ML20203E934

SER Accepting Request for Relief from Requirements of 10CFR50.55a(g) for Performing Required Exams for Certain Class 1 Components IAW ASME Boiler & Pressure Vessel Code Section XI for Plant,Unit 3

ML20203E934
Person / Time
Site:	Millstone
Issue date:	02/17/1998
From:	NRC (Affiliation Not Assigned)
To:
Shared Package
ML20203E888	List: ML20203E884 ML20203E934
References
NUDOCS 9802270159
Download: ML20203E934 (5)

Text

. . - _ - - . - - . - - __ - - - - - - - - .- -.

i ,

[. 't

,j UNITED 6TATES NUCLEAR REGULATORY COMMISSION

=

i WASHINGTON, o.C. 3064H001

.....l SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION

RELATED TO A REQUEST FOR REllEF FROM ACMF CODE SECTION XI REQUIREMENTS NORTHEAST NUCLEAR ENERGY COMPANY. ET AL.

MILLSTONE NUCLEAR POWER STATION. 'JNIT NO. 3 DOCKET NO. 50_-(23

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 alternatives to the requirements of paragraph (g) may be used, when authorized by the NRC, if (i) the proposed ahomatives 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 (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 i

limitations of design, geometry, and materials of construction of the components. The regulations require that inservic9 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 5025a(b) on the date 12 months prior to the start of the 120-month interval, subject to tl.a limitations and modifications listed therein. The applicable edition of Section XI of the ASME Code for Millstone Unit 3, for the first inservice inspection (ISI)intervalls the 1983 Edition through the Summer 1983 Addenda. The components (including supports) may I ^-t 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.

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 10 CFR 50.55a(g)(6)(i), the Commission may grant relief and may impose attemative requirements that are determined to be authorized by law, will r,ot 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 on the facility, 9802270159 900217 PDR P

ADOCK 05000423 PDR lhelosae

l l

2-By letter dated July 31,1997 Northeast Nucisar Energy Company (licensee) requested relief from compflance with the 1983 Edition of ASME Code,Section XI, through the Summer 1983 Addenda, Article IWB 2500, which requires a volumetric examination of essentially 100 percent of the wold length for the Reactor Vessel Lower Head circumferential and meridional welds due to permanent obstructions and geometric configuration that limits accessibility to perform the Code examination.

The staff has reviewed and evaluated the licensee's request and supporting information on the proposed aftemative to the Code requirements for Millstone Unit 3, pursuant to the provisions of 10 CFR 50.55a(g)(6)(i).

2.0 DISCUSSION Comnonent Identificatiga Reactor Pressure Vessel Lower Head Welds Code Class: 1, Examination Category: B A Code Reautrement ASME Section XI,1983 Edition through the Summer 1983 Addenda, Artic e IWB 2500, requires a I volumetric examinat.'on of essentially 100 percent (l.a., greater than 90 percent) of the weld length for the following items:

ligm Descriotion B1.21 Lower Head Circumferential Welds B1.22 Lower Head Meridional Welds Licensee's Code Rollef Re_quait The licensee requested the following (as stated):

Pursuant to 10 CFR 50.55a(g)(5)(iii), relief is requested from performing the inservice volumetric examination of the inaccessible portion of the subject Welds.

Licensee's Basis for Rtguestino Rollsf The licenses provided the following basis for the relief request (as stated):

In performing the 1st 10 year Interval Reactor Pressure Vessel Exam, the best available technology was uulized in performing a volumetric exam of the vessel from the I.D.

(inside diameter). Geometric configuration and permanent obstructions limit the volumetric examination of the following listed welds.

m. '

3 Code item No. Wald Code Coversoe B1.21 Torus to-Dollar Plate (102-151)* 71 %

B1.22 Peel Segment at 0 degree (101 154A)* Bi%

B1.22 Peel Segment at 90 degrees (101 154B)* 87 %

B1.22 Peel Segment at 180 degrees (101 154C)* 73 %

B1.22 Peel Segment at 270 degrees (101 154D)* 89 %

• Note: See Figure A 1 (Attachment 2) for weld identification (from the licensee's July 31,1997, letter),

1 Appendix F " EXAMINATION AREA COVERAGE REPORT FOR MILLSTONE NUCLEAR POWER STATION, UNIT 3, REACTOR PRESSURE VESSEL WELDS (Attachment 3)

[from the licensee's July 31,1997, letter) provides details for the weld examination data in question.

