ML20213G137

Suppls Response to IE Bulletin 80-08 Re Exam of Containment Liner Penetration Welds & Discusses Listed Followup Actions to Resolve Open Status Identified in NUREG/CR-3053.Exam Unnecessary Due to Low Stresses in Weld

ML20213G137
Person / Time
Site:	Monticello
Issue date:	11/10/1986
From:	Larson C NORTHERN STATES POWER CO.
To:	James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
References
RTR-NUREG-CR-3053 IEB-80-08, IEB-80-8, NUDOCS 8611170339
Download: ML20213G137 (5)

Text

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. bMb Northern States Power Company 414 Nicollet Mall Minneapohs. Minnesota 55401 November 10, 1986 Telephone (612) 330 5500 Mr J G Keppler Regional Administrator, Region III U S Nuclear Regulatory Commission 799 Roosevelt Road Glen Ellyn, IL 60137 MONTICELLO NUCLEAR GENERATING PLANT Docket No. 50-263 License No. DPR-22 Additional Response to IE Bulletin 80-08, Examination of Containment Liner Penetration Welds IE Bulletin 80-08 requested information regarding NDE of the welds joining the process piping to the flued heads in containment penetrations.

NSP's response to this Bulletin was sent to the NRC on July 3, 1980.

Subsequently, NUREG/CR-3053 identified Monticello as having an open status for this Bulletin. This document also recommended followup actions that could be taken to resolve this concern. The recommendations were:

a) Those penetration butt welds which were not radiographed during acceptance examination should be reviewed by the licensee to determine if they are the design described in " Remaining Areas of Concern" and if a radiographic examination is physically possible.

b) For thase welds where a meaningful radiographic examination cannot be made, full justification for not making the examination should be presented by the licensee. Such justification could stem from a review of weld design, since these plants were designed and constructed to codes allowing welds without volumetric examination where, in the design, wall thicknesses were chosen using low weld efficiency factors.

c) The results of the examinations and the justifications should be identified by penetration number, size, piping system, and other-wise as required for full identification. The results should be reviewed and evaluated by cognizant licensee engineers, and then submitted to NRC/IE with this evaluation for final resolution.

The following actions were taken to resolve this issue:

1. The penetrations that contain welds that were not radiographed during construction and contain high energy steam or water piping (triple flued head design) were identified in NSP's original submittal. This design is the type described in " Remaining areas of Concern". A total of 16 penetrations meet this criteria and are tabulated on Attach-ment (1). The welds joining the expansion bellows assembly to the flued head forging, weld B in Attachment (2), were not radiographed due to the geometry of the finished penetration assembly.

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Mr J G Kappler, Reg III November 10, 1986 Page 2 Northem States Power Company

2. Since the geometry of these penetrations is such that a meaningful radiographic can not be performed, justification for not examining the welds was prepared based on the method proposed in (b) above.

Bechtel Power Corporation was contracted to evaluate the stresses in the subject welds and compare these to the Code allowable stresses taking into account the weld joint efficiency factors specified in the Code. The applicable Code for the Monticello containment vessel is ASME Section III, Class B, 1968 Edition. This Code references ASME Section VIII for design and fabrication. Weld joint efficiency factors are specified for buttweld joints where no volumetric examina-tion is performed. Calculations were performed on the largest penetra-tions (X-7A-D, X-9A/B, X-13A/B) and the smallest penetration (X-10) to determine the stresses. The calculations considered loading due to pressure, deadweight, thermal expansion, seismic inertia (OBE & SSE),

seismic anchor movements (OBE & SSE) and pipe rupture. The calculated stresses for the welds were very low, on the order of 1/10 of the Code allowable stresses. Attachment (3) is a detailed summary of the calculation results.

Based on the evaluations performed it can be seen that not performing radiographic examination of the subject welds can be justified due to the very low stresses in the welds. It is felt that the other penetrations whose size falls between those for which calculations were done can be justified based on the following:

1. The largest contributor to the calculated stresses was the longitudinal pressure stress. Since variation in this is dependent on the penetra-tion diameter (the other variables stay constant), the stresses calcu-lated for the other penetrations would fall between the largest and the*

smallest.

2. The large margin between the calculated stresses and the allowable stresses for the material.

Please contact us if you have any questions related to the information we have provided.

C E Larso Vice President Nuclear Generation CEL/ dab c: Resident Inspector, NRC NRR Project Manager, NRC Document Control Desk, NRC Director I&E, NRC G Charnoff

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ATTACHMENT 1 .

LIST OF HIGH ENERGY LINE PENETRATIONS j.

Penetration Penetration Penetration No. Service Size (In.) Wall Thk. (In X-7A,B,C,D Main Steam Lines 34" 9 . '5 X-8 Main Steam Drains  : 18" "

0.5 X-9A,B Feedwater 34" 0.5 X-10 Main Steam to RCIC 16" 0.5 X-11 Main Steam to HPCI 28" 0.5 l X-12 RHR- S/D Cooling Supply 34" 0.5 l

X-13A,B RHR- Return 34" 0.5 X-14 Reactor Water C/U 20" 0.5 X-16A,B Core Spray 24" 0.5 X-17 RHR- Head Spray 20" 'O.5

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ATTACHMENT 2 PENETRATION DETAIL ts

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ATTACHMENT 3 RESULTS OF EVALUATION A. Loading Combinations I P+D< .8 Sh ( Normal Loads )

II P+D+E< .96 Sh ( Upset Loads )

III TH < .8 Sa ( Upset Loads)

IV P + D + E'< 1.92 Sh ( Faulted Loads )

P = Pressure stress D = Stress due to deadweight TH = Thermal Expansion stress E = Stress due to seismic loads (OBE)

E' = Stress due to seismic loads (SSE)

Sh = Allowable stress at maximum design temperature Sa = Allowable stress range Sa = 1.25 Sc + .25 Sh Sc = Allowable stress at minimum design temperature Seismic anchor movements were negligible.

Pipe rupture loads not considered due to existance of guard pipe.

B. Results of Calculations Calculated Stress Calculated Stress Allowable Load Combination Pen. X-7A-D (psi) Pen. X-10 (psi) Stress (ps I 1266 604 14,000 II 1278 611 16,800 III 11 2 21,000 IV 1290 618 33,600 t

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