ML20211A382
| ML20211A382 | |
| Person / Time | |
|---|---|
| Site: | Vogtle  |
| Issue date: | 02/09/1987 |
| From: | Bailey J GEORGIA POWER CO., SOUTHERN COMPANY SERVICES, INC. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| Shared Package | |
| ML20211A387 | List: |
| References | |
| 1031V, GN-1345, NUDOCS 8702190161 | |
| Download: ML20211A382 (9) | |
Text
.
Georgia Power Company Routs 2 Box 299A Waynesboro, Georgia 30830 Telephone 404 554-9961 404 724 8114 Southern Company Serwces,Inc.
Pcst Office Box 2625 Birmingham Alabama 35202 Telephone 205 8706011 Vogtle Proj.ect February 9, 1987 U. S. Nuclear Regulatory Commission File: X7BC35 Attn: Document Control Desk Log:
GN-1345 Washington, D.C.
20555 NRC DOCKET NUMBERS 50-424 AND 50-425 OPERATING LICENSE NPF-61 CONSTRUCTION PERMIT NUMBER CPPR-109 V0GTLE ELECTRIC GENERATING PLANT - UNITS 1 AND 2 NUCLEAR SERVICE COOLING WATER SYSTEMS Gentlemen:
In response to your request, we have made an expanded conservative evaluation of the nonfused consumable insert concern identified in the nuclear service cooling water (NSCW) piping system (Attachment 1).
These calculations are based on the current criteria available in the 1986 edition of ASME Section XI, IWB-3641. The final analysis supports the original conclusions and recommendations of the Evaluation of Nonfused Consumable Inserts in TP304L Stainless Steel Piping Systems, letter from Y. Chung to D. L. Kinnsch, August 1, 1986 (note: this letter is contained in Tab D of the enclosed report). This ind Mn? assessment was satisfactory based on the alternate criteria given in im M42. These complementary results provide further assurance of the fitness-for-service of the installation.
Because of the relatively low operating temperature (up to 115*F, or 150*F during shutdown) of NSCW water, the lack of fusion crevices are not expected to corrode such as to cause an increase in flaw depth. Nevertheless, we will perform a walkdcwn for visual observation of leakage. This walkdown will include accessible ASME code class 3 portions of the NSCW piping system at operational pressures during each refueling interval for the first ten years of service. This inspection will provide additional assurance in the leak-tight-integrity of the system.
Additionally, we will perform an ultrasonic examination (UT) of two representative welds which are in piping 24 inches in diameter, one in each unit, every 40 months for the first ten years of service. This volumetric method will confirm that the flaw has not increased in depth such as to cause
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8702190161 870209 PDR ADOCK 03000424 PDR p
pr U.S. Nuclear Regulatory Commission File: X7BC35 February 9,1987 Log:
GN-1345 Page 2 additional evaluations to be made. The baseline UT examination has been performed utilizing the procedure described in Attachment 2, resulting in an accuracy of approximately fif teen percent of the pipe wall thickness.
During the inspection intervals UT procedures with at least equivalent accuracy will be employed.
If you have any questions, please do not hesitate to contact me.
Sincerely, Q.h...',
J. A. Bailey Project Licensing Manager JAB /sm
-Enclosure xc:
J. P. O'Reilly R. E. Conway L. T. Gucwa R. A. Thomas J. E. Joiner, Esquire B. W. Churchill, Esquire M. A. Miller (2)
G. Bockhold, Jr.
NRC Regional Administrator NRC Resident Inspector B. Jones, Esquire D. Feig R. W. McManus Vogtle Project File 1031V f
l i
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ATTACHMENT 1 6
Bechtel National, Inc.
Engineers-Constructors Fif ty Beale Street San Francisco. California MadAddress Po Bas 336s sanFranc6co CA94t19 To:
D. L. Kinnsch File No. YC-027-01
Subject:
Nonfused Consumable Inserts Date: February 6,1987 in TP 304L SS Piping Systems Vogtle Project From:
Y. Chung Bechtel Job No. 9510-008 Of:
R&D/ Materials and Quality Copies:
F. C. Breismeister/R. A. Manley Services Department D. Capito S. R. Garreffa At:
50/15/B5 Ext.
