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{{#Wiki_filter:l a na ENCLOSURE 7 / o UNITED STATES
- ,7, NUCLEAR REGULATORY COMMISSION h
WASHINGTON. D. C. 20555 SEP ?0 1!!SS f MEMORANDUM FOR: Richard H. Vollmer Director Division of Engineering FROM: Darrell G. Eisenhut, Director Division of Licensing
SUBJECT:
CVALUATION OF THE LANDSMAN CONCERNS FOR MIDLAND Your letter of September 8,1983 (Enclosure 1) provided a revised schedule for the DE work plan regarding the Landsman concerns. While I find the proposed schedule acceptable I feel com ensure that no fur *.her slippage ocnrs.pelled to emphasize that we must I am also in receipt of a letter from Billie Garde (Enclosure 2) that indicates their understanding that several staff members had " strong feelsings about the approval by the DG8 resolution." Please consider this letter in your ongoing review. 'Darrell "G. Eisenhut,' Director Division of Li. censing
Enclosures:
- 1. Vollmer memo to DGEisenhut 8/8/83
- 2. B. Garde to DGEisenhut 7/19/83 i
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- t MEMORANDUM FOR: Darrell G. Eisenhut, Director Division of Licensing, ONRR FROM:
Richard H. Vollmer, Director Division of Engineering, ONRR
SUBJECT:
EVALUATION OF LANDSMAN'S CONCERNS REGARDING DIESEL GENERATOR BUILDING AT MIDLAND I
References:
1. Memo, Eisenhut to Keppler, June 27, 1983 i 2. Memo, Vollmer to Eisenhut, July 21, 1983 i 3. Memo, Landssan to Warnick, July 19, 1983 l l Due to schedule conflicts between the Diablo Canyon Review and this effort on Midland which affects the parsonnel from Brookhaven National Laboratory (BNL), t DE must reschedule the completion of the Midland DGB review from September 28 to October 15, 1983. During the month of September, the BNL personnel will partially be carmitted to Diablo Canyon reviewing ITR's, preparing testimony and taking depositions. If you do not concur with slipping this effort to accommodate the demands of Diablo Canyon, please advise accordingly. j Enclosed is a revised Work Plan for the completion of the DE evaluation of the Landsman's concerns. The ASLB (via OELD) should be advised of the revised schedule for completion. i s f Richard H. Vollmer, Director Division of Engineering, ONRR
Enclosure:
_As stated i cc: H. Denton J. Knight G. Lear P. Kuo N. Romney C. Tan E. Adensam D. Hood CONTACT: N. Romney, SGE8 49-28987 s 1 N j \\ ,~' k ~g @ .m a .i yl
ENCLOSURE Midland NPP Diesel Generator Building Review Work Plan 1 August 24 - 25, 1983 Task Force - Site Visit - Completed September 8,1983 Task Force meet with: F. Rinaldt i J. Kane J. Matra 2 G. Harstead Septe.ber 13,1983(AM) Task Force meet with R. Landsman { (Ann Arbor, Michigan) September 12 - 13, 1983 Task Force conduct audit of Midland DGB (Ann Arbor, Michigan) October 15, 1983 Issue Report of Findings l I l t E i q e p
s f 1 GOVERNMENT ACCOUNTABRRY PROJECT Institute for Policy Studies 1901 Que Street. N.W.. Woshing:on. D.C. 20009 (202)234-9382 August 19, 1983 4 Mr. Darrell G. Eisenhut Director. z Division of Licensing Office of Nuclear Reactor Regulations U.S. Nuclear Regulatory Commission Washington, D.C. 20555
Dear Mr. Eisenhut:
On August 10, 1983 you responded to my Aug. 8, 1983 request for information regarding the review group formed to consider the concerns of Mr. Ross Landsman. On Aug. 11, 1983 during a public meeting on the Construction Completion Plan (CCP) you indicated that a review of the NRR Engineering Division had inlicated no support or agreement with Mr. Landsman. Mrs. Barbara Stamiris, the Citizen Intervenor on the soils settlement ("OM") proceedings inquired specif:.cally 3 i about Mr. Joe - Kane of your office and a consultant, Dr. Sing, of the U.S. Army Corps of Engineers. Yo" indicated that you were not aware of whether or not those indiv3 ~.uals had been asked or not. Please inform Mrs. Stamiris and myr.a ',f of the answer to that question. More specifically, it is our clea: understanding that several 4 members of the Engineering Staff in both the Region and in headquarters i had very etrong feelings about the approval of the DGB resolution. We expect your technical review to includa the past concerns of 4 both Regional and headquarters engineers. Furthermore, since the concerns about this issue and its resolution are of interest to Congress, the local intervenors and GAP we respectfully request that your of fice issue an Interim report, allow time for review j and comment by the public, and hold at least one open meeting prio-l to the issurance of the final report on this subject. 1 A final concern we wish to raise with your office deals with l the background of the individuals you have nominated to complete '1-the review of Dr. Landsman's concerns. All of the people selected are structural engineers.- Dr. Landsman of course, is a geo-technical 1 engineer. Clearly, any review team should contain professional representation from Dr. Landsman's discipline, and suggest that you appoint an independent geo-technical consultant to review the work of your engineers. t-Finally, we concur with Mr. Robert Warnicks suggestion contained i in his July 21, 1983 memo to you that "all related correspondence and } the resulting report (s) and documentation should be placed in the public document rcom and distribution list. " 4 \\ vv , gO p / + ,,,_)- +- V
t c e. Thank you for your extraordinary promptness to my August 8, 1983 letter, it was a pleasant surprise. I look forward to an equally pleasant substantive report on the DGB from your office. 1 Sincerely, Billie Pirner Garde citizens Clinic Director wgw F i 4 i I e i 1 ? I l I -- ~ ~- -,. ~ Y .i e-) e 4Y
7p' "k g'c d J-UNITED STATES ._. d,i._ _ I 8 ' *,. c ,7, NUCLEAR REGULATORY COMMISSION m i j wassinoron. o. c. 2osss 'I % l,,,, October 11, 1983 ]-j U Docket Nos: 50-329 OM, OL IIHF _l'i a _#m a and 50-330 OM, OL MEMORANDUM FOR: The Atomic Sufety and Licensing Board for the Midland Plant, Units 1 & 2 FROM: Thomas M. Novak, Assistant Director for Licensing Division of Licensing
SUBJECT:
SUPPLEMENTARY NOTIFICATION REGARDING DR. LANDSMAN'S CONCERNS FOR THE MIDLAND DIESEL GENERATOR BUILDING (BN 83-153) Board Notifications 83-109 and 83-14'2 have transmitted the NRC staff's plan to address the concerns of Dr. Ross Landsman of Region III regarding the structural adequacy of the Midland Diesel Generator Building (DGB). These Notifications are deemed to provide information material and relevant to safety issues in the Midland OM/0L proceeding, including testimony by members of the NRC staff and staff censultants during the December 10, 1982, hearing session. This Board hotification 83-153 further supplements the information regarding Dr. Landsman's concern, and is provided for your information. Enclosure 1 provides a reply by Mr. J. P. Knight to inquiries (Enclosure 1 to Knight's memorandum) by Mr. R. Vollmer as to (1) whether or not any members of ~ Mr. Knight's staff, or censultants thereto, share Dr. Landsman's concerns that the DGB is inadecuate to return to service from a safety point of view, and (2) whetter or not any of these individuals snare Dr. Landsman's specific tech-nical concerns, notwithstanding their judgement that the building is safe for operation. e b 'W / g Thomas M. Novak, Assi ant Director for Licensing Division of Licensing j
Enclosures:
As stated @(L l' f c } gl - l. g o..,. c# } 00T 171983
f ' DISTRIBUTION LIST FOR BOARD NOTIFICATION 4-Midland Units 1&2, Docket Nos.- 50-329/330 ACRS Members Charles Bechhoefer, Esq. Dr. Robert C. Axtmann Ms. Lynne Bernabei Mr. Myer Bender l Lee L. Bishop, Esq. Dr. Max W. Carbon James E. Brunner. Esq. Mr. Jesse C. Ebersole Dr. John H. Buck Mr. Harold Etherington Myron M. Cherry, P.C. Dr. William Kerr Dr. Frederick P. Cowan Dr. Harold W. Lewis T. J. Creswell Dr. J. Carson Mark Steve J. Galder, P.E. Mr. William M. Mathis Dr. Jerry Harbour Dr. Dade W. Moeller Mr. Wayne Hearn Dr. Milton S. Plesset Mr. James R. Kates Mr. Jeremiah J. Ray Frank J. Kelley, Esq. Dr. David Okrent Christine N. Kohl, Esq. Dr. Paul C. Shewmon Mr. Howard A. Levin Dr. Chester P. Siess Mr. Wendell H. Marshall Mr. David A. Ward Michael I. Miller, Esq. Thomas S. Moore, Esq. Mr. Paul Rau Ms. Mary Sinclair Ms. Barbara Stamiris Frederick C. Williams, Esq. Atomic Safety and Licensing Board Panel Atomic Safety and Licensing i Appeal Panel Docketing and Service Section l Document Management Branch I } Iv x ,?<
MIDLAND (For BNs) Mr. J. W. Cook Vice President Consumers Power Company 1945 West Parnall Road Jackson, Michigan 49201 cc: Stewart H. Freeman James G. Keppler, Regional Administrator Assistant Attorney General U.S. Nuclear Regulatory Commission, State of Michigan Enviornmental Region III i Protection Division 799 Roosevelt Road 720 Law Building Glen Ellyn, Illinois 60137 Lansing, Michigan 48913 Mr. Ron Callen Mr. Paul Rau Michigan Public Service Commission Midland Daily News 6545 Mercantile Way 124 Mcdonald Street P.O. Box 30221 i Midland, Michigan 48640 Lansing, Michigan 48909 I Mr. R. B. Borsum Geotechnical Engineers, Inc. j Nuclear Power Generation Division ATTN: D.'. Steven J. Poulos 1 Babcock & Wilcox 1017 Main Street j 7910 Woodmont Avenue, Suite 220 Winchester, Massachusetts 01890 Bethesda, Maryland 20814 Billie Pirner Garde Mr. Don van Farrowc, Chief Director, Citizens Clinic Divtsion of Radiological Health for Accountable Government Department of Public Health Government Accountability Project P.O. Box 33035 Institute for Policy Studies Lansing, Michigan 48909 1901 Que Street, N.W. Washington, D. C. 20009 U.S. Naclear Regulatory Commission Resident Inspectors Office Commander, Naval Surface Weapons Center Route 7 ATTN: P. C. Huang 1 Midland, Michigan 48640 White Oak Silver Spring, Maryland 20910 j Mr. Paul A. Perry, Secretary i Cons mers Power Company Mr'. L, J. Ause, Manager 212 W. Michigan Avenue Facility Design Engineering Jackscn, Michigan 49201 Energy Technology Engineering Center 2 P.O. Box 1449 -i Mr. Walt Apley Canega Park, California 91304 c/o Mr. Max Clausen Battelle Pacific North West Labs (PNWL) Mr. Neil Gehring Battelle Blvd. U.S. Corps of Engineers SIGMA IV Building NCEED - T Richland, Washington 99352 7th Floor 477 Michigan Avenue Mr. I. Charak, Manager Detroit, Michigan 48226 BC Assistance Project Argonne National Laboratory 9700 South Cass Avenue l Argonne, Illinois 60439 1 o 1 i .. ~ --. m "wwr' f
