ML20088A706
| ML20088A706 | |
| Person / Time | |
|---|---|
| Site: | Comanche Peak  |
| Issue date: | 04/10/1984 |
| From: | Finneran J TEXAS UTILITIES ELECTRIC CO. (TU ELECTRIC) |
| To: | |
| Shared Package | |
| ML20088A703 | List: |
| References | |
| NUDOCS 8404120426 | |
| Download: ML20088A706 (13) | |
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UNITED STATES OF AMERICA NUCLEAR REGULATORY COMMISSION BCFORE THE ATOMIC SAFETY AND LICENSING BOARD In the Matter of
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Docke t Nos. 50-445 and TEXAS UTILITIES ELECTRIC
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(Application for (Comanche Peak Steam Electric
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Operating Licenses)
Station, Units 1 and 2)
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AFFIDAVIT OF JOHN C.
FINNERAN, JR.
REGARDING A500 TUBE STEEL I,
John C.
- Finneran, Jr.,
being first duly sworn, do depose and state as follows:- I have previously testified in this proceeding as Pipe Support Engineer for Comanche Peak.
As such, I am familiar with Applicants' pipe support design program and the use of A500 tubular steel in the design of linear pipe supports at Comanche Peak.
A statement of my educational and professional qualifications was admitted into evidence in this proceeding as Applicants' Exhibit 142B.
This affidavit presents information addressing questions raised by the Licensing Board in its Partial Initial Decision regarding material properties for A500 tube steel.
I specifically address the Board's interpretation of testimony in this proceeding regarding Applicants' consideration of cyclic loads in pipe support designs and the significance of revised yield values for A500 steel on those designs.
8404120426 840411 PDR ADOCK 05000445 O
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5 Consideration of Cyclic Stresses As the Board recognizes in its Decision, Applicants have presented testimony in this proceeding regarding consideration under the ASME Code of cyclic stresses in the design of pipe supports (Decision at 6-7).
That testimony was presented in the context of interpreting a specific portion of the ASME Code and does not address the issue the Board raises in its Decision.
That testimony simply noted that the ASME Code had stress limits for cyclic stresses which are premised on a twice yield limit to assure that " shakedown" to elastic action will occur under cyclic loadings (Tr. 5893-94).
No testimony was given regarding Applicants' method of considering cyclic stresses in pipe supports at Comanche Peak.
In this regard, the Board should note that Applicants' pipe support design guidelines have not taken advantage of the Code provision which permits allowable stresses for cyclic loads to be set at approximately twice yield (ASME Code section 3231.l(a)).
Instead, those guidelines establish allowable stresses for these loading combinations at values less than yield.
Thus, the small revision to the yield values for A500 tube steel do not give rise to a concern with respect to the consideration of cyclic loads.
Consideration of Revised Yield Values a t Comanche Peak Even prior to NRC approval of Code Case N-71-10, Applicants recognized that the yield strengths of A500 tubular steel had been slightly decreased by that Code Case from the previously
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s 3-published values.
Applicants also recognized, however, that several factors in their pipe support designs assured that no adverse safety impact would result from their use of the original yield strengths for A500 tube steel.
Accordingly. Applicants concluded that it was unnecessary to revise the pipe support designs at Comanche Peak to account for the revised A500 yield values.
In the first instance, at the time Code Case N-71-10 was issued, Applicants recognized that the ASME reviews all Code Cases before issuance to assure that no potential safety concerns are raised by prior practices which may be altered by the new Code Cases.
In situations where such concerns may exist, the ASME will either make the Code Case mandatory or notify all parties who may be affected of the potential safety concern.
In this instance, the ASME did not make the subject Code Case mandatory and did not issue a notice of a potential safetp concern.
This assessment was recently confirmed by the ASME in the attached interpretive letter.
In view of this, Applicants were confident that the use of the original yield values for A500 tubular shaped steel presented no safety concern.
Applicants did not, however, base this conclusion solely on the ASME review process and determination inherent in the unconditional release of the Code Case.
