View source for L-30-100, Rev 2 to Design Rept for Recirculation Sys Weld Overlay Repairs & Flaw Analysis at Brunswick Steam Electric Plant Unit 1

{{Adams
| number = ML20132D484
| issue date = 09/30/1985
| title = Rev 2 to Design Rept for Recirculation Sys Weld Overlay Repairs & Flaw Analysis at Brunswick Steam Electric Plant Unit 1
| author name = Gustin H, Kleinsmith M, Wenner T
| author affiliation = NUTECH ENGINEERS, INC.
| addressee name = 
| addressee affiliation = 
| docket = 05000325
| license number = 
| contact person = 
| document report number = CPL-30-100, CPL-30-100-R02, CPL-30-100-R2, NUDOCS 8509300186
| package number = ML20132D476
| document type = GENERAL EXTERNAL TECHNICAL REPORTS, TEXT-SAFETY REPORT
| page count = 34
}}

=Text=
{{#Wiki_filter:_ -          .      .
NUTECH   -
CONTROLLED CPL-30-100 Revision 2 September 1985 CPLO30.0100 DESIGN REPORT FOR RECIRCULATION SYSTEM WELD OVERLAY REPAIRS AND FLAW ANALYSIS AT BRUNSWICK STEAM ELECTRIC PLANT UNIT l c
Prepared fort Carolina Power and Light Company Prepared by:
NUTECH, Inc.
San Jose, California ll Prepared by:                            Reviewed by:
C, hau, v M. E. Kleinsmith                        H. L. Gustin, P.E.
Consultant I                            Project Engineer Approved by:                            Issued by:
9 A-   -   p                                  [
T. J. Wenner,   P.E.                    D. K. dshida,P.E.
Engineering Manager                     Project Manager Date       ifill85 8509300186 850925 PDR  ADOCK 05000325 P                  PDR

        ~
REVISION CONTROL SHEET                                                   .
TITLE: Design Report for                     DOCUMENT FILE NUMBER:     CPLO30.0100 Recirculation S' stem y        Weld Overlay Repairs and Flaw Analysis at Brunswick Steam Electric Plant Unit 1 H. L. Gustin, P.E./ Project Engineer N AME / TITLE                                      INITI ALS M. E. Kleinsmith/ Consultant I N AME/ TITLE fr rf iNITI'A LS N. G. Cofie/ Senior Consultant                                         A/ dd.
N AME / T'TLE                                     INITI A LS N AME / TITLE                                     INITI ALS AFFECTED    DOC      PAEPAAE0       ACCUAACY          CRITE RI A R4 PAGEtS     AEV      BY ?OATE    CHECK SYlOATE CHECK 8Y / DATE i-vi          0   Nd %YdF            ^/4c </r/sf    gf4 9/3/yf         Initial Issue 1-28          0   @ct "/MJ          ucc 9/5/sr ///d T[3/'I 23          1   Sd 9/ich7         pp $/../d              Tf<0,ft? Added NOTE, revised nek g/nr                                              "
8,17         2                      ,;C c Slo /rf  M 9/11/6f      'A ed R erence 9, 20,28         2    ncW VM/8f        use. 9/o/ts      g $[g[gf       revised stresses and crack growth prediction 11      vi PAGE          OF li a . ; t .1 A EV .1

CERTIFICATION BY REGISTERED PROFESSIONAL ENGINEER I hereby certify that this document and the calculations con-tained herein were prepared under my direct supervision, or reviewed by me,            and to the best of my knowledge are corr'ect and complete.             I ~further certify that, to the best of my knowledge design margins required by the original Code of Construction have not been reduced as a result of the repairs addressed herein.             I am a duly Registered Professional Engi-neer under the laws of the State of North Carolina and am competent to review this document.
                         .iiin ,e,,,,
                  /' W C ARO[' #*,                      Certified by:
                 /S(Q*Gi?J,./ ,',,
f    [      SEAL       I i i          12504     I!
H. L. Gustin,  P.E.
Registered Professional Engineer State of North Carolina Ragistration No. 12504 CPL-30-100                                     111                              .
Revision 2 nutggh

                                                                                       . . . _ , .   .        =_ .                    .
TABLE'OF CONTENTS Page                            ;
LIST OF TABLES                                                                       V LIST OF FIGURES                                                                    vi 1
                        .l .0   INTRODUCTION 2.0   REPAIR DESCRIPTION                                                             7 3.0    EVALUATION CRITERIA                                                          13 3.1       Weld Overlay Repair Criteria                                       13 3.2        Flawed Pipe Analysis Criteria                                     14 4.0    LOADS                                                                        15 4.1       Mechanical, Internal Pressure, and Thermal Loads                                                      15 4.2       Weld Overlay Shrinkage - Induced Loads                             15 5.0    EVALUATION METHODS AND RESULTS                                               18 5.1        Code Evaluation - Section XI                                     18 5.2         Fracture Mechanics Evaluation                                   19 5.3       Overlay Shrinkage Effect on Recirculation System                    .
20 5.4         Low Material Toughness Concerns                                 21 6.0     

