ML19326C394
| ML19326C394 | |
| Person / Time | |
|---|---|
| Site: | Arkansas Nuclear  |
| Issue date: | 12/23/1977 |
| From: | Desiree Davis Office of Nuclear Reactor Regulation |
| To: | Cavanaugh W ARKANSAS POWER & LIGHT CO. |
| References | |
| NUDOCS 8004220938 | |
| Download: ML19326C394 (9) | |
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h WASHING TON. D. C. 20555 %l(10 O j x.m / ~ p ..e Docket No. 50-313 Arkansas Power & Light Company ATTN: Mr. William Cavanaugh, III Executive Director, Generation and Construction P. O. Box 551 Little Rock, Arkansas 72203 Gentlemen: By letter dated August 24, 1977, you described a problem regarding low lift-off force for certain reactor containment building tendons at Arkansas Nuclear One, Unit No.1 (ANO-1). This letter also noted a decrease in tensile strength of some wires withdrawn for testing and stated that a review of both aforementioned problems was underway. By letter dated November 4,1977 you forwarded the results of this review in the form of a report. We have reviewed the November 4,1977 report and have determined that additional information is necessary in order that we may complete our review. Therefore, you should provide the information requested in the enclosure within S0 days of receipt of this letter. Sincerely, Don K. Davis, Acting Chief Operating Reactors Branch #2 Division of Operating Reactors
Enclosure:
Request for Additional -Information cc w/ enclosure: See page 2 s
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.6, Arkansas Power & Light Company CC Phillip K. Lyon, Esquire House, Holms -a Jewell 1550 Tower Suilding Little Rock, Arkansas 72201 ' Mr. Daniel H. 'Jilliams flanager,' Licensing Arkansas Power & Light Ccapany-Post Office' Box 551 Little Rock, Arkansas 72203 Mr. John W. Anderson, Jr.. Plant Superintendent Arkansas Nuclear One . Post Office Box 608 Russellville, Arkansas 72801 Arkansas' Polytechnic College Russellville, Arkansas - 72801 ,e \\. e r a e - l 1 l Le
n s Encicsu_e_ Arkansas Nuclear Ont. Unit 1 Docket 50-313 P.EQUEST FOR ADDITIONAL INFORf4ATION REACTOR CONTAINfiENT BUILDING TENDON SURVEILLANCE ~ I.. The information provided to-date indicates that the following variations in strength may cause. concern (see pages 2-1, 2-3, and 4-1 of November 4,1977 report): tendon. 31H40 fe lift-off forces lower than required e n 32H14 - some wiregsamples failed at less than tendon guaranteeiminimum ultimate strength. '; p- ~ This information involves only hoop tendons. The information given on page 4-2, however, 'is diff'arent. It indicates that the average lift-off force (per. wire) for all vertical tendons is approximately +0.41" higher than expected, but that the average value of. lift-off forces.for both hoop and dome tendons is lower than expected [for dome tendons - 0.68% (approximately); for hoop tendons - 1.1% (approximately)]. Another contradiction can be found in information provided in figures 4.1,'4.2, and 4.3. It can ha coen that, per wire, the lift-off force was lower than expected for: V95(VerticalD / 1D20; 3021; 2008 (Dome) 32H14; 32H24; 32H40; 32H32; 31H39; 31H41; 31H50; 3iH40 (hoops) .l. Explain these contradictions and correct them. 2. Explain the significance of lower lift-off forces for the stability of the structure. f Explain the significance of. ultimate strength ofwire samples lower than 3. p the guaranteed minimum ultimate strength for the stability of the structure. Items 2 and 3 involve-a study of errors inherent in such a complex operation as lift-off-force measurements and of tolerances which should be applied to 'the result evaluation.
