ML20198B927
| ML20198B927 | |
| Person / Time | |
|---|---|
| Site: | Byron  |
| Issue date: | 12/09/1998 |
| From: | Graesser K COMMONWEALTH EDISON CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| BYRON-98-0313, BYRON-98-313, NUDOCS 9812210227 | |
| Download: ML20198B927 (15) | |
Text
Conmtonwealth Ednun Company liyron Generating Mation E
- 4 450 North German Church Road
- II) run,11. 61014979s Tel 815-2M5 611
' December 9,1998 LTR: BYRON-98-0313 l FII.E: 2.01.0700 U.S. Nuclear Regulatory Commission ATfN: Document Control Desk Washington, DC 20555-0001 1
l I
Subject:
Byron Station Unit 2 First 10 Year Inservice Inspection Program Relief Requests: J NR-26, Limited Volumetric Examination of Reactor Coolant System Weld Due to Whip Restraint Obstruction; NR-27, Volumetric Examination of Reactor Presst.re Vessel Circumferential Shell Weld; and NR-28, Volumetric Examination of Reactor Pressure Vessel Circumferential Shell Weld.
Byron Station, Unit 2 Facility Operating License No. NPF-66 NRC Docket No. STN 50-455
Reference:
NRC letter, " Evaluation of First 10-Year Interval Inservice Inspection Requests for Reliefs Nos. NR-20, Revision 1, and NR-25, Revision 0, for Byron Nuclear Power Station, Unit 1," dated August 28,1998.
- In May 1998, Byron Station Unit 2 completed its first 10 year inservice inspection interval.
Attached are the remaining three requests for relief needed to closcout the examination requirements of the first interval.
The first attached relief (i.e., NR-26) is requested pursuant to 10CFR 50.55a(a)(3)(ii) on the basis that compliance with the American Society of Mechanical Engi.n-ers Boiler and Pressure Vessel
[
Code (ASME Code) requirement would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety. Specifically, reliefis requested from the requirements of ASME Code Section XI, Subsection IWB-2500 for Valve-to-Pipe weld 2RC29AC-10", J01. The ASME Code requires essentially 100% examination of the weld length.
Due to a pipe whip restraint obstruction less than 100% examination could be achieved.
l 9812210227 981209
~
~0 p
A t!mcom o mpany
,. .' Byron Ltr. No. 98-0313 Page 2 '
December 9,1998 The second and third attached reliefs (i.e , NR-27 and NR-28) pertain to the same examination requirement for Reactor Pressurc Vessel circumferential weld, RPVC-WR29. For your information, the referenced letter provides NRC approval for similar relief requests for Byron i Station Unit 1.
NR-27 is requested pursuant to 10CFR50.55a(g)(6)(ii)(A)(5) on the basis that the proposed alternative would provide an acceptable level of quality and safety. Specifically, the essentially 100% weld caverage requirement, as defined in 10CFR50.55a(g)(6)(ii)(A)(2), for weld RPVC-WR29 could not be met. Only 57% could be obtained due to interference with core barrel locating lugs.
NR-28 is requested pursuant to 10CFR50.55a(g)(5)(iii) on the basis that conformance to the ASME Code requirement is impractical. The ASME Code also requires essentially 100% weld coverage requirement for weld RPVC-WR29.
- Upon approval of these relief requests, Byron Station commits to the proposed alternative sections of the requests. Otherwise, actions described in these relief requests represent intended or planned actions by Byron Station. They are described for the NRC's information and are not regulatory commitments.
Please address any comments or questions regarding this letter to B.J. Adams at (815) 234-5441, extension 2280.