Applicants also recognized that several conservatismE which are not otherwise considered in the design process provide additional margins of safety that more than offset the small reduction in
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A500 tube steel yield values occasioned by Code Case N-71-10.
First, Applicants knew that design criteria other than the tube steel allowable stress values are the limiting design considerations for pipe supports at Comanche Peak.
Thus, by assuring that those criteria are met in the first instance, Applicants were assured that the stresses in the tube steel would be limited to levels well below the allowable stresses.
For example, adherence to the 1/16" deflection criteria alone will in most instances limit the stresses imposed on the tube steel to levels well below the allowable stress values.
In addition, the stress limits on Hilti (and other anchor) bolts also serve as controlling design considerations, satisfaction of which provides added assurance that stresses in tube steel members are well below allowable stress levels for those members.
Given such conservatisms in their design process, Applicants were satisfied at the time the A500 tube steel yield strengths were revised that there is a high level of assurance that stress levels in tube steel members would not exceed even the revised A500 tube steel allowables.
Upon receiving the Board's Decision, Applicants undertook an evaluation of a large number of supports which use A500 tube steel to demonstrate the accuracy of their initial judgment on this matter.
As discussed below, that evaluation demonstrated that A500 tube steel members in Applicants' pipe i
supports are generally stressed only small fractions of the revised allowable stress limits.
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, In addition to the above, Applicants derived further i
assurance that stresses in tube steel members will not approach even the revised allowables for A500 tube steel from the fact that Applicants' pipe support design organizations use very conservative design philosophies.
For example, Applicants support designers frequently apply more conservative allowable load levels than are required.
In this regard, Applicants apply level B stress allowables in assessing the more severe level C loads.
Further, each pipe support design organization, as a general practice, employs' stronger tube steel sections than necessary in order to provide a contingency for possible changes in support loads and stresses as a result of support modifications or piping reanalysis.
This fact is evidenced by Applicants' evaluation of tube steel stresses, as discussed in the sample below.
Thus, the stresses imposed on the tube steel members in Applicants' pipe support designs are often much less than stress limits imposed by ASME criteria and NRC regulations.
Further, Applicants' experience with test data (which we receive with each shipment of steel) was that the actual yield strengths are generally substantially greater than the published values.
This test data is provided to Applicants by fabricators of steel materials _who perform material tests for various properties, including yield strengths, on each production run of material.
Applicants were confident, therefore, that the reductions in A500 tube steel yield strengths presented no l
concern for the ultimate safety of pipe support designs at I
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- . 1 Comanche-Peak.
To demonstrate for the Board the accuracy of our judgment on this matter, Applicants have examined the actual yield strengths for A500 tube steel in a sample of pipe supports and' conservatively assessed the worst case supports.
As discussed below, this evaluation clearly confirms that j
Applicants' original judgment on this matter was correct.
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Evaluation of Impact of Revised A500 Tube Steel Yield values To assess the impact of the revised A500 tube steel yield values on actual pipe support designs at Comanche Peak, and to confirm Applicants,' previous judgment that no safety concern exists with respect to those revised values, Applicants sampled a large number of supports for evaluation using the revised yiold values.
This analysis demonstrates that all stresses in tube I
steel support members remain below even the reduced allowable I
j stresses and that, in fact, the stresses in the vast majority of i
supports remained significantly below those allowables.
To generate the sample of supports for this analysis, Applicants first developed alphabetical listings of all Unit 1 a
and common area ASME supports for each support design l
l organization (NPSI, ITT-Grinnell and PSE).
Applicants then i
selected every hundredth support (PSE selected every 90th) from 4
the list.
If the selected support did not utilize A500 tube steel, the next support on-the list which did was chosen.
The
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resulting selection of 182 supports contained an excellent mix of i
buildings, systems, classes and types of supports.
Each selected
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support was then reviewed to determine the effect of substituting the reduced allowable stresses for the A500 tube steel based on the yield strengths published in Code Case N-71-10.
Applicants then tabulated the percentage of the revised allowable stress seen by the most stressed tube steel member of each support.