==SUMMARY==
AND CONCLUSION                                                      25

==7.0     REFERENCES==
27
.I I
CPL-30-100                                            iv                                                      .
Revision 2 l

t i,
LIST OF TABLES Table                                                                                         ' Title                                                                                   Pace t
1.1                             Brunswick Unit 1 Flaw Disposition                                                                                                                                     2 l
)
h j                            2.1                             Weld overlay As-Built Dimensions                                                                                                                                       9             ,
l 1
4 4.1                              Summary of Total Stresses                                                                                                                                        17                 :
,                                                                                                                                                                                                                                                 i l                            5.1                              Summary of Shrinkage Stresses at Recirculation                                                                                                                                      i i                                                             System Flaw Locations                                                                                                                                            23                 -
;                                                                                                                                                                                                                                                 i 1
i 4
1
'l i
i 9
2 1
1 T
 .I 1
I i
1 d
i
!                             CPL-30-100                                                                                                 v                                                                                                    . ,
Revision 2
   --*--,ww+=w        y    ,  v    ,      ym,,-www,,,,,<-.                r-----,---y_-..,-,c-             y-%.w,,.w_.,- m omm, g i ,   -,% m. , m,      %--- o w n. i,w s , .w y,-w w - y ,                        -,..ww,wree-&.,-,.g..e

1                                                                                                                                                                                      -
LIST OF FIGURES Figure                                                           Title                                              Page i
i                                 1.1         Conceptual Drawing of Recircu'lation System                                                                         5 1.2         Weld Overlay Dimension Definition                                                                                   6
  !                                 2.1         Configuration of Safe End-to-Pipe Weld Overlay                                                                    10 2.2         Configuration of 12" Elbow-to-Pipe Weld Overlay                                                                   11 i                                               .
 ]                                  2.3         Configuration of 28" Elbow-to-Pipe Weld Overlay                                                                   12 4
S.1         Brunswick Unit 1 Recirculation System Piping Model                                                                24 I
I 1
f.:
1 i
l
  +
i t
i i
4 CPL-30-100                                                                vi                                                                       ,
                                    ' Revision 2 f
tr-,- - . .-   y,+. w - -      ,,-%r 3e--   y- g--,mw-.,- - , , ,           .    -..--...m._     --..,-3   ,.,----,,w.mw.v-.-,        we . , , ,,      ~,=-e-   g-ww ..- - . - -g-,-

     .-                  . ~. -.   .--  -  - _ _ - -       .     --            ,    . ..

==1.0       INTRODUCTION==

This report summarizes analyses performed by NUTECH to evaluate flaw indications and weld overlay repairs in l
the Recirculation System at Carolina Power and Light Company's Brunswick Steam Electric Plant Unit 1 (Brunswick 1). The flaw indications addressed in this report were detected during the summer 1985 refueling i                      outage inspection.
Flaw indications were identified adjacent to 23 welds in the Recirculation System. One flaw indication detected by ultrasonic (UT) examination was determined to be ac-ceptable without repair for at least the next 18 months. The remaining flaw indications were repaired by I
application of weld overlay. The purpose of each over-
;                       lay is to arrest any further propagation of intergranu-lar stress corrosion cracking (IGSCC), and to restore original design saf ety margins to the weld. All flaws are in Type 304 stainless steel material. Figure 1.1            l shows the location of these flaw indications.      Table 1.1 contains a description of each flaw indication an'd the disposition of each.
r CPL-30-100                             1                                   .
Revision 2

