request did not invoke code case N-513-3, similar to the precedent request approved by NRC staff for Catawba (ML11187A001). Relief was requested from ASME Boiler and Pressure Vessel Code, IWB-3522.1, which requires corrective action to meet the requirements of IWB-3142 and IWA-5250 prior to continued service upon discovery of leakage from non-insulated components.
The reference to code case N-513-3 was provided as similar alternatives also considered acceptable to the NRC. The technical basis of the relief request is that the alternatives provided in Section 6 a) through g) of the relief request, with bases presented in 1) through 8) of the same section, and supplemented by regulatory commitments proposed herein, provide reasonable assurance of structural integrity.
U.S. Nuclear Regulatory Commission Relief Request I3R-10 RAI Response Enclosure to HNP-12-133 Page 4 of 14 Request 3 Section 6(a) of the relief request states that"...[t]he subsurface length of the flaw will be assumed to be four times the surface length for characterization purposes..."
(1) Discuss the technical basis for the factor of 4 and how the factor of 4 is adequate to characterize the subsurface flaw length.
(2) Discuss the degradation mechanism of the flaws in the subject pipe.
Response 3 (1) Flaw geometry will be characterized by physical measurement, rather than volumetric inspection. In the absence of volumetric characterization of the flaw, engineering judgment was used to bound the possible subsurface characteristics of the flaw. Ultrasonic thickness measurements confirmed that there was no general wall thinning. With no general wall thinning, a factor of four is very conservative.
(2) The likely degradation mechanism is stress corrosion cracking. HNP plans to take samples during the repair activity and perform analysis to better understand the cause of the flaws.
Request 4 Section 6(d) of the relief request requires a flaw evaluation to be performed. Discuss the flaw evaluation in detail or submit the flaw evaluation. The flaw evaluation should include the information on the flaw size at the time of discovery, the predicted flaw size on the last date on which the licensee must repair the pipe (i.e., November 30, 2013), and the allowable flaw size.
Response 4 The flaw evaluation is included as an attachment to this document. The flaw evaluation did not predict flaw growth rates, because HNP credits frequent periodic inspections of no more than 30 day intervals to determine if flaws are growing and to establish the time at which the detected flaws will grow to the allowable size. The allowable flaw sizes from the flaw evaluation are 27.4 inches for axial flaws and 17.3 inches for circumferential flaws.
Request 5 Section 6(d) of the relief request states that [f]law acceptance criteria shall assume that the length of the flaw is four times the surface length to account for the lack of information associated with subsurface characterization of the flaws..." Section 6(e) states that "...[t]he allowable size limit will assume that the length of the flaw is four
U.S. Nuclear Regulatory Commission Relief Request I3R-10 RAI Response Enclosure to HNP-12-133 Page 5 of 14 times the surface length to account for the lack of information associated with volumetric characterization of the flaws..." Section 8, Regulatory Commitment, states that "...[t]he allowable size limit will assume that the length of the flaw is four times the surface length to account for the lack of information associated with volumetric characterization of the flaws..." Clarify the terminology "flaw acceptance criteria" and "the allowable size limit" based on calculations using materials properties and applied loading of the pipe, not based on an assumption. It appears that the above statements are related to how to size the detected flaw, rather than the allowable flaw size.
Response 5 The allowable flaw sizes from the flaw evaluation are 27.4 inches for axial flaws and 17.3 inches for circumferential flaws. This is based on calculations using materials properties and applied loading of the pipe. The allowable flaw size, allowable size limit, and flaw acceptance criteria all refer to the flaw evaluation results demonstrating that flaws up to 27.4 inches for axial flaws and 17.3 inches for circumferential flaws preserve structural integrity. The regulatory commitment was reworded to provide improved clarity.
Request 6 Section 6(e) of the relief request states that "...[f]requent periodic surface inspections of no more than 30 day intervals shall be used to determine if flaws are growing and to establish the time, tallow, at which the detected flaw will reach the allowable size..."
Section 6(1) states that "...[u]se of physical measurement of surface flaw length in lieu of volumetric inspection is satisfactory based upon the proposal to use four times the surface length of the flaw for flaw characterization, evaluation, and monitoring of flaw growth rate..."
Based on the above two statements, confirm the following:
(1) The licensee will measure the flaw length on the outside surface of the degraded pipe at least once every 30 days. The licensee will multiply the flaw length on the pipe outside surface by 4 and record it as the detected flaw length.