Respectfully, M
K. L. Graesser Site Vice President Byron Station KLG/JL/cb j
Attachment cc: NRC Regional Administrator, Rlll Senior Resident Inspector, Byron Byron Project Manager, NRR P:W8byttrsif 80313, doc
Attachment Ilyron Station Unit 2 First 10 Year Inservice inspection Interval Relief Requests: NR-26, NR-27, and NR-28 l
PA98byttrsi9803134x
Revisi:n 0 Pzge1ef3 l BYRON STATION UNIT 2 INSERVICE INSPECTION RELIEF REOUEST NR-26 COMPONENT IDENTIFICATION Code Class: 1
Reference:
IWB-2500, Table IWB-2500-1 Examination Category: B-J Item Numbers: B9.11
Description:
Limited Volumetric Examination of Reactor Coolant System Weld Due to Whip Restraint Obstruction Component Number: Valve-to-Pipe Weld,2RC29AC-10", J01 Drawing Number: 2SI-1-ISI, Sheet 9 CODE REOUIREMENTS Table IWB-2500-1, Examination Category B-J, Item Number B9.11 requires surface and volumetric examination of the regions described in Figure IWB-2500-8(c) for piping NPS 4 and greater. The examination includes essentially 100% of the weld length.
This wc!d exceeds the criteria of Category B-J, Note 1(b), and therefore must be selected for examination.
This note states: "All terminal end welds and joints in each pipe or branch run connected to other components where the stress levels exceed either of the foll: ving limits under loads associated with specific scismic events and operational conditions: (1) Primary plus secondary stress intensity range of 2.4S,,, for ferritic steel and austenitic steel; (2) Cumulative usage factor U of 0.4".
Table IWB-2500-1, Examination Category B-P, item Numbers B15.50 and B15.51 require pressure l retaining piping components to be pressure tested and VT-2 examined.
l I CODE REOUIREMENTS FROM WillCil REl,lEF IS REOUESTED l Reliefis requested from the examination coverage requirements of Figure IWB-2500-8(c).
l BASIS FOR RELIEF l
Pursuant to 10 CFR 50.55a(a)(3)(ii), reliefis requested on the basis that conformance with the Code requirements would result in undue hardship or unusual difficulty withos.i ; compensating increase in the level of quality and safety.
In order to perform the Code required examinations of this weld; modification of the whip restraint would be required. Weld 2RC29AC-10', J01 is adjacent to a permanent whip restraint making it only accessible for a partial volumetric examination. Byron Station would incur significant engineering, material, and installation costs to perform such a replacement and would not realize a compensating increase in the level of quality and safety tojustify such modifications.
PPS8byhn 980313. doc
l Revision 0 Page 2 of 3 BYRON STATION UNIT 2 INSERVICE INSPECTION I
RELIEF REOUEST NR-26 l
l During the First Interva!, an inspection of weld 2RC29AC-10", J01 was attempted during refuel outage B2R02. It was discovered that the surface examination and the circumferential volumetric scan could not be achieved. The restraint ring is located over this valve-to-pipe weld. The restraint ring is also adjacent to the valve body and does not allow access from the valve-side of the ring opening.
l Clearance between the pipe and whip restraint did not allow for access to the necessary examination j surface. The technicians were unable to remove the excess penetrant material to the extent necessary for a ;
meaningful examination. The circumferential scan was obstructed because of the valve-to-pipe weld '
transition narrowed the space between the weld and the restraint ring and thus prevented the transducer from scanning on the required surface. The technicians were able to obtain 100% coverage in the axial direction by reaching under the restraint ring.
The examination was rescheduled for a later outage to coincide with the corresponding Reactor Coolant System 'D' Loop weld (i.e.,2RC29AD-10",101) and preparations were made to remove both restraints if necessary. The initial concem was damage to the honeycomb material of the whip restraint when the ring was removed. Replacement honeycomb material was procured for when the restraint disassembly was attempted. The second attempt was made during refueling outage B2R07. It was then determined that the i
bottom of the threaded bolt was inaccessible due the welded bar stock and the bolt could not be removed.