r Table 1.1 BRUNSWICK UNIT 1 FLAW DISPOSITION overlay Desion (in.)f Tmin/No.                                             Pipe a                                                      L2             -Size Weld No.                 Flaw                    of Layers L1 A8            Circumferential                N/A                    N/A           N/A             28"                                      '
2.25"x25%,
upstream 12-AR-A2         Axial, 0.4",                   2 layers               1.5           1.5             12"                                      -
upstream D
$               12-AR-A3          Circumferential,              0.250"                 1.5           1.5             12" 1.75"x35%,
i                                 upstream                                                                    ,
12-AR-B3          Axial, 0.5",                   2 layers              1.5           1.5             12" downstream i
12-AR-C2          Circumferential,               0.260"                1.5           1.5             12" 0.6"x50%,
downstream 12-AR-C3          Axial, 0.4",                   2 layers              1.5           1.5              12" downstream i               12-AR-D2          Axial, 0.60",                  2 layers              1.5            1.5             12" I                                 upstream D 12-AR-D3         -Axial,0.3f5",                  2 layers              1.5            1.5             12"
;                                 downstream i               12-AR-D4          Circumferential,              0.220"                1.5            0.625           12"
'                                  2.0"x35%,
i                                  upstream i
12-AR-E3          Axial, 0.4",                   2 layers              1.5           1.5             12"
'                                  downstream 12-BR-F2         Axial,0.7g",                   2 layers              1.5           1.5             12" downstream 12-BR-G2        Circumferential,               0.220"                1.5           1.5             12" 1.125"x25%,
upstream l
l 4
CP L- 30-100                                                      2                                                                    ^.!
Revision 2 1

Table 1.1 BRUNSWICK UNIT 1 FLAW DISPOSITION (continued)
Overlay Design (in.)f Tmin/No.                  Pipe a        of Layers L1        L2    Size Weld No.          Flaw 12-BR-G3    Axial, O g8"        2 layers   1.5      1.5   12" upstream 12-BR-G4    Axial, 0.5",        2 layers   1.5      0.60  12" b
upstream 12-BR-H2    Axial, 0.4",        2 layers   1.5      1.5   12" D
downstream 12-BR-H3    Axial, O g 5",      2 layers   1.5       1.5  12" upstream f
12-BR-J2    Axial, O g6"        2 layers   1.5       1.5  12" upstream 12-BR-J3   Circumferential,    0.230"     1.5       1.5  12" 4"x60%,
downstream 12-BR-K2   Axial C              2 layers   1.5      1.5  12" 12-BR-K3   Axial,Oj75"          2 layers   1.5      1.5  12" upstream 12-BR-K4   Axial, O g4"         2 layers   1.5      0.55  12" upstream 28-A4      Axial, O 6",         2 layers   1.6      1.6   28" upstream d 28-B4       Axial, 0.6"         2 layers   1.5      1.5   28" x25%, upstream
* CPL-30-100                             3
,        Revision 2                                               g

i Table 1.1 BRUNSWICK UNIT 1 FLAW DISPOSITION (continued) a Flaw size used in designing overlay b  Flaw depth assumed 100%
c  Leaking flaw undetected by UT, flaw assumed axial .7"x100%
d Circumferential flaws present did not require overlay; flaw depth assumed 100%
* Circumferential flaws present did not require overlay f
See Figure 1.2 for definition of weld overlay dimensions CPL-30-100                          -4                              .
Revision.2 nutagh

K-4 gQ                                                                         H3     J2      - J-3   -K3 k                                  G4                                 K 2 b O,
                                                                                                                   ,f Ei     !4 E3 e
CD     l e
B3 A-2 F 2>  /
O   i q
n'n w-2 P
4        %                                             %
[-       -
                                                    ' D-2             I                 ''
D1                                                   04        %
4                                              ( en dg un                                                                                              pq L OOP 8                    f 1
A8                                p1 90       V F CPL 83.08-17 LOOP A i
l C                                                         rier.1.1 CONCEPTUAL DRAWING OF RECIRCULATION SYSTEM h                                                                                                                         $

e L1               L2 PIPE WALL
                 \^        A%\%\%%\%\\%\%%\\                                    T min V///////////////////////////h'/////////////////////////////b PIPE SIDE                     ELBOW, VALVE, OR SAFE END SIDE
(
PATENT ADPLIED FOR Figure 1.2 WELD OVERLAY DIMENSION DEFINITION CPL-30-100                                   6                                       .
Revision 2 nutggh

2.0      REPAIR DESCRIPTION The UT flaw indications requiring repair were remedied 4
by establishing additional " cast-in-place" pipe wall thickness with weld metal deposited 360 degrees around and to either side of the existing weld, as shown in Figures 2.1 through 2.3.                                    The weld-deposited band over the cracks provides, as a minimum, wall thickness equal to that required to meet the requirements of Reference                                                                                            ,
1, as modified by Reference 2.                                      NRC Generic Letter 84-11 (Reference 2) requires that the first weld overlay layer not be included in the design thickness.                                                                   A favorable compressive residual stress distribution results from overlay application, which will tend to inhibit further.
crack initiation or growth.                                       The deposited weld metal is type 308L, which is resistant to IGSCC propagation.
Table 2.1 presents design and as-built inf ormation for the overlay repairs applied to Brunswick 1.
All weld overlay repairs were inspected using non-destructive examination.                                    Non-destructive examination of the weld overlays consisted of the following:
I
 !                             1)                Surface examination of the first weld overlay layer by the liquid penetrant examination technique in i                                                accordance with ASME Section XI (Reference'l).
i CPL-30-100                                                             7                                                                                ~,
Revision 2
_ . = - - - ,     , -.        . . - , . . _ .              , _ - _ _ . _ , . . _ , _ . _         - . . _ - . _ _ . _ . _ , _ . . _ . ,       -  - _ _ _ . . . . - - - -

