ML20064F986
| ML20064F986 | |
| Person / Time | |
|---|---|
| Site: | Wolf Creek  |
| Issue date: | 03/08/1994 |
| From: | Carns N WOLF CREEK NUCLEAR OPERATING CORP. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| WM-94-0042, WM-94-42, NUDOCS 9403150522 | |
| Download: ML20064F986 (13) | |
Text
-.-
j W$LF CREEK NUCLEAR OPERATING CORPORATION l
Nml S. " Bun" Cmns chairman, Prestent anti cn..n mowe o**'
March 8, 1994 1
-I WM 94-0042 i
U.
S.
Nuclear Regulatory Commission
)
ATTN: Document Control Desk 1
Mail Station PI-137 Washington, D.
C.
20555 1
Reference:
Letter WM 92-0035, dated March 5, 1992, from B.
D.
Withers, WCNOC to the NRC Document Control Desk
Subject:
Docket No. 50-482:
Resubmittal of Inservice Inspection Program Relief Requests IIR-23,.IlR-24, and IlR-27
)
1 Gentlemen:
This letter resubmits Inservice Inspection (ISI) Program Relief Requests IIR-23, I l R-2 4, and IIR-27, in accordance with 10 CFR 50.55a (g) (5) (iii) for relief from ASME Section XI requirements.
10 CFR 50.55a (g) (5) (iii) allows licensees to submit relief requests based on a determination that conformance with certain code requirements is imp r a c ti cal.
These relief requests, which are p rovided in the attachment, apply to ISI Periods 1 and 2 and are being resubmitted based upon discussions with Mr.
W.
D.
Reckley, NRC. Project Manager, on January 21, 1994, during a teleconference with Wolf Creek Nuclear Operating Corporation (WCNOC) personnel.
The reference originally submitted Relief Requests IlR-23 through IlR-30.
WCNOC requests that the attached relief requests be evaluated. in accordance with the requirement of 10 CFR 50.55a (g) (6) (1).
This requirement allows the NRC Commission to grant relief and impose alternative requirements as it determines is authorized by law and will not endanger life or property or the common defense and security and is otherwise in the public. interest giving due-consideration to the burden upon the licensee that could result if the code requirements were imposed on the facility.
If you have a n'/ questions concerning this matter, please contact me at (316) 3 6 4 - 8 8 T', extension 4000, or Mr. Kevin J.
Moles at extension 4565.
Very truly yours, J-14010i "eil s carns Attachment cc:
L.
J. Callan (NRC), w/a G. A.
Pick (NRC), w/a W.
D.
Reckley (NRC), w/a L.
A.
Yandell (NRC), w/a f (ff '
N b @ ! OudM n VsW3M Phone (3@8831 9403150522 94030s I
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4 4 Attachment to WM 94-0042 Page 1 of 12 ISI RELIEF REQUEST IIR-23 Qtnenents:
BB-01-F207, BB-01-F307, BB-01-F407, BB-01-F305, BB-01-F405, BB-01-F306, BB F2 0 3,
BB-01-F303 Catenorv:
Section XI, Table IWB-2500-1, Examination Category B-J, Item B9.1 Descrintion:
Reactor Coolant Pumps "B",
"C",
and "D"
Suction to Elbow, Steam Generators "C"
and "D"
Outlet Safe-End to Elbow, Steam Generator "C"
Outlet Elbow to Crossover Leg Spool, and Reactor Pressure Vessel Outlet Nozzles "B" and "C" Safe-End to Pipe.
Code Reauirement:
Requires the inner 1/3t of the weld plus 1/4" of the base metal beyond the we]1 toe be scanned as shown by Figure IWD-2500-8.
Basis for Relief:
The subject welds were examined during the third refueling outage in 1988.
At that time, geometry and search unit capabilities prompted WCNOC to classify these welds as limited examinations for the detection scans of reflectors transverse to the weld axis.
The code required volumetric examinations were completed perpendicular to the weld axis in two (2) directions with no reportable indications.
The special side by side dual element search units used to examine the subject cast stainless steel (CSS) welds were too large to maintain sufficient contact in the circumferential scan direction (reference Figure 1).