The welded bar stock would have to be cut away for removal. This process would involve cutting and )
l grinding in a contaminated area and this action would potentially create airborne contamination. Without I the bolt removed, it is impossible to move the restraint ring away from the subject weld. The corresponding l 'D' Loop weld also required this removal. This was accomplished without event due to the 'D' Loop whip restraint does not possess the welded bar stock at the base of the restraint assembly.
Reasonable assurance of the continued insenice structural integrity ofweld 2RC29AC-10",101 will be
! achieved without completing the Code required volumetric and surface examinations based on the l following. Past construction, presenice and first interval inspections that could be accomplished have not revealed any rej:ctable flaws in this weld. The nquired second interval volumetric examination will bc l i performed to the maximum extent possible. In addition to the surface and volumetric exams, the Visual I l (i.e., VT-2) examination of the weld during the system leakage test performed each refueling outage and l- during the system hydrostatic test performed each interval will also continue to assure the inservice j structural integrity of this weld.
l PROPOSED ALTERNATE PROVISIONS The Code required volumetric and surface examinations will be wmpleted to the maximum extent possiHe.
Current methods allow only the axial volumetric scan.
4
. PERIOD FOR WHICH RELIEF IS REOUESTED
- Relie fis requested for the first ten-year inspection interval of the Insenice inspection Program for Byron
- Station Unit 2.
t Ps98b%trs'980313 doc
Revision 0 Page 3 cf 3 BYRON STATION UNIT 2 INSERVICE INSPECTION REI,IEF REOUEST NR-26 Figu.e 1 2RC29AC-10" 1
eWhip Restraint Sl9R-495 4+
\ -
Restraint Ring:
%"x4"x1'-2%" 1D Reference Only Not to Scale a,
o oe'*s W s' g\
l t
oo 4N4"x3"g i Honeycomb l 6I I
%"O A-193-B7 ;
E, cit w/1 *O
_4 l
Lipset Ends (Both Sides)
Welded 1 %"x4" l Bar Stock l
....u.... .........
I i l l
I l
!~
l.
Pn98byttrs'980313.&x:
j- -
Revisi:n 0 Page 1 cf 4 BYRON STATION UNIT 2 INSERVICE INSPECTION RELIEF REOUEST NR-27 l
COMPONENT IDENTIFICATION l Code Class: 1
Reference:
IWB-2500, Table IWB-2500-1 Enmination Category: B-A ;
Iton Number: Bl.Il '
Description:
Volumetric Examination of Reactor Pressure Vessel Circumferential Shell Weld l Component Numbers: RPVC-WR29 Drawing Numbers: 2RPV-1 ISI (Unit 2) ,
1 CODE REOUIREMENT l 10CFR50.55a(g)(6)(ii)(A)(2) requires that all licenses shall augment their Reactor Pressure Vessel (RPV) examination by implementing once, as part of the inservice inspection interval in effect on September 8,1992, the examination requirements for the RPV shell welds specified in Item Bl.10 of Examination Category B-A, " Pressure Retaining Welds in Reactor Pressure Vessel", in Table IWB-2500-1 of Subsection IWB of the 1989 Edition of Section XI, Division 1, of the ASME Code.
For the purpose of this augmented examination, " essentially 100%" as used in Table IWB-2500-1 mewis more than 90% of the examination volume of each weld, where the reduction in coverage is due to interference by another component, or part geometry.
CODE REOUIREMENTS FROM WHICH RELIEF IS REOCESTED Reliefis requested from the examination coverage requirements of Figure IWB-2500-1 of the 1989 Edition of Section XI, Division 1, of the ASME Code as specified in 10CFR50.55a(g)(6)(ii)(A)(2)
HISTORY Byron Station, during refuel outage B2R07, conducted ultrasonic examinations of the Byron Station Unit 2 RPV. This was the laa fuel outage of the third period of the First Inservice Inspection Interval and occurred in March and April,1998. Framatome Technologies Inc. (FTI) was contracted to perform the examinations with their state-of-the-art "URSULA" manipulator and their "ACCUSONEX" Ultrasonic Test (UT) system. The examinations were performed in accordance with the requirements in'ASME Code Section XI, Article IWA-2232, Regulatory Guide 1.150 and l 10CFR50.55a(g)(6)(ii)(A). The examination scope included 100% of the RPV shell welds (ASME Code Section XI Table IWB-2500-1, Category B-A), all 8 Reactor Nozzle to Vessel welds and Inner Radius sections (Category B-D), all 8 Nozzle-to-Safe-end welds (Category B-F), and the Pipe-to Safe-end weld on the A Loop (Category B-J). The RPV does not have any longitudinal shcIl welds.