8-1489 B. D. Hackney R. F. Steigerwald 6
R. A. White DCC 0152157
References:
(1) Letter from Y. Chung to D. L. Kinnsch, August 1, 1986, YC-086-01 (Rev. 1)
(2) Letter from S. T. Cloyd, V-SANU to G. H. Freddy, B-PFE, V-SAMU-SE-19800, NSCW Systems - Maximum Stress Levels at Butt Welds on Large Bore Thin Wall Pipe, February 4, 1987 We reported the acceptability of nonfused consumable inserts up to one-half the insert height in Class 3 TP 304L austenitic stainless steel piping systems for the Vogtle Project (Reference 1).
IWD-3000 states that the flaw acceptance criteria for Class 3 "...is in the course of preparation" as of the 1986 edition of ASME Section XI.
In the meantime, "The rules of IWB-3000 (for Class 1) may be used" for Class 3.
IWB-3640, Evaluation Procedures and Acceptance Criteria for Austenitic Piping, provides two alternative flaw acceptance criteria: IWB-3641 or IWB-3642.
In Reference 1, we showed that the nonfusion flaw' condition can satisfy the margin of safety required for Class 1 in IWB-3642 and, therefore, is acceptable as-is.
Using schedule 10S pipewall thicknesses, the nonfusion flaw depth ratios were calculated to be 0.41 for pipe sizes 14, 16, and 18 inches, 0.36 for 20 and 22 inches, and 0.31 for 24 inches in diameter.
This has been found to be incorrect. The pipes are schedule 10 with a 0.250 inch wall thickness for pipe sizes from 14 to 24 inches in diameter. Therefore, the nonfusion flaw depth ratios are 0.31 of the pipewall thickness for all pipe sizes (14 through 24 inches).
Figure 1 shows the flaw assessment diagram in Reference 1 with some modification: Curve "5" has been added. Curve "5" is applicable to class 3 piping with the same margin of safety factor as for Class 1 piping.
nus
O D. L. Kinnsch From:
Y. Chung Page 2
Subject:
Nonfused Consumable Inserts February 6, 1987 in TP 304L SS Piping Systems Vogtle Project Bechtel Job No. 9510-008 Figure 1 shows that the allowable ratio of full circumferential part-through flaws to pipewall thickness is 0.40 for Class 1 piping without lowering the required margin of safety.
(This ratio should be 0.43 for Class 3 piping.)
This is the maximum flaw depth ratio allowable when the stresses are at design maximum. The actual nonfusion flaw condition represents a ratio of flaw to pipewall thickness of only 0.31, which is less than the allowable (0.40) without lowering the required margin of safety. Therefore, the nonfusion flaw 4
condition satisfies the IWB-3642 criteria. The allowable flaw depth ratios are greater than 0.40 for actual stresses because they are lower than design maximums. This is demonstrated below.
The alternative acceptance criteria, IWB-3641, are shown below. The definitions of the symbols come f rom IWB-3641.2. These criteria provide the maximum allowable flaw depth ratios for a given stress level rather than for the design maximums.
IWB-3641.3 Acceptance Criteria.*' Piping containing a flaw exceeding the allowable flaw standards of IWB-3514.3 is acceptable for continued service until the end.of the evaluation period if the following criteria are satisfied:
(a) For circumferential flaws (1) af less than an (Table IWB-3641-1 or Table IWB-3641-5) and (2) af less than ao (Table IWB-3641-2 or Table IWB-3641-6) r ag =
the maximum depth to which the detected flaw is calculated to grow at the end of the evaluation period Eg=
the maximum length to which the detected flaw is calculated to grow at the end of the evaluation period the maximum allowable flaw depth corresponding a =
n to flaw length Eg for normal operating (including upset and test) conditions the maximum allowable flaw depth corresponding a =
o to the flaw length Eg for postulated emergency and faulted conditions Tables IWB-3641-1 and IWB-3641-2 for gas tungsten-arc (GTAW) welds are applicable in this case. These tables are reproduced in Attachment I.