~ ' /' %o UNITED STATES '!} 'l NUCLEAR REGULATORY COMMISSION j WASHINGTON, D. C. 20555 , %' w / $EP 2 31983 MEMORANDUM FOR: Richarc H. Vollmer Director Division of Engineering i FROM: James P.. Knight, Assistant Director for Components & Structures Engineering Division of Engineering 4
SUBJECT:
MIDLAND ^ i c This is in response to your note of August 15, 1983 asking if any members of my staff, or our consultants, share R. Landsman's concerns i that the Midland diesel' generator building is inadequate for its intended service and whether they share any of his specific technical Concerns. I A task group, including consultants frcm Brookhaven National Laboratory (BUL), was fonned under the supervision of Dr. P. T. Kuo of the NRC i staff to conduct a reevaluation of the staff's position with regard to-acceptance of the Midland diesel generator building. Upon receiving Dr. Landsman's statement of concerns, dated July 19, 1983, members of the iti'dland revieQ" staff, 'and consultants ~ named below, were given copies of Dr. Landsman's memo. Their initial reactions were that Dr. Landsman's statement contained no new information and that their previous sentiments, as discussed further below, remained unchanged. On Septee.ber 8,1983, the task group consisting of Dr. Kuo, Dr. C. P. Tan' and Mr. N. Romney of the NRC staff, with the assistance of Drs. C. A. Miller, C. J. Constantino and A.. J. Philippacop ulos of B"L, conducted o L i . individual interviews with Mr. J. Kane, NRC staff. Dr. L. Heller, NRC l staff, and Mr. H. Singn, Corps of Engineers, and a group interview with Mr. F. Rinaldi of the NRC staff, Mr. J. Matra3f the Haval Ordinance Laboratory end Dr. G. Harstead of Harstead Associ.:tes. These individuals represent to the best of our knowledge all members of the NRC staff and our consultants who were principally involved in the review activities associated with the Midland diesel generator building. a
- l As you know, the task group solicited all information and opinions
'l related to the diesel generator building in addition to connents on Dr. -l Landsman's statement. The results of all interviews conducted in this effort are being compiled as a part of the overall task group report which is scheduled to be completed in October,1983. It is my understanding that the sentiments expressed by these individuals were essentially the same sentiments contained in the staff and consultant testimony before the Atomic Safety & Licensing Board; Mr. Rinaldi, Mr. Matra, Dr. Harstead, Mr. Kane and Mr. Singh were among the staff and consultant witnesses on -i this matter. Although.Dr. Heller. Mr. Kane and Mr. Sinah were not j - satisfied with certain asperas_of the analyses performus by the [ @WW"L p 8 ,e -my
i l Richard H. Vollmer SEP 23 v33 applicant, and some of these same aspects were echged by Dr. Landsman in his July 19, 1983 statement, none of these individuals have made a final assessment as to the acceptability of the diesel generator building for its intended service because they feel that the basis for such a judgement is incomplete. Consistent with the hearing record, Dr._Harstead, Mr. Matra and Mr. Rinaldi reiterated their judgement that the diesel generator building._ was structurally _accep.ta51ffbr~serviceWe., would remain sitructurally functional under design loading conditions. The task group met with representatives of the applicant at the offices of Bechtel Corporation in Ann Arbor, Michigan and went to the site on August 24 & 25, 1983. The task group returned to the Bechtel offices in Ann Arbor on September 12 8 13, 1983 for a further audit of the calculations employed to investigate the predicted performance of the diesel generator building. Both of these meetings were preannounced public meetingst however, there was no attendance by members of the i public. Dr. Landsman was also interviewed by the task group on September 13, 1983. , --Q M L ........-.c James P.%ight, Assistant Director for Components & Structures Engineering Division of Engineering
Enclosure:
R. Vollmer's Note to J. Knight dated August 15, 1983 cc w/ enc 1: ~ H. Denton D. Eisenhut T. N3vr.k C. Adensam G. Lear D. Htod L. Heller P. T. Kuo F. Rinaldi { J. Kane 1, t 'i 4 -- } .w.= ~ - - Y [
p.... i.ncl ;ur e i j UNITE D STATES E ".,, (;' g, { k,T.j,'.. i NUCLEAR REGULATORY COMMISSION .c WASHING TON. D. C. 20555 kb d' August 15, 1983 1 NOTE T0: Jim Knight With respect to the Landsman issue, I would like to know if any of your c staff or consultaats share Landsman's concerns that the Midland Diesel Generator Building is inadequate to return to service from a safety point of view, i.e., inability to meet, design requirements. I would also like an answer to the broader ques:, ion: do they share any of his specific technical concerns even though their bottom line judgment would be that the building is safe for operation. I would like to discuss.this with you on August 22nd. gk$b-R..Vollmer' i 1 i I' 4 ~! J J .Q Q. 0 ~< a
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- 4 ^ L/Q () y " f%y November 22, 1983 L. DIS W BUTION: Docket Nos: 50-329 OH, OL and 50-330 OM, OL Docket Nos. 50-329/330 L8'f4 r/f nsas MEMORANDUM FOR: Darrell G. Eisenhut, Director L Division of Licensing TNovak MDuncan FROM: Darl S. Hood, Project Manager Licensing Branch No. 4 Division of Licensing
SUBJECT:
RECOMMENDATION FOR SUPPLEMENTAL BOARD NOTIFICATION REGARDING MIDLAND DIESEL GENERATOR BUILDING Board Notification 83-165 dated October 26, 1983, transmitted the report of a special task group on the re-evaluation of the structural design and construc-tion adequacy of the Midland Diesel Generator Building (DGB). The re-evaluation had been prompted by the concern of Dr. Landsman in BN 83-109. Also, BN 83-153 dated October 11, 1983, had transmitted a reply to an inquiry by NRR's Director j of the Division of Engineering as to whether or not any member of that Division i or NRC consultant shared Dr. Landsman's specific technical concerns. g Review of the task group's report by others, and the NRC's internal process of soliciting coments on the Applicant's Proposed Fiv. dings of Fact and Conclusions of Law on Remedial Soils Issues, have resulted 'n recent coments on the DGB which are material and relevart to issues before the Board. The coments fur-ther indicate the vfews of NkR members and consultants regarding Dr. Landsman's concerns as expressed in BN 83-153. Because of the contents of the task I group's report, but also, in part, because of these supplemental coments, the NRC staff stPted during the Midland OM-OL hearing session of November 19, 1983, it would advise the Board by December 1,1983, of its position on the need to reopen the record on the special task grcup's re-review of the DGB. The stsff also noted dur'ng the Novenber session that if it takes the position that the record.need not be re-apened, it will file responsive findings with respect to the DGB or. December 9, 1983 As part of this decision process, Messrs, J. Kane and F. Rinaldi were requested to provide coments on the task group's repcrt and to provide their recomendation as to whether of not the hearing should be l reopened. Both replied November 18, 1983. I recomend that the Board be notified of these supplemental coments relative to the DGB. These are { discussed below. / l ,c, nj N l f dy 'N0ygg ggg n
~ 1. Coments of Joseph Kane op Applicant's Findings The task group's report, in part, discussed the results of an interview with Mr. J. Kane: "With regard to the structural analyses using actual settle-ment data, Mr. Kane observed 70-80% of the cracks to be in areas where the analyses indicated areas of high stress. Mr. Kane has documentea his concerns in memos dated August 2) 1983, and are included in Attachments 1 and 2." [page AII-3. In Attachment 1 of the task group's report, page 2. Mr. Kane noted he per-sonally had serious problems and questions with a report documenting an analysis perfomed by an NRC consultant, the U.S. Naval Surface Weapons Center (NSWC), and explained why he had not pursued his concerns at that time. He acknowledged that the staff position does not rely on the results or conclusions of the NSWC study. In Attachment 2 of the task group's report, second paragraph, Mr. Kane questions why total settlements were used in the NSWC study to compute maximum stresses and movements in checking for areas of cracking. Mr. Kane noted the need to clarify this with NSWC and re-examine computed stresses and movements with available crack mapping. He also noted that in several of the walls there does appear to be correlation of cracks with high stress areas and that this shoulo be discussed with NSWC. Supple'nental infomation regarding the above concerns in BN 83-165 is con-tained in a memcrandum from G. Lear dated October 14, 1983, which transmits to OELD the Geotechnical Engineering review coments en the applicant's proposed findings of fact and conclusions of law regarding. technical l 4 aspects of the CM-OL proceeding. The coments were prepared by J. Kane. On page 12 (Enclosure 1) Mr. Kane notes the results of his examination of i the results of the NSWC report and attaches a table showing the resultc of i his comparison from which he concludes that in the majority of locations, { cracks do appear in the identified areas of high :; tress. Mr. Kar.e notes the need to resolve this difference with NSWC, and that if his conclusions 1 are correct, "both the applicant's findirgs and the hearing record need to be corrected in order for the Board to make the proper findings." i I recomend that Enclosure 1 be forwarded to the Midland Board for supple-mental information to BN 83-165 and BN 83-153, even though the staff did not rely on the NSWC study nor the applicant's analyses, for its conclu-sion regarding the adequacy of the DGB. The infomation is potentially 4 i