                 . .                         ._        __    __ _               -       .                   . _.. .__.          _ _ . _. m _ _ . _ .
i L                                                                                                                                                                    ,
4
: 2)        Delta ferrite measurement of the first layer, using a Severn gauge.
: 3)        Surface examination of the completed weld overlay by the liquid penetrant examination technique in accordance with ASME Section XI (Reference 1).
4
: 4)        Volumetric' examination of the completed weld over-l                                                                                                                                                                      '
lay by the ultrasonic examination technique in accordance with ASME Section XI (Reference 1).
l                                                         5)        Volumetric examination of the weld overlay.to pipe                                                 I
                                                                                                               ~
bond and existing circumferential pipe weld by the ultrasonic examination technique in accordance with i
l                                                                   recommendations outlined in the EPRI interim report                                         %
dated April 1985, " Examination of Weld Overlayed l                                                                   Pipe Joints" (Reference 9).
i
 ?
I i                                               CPL-30-100                                                                    8                                      .
Revision 2

I                                                                                                  Table 2.1 l
WELD OVERLAY AS-BUILT DIMENSIONS i
j                                                                                              Design Tmin/                         As-Built        As-Built               {
l                                Weld I.D.               Pipe Size                             No. of Layers                        Thickness        Lencth 1,
1 12-AR-A2                      12                                      2 layers                       0.303           3.453 l                                12-AR-A3                      12                                      0.250                          0.419           3.188 i
j                                12-AR-B3                      12                                      2 layers                       0.398           3.43 1
i                                12-AR-C2                      12-                                     0.260                          0.435           3.640 l                               12-AR-C3                      12                                      2 layers                       0.435          .3.037 12-AR-D2                      12                                      2 layers                       0.296           3.170                6
]                                12-AR-D3                      12                                      2 layers                       0.317           3.075 i
 !                               12-AR-D4                      12                                      0.220                          0.404           2.225                i 12-AR-E3                      12                                      2 layers                       0.373           3.064 12-BR-F2                      12                                      2 layers                       0.328           3.453 i                                12-BR-G2                      12                                      0.220                          0.418           3.288 i
j                                12-BR-G3                      12                                       2 la'yers                     0.468           3.050 i
j                                12-B R-G4                     12                                       2 layers                      0.205           2.923 l-j                                 12-BR-H2                     12                                       2 layers                      0.280           3.482                ,
e                                                                                                                                                                          '
12-BR-H3                     12                                       2 layers                      0.465           3.175
{                                 12-BR-J2                     12                                       2 layers                      0.290           3.101 f                                 12-BR-J3                     12                                       0.230                         0.447           3.115 12-BR-K2                     12                                       2 layers                      0.410            3.110 f
12-BR-K3                     12                                       2 layers                      0.320            3.250 j                                 12-BR-K4                     12                                        2 layers                     0.213            2.425               {
28-A4                        28                                        2 layers                     0.140            3.525 i
l                                 28-B4                         28                                       2 layers                     0.163            3.72 l
* Exclusive of first layer thickness
{                                                                                                                                                                           !
j                                                                                                                                                                      .,
I                                 CPL-30-100                                                                                    9 Revision 2 i                                                                                                                                                                           1 f , _ __._, _ . _ . _ ,.-. _                                    , _ _ _ _ _ . _ , . _ _ _ _ _ _ . _ . _ _ _ _ . - . _ _ _ _ _ _

I I
NO AS WELDED SURFACE N o ACCEPTABLE FOR OVERLAY                                                                                                 L O [ TAPER TRANSIIlONS                       1.5"        c 12) e-                                                     SAFE-END o
m
                                           ~
TYPE 30GL if WELD OVERLAY
                                       //////////Mfffkk
                                    // / /                  G\\ \\\ 47 s          - 0.57"              f v^-                        '                                                     $
46' NOMINAL (TYP)
H          4              2 PLACES o
l      _                  _
i    I      _
12", 0.57" WALL                          12", 0.57" WALL    SAFE-END TO 304 SS PIPE                             304 SS PtPE         " PUP"-PIECE WELD
                                                                                 " PUP" PIECE TO       SAFE END TO PIPE WELD             NOZZLE WELD (1) MINIMUM THICKNESS VARIES, BUT DOES NOT
      $                                          INCLUDE FIRST LAYER THICKNESS                                     PATENT APPLIED FOR (2) DIMENSION VARIES DEPENDENT UPON EXTENT OF INCONEL Figure 2.1 CONFIGURATION OF SAFE END-TO-PIPE WELD OVEHLAY