l
- 1986 ASME Boiler and Pressure Vessel Code,Section XI Rules for Inservice l
Inspection of Nuclear Power Plant Components
-v,.--y--w w--,--y
_-,-m.-,.-,-,,w
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--m m,
T'o D. L. Kinnsch From:
Y. Chung Pege 3
Subject:
Nonfused Consumable Inserts February 6, 1987 in TP 304L SS Piping Sy eems Vogtle Project Bechtel Job No. 9510-008 We concluded in Reference 1 that the nonfusion flaws will not grow due to fatigue
- or stress corrosion cracking. Therefore, af is the same as the initial flaw depth, namely 0.31 of the pipewall thickness. The last column in Table IWB-3641-1 shows that the allowable end-of-evaluation period flaw depth-to-thickness ratio is 0.41 when (Pm + P )/S is 1.0.
This is b
m applicable to flaws which are fully circumferential. Likewise, Table IWB-3641-2 shows that the allowable end-of-evaluation period flaw depth-to-thickness r& io for the full pipe circumference is 0.40 when (Pm + P )/S b
m is 1.8.
For stress ratios lower than 1.0 in Table IWB-3641-1 or 1.8 in Table IWB-3641-2, the allowable flaw depth-to-thickness ratios are higher than 0.40 or 0.41, respectively.
Table 1 shows maximum stress values at the butt welds of the Class 3 Type 304L stainless steel schedule 10 piping for each pipe size from 14 to 24 inches in diameter (Reference 2).
These values are specific to the Vogtle plant. The stresses under columns "Eq. 8 and Eq. 9(B)" are lower than S ** and those h
under column "Eq. 9(D)" are lower than 1.8 S. Therefore, the allowable h
flaw depth ratios should be greater than 0.40 as compared with 0.31 actual.
The allowable flaw depth ratios for the full pipe circumference corresponding to the maximum stress values have been calculated using Tables IWB-3641-1 and IWB-3641-2. The results are included in Table 1.
The maximum allowable flaw depth ratios are 0.41 to 0.63 under normal operating conditions and 0.44 to 0.55 under faulted conditions.
(No emergency loading conditions have been identified to these piping systems.) The nonfusion flaws, which are only 0.31 of the pipewall thicknesses, are lower than the above maximum allowable flaw depth ratios. Therefore, the IWB-3641 criteria are satisfied. These allowable flaw depth ratios specific to Vogtle are plotted in Figure 1.
These ratios can be compared with the nonfusion flaw depth ratio, which is lower thc.n the allowables.
The above analysis reinforces the conclusions, and recommendations remain the same as in Reference 1: The nonfusion condition is acceptable as-is for the life of the plant.
Le s
. Chung YC Attachments
- da/dN for stainless steels are much lower than the rate used in Reference 1.
See for example, Transactions of the ASME, Journal of Pressure Vessel Technology, Vol. 108, August 1986, p. 364.
- S : basic material allowable stress at design temperature, psi (ND-3652).
h
r'.i TABLE 1 Maximum Stress Values for Class 3 Stainless Steel Piping Systems and Allowable Full Circumferential Flaw Depth-to-Thickness Ratios Pipe Eq. 8 (Normal) (1)
Eq. 9(B) (Upset) (1)
Eq. 9(D) (Faulted) (1)
Size Max. Stress Flaw Depth Max. Stress Flaw Depth Max. Stress Flaw Depth inch ksi Ratios (2) ksi Ratios (2) ksi Ratios (3) 14 14.3 a = 0.46 15.5 a = 0.41 25.1 a = 0.46 n
n o
16 14.3 0.46 15.5 0.41 26.2 0.44 18 11.5 0.56 15.5 0.41 20.8 0.53 20 8.9 0.63 14.4 0.46 18.6 0.55 22 6.1 0.63 15.5 0.41 20.5 0.54 24 11.5 0.56 14.9 0.44 26.2 0.44 (1) Per ASME Section III, ND-3652 (2) Per ASME Section XI, Table IWB-3641-1 (3) Per ASME Section XI, Table IWB-3641-2 IWB-3641.3 Acceptance Criteria (based on flaw depth ratios): ag < an n
and a af = 0.31 (end-of-evaluation flaw depth-to-thickness ratio)
= see the values in the above table.
