ML20137D496

Safety Evaluation of Second 10-year Interval Inservice Insp Program Plan Requests for Relief CR-17 & CR-18 Commonwealth Edison Co,Lasalle County Station,Units 1 & 2

ML20137D496
Person / Time
Site:	LaSalle
Issue date:	03/24/1997
From:	NRC (Affiliation Not Assigned)
To:
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ML20137D488	List: ML20137D484 ML20137D496
References
NUDOCS 9703260183
Download: ML20137D496 (6)

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NUCLEAR RESULATORY COMMISSION WASHINGTON, D.C. 30586-0001 i

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l SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION j OF THE SECOND 10-YEAR INTERVAL INSERVICE INSPECTION PROGRAM PLAN l REQUESTS FOR RELIEF NOS. CR-17 AND CR-18 l COMONWEALTH EDISON COMPANY L

LASALLE COUNTY STATION. UNITS 1 AND 2 DOCKET NOS. 50-373 AND 50-374

1.0 INTRODUCTION

The Technical Specifications (TS) for LaSalle County Station, Units I and 2, state that the inservice inspection (ISI) of the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code (Code) Class 1, 2 and 3 components shall be performed in accordance with Section XI of the ASME L

Code and applicable Addenda as required.by 10 CFR 50.55a(g), except where specific written relief has been granted by the Commission pursuant to 10 CFR 1 50.55a(g)(6)(1). In 10 CFR 50.55a(a)(3) it states that alternatives to'the I requirements of paragraph (g) may be used, when authorized by the NRC, if (i) the proposed alternatives would provide an acceptable level.of quality and safety or (ii) compliance with the specified requirements would result in  !

hardship or unusual difficulty without a compensating increase in the level of '

quality and safety.

Pursuant to 10 CFR 50,55a(g)(4), ASME Code Class 1, 2 and 3 components I (including supports) shall meet the requirements, except the design and access provisions and the preservice examination requirements, set forth in the ASME l

Code,Section XI, " Rules for Inservice Inspection of Nuclear Power Plant l Components," to the extent practical within the limitations of design,

! geometry, and materials of construction of the components. The regulations i require that inservice examination of components and system pressure tests

! conducted during the first 10-year interval and subsequent intervals comply 1 l with the requirements in the latest edition and addenda of Section XI of the  !

ASME Code incorporated by reference. in 10 CFR 50.55a(b) 12 months prior to the l start of the 120-month interval, subject to the limitations and modifications l listed therein. The applicable edition of Section XI of the M ME Code for the l LaSalle County Station, Units 1 and 2, second 10-year ISI interval is the 1989 i l Edition. The components (including supports) may meet the requirements set forth in subsequent editions and addenda of the ASME Code incorporated by  ;

reference in 10 CFR 50.55a(b) subject to the limitations and modifications  ;

listed therein and subject to Commission approval.  ;

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, j j ENCLOSURE 9703260183 970324 PDR ADOCK 05000373 G PDR

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l Pursuant to 10 CFR 50.55a(g)(5), if the licensee determines that conformance i with an examination requirement of Section XI of the ASME Code is not practical for its facility, information shall be submitted to the Commission in support of that determination and a request made for. relief from the ASME  !

e Code requirement. After evaluation of the determination, pursuant to 10 CFR  !

50.55a(g)(6)(1), the Commission may grant relief and may impose alternative l' requirements that are determined to be authorized by law, will not endanger life, property, or the common defense and security, and are otherwise in the  !

public interest, giving due consideration to the burden upon the licensee that .

could result if the requirements were imposed.  ;

In a letter dated September 4,1996, Commonwealth Edison Company (Comed, the ,

l licensee), submitted to the NRC its second 10-year interval ISI program relief l l requests CR-17 and CR-18 for the LaSalle County Station, Units 1 and 2. The -

i licensee requested relief from performing Code-required surface examinations of integrally welded attachments due to one of the weld surfaces being l inaccessible. The staff has reviewed and evaluated the licensee's request and ,

! the supporting information for the LaSalle County Station, Units 1 and 2. '

2.0 DISCUSSION j A. -LICENSEE'S RELIEF REQUEST NO. CR-17:

CONP0NENT IDENTIFICATION j

Description:

Integrally Welded Attachments to Piping (Reference Tables CR-17-01 and CR-17-02 of licensee's relief request)

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l. Code: 1989 ASME Code,Section XI, Figures IWB-2500-15 and {

IWC-2500-5(a) Examination Category B-K-1 and C-C, Item i Nos. B10.10 and C3.20, Class 1 and 2 ,

i EXAMINATION REQUIREMENT l Section XI, Table IWB-2500-1, Examination B-K-1, Item B10.10 requires a surface examination of the welds and adjacent base metal as defined by Figure IWB-2500-15.