_. -                           _                   -_                         --        _-        -    _=.
e l
es* MAXIMUM /
TYM 300L WELD CVERLAY a
1.5 MIN -
                                                    /                                          12", QJ7" THICK WALL, 304 SE PtPE (1) -            l
                                                        \
THROUGH WALL CRACK (ASSUMED)           8 s.o MIN      .t                  , -
7 p N
h It N
                                                                               \
As wELoEo SURFACE tcNo ACCEPTA8LE FOR RACIUS QVERLAY TAMR ELSCW TRANSITICNS (1) MINIMUM THICKNESS VARIES, BUT 00ES NOT                                       FCP M INCLUDE FIRST LAYER THICKNESS Figure 2.2 CONFIGURATION OF 12" EL8OW -TO -PIPE WELD OVERLAY PATENT APPLIED POA CPL-30-100                                           11
                                                                                                                 ~
Revision 2

                            . _ - m . _   .               . _ _ _ . _ _ _ _ __.1.
e l
488 MAXIMUM #
TYPE XISL WELD OVERLAY 1.5 MIN =
              ,b       d                                                                        28",1.09" THICK WALL,M4 $$ PtPE (1) e       1 k      AXIAL INDICATION 100% (ASSUMED) 3.0 MIN       =                    .
                                                                                                 ''PE TO ELSCW WELO I
o l
AS #ELDEQ SURFACE ACCEPTA8LE FCR CVERLAY TAPER                                                                   ,
TRANSITICNS LCNG RAciuS
;                                                                                           stscw 1
(1) MINIMUM THICKNESS OF 2 LAYERS DOES
  ,                NOT INCLUCE FIRST LAYER                                                             PCPL83.0644 Figure 2.3 CONFIGURATION OF 28" ELBOW -TO -PIPE WELD OVERLAY PArswr AppuEn Pon CPL-30-100                                        12 Revision 2                                                                                                     -*
nutagh

3.0         EVALUATION CRITERIA This section describes the criteria that are applied in this report to evaluate the acceptability of the weld overlay repairs and flawed pipe analysis. A Section III stress evaluation was not performed as part of.this analysis since the Section XI evaluations inherently satisfy Section III requirements.
3.1        Weld Overlay Repair Criteria Due to the nature of these repairs, the geometric configu-ration is not directly covered by Section III of the ASME Boiler and Pressure Vessel Code, which is intended for new construction. However, materials, fabrication procedures, and Quality Assurance requirements meet applicable sections of the original construction code. In addition, since con-ditions conducive to IGSCC led to the need for repairs, IGSCC-resistant materials have been selected for the weld overlay repairs.
A conservative method was used to demonstrate the adequacy of weld overlay repairs. All relevant UT indications were assumed to be through-wall for their measured length. The weld overlays were then designed such that the net section CPL-30-100                           13                                  ~.
Revision 2

limit load requirements of Reference 1 were satisfied, in addition to the requirements of Reference 2.
3.2          Flawed Pipe Analysis Criteria Weld 28-A8 contained a circumferential' flaw determined to be 2.25" long with a depth of 20%.                Due to its small initial length, the end-of-cycle allowable flaw depth defined in Table IWB-3641-1 of ASME Section XI (Refer-ence 1) is 75% of the pipe wall thickness.. The NRC's Generic Letter 84-11 (Reference 2) modifies this depth by a factor of 2/3.       The end-of-cycle allowable flaw depth is defined to be 50% of the pipe wall thickness, for the purpose of this analysis.
The upcoming cycle length is 18 months.                Therefore the flaw must be shown to be acceptable without repair for at least the next 18 months, utilizing the crack growth law presented :in Section 5.2.
i i
i a
CPL-30-100                                  14                                          ,
Revision 2

o
  ..                                                                              i 4.0       LOADS The loads considered in the evaluation of UT flaw indi-cations included. mechanical loads, internal pressure loads, dif ferential thermal expansion loads, and weld overlay-induced shrinkage loads. Mechanical and inter-nal pressure loads are used in designing weld overlays and are described in'Section 4.1. Differential thermal and- overlay shrinkage-induced loads are -included for crack growth predictions. The weld overlay shrinkage-induced loads are explained in'Section 4.2.
4.1       Mechanical, Internal Pressure, and Thermal Loads Internal pressure information for the Recirculation Sys-tem was obtainedifrom Reference 3. Deadweight, thermal and seismic loads applied to the Recirculation System welds were obtained from Reference 4. Calculated stresses are included in Table 4.1.
4.2       Weld Overlay Shrinkage - Induced Loads Weld overlays cause a small amount of axial shrinkage beneath the overlay. The resulting loads are manifested as bending stresses in the remainder of the piping sys-tem. Shrinkage loads in the Recirculation System were 4
CPL-30-100                           15                                -~
Revision 2 nutagh

calculated using a PISTAR (Reference 5) piping model, weld overlay shrinkage is discussed further in section 5.3.
g 's
                                        't l
l CPL-30-100                          16                            -\
Revision 2 nutgch   !
* t Table 4.1.

