View source for U-603178, Forwards Four ASME Section XI Relief Requests Re Performance of non-destructive Exams for First 120-month Inservice Insp for CPS

{{Adams
| number = ML20210G371
| issue date = 07/29/1999
| title = Forwards Four ASME Section XI Relief Requests Re Performance of non-destructive Exams for First 120-month Inservice Insp for CPS
| author name = Sipek J
| author affiliation = ILLINOIS POWER CO.
| addressee name = 
| addressee affiliation = NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
| docket = 05000461
| license number = 
| contact person = 
| document report number = U-603178, NUDOCS 9908030079
| document type = CORRESPONDENCE-LETTERS, INCOMING CORRESPONDENCE
| page count = 16
| project = 
| stage = Request
}}

=Text=
{{#Wiki_filter:.   ,.
liknots Power Company Chnton Power Station P o. Box 678 Chnton,IL 61727 Tel 217 935-8881 Joseph V. Sipek g                                                              Director - Licensing w~ aww U-603178 8E.100c July 29, 1999 Docket No. 50-461                                                               10CFR50.55a Document Control Desk                                                                                           i Nuclear Regulatory Commission                                                                                   l Washington, D.C. 20555
                                                                                                                             ]

==Subject:==
Submittal of Four ASME Section XI Relief Requests Regarding Performance of Non-Destructive Examinations for the First 120-Month Inservice Inspection Interval for Clinton Power Station

==Dear Madam or Sir:==

Attached for NRC review and approval are four requests for relief from the requirements of Section XI of the American Society of Mechanical Engineers (ASME)
Boiler and Pressure Vessel Code,1980 Edition through Winter 1981 Addenda, with regard to the performance of non-destructive examination of welds for the first 120-month inservice inspection interval for Clinton Power Station (CPS). Contained within each relief request are the details concerning the applicable ASME Section XI Code requirements and the affected welds, as well as the basis and justification for the requested relief.
Inservice inspection of ASME Code Class 1, 2, and 3 components is required to be performed in accordance with Section XI of the ASME Code pursuant to 10CFR50.55a(g) except where specific written relief has been granted by the Commission. Per 10CFR50.55a(gX5), if a licensee determines that conformance with                                l certain requirements of Section XI of the ASME Code is not practical, information shall I
be submitted to the NRC in support of that determination and a request made for relief from the ASME Code requirement. Further,10CFR50.55a(aX3) states that alternatives to the requirements of 10CFR50.55a(g) may be used, when authorized by the NRC, if l
the proposed alternatives would provide an acceptable level of quality and ssfety, or compliance with the specified requirements would result in hardship or unusual difficulties without a compensating increase in the level of quality and safety. The attached relief requests (Attachments 1 through 4 of this letter) are accordingly submitted for NRC review and approval pursuant to the requirements of                                    l      ;
10CFR50.55a(g)(5) and 10CFR50.55a(gX6Xii)(A)(5). The applicable edition of Section XI of the ASME Code for the first 120-month inservice inspection (ISI) interval                    i at CPS is the 1980 Edition through Winter 1981 Addenda.                                              y 9909030079 990729'' 9 PDR ADOCK 050004617
     .O PDR ~
L-                                                                                                                  .