relevant since the concern, if valid, would be contrary to other infoma-tion on tne record, which if relied upon by the Board, could lead to improper findings or cause the issue to be viewed in a different light. Specifically: I The NSWC report (Consumers Power Company Exhibit 30) concluded, in part, that: 4 "the analyses show that other areas [other than at the duct bank areas] of the DGE walls still have high stresses and in all pro-bability should also be cracked. But no cracks were observed in these areas." [Statments in brackets and underlining added.J and that: "2. The measured settlement values imposed on the analytical models resulted in very high stresses (over ten times yield) in areas l where no cracks now exist. Thus indicating that this settle-j ment value more than likely was not seen by this structure." Similar statements are made in the hearing by J. Matra of NSWC (Tr. pp. 11094 - 11127) and K. Wiedner (Tr. p.10815). II. Comments by U.S. Amy Corps of Engineers 1 Mr. G. Lear's memorandum of November 16,1983 (Enclosure 2) trar.smits to L8 f4 an October 28, 1983, coverletter from the Corps. of Eugineers (C0E) with two memoranda containing the coments of H. N. Sinoh. Mr. Singh's i comer.ts further explain why "the Corps is not in a position to certify the adequacy of the structure." Mr. Singh expresses numerous differences with the Applicants proposed findings of fact, and presents significant ] conclusions of his own. For.exawle, Mr. Singh finds "surcFarging has i created major structural distress in different ) arts of the building," i
- The Applicant's der.ir, ion to cast concrete 'to complete construction
.cf the 068] during the surcharge oots net comply with the sound construc-tion practices."... "There has been considerable warping of the structure during and subsequent to the removal of the surcharge"... "numrous cracks which have developed due to the settlement have been ignored for j j the purpose of stress evaluation."... "The soil spring constant used in i i the analysis is not appropriate"... "It is clear from the east well that all the cracks which are inclined and have developed after the release of l the duct banks are shear cracks"... "Obviously, all of the Applicant's analyses are erroneous. If the structure can not be correctly analyzed, 4 that is not a justification to declare it structurally adequate." is also relevant to the Board because as a composit document. it may cause the Board to view the Corps' position on the 068 in a dif-l ferent light. -. ~ ~ ~ - -, E
III. Coments of J. Kane on Task Group's Report and Recomendations to Reopen Hearing g In Enclosure 3. Mr. J. Kane notes numerous conflicts between hearing testimony and the Task Group's report. Paragraph 4C of Enclosure 3 states that an incorrect conclusion has not yet been brought to the Board's atten-tion. Mr. Kane presents several reasons why the hearing should be reopended on the DGB. Enclosure 3 speaks for itself as to why it is material and relevant to the issues before the Board. Accordingly, the Board should be notified of this document. IV. Evaluation of F. Rinaldi on need to Reopen Hearing In Enclosure 4 Mr. Rinaldi, using the same criteria as Mr. Kane in III above, reaches the contrasting view that the hearing record need not be reopended on the DGB. The issue of whether the Task Group's report pro-vides a sufficient basis to reopen the hearing is material and relevant to issues before the Board. Hence, Mr. Rinaldi's views should be for-warded to the Board. Dr S. Hood, Project Manager Licensing Branch No, 4 Division of Licensing
Enclosures:
As stated cc: See next page i 1 k' 4 DL:LB #4
- .DL l
DHood/h N T a i 11/ ;/83 11 3 l
's imlTfD STATES NUCLEAR REGULATORY COMMISSION was.onectos, o. closes .c j OCT 14 583 \\ MEMORANDtNFOR: William D. Paton. Attorney Office of the Executive Legal Director FROM: George Lear. Chief 0 1 Structural and Geotechnical Engineering Branch Division of Engineering SUBJEUT: GEOTECHNICAL ENGINEERING REVIEW COMMENTS ON THE APPLICANT'S PROPOSED FINDINGS OF FACT AND CONCLUSIONS OF LAW - MIDLAND PLANT We have enclosed the final phase of geotechnical engineering input on Midland's Finding of Fact in response to OELD request. 23 were previously provided to you in my memos of SeptemberComments 1 through 27, 1983 and September 30. 1983. Findings en the Borated Water Storage Tanks. Diesel Fuel Oil Tan 1 ground Piping. Liquefaction and Dewatering. Slope Stability of Baffle and Perimeter Dikes and the Diesel Generator Building. The enclosed coments were prepared by Joseph Kane (28153) who may be contacted if you wish to further discuss the coments.
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jy Geo e Lear, Chief I 7 Structural and Geotechnical 1 i Engfaeering Branch Division of Engineerirg cc: w/ attachment R. Volts.er J. Knf ht i T. Sul an 1 (.
- am S d. ear f
P. Kuo L. Heller D. Hood N. Wright M. Wileove R. Gonzales . F. Rinaldi J. Kimball H. Singh. C0E . (, ' ~ -J. Kane p V k J .e__.
/ l / r, actual Finding discuss' ions. Because of the above effects we feel major revisions to the Applicant's Findings are needed in order to adequately reflect the Staff's SER positions and conclusions in the NRC Findings. Diesel Generator Buildino
- 61. (Page134. Par.166). In this paragraph the Applicant's Findings cite the results of the Naval Surface Weapon Center (NSWC) study which ultimately concludes that when the measured settlement values are imposed on the analytical models of the DGB, very high stresses result l
in areas where no cracks now exist. In response to this study l conclusion, we have examined the results of the NSWC report. As, indica,ted, I in the attached tables where we have compared the areas of high stress computed by the t!SWC with areas of recorded cracking (visible signs of potentialstructuraldistress)ourconclusionsinthisreviewindicate that in the majority of locations cracks do appear in the fdentified areas of high stress. Because the NEWC conclusions are so significantly different from car conclusions we feel it is ne:essary to resolve this-difference with the NSWC. If our conclusions are correct we feel both the Applicant's Findings and the bearing record need to be corrected in order for the Board to make the proper Findings. 4 k
~.. - ~ i Comparl' son of Computed High Stress kreas with Recorded Cracked Areas . WEST CENTER ifALL Observations of J. Kane in Ccmparison of Cracked Areas with High Stress Area N MSWC
- Computed High Period of Fig. 14-2 Mapping Figs. 28-2 and Fig. 49 Mapp bg ConclusionsonComparisoD Figure Stress Areas-
- Measured December 1978 28-3 Mapping July 1981 Dec 1978;
' Settlement 5 Sept 1979 to /i ( Jan 1980 31 On south side $ 3/28/78 to
- No cracks shown' Crack observed in Same crack Cracks do appear in all
.,'9/79 is recorded observed in NSWC identified areas of below E1. 650 8/15/78 on.12/78 Map 4 in this area and 9/79 is again high stress when incre-i, (presurcharge) f is identified as recorded in 7/81. mental settlements for a a 4 crack due to given time frame are j. structural imposed and the latest ~s 6 , displacement crack mapping (July 1981) + e is used, 37 Onnorthsfde@,3/28/78to
- Crack shown in.,
No cracks shown Cracks shown in ~ below El 650 8/15/78 12/78 Map on 9/79 Map 7/81 Mapping 7 b hNW / (Presurcharge) available maps closest to dates of measured 33 Onnortl. side @ 8/78 to 1/79
- Cracks shown in' No cracks shown Cracks shown in to above El 634. c (presurcharge)12/78 Map on 9/79 Map 7/81 Mapptog and settlement, then cracks slight extension appear in 4 out of the of 12/78 mapped 6 locations (shown by i
cracks
- asterisks)ofhigh stresses. The fact that 35 Onnorthside@
8/78 to 1/79
- Crack shown in.
No cracks shown Cracks shown in 'd below El 650 (presurcharge)12/78 Map .on 9/79 Map 7/8.1 Mapping { ob 37 Onnorthside@ 1/79 to 8/79 Fig 14-2 Mapping not **No cracks shown Cracks shown in 9/79 but reappear in sL.A above El 634 (Surtharge applicable as it pre-on 9/79 Mapp //81 mapping and locations in 7/81 could j dates this period of slightly extend mean, the cracks were Period) settlement g3 mapped missed in 9/79. ' Crack shown in Same crack observed On south side h 1/79 to 8/79 Fig. 14-2 Mapping above El 634 (Surcharge not applicable. 9/79 map and is in 9/79 is again 1 39 identified as recoroed in 7/81. Period) structural dis-placement crack. f4 i 6 -,_-_ _ _
e_ l_1 L, Comparison of Computed liigh Stress Areas with Recorded Cracked Areas CENTER Wall. i ' Observations of J. Kane in Comparison of Cracked Areas l ;. with High Stress Area NSWC Computed High Period of Fig. 14-2 Mapping Figs. 28-2 and Fig. 49 Mapping ConclusionsonCg Figure Stress Areas Measured December 1978 28-3 Happing July 1981 \\ Settlement Dec. 1978; i . Sept 1979 to Jan 1980 1 31 Onnorthside@ 3/28/78 to Cracks shown in Cracks shown and Cracks shown in above E1. 634 8/15/78 12/78 Map increase from 7/81 Mag. ping (presurcharge) 12/70 to 9/79 Cracks do appear in 5 out of the 6 locations i 32 Onnorthside@ 3/28/78 to Cracks shown in Cracks shown and Crack shown in where NSWC has computed below E1. 650 8/15/78 12/78 Map increase from 7/81 Mapping areas of high stress (presurcharge) 12/78 to 9/79. and on crack maps with dates closest 33 On:northside@ 8/78 to 1/79 Cracks shown in Cracks shown Cracks shown to the treriods of above E1. 634 (presurcharge)12/78' Hap and increase in 7/81 Mapping ressured from 12/78 settlemants. to 9/79. 35 Onnorthside@ 8/78 to 1/79 Cracks shown in Cracks shown and Cracks shown in above E1. 634 (presurcharge)12/78 Map increase from 7/81 Mapping 12/78 to 9/79. 37 On north side h. 1/79 to 8/79 Fig. 14-2 Mapping Cracks shown and Cracks shown in above El. 634 (Surcharge not app 1Icable as increase from 7/81 Mapping Period) it predates this. 12/78 to 9/79 period of settlements 39 Onsouthside@ 1[19to8/79 Fig. 14-2 Mapping 'No cracks shown No cracks sht>wn . On 9/79 Map on 7/81 Hap above El. 634 (Surcharge not appilcable Peribd) S IS f
Nd-n u.-._:.a a _-. - - -- = Comparison of Computed High Stress Areas with Recorded Cracked Areas EAST CENTER WALL } Observations of J. Kane in Compariston of Cracked Areas v E with High Stress Areas NSWC Computed High Period of* Fig. 14-2 Mapping Figs. 28-2 and Fig. 49 Mapping Conclusions on Compai Figure Stress Areas Measured December 1978 28-3 Mapping July 1981 N Settlement Dec. 1978; Sept. 1979 to Jan 1980 31 On south side p-Location of high stress below El 663 is unreasonable for this (not reasonable stage of construction. j since wall is No. comparison therefore f built only to can be made. El 656 at this time). 32 Onnorthside@ 3/28/78 to
- Cracks shown No cracks Cracks shown Cracks do appear in all below E1. 650 8/15/78 in 12/78 shown in 9/79 in 7/81 Mapping MSWC identified areas of (presurcharge)
Map high stress when incremental settlements 33 .Onnorthside@ 8/78 to 1/79
- Cracks shown in No cracks shown Cracks shown in for a given time above E1. 634 (presurcharge)12/18 Map in 9/79 Map 7/81 Mapping frame are imposed and the latest crack mapping (July 1981) is used.