==SUMMARY==
OF TOTAL STRESSES Maximum Stress (PSI)           Total Stress (PSI)
Deadwe ight +  Crack        Wol Weld No.        Thermal      Seismic      Pressure    Growth    Design 28-A8             2358         1141            7346     9704        8487                       l 12-AR-A2             --          --
                                                        *14030    14030  '
14030 AR-A3          8960         2150            6343    15303        8493                       l AR-B3            --          --
                                                        *14030    14030     14030 12-AR-C2         6231         1463            6308    12539        7771'                      l 12-AR-C3            --          --
                                                        *14030    14030      14030 12-AR-D2            --          --
                                                        *12649    12649      12649 12-AR-D3            --          --          *14030    14030      14030               ,
4 12-AR-D4        10049         2722            6318    16367        9040 12-AR-E3            --          --
                                                        *12649    12649      12649 12-BR-F2            --          --
                                                        *12649    12649      12649 12-BR-G2         5608          738            6568    12176        7306                       l 12-BR-G3            --           --
                                                        *12649    12649      12649 12-BR-G4            --          --          *10768    10768      10768 12-BR-H2            --           --
                                                        *10696    10696      10696 12-BR-H3           :--           --
                                                        *14030    14030      14030 12-BR-J2            --           --
                                                        *12649    12649       12649 12-BR-J3         8769         1259            6339    15108        7598 12-BR-K2            --           --
                                                        *14030    14030       14030 12-BR-K3            --           --
                                                        *12649    12649      12649 12-BR-K4            --           --
                                                        *10768    10768       10768 28-A4                --          --
                                                        *12880    12880      12880 28-B4                --           --
                                                       '*13417    13417       13417 s
* Circumferential stress due to pressure only CPL-30-100                                 17                                                   -,
Revision 2 nutggb

5.0      EVALUATION METHODS AND RESULTS The flawed welds shown in Table 1.1 were identified by UT inspections during the summer 1985 refueling outage inspection at Brunswick Unit 1. These flawed welds were evaluated based upon the criteria of Section 3-to deter-mine whether an overlay was necessary to meet the re-quirements of Reference 1 and 2. Only one flawed weld (28-A8) was found to meet the' requirements of References l'and 2 without an overlay repair.
The application of weld overlays imposes a small amount of axial shrinkage at the weld location,which produces secondary stresses on the remainder of the piping sys-tem. The analysis made to determine the magnitude of this effect at each weld location and to address its sig~nificance is discussed in Section 5.3.
5.1      Code Evaluation - Section XI All weld overlays were designed assuming flaws were through-wall for their measured length. Welds contain-ing axial flaws only or axial flaws with very small          ,
circumferential flaws (as in welds 28-A4 and 28-B4) require only a leakage barrier. This leakage barrier consists of two layers of weld overlay material, with an CPL-30-100                           18                              .
                                                                            ~!
l Revision'2 nutagh

additional layer as required by Reference 2.         Circumfer-ential flaws in 12" pipe were overlay repaired in ac-cordance with Reference 1. All overlay designs restore the safety margins required in Section IWB-3640 of ASME Section XI (Reference 1).        The flaw in weld 28-A8 meets these requirements without repair and will not violate them for at least the next 18 months.
5.2         Fracture Mechanics Evaluation The allowable end-of-cycle flaw depth was determined from References 1 and 2.-       Calculation of crack growth                           '
due to IGSCC was based on Reference 6 and NUTECH's computer program NUTCRAK (Reference 7).        Input to NUTCRAK included the as-measured flaw depth, a con-servetive residual stress distribution, and the follow-ing conservative crack growth law.
3.59 x 10 -8 g 2.161              (Reference 3) hf =
Where da = differential crack depth (in) i dt =' differential time (hrs) .                                           f K = stress intensity at the crack tip (ksi Vin)
CPL-30-100                                 19
* i         Revision 2 O
c