f U-603178 Page 2 i
A brief description of each relief request (along with the corresponding attachment number to this letter) is provided below:
Relief Reauest No. Attachment No.                                Description i
4014                1              This is a request to allow a reduction in the required volumetric examination volume for nine (9) reactor l                                                  pressure vessel (RPV) nozzle-to-shell welds (Code l                                                  Class 1, Examination Category B-D, Item B3.90). A I
portion of the Code required examination volume cannot be completed due to the RPV nozzle              )
configuration / geometry.
4015                2              This is a request to allow a reduction in the required volumetric examination volume for RPV shell-to-flange weld number RPV-C5 (Code Class 1, Examination Category B-A, Item Bl.30). A portion of the Code required examination volume cannot be completed due to the RPV shell flange configuration / geometry.                               1 i
4016                3              This is a request to allow a reduction in the required J volumetric examination volume for RPV longitudinal weld numbers RPV-V2B and RPV-V2C (Code Class 1, Examination Category B-A, Item Bl.12). Reliefis requested since examination of the remainder of the weld would require erecting scaffolding or a platform in a very high radiation area.
4017                4              This is a request to allow a reduction in the required volumetric examination volume for the bottom head-to-shell Course No. I weld number RPV-Cl (Code Class 1, Examination Category B-A, Item Bl.11). A portion of the Code required examination volume cannot be completed due to the bottom head-to-shell Course No. I weld configuration / geometry and location where the RPV skirt is welded to the bottom head.                                                  !
l                    It should be noted that the nine specific welds identified in Relief Request No.
l 4014 and the two welds identified in Relief Request No. 4016 were previously submitted         '
as part of Relief Request No. 4006 and part of Relief Request No. 4010, respectively, in       )
IP {{letter dated|date=June 5, 1996|text=letter dated June 5,1996}} (U-602566). By {{letter dated|date=December 4, 1996|text=letter dated December 4,1996}}, the NRC               1 informed IP of the Staff's determination regarding the relief requested in the IP June 5,      1 1996 letter. Specifically, the Staff denied Relief Request No. 4006 (in part) and Relief       i i

U-603178 Page 3 Request No. 4010 (in its entirety) on the basis that it was inappropriate to grant relief prior to the subject welds being examined. Subsequently, IP has performed the required examinations of the welds identified in Relief Request Nc. 4014 and No. 4016 to the maximum extent practical. As such, IP is now seeking relief from the requirement to perform a complete volumetric examination for the subject welds as described in the attached ReliefRequests.
The IP {{letter dated|date=June 5, 1996|text=June 5,1996 letter}} also included requests for relief that were approved by the NRC. Specifically, Relief Request No. 4005 was approved, as identified in the NRC {{letter dated|date=December 4, 1996|text=letter dated December 4,1996}}. This is noted because Relief Request No. 4015 and No.
4017 (as attached) are comparable to Relief Request No. 4005 with respect to the relief requested, the types of welds involved, and the reasons why 100% of the weld volume l           could not be examined.
Sincerely yours, Jo ph . Si Di ector-Licensing EET/krk Attachments cc:     NRC Clinton Licensing Project Manager NRC Resident Office, V-690 Regional Administretor, Region III, USNRC Illinois Department of Nuclear Safety l
l i
l                                                                                                           j I

Attachment 1 to U-603178        I Page 1 of 6 1
l ILLINOIS POWER COMPANY Clinton Power Station ASME Section XI Relief Request RELIEF REQUEST 4014 (Revision 0)                                                   l l
l                                                                   Nine (9) reactor pressure vessel (RPV) novic-to-shell        l SYSTEM / COMPONENT (S) FOR WHICH RELIEF                    welds, Code Class 1, Examination Category B-D, item IS REQUESTED                                               B3.90. See attached Table i for wcld numbers.
l ASME Section XI,1980 Edition thru Winter 1981 CODE REQUIREMEVr                                           Addenda, Table IWB-2500-1, Category B-D, item B3.90 requires volumetric cumination of the wcld and adjacent base material as defined by Figure IWB-2500-7(b)
For cach of the identified nonJc-to-shell welds, relief is CODE REQUIREMENT FROM WHICH RELIEF IS                      requested from performing complete volumetric REQUESTED                                                  examination of the required volume which is restricted due to scanning limitations presented by the RPV noule configuratica/gcometry. Attached Figure lA through IC depict a typical RPV nonic weld, what portion of the examination volume is restricted by nonle configuration / geometry, and how that restriction affects the percentage of the volume that can be examined by each of the various examination techniques (0 L-Wave,45 P-Scan,60 T-Scan, etc.).
Attached Table 1 identifies the estimates of the composite Code cumination vc,lume that have been examined for caco of the subject RPV noalc welds.
A portion of the Code required examination solume cannot BASIS FOR RELIEF                                           be     completed       due    to     the     RPV      nonlc configuration / geometry. Attached Figures l A through IC identify the limitations presented by a typical RPV nonic configuration / geometry for cach examination technique employed at Clinton Power Station (CPS).
Illinois Power Company (IP) perfonned ultrasonic ALTERNATE EXAMINATIONS                                     cxamination of these welds to the maximum extent feasible for the required examination solume.
Performance of ultrasonic examination of approximately 65 JUSTIFICATION FOR THE GRANTING OF                          percent of the required examination volume for cach of the RELIEF                                                     nine identified welds provides reasonable assurance of the stmetural integrity of each entire weld. Altogether, there are twenty-nine (29) RPV nonlc-to-shell welds requiring ultrasonic examination. During two previous refueling outages (RF-2 and RF-4) IP performed ultrasonic examination on twenty (20) of these welds. These ultrasonic examinations did not cover 100% of the required examination volume of each of these 20 welds. There were no unacceptable indications in the areas examined. IP submitted a relief request (Relief Request 4006, IP letter U402566 dated June 5,19%) for these welds, which was approved by the NRC (for the twenty examinations performed in two previous outages) to [ctmit examination ofless than the minimum required wcld examination volume.
I                                                             1 l