The combination of weld crown and weld shrinkage (welds F203 and F303 due to weld taper) caused lift off of the search unit which in turn resulted in loss of coupling-from the examination surface preventing the transmission of the ultrasound into the component.
Contact was sufficient for scans perpendicular to the weld axis.
WCNOC contends that other transducers may have maintained better contact along the weld crown, but would not have provided as an effective examination.
This is because the transducers used to examine this CSS material were designeu specifically to enhance the flaw detection capabilities using technologies available at the time these examinations occurred (198B).
The transducer size, frequency, damping, focusing, and wave mode were all variables optimized to provide the best response in this coarse grain material. When transducers-deviate from this
Attachment to WM 94-0042 Page 2 of 12 design and are used to send sound into CSS material, it is entirely probable that the returning sound / signal has been so altered by the effects of scattering that any flaw indications would be masked by the noise reflections caused by grain boundaries.
Alternate Examination:
Prior to examination of these welds, WCNOC sponsored a round robin performance demonstration at the Electric Power Research Institute for the inspection of CSS mat rials.
Based on the results, the highest performing vendor was selected with the confidence that the selected vendor would provide the highest quality examinations with the greatest probability of detection. Therefore, WCNOC is confident in the quality of these exams and that they were examined to the fullest extent possible.
Presently, transducer design has been improved to provide a more complete examination of these welds (F203 and F303 are on a taper which i
adds additional problems with search unit access).
However, WCNOC is of the opinion that re-examination of these welds prior to their second interval examination would result in a hardship without a compensating
)
increase in safety.
Re-examining these welds would create a significant
)
l burden due to the additional radiation exposure (approximately 9 man-Rem).
Additionally, the costs associated with the re-examination would be significant.
ASME Code Section III:
Ultrasonic examinations of these welds at 0*
and 41 showed no indications.
Evaluation of Plant Safety:
Strict ASME Section III quality controls were used when designing, fabri.. ting, and installing these welds.
In addition, these welds were ultrasocienlly examined with no irregularities found.
These welds were previously examined in the first period of the first ten year interval (this interval will conclude in September 1995).
They will again be inspected as required by the ISI Program Plan for the second ten year interval.
For inspection of these welds during the second interval, it is expected that improved technologies will allow a more complete circumferential examination as long as a quality inspection can be achieved without the burden of a significant monetary expense.
100%
completion of the perpendicular scans from both directions provides confidence through the next inspection that the welds are structurally sound and do not compromise the health and safety of the public.
.l Y
Attachment to WM 94-0042 Page 3 of 12 ISI RELIEF REQUEST IIR-24 I
'l Comnonent.1 TEM 01-SEAM-2-H Cateacry:
Section XI, Table IWC-2500-1, Examinatio' itegory C-A, Item C1.20 Descrintion:
Boron Injection Tank Upper Head to Shell Weld Code Reauirement:
i r
Requires the weld plus 1/2" of the base metal on both si'.les of the weld be scanned as shown by figure IWC-2500-1 Basis for Relief:
The subject weld was examined during the third refueling outage in 1988.
i At that time, geometry and search unit capabilities prompted WCNOC to classify this weld as a limited examination for the detection scans of reflectors transverse to the weld axis.
The code required volumetric i
examinations were completed perpendicular to the weld axis in two '.(2) i directions with no reportable indications.
The special side by side dual element search units used to examine the subject cast stainless steel (CSS) weld was too_ large to maintain sufficient contact in the circumferential scan direction (reference Figure 1).
The combination of weld crown and weld shrinkage caused lift
'l off of the search unit which in turn resulted in loss of coupling from the examination surface preventing the transmission of the ultrasound into the component.
Contact was sufficient for scans perpendicular to the weld axis.
WCNOC contends that other transducers may have maintained better contact along the weld crown, but would not have provided as an.ef fective examination.
This is because the transducers used to examine this CSS material were designed specifically to enhance the flaw detection capabilities using technologies available at the time the examination occurred (1988).
The transducer size, frequency, damping, focusing, and wave mode were all variables cptimized to provide the best response in this coarse grain. material.