Ps98byttrs'980313 doc
l 1
Revisiin 0
/ Page 2 cf 4 BYRON STATION UNIT 2 INSERVICE INSPECTION ;
RELIEF REOUEST NR-27 The B2R07 examinations revealed one minor recordable indications in each Nozzle-to Shell welds RPVN-C and RPVN-E. All indications are within the acceptance criteria of ASME Code Section l
XI, Article IWB-3500.
During the performance of the B2R07 examinations, physical obstructions and geometry prevented UT coverage in excess of 90% of the required volume for the weld WR-29. Full 100% UT coverage was obtained for the Item Bl.10 RPV shcIl welds WR-18 and WR-34. Full 100% UT coverage was obtained for the Item Bl.30 R.PV shell to flange welds WR-7. Additionally, a limited
examination limitation for WR-16 is addressed in Byron Station First Inspection Interval Relief Request NR-1 which was previously approved by the NRC in Augurt 1991. The portion of NR-1 that addressed the examination limitations of weld WR-16 was not affected by 10CFR50.55a(g)(6)(ii)(A).
l ASME Code Section III quality controls were used when designing, fabricating, and installing these welds. In addition, these welds were volumetrically examined during preservice inspections.
Preservice inspection ultrasonic examination of the Byron Station Unit 2 RPV was conducted during the Fall of 1985 and did not reveal any rejectable indications for the Category B-A RPV shell welds.
Preservice examination ultrasonic limitations were addressed in the Byron Station First Inspection Interval Relief Request NR-1. Portions of the previously granted relief request NR-1 for the RPV Shell welds specified for Code item Bl.10, were revoked in 10CFR50.55a(g)(6)(ii)(A) with respect to examination coverages.
BASIS FOR REl,IEF Pursuant to 10 CFR 50.55a(g)(6)(ii)(A)(3), reliefis requested from the augmented requirement to examine l " essentially 100%" of the examination volume of the RPV Circumferential shell weld, RPVC-WR29, on l the basis that the alternative to the examination requirements would provide an acceptable level of quality i
and safety.
l Augmented examination of the subject RPV shell weld was conducted during refuel outage B2R07 i (Spring 1998). During this examination, physical obstructions and geometry prevented ultrason;c coverage in execss of 90% of the regnired volume. The examination of the Lower Shell Course-to-l Dutchman weld, RPVC-WR29, is restricted by six (6) core barrel locating lugs welded to the inner i surface of the vessel approximately 4 inches above the weld (See Figure 1). These lugs obstruct the l automated UT inspection tool from examining the code required volume of the weld below each lug (156 ). The FTI "URSULA" tool has a 6 degree movement arm and the physical size of the lugs and the " yaw" joint of the tool prevented scanning below the lugs back into the weld and surrounding base metal. All weld metal can be examined from both sides where access is available
- between the lugs (204 ). Examinations for perpendicular and parallel reflectors covered areas 4
accounting for 57% of the weld metal and heat affected zone. Similarly,57% or the weld metal can be examined for transverse reflectors from two opposing directions. Examination of the welds from Pc98byltra 980313 doc
. . - _ _ -. . =. -_. -. - . . . - -
/ Revisitn 0 Page 3 cf 4 BYRON STATION UNIT 2 INSERVICE INSPECTION REI,IEF REOUEST NR-27 the outer surface of the vessel is not practicable due to the structural concrete surrounding the vessel. The annulus between the vessel and the structural concrete does not allow for even remote ultrasonic techniques to be employed. To achieve 100% ultrasonic examination coverage of this weld would require redesign and refabrication of the RPV to climinate the core barrel lower lugs.