If the detected flaw length exceeds the allowable flaw length, the licensee will repair the pipe immediately per the ASME Code.
(2) In addition to the allowable flaw length, discuss whether there is a need to implement an administrative flaw size (which would be less than the allowable flaw size) beyond which more frequent inspections and monitoring will be taken.
(3) Discuss why an allowable leak rate is not specified.
U.S. Nuclear Regulatory Commission Relief Request I3R-10 RAI Response Enclosure to HNP-12-133 Page 6 of 14 Response 6 (1) HNP will determine the outside surface flaw length by physical measurement at least once every 30 days. HNP will multiply the combined outside surface flaw length of all the flaws in each weld by four and treat it as the flaw length. If the flaw length exceeds the allowable flaw length, HNP will repair the pipe immediately per the ASME Code.
(2) HNP will implement an administrative limit on flaw size. If flaws in a weld grow to a combined surface length of two inches, corresponding to a flaw length of eight inches, HNP will repair the pipe immediately per the ASME Code. This will ensure that the flaw size does not exceed the allowable flaw length prior to performing the code repair.
(3) The current leak rate is negligible. The makeup capability to the spent fuel pools is 230 gallons per minute. HNP will impose an administrative limit on leakrate of 5 gallons per minute. If the leakrate reaches the administrative limit, HNP will repair the pipe immediately.
Request 7 Although Section 6(f) requires a daily walkdown, Section 8, Regulatory Commitment, does not specify the daily walkdown. In addition, Section 6(g)(3) states that ultrasonic thickness examinations were performed in the areas directly adjacent to the flawed welds.
However, Section 8, Regulatory Commitment, does not mention ultrasonic examinations of pipe wall thickness. The licensee must either include in the Regulatory Commitment, the performance of periodic pipe wall thickness measurements using ultrasonic technique and the performance of daily walkdowns or justify their absence.
Response 7 HNP revises the Regulatory Commitment in Section 8 as follows:
Leakage shall be observed by daily walkdowns. Frequent periodic physical measurements and ultrasonic thickness measurements in the vicinity of the flaws at no more than 30 day intervals shall be used to monitor flaw size. If either the flaw size or leakage exceeds the administrative limit prior to the next refueling outage in the fall of 2013, the degraded pipe will be repaired or replaced. The length of the flaw will be considered to be four times the surface length of the flaws in each weld.
U.S. Nuclear Regulatory Commission Relief Request I3R-10 RAI Response Enclosure to HNP-12-133 Page 7 of 14 Request 8 ASME Code Case N-513-3, paragraph 2(g) states that if examinations reveal the flaw growth rate to be unacceptable, a repair or replacement shall be performed. Paragraph 2(h) states that repair or replacement shall be performed no later than when the predicted flaw size from either periodic inspection or by the flaw growth analysis exceeds the acceptance criteria of [section] 4 or the next scheduled outage, whichever occurs first.
(1) Discuss the unacceptable (i.e., allowable) flaw growth rate and/or flaw size.
(2) Section 8, Regulatory Commitment, should state that "If the measured flaw growth rate or detected flaw size exceeds the unacceptable flaw growth rate or unacceptable flaw size prior to the next refueling outage in the fall of 2013, the degraded pipe will be repaired or replaced..." If the degraded pipe will not be repaired or replaced in this scenario, provide justification.
Response 8 (1) Unacceptable flaw size is any flaw greater than the allowable flaw sizes calculated by the flaw evaluation, which are 27.4 inches for axial flaws and 17.3 inches for circumferential flaws. Flaw growth rate was not calculated because frequent periodic inspections and an administrative limit on flaw size will be used to ensure a code repair is performed prior to reaching a condition where structural integrity is significantly challenged.
(2) The regulatory commitment was revised in response 7 to ensure the code repair will occur if the detected flaw size reaches the administrative limit on flaw size or the next refueling outage in fall of 2013.
Revised Regulatory Commitment Leakage shall be observed by daily walkdowns. Frequent periodic physical measurements and ultrasonic thickness measurements in the vicinity of the flaws at no more than 30 day intervals shall be used to monitor flaw size. If either the flaw size or leakage exceeds the administrative limit prior to the next refueling outage in the fall of 2013, the degraded pipe will be repaired or replaced. The length of the flaw will be considered to be four times the surface length of the flaws in each weld.