a,ao n
I 1
i
]
Nominst str;;ss in tha uncracked section of pipe d k Pm + Pb
- =,,
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i h
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+
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$ >s _ _ _ _ _ _kl N
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=
i h og = Flow stress
-+]H P Neutral axis m
Circumferential surface flaw geometry and assumed plastic collapse stress distribution 65' 147' 360*(=2a)
\\
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k
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i s
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\\
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(collacse kne)
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- 2) P.. P3 = 1.5.s, s
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' " " = = = - - - - -
0.75 y
's,'
(5) v g
Pa+Pb
- 2 77'Sh Class 3 g
n n = 0.63 a
s
$ 0.6 MI6 (3) p + p. - 2 m s_
(safety Factor = 2.773)
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O ao = 0.55
!iff#)
Lanearll
- = = = " "
0.43
=
.: approximaton i:
n an = 0.41 o 0.4
-+
ter aiio-aeie ::
i:..
4,4o e
! **. *A':i
!!1ii.
if!f!f j!!j[ag = 0.31 o
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iils E!s
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E O
O O.2 0.4 0.6 0.8 1.0 Fraction of Circumference (a/n)
Figure 1 A flaw assessment diagram for TP 304/304L stainless steel pipe with circumferential flaws. Curves "1",
"2",
and "3" are for Class 1 piping and "5" for Class 3 piping with the same margin of safety factor af (X) is the nonfusion flaw depth ratio at the end of evaluation period; an (0,A) and ao (e) are flaw depth ratio allowables for the full pipe circumference from Table 1.
I (The above figure is a modification of Figures 3 and 4 in
" Acceptance Criteria for Circumferential Flaws in Stainless Steel Piping, by D. M. Norris, et al., in ASSE PVP-Vol. 58,
)
Aspect of Fracture Mechanics in Pressure Vessels and Piping, pp.185-200, ASSE,1982)
o Attachment I YC-027-01 TABLE IWB-3641-1 ALLOWABLE END-OF-EVALUATION PERIOD FLAW DEPTH 1 TO THICKNESS RATIO FOR CIRCUMFERENTIAL FLAWS - NORMAL OPERATING (INCLUDING UPSET AND TEST Ratio of Flaw Length, t,, to Pipe Circumference [ Note O)]
P. + P, 0.5 S.
(Note (2)]
0.0 0.1 0.2 03 0.4 or Greater 1.5 (4)
(4)
(4)
(4)
(4)
(4) 1.4
~ 0.75 0.40 0.21 0.15 (4)
(4) 1.3 0.75 0.75 0.39 0.27 0.22 0.19 1.2 0.75 0.75 0.56 0.40 0.32 0.27 1.1 0.75 0.75 0.73 0.51 0.42 0.34 II.0 0.75 0.75 0.75 0.63 0.51 0.41 l 0.9 0.75 0.75 0.75 0.73 0.59 0.47 0.8 0.75 0.75 0.75 0.75 0.68 0.53 0.7 0.75 0.75 0.75 0.75 0.75 0.58 s 0.6 0.75 0.75 0.75 0.75 0.75 0.63 NOTES:
(1) Flaw depth = a,for a surface flaw 2a,for a subsurface flaw t = nominal thickness Linear interpolation is permissible.
(2) P. = primary longitudinal membrane stress (P. s 0.5 S.)
P,= primary bending stress S. = allowable design stress intensity (in accordance with Section III)
(3) crcumference based on nominal pipe diameter.
(4) !WB-3514.3 shall be used.