When transducers. deviate f rom a this j
design and are used to send sound into CSS material, it is entirely probable that the returning sound / signal has been so -altered by : the effects of scattering that any flaw indications would be masked by the noise reflections caused by grain boundaries, i
. _. ~ _. _ _ __
4 Attachment.to WM 94-0042 Page 4 of 12 Alternate Examinatior.:
Prior to examination of these welds, WCNOC sponsored a round robin performance demonstration at the Electric - Power Research Institute for the inspection of CSS materials.
Based on the results, the highest performing vendor was selected with the confidence that the selected vendor would provide the highest quality examinations with the greatest probability of detection. Therefore, WCNOC is confident in the quality of these exams and that they were examined to the fullest extent
- possible, i
Transducer design presently allows a more complete examination of this i
weld.
However, WCNOC is of the opinion that re-examination prior to its second interval examination would result in a hardship without-a compensating increase in safety.
Re-examination of this weld would represent an additional radiation exposure and, because other CSS welds
)
on this component are not scheduled for examination prior to completion of the first ten year interval, a significant monetary expense would be incurred.
bSME Code Section III:
A complete ultrasonic examination was performed at an angle of O' and approximately 50% of the weld was examined with angles of 41*,
These inspections revealed no indications.
Evaluation of Plant Safety:
Strict ASME Section III quality controls were used when designing, fabricating, and installing this weld. This weld was ultrasonically inspected to the fullest extent possible with no irregularities found.
This weld was previously examined in the first period of the first ten year interval (this interval concludes in September 1995).
It will again be inspected as required by the ISI Program plan for the second ten year interval.
For inspection of this weld during the second interval, it is expected that improved technologies will allow a more complete circumferential examination as long as a quality inspection can be achieved without the burden of a significant monetary expense.
100%
completion of the perpendicular scans from both directions provides confidence through the next inspection that the weld 'is structurally sound and does not compromise the health and safety of the public,
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O O ct TYPICAL CIRCUMFERENTIAL SCAN LIFTOFF 8
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TRAN SOUCE R 0
WEDGE I
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Attachment to WM 94-0042
'Page 6 of 12 ISI RELIEF REQUEST IIR-27 Comoonent:
TEM 01 -SEAM W 1
Cateoorv:
l Section XI, Table IWC-2500-1, Examination Category C-A, Item Number C1.20 Descriotion2.
Boron Injection Tank Bottom Head to Shell Weld Code Recuirement:
Requires the weld plus 1/2 inch of the base metal on both sides of the weld be scanned as shown by figure IWC-2500-1.
Basis for Relief:
The subject weld was examined during the fifth refueling outage in 1991.
Component structure, weld geometry and search unit size prompted WCNOC to classity this as a limited weld examination.
The volumetric examination of the subject weld is limited as demonstrated by Figures 3A through 3D and the following table:
BEAM TOWARD BEAM TOWARD LIMITATIONS SHELL HEAD Weld Configuration
-57%
-33%
Leg Supports
-22%
-25%
Instrumentation Nozzle
-4%
-5%
Total Weld Coverage 17%
37%
During past cast stainless steel (CSS) material examinations, - search unit capabilities limited examinations for the detection scans' of reflectors in the transverse direction.
The vendor designed a special search unit based on the experiences of the past.
The unit maintained the essential parameters and configured the search unit in a front to-back dual element tandem arrangement to improve examination coverage, j
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Attachment to WM 94-0042 Page 7 of 12 However, even with this improved transducer design, the circumferential scan was 100% limited because of this weld configuration (and the physical obstructions listed above) which is configured slightly different than those in the past.
Welds that are either on a taper or a taper of a transition between the components being joined by the weld do not allow for access of the search unit to effectively scan the examination volume, as evidenced by the figures, b1 ternate Examination:
Prior to examination of these welds, WCNOC sponsored a round robin performance demonstration at the Electric Power Research Institute for the inspection of CSS materials.
Based on the results, the highest performing vendor was selected with the confidence that the selected vendor would provide the highest quality examinations with the greatest probability of detection. Therefore, WCNOC is confident in the quality of these exams and that they were examined to the fullest extent possible.
Present transducer designs may allow a more complete examination of this weld (the physical obstructions would still be present).
Ilowever, WCNOC is of the opinion that re-examination prior to its second interval examination would result in a hardship without a compensating increase in safety.