35 On south side h 8/78 to 1/79
- Cracks appear very Crack shown in Crack shown in
.above E1. 640 (presurcharge) close to this 12/78 Map 7/81 mapping
- If comparison is ilmited location in 12/78 to available maps Map.
closest to dates of measured settlements, then cracks appear in 3 out of the b locations (shown by asterisks) of 1 high stresses. 37 Onnorthside@ 1/79 to 8/79 Fig. 14-2 Mapping
- No cracks shown Cracks shown in above El 640 (surcharge not applicable as in 9/79 Map 7/81 mapping period) it predates this period of settlement 39 Onsouthside$
1/79 to 8/79 Fig. 14-2 Mapping
- Crack shown in Crack shown in above E1. 634 (Surcharge not appitcable.
12/78 Map but not 7/81 Mapping g, Period) in 9/79 Itap 3 s
'~ ~ ,d T'.h/h //6 M UNITED STATES [, 't NUCLEAR REGULATORY COMMISSION WASH 6NG70N,0. C. 20SSS a NOV 161983 MEMORANDUM FOR: Elinor Adensam, Chief Licensing Branch No. 4 Division of Licensing FROM: George Lear, Chief Structural and Geotechnical Engineering Branch Division of Engineering
SUBJECT:
CORPS OF ENGINEERS MEMORANDA ON DIISEL GENERATOR BUILDING - MIDLAND PLANT I We have recently received the attached letter from P. McCallister, Chief, Engineerir.g Division U.S. Army Corps of Engineers which is dated October 28, ,1983 and includes two enclosures that pertain to the Diesel Generator Building at the Midland plant. The enclosures were originated by the Corps reviewer for the Midland project, Mr. Mari N. Singh. The k)ctober 28, 1983 letter and two enclosures are being forwarded to DL i i for your information and appropriate licensing action. We plan to address the items identified in the two enclosures to the October 28, 1983 letter, where they are appropriate, in our future input to NRC Findings of Fact for the Diesel Generator Building. Iw 8 I George Lear,' Chief Structural and Geotechnical Engineering Branch j Division of Engineering l-Attachments: As stated cc: w/o attachments w/ attachments R. Vollmer G. Lear D. Eisenhut L. Heller J. Knight P. Kuo AMi j g F. Rinaldi 7 J. Kane g, N < A e\\ () s V' N' ( ,. '] qi <a I
r l f _r' DEPARTMENT OF THE ARMY S- "'50 y orvaorrcemet.comes ce twassas not Msf e Taon. cmaan assu i b I.'!. i Design Branch
SUBJECT:
Two Memoranda Concerning the Midland Nuclear Power Plant Mr. George Lear U.S. Nuclear Regulatory Com=ission Chief, Hydrologic and Geotechnical Engr Br Division of Engineering Mail Stop P-214 Washington, D. C. 20555
Dear Mr. Lear:
Attached are two memoranda providing Corps of Engineers co=ments regarding the recent controversy over the etructural adequacy of the Diesel Generator Building (D.C.B.). These memoranda are Midland Nuclear Power Plant, Midland, Michigan dated 28 September 1983 and Applicant's Proposed Finding of Fact and Conclusions of Law on Remedial Soils Issues-Midland Nuclear Power Plant, Midland, Michigan. Sincerely, / / i Enclosures P. McCallis , P. E. Chief Engineering Division 1 e d l l M p {h gh CF ~ 3 ,9 1
d' 8c'D D-C 28 September 1983
SUBJECT:
Midland Nuclear Power Plant, Midland, Michigan To: File FROM: H.N. Singh 1. The controversy over the structural adequacy of the Diescl Generator Building (DGB) of the Midland Nuclear Power Plant led the formation of an Indecendent Review Committee of four experts by the Nuclear Regulatory Commis sion. 2. Pursuant to an interagency agreement between the U.S. Army Corps of Engineers (the Corps) and the U.S. Nuclear Regulatory Commission (NRC), which became ef fective in September 1979, we have reviewed the geotechnical aspects of the Midland Nuclear Pouer Plant, and have concluded that the DGB has not been -
- correctly analysed (H.N. Singh's testimony of 10 December 1982 before the U.S.
Atomic Safety Licensing Board, ASLB). Therefore, the Corps is not in a position to certify the adequacy of the structure. 3. The NRC geotechnical experts have also concluded that the ef fects of the foundation settlement have not been considered in the analyses, therefore, the struct' ural analyses perfor=ed by the Consumers Power Company (CPCO) are not appropriate. Dr. R. B. Landsman of the NRC Region III of fice has testified to this aspect before the Congressman Udall's subcommitte, and before the ASLB. Mr. J. D. Kane, Principal geotechnical Engineer of the NRC also exprecaed his concern before the ASLB hearing on 10 Decamber 1982. 4. On 8 September 1983, I was celled upon by the newly formed Independent Review Committee to apprise the committee of the Corps' concerns regarding the l DCB. 5. I informed the Committee that the details of my concerns are provided in my testimony of 10 December 1982 before the ASLB, a'nd in the Corps' report of 7 July 1980, and 16 Anril 1981. An abstract of the Corns' concerns are a. The CPCO has not considered the ef fect of dif ferential settlement of the DGB in structural analyses. b. The DGB has numerous cracks on its walls. These cracks have reduced the rigidity of the structure, therefore, the ef fects of cracking must be considered in structural analysis. / c. CDC0 method of computing stresses in the reinf orcing bars on the basis of the crack vidth is not appropriate. I P 6. A list of concerns resulting from the review of the CPCO's " Proposed Findings of Fact and Conclusions of Law in 'the Midland Proceeding" is inclosed. ? Il H. . nah PESE Lead Reviewer Hidland Nuclear Power Plant 9 L. n el I
r s DED-C c
SUBJECT:
Applicant's Proposed Findings of Fact and Conclusions of Law on Remedial Soils Is, sues - Midland Nuclear Plant, Midland, Michigan i The Corps of Engineers has reviewed the subject report. The following are the comments: 1. Para. 91: The main reason for uneven settlement of the Diesel Generator Building (DGB) is variable soil stiffness resulting from poorly compacted soil. No doubt, the duct banks did contribute to unequal settlement in the beginning, but there has been significant uneven settlement subsequent to their release from the walls in December,1978. 2. Para. 92: The major cracks in the east wall of the DGB developed subsequent to the release of the duct banks from the building. The number of cracks prior to the release of the duct banks are shown in Attachment #2 of the original testimony of H. N. Singh. This attachment shows only 10 cracks on the east i wall, but today there are 16 cracks on the wall. i 3. Para. 92: The settlement cf the D.C.B. after the release of the duct banks is not, uniform as claimed by the Applicant in the last mentence of this 'l paragraph. As shown in Attachment No.-2 (Fig-2) of the testimony of Mr. W. N. Singh, there has been considerable dif ferential settlement af ter the { release of the duct ba nks. 4 Para. 93: The settlement of the D.C.B. during the surcharge has created many cracks, (Singh's original testimony Q-9). On the east wall, the number of 1 cracks increased from 10 to 16. Therefore, the surcharge did reduced the struc-tural integrity of the D.C.B. The Applicant has not considered the settlement in his structural analyses (Singh testified before ASLD on 10 Dec 1982 to this t i aspect), and has not been able to demonstrate the adequacy of the D.C.B. i i 5. Para. 95: Partially saturated soil will not' consolidate as saturated clay l as claimed by the Applicant in this paragraph. The Corps of Engineers ' concern j as to this matter was communicated to the Applicant through the Corps' report of' 7 July 1980 para. 63(a). 6. Para. 96,97, 98: We do not understand the intent of providing the contents of these three pargraphs. The matter described is well-known. Every soil engineer knows when primary consolidation is completed, and the secondary portion of consolidation continues as a straight line when plotted on logarithimic time scale. 7. Para. 99: Surcharging of a completed or partially completed structure is i not a well established and widely accepted technique as claimed by the Applicant i in this paragraph. A number of precedents described in Dr. Peck's testimony are } nothing but surcharging of foundations; the portions of structures which are ) 4 6 ~ ) ,._..g..
m. c5ED-C
SUBJECT:
Applicant's Proposed Findings of Fact and Conclusions of Law on Remedial Soils Issues - Midland Nuclear Plant, Midland, Michigan affected by the differential settlement were not completed. The case of the D.G.B. is entirely dif ferent, where almost entire structure was completed during the surcharge. Therefore, surcharging has created major structural distress in dif ferent parts of the building. 8. Para.102: The surcharge did not produce adequate stresses in the foun-dation soils to negate the effect of future loads (dewatering etc.) on the settlement. This has been substantiated by the excessive measured settlement af ter the plant area was dewatered to elevations less than 595. 9. Para. 103: It is not a sound engineering practice to cast concrete, when the structure is moving (settling). The Applicant's decision to cast concrete j during the surcharge does not comply with the sound construction practices. ,j
- 10. The piezometer readings and the shape of the consolidation curves did not confirm that all the excessive pore pressures were dissipated. The reasons are given in the Corps of Engineers report of 16 April 1981 (Question No1 40).
- 11. Para. 106: To limit the accuracy of survey instruments (transit) to 1/8" is too high to be realistic. The normal measuring devices in leveling instru-ment 1s can read up to 1/'000 of a foot, therefore, it appears that Applicant's settlement seasuring method was not appropriate. Further, the error in measure-ment can be either plus or minus resulting in uncertainty in the measured settlement. In such case, to inst.te safety of the structure, it is reasonable to use higher values of settlement. The Applicant's method of computing settle-ment and creatina error band of 1/4", and neglecting the differential settlement for computing stresses are not sporopriate.
12. Para. 107: It is not known how the observations of the borros anchors would improve the precision of the data obtained. The data from borros anchors l are more susceptible to errors than the reading on the markers which were located at the fixed points on tha valls of the D.G.B. I 9
- 13. Para. 112: Although, the pond level was raised to elevation 627.00, there
't is no evidence that water level below the D.C.B. rose above elevation 622.0 (Corps' report of 16 April 1981, see piezometer 12, 17, 23, 25, 29, 34, 36, 40, .] and 43). 14. Para. 114: - The primary consolidation under the D.G.B. was not completed ac all the points (Singh testified before ASI.B on 10 Dec 1982 on this aspect) as claimed by the Applicant. 'l
- 15. Para. 117: The foundation of the D.C.B. did not remain in plane after the removal of the surcharge. There has been considerable warping of the structure during and subsequent to the removal of the surcharme (see Singh's criminal y
testinony). lj 16. Para. 121: The reduction in stresses due to the surcharge removal did not exceed the stresses'due to the added loads. For example the dewatering has j ,added so much stress in excess of the surcharge stress that the foundation soils ? started showing primary consolidation. I i i s
l i,:D-C l - jcBJECT: Applicant's Proposed Findings of Fact and Conclusions of Law on i Remedial Soils Issues - Midland Nuclear Plant, Midland, Michigan i 17. Para. 125: The settlement due to the devatering is primary settlement. I don't know when and how Dr. Peck added this settlement to the secondary settle-ment. It should be the part of the primary settlement. Part of this might be compensated by the additional settlement for continuing the surcharge load which has been included in the total predicted settlement. But definitely it has not been included in the secondary settlement.