=+ s . II. In your letter dated August -24,1977 you stated that 46 tendons have the same' heat of material as tendon 32H14. In the flovember 4,1977 report the problem of the heat is not mentioned. Explain this contradiction and possible omission of the heat problem. ,,,III. The documents furnished 53 th: 'i:xx: suggest that the acceptance values and the normalizing factnrs used in the one-year surveillance in 1975 be modified and that after such a revision the normalized tendon lift-off forces will exceed the required minimum values. This approach is question-able, since one of the goals of successive surveillance operations is to establish historic continuity in the evaluation of the safety of the struc-p A modification of the basic criteria will destroy this continuity, ture. It is imperative first to establish the significance of not satisfying the original criteria and normalizing procedures. To clarify this problem, answer the following questions: 1. It is indicated in your letter of August 24, 1977, that the lowest value recorded and accepted as valid for the ultimate strength of
- p the wire samples was 229 ksi,* the nighest was 246 ksi. The required ultimate strength of the wires required in AST!1 A 421-74 is 240 ksi.
The maximum devietion was therefore approximately -4.6%. It is also indicated that the stress at elongation of 15 was less than the required 192 ksi. In addition some samples with ultimate strength icwer than 240 ksi had an elongation smaller than that required by the specifi-cation of 4.05. The wire manufacturers' have a great amount of statis-tical information available. Therefore present a study of the signifi-dance of these deviations. (See pages 5-2 & 5-3, Tables 5.1, 5.2, 5.3 and Appendix G). 2. There is a confusion between " sample" length and " gage" length. For example.in the letter dated August 24, 1977 the expression "100 inch sample" is used; also on page 2-3 of the report the expressions "10 inch samples" and "100 inch samples" are used. In Tables 5.1, 5.2, 5.3 in Appendix H the expression " measure gage length" is used throughout. Clarify these contradictions. a 3. Explainpemeaningoftheexpression" guaranteed # minimum ultimate strength (pages 5'3, 5-4). What are the tolerances and permitted deviations on the " guaranteed" values? 4. Clarify the meaning of " improper" wire removal procedures. If the reason for the difficulties is in the use of a sheave approximately '12 inches in diameter explain why this procedure did not damage the wires in vertical and dome tendons. See page 3 in Appendix I. The mention of "Bauschinger Effect" may be inappropriate since this effect has~ been mostly investigated far uni-axial tensile tests or torsion, and the problems presented in this documer ation are much more ccmplex p (see page 5-4 of the report and page 3 ' Appendix I). Describe the future wire removal orocedure as planned at this time.
a s I 5. In several locations in the. report it is indicated that some button-heads are "offsire". The original design of buttonheads by the manufacturers is very sophisticated. Therefore explain what is meant by "offsize" and justify the statement that this did not influence the strength of the tendons. (see page 2-1. and Appendix D). Discuss other imperfectior.s of the buttonheads such as cracking, offset etc. 6. On page 2-2 it is stated that with two revisions of the basic criteria, all the tendons are considered acceptable. This statement seems to be. inappropriate since, as indicated above, the use of new criteria may be objectionable in itself. Therefore qualify this statement. 7.- On page 2-2 of the Report it is indicated that the "available" equipment could not perform adequately the wire continuity test. Explain why the needed equipment was not available for this important test. 8. "flo corrosion" is indicated on page 2-2. Explain the procedure establishing this negative condition, expecially whether the-procedure used permitted the discovery of any small pitting. See also Appendix G. 9. Discuss .. ail the testing of wires. You should cover all important facets on the testing procedure including, but not limited to: a. failing inside of gripping jaws. Influence of the shape of the jaws. b. the influence of curvature and twisting of tendons as installed ~ on the resistance of wire to removing, which may have pre-deformed the wires in a complex way. c. rate of speed of the testing machines.
- d. - ambient temperature during testing.
0 ,,,,,mpe e. possible eccentric 1(ading by the machines, bending or twisting of the wire samples. f. influence of the type of machine. g. comparison of testing methods used by the manufacturers, by Pittsburgh-Testing Laboratory, by Hales Testing Laboratory and by any other organization participating in testing of wire samples. Conformance witn ASTM specifications. h. ' influence of the temperature of fill'er and its pressure.
s . 'i. influence of.the average temperature of tendons in place.
- j. machine calibration
- 10. Add to information provided regarding filler (page 3-1 and Appendix C) a discussion clarifying the problem of shrinkage of the filler when cooling (outside of trumpets)., What procedures have been used to check on possible voids at intermediate points in tendons, due to the cooling shrinkage?