Re-examining this weld would represent an additional-radiation exposure and, because other CSS welds on this component are not scheduled for examiestion prior to completion of the first ten year interval (this intervar concludes in September 1995), a significant monetary expense would be incurred for a special transducer to fit the weld configuration and the actual physical examination itself.
ASMC Code Section III:
A complete ultrasonic examination was performed at an angle of 0*.
The axial and circumferential scans were limited in the following way.
HEAD TO SHELL TO SCAN ME,THOD SHELL HEAD Axial
-40%
-90%
Circumferential
-40%
-90%
These inspections revealed no indications.
Evaluation of Plant Safety:
Strict ASME Section. III quality controls were used when designing, fabricating, and installing this weld.
This weld was ultrasonic inspected to the extant possible with no irregularities found.
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Attachment to WM 94-0042 Page 8 of'12 j.
In addition to the ultrasonic examination, a System Pressure Test (STS PE-044A) was performed on the Baron Injection Tank in May of 1991 with no indications of leakage by the tank.
The upper head to shell weld j
(1-TEM 01-SEAM-2-W) was ultrasonically inspected during the third l
refueling outage in both axial directions with no indications found.
For inspection of this weld during the second interval, it is expected that improved technologies will allow a more complete circumferential 4
examination (physical obstructions still present) as long as a quality inspection can be achieved without the burden of a significant monetary j
expense.
Based on what was scanned, in conjunction with the pressure i
test and upper head to shell weld inspection, a satisfactory level of I
confidence is achiev7d without compromising the health and safety of the public.
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- -5.64 SOUARE INCIES l2.m3] AREA (917 CUBIC INCHES 4
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I IN TOTAL WELD VOLUME I.
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.].500 L
-T I
00 iAPER / TRANSITION AREA.
NO UT SOUND TRANSHISSION IN THIS REGION OUE TO TRANSOUCEH
{t u n 5(4ol t_IFTOFF FROM PART SUniACE IN THIS AREA.
Figure 3A AREA OF INTEREST l
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?N Ek AREA COVERAGE I'1E AM D I REC T I ON TOWARDS SHELL:
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UPPER REGION - 2.06 SOUARE INCHES oe 23G CUOIC INCHES l
3G PERCENT Cg O.308 SQUARE INCHES 3
LOWER REGION 45 CUBIC INCHES
^
7 PERCENT 2l TOTAL:
thl PERCENTAGE OF WELO EXAMINED: 43
- [,[ ',,
PERCENTAGE OF WELO NOT EXAMINED: 57
-"((1 DEAM OIRECTION TOWARDS HEAD:
3.76 SOUARE INCHES 430 CUBIC INCHES I
67 PERCENT i
TOTALS:
s PERCENTAGE OF WELD EXAMINED: 67
'b6 PERCENTAGE OF WELO NOT EXAMINED: 33 N
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- AREA OF INTEREST NOT EXAMINED m
s
- !au M !!J 2"^ '
Figure 3B RESTRICTIONS
i' EN W"
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AREA COVERAGE BY INSTRUMENTATION NOZZLE
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NOTEe LENGTH OF RESTRICTION 4 INCHES o 2 LOCATlONS RE 1HIS YlELOS S.0% OF TIE TOTAL WELO IS UNDEH
-n INSTRUMENTATION NOZZLE.
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'P3 ! T..,.*..-m-ED BEAM DIRECTION TOWARO SHELL:
I 94N-mfd UPPER REGION - O.46 SOUARE INCIES
- O M3 3.60 CUOIC INCIES g
V){ S5;.:i 4I PERCENT rr
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nahme 5-NV LOWER' REGION - O.SS SOUARE INCHES
- *iTJ..
4.40 CUDIC INCHES
~l INSTRUMENTATION NOZZLE l
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.SS PERCENT TOTALS:
PERCENT OF UELD EXAMINED: 0.9 PERCENT OF WELD NOT EXAMINED: 4.I BEAM DIRECTION TOWAROS HEAOr O.O SOUARE 1NCHES 0.O CUDIC INCHES O.O PERCENT TOTALS:
PERCENT OF WELD EXAMINEO: 0.0 PERCENT OF WELD NOT EXAMINED: S
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AREA OF INTEREST NOT EXAMINED M
=
ymn LE6h,si Figure 3C COVERAGE IN AREA WITH INSTRUMENTATION NOZZLE
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