- 18. Para. 130: There is no' justification for correcting the measured settlement the way the Applicant has done. Applicant has consistently made unjustified corrections to reduce the differential settlement in the structure. If there are errors in survey, there is possibility that corrections might increase the s e t tleme nt.
But the Applicant's corrections have always reduced the settlement.
- 19. Para. 131:
Dr. Peck's conclusion that piezometer observations are prone to anomalies is correct. But in the case of Midland Plant, a substantial number of piezometers consistently showed that pore pressures under the D.C.B. have not .been completely dissicated. Hence taking advantage of anomalies to justify an incorrect result is not appropriate. 4 20. Para. 132: Dr. Peck's calculations of permeability are based on many questionable assumptions. Therefore, there is no merit in the values of the permehbility calculated. l 21. Para. 135: Dr. Peck's conclusion in para.135 is not appropriate. In care of future cracks, a redistribution of stresses will take place, and the soil which was bridged by the structure before cracking will be subjected to more i loading, causing additional settlement and more stresses in the structure. i 22. Para. 138: I do not know whether Licensing Board has agreed with Peck's and Hendron's conclusions.
- 23. Para. 147:
Dr. Peck's and Hendron's conclusion that th'e structural integrity of the structure has not been impaired-is not correct. Mr. Singh has l already shown in his original testimony that number of cracks on the east wall j has increased from 10 to 16 after the surcharge. The curvature of the structure { has. considerably increased af ter the surcharge. This is a clear indication that stresses in the structure had increased to such a level due to the surcharge [ that numerous new cracks developed. Further the analysis of the D.C.B. struc-ture due to eettlement is incorrect. Dif ferential settlement of the structure has not been considered in the evaluation of the stresses. Also numetaus cracks which have developed due to 'the settlemene have been ignored for the purpose of l stress evaluation. 24. Para. 150, 151: The soil spring constant used in the analysis is not appropriate. Bechtel did not consider the correct values of spring constant. 1 l I l ? t 3 .= I e 9 s-4 y v ,e --w -n, r---- e. e,,e-m v nn- -,,~-m-
3 . ;DED~C 'jsUBJECT: Applicant's Proposed Findings of Fact and Conclusions of Law on i Remedial Soils Issues - Midland Nuclear Plant, Midland, Michigan 25. Para. 154: It is clear' from the east wall that all the cracks which are I inclined and have developed af ter the release of the duct banks are shear i / cracks. These cracks have bent towards south, indicating shear stree due to l excessive settlement at the southeast corner. I 26. Para. 166. The error band created by the Applicant is not justified. The ASLB has been informed by Mr. Singh and Mr. Kane on 10 December 1982 regarding this fact. 27. Para. 168: Dr. Corley was wrong in making the statement that there is no evidence in the structure of any other hard spot. I do not know what is the basis of his conclusion. There are evidences of large cracks on the east vall which occurred after the release of the duct ba nks. This clearly establishes that theae large shear cracks have occurred following the settlement of the southeast corner. Further, settlement patterns developed af ter the relessa of 1 the duct banks clearly indicate that there are many sof t spots under the D.G.B. Further, the variation made in the spring constant over a 15' length was not adequate to reflect the sof tness of the 2arge area under the foundation. 28. Para. 169: No cracks have been considered in the analysis. 29. Pa'ra. 170: If the Applicart can not analyse the structure correctly, that does not mean that he will perform incorrect analysis to justify the adequacy of the structure. Obviously, all of the Applicant's analyses are erroneous. If the structure can not be correctly analyzed, that is not a justification to declare it structurally adequate. f iY' H. N. SINGH, P.E.S.E. NCDED-G Lead Reviewer Midland Nuclear Plant I t l ' i i i + i l .,f e i I E 1
- ~~..o.,
..____,_t_. m _,.r __-,-.,.._m_ , +,, _,., _.._,,,m-.~
b Li g UNITED STATES /. NUCLEAR REGULATORY COMMISSION //D a r~I wassi~cro=, o. c. nossa M HOV 181983 MEMORANDUM FOR: George Lear, Chief Structural and Geotechnical Engir.eering Branch Division of Engineering THRU: yman W. Heller, Leader J d( Geotechnical Engineering Section Structural and Geotechnical Engineering Branch 7 Division of Engineering FROM: Joseph Kane, Sr. Geotechnical Engineer Geotechnical Engineering Section Structural and Geotechnical Engineering Branch Division of Engineering
SUBJECT:
COMMENTS ON OCTOBER 21, 1983 REPORT BY INDEPENDENT TASK GROUP REVIEW OF THE DGB AT THE MIDLAND PLANT s In response to your verbal request, I have enclosed my review coments on the October 21, 1983 report by.he Independent Task Group which was fomed to evaluate the concerns expressed by R. B. Landsman of Region III for the f Diesel Generator Building. It is my understanding that my review coments will ultimately be considered j in OELD deliberations as to whether it is necessary for NRC to request reopening of the ASLB hearings on the DGB. The general guidelines provided by OELD relative to their decision which I have used in identifying the potential hearing considerations are the following: 1. Does the issue whic5 I have identified in the Independent Task Group . report provide new evidence that affects or modifies the hearing i j record evidence? I 2. Are the facts or expert opinions which are expressed in the Independent Task Group Reprt significant and different from the facts or expert opinions that are now in evidence before the Licensing Board which could ] affect a conclusion with rerpect to the structural adequacy of the DGB7 3. Although the infomation from the Independent Task Group report does not change the Staff conclusion with respect to the DGB - in " fairness to i the Board" should the Board have the benefit of reviewing the evidence in the report in order to reach its conclusion? ^ j u a N g j i
e / deorgeLear NOV 181983 / On the basis of my review of the Independent Task, Group report and ny comparison with the guideline provided by OELD. I h' ave provided my comments in Enclosure 1. Joseph Kane. Senior Geotechnical Engineer Geotechnical Engineering Section Structural and Geotechnical Engineering Branch Division of Er.gineering i
Enclosure:
As stated cc: w/ enclosure R. Vollmer J. Knight T. ' Nova k L. Heller P. Kuo T. Sullivan E. Adensam D. Hood W. Paton OELD M. Wilcove. OELD F. Rinaldi N. Singh. COE ~ J. Xane e J l i i i l f 1 . = - ~ - - v ,-,-,,n.,,.-_-...
i
Subject:
Review Coments on October 21,1983 Report by Independent Task Group on the DG8 Plant: Midland Plant Units 1 and 2, 50-329/330
- Prepared by: Joseph Kane, NRR, DE SGE8 l
1. A. Potential Hearing Consideration - There are statements in the Independent Task Group report on the completeness and accuracy of l available settlement data and history that are in conflict with the previous testimony of reviewers from the NRC geotechnical engineering staff and the Corps of Engineers. The specific areas of the report are: Group Report, Pg. 6. "a complete and accurate settlement history a. does not exist b. Group Report, Pg. 12. "there are no such detailed settlement f measurements available, especially for the early stagas of l construction." l l ' c. Group Report, Pg. 15. "Given the unavailability of the data necessary to complete the input to the analysis by the staff's j , consultant, the previously stated staff position is reasonable." d. Group Report, Pg. 20. "However, such settlement history for j the DG8 does not exist." e. Group Report, Pg. 21. " Inconsistencies in the documentation of i the settlement history needs tc be resolved." i f. Appendix III, Pg. 5. "However, it should be mentioned that the exact settlement history at the various settlement markers at subsequentlygiven) question." (Reasons for this statement are the DG8 is open to g. Appendix I!!, Pg. 7. "These analyses, though different in detail, f lead to the similar conclusion that the settlement measurements l were(andcontinuetobe)insignificanterror." h. Appendix III, Pg. 8. "The first period (where measured j settlementsarebeingusedtocomputestresses)spansfromthe i becinning of construction through Au;ust 1978 at which time construction was halted." 1. Appendix !!!, Pg. 17. "However, it is recomended that the ancialies in the documentation of the settlement history be resolved" (LastparagraphofApp.III,Section2.2). These nine statements are in conflict with $$ER No. 2, pg. 2-33 'and the testimony of J. Kane and H. Singh during the week of December 6 - 10, 1902. ? -.,. ~.....