Based on this conservative analysis, it was predicted that the flaw in weld 28-A8 would not exceed the end-of-cycle allowable crack depth for at least 22 months.               <[l 5.3        Overlay Shrinkage Effect on Recirculation System The effects of the radial shrinkage are limited to the region adjacent to and directly underneath the weld overlay. Based on Reference 8, the stress due to the radial shrinkage is less than the yield stress at dis-tances greater than about.four inches from either end of the overlay.
The effect of the axial weld shrinkage on the Recircula-tion System was evaluated with the NUTECH computer pro-gram PISTAR (Reference 5) using the piping model pre-sented in Figure 5.1. The' measured shrinkages due to all overlays applied this outage, as well as those due to previously applied overlays, were imposed as boundary conditions on this model. Since the ASME Code does not limit weld residual stress, all stress indices were set equal to 1.0.
The PISTAR program was used to elastically calculate stress due to weld shrinkage. The maximum calculated stress for an IGSCC susceptible weld was 18.1 ksi at l
CPL-30-100                             20                                          i Revision 2                                                                      ~l 1

3 e
nozzle weld N2D (weld 12-AR-D4).        This weld is a 12" safe-end-to-nozzle weld on a recirculation riser, and f                         was overlay-repaired. None of the stresses reported in i                        Table 5.1 take into account the increased membrane due l                         to overlay. Table 5.1 gives the ' shrinkage stress for all welds in the recirculation system found to have                         ;
j Since weld shrinkage-induced stresses are not flaws.
3
                                                                                                      ?
;                         limited by the ASME Code, the Code acceptability of i                        these welds is not in question.       It is judged that r
stresses of the-magnitude calculated will have negli-gible effect on the integrity or IGSCC susceptibility of these welds.
i 5.4        Low Toughness Material Concerns F
Recently, concerns have been raised that the toughness
]                                          .
of weld metal in stainless steel butt-welds deposited by
!                         flux shielded processes may be substantially lower than that of the surrounding metal. 'Potentially, this could i
lead to brittle failure of the butt weld material at an
~i applied load appreciably below the net section collapse l                          lead of the adjacent piping material.        As of the date of this report,-there is no formal regulatory or Code guid-
;                          ance on this issue.
i i
l 4
                                                                                                       )
.              CPL-30-100'                                 21                                      ^. l l               Revision 2                                                                             i l
j I

r                                                                                                                                        .
NUTECH reviewed the weld overlays and unrepaired flaw at Brunswick 1 to address this issue.                                   Most of the repaired flaws are oriented axially and are thus not affected by the toughness concern. -The weld overlay as-built thick-nesses of welds containing~circumferential flaws are large enough to adequately repair 360*x100% flaws, ex-cluding credit for the first overlay layer, as required by Reference 2.                Therefore, no credit for the butt weld material need be taken.                        Finally, the unrepaired. flaw in weld 28-A8 is very short'and shallow and is thus not of i
concern.
I 1
4 9
4
!                  CPL-30-100                                                 22
                                                                                                                                         -~
Revision 2 1
                          .     ......,m.-_._._       _,_     _
4 -      ,_,_....c-._.,       _, , ._, _ . . , , . - r -,- -

l                                                                                     .
Table 5.1

==SUMMARY==
OF SHRINKAGE STRESSES AT RECIRCULATION SYSTEM FLAW LOCATIONS Shrinkage Weld Number                     Overlay             Stress (PSI) 28-A8                                No                    176 12-AR-A2                          Yes                     1306 12-AR-A3                          Yes                     1410 4      12-AR-B3                          Yes                      557 I       12-AR-C2                          Yes                     1909 4
12-AR-C3                          Yes                     2651 12-AR-D2                          Yes                     6350 i-      12-AR-D3                          Yes                     4255 12-AR-D4'                         Yes                    18067 12-AR-E3                          Yes                     5422 12-BR-F2                          Yes                      743 12-BR-G2                          Yes                     3348
:       12-BR-G3                          Yes                     1230 12-BR-G4                          Yes                     8923 i       12-BR-H2                          Yes                      989 12-BR-H3                          Yes                     2248 12-BR-J2                          Yes                      633
 ;      12-BR-J3                          Yes                      812
;       12-BR-K2                          Yes                     2534 1
12-BR-K3                          Yes                     2216 12-BR-K4                           Yes                    1125 28-A4                             Yes                      195 28-B4                              Yes                     191 12-AR-A4*                          Yes                     879 12-AR-B2*                          Yes                     282
;       12-AR-84*                          Yes                     558 12-AR-E2*                           Yes                   3358 12-BR-F4*
* Yes                    1008 12-BR-H4*                          Yes                    6989 4       28-A14*                            Yes                     123 28-A15*                            Yes                     218 28-88*                              Yes                    189
* Overlay repaired during a previous outage NOTE:   Bypass loop weld 4A-10 was also overlay repaired. Its shrinkage will not affect the remainder of the system.                   ,
Shrinkage stress present at this weld is less than 100 psi.
CPL-30-100                                23
* Revision 2                                                                   .