For the weld referenced above, the probability of a flaw occurring only in one of the areas not being examined is extremely small. Most future indications of significant size should be found by the examination of the weld as it is currently performed.
PROPOSED ALTERNATE EXAMINATION The ultrasonic examination of the RPV was performed to the maximum extent possible. No alternative volumetric examination is proposed to examine the areas not scanned due to obstructions or geometric constraints.
VT-1 inspection was conducted on the weld and heat affected zore from the inside clad surface utilizing a submersible robot during refuel outage B2R07. Additionally, a VT-2 examination during system pressure testing per Category B-P is performed on the RPV each refueling outage to verify leaktight integrity of these welds.
JUSTIFICATION The Code required volumetric c3 ,tination has been completed to the maximum extent practical using ultrasonic examination techniques. The RPV examinations are conducted using an automated technique from the inside diameter of the vessel. Access to allow inspection from the outer surface (i.e., shell side) of these welds is restricted due to the structural concrete structure surrounding the vessel.
Reasonable assurance of the continued inservice structural integrity of the subject welds is achieved without performing a complete Code examination. The weld has received visual examinations (i.e.,
VT-1 and VT-2) to visually verify the integrity of the weld. Additionally, leakage during operations would be detected by the required shiftly monitoring of the water inventory of the reactor cavity sump.
Compliance with the applicable Code requirements can only be accomplished by redesigning and refabricating the RPV and/or building structure surrounding the vessel. Byron Station believes this course of action is a hardship without a compensating increase in the level of quality and safety.
r PERIOD FOR WHICH RELIEF IS REOUESTED l
Reliefis requested for the first 10-year inspection interval for Byron Station Unit 2.
l
- l. Pn98byttrs'980313. doc l
I i
. - . . . . -. . . ~, . _ _ . _ - .
/ Revision 0 Page 4 of 4 BYRON STATION UNIT 2 INSERVICE INSPECTION RELIEF REOUEST NR-27
=204" Cavity Diameter
- 4 '
[ :
=191" Reactor Diameter BMT(1)=8.625*
Core Support Lua Detail CONCRETE ; l BUILDING '
b STRUCTURE E
BMT(1)/2
/ 1.50" $u l
1 2.1r
[ s
(
BMT(2)/2 BMT = Base Metal Thickness
=8.0" Betweei : :
(--> = code volume !
RPV and r BMT(2)=5.625' Transducer Package Unobstructed Scan Area Reactor Vessel Shell l Core Support Lug , ,
x; igm $4& q
\ .
p j
\
l Exam Coverage \
l Between Core Support
- Lugs for Reflectors Oriented Transverse to '
the Weld Obstructed Scan Area (Below Lugs) i 4
Pf98byttct980313.d.x:
Revisi:n 0 Page 1 cf 4 BYRON STATION UNIT 2
. 19.ERVICE INSPECTION RELIEF REOUEST NR-28 COMPONENT IDENTIFICATION 1
Code Class: 1
Reference:
IWB-2500, Table IWB-2500-1 Examination Category: B-A Item Number: Bl.11
Description:
Volumetric Examination of Reactor Pressure Vessel Circumferential Shell Weld Component Numbers: RPVC-WR29 Drawing Numbers: 2RPV-1-ISI (Unit 2) l CODE REOUIREMENT Table IWB-2500-1, Examination Category B-A, item Numbers Bl.11 require a 100% volumetric examination of the Reactor Pressure Vessel Circumferential Shell welds as detailed in Figure IWB-2500-1 CODE REOUIREMENTS FROM WIIICII RELIEF IS REOUESTED l
Reliefis requested from the examination coverage requirements of Figure IWB-2500-1.
