ML20199G705
| ML20199G705 | |
| Person / Time | |
|---|---|
| Site: | Monticello  |
| Issue date: | 11/19/1997 |
| From: | NRC (Affiliation Not Assigned) |
| To: | |
| Shared Package | |
| ML20199G697 | List: |
| References | |
| NUDOCS 9711250258 | |
| Download: ML20199G705 (6) | |
Text
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- UNITED STATES j
,j* NUCLEAR REGULATORY COMMISSION WASHINGTON. D.C. speeH001
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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION E
THIRD 10 YEAR INSERVICE INSPECTION INTERVAL ,
EllEF REOUEST NO. 8 EDB NORTHERN STATES POWER COMPANY -
MONTICELLO NUCLEAR GENERATING PLANT DOCKET NUMBER- 50 263
1.0 INTRODUCTION
The Technical Specifications (TS) for Monticello Nuclear Generating Plant state that the inservice inspection of the American Society of Mechanical Engineers (ASME) Code Class 1. 2. and 3 components shall be performed in accordance with Section XI of the ASME Boiler and Pressure Vessel (B&PV) Code and applicable addenda as required by 10 CFR 50.55a(g). except where specific written relief has been granted by the Commission )ursuant to 10 CFR 50.55a(g)(6)(1). The 10 CFR 50.55a(a)(3) states tlat alternatives to the requirements of paragraph (g) may be used, when authorized by the NRC. if (1) the proposed _ alternatives would )rovide an acceptable level of quality and safety or (ii) compliance with t1e s)ecified requirements would result in hardship or unusual difficulties witlout 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 (including supports) shall meet the requirements, except the design and access orovisions and the ]re-service examination requirements, set forth in the ASME Code.Section XI.
- Rules for Inservice Inspection of Nuclear Power Plant Components." to the extent practical within the limitations of design.
geometry, and materials of construction of the components. The regulations require that inservice examination of components and system pressure tests conducted during the first 10 year interval and subsequent intervals comply 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 start of the 120 month interval. subject to the limitations and modifications listed therein. The applicable edition of Section XI of the ASME Code for the Monticello Nuclear Generating Plant third 10-year inservice inspection interval is the 1989 Edition Addenaa.
Enclosure 9711250258 971119 PDR ADOCK 05000263 0 pan
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Pursuant to 10 CFR 50.55a(g)(5), if the licensee determines that conformance ;
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 !
Code requirement. After evaluation of the determination, pursuant to i 10 CFR 50.55a(g)(6)(1), the Commission may grant relief and.may impose i alternative re '
endanger life,quirements thatcomon property, or the are determined defense and to security, be authorized and areby law, will not otherwise in the public interest, giving due consideration to the burden upon the .
licensee that could result if the requirements-were imposed.
By letter dated March 14. 1996. Northern States Power Company (the licensee) ;
submitted to the NRC its third 10 year inservice inspection interval program plan alternative to use existing calibration blocks contained in Request for Relief No. 8 for the Monticello Nuclear Generating Plant. The licensee also provided additional information in its letters dated January 22 and April 29, 1997.
2.0 EVALUATION The staff, with technical assistance from its contractor, the Idaho National Engineering and Environmental Laboratory (INEEL). has evaluated the ,
information provided by the licensee in support of its third 10-year inservice ,
ins No.pection 8 for theinterval program Monticello kuclear plan alternativePlant Generating contained dated March in Request 14,1996, for Relief as su)plemented January 22 and April 29, 1997. Based on the information su)mitted.- the staff adopts its contractor's conclusion and recommendation presented in the attached Technical letter Report (TLR) by INEEL.
3.0- CONCLUSIONS The staff has reviewed the licensee's submittal and concludes that requiring the licensee to fabricate new calibration blocks in lieu of using existing calibration blocks will result in a burden without a compensating increase in i the level of quality and safety. The 11 wnsee has proposed to perform velocity and attenuation checks to verify the acoustic similarities of the calibration blocks and materials being examined. Therefore, the licensee's proposed 41ternative is authorized pursuant to 10 CFR 50.55a(a)(3)(11).
1 Principal contributor: T. K. McLellan ,
Date: November 19, 1997 L
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l TlCHNICAL LETTER REPORT THIRD 10-YEAR INSERVICE INSPECTION INTERVAL RELIEF RE00EST NO. 8 NORTHERN STATES POWER COMPANY MONTICELLO NUCLEAR GENERATING PLANT i DOCKET NUMBER: 50 263 i
1.0 INTRODUCTION
By letter dated March 14. 1996. Northern States Power Company (the
- licensee) submitted Request for Relief No. 8. In subsequent letters dated January 22, 1997, and April 29,1997, the licensee provided clarifying information, and made commitments for alternative requirements deemed a)propriate by the Nuclear Regulatory Commission (NRC) staff. The Idalo National Engineering and Environmental Laboratory (INEEL) under a contract with the NRC, has evaluated the licensee'ssubjectsubmittals.