At tachtnent 1 to U-603178 Page 2 of 6
          . Tie remaining nine (9) welds were examined during refueling outage RF-6 and no unwentable indication identified.
The examination cmtrage for each of these nine (9) welds is approximately the same as for the twenty (20) welds xlentdied in Relief Request 4006. It should be noted that during initial plant construction, all of these welds were
,           rhiivyop64 and the results were acceptabic. These welds were also ultrasonically examined in accordance with the l-          Presenice Inspection Plan, and the results of those exammations were also acceptable.
ASME Section V, Article 4, requires that the examination volume (weld and adjacent base material) be scanned by straight and angle beam,45* and 60*, techniques. Article 4 of ASME Sxuon V allows the examination to be performed from one side of the weld. Due to the RPV nozzle configuration, ultrasonic examination can only be performed from the shcIl side. Due to tie bend radius and thickness of the nozzle, tie following examination volumes were scanned using the techniques listed below (not taking beam spread into account):
1 1                                 Techniaue                                     % of Exarnination Volume Examined i
0* L-Wave                                                50 %
45'P-Scan Clockwise                                      60 %
l                                 60*P-Scan Clockwise                                      60 %
l                                 45'P-Scan Counter Clockwise                              60 %
1 60*P-Scan Counter Clockwise                              60 %
45 T-Scan Shell Side                                     80 %
1             .                   60* T-Scan Shell Side                                    88 %
Composite examination volume = 65%
It should be noted that the outer 1/4" volume was excluded from this determination of examination volume because of inherent properties of the ultrasonic examination metixxis near-surface effect.
As shown above, at least one technique (60 T-Scan) cmcrs close to 90% of the exanunation volume. Illinois Power Company believes that the actual area exanuned using tie 45* T-Scan and 60* T-Scan tecimiques was mer 90%,
however, if any indication would have been present in the area identified as not examined, it would have been difficult to size. For this reason, the examiner has identified 80% and 88 % cmtrage for 45 T-Scan and 60 T-Scan techniques respectively. It should be noted that the ASME, per Code Case N-460 considers 90% cmerage as meeting the Code requirements. Code Case N-460 has been incorporated into Regulatory Guide 1,147.
Tie examination limitation imposed by the RPV nozzic/shell configuration makes it impractical to perfonn a complete          i volumetric examination (90% or more) of the nozzle-to-shell welds. However, IP believes that performance of ultrasonic       !
examination of the welds to the maximum extent feasib'e (for a composite examination volume of approximately 65%) is
           . suflicient for confirming weld integrity anxi therefore prmides an acceptable lesti of quality and safety.                  j Reliefis requested for the first ten-year interval at CPS.
IMPLEMENTATION SCHEDULE                                                                                                  .
F 2
i
                                                                                                                                         )