. 8. Applicable OELD Guitfelines - Guidelines Nos.1, 2 and 3 C. Basis for Identifyinq !ssue As Potential Hearing Consideration - Because the nine identified statements in the Independent Task Group report r raise questions with respect to the completeness and accuracy of the DGB set'.lement history and because this is in conflict with previous Staff testimony, the hearing record has became unclear and confusing. Also item 1. in the above identified statements appropriately recomends that these anomalies be resolved. In sty opinion all three of the guidelines identified by OELD would apply when considering the need to reopen the hearings in order to straighten out the hearing record on this issue. 2. A. Potential Hearing Consideration. At this particular time there are questions and significant doubts as to the defensibility of NRC position in concluding there is reasonable assurance that the structural integrity of the DGB will be maintained and its functional requirement fulfilled (See October 21, 1983 memo from P. T. Kuo to J. P. Knight, pg.1; Group Report, pg. 21, Conclusion no. 5; App. III, pg.17.Conclusionno.6). The questions and doubts result from the following items in the Independent Task Group report: r a. The report in several locations identifies the need for the Applicant and the NRC staff to properly document the information and calculations for crack width approach for all DGB walls in order for the stresses that are induced by settlements to be known and evaluated. (See October 21. J983 memo, pg. 2, item 3; Group Report, pgs.16 and 21, item 2; App. III, pgs. 11, 16, 17 item 2). b. Closely related to this issue is the report's acknowledgement that the crack method approach is questionable where relatively few cracks occurred (App. III, pg.11) and the absence of written justification in the FSAR for using this approach for structures like the DG8 (App. III, pg.16). c. In addition the report in several locations points out the inadequacies of the present crack monitoring program and the need for improvement (Group Report, pgs.17 rnd 21 item 4; App. III, pgs.13,16 and 17) and the need to establish action levels (Oct. 21, 1983 memo, pg. 2 item 5; App III, pgs.16 and 17 item 4). d. The NRC Staff position on DGB acceptability uses the crack width approach to estimate settlement induced stresses and this position is heavily dependent on the accuracy of available crack maps. In several locations in the Task Group report, the reliability and accuracy of presently available crack maps are questioned and the Group report cites concern that cracking in the DGB has not i
j-stabilized and thIt cracks are growing (See Oct. 21,1983 mema, pg. 2 item 4; App. III pgs. 6. 7,13 and 17 item 3). In my opinion it will be necessary to obtain.and use more recent and i accurate crack maps of the DG8 before the recommendation of the j Task Group can be followed for establishing crack width levels i that will reflect a sufficient stress margin available to resist i critical load combinations (October 21, 1983 memo, pg. 2 item 5). l 8. Applicable OELD Guidelines. Guideline Nos. 1, 2 and 3. 4 i C. Basis for Identifying Issue As Potential Hearino Consideration. For the NRC staff to have a reasonable and defensib' e position in judging l the adequacy of the DGB there is a need to have a good data basis. i The Task Group report, as indicated by the above coments, correctly points out that at this time we do not have that basis. The report provides some specific recommendations that should be followed j i in order to reach the needed sound engineering basis. Both the Board ar.d the public have already asked what is the NRC Staff response to 1 1 the report's recommendations and will want to know what sigr.ificant ,information is developed in carrying out these recomendations. For these reasons I believe all three of the guidelines provided by OELD 1 apply and would be the basis for reopening the hearing on the DGB. l ^ ) 3. A. Potential Hearina Consideration. The Task Group report in many f locations discusses the controversial finite element analysis j completed by the Applicant where the measured / predicted displacements were " straight lined" which essentially disregards any effect of 4 differential settlement. (SeeGroupReport.pgs.7,20 item 1; i App. III, pgs. 9 and 14). In the Dec. 6 through 10, 1982 hearing sessions j this issue was extersively discussed and reflected significant differences in professional opinions that has left the hearing record l unclear and unresolved. The statements in the Task Group report on this controversial subject are very specific and clear "that i this model (the Applicant's) will yield cr. conservative estimtes of stresses." (App. III, pg. 9, 2nd par.) and "We therefore conclude l' that this approach to compute settlement stresses is inappropriate." 1 (App Ili, pg. 9) and "The straight line representation of the settlements along the north and south wall for the analysis reported in 2.4.1 is said to be in error. As indicated in that section of this report, it is our opinion that this analysis will result in unconservative i predictions of stresses due to settlements. As such, it is considered i to be an inappropriate analysis." (App. III, pg.14, 2nd par.). 4 i i 5 3 .W
~
- i.,
8. Applicable OELD Guide' lines. Guideline Nos. 1, 2 and 3. l C. Basis for Identifying Issue As Potential Hearing Consideration. In my opinion the presently conflicting evidence before the Board on this issue is significantly impacted by the Task Group's findings. I believe the clear engineering explanation provided in the report's statements on why this analytical approach is not appropriate would be helpful to the Board in assisting them to reach a decision on this issue. l 4. A. Potential He6 ring Consideration. A previously identified concern expressed by J. Kane (Oct. 24, 1983 memo, G. Lear to W. Paton on the Applicant's Proposed Findings, pg.12, item 61) with the results of the Naval Surface Weapon Center (NSWC) study is also impacted by ~ the Task Group's report. Although the Task Group in App. III, pg.10 questions the value of the NSWC conclusions because of the i apparent linear assumption of settlement data points made in the study, the report by the Group reflects an influence of the NSWC sresults by referencing the important conclusion by the NSWC study - that very high stresses are calculated in areas of the DGB where no cracks now exist. (See Group Report, pgs. 8 and 20 item 1; App. III pgs.14and15). This NSWC corclusion is seriously questioned when 4 a comparison is made of the computed areas of high stress with areas of recorded cracking (See enclosure tables to Oct. 24,1983 memo). When the internal walls of the DGB are evaluated for computed areas of j high stress with areas of recorded cracking, it can be shown that i cracks appear in 94 percent of the locations where the NSWC study has computed high stresses. j I l 1 B. Applicable OELD Guidelines - Guidelines No's. 1, 2 and 3. l j C; Pasis for Identifying Issu'e As Potential Hearin". Consideration. Both the Task Group report and the present hearing record offer the conclusion by the NSWC study that cracks do not appear in areas of i computed high stress, thereby indicating that the settlement values l i more than likely were not seen by the structure. This MSWC conclusion is incorrect and this issue has not yet been brought to the Board's attention. It is quite likely that the Board would place significant reliance on the NSWC conclusion, if left uncorrected, in reaching its decision with respect to the safety of the DGB. For i 'these reason'. I feel it should be brought to the Board's attention. t 1 1, s I a r k-
s 5. There a're less important ' considerations affected by the information within the Independent Task Group report, that would not require reopening of I the DGB hearing, but which would be helpful to the Board if addressed, since they are related to previous testimony. These items are: a. Group Keport, pgs. 3 and 4. The impitcation that surcharging the completed DGB structure relieved it of stress. b. App. III, pg. 5. The questionable significance of the piezometer data during surcharging, c. App. III, pg. 12. The statement that serious structural distress was caused by the very large settlements at the DGB. d. App. III pgs. 12 and 13. The need to improve the accuracy of future settleaent monitoring at the DGB and to require batter r.ethods for monitoring crack growth with reliable strain gages. t J l O I i t d b
._.m h f.{.&c-c/ UNITED STATES t, NUCLEAR REGULATORY COMMISSION // q. WASHINGTON. D. C. 20546 ' NOV 181983 1 ~ MEMORANDUM FOR: George Lear Chief Structural and Geotechnical Engineering Branch i Division of Engineering i THRU: Pao-Tsin Kuo, Leader 1 Structural Engineering Section B J Structural and Geotechnical Engineering Branch Livision of Engineerb.g i FROM: Frank Rinaldi, Structural Engineer Structural Engineering Section 8 Structural and Geotechnical Engineering Branch Division of Engineering
SUBJECT:
EVALUATION OF EVID:NCE ON DIESEL GENERATOR BUILDING - MIDLAND PRNECT FOR DETERMINATION OF NEED TO REOPEN HEARINGS Pursuant to your request of Wyember 8,1983, for my evaluation of any new evidence related to the structural adequacy of the Diesel Generator Building (DGB), I have evaluated the report by the NRR Task Group dated 0 tober 21, 1983, for the test conditions provided by your management (Enclosure 1) and expanded by the staff attorney (Enclosure 2). Foremost. I like to state that the NRC staff decision to reopen the hearings on the DGB lies on the NRC legal staff. The NRC legal staff is aware of the official staff position and personal technical positions of staff members and consultants, as stated in written and oral testimony during the ASLB hearing of December,1982. In addition, tie NRC legal staff is aware of the questions raised by the Region III-IE inspector as well as the answers provided by all concerned parties. Indeed the NRR Task Group Report of October 21,1982, documents the conclusions, di:cussions, and specific answers to the questions raised by Region III-IE inspector. The NRR Task Group report includes their findings, those of their consultant staff from Brookhaven Nation 61 Laboratory (BNL), as well as the replies by MRR Structural and Geotechnical staff and their consultants to the questions t raised by the Region III-IE inspector. Please note that errata has been 1 l pointed out to the Task Group. The need for corrections has been acknowledged by the Task Group and errata pages have been issued. Recognizing the fact that my recomendations on the subject of reopening the hearing for the DGB are needed for the final decision making, I will i identify the important facts stated by the Task Group and state if they constitute, from the structural engineering point of view, new evidence or if they impact on the previous conclusions reached by the structural engineering staff. The major points are the following: nk o>" .} ^3 l
~ 7.... j George Lear NOV 181983 i \\ I 1. The Task Group used the same facts and evidenc*e*used by the review i staff in their evaluation of the DG8. l 4 2. The Task Group reached the same bottom line conclusion. "that there is reasonable assurance that the structural integrity of the DG8 will be maintained and its functional requirements fulfilled." j 3. The Task Group concluded that, "The most reasonable estimate of stress due to settlement is based on the crack width data. However, the calculations that have been done in this area need to be completely l { documented." ) 8 4. The Task Group stated. "That a more accurate and reliable crack f monitoring program be established." and that sufficient stress margins i for Action Level and specific repairs be established for Alert Level of crack /s width /s. Also, they recomended a general repair program i prior to plant operation. The fir'st two items are self-explanatory and from a structural engineering I hearings are required to establish the structural adequacy of the DG8. The technical point of view should be the major reasons that no additional i third item hsks for the documentation of the calculations used in the j determination of the conservative stress values utilizing the crack width data. The approach has been discussed, the results have been documented, and the date used for the calculations has been identified. Therefore I the requested documentation will consist of nothing more than presenting the i information related to the assumpticos made, formula used, input data. calculations, and results. The actual calculations require basic skills and engineering judgment. The resulting stress values can be easily verified with the stress results identified in the written and oral testimony of the applicant and the staff. I do not consider this documentation to be new evidence because the facts do not change. The fourth item recomends a modification to the monitoring program previously proposed by the applicant and a:cepted by the staff and a general repair program. The Task Group does j j not provide specific approaches that would fulfill these recomendations. BNL report recomends the extensive use of Whitmore strain gages in place of the three crack monitoring windows currently accepted by the staff, but recommends the same general approaches as the Task Group for requirements on l the general repairs and the requirements on the Alert and Action Levels. The Task Group was aware of the 8NL recomendation related to the Whitmore strain i L gages, but did not make such firm recomendation. The above stated facts lead l l' me to the conclusion that the Task Group is leaving the structural review j ] staff and the applicant with the task of resolving these concerns. 1 =.