IIISTORY Byron Station, during refuel outage B2R07, conducted ultrasonic examinations of the Byron Station Unit 2 Reactor Pressure Vessel (RPV). This was the last refuel outage of the third period of the First Inservice Inspection Interval and occurred in March and April 1998. Framatome Technologies l Inc. (FTI) was contracted to perform the examinations with their state-of-the-art "URSULA"
- manipulator and their "ACCUSONEX" Ultrasonic Test (UT) system. The examinations were performed in accordance with the requirements in ASME Code Section XI. Article IWA-2232, Regulatory Guide 1.150 and 10CFR50.55a(g)(6)(ii)(A). The examination scope included 100% of l the reactor shell welds (ASME Code Section XI Table IWB-2500-1, Category B-A), all 8 Reactor Nozzle to Vessel welds and Inner P;idius sections (Category B-D), all 8 Nozzle-to-Safe-end welds I (Category B-F), and the Pipe-to Safe <nd weld on the A Loop (Category B-J). The RPV does not have any longitudinal shcIl welds.
He B2R07 examinations revealed one minor recordable indications in each Nozzle-to Shell welds RPVN-C and RPVN-E. All indications are within the acceptance criteria of ASME Code Section XI, Article IWB-3500.
P"98byttn 980313. doc
l .
Revisi:n 0 Page 2 of 4 l
l , BYRON STATION UNIT 2 INSERVICE INSPECTION l
REl.lEF REOUEST NR-28 l
During the performance of the B2R07 examinations, physical obstructions and geometry prevented I UT coverage in excess of 90% of the required volume for the weld WR-29. Full 100% UT coverage was obtained for the item Bl.10 RPV shell welds WR-18 and WR-34. Full 100% UT coverage was obtained for the item Bl.30 RPV shell to %nge welds WR-7. Additionally, limited amount of examination coverage was attained for item Bl.20 RPV lower head weld WR-16. The l examination limitation for WR-16 is addressed in Byron Station First Inspection Interval Relief l Request NR 1 which was previously approved by the NRC in August 1991. The portion of NR-1 that addressed the examination limitations of weld WR-16 was not affected by 10CFR50.55a(g)(6)(ii)(A).
ASME Code Section 111 quality controls were used when designing, fabricatmg, and installing these l welds. In addition, these welds were volumetrically examined during presenice inspections.
Preservice inspection ultrasonic examination of the Byron Station Unit 2 RPV was conducted during the Fall of 1985 and did not reveal any rejectable indications ror the Category B-A RPV shell welds.
Preservice examination ultrasonic limitations were addressed in the Byron Station First inspection
! Interval Relief Request NR-1. Portions of previously granted relief request NR-1 for the RPV Shell welds specified for Code Item Bl.10, were revoked in 10CFR50.55a(g)(6)(ii)(A) with respect to l examination coverages.
i BASIS FOR RELIEF Pursuant to 10 CFR 50.55a(g)(5)(iii), reliefis requested from the ASME Code Item Bl.11 requirement to examine " essentially 100%" of the examination volume of the RPV circumferential shcIl weld, RPVC-WR29, on the basis that conformance with the Code requirements is impractical.
Volumetric examination of the subject RPV shell weld was conducted during refuel outage B2R07 l (Spring 1998). During this examination, physical obstructions and geometry prevented ultrasonic i
coverage in excess of 90% of the required volume. The examination of the Lower Shell Course-to-Dutchman weld, RPVC-WR29, is restricted by six (6) core barrel locating lugs welded to the inner surface of the vessel approximately 4 inches above the weld (See Figure 1). These lugs obstruct the automated UT inspection tool from examining the code required volume of the weld below each lug (156 ). The FTl "URSULA" tool has a 6 degree movement arm and the physical size of the lugs and the " yaw" joint of the tool prevented scanning below the lugs back into the weld and surrounding base metal. All weld metal can be examined from both sides where access is available i between the lugs (204 ). Examinations for perpendicular and parallel reflectors covered areas I
accounting for 57% of the weld metal and heat affected zone. Similarly,57% of the weld metal can be examined for transverse reficctors from two opposing directions. Examination of the welds from 1
the outer surface of the vessel is not practicable due to the structural concrete surrounding the vessel. Removal the obstruction (structural concrete) would require extensive structural modifications and the manhour/ exposure expenditures is inpracticable .The annulus between the vessel and the structural concrete does not allow for any existing remote ultrasonic techniques to be employed. He development of new sophisticated tooling to examine the weld frc,m the outer surface would result in only marginal increases in the examination coverages.