r
( '
* Attachment 1 l
to U-603178 l                                                               Page 3 of 6 l
l TABLE 1 CODE CATEGORY B-D 1
EXAMINATION COVERAGE Estimated Percentage Of l
Volume Examined Due
        % eld Number                  Description       To Nonle Confieuration  j f
N2A, N2H, N21, N2K   RecirculationInlet Nozzles         65 N3B,N3D              Main Steam Nor21cs                 67 NSB                  Core Spray Nozzle                  63 N6A                  RHR CoolantInjection Nonle         65 N9B                  Jet Pump Instrument Nozzle         66              1 l
3

                                                             > g Sfi" -
..                                                           n e&$e yg&            , a d
l                                               /
e                                           /
W l
l e
            .h S              e g
a Ao t                 r e
v o
1                    c e   1         m a
x el                  e r z   z n      la uo        t o      t e
m                                 e v
gN          n      d le o
w i          w                                 -
i                                                     L V    l C          e FP v                               O o
R             L w
l             O         , I I I I                   ,jI    '
a                                                       e c                                                       v o   '
i                                                        w p                                                      L y                                                      'O T                   %                                              _
A N     i I I           I l I , g i '
N s
                                                          ~

                                                       $        sa" -
EC$O3
                                                       *"          a d
-                l e                         /
-                W l
l e
-                h         e g
S         a r
e v
Bo t          o c
1         1 m
a x
e        e    R                   n a
n                         c
             'e z  l     n o c             n s
r z        o s
o c
T uo       t n
P d
s P
F 4
gN       i n
a             F       '
n             4 i
V l
C    o c
R FP             s R        T                                          m.
F 4
-                l                   ,lI     i I          j' a
c                                             _     _
-                 i                                      n             _
o p                                     s y                                      -
R P             .
T                -
4 A
                               /l l i i I                   ; '
n o
c s
T F
4 x
                                                  ~
                                                  ~

R               gE _
1                                         g 4e:.              :
7                 ,* .
     . e d
l e                             /
W                            /
l l
e h
S               R e
g a                   n Co t             r e
v o
c s
1                o c                  T e   1 m
a 0
6 el z            x e             n r z        n n
a o
c s
uo         o c
s P
gN       t P            -
0 6
i V     i n   d n
a R
FP        l n
o                                    .
R     C      c s                                         _
T l
                         '0 a          6 c
                                ,I I      ig                 .
i                                                      .
p                                          n y                                          o          _
T                                             -
R                        P A                                         '
6 1l I    I     I     l r
a c
s T
0 6
x     1

Attachment 2
  ,                                                                                                             to U-603178 Page 1 of 3 ILLINOIS POWER COMPANY Clinton Power Station ASME Section XI Relief Request RELIEF REQUEST 4015 (Revision 0)
Reactor Pressure Vessel (RPV) shell-to-flange weld, Code SYSTEM / COMPONENT (S) FOR WHICH RELIEF                      Class 1, Examination Category B-A, item Bl.30, wcld IS REQUESTED                                                 rumber RPV-C5.                                             t ASME Section XI,1980 Edition through Winter 1981 CODE REQUIREMENT                                             Addenda, Table IWB-2500-1, Category B-A, Item Bl.30        l requires a volumetric examination of the weld and adjacent i wcld material as dermed by Figure IWB-2500-4.
Relief is requested from performing 100% volumetric CODE REQUIREMENT FROM WHICH RELIEF IS                        examination cf the examination volume which is restricted REQUESTED                                                    due to scanning limitations presented by the RPV shcIl flange configuration /gcometry and inherent near-surface effects of ultrasonic examinations. It is estimated that 52% of the composite codc cumination volume has ba:n examined by ultrasonic examination. See attached Figure 1.
A portion of the Code required cumination volume cannot    l BASIS FOR RELIEF                                             be completed due to the RPV shcIl flange configuration /
geometry. Figure 1 identifics the geometrical limitation presented by the RPV shcIl flange with respect to the various ultrasonic cumination techniques performed on the RPV shcIl to flange weld.
Illinois Power Company (IP) completM ultrasonic ALTERNATE EXAMINATIONS                                       examination of this wcld to the maximum extent feasible for the required cumination volume.
Performance of approximately 52% of the required JUSTIFICATION FOR THE GRANTING OF                            cxamination volume provides reasonable assurance of the RELIEF                                                       structural integrity of the entire weld. Based on the examination conducted, no unacceptable indications were found. It should be noted that during initial plant construction, this wcld was radiographed and the results were acceptable. The wcld was also ultrasonically cumined in accordance with the Preservice Inspection Plan, and the results of that cumination were also acceptable.
I L
k