Section XI, Table IWC-2500-1, Examination C-C, Item C3.20 requires a surface examination of the welds and adjacent base metal as defined by Figure IWC-2500-5(a).

LICENSEE'S BASIS FOR RELIEF: (As stated)

" Pursuant to 10 CFR 50.55a(a)(3)(ii), relief is requested on the basis that compliance with the Code requirement would result in hardship or unusual difficulty without compensating increase in the level of quality and safety.

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The subject welded attachments are of the T joint double bevel groove weld design such that one of the weld surfaces, surface area C-D, is located inside the flued head penetration assembly.

The configuration of these components are shown on Figures CR-17-01 and 02. A surface examination on both surface areas A-B and C-D is required on components in categories B-K-1 or C-C.

Due to limitations imposed by the design and construction of these 1 penetration assemblies, the Code-required surface examination cannot be performed on surface area C-D. Access to surface area C-D from the outside (closed) end of the penetration assembly is not possible due to the presence of the integral attachment.

Additionally, the distance to the integral attachment from the ,

inside (open) end of the penetration assembly, coupled with the '

limited clearance between the process pipe and the penetration sleeve prevents the performance of the required surface examination on surface area C-D. Typically, this distance is between 54 and 78 inches. Table CR-17-01 and -02 provide additional detailed dimensions for the subject penetration assemblies. Each of the components listed on Table CR-17-01 and

-02 are part of assemblies which penetrate primary containment, secondary contair. ment, or walls. To satisfy the Code requirement, redesign of the piping and/or penetrations to provide access to l the subject surface areas would be required. Significant  !

engineering, installation costs, and radiation exposure would be incurred by LaSalle station to implement these modifications without a compensating increase in the level of quality or safety because (1) the Code-required surface examination on surface area A-B, and (2) the periodic VT-2 examinations as required by ASME-Section XI, Categories B-P or C-H will provide reasonable assurance of continued structural integrity of the subject components.

Based on the above reasons, relief is requested from performing the Code-required surface examination on inaccessible surface area C-D for the subject components."

LICENSEE'S PROPOSED ALTERNATE EXAMINATION: (As stated)

"For the reasons previously discussed, alternate examination is impractical for surface area C-D.

However, LaSalle Station will perform a surface examination on the accessible surface area A-B in accordance with the requirements of ASME Section XI Category B-K-1 or C-C. Additionally, a VT-2 visual examination around the annulus of the penetration will be l performed in conjunction with the system pressure tests required l by ASME Section XI, Category B-P or C-H."

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_4-t, EVALUATION i

Relief request CR-17 involves piping penetration assemblies in Class 1 and 2 l piping that penetrate primary and/or secondary containment. The flued head of the penetration assembly has a double bevel groove weld to the piping with a l Tee joint configuration. The requirement of the Code is impractical because the surface area of the weld inside the flued head, identified as C-D in the Code Figures IWB-2500-15 and IWC-2500-5(a), is inaccessible and has inadequate clearance to perform the Code-required surface examination. The licensee l l would need to redesign and modify the penetration assembly to gain access to the surface C-D to meet the examination requirement of the surface C-D. The licensee, however, proposes to perform a VT-2 visual examination around the annulus of the penetration assembly during the system pressure test to ensure that no service induced flaw emanates from the unexamined surface area C-D that penetrates through-wall into the piping pressure boundary. If a service induced flaw were to originate at the surface C-D and penetrate into the opposite surface (containment), such a flaw will be detected by examination of the surface area A-B which is accessible and is currently in the scope of examination. Therefore, granting relief with the imposition of the proposed i alternative to perform a VT-2 visual examination of the annulus of the penetration assembly, along with a surface examination of area A-B, as requested, provides reasonable assurance of operational readiness. ,

B. LICENSEE'S RELIEF RE0 VEST NO. CR-18:

l COMPONENT IDENTIFICATION

Description:

Reactor Vessel Support Skirt to Reactor Vessel Bottom Head Weld Component Numbers, IVS-1 (Unit 1) and IIVS-1 (Unit 2) l l

Code: 1989 ASME Code,Section XI, Figure IWB-2500-13 Examination  !