The limitations caused by the instrument tubes when performing the exams on welds 102151,101 154A,101 1548,101 154C, and 101 154D, from the I.D. would also be similarly realized when ,mrforming [an) ultrasonic examination from the O.D. [outside diameter). Therefore, minimal benefit would be realized from performing a volumetric exam from the O.D. of the vessel on these welds.

Subsequently an ALARA [as low as is reasonably achievable) Review was perforrr.ed, taking into account that staging and insulation removal would be involved in performing these O.D. exams. The results are shown below:

Igsk Estimated Estimated Man-Hours Man-Rem Installinspeetion Platform 30 6 Install / Remove Staging 100 20 Remove / Replace Insulation 80 16 Weld Preparation 30 6 Weld inspection 35 7 Total: 275 55'

• Based on 200 mrem /hr

l' 4

1 The rewts of this ALARA review show that the performance of manual O.D. exams 4

wou.'i provide an undue hardship, for a minimal gain in code coverage.

i The subject welds received both volumetric examination by radiography and surface examinations, in accordance with ASME Section lil requirements during the fabrication i process. This provides adequate assurance of the structuralIntegrity of the welds. l Licensee's r'rocosed Alternative Examination 1

, The licensee proposed the following (as stated):

1 (1) The subject welds will receive a volumetric exam (utilizing best available technology) on the accessible portions in accordance with Section XI (IWB 25001).

(2) Inservice system leakage tests will be performed per Code Case N-4981 as granted by the NRC (Correspondence dated January 18,1995 TAC NOS. M90685,

, M90841, M91103, M90580).

3.0 EVALUATION The licensee performed a best effort examination of the above welds in the Millstone Unit 3 i reactor vessel from the inside surface. The volumetric coverage of the lower head circumferential and meridional welds averaged between 71 percent to 89 percent. The reduced volumetric coverage below that of the Code required 90 percent coverage for each of the welds, was attributed to physical obstructions from the instrument tubes that penetrate the lower head, the radial support lugs adjacent to the lower circumferential seam, and the rough clad surface on one of the welds. Furthermore, an examination from the outside surface of the vessel to supplement the volumetric coverage of the lower head meridional veelds and the torus to dollar plate weld, is limited due to obstructions from instrument tubes and, hence, it is impractical to meet the Code requirement of greater than 90 percent volumetric coverage for these welds.

However, a small percentage of volumetric coverage could be gained for the lower head circumferential weld at a cost of high man rem. The staff has determined that if the Code l requirements were imposed on the licensee, the reactor vessel would have to be redesigned, modified, and replaced, which would impose a significant burden on the licensee.

The subject welds are located beyond the vessel beltline region and, therefore, would not be exposed to critical neutron fluence level to adversely affect their fracture toughness. The staff further determined that unacceptable flaws caused due to any degradation mechanism, if present, would have been detected with reasonable confidence with volumetric examination coverage of 71 percent to 89 percent for the subject welds, and there were no such flaws found as a result of the enamination, Therefore, the licensee's proposed attemative testing provides reasonable assurance of structuralintegrity.

4.0 CONCLUSION

The staff has reviewed the licensec's submittal and concludes that the Code examination requirements are impractical to comply in case of the lower head meridional welds and the torus-to-dollar plate weld due to obstructions from the incore instrument tubes. If the requirements were imposed, the reactor vessel would have to be modified, which would impose a significant .

burden on the licensee. The proposed alternative testing, however, provides reasonable

o j ..

5-assurance of structuralintegrity in that service induced degradation, if present, would have been detected. Therefore, the licensee's request for relief, as stated in Relief Request No. IR 26, is granted pursuant to 10 CFR 50.55a(g)(6)(i) for Millstone Unit 3, during the 1st 10 year inspection interval, in that the applicable ASME Cede requirements are impractical and that the proposed attematives are imposed. The relief granted 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 burcen upon the licensee that could result if the requirements were imposed on the facility.

Principal Contributor: P. Patnaik Date: February 17, 1998 m wwmnewarnY