1 4
P.198byttru 980313 doc
1 Revisi:n 0 Page 3 of 4 i BYRON STATION UNIT 2
. INSERVICE INSPECTION !
RELIEF REOUEST NR-28 l
1 l
To achieve 100% ultrasonic examination coverage from the inner surface of this weld would require redesign and refabrication of the RPV to eliminate the core barrel lower lugs l or reposition th e weld relative to the lugs.
For the weld referenced above, the probability of a flaw occurring only in one of the areas not being examined is extremely small. Most future indications of significant size should be found by the examination of the weld as it is currently performed.
PROPOSED ALTERNATE EXAMINATION l l
The ultrasonic examination of the RPV was performed to the maximum extent possible. No l alternative volumetric exalnination is proposed to examine the areas not scanned due to obstructions or geometric constraints. l l
VT-1 inspection was conducted on the weld and heat affected zone from the inside clad surface utilizing a submersible robot during the Byron Station Refuel Outage B2R07. Additionally, a VT-2 examination during system pressure testing per Category B-P is performed on the Reactor Pressure Vessel cach refueling outage to verify leaktight integrity of these welds. !
JUSTIFICATION The Code requi ed volumetric examination has been completed to the maximum extent practical using ultrasonic examination techniques. The RPV examinations are conducted using an automated technique from the inside diameter of the vessel. Access to allow inspection from the outside diameter (i.e., shell side) of this weld is restricted due to the structural concrete structure surrounding the vessel.
Reasonable assurance of the continued inservice structural integrity of the subject weld is achieved without performing a complete Code examination. The weld has received visual examinations j (i.e.,VT-1 and VT-2) to visually verify the integrity of the weld. Additionally, leakage during operations would be detected by the required shiftly monitoring of the water inventory of the reactor cavity sump.
t l
l Compliance with the applicable Code requirements can only be accomplished by redesigning and refabricating the Reactor Pressure Vessel and/or buildina structure surroundi.ig the vessel. Byron Station believes this course of action is a hardship without a compensating increase in the level of quality and safety.
PERIOD FOR WHICH RELIEF IS REOUESTED Reliefis requested for the first 10 year inspection interval for Byron Station Unit 2.
P.^98tgitri 980313 doc 1
9 Revisi:n 0 P:ge 4 of 4 BYRON STATION UNIT 2 INSERVICE INSPECTION RELIEF REOUEST NR-28 Figure 1 1 (Drawing not to scale) l
=204* Cavity Diameter , 1 w .
l
[ :
=191" Reactor Diameter BMT (1)=8.625' Core Support Lua Detail CONCRETE :
l BUILDING l b
STRUCTURE E
BMT
/ 1.50' $v I 2.14' 4
I
( BMT (2)/2 BMT = Base Metal Thickness
=8.0" Betweel :
(-) = Code volume RPV anri e >
BMT (2)=5.625" Transducer Package n stmded Scar Ama Reactor Vessel i I
Shell Core Support Lug s' VU %'Q">'yJ ,
l
\
\\>s R/l Exam Coverage 'N Between Core Support N Lugs for Reflectors Oriented Transverse to
\
/[
the Weld Obstructed Scan Area (Below Lugs)
PPS8byltn 980313. doc