Category B-H, Item No. B8.10, Class I l EXAMINATION REQUIREMENT Section XI, Table IWB-2500-1, Examinatim Category B-H, Item No. B8.10 ,

requires a surface examination of the weld and the adjacent base metal as I defined by Figure IWB-2500-13.

LICENSEE'S BASIS FOR RELIEF: (As stated)

" Pursuant to 10 CFR 50.55a(a)(3)(1), relief is requested on the  !

basis that the proposed alternatives would provide an acceptable  !

i level of quality and safety.  !

l l The reactor vessel bottom head was constructed with a weld build- I l

up around the circumference of the head that was designed as the attachment point for the reactor vessel support skirt. This weld build-up was machined and heat treated along with the reactor vessel.

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The support skirt is attached to the weld build-up by means of a full penetration butt weld. As can be seen in Figure CR-18-01 and

-02, the design of this weld is such that the Code-required surface examination on surface area C-D of Figure IWB-2500-13 is limited by the short blend radius (1" R for Unit 1, 3" R for Unit

2) and the steep angle formed by the bottom head support skirt that limits access to surface area C-D. Additionally, inspection personnel would be exposed to high radiation field when conducting the Code-required surface examination on surface area C-D. The estimated radiation exposure can be up to 2.4 person-rem for an l inspection team of two (2) persons based on radiation field of 600 mR/ hour for 2-hour examination time. It is further estimated that l an additional 3 person-rem would be incurred by craft support personnel to prepare area C-D for the Code-required surface l examination. The radiation field on the outside of the support skirt is approximately 25 mR/ hour.

Based on dimensions provided on fabrication drawings, a best

, effort ultrasonic examination using a combination of various angle beams, such as 0*, 30*, and/or 45' can be performed from the outside surface of the support skirt. This volumetric examination

, is expected to detect service induced flaws initiated from most of I surface area C-D. The performance of this volumetric examination in conjunction with the performance of the Code-required surface examination on surface area A-B will provide adequate assurance of the structural integrity of the subject weld.

. For these reasons, LaSalle Station requests relief from the ASME l

Section XI, surface examination of surface area C-D of Figure IWB-2500-13."

LICENSEE'S PROPOSED ALTERNATE EXAMINATION: (As stated) l "As an alternate examination to the Code-required surface l examination of surface area C-D, LaSalle Station will perform a l best effort ultrasonic examination of the C-D region from the outside surface of the support skirt. The volumetric examination l frequency will be in accordance with that required by Category B-H, Item B8.10.

The Code-required surface examination of the surface area A-B will l

be performed in accordance with the requirements of Category B-H, Item B8.10."

EVALUATION Relief request CR-18 is applicable to the reactor vessel support skirt to reactor vessel bottom head weld. The configuration of this weld is such that access to the surface area C-D shown in Figure IWB-2500-13 of ASME Code,Section XI, for the required surface examination, is restricted. The licensee l

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Relief request CR-18 is applicable to the reactor vessel support skirt to reactor vessel bottom head weld. The configuration of this weld is such that access to the surface area C-D shown in Figure IWB-2500-13 of ASME Co,de,Section XI, for the required surface examination, is restricted. The licensee proposes to examine the surface C-D ultrasonically by scanning the weld surface A-B outside the skirt, in lieu of the Code-required surface examination of C-D. The ultrasonic examination will detect flaws at the surface C-D which the surface examination would have detected along with any subsurface flaws. Hence, the licensee's proposed surface examination of A-8, along with an ultrasonic examination of surface C-D, provides an acceptable level of quality and safety by providing equivalent protection as that of the Code.

3.0 CONCLUSION

The staff has evaluated the licensee's request for relief CR-17 pertaining to surface examination from one of the surfaces of penetration assemblies. The staff has determined that the requirement of the Code is impractical because the area is inaccessible. Therefore, relief is granted pursuant to 10 CFR 50.55a(g)(6)(1) and an alternative is imposed. The relief granted is authorized by law, will not endanger life, 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 requirement were imposed. The staff has evaluated relief request CR-18 pertaining to examination of the reactor vessel support skirt to reactor vessel bottom head weld and has determined that the proposed alternative provides an acceptable level of quality and safety. Therefore, the proposed alternative in request CR-18 is authorized pursuant to 10 CFR 50.55a(a)(3)(1).

Principal Contributor: P. Patnaik Dated: March 24, 1997 l

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