Y ~ george Lear NOV 181983 I conclude from my review of the Task Group report that the h% staff r.ceds to start discussions with the applicant concerning the documentation of the rebar stresses as determined from all available crack-width data, the usefulness and effectiveness of the strain gages prcposed by BNL, and if more specific actions should be established now, or as results of meetings with the applicant after the alert and/or action levels are reached. The applicant has contracted with Portland Cement Association (PCA) to review P and evaluate all field data (cracks and deflectionq) to evaluate potential and specific problems identified by t.'.e monitoring program. The staff was relying on this independent monitoring and evaluation by PCA in the acceptance of the monitoring requirements. I understand the fact that some people may not fully understand the i structural engineering technical aspects of this case and may consider the availability of any new document as solid ground for reopening the hearings on the DGB. However, based on the fact that no new evidence was uncovered 'in the preparation of the conclusions of the Task Group, that the structural adequacy of the DGB was assured, and that no specific detailed recommendations were made other than generic suggestions which the staff can request the applicant to resolve and then infom the board of the resolutions; I do not recommend, from the structural engineering technical point of view, to reopen the hearing on the structural safety of the DGB. ~ M g4 Fra k Rinaldi, Structural Engineer Structural Engineering Section B j -Structural and Geotechnical Engineering Branch Division of Engineering
Enclosures:
4 j As stated I cc: R. Vollmer J. Knight T. Novak j T. Sullivan E. Adensam D. Hood W. Paton P. Kus L. Heller J. Kane l G. Marstead i J. Matra F. Rinaldi l i i
17' N. e t to apply in deciding whether to recommend that the hearing be s c reopened. Is there new evidence that modifies the evidence of record? For example, does the new evidence affect what was said by the . witnesses (any or all) in such a way that something different would have been said if the information had been available before the testimony was given? The issue is one of " fairness to the board". If our feeling is that the evidence would not change our conclusions but that the 'board nevertheless, should have the benefit of reviewing this new evidence to reach its conclusions, then we should recommend i for reopening the record. ) 1 'h*. ENCL D50RE 1 3
Are the facts or expert opinions in the'DGB Task Report that are i different from facts cr expert opinions now in evidence before the Licensing Board. (The facts and expert opinions referred to are i significant facts and expert opinions,1. e. - facts and expert opinions that could effect a conclusi_on w'ith respect to the structural adequacy of the Diesel Generator Building) 9 i t l I - l I l l ) 1 J l l 1 1 I s c 1 ,_____i____________
4_ (m -m , _ a_, = L J f PRINCJPAL ST/ 7F H WA January 4,1985 ?W.MPP oc %y ^ x sf 3~.:.1A ses / ~ t3 IGA ML Mr. Jornes W. Cook dNF File Xg i Vice President Consumers Power Company 1945 West Parnall Road Jackson, Michigan 49201 Mr. J. G. Keppler Administrator, Region 111 Office of Inspection and Enforcement U.S. Nuclear Regulatory Commission 799 Roosevelt Road Glen Ellyn, IL 60137 Mr. D. G. Eisenhut Director, Division of Licensing Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Washington, D.C. 20555 Re: Docket Nos. 50-329 OM, OL and 50 330 OM, OL Midland Nuclear Plant - Units I and 2 independent Design and Construction Verification (IDCV) Program Structural Evoluotion of the Diesel Generator Building - Assessment of the Structural Performance Capability as Potentially Affected by Settlement induced Crocking Gentlemen: Attached is our recently completed engineering evoluotion of the structural perimi.w.ce capability of the diesel generator building. This evoluction was undertaken in accordonce with the defir.ed scope of the IDCVP as part of our brooder assessment of the quality of the design and constructed product of.the 1 Midland plant Storuby Electric Power system. We are transmitting it to you because of its relevance to ongoing discussions concerni the potential effects of settlement induced crocking on the capability of the to meet intended performance requirements over its service life. We have concluded that the existing cracks, generally being of small size, are ( not Indicative of a condition that would compromise the capability of the DGB in N, i meeting its intended performance requirements. Furthermore, it is judged that pr significant future crocking is unanticipated and the DGB is expected to remain serviceable without further remedial action of this point in time. We have i, \\o h qpR yRfM5f3bMr c 1 PDR g TERA CORPORATION 7101 WtSCONSIN AVENUE BETHESDA, MAW AND 20814 301 654 8 % 0
Multiple Addressees, l reviewed Consumers Power Company's commitments to verify continued serviceability and have concluded that these are acceptable; however, we have offered certain recommendations for consideration that are intended to improve availab'e information and reduce operational constraints. Should you desire further articulation of the bases for our conclusions, we would welcome the opportunity for discussion. Sincerely, ./ .dW Howord A. Levin Project Manager Midland IDCV Program Enclosure cc: L. Gibson, CPC. R. Erhardt, CPC J. Mooney, CPC D. Budzik, CPC D. Quammy, CPC (site) R. Whitaker, CPC (site) R. Burg, Bechtel J. Taylor, NRC, l&E HQ T. Ankrum, NRC, I&E HQ D. Hood, NRC, NRR Midiond IDCVP Service List HAL/sl M' l 1 ERA CORPORATION i .I
~. SERYlCE LIST FOR MIDLAPO IPOEPEPOENT DESIGN APO CONSTRUCTION VERIFICATION PROGRAM cc: Harold R. Denton, Director Ms. Barbara Stamirls Office of Nuclear Reactor Regulation 5795 N. River U.S. Nuclear Regulatory Commission Freeland, Michigan 48623 Washington, D.C. 20555 IM I .; James G. Keppler, Regional Administrator Rwte 10 U.S. Nuclear Regulatory Commission' Midland, Michigan 48440 Region til 799 Roosevelt Road Mr. Steve Gadler Glen Ellyn, Illinois 60137 2120 Carter Avenue St. Paul, Minnesota 5:108 U.S. Nuclear Regulatory Commission Resident inspectors Office Ms. Billie Pirner Garde Route 7 Director, Citizens Clinic Midland, Michigan 48(40 for Accountable Government + Government Accountability Project Mr. J. W. Cook institute for Policy Studies Vice President 1901 Que Street, N.W. Consumers Power Company Washington, D.C. 20009 1945 West Parnall Road j Jackson, Michigan 49201 Charles Bechhoefer, Esq. i Atomic Safety & Licensing Board Michael I. Miller, Esq. U.S. Nuclear Regulatnry Commission Isham, Lincoln & Beale Washington, D.C. 20555 Three First National Plaza, Sist floor Dr. Frederick P. Cowan Chicago, Illinois 60602 Apt. B-125 6125 N. Verde Troll James E. Brunner, Esq. Boca Raton, Florida 33433 Consomns Power Cw.y 212 West Michigan Avenue Jackson, Michigan 49201 Jerry Harbour, Esq. Atomic Safety and Licensing Board l U.S. Nuclear Regulatory Commission Ms. Mary Sincialr 571i Summerset Drive Washington, D.C. 20555 ~ l Mid!ad, Miet.:g:- 486:;0 ,,p Michigan Public Service Commission i Cherry & Flynn 6545 Mercantile Way Suite 3700 e P.O. Box 30221 Three First National Plaza i Lansing, Michigen 48907 Chicago, Illinois 60602 Mr. Paul Rau l Ms. Lynne Bernabel Midland Dolly News Government Accountability Project 124 Mcdonald Street 1901 Q Street, NW Midland, Michigan 48640 p' ~~- i Washington, D.C. 2000, l 1 l l l 1
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- Mr. James W. Cook Vice President Consumers Power Company 1945 West Parnall Rood Jackson, Michigan 49201 Mr. J. G. Keppler Administrator, Region ill Offlee of Inspection and Enforcement U.S. Nuclear Regulatory Commission 799 Roosevelt Rood Glen Ellyn,IL 60137 Mr. D. G. Eisenhut Director, Division of Licensing Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Washington, D.C. 20555 Re Docket Nos. 50-329 OM, OL and 50-330 OM, OL Midland Nuclear Plant - Units I and 2 Independent Design and Construction Verificotton (IOCV) Program Structural Evoluotion of the Diesel Generator Building -
Assessment of the Structural Performance Capability as Potentially Affected by Settlement Induced Crocking j Gentlemen: Attoched is our recently completed engineering evaluation of the structural performance capability of the diesel generator building. This evoluotion was undertaken in occordance with the defined scope of the IOCVP as part of our brooder assessment of the quality of the design and constructed product of the Midiond plant Stoney Electric Power system. We are transmitting it to you because of its relevance to ongoing discussions concerni the potential effects of settlement induced crocking on the capability of the to meet Intended performance requirements over its service life. We have concluded that the existing crocks, generolly being of small sia not Indicative of a condition that would compronise the capability of the bare in i j-meeting its intended perfeirmance requirements. Furthermore, it i udged that 's l sipificant future crocking is unenticipated and the DG8 la expect to remain.# serviceable without further remediol action of this point in time. We have ~ l TERA CORPORATION 7101 WISCON$N AVENUE SETHESDA MATM.AND 20814 301.o54 8 % 0 ]
Multiple Addressees l 9 reviewed Consumers Power Company's commitments to verify continued serviceability and have concluded that these are acceptables however, we have offered certain recommendations for considerotton that are intended to improve available information and reduce operoflonal constraints. Should you desire further articulation of the bases for our conclusions, we would welcome the opportunity for discussion. Sincerely, r s Su T
- ew Howard A. Levin Project Monoger Midland IDCV Program Enclosure cc L. Gibson, CPC.