Attachment 2 to U-603178 Page 2 of 3 ASME Section V, Article 4, requues that tie examination solume (weld and adjacent base material) be scanned by              ,
                                                                                                                                        ~
          . straight and angle beam,45 ' and 60 ', techmques. Article 4 of ASME Section V allows the examination to be performed from ore side of the wel6 Due to the flange configuration, ultrasonic exandnation can only be perfonned from the shell side oithe weld. Due to the bend radius on the flange side and the thickness of the flange, only the following examination  i miumes can be scanned for the techmques listed below (not taking beam spread into account):
Techniaue                                    % of Examination Volume Examined j                                0*l-Waw                                                58 %
l                                45* T-Scan Upstream Side                               85 %
i 60* T-Scan Upstream Side                               89 %
45'T-Scan Downstream Side                              0%
60*T-Scan Downstream Side                              0%                                              I l                                45'P-Scan Counter Clockwise                            60 %
60*P-Scan Counter Clockwise                            60 %
45* P-Scan Clockwise                                   60 %
60* P-Scan Clockwise                                   60 %
Composite examination volume = 52%
l It should be noted that the outer 1/4" volume was excluded from this determination of examination mlume because of l           interent properties of the ultrasonic examination method's near-surface effect.
l           As shown abme, at least one to:hnique (60* T-Scan) cmcrs close to 90% of the examination volume. Illinois Power
!           Company believes that the actual area examined using t:e 60' T-Scan was mer 90% becruse Illinois Power assumes the l           outer 1/4" was not exanuned due to near zone effects of ultrasonic method This is a wry consenative assumption, in l           fact, only a smaller portion versus 1/4" close to the surface is not examined. Similarly lilinois Power believes that the actual area examined using 45' T-scan was mer 90% It should be noted that the ASME considers 90% cmcrage to be acceptable per Code Case N-460. Code Case N 460 has been incorporated into Regulatory Guide 1.147.
The examination limitation imposed t.y the RPV flange configuration makes it impractical to perform a complete volumetric examination (90% or more) of the weld. However based on the e . amination performed, IP beliews that the structural integrity of the wcld is confirmed and prmides an acceptable level of quality and safety.
Rehefis requested for the first ten-year intenal at Clinton IMPLEMENTATION SCHEDULE                                     Power Station.
I i
2

yn E           _
8
:                                                                o E          .
ig n        wEm n
o c
s T
F 4
s n
e s
P
                                            ;   I         l I 7,
                                      \
e           s
                                    \                          w od 1             g                                       wn                 _
m
                                                               - a n                                       L a                                         5
                                                              'O 4 E
l F                                                 -
R             o                              s n
U     5 t                                  e s
G I
C 4        s n
o P
                  -       c                          7 F     V #
s
                                                  '6 T                        C' qIigg d
P                         'g Rg         7 6                       l-    a n          n                             F oR i    d n
a I4 N\
t                                n l   F                 o i
ndl e l
4
                             .g e            c s
a              -
l eh      la   r e ev T
CWS t
moc             T 4
d lem wax ev e                     n o
o s                      c                            _
w no                    s c                   T L s                                                   _
0 DP                                                     _
6
                                                        \