The results of this tabulation are, as follows:
Percentage of Reduced Allowable Stress for Highest Number Supports Strossed Tube Steel Member 82 0-10 52 10.01-20 22 20.01-30 9
30.01-40 8
40.01-50 3
50.01-60 4
60.01-70 1
70.01-80 0
80.01-90 1
91 182 (Total) l Analysis of the above sample demonstrates that for over 95% of i
the sampled supports the tube steel members seeing the maximum stress is stressed less than 50% of the reduced A500 allowable.
In fact, the average percentage of the allowable stress neen by all such members is 16.4%.
i In addition to the above analysis, Applicants have evaluated the impact of using actual, rather than published, yield strengths in pipe support designs.
As already mentioned, the actual strength of fabricated steel materials is generally much greater than the published material properties (e.g. yield strengths used for design calcula tions).
To demonstrate the implications of this fact for the pipe support designs at 4
9 i Comanche Peak which use A500 tube steel, Applicants selected the ten highest stressed support members from the sample of supports discussed above for further analyses.
Applicants determined from the certified mill test reports for these support members that the minimum actual yield strength for the A500 tube steel material in these members was 56.3 ksi.
To account for the 15%
reduction in yield strength assumed by the ASME to result from welding, we reduced the lowest of these actual yield strengths by 15% to 47.8 ksi.
This value is 33% above the 36 kai yield strength tabulated by the ASME for A500 tube steel in code case N-71-10, and still greater than the 42 kai yield strength value originally published.
Thus, even the worst case comparison of actual v. published yield strengths for A500 tube steel used in supports at Comanche Peak demonstrates that there is a significant favorable margin between these values.
This fact emphasizes the highly conserva tive nature of Applicants', support designs and confirms Applicants' initial judgment at the time the A500 tube steel yield values were reduced that consideration of actual material properties would more than offset the slight reduction of the yield values published by the ASME.
Finally, I note that the revised yield strengths for A500 tube steel are themselves conservative values selected by the ASME.
The ASME recognized that the yield strength of A500 steel in the cold wrought condition may be slightly reduced in the heat
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2 affected zone of welcheenta.
Accordingly, although precise matarial data was not available, the ASME selected as conservative values for this criterion the yield strengths for A501 and A36 mararinla.
See ASME interpretative letter, Nov a bar la,1383, (Attachannt).
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pohn C. vinauran, Jr, jf County of Scr.:arvell }
State of Texas
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Subscribed and rmorn to before tut this m'A day of @S b l
, 1994 k
u.erk_.
s ode Kotar] BunLtc This is a telecopy facsimile.
The original will be sent under separate cover.
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,Tho Amcriccn S
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'S Iclety cf Mrchenical Enginccra t)nceo Ugrrt ent g Cer"-- - " ~ ~ '
- "" '9017
- 212 644 7722
- TWX-710 581J267 Novemberla,k983 Texas Utilities Services Inc.
PO Box 1002 Glen Rose, TX 76043 Attn:
M. R. McBay
Subject:
Section III, Division 1 Code Case N-71-9 & N-71-10 ASTM A-500 Tubular Shapes
Reference:
Your letter of October 25, 1983 ASME File i NI 83-101 Gentlemen:
replies are as follows: Cur understanding of the questions in your inquiry and our Question 1:
An Owner has contracted for construction of component supports under the provisions of Case N-71-9.
Must component supports constructed from ASTM A-5 r
re-analy::ed using the lower yield strength values published in a later revision of the case (e.g., N-71-10 ) for the same material?
Reply 1:
No, are ner ther mandatory or retroactive.the provisions of later revisions to Code Question 2:
tucular shapes published in Case 1644-3 through N 71 9Why w duced in N-71-10?
re-Reply 2:
of A-500 in the cold wrought condition may be slightly re-T duced in the heat affected zone of weldments.
values, given in N-71-10, for A-500 were those used for The revised A-501 and A-36 material which were selected as conservativ values for A-500 tubular shapes in the welded condition e
Tho revised values may be chan dnta for the welded condition,ged at such time when material procented to the Committee for consideration.as required by the Code, is The higher aveelao6e which the inqu6ter boilewes m6ght affect the interpretationASME pro r
interpretattonmayappealtothecognizant ASMEcommitteeorsuccomm. Further, persons aggrieved by thisadditional code documents. ASME does not" approve,*" certify,"" rete "or" endorse"anyitem constructio i
cevice or activity.
ittee. As statedin the foreword of the
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9 NI 83-101 Texas Utilities Services Inc.