R. Erhardt, CPC J. Mooney, CPC D. Budalk, CPC D. Quammy, CPC (site) R. Whitaker, CPC (site) R. Burg, Bechtel J. Toylor, NRC, I&E HQ T. Ankrum, NRC, I&E HQ D. Hood, NRC, NRR Midland IDCVP Service List i l HAL/sl l l t t l l .)- ~ 2 l t i 1 l TE?A CC40CGATG1 l l
.. - ~ l SERYlCE LIST FOR MIDLA>O IPOEPEPOENT DESIGN APO CONSTRUCTION VERIFICATION PROGRAM Director Ms. Barboro Stamiris Harold R. Danton, Reactor Regulation cc: Office of Nuclear 5795 N. River U.S. Nuclear Regulatory Commission Freeland, Michigan 48623 Washington, D.C. 20555 Mr. Wendell Marshall .. James G.Kepoler; Regional Administrator Route 10 U.S. Nuclear Reguiotory Commission, Midland, Michigan 48440 Region til 799 Roosevelt Road Mr. Steve Godler Glen Ellyn,!!!!nois 40137 -2120 Carter Avenue St. Paul, Minnesota 55108 U.S. Nuclear Regulatory Commission Resident inspectors Office Ms. Billie Pirner Garde Route 7 Director, Citizens Clinic Midled, Michigan 48640 for Accountable Government Covernment Accountability Project ~~ Mr. J. W. Cook Institute for Policy Studies Vice President ' 1901 Que Street, N.W. Consumers Power Company Washington, D.C. 20009 1945 West Parnall Road Jackson, Michigan 49201 Charles Bechhoefer, Esq. Atomic Safety & Licensing Board Michael I. Miller, Esq. U.S. Nuclear Regulatory Commission Isham, Lincoln & Beale Washington, D.C. 20555 Three First National Plaza, Sist floor Dr. Frederick P. Cowan Chicago, Illinois 60602 Apt. B-125 m 6125 N. Verde Troll James E. Brunn. Esq.. er, Boca Roton, Florido 33433 Consumers Power Company-212 West Michigan Awnue Jerry Harbour, Esq. ~ Jackson, Michigan 49201 Atomic Sofety and Licensing Board U.S. Nuclear Regulatory Commission Ms. Mary Sineloir Wasington, D.C. 20555 5711 Summerset Drim Mid:md, Michigen 49640 Mr. Ron Collen Michigan Pub!Ic Service Commission i Cherfy & Flynn 6545 Mercontile Way j Suite 3700 P.O. Box 3022I Three First National Pfaro Lansing, Michigan 48909 i Chicoge, Illinois 60602 Mr. Poul Rau Ms. Lynne Bernobei Midland Daily News Government AccountabilityProject 124 Mcdonald Street 1901 Q Street, NW Washington, D.C. 20009. Midland, Michigan 48640 - .7 i n I n ~ ~. .ig <y wrM C@PGADON ?. .r -.7
y_ ATTAC>edNT A.Pl.320100f.REv 2 ENGIPE.ERING EVALUATION COVER SFEET Structural Evaluation of the Olesel Generator Bldg. CONT. n m mie. 031 TIT E 02 NO. OF 5 HTS. _ PROJECT: CONSUMERS POWER COMPANY MIDLAPC CCV SUPERSEDES ENC. EVA! NO. REV. NO. REVISION ORIGINATOR DATE REvi_EWED BY DATE APPROVED BY DATE O Original g@ 12/30/83 Jg 12/30/1 3,W I/4/84 =- D N EENAM 1 I I
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g TOPIC NUMBER Design Considerations, Foundations, Concrete / Steel Design Civil / Structural TOPIC TITLE METNOD/ EXTENT OF REVIEW Review of Midland project generated information including calculations, consultant l. reports, testimony, etc. Independent calculations and evaluations by IDCVP Review Team. 2. PURPOSE intended Evaluation of settlement induced cracking as it may potentially affect performance requirements and serviceability of the diesel generator building. E i CONTENTS (SEE SECTION 2., Pl.3201-001) E A8STRACT E OVERVIEW OF REVIEW PROCESS E BASE 5 FOR SAMPLE SELECTON d '~ f E SOURCES OF INFORMATION/ REFERENCES E BACKGROUFC DATA (IPPUT5, ASSUMPTIONS, RELATED CALCULATIONS) E ACCEPTANCE CRITERIA (COOES, STAPCARDS, FSAR, NRC CUCANCE, REGULATIONS) l ~ E EVALUATION (DOCUMENTATION OF REVIEW AGAINST, CHECK LIST,(ACCEPT ANCE CRITERIA) [ E CONCLUSIONS v TERACORPORATION
l l l l STRUCTURAL EVALUATION OF TIE DIESEL GEfERATOR BUILDING - I CAPABILITY APO SERVICEABILITY AS POTENTIALLY AFFECTED BY SETTLEMENT IPOUCED CRACKING t h e e. ) i = m, mdH .e 6 l I TERA CORPORATION ,O j
i TABLE OF CONTENTS PAGE i j l.0 ABSTRACT l-l 2.0 OVERVIEW OF REVIEW PROCESS 2-1
3.0 BACKGROUND
DATA AND REFERENCES 3-1 4.0 ACCEPTANCE CRITERIA 4-1 5.0 BASES FOR SAMPLE SELECTION 5-1 6.0 ENGIEERING EVALUATION 6-1 6.1 Building Performance Requirements 6-1 6.2 Acceptance Criteria 6-2 6.2.1 Structural Primary Loadings 6-3 6.2.2 Secondary Loadings - Settlement Effects 6-4 6.3 Evaluation of DGB Performance Capability 6-8 6.3.1 Available Data 6-8 6.3.2 Miaiand Project Evaluations 6-9 6.3.2.1 Evol. of DGB Based on Crocking 6-10 6.3.2.2 Eval. of DGB Based on Settlement 6-10 6.3.3 IDCVP Evaluations 6-14 6.3.3.1 Building inspection ~ 6-14 6.3.3.2 Settlement Data 6-14 i 6.3.3.3 Gross Stress Estimation 6-17 6.3.4 IDCVP Assessment / Interpretation of Results 6-18 i 6.4 Serviceability Future Capability and Monitoring 6-19 I 6.4.1 Midland Project Evoluntion and Commliment 6-19 6.4.2 IDCVP Assessment 6-21
7.0 CONCLUSION
S 7-1 ?' ~ i l I TERA CORPCRATION
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l.0 ABSTRACT An engineering evoluotion has been completed to assess the structural l performance capability and serviceability of the Midland plant diesel generator The } building tDGB) as potentially offected by settlement induced crocking. evoluotion was initiated by TERA Corporation as part of the Midland independent Design and Construction Verificotton Program (IDCVP). The performance requirements for the DGB were identified and the acceptance i criteria for meeting these requirements were reviewed. Information generated by the Midland project as well as independent calculations and evoluotions by the IDCVP review team serve os input to the conclusions of the engineering evoluotion. It was concluded that the existing crocks, generally being of small size, are not Indicative of a condition that would compromise the capability of the DGB in meeting its intended performance requirements. i Furthermore, it was judged that significant future cracking is unonficipated and the DGB is expected to remain serviceable without further remedici action of this time. Consumers Power Company (CPC) commitments to verify continued serviceability were reviewed and found to be acceptable.- Certain recommendations have been offered for consideration that are intenced to improve available information and reduce operational constroints. 4 I 0 p-s l J i l-l = I TERA CORPCRATION 3.- 1
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3 2.0 OVERVIEW OF REVIEW PROCESS This engineering evaluation was undertaken as part of a broader assessment of the quality of the design and constructed product of the Midland plant Standby Electric Power (SEP) system. The seecific scope of review documented herein j Includes a structural evaluation of the diesel generator building (DGB), the structure which houses four emergency diesel generators which are principal w.T.pw. eats of the SEP system. The main amphasis of the review is on the civi!/ structural design considerations for the DGB and how settlement induced cracking may potentially affect the intended performance requirements. l Accordingly, this evaluation addresses the following toples within the Midland IDCVP: Topic 111.5 Civil / Structural Design Considerations e I Topic 111.6 Foundations, and t i e i j Topic 111.7 Concrete / Steel Design; e therefore, representing partial fulfillment of the structural design review scope pertaining to SEP system. This evaluation has required input from other ongoing j topic reviews such as: i Topic 111.1 Seismic Design / Input to Equipment, and e i e Topic 111. 2 - 2 Wind and Tornado Design / Missile Protection; l i l however, these evaluations are documented under separate covers. The DGB construction / installation documentation reviews and the associated physical verification have not been completed and are not documented in this evoluction. Accordingly, should the results of these evaluations offect the conclusions drawn herein, the engineering evaluation will be appropriately revised. i The review concept includes a determination of the DGB periw. se T requirements and important design inputs (i.e. engineering data and assumptions); ( an evaluation of their accuracy, consistency, and odequacy; aind on evaluatior.4f-t I 2-1 i TERA CORPORATION w
? l the implementation of these commitments. Current licensing criteria are utilized as a baseline as well as consideration of various other regulatory criteria which evolved during the licensing process. Given the unique circumstance. assoelated with the DGB design and construction processes, the IOCVP ossessment used the Intent of today's licensing criteria and corresponding marg ns of safety and reliability. The review draws upon two principal sources of information; that generated by 3 the Midland project (e.g. Bechtel calculations, consultant reports, testimony, I etc.) and by the IDCVP review team (e.g. Independent calculations and evoluotions, etc.). Pertinent background data and referenc-s are documented in Section 3.0. Conclusions are reached through an integrated assessment of these dato, discussions with Midland project personnel, os well as engineering judgement. t The following individuals made technical contributions to this engineering j evaluation: S Structural Reviewer, Midland !OCVP and Senior Dr. Jorma Arros Structural Engineer, TERA Corporation Dr. William.l. Hall Member Senior Review Team, Midland IDCVP and Professor of Civil Engineering, University of Illinois i f Consultant, Midland IDCVP, Professor of Civil Professor Myle J. Holley Engineering Emeritus. Massachusetts Institute 4 ~ ! . of Technology and President, Hansen, Holley and Biggs, Inc. Project Monoger, Midland IDCVP and Manager, Mr. Howard Levin Engineering, TERA Corporation Lead Technical Reviewer, Standby Electric Dr. Christian Mortgat Power System Structural Review, Midland IDCVP and Principal Structural Engineer, TERA Corporation ~ i 2-2 1 TERA CORPORATION L l i m _.m.,, 4 mw y ,.y_ y.. _.,_,,,.n.,y_
i-l The following chronology of external interactions transpired as port of this review. 1 Date Activity l August 24,1983 Review team members observe NRC task force l meeting on structural rereview of DGB of Bechtel's Ann Arbor, Michigan offices. November 17,1983 Review team members inspect diesel-generator building. \\ Review team members discuss civil / structural design j November 18,1983 considerations for the DGB and collect information .3 at Bechtel's Ann Arbor, Michigan offices. i December 12-16,1983 Review team members review DGB finite element 'i and seismic stick models at Bechtel's Ann Arbor, 4 Michigan offices. I i l t i i i t 1 t \\ l 1 l l .F l '\\ 2-3 h t. I TERA CORPORATION b i ?
1 J +, 3.0 BACKGROUbD DATA APO REFERENCES The following table identifies references and sources of information that were k selected for review and served as input to this engineering evoluotion. The numbers in the left margin correspond to references made within the body of the engineering evoluotion. i i e l q I s
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--.... ~, ATTACHIAENT 8.Pl-Hel.eD4.f(V 2. REFERENCES / SOURCES OF IWORMATION ~ l m.7-2 TOPIC TITLE Civil / Structural Deslan Considerat ions. Foundat ions. TOPIC NO. 111.5-2.111.6-2. ppcg I OF 3 O 12/30/8 I urI al. of the Diesel Generator Blde ONT.lD.NO.320I-001-031 REV DATE ENGIEERING E AL AT i WHERE/HOW DOCUMENT ORIGINATING ORG./ IDENTIFICATW REV. DATE l TITLE LOCATED TYPE AUTHOH NUMBER File 0455.16/B1: 3 1. Bechtel Serial 22423 48 5/83 Final Safety Analysis Report Ann Arbor FSAR i 10/2) Report on the Review of the Diesel 81 Generator Building, Midland Docket Report 2. NRC 50-329/330 0 8/24/ Hidland Units I and 2 Ann Arbor, 11/18/85 0 81 Diesel Gen. Bldg. Exec. Summary Meeting 3 Bechtel T stimony of Karl Wiedner for the Docket Testimony testimony at pp 9/8/ Hidland Plant Diesel Gen. Bldg. 4. Wiedner 10804-11007 0 82 File 0485.16 6/1/ Technical Report-Structural 5. CPC B3.0.3, Serial 0 82 Stresses Induced by Differential CPC, Jackson Report 17228 Settlement of the Diesel Generator Bldo. '98 '"9 6. CPC 3 9/79 f[(("'" Docket Report ng de 7 ACI Ati 318-77 Bul Library Standard e e nc e 8. ACI ACI 349-76 k$iat$3NEN2e'S$c!uN$8' 58I*El Library Standard 7/15/ Project 9 TERA PI-3201-003 3 g3 Engineering Program Plan IDCVP Proj. Files Instruction 2/11/ Eval. of the Effect on Structural Transcript at 0 Strength of Cracks in the Walls of 10950 Report 10. Sozen 82 the Diesel Generator