U.S. Nuclear Regulatory Commission Relief Request I3R-10 RAI Response Enclosure to HNP-12-133 Page 8 of 14 Enclosure - Attachment 1 Flaw Analysis (6 pages plus cover)
Shearon Harris Nuclear Power Plant, Unit 1 Docket No. 50-400 Relief Request I3R-10 Spent Fuel Pool Cooling Piping Request for Additional Information Response
ATTACHMENT E EC88099 Z04R2 Page 1 of 6 N513-3, 3.1 (b),Section XI Article C-5000 Problem
- 1. P er CR 55384 8, durin g the performance of EST-33 9 a potential thru wall lea k wa s found ~
6 " north of th e socko let fo r 1 SF-71 . There ar e ~ 3 table sp oons of wh ite dry b oron on the b ottom of the pipe. The b oron is located at the inte rse ction of a long itud inal weld an d a circumferential weld . . Also n ote d d ry boron ~ 1 cup on the Sou th west sid e of fla nge for 1 SF-17 W Rs 5 47987 and 54 298 we re g enerated.
- 2. CRs 0 05549 34 a nd 555527 identified two additional pin hole lea ks on the line same line 3 SF12-176 SB-1&4 , on the So uth side of the Spent Fu el P ool (se e Attach me nt B). These p inhole leaks are also on the weld an d o ne is appr oximately 1 /32 an d the other is a pproximately 1/64.
Discussion The provisions of Code Case N-513 are applicable to Class 3 piping whose maximum operating temperature does not exceed 200 deg F and whose maximum operating pressure does not exceed 275 psig.
The flaw evaluation criteria are permitted for pipe and tube. The flaw evaluation criteria are permitted for adjoining fittings and flanges to a distance of (Ro t)1/2 from the weld centerline.
The provisions of the flaw evaluation per Code Case N-513 demonstrates the integrity of the piping component and not the consequences of the leakage.
The following evaluation is in accordance with Code Case N-513, paragraph 3.0(b). applicable to stainless steel.
For planar flaws, the flaw shall be bounded by a rectangular or circumferential planar area in accordance with the methods described in Appendix C. The geometry of a through-wall planar flaw is shown in Fig's. 1 & 2.
The evaluation is based on fully-plastic limit criteria load Line Number: 3SF12-176SB-1&4 ( 12- inch Schedule 40S pipe) analyzed in stress calculations 2850-8 and 2850-4 From the AR's mentioned above the pin hole leaks are 1/32" dia max at three locations. The combined flaw size will be 3/32". Conseravtively consider a total flaw of 1/4".
DESIGN INPUT COMPONENT WALL THK t := 0.375 in OPERATING PRESSURE p := 85psi DESIGN PRESSURE P := 100 psi OPERATING TEMPERATURE T := 150 °F DESIGN TEMPERATURE 200 °F PIPE OUTSIDE DIA Do := 12.75 in Do t R := = 6.188 in 2
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ATTACHMENT E EC88099 Z04R2 Page 2 of 6 FLOW STRESS MATERIAL TYPE SS
" all material properties shall be based on operating temperature" MATERIAL YIELD STRENGTH Sy := 30000psi MATERIAL ULT. TENSILE STRENGTH Su := 75000psi Axial Flaw Evalutation l
t R
Fig 2. Axial Flaw AXIAL CRACK LENGTH FOR THRU WALL FLAW The following axial flaw evaluation is based on equations 1, 2 & 3 of Code Case N-513-3, Section 3.0 (b) with structural factors on primary membrane stress as specified in C-2622,Section XI.
Service Level A 2.7 2.4 Service Level B (C-2622)
SFm := Service Level C 1.8 1.3 Service Level D Do (2) h := P h = 1700 psi 2 t f :=
( Sy + Su) = 52500 psi (3) 2 THE AXIAL FLAW LENGTH FOR THRU WALL FLAWS IS:
1 Service Level A 2 27.423 (1) f 2
= 30.876 in Service Level B lallA := 1.58 R t SFm h 1
41.222 Service Level C 57.123 Service Level D ACCEPTABLE AXIAL FLAW LENGTH OF 27.423" MINIMUM IN AXIAL DIRECTION.
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ATTACHMENT E EC88099 Z04R2 Page 3 of 6 Circumferential Flaw Evaluation 2C t
NA R
D Figure 1 Circumferential Flaw For planar flaws in austenitic piping, the evaluation procedure of Appendix C, subsection C-5300 is used. Flaw depths up to 100% of wall thickness is evaluated with the flaw depth to thickness ratio, a/t, is to unity.