HIGHEST STRESS LOCATION
                                                                                                   %m                   , .n
                                                                                                 ", %               f..                    g=
o ,,,,
p- -
                                                                                                   ''=
g-7                                                                           % -                 '     '
                                                                              /m fia                                           I.
v.
N      -    "
                                                                               ..                   n=,,
i=
9                                        .
                                                ==              ,
7 '"
                                                                                                                                                     .' a.
                                                                                                                                                                        =
                                          .'=           .                .                      s. ,,,
                                                                                 .                                              ,..                               m
                                                                  ,g=                               .
y                           '
                                                      '.        '.=            ,
                                                                                 ,,                                             .,,                  .,,.       F,i;;
                         . A-         ..
                                                        =
198.
l.
m             .,.                                                              ...     ..                 im                                 '.
i         ...                                    ,
3; L'" _                                 ,,
in f. hm Ni.                                                                      -                      '
                                       =                                                                                          c.= = -,                            '.i m                         ,,,                                                                               ,,,
                                                      )
                                                                                                                                              =
i                         g4...                      ,,
L.
i.
                                                                                               ..     .u
                                                                                                                  .n FCPL85.03
      -                                                                    Figure 5.1 BRUNSWICK UNIT 1 RECIRCULATION SYSTEM PIPING MODEL CPL-30-100 Revision 2                                                           24 nutg_qh

6.0       

==SUMMARY==
AND CONCLUSION Evaluation.of the repairs to the Recirculation System reported herein shows that the resulting stress levels are acceptable for all design conditions. The stress i
levels have been assessed from the standpoint of load i
capacity of the components and the resistance to crack growth.
i Acceptance criteria for the analyses have been estab-lished in Section 3.0 of this report which demonstrate that:
: 1. Overlay repaired welds meet margins of safety in-      'I
         ~
herent in IWB-3640 of ASME Section XI (Reference 1).
: 2. The one flawed weld which did not require weld overlay repair-will not exceed the allowable flaw size of Reference 1 as modified by. Reference 2 over at.least the next 18 months.
l l
Analyses have been performed and results are presented which demonstrate that the repaired welds satisfy these
  -                      criteria by a large margin. Analyses have also been CPL-30-100                            25 Revision 2

f performed which demonstrate that the unrepaired weld satisfies these criteria by a large margin.                         ,
 }
Fu r t he rmo re , it is concluded that IGSCC experience in the Reactor Recirculation System at Brunswick Unit 1 does not increase the probability of a design basis pipe rupture at the plant. This conclusion expressly con-t~
siders the nature of the cracking which has been ob-I              served at Brunswick Unit 1, and the likelihood that other similar cracking may have gone undetected.
I             Finally, the possibility that butt welds with extremely low toughness exist at Brunswick 1 nas been considered and found not to violate acceptance criteria.
  \
t I,
i I
CPL-30-100                             26 Revision 2 ritit99.I.l.

I I      

==7.0       REFERENCES==

i
: 1)   ASME Boller and Pressure Vessel Code, Section XI,
 '                    1983 Edition with Addenda through Winter 1984, Paragraph IWB-3640, " Acceptance Criteria for Austenitic Steel Piping."
: 2)   NRC Generic Letter 84-11, dated April 19, 1984,
  !                    File No. CPLO30.0012.
I
{
: 3)   General Electric Design Specification 22A1417, Revision 2,  File No. CPLO30.0012.
: 4)   General Electric " Brunswick Steam Electric Plant Unit 1 Recirculation Pipe System Stress Reanaly-sis," 6/11/85, File No. CPLO30.0012.
: 5)   NUTECH Computer Program PISTAR, File No.
08.003.0300, Version 3.2.
: 6)  NUREG 1061, Vol. 1,  " Investigation and Evaluation of Stress-Corrosion Cracking in Piping of Boiling Water Reactor Plants," Second Draft, April 1984.
   -               7)   NUTECH Computer Program NUTCRAK, Version 2.0.2, File No. 08.039.0005.
CPL-30-100                             27
    ~
Revision 2 nutggh

I
: 8) NUTECH Report NSP-81-105, Revision 2,   " Design Report for Recirculation Safe End and Elbow Repairs, Monticello Nuclear Generating Plant,"
December 1982   Elle No. 30.1281.0105.
: 9) EPRI Interim Report, " Examination of Weld Overlayed
                                                                          <g 1
Pipe Joints," dated April 1985, RP1570-2.
I li s.
CPL-30-100                         28 Revision 2 nutRch}}