ML20207L596

Safety Evaluation Concluding That Code Requirements,Which Require 100 Percent Volumetric Exam of RPV flange-to-shell, Impractical to Perform to Extent Required & That Alternative Provide Reasonable Assurance of Structural Integrity

ML20207L596
Person / Time
Site:	Millstone
Issue date:	02/22/1999
From:	NRC (Affiliation Not Assigned)
To:
Shared Package
ML20207L583	List: ML20207L579 ML20207L596
References
NUDOCS 9903180194
Download: ML20207L596 (6)

Text

--

:==: 2 ====

= - - -

m = :.:,; : : = 3 3 3 -

ne:

,4 y UNITED STATES i g , NUCLEAR REGULATORY COMMISSION WAeNINGTON, e.C. SDOOHOM '

SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION REQUEST FOR RELIEF FROM THE REQUIREMENTS OF THE ASME CODE NORTHEAST NUCLEAR ENERGY COMPANY t

MIL'LSTONE NUCLEAR POWER STATION. UNIT NO. 3 DOCKET NO. 50-423

1.0 INTRODUCTION

The Technical Specifications for Millstone Unit 3, state that the inservice inspection and testing 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 Code (ASME Code) and applicable addenda, as required by Title 10 of the Code of Federal Reaulations (10 CFR), Part 50, Section 50.55a. Section 50.55a(a)(3) states that attematives to the requirements of paragraph (g) may be used, when authorized by the NRC, if the proposed altamatives would provide an acceptable level of quality and safety, or (ii) if compliance with the Code 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 (including supports) shall meet the requirements, except the design and access provisions and the preservice 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 I

. 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) on the date 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 Millstone Unit 3 fo.- the first inservice inspection intervalis the 1983 Edition through the Summer 1983 Addenda. 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. i Pursuant to 10 CFR 50.55a(g)(5), if the licensee determines that conformance with an l' 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 i

determination, pursuant to 10 CFR 50.55a(g)(6)(i), the Commission may grant relief and may impose, altemative requirements that are determined to be authorized by law, will not endanger

~

9903190194 990222 ENCLOSURE PDR ADOCK 05000423 P PDR 1

~ - _ -

~. .

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 on the facility.

2.0 EVALUATION By letter dated September 23,1998, Northeast Nuclear Energy Company (the licensee) requested relief, pursuant to 10 CFR 50.55a, from the requirements of the ASME Code,Section XI for Millstone Unit 3. The Idaho National Engineering and Environmental Laboratory (INEEL) has evaluated the information provided by the licensee in support of the relief request.

Based on the results of the review, the staff adopts the contractor's conclusions and recommendations presented in the Technical Letter Report attached. The basis for adopting the contractor's recommendations are summarized below.

The ASME Code,Section XI, Examination Category B-A, item B1.30 requires 100 percent

- volumetric examination of the reactor pressure vessel flange-to-shell weld, as defined in Figure IWB-2500-4, each inspection interval.

In accordance with 10 CFR 50.55a(g)(5)(iii), the licensee requested relief from the Code-required volumetric examination of flange-to shell weld numbers 101-121. The licensee was able to examine approximately 70 percent of the Code-required cumulative volume. Complete examination coverage is restricted by geometric surface condition (flange wall taper) that makes 100 percent volumetric examination impractical for this weld. To gain access for examination, the reactor pressure vessel would require design modifications. Imposition of this requirement would create a significant burden on the licensee. In addition, other reactor pressure vessel shell welds have been examined to the extent required by the Code.

Therefore, any existing pattems of degradation would have been detected by the examinations that were completed and thus a reasonable assurance of structuralintegrity has been  !

provided.

' The staff finds that the licensee's proposed altemative provides reasonable assurance of structuralintegrity and safety for the subject welds. This conclusion is based on the fact that other reactor pressure vessel shell welds have been examined to the extent required by the Code and 70 percent of examination coverage of the subject welds was accomplished. l Therefore, a pattom of degradation, if present, would be detected.

3.0 CONCLUSION

The NRC staff concludes that the Code requirements, which require a 100 percent volumetric examination of the reactor pressure vessel flange to-shell weld, are impractical to perform to the extent required by the Code and that the proposed altemative provides reasonable assurance of structuralintegrity and safety. Therefore, the request for relief is granted 1

- .:.== ..:: -^ :-^':::: .:? ~ ".~ ~ ~~ "

1 3-pursuant to 10 CFR 50.55a(g)(6)(i). The relief granted is authorized by law and will not endanger life or property or the common defense and security and is othenvise in the public interest giving due consideration to the burden upon the licensee that could result if the requirements were imposed on the facility.