      ~
Attachment 3 l                                                                                                                  to U-603178 l                                                                                                                 Page 1 of 2 ILLINOIS POWER COMPANY Clinton Power Station l                                                     ASME Section XI Relief Request 1
RELIEF REQUEST 4016 (Resision 0) 1 Two (2) Reactor Pressure Vessel (RPV) longitudinal utids, SYSTLM/ COMPONENT (S) FOR WHICH RELIEF                       Code Class 1, Examination Category B-A, item Bl.12, 15 REQUbsID                                                  wcld numbers RPV-V2B and RPV-V2C.
ASME Section XI,1980 Edition through Winter 1981 CODE REQUIREMENT                                             Addenda, Table IWB-2500-1, Category B-A, item Bl.12 requires a volumetric examination of ticsc welds and adjacent matenal as defined by Figure IWB-2500-2.
I Reliefis requested from perfonning ultrasonic examination CODE REQUIREMENT FROM WHICH RELIEF IS                        of approximately 4% of the cumination volume since only REQUESTED                                                    91% of the required examination volume can be examined by automated ultrasonic examination equipment and approximately 5% of the cumination volume can be exempted by ASME Code Case N460 due to instrmnent nozzle (N12C and D) interference.
In order to perform manual ultrasonic examination of 4%
BASIS FOR RELIEF                                             cumination volume, temporary platforms (or large             ,
scaffolding) would have to be installed adjacent to the reactor inside the bioshield arca which is a very high radiation zone.
Illinois Power Company (IP) completed ultrasonic ALTERNATE EXAMINATIONS                                       cxamination of these welds to the nnximum extent feasible for the required cumination volume.
Performance of ultrasonic examination of 91% of the JUSTIFICATION FOR THE GRANTING OF                            required examination vohunc provides reasonable RELIEF                                                       assurance of the structural integnty of the entire weld. The results of 91% of the examination volume were acceptable During initial plant constmetion, the entire welds were radiographed and the resul?s were acceptabic. The welds were also ultrasanically examined in accordance with the Presenice Inspection Plan, and the results of that examination were also acceptable.
To perform the remaining 9% of the code required examination would require crecting scaffolding /platfonn in the scry high radiation area. The dose rate in this area during our most recent outage were approximately 3000 mR/hr measured at the N12 nozzles. It is estimated that performing manual examinations of the areas not restricted by N12 nozz!cs would bring the total coverage to 95% The hazards involved in this additional examination (only 4%) as well as the dose fields encoun'ered do not warrant performing this additional cumination to obtain an additional 4% costrage. It should be noted that the outer 1/4" volume was excluded from this determination of cumination volume because of inherent properties of ultrasonic examination methods near-smface effect.
I I

r Attachment 3
  .' - '                                                                                                       to U-603178 Page 2 of 2 ASME Code Case N-460 has been adopted into Regulatory Guide 1.147, Rm.11 dated October,1994. This Code Case
         . allows a reduction of tic exanunation area ofless than 10% due to interference by anotler component or part geometry.
This Code Case allows lilinois Power to not perform the 5% of the examination volume restricted by N12 no721cs, howner, it does not allow the remaining 4% of tic examination mlume to be not performed. Another 4% reduction in the exammation area for these welds wwld not significantly impact tic effectheness of the examination and thus simuld not mmpromise safety.
Reliefis requested for the first ten-> tar interval at Clinton IMPLEMENTATION SCHEDULE                                 Power Station.
1 l
1 1
1 l
I l
l l
l 2
1