TABLE IWB-3641-2 ALLOWABLE END-0F-EVALUATION PERIOD FLAW DEPTH 2 TO THICKNESS RATIO FOR CIRCUMFERENTIAL FLAWS -
EMERGENCY AND FAULTED CONDITIONS P. + P, Ratio of Flaw Length, I,, to Pipe C3%..'..w [ Note O)]
[ Note (2)]
0.0 0.1 0.2 0.3 0.4 0.5 0.75 1.0 3.0 (4)
(4)
(4)
(4)
(4)
(4)
(4)
(4) l 2.8 0.75 0.46 0.24 0.17 0.13 (4)
(4)
(4) 2.6 0.75 0.75 0.39 0.27 0.22 0.19 0.17 0.17 2.4 0.75 0.75 0.54 0.38 0.30 0.26 0.24 0.24 2.2 0.75 0.75 0.68 0.48 0.38 0.33 0.30 0.29 2.0 0.75 0.75 0.75 0.58 0.46 0.40 0.35 0.35 l 1.8 0.75 0.75 0.75 0.67 0.54 0.47 0.41 0.40 l 1.6 0.75 0.75 0.75 0.75 0.62 0.53 0.46 0.46 s 1.2 0.75 0.75 0.75
~
0.75 0.69 0.60 0.51 0.51 1.4 0.75 0.75 0.75 0.75 0.75 0.66 0.56 0.55 NOTES:
(1) Flaw depth = a,for a surface flaw 2a for a subsurface flaw t = nominalthickness Linear interpolation is permissible.
(2) P. = primary longitudinal membrane stress (P. s 1.0 S.)
P,= primary bending stress. The sum (P. + P,) shall not exceed 25,, where 5,is the Section 111 specified minimum yielo stress.
l S. = allowable design stress intensity (in accordance with Section III)
(3) Crcumference based on nominal pipe diameter.
(4) IWB-3514.3 shall be used.
Discussion of UT Inspections of Pipe Welds The technique employed to measure through-wall dimension of flaws on thin wall stainless steel piping is a combination of a variation of an approved VEGP procedure, UT-V-407, and EPRI guidelines generally developed for sizing of IGSCC.
Initial detection of areas of interest is accomplished using a 0.25",
5.0 MHZ, 60* shear wave with a modified shoe. Subsequently these areas are further investigated using a dual eleient, 5.0 MHZ, 70* refracted longitudinal wave search unit, calibrated in depth of remaining wall and employing a flaw-tip diffraction method. Calibration is accomplished using a series of 1/32" side d:111ed holes located at depths of 0.1",
0.2",
0.3", 0.4" and 0.5".
Further refinement of the calibration is done on a series of electrical discharge machined (EDM) notches at depths of 0.08" to 0.5".
Qualification was accomplished on a spool sample fabricated to exhibit conditions as are present in the field. A series of notches placed in the spool sample were successfully sized to within 15% of measured through-wall depth.
Limitations This technique is limited in two aspects which are not a concern for this application. Due to the focal length of the search unit, measurements on material thicknesses less than 0.250 inches will result in less accuracy of readings (the pipe wall thickness in this case is nominally 0.250 inches).
In addition, flaws exhibiting a through-wall dimension in excess of 85% of the wall thickness will be difficult to accurately measure. However, it would be evident that the through-wall depth exceeds allowable values.
Preliminary Results of Weld Examination Unit 1 The 24 inch pipe weld has approximately 25 inches (of about 75 inches total circumference) of indication area. The 70*F results indicate four areas of measurable depth. Readings were:
0.020, 0.050, 0.035 and 0.045.
The total length of these indications are approximately 4.6 inches.
Unit 2 The 24 inch pipe weld has approximately 53 inches (of about 75 inches total circumference) of indication area. The 70*F results indicate three areas of measurable depth. Readings were:
0.040, 0.020 and 0.025.
The total length of these indications are approximately 2.75 inches (note: one area of interest, about fifteen inches long, showed no measurable through-wall flaw dimension).
3031V