ML20207L115

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

ML20207L115
Person / Time
Site:	Prairie Island
Issue date:	09/21/1988
From:	NORTHERN STATES POWER CO.
To:
Shared Package
ML20207K894	List: ML20207K891 ML20207L115
References
PROC-880921, NUDOCS 8810170194
Download: ML20207L115 (6)

Text

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, Enclosure l-  ;

L CRITERIA FOR DETERMINING JUSTIFICATION FOR CONTINUED OPERATION WHEN ENCOUNTERING r

i MAJOR DISCREPANCIES IN "AS-BUILT" SAFETY RELATED PIPING  !

l SEPTEMBER 21, 1988 1

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l NORTHERN STATES POWER CO.

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j PRAIRIE ISLAND NUCLEAR GENERATING PLANT 1

1717 WAKONADE DRIVE EAST 1

i WELCH, MN 55089 l

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!bk P

A $$ 282 PNU

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. TABLE OF CONTENTS PAGE

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 INTRODUCTION

& 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 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-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 10CER50.

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).

The design loading conditions to be applied in the analysis shall include the DBE earthquake.  !

i Following is the pipe stress criteria for justifying {

continued operation of the plant i i

(Sgp + SWT

• 3DBE 5 2.0 Sy] (Ref. 1 equation 9)  !

Where: S gp = Longitudinal Pressure Stress 1 S WT = Dead Weight Stress  ;

SDBE = Stresses Resulting From Design Basis Earthquake Sy

= Material Yield Stress (Reference 1 Appendices) I code Csse N-411 allows for increased damping values, independent of pipe diameter, for seismic analysis.

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

2.2), then additional iterative analysis of the piping i

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may be required. The iterative analysis 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 cupport 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 4

As a first step in evaluating the support, a linear elastic analysis method will be used to determine the ,

strdss in the support membera. In addition to the loading in Section 2.1, the support loads must include pipe thermal loads and results from free end displace-ment and anchor motion. Supports will be analyzed .

using the allowables listed below to meet operability I requirements. l I

Structural Seeel i'

Tension F t

= 1.20 Sy but 5 0.70 Su i Bending F = 1.20 Sy but b

5 0.70 Su  !

Shear Fy = 0.72 Sy but 1 0.42 Su  !

Compression F, < F t but not to exceed 2/3 Per  ;

Combined Stress For axial compress',on and bending ,

or axial tension and bending, use -l AISC 1.6., (Ref. 6)

Web Crippling = 1.0 Sy [

Weld Stress Fy =

0.42 Su (of weld material) I Anchor Bolts Use Factor of Safety of 2 against ultimate tension and shear values.  !

i Snubbers  !

Hydraulic Load < manufacturers one time load capacity.

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

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1 All remaining Une manufacturors published fcultsd 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 1 capacity).

Where F = Allowable Tensile Stress t

F b = Allowable Bending Stress j Fy = Allowable Shear Stress

{

, F, = Allowable Axial Compressive Stress  ;

F, = Allowable Weld Stress c

Per = Maximum Strength of Axially Loaded

. Compression Member ,

i Sy = Specified Minimum Field Strength at Temperature (See Note 1)

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

l If a support fails using the linear clastic 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

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, If the above criteria cannot be met, reportability per 10 CFR i

50 must be evalue.ted and system operability requirements per Plant Technical Specifications must be evaluated and appro- ,

priate actions taken.

I 4.0 . REFERENCES f

1. American Society of Mechanical Enginee.rs, 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, "Pipa Support Bose Plate Danigns Using Concrete Expansion Anchor Bolts," Revision No. 1

, (Supplement No. 1), Dated 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 Steel Construction, Inc., Eighth Edition, 1980.

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