2.0 EVALUATION
.The Code of record for third 10 year inservice inspection interval at the Monticello Nuclear Generating Plant is the 1989 Edition of the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code Section XI. The information provided by the licensee in support of the request for relief from Code requirements has been ,
evaluated and the basis for disposition is documented below.
2.1 Code Reauirement ASME Section XI, Article 4 of Section V Paragraph T-441.1.2.1 specifies ,
the code requirements for ultrasonic calibration block material for vessels greater than 2 inches in thickness, It states that the ultrasonic calibration block (s) be fabricated from one of the following:
(a) Nozzle drop out from the component: '
(b) A component prolongation: i (c) Material of the same material specification, product form, and heat '
treatment condition as of the material being joined.
Appendix 111 of Section XI specifies the code requirements for ultrasonic calibration block material for examination of vessel welds
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2 less than or equal to 2 inches in thickness and all pip og welds, it :
states the following requirements for the ultrasonic calibration block (s):
(a) The calibration block for similar metal welds shall be fabricated from one of the materials specified for the piping being joined by the weld.
(b) Calibration blocks for dissimilar metal welds shall be fabricated from the material specified for the side of the weld from which the examination will be conducted. If the examination will be conducted from both sides, calibration reflectors shall be provided in both materials.
(c) Where examination is to be >erformed from only one side of the joint, the calibration bloc ( material shall be of the same specification as the material on that side of the joint.
(d) If material of the same specification is not available, material of similar chemical analysis. tensile properties, and metallurgical structure may be used.
(e) Where the component material is clad, the block shall be clad by the same welding procedure as the production part. Where the automatic method is impractical, deposition of the clad shall be by the manual method.
2.2 Licensee's Proposed Alternative Pursuant to 10 CFR 50.55a(a)(3)(ii), the licensee proposed the followir alternative to the above code requirements for ultrasonic calibration block material:
" Existing calibration blocks will be used as is. When using the existing calibration blocks that lack the appropriate documentation a comparison will be made between the acoustical properties (i.e.,
velocity and attenuation of the calibration block and the material being examined), This comparison will be done once, prior to the use of the calibration block, to ensure that the sensitivities are sufficient to find existing flaws in corresponding examination volumes. Any calibration blocks obtained in the future will be obtained with documentation to demonstrate compliance with the material specification requirements of ASME Code Section V. Article 4 or Section XI. Appendix 111. as applicable."
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2.3 Licensee's Basis for the ProDosed Alternative (as stated): !
" Documentation requirements existing at the time of fabrication did not '
require traceability to the material's chemical or physical certifications. Existing calibration blocks certification is verified through appropriate P number grouping. The P number grouping provides ;
adequate assurance that the blocks will establish the proper ultrasonic calibration and sensitivity." i "It would be im ractical to fabricate a new set of calibration blocks in order to satisf the documentation requirements of the current Code.
Existing record indicate the appropriate P number grouping, thereby ,
providingccalibrationandsensitivity." adequate assurance that the blocks wil ultrason 3.0 Evaluation Section XI. Appendix Ill and Section V. Article IV of the ASME Code require that calibration blocks be of the same material or a material of similar chemical, tensile, and metallurgical properties. The calibration blocks procured for the Monticello Nuclear Generating Plant were constructed to the 1971 Edition of Section 111, which only required that they be of the same P number grouping.
The existing calibration blocks were fabricct-1 prior to current Code requirements for material selection and documentation. As such, the licensee does not have the calibration block material records required by the current Code. Because the subject calibration blocks met the original Code, requiring the licensee to develop the required ,
documentation or to fabricate new calibration blocks with the required corresponding information would be considered an unnecessary burden.
When using existing calibration blocks that lack the appropriate documentation, it has been determined that a comaarison of acoustical properties (i.e., velocity and attenuation) of t1e calibration block and the material being examined is essential to ensure that the sensitivity and scan angle developed in the calibration block is equivalent to that of the production material. The comparison should be done once prior to the use of the calibration block for the applicable examination areas, This will ensure that a meaningful examination will be obtained.
The existing blocks were deemed acceptable for ultrasonic calibrations-during previous ISI intervals. Therefore, the use of the existing calibration blocks is acceptable provided that the existing calibration blocks are demonstrated to have acoustic properties that are equivalent to the material being examined. As a result, ccQuiring the licensee to develop material records or obtain new calibration blocks will result in a burden without a compensating increase in quality and safety. The ,
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4 licensee pro)oses to verify the acoustic properties of the existing calibration alocks before use. This verification of material acoustic sin.!' tity will provide reasonable assurance that neaningful :
examinations will continue to be obtained.
4.0 CONCLUSION
Requiring the licensee to fabricate new calibration blocks in lieu of using existing calibration blocks will result in a burden without a compensating increase in the level of quality and safety. The licensee has proposed to perform velocity and attenuation checks to verify the acoustic similarities between the calibration blocks and materials being examined. Therefore it is recommended that the proposed alternative be authorized pursuant to 10 CFR 50.55a(a)(3)(11).
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