CHECK COMBINE BEND STRESSES FOR CIRCUMFERENTIAL FLAW FOR ALL SERVICE LEVELS ( REF. C-5320)
Pipe stresses from calc 2850-4 and 2850-8 are enveloped to obtain the following are the maximum stresses:
Eq.8 = 2983 psi: Eq.9U = 8562 psi, Eq. 9E = 10833 psi and Eq.9F =10983 psi Do Membarane Stress m := P = 850 psi 4 t a := t crack thru wall For pentration flaw not penetrating compressive side of the pipe such that + <= , between applied load and flaw depth at incipient collapse given below. See Fig 1 f
b := 2 2 sin ( ) sin ( )
a C-5321 t
1 a m
- =
2 t f Combining two equations f 1 a m a b ( ) := 2 2 sin sin ( )
2 t f t
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ATTACHMENT E EC88099 Z04R2 Page 4 of 6 SERVICE LEVEL A BENDING STRESS Sc FROM CALC W/O SIF :
SFmA := 2.7 SFbA := 2.3 C-2621 Allowable bednding stress for circumferentialy flawd pipes can be calulated by N513-3 formula (5) b ( )
m 1 1
Sc :=
SFbA C-5321. (5)
SFmA For actual bending Level A stress from pipe stress Sc := 2983 psi, the angle can be calculated by solving two equations.
This calculation shall be repeated for all aplicable service levels.
- = .1 rad Moment stress due to dead weight and pressure form stres calc 2850-8 Sc := 2983 psi f a m a 2 2 sin 1 sin ( )
2 t f t
1 1 S , C-5321 out := root SFbA m c SFmA out = 1.778 rad := out L := Do L = 22.664 in 1 a m
- = = 0.657 rad + = 2.434 rad C-5321 2 t f
= 1.778 if ( + < , "OK" , "NG" ) = "OK" SERVICE LEVEL B BENDING STRESS Sc FROM CALC W/O SIF :
SFmB := 2.4 SFbB := 2.0 C-2621 b ( )
m 1 1
Sc :=
SFbB SFmB Sc := 8562 psi Bending Level B stress from pipe stress calc
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ATTACHMENT E EC88099 Z04R2 Page 5 of 6 f a m a 2 2 sin 1 sin ( )
2 t f t
1 1 S ,
out := root SFbB m c SFmB out = 1.363 rad := out L := Do L = 17.381 in 1 a m
- =
2 t f
= 0.864 rad + = 2.227 rad if ( + < , "OK" , "NG" ) = "OK" SERVICE LEVEL C BENDING STRESS Sc FROM CALC W/O SIF :
SFmC := 1.8 SFbC := 1.6 C-2621 b ( )
m 1 1
Sc :=
SFbC SFmC Bending Level C stress from pipe stress calc Sc := 10833 psi f a m a 2 2 sin 1 sin ( )
2 t f t
1 1 S ,
out := root SFbC m c SFmC out = 1.369 rad := out L := Do L = 17.461 in 1 a m
- = = 0.861 rad + = 2.23 rad 2 t f if ( + < , "OK" , "NG" ) = "OK"
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ATTACHMENT E EC88099 Z04R2 Page 6 of 6 SERVICE LEVEL D BENDING STRESS Sc FROM CALC W/O SIF :
SFmD := 1.3 SFbD := 1.4 C-2621 b ( )
m 1 1
Sc :=
SFbD SFmD Sc := 10833 psi Bending Level D stress from pipe stress calc f a m a 2 2 sin 1 sin ( )
2 t f t
1 1 S ,
out := root SFbD m c SFmD out = 1.46 rad := out L := Do L = 18.617 in 1 a m
- =
2 t f = 0.815 rad
+ = 2.275 rad if ( + < , "OK" , "NG" ) = "OK" CHECK MEMBRANE STRESSES FOR CIRCUMFERENTIAL FLAW FOR ALL SERVICE LEVEL A CONDITION ( REF.
C-5322) membrane stress from pipe stress calc. or above calulated long stress.
m = 850 psi
- = 1.363 from service Level B - shortest allowable crack length sin ( ) = 0.978 1
- = sin 0.5 sin ( )
a
- = 0.511 t
mc := f 1 2 a
t mc St :=
SFbA St = 20348.46 psi > ( m) = 850 psi CONCLUSION:
Bases on the above evaluation, Maximum flaw length allowed is 27.423" for axial direction and 17.381" in the circumferential direction to maintain structural integrity of the piping. Since the combined flaw from three location is less than 1/4", this condition is acceptable.
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