ML20154Q898

Criteria for Determining Justification for Continued Operation When Encountering Major Discrepancies in 'As-Built' Safety-Related Equipment

ML20154Q898
Person / Time
Site:	Prairie Island
Issue date:	09/21/1988
From:	NORTHERN STATES POWER CO.
To:
Shared Package
ML20154Q884	List: ML20154Q879 ML20154Q898
References
NUDOCS 8810040097
Download: ML20154Q898 (6)

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• CRITERIA FOR DETERMINING JUSTIFICATION FOR CONTI'tVED OPERATION WHEN ENCOUNTERING MAJOR DISCREPANCIES IN "AS-BUILT" SAFETY RELATED PIPING SEPTEMBER 21, 1988 NORTHERN STATES POWER Co.

PRAIRIE ISLAND NUCLEAR GENERATING PLANT 1717 WAKONADE DRIVE EAS",'

WELCH, MN 55089 8910040097 880926 POR ADOCK 05000282 P F'DC

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TABLE OF CONTENTS PACE ,

1.0 INTRODUCTION

& SCOPE................................. 3 2.0 CRITERIA ............................................ 3

3.0 CONCLUSION

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4.0 REFERENCES

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1.0 INTRODUCTf0N & SCOPE

, These criteria are in' tended to assure the operability require-ments of safety related piping and associated supports if it

, is determined that stresses exceed allowables presented in i the Prairie Island USAR. These criteria permit operation for an interim period only. Modifications will be made which return the system to within USAR allowables by the next re-j fueling outage or sooner if operation permits.

These criteria are intended to expeditiously perform necessary evaluations to determine interim operability and not to delay appropriate actions.

For cases involving components classified as ASME Code Class I where USAR allowables are exceeded, NSP shall be notified upon discovery and NSP shall evaluate reportability require-

! ments per 10CFR50.

I l' 2.0 CRITERIA

2.1 Piping Operability Criteria

The piping analysis shall be in accordance with ASME,Section III NC-3600 service level D limits (Ref. 1).

i The design loading conditions to be applied in the

, analysis shall include the DBE earthquake.

j Following is the pipe stress criteria for justifying continued operation of the plant:

(Sgp + SWT

• 3DBE $ .O Sy} (Ref. 1 equation 9)

)

Where S gp = Longitudinal Pressure Stress

S = Dead Weight Stress WT i

j SDBE = Stresses Resulting From Design Basis

! Earthquake l S 7 = Material Yield Stress (Reference 1 Appendices)

{

Code Case N-411 allows for increased damping values, 3

independent of pipe diameter, for seismic analysis.

Therefore, increased damping values, in accordance i with reference 2, will be acceptable when performing i these analyses to meet operability. Should the piping stress analysis exceed the value of 2.0 Sy, or pipe supporltc do not meet their operable limits (see Sect.

l 2.2),lthenadditionaliterativeanalysisofthepiping 1 i

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. mcy bo required. Tho itorctivo cnolysis may use the knowledge that a support is not capable of withstand-ing the loads, and can be removed from the analysis.

Where feasible, the actual support stiffness may be included in the iterative analysis, along with other

, refinements.

For cases where piping secondary stresses are determined to exceed USAR allowables, a specific case by case approach will be used to determine interim operability.

2.2 Pipe Support & Hanger operability criteria As a first step in evaluating the support, a linear elastic analysis method will be used to determine the stress in the support members. In addition to the leading in Section 2.1, the support loade must include pipe thermal 17 ads and results from free end displace-ment and anchor mction. Supports will be analyzed .

using the allowables listed below to meet cperability requirements.

Structural Steel Tension Fg = 1.20 Sy but 5 0.70 Su Bending F = 1.20 Sy but b

5 0.70 Su Shear Fy = 0.72 Sy but 5 0.42 Su Compression F, < F t

u n t exceed 2/3 Per Combined Stress For axial compression and bending or axial tension and bending, use AISC 1.6., (Ref. 6)

Web Crippling = 1.0 Sy Weld Stress Fy = 0.42 Su (of weld material)

Anchor Bolts Use Factor of Safety of 2 against ultimate tension and shear values.

Snubbers Hydraulic: Load < manufacturers one time load capacity.

Movement < total travel Springs Load within catalog range without bottoming out Struts FS = 2 and < 2/3 Per Page 4

All remaining Use manufacturers publishcd fculted Catalog Items load rating. Where level D allow-ables are not given, and the factor of safety is specified in the catalog, use design allowables but with FS = 2. (Typical catalog FS = 5, therefore use 2.5 x catalog capacity).

Where F t

= Allowable Tensile Stress F = Allowable Bending Stress b

Fy = Allowable Shear Stress F, = Allowable Axial Compressive Stress Fy = Allowable Weld Stress Per = Maximum Strength of Axially Loaded Compression Member Sy = Specified Minimum Field Strength at Temperature (See Note 1)

Su = Specified Minimum Tensile Strength Temperature FS = Factor of Safety NOTE 1: Actual yield strsngth may he used where CMTR's are available for the material.

If a support fails using the linear elastic method, then a more refined analysis may be performed using plastic analysis techniques. The plastic analysis will follow the design rules of ASME Section III, Appendix F. {Ref. 1).

3.0 CONCLUSION

If the above criteria cannot be met, reportability per 10 CFR 50 must be evaluated and system operability requirements per Plant Technical Specifications must be evaluated and appro-priate actions taken.

4.0 .REFEJENCES

1. American Society of Mechanical Es.gineers, Boiler and Pressure Vessel Codes,Section III, 1983 Edition, through Winter 1985 Addenda.

2. American Society of Mechanical Engineers, Boiler and Pressure Vessel Codes, Case N-411, Dated 9/17/84.

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3. NRC-IE Bulletin 79-02, "Pipe Support Base Plate Designs Using Concrete Expansion Anchor Bolts," Revision No. 1 (Supplement No. 1), Datad 8/20/79.

4. USAS B31.1.0-1967, Power Piping Code.

5. Updated Safety Evaluation Report for PINGP.

6. "Manual of Steel Construction," American Institute of Stect Construction, Inc., Eighth Edition, 1980.

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