PrincipalReviewer: T.McLellan Date: February 22, 1999 l

l i

e

. - - - ~ - - - - - . . . - - _ _ . ,

TECHNICAL LETTER REPORT i i

ON FIRST 10 YEAR INTERVAL INSERVICE INSPECTION l REQUEST FOR RFl_IFF NO. IR-27 '

f.QB NORTHEAST NUCLEAR ENERGY COMPANY MILLSTONE NUCLEAR POWER STATION. UNIT 3 -

DOCKET NUMBER: 50-423

1. INTRODUCTION By letter dated September 23,1998, the licensee, Northeast Nuclear Energy Company, submitted Request for Relief No. IR 27 seeking relief from the requirements of the ASME Code,Section XI, for the Millstone Nuclear Power Station, Unit 3, first 10-year inservice inspection (ISI) interval. The Idaho National Engineering and Environmental Laboratory (INEEL) staff's evaluation of this request for relief is in the following section. 1 l

2. EVALUATION The information provided by Northeast Nuclear Energy Company in support of the ,

request for relief from Code requirements has been evaluated and the basis for disposition is documented below. The Code of record for the Millstone Nuclear Power Station, Unit 3, first 10-year ISI interval, which began April 23,1986, is the 1983 Edition through Summer 1983 Addenda of Section XI of the ASME Boiler and Pressure Vessel Code.

Raouest for Relief No. IR 27. Examination Cateoorv B A. Item B1.30. Reactor Pressure Vessel Shelf-to-Flance Wald Code Reauirement: Examination Category B-A, item B1.30 requires 100% volumetric examination of the reactor pressure vessel (RPV) shell-to-flange weld, as defined in Figure IWB 2500-4, each inspection interval.

Licensee's Code Relief Raouest: In accordance with 10 CFR 50.55a(g)(5)(iii), the licensee requested relief from the Code-required volumetric examination of shell-to-ATTACHMENT 2

- . - _ ,,. .=- -- .. .- -..

er

" l 2

b .

- 4 flange Weld 101-121. The licensee was able to examine approximately 70% of the Code-required cumulative volume. l Licensee's Basis for Reauestina Relief (as stated):

1 "In performing the 1" 10 year Interval Reactor Pressure Vessel Exam, the best available technology was utilized in performing a volumetric exam of the vessel from the I.D. Geometric configuration limits the volumetric examination of Weld No. 101-121, Flange - to - Shell, as shown in Attachment 2'.

Specifically, volumetric examination requires that the inside (ID) and outside (OD) surfaces of the examination area must be relatively parallel in order to provide meaningful test results. The geometric configuration of the Shell- to -

Flange weld (101-121) includes tapers on both the ID and OD of the flange side surface. This taper results in a non-parallel surface configuration, thereby limiting meaningful examination to the Shell side of the weld.

"The limitations caused by the surface taper when performing the exams on weld 101-121 from the I.D. would also be similarly realized when performing a ultrasonic exam from the O.D. Therefore, no additional benefit would be realized from performing a volumetric exam from the O.D. of the vessel on this weld.

l l

"The subject weld received both volumetric examination by radiography and surface examinations, in accordance with ASME Section lil requirements during the fabrication process. This provides adequate assurance of the structural integrity of the weld."

Licensee's Prooosed Alternative Examination (as stated):

"1) The subject weld received a volumetric exam (utilizing best available technology) on the accessible portions (approximately 70 percent) in I accordance with Section XI (IWB-2500-1).

"2) Inservice system leakage test will be performed per Code Case N-498-1 as granted by the NRC (Correspondence dated January 18,1995 TAC NOS.

M90685, M90841, M91103, M90580)."

Evaluation: The Code requires 100% volumetric examination of the subject RPV shell to-flange weld. However, complete examination coverage is restricted by geometric surface conditions (flange wall taper) that make 100% volumetric examination impractical for this weld. To gain access for examination, the RPV would require design modifications. Imposition of this requirement would create a significant burden on the licensee.

1. Attachments included with the licensee's original submittal are not included in this report. .

m. _.

k 3 j

~

The licensee has examined the subject weld to the extent practical, attaining approximately 70% of the cumulative Code-required coverage. In addition, other RPV shell welds have been examined to the extent required by the Code. Therefore, any existing patterns of degradation would have been detected by the examinations that were completed and reasonable assurance of structuralintegrity has been provided.

3. CONCLUSION Based on the impracticality of meeting the Code examination requirements for the RPV shell to-flange weld, and the reasonable assurance provided by the examinations that were completed on this and other welds, it is recommended that relief be granted pursuant to 10 CFR 50.55a(g)(6)(i). l I

l

,