11. Indicate whether local bending of bearing plates has been checked. 12. Indicate how accurately the absence of pitting in anchor hardware has been observed, and the minimum size observable. 13. In Appendix B the normalizing formulae are presented. Discu'ss the possibility that factors neglected in these formulae may be more important than factors which have been included. (See Appendix B and page 4-1). Some of the neglected factors are: - First surveillance formula does not include con: rete creep and concrete shrinkage or thermal effects and c3ncrete placing variation. I - Integration along the tendon may introduce ques tionable ~ properties of materials. - Subsequent surveillance formula do not appear.n include the following: thermal effects, shrinkage, detailed effects on c'reep, bearing plate displacements, changes in concrete, i Young's elasticity. modulus and Poisson's ratic, Jack orientation, cracking of concrete. - Indicate the tolerances in normalizing factorr. i l
- 14. Table 4.1. and 4.2, pages 6-1 and 6-2 :nd Appendix f indicate that the elongations-have been measured between the outiide f ace of the bearing plate and the inside face of the ancher head.
Discuss whether the precision of these measurements is sui.'icient to establish the adequacy and the cor-rectness of lift-off forces.
- 15. Discuss. ram calibration.
In page 4-3 of the report it is indicated that load cell' calibration is " traceable" to the National Bureau of Standards. This expression is too vague. Indicate whether the N35 did ~in effect calibrate the load cells and if not, what is the significance of this procedure for the reliability of the calibration. It is.also indicated in the same page that the uncertainty of the Eneasurements is 0.5L (two times standard deviation). Define the standard deviation ifor such a small number of measurements and discuss the' basis for accepting an uncertainty of twice the
s 1 5-standard deviation in this case. Discuss also whether the' partici-pation of NBS, University of California, University of Arkansas, Wiss, Janney, Elstner and Assoc. Inc. and Zabel Calibration Service in different phases of the calibration operations leads to compatible results. (See Appendix F).
- 16. On page 5-1 of the report it is stated that 13 wires from 23 surveillance tendons showed ano.malies which were judged to be
' inconsequential. This is presented in some detail in 8 paragraphs on the same page. However, this infomation appears to indicate lax quality control during erection and not sufficient attentinn provided during previous surveillance operations. Discuss this problem.
- 17. On page 5-4.of the report a brief discussion is given of the metallurgical investigation, presented in a more detailed way in Appendix 1.
The appropriateness of including the _uSE of 12" sheave and the "Bauschinger" effect as explanations of the weakness of some wire samples has been questioned above, a. ' Discuss the manufacturing, testing, and quality controls of Suzuki, Limited, also the possible effect of transporting the wires through long distance shipping. ~ b. Explain whether the fact presented in page 2 (Appendix I) that one wire showed evidence of rust on the failed end, whereas the other failed wire did not, corresponds to a normal condition, to be expected, or may indicate some special circumstance causing different behavior of the two wires. ~
- 18. Appendix A describes the Surveillance Procedure.
State whether this procedure is in accordance with Regulatory Guide 1.35, with the ASME/ACI Pressure. Vessel Code, Section III, division 2, with the Technical Specifications and with Bechtel's Topical Report BC-TOP-S.
- 19. Appendix-E presents data sheets on retensioning, retensioning force and.. el onga tions.
Discuss the possible errors in this operation and the tolerances which should be used to evaluate the results. On page 4-3 it is stated that Ram el failed, was repaired and recalibrated. Discuss the' consistency of results obtained by using y.a Jr' calibrated Ram. Evaluate the possible errors. See question 15 e above on calibrat on. (See also Appendix F). L ,1 b s
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- 20. 'Apperdix H presents data sheets on tendon wire tests Discuss
.the possible errors and tolerances to be applied to results. See a also question above on wire testing.
- 21. The list of references' presented in the report (Appendix I,.
- page 4a) includes only references which date from 1958, 1963 and 1971..Present.some references which are more up to date, especially on "Bauschinger Effect." 22. Indicate (Appendix I) whether the chemical analysis 6grees with Suzuki results.
- 23. Conclusions are presented on page 2-4 of the flovember 4, 1977
_ report., Modify these conclusions in accordance with the answers to these. questions. I e ( f 1 3 > J4 M h e 4 L:' .5 'a ? e t .V-s 's y_) -. + -. ,-}}