PO Box 1002 Glen Rose, TX 76043 Attn:
M. R. McBay Page 2 of 2 yield strength values published in N-71-9 are adequate because of the many safety factors and design constraints applied to the yield strength in the design of piping supports.
Question 3:
If a component support is ordered under a Design Specification which required compliance with an Edition and Addenda of the Code which was issued prior to final approval of Case N-71-10, and the contract date for the support is after the date of Council approval of Case N-71-10, does the Code allow the construction of the support under the pro-visions of Case N-71-9?
Reply 3:
Yes,. in accordance with NA/NCA-ll4 0.
We note that when, in the opinion of the Committee, a review of current Code provisions indicate a potsntial safety con-cern there are established means of notifying organizations and individuals who may be affected.
These means include notification through Mechanical Engineering magazine and letters to holders of Certificates of Authorization and jurisdictional and regulatory authorities.
These measures were determined not to be necessary in the case of the yield i
strength values for A-500 tubular shapes in Case 1644-3 through N-71-9.
Yours truly,
!'KevinEnnis
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f BPVC Assistant Secretary (212) 705-7643 KE/dp
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UNITED STATES OF AMERICA NUCLEAR REGULATORY COMMISSION l
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BEFORE THE ATOMIC SAFETY AND LICENSING BOARD
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In the Matter of
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TEXAS UTILITIES ELECTRIC
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Docket Nos. 50-445 and COMPANY, _e t _a l.
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' 50-446 (Comanche Peak Steam Electric
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(Application for Station, Units 1 and 2)
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Operating Licenses)-
I CERTIFICATE OF SERVICE I hereby certify that copies of the foregoing " Applicants'
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Response To Partial Initial Decision Regarding A500 Steel" in the above-captioned matter was served upon the following persons by overnight delivery (*), or deposit in the United States mail, l
first class, postage prepaid, this lith day of April, 1984, or by
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hand delivery (**) on the2th day of April, 1984.
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- Peter B.
Bloch, Esq.
Chairman, Atomic Safety and 1
Chairman, Atomic Safety and Licensing Appeal Panel l
Licensing Board U.S.
Nuclear Regulatory j
U.S.
Nuclear Regula tory Commission Commission Washington, D.C.
' 20555, i
Washington, D.C.
20555 Mr. William L. Clements j
- Dr.
Walter H. Jordan Docketing & Service Branch l
881 West Outer Drive U.S. Nuclear Regula tory i
Oak Ridge, Tennessee 37830 Commission Washington, D.C.
20555 i
- Dr. Kenneth A. McCollom Dean, Division of Engineering Architecture and Technology
- Stuart A.
Treby, Esq.
j Oklahoma S tate University Office of the Executive Stillwater, Oklahoma 74074 Legal Director U.S. Nuclear Regulatory
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Mr. John Collins Commission i
Regional Administrator, Washington, D.C.
20555 Region IV U.S.
Nuclear Regulatory Chairman, Atomic Safety and l
Commission Licensing Board Panel 611 Ryan Plaza Drive U.S. Nuclear Regula tory j
Suite 1000 Commission Arlington, Texas 76011 Washington, D.C.
20555 4
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Renea Hicks, Esq.
- Mrs. Juanita Ellis Assistant Attorney General President, CASE Environmental Protection 1426 South Polk Street Division Dallas, Texas 75224 P.O.
Box 12548 Capitol Station Austin, Texas 78711 Lanny A.
Sinkin 114 W.
'th Stree t Suite 220 Austin, Texas 78701 4-William A.
Horin 1
cc:
Homer C.
Schmidt Robert Wooldridge, Esq.
David R.
Pigott, Esq.
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