ML19339C921

Testimony Re Methodology Used in Performing Analysis of Ultimate Capability of Facility Containment Vessel to Withstand Pressures Similar to TMI-type Accident.Prof Qualifications Encl

ML19339C921
Person / Time
Site:	McGuire, Mcguire
Issue date:	02/09/1981
From:	Priory R DUKE POWER CO.
To:
Shared Package
ML19339C912	List: ML19339C911 ML19339C914 ML19339C915 ML19339C916 ML19339C919 ML19339C920 ML19339C921 ML19339C922 ML19339C923 ML19339C925 ML19339C926
References
NUDOCS 8102120342
Download: ML19339C921 (7)

Text

9 UNITED STATES OF AMERICA NUCLEAR REGULATORY COMMISSION BEFORE THE ATOMIC SAFETY AND LICENSING BOARD In the Matter of )

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DUKE POWER COMPANY ) Docket Nos. 50-369

) 50-370 (William B. McGuire Nuclear )

Station, Units 1 and 2) )

TESTIMONY OF R.B. PRIORY REGARDING CONTAINMEh"I' STRUCTURAL INTEGRITY AND RESPONSE TO LICENSING BOARD QUESTIONS

1. Q. Have you prepared an analysis of the ultimate capability of the McGuire containment vessel?

A. Yes, I have.

2. Q. Why did you prepare this analysis?

A. As a result of the TMI accident Duke undertook an analysis to determine whether McGuire could withstand the pressures associated with a similar type accident.

3. Q. What methodology did you use in performing this analysis?

A. I conducted a structural evaluation of the pressure boundary of the containment vessel to determine the location of minimum strength when loaded with an axisymmetric and quasistatic uniform internal pressure.

The results of this evaluation demonstrated that the region of minimum strength occurred in the cylindri-cal portion of the shell and was associated with gen-eral yielding of the 3/4 inch shell plate / ring stif f-ener configuration.

The containment was analyzed to determine its ulti-mate capacity using a finite element model of the full containment shell. The model was constructed of axisymmetric curved shell elements and analyzed using the MARC computer program. Both geometric and material non-linearities were accounted for in the analysis procedures. The actual ~ containment

. functional capability was established using the collapse load criteria of the American Society of Mechanical Engineers Boiler and Pressure Vessel

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' Code,Section III, Division I, Appendix II. A

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detailed description of the containment and the above described analysis is set forth in " Duke Power Company, An Analysis of Hydrogen Control Measures at McGuire Nuclear Station," Volume 2, Chapter 4 (November 17, 1980).

4. Q. What conclusion do you reach with respect to your analysis?

A. I concluded that the functional capability of the containment pressure boundary is conservatively estimated to equal 67.5 psig.

5 Q. Based upon your familiarity with structural loading, could the McGuire containment withstand an internal pressure of 67.5 psig?

A. Based upon the analysis procedures used and the criteria used to define the functional capability of the vessel, my judgment is that the containment vessel could withstand an internal pressure of 67.5 psig.

6. Q. By Memorandum and Order of January 27, 1981 the Atomic Safety and Licensing Board (" Licensing Board") requested that, among other things, Duke Power Company respond to four specific ques-tions regarding the calculations which are the subject of your testimony. Have you read the Licensing Board's questions and prepared a response thereto?

A. Yes. The response to each Licensing Board question

("LBQ") is set forth below:

LBO-1: Identify each factor that enters into the de-termination of the new value for pressure capability and explain any changes in numerical values or in-terpretations of codes that are used in this re-determination.

Re s ponse : The McGuire containment vessel design considers an extensive set of service loading conditions and combinations thereof, as delineated '

in the McGuire Nuclear Station Final Safety Analy-sis Report. The peak internal pressure which forms a part of several load combinations is equal to 15 psig and occurs as a result of the design basis accident.

This pressure is often referred to as the " design pressure" of the vessel although it represents only one (1) of the service loading conditions present in the load combinations under consideration.

The objective of the Duke study was to determine the functional capability of the containment vessel to withstand internal pressure. This determination is not intended to replace the original " design pressure" with a new value but to establish a realistic and conservative estimate of the full capability of the structure to withstand internal pressure and remain functional. The analysis technique employed is commonly referred to as plastic analysis and is defined by the American Society of Mechanical Engineers Boiler and Pressure Vessel Code as follows:

" Plastic analysis is that method which computes the structural behavior under given loads con-sidering the strain hardening characteristics of the materials, strain rate effects, permanent de fo rmations , and stress redistributions occur-ring in the structure."

The procedures outlined in Appendix F of the ASME Code,Section III were used for the analysis and determination of the collapse pressure with the exception that actual certified mill test reports of the material properties were utilized in lieu of minimum material properties required by specifica-tio ns .

LBO-2: Explain why the changes are considered to be acceptable or unacceptable.

Re sponse : The analysis performed to determine the functional capability of the containment vessel is consistent with sound professional engineering practice. Other investigators have determined similar values of capability for the McGuire containment vessel. Structural evaluation of similar containment-vessels, at other plants, have utilized comparable ~ analysis procedures and have arrived at comparable ratios of design pressure to functional capacity. On this basis, I conclude that functional pressure capacity of 67.5 psig is reasonable and acceptable.

LBC-3: Explain the degree of engineering reliability reflected in each of the new values.

Response: The functional capacity value was established utilizing conservative assumptions to provide reasonable assurance that the value is below the actual ultimate capacity of the structure. A summary of these assumptions is as follows:

1) Longitudinal stif feners were neglected in the computation of meridional bending stresses.

The consequence of this assumption is an overestimate , of the stres s component.

2) The assumed diameter of the cylindrical por-tion of the vessel was nominal plus the extreme erection tolerance. Similarly, this assumption leads to an overestimate of shell stresses.

3) The yield strength assumed in the analysis was the actual mean minus 2.05 standard deviations.

The mean value of yield strength would be more representative of the true stress state at the ultimate pressure because of the ability of the structure to redistribute stress to locations of higher strength, if yield strength has been exceeded in a local region.

4) The ASME,Section III, Appendix F procedure for establishing the collapse pressure provides margin to assure reliability of the value obtained. Actually, the plastic analysis results predict the structure to remain stable at pressures in excess of 80 psig.

5) Material strain values are less than 1.2% at 67.5 psig. The mean ultimate strain values for vessel materials are on the order of 27.0% -

30.0%.

6) The peak displacements of the shell, at 67.5 psig, are comparable ' to values for one of the loading conditions for which the containment vessel was originally designed.

7) Gravity loads associated- with the weight of the vessel and its attachments, parts and appurtenances were neglected in the analysis.

Stresses due to these loads are of opposite direction to those resulting from internal j pressure and therefore reduce the total stress, if included.

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LBO-4: Explain the degree of engineering reliability reflected in the final overall result of determin-ing a new value of pressure capability of the McGuire reactor building.

Response: The assumptions employed in the Duke analy-sis are sufficiently conservative to assure the result underestimates the functional capacity of the containment vessel. The behavior of the containment vessel in responding to internal pressure is well understood and verified by numerous studies. My professional engineering judgement is that the containment vessel can withstand internal pressures in excess of 67.5 psig. ,

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I Professional Qualifications of Richard B. Priory Principal Engineer, Civil and Environmental Division Cesign Engineering Department Duke Power Company 4

My name is R. B. Priory. My business address is 422 South Church i Street, Charlotte, North Carolina 28242. I an Principal Engineer of the Structural Engineering Section, Civil and Environmental Division, Cesign Engineering Department, Duke Power Company.

I h.old a Bacheolor of Science in Civil Engineering Cegree frcm West Virginia Institute of Technology and a Master of Science in Engineering from Princeton University.

From Cecember,1969 to August,1973, I was employed as a Project Engineer by Union Carbida Corporation, Chemicals and Plastics Division at their research center in South Charleston, West Virginia. From August,1973 l

to September,1974, I was employed by Princeton University as a Teaching Fellow while attending graduate school. From September,1973 to May,1976, I was employed as an Assistant Professor of Structural Engineering by the University of North Carolina at Charlotte. During this same period, I also provided consulting engineering services to engineering firms on several projects. From May,1976 to present, I have been employed as a Structural Engineer by Duke Power Company. In May,1978, I was promoted to my current l position, of Principal- Engineer of the Structural Engineering Section, Design Engineering Cepartment.

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I am a merter of the American Society of Civil Engineers, member of the Integrated Civil Engineering Systems Applications Group, member of the American Society of Metals, and a registered Professional Engineer in North and South Carolina.

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