Attachment 4 to U-603178 Page 1 of 2 i
I l                                                ILLINOIS POWER COMPANY l                                                      Clinton Power Station 1
ASME Section XI Relief Request l
RELIEF REQUEST 4017 (Resision 0)
                           ~        ~
Reactor Pressure Vessel (RPV) bottom head to simll course SYSTEM / COMPONENT (S) FOR WHICH RELIEF                 number I weld, Code Class 1, Examination Category B-A, IS REOiIESTED                                           item Bl.11, wcld number RPV-CI.
                                                                                                                                   )
ASME Section XI,1980 Edition through Winter 1981 CODE REQUIREMENT                                        Addenda, Table IWB-2500-1, Category B-A, Item Bl.Il requires a mlumetric examination of the utid and adjacent wcld material as defined by Figure IWB-2500-1.
Reliefis requested from performing ultrasonic examination CODE REQUIREMENT FROM WHICH RELIEF IS                   of approximately 9% of the examination volume since 81%
REQUESTED                                               of the required exandnation volume can be cumined by ultrasonic examination and a limit of 10% of the total
                                                                                                                                   ]
cxamination volume can be exempted by ASME Code Case N-460 due to the wcld configuration.
A portion of the Code irquired exandnation volume cannot BASIS FORRELIEF                                         be completed due to the bottom head to shcil course number I weld configuration /gcometry and location where RPV skirt is welded to the bottom head.
Illinois Power Company (IP) completed ultrasonic ALTERNATE EXAMINATIONS                                  cxamination of this wcld to the maximum extent feasible for the required cundnation volume.
Performance of ultrasonic examination of approximately JUSTIFICATION FOR THE GRANTING OF                       81% of the required examination volume provides RELIEF                                                  reasonable assurance of the stmetural integrity of the entire weld. During plant construction, the entire wcld was mdiographed and the results were acceptable. The wcld was also ultrasonically examined in accordance with the Picsenice Inspection Plan, and the results of that exandnation were also acceptable. Tim remaining 19% of the exandnation volume cannot be performed due to the wcld configuration / geometry and location where RPV skirt is wclded to the bottom head. Code Case N-460, Alternative Examination Coverage for Class 1 and Class 2 welds, allows lilinois Power to reduce the exandnation coverage of up to 10% due to the component geometry.11 crefore, only 9% of tic code required cumination was not performed.
i

e ,. .                                                                                                             Attachment 4 to U-603178 Page 2 of 2 ASME Secten V, Article 4, requires that the exanunation solume (weld and adjacent base material) be scanned by
           , straight.and angle beam,45
* and 60 *, techniques. Due to the weld configuration / geometry and loanion where RPV skirt is welded to the bottom head, the following exammation solumes can be scanned using the techniques listed below:
Ta:hnioue                                       %of Examination Volume Examined 0* L-Wave                                                  %%
45* T-Scan Downstream Side                                 94 %
45'T-Scan Upstream Side                                    72 %
60 T-Scan Downstream Side                                  88 %
60 T-Scan Upstream Side                                    40 %
                               ' 45' P-Scan Clockwise                                       72 %
45' P-Scan Counter Clockwise                               %%
60* P-Scan Clockwise                                       72 %
60* P-Scan Counter Clockwise                               %%
Composite examination volume = 81%
It should be noted that approximately 4% (the outer 1/4" volume) of the volume was not examined, due to inherent UT properties of near zone effect, and it is not included in the abmt determination of examination solume.
As shown abme, at least four (4) tecluuques (0* L-Wave,45* T-Scan Downstream,45* P-Scan Counter Clockwise, and 60* P-Scan Counter Clockwise) cmer mer 90% of the exanunation solume. Illinois Power belieses that the actual area exanuned using other techniques was more than what is identified abme, ha mer, if any indication would hase been present in the area identified as not examined, it would have been difrx: ult to size. For this reason, the exarniner identified lesser cmtrage for these techniques. It should be noted that the ASME, per Code Case N-460, considers 90% coverage as meeting the code requirements. Code Case N-460 has been incorporated into Regulatory Guide 1.147.
The exammation limitation unposed by this geometry / configuration makes it impractical to perform a complete solumetric examination (90% or more). However, Illinois Power beliests that performance of ultrasonic examination of the weld to the maximum extent feasible (for a composite examination volume of approximately 81%) is sufficient for conftrming weld integrity and that such examination therefore prmides an acceptable lesel of quality and safety.
Reliefis requested for the first ten-year interval at Clinton IMPLEMENTATION SCHEDULE                                      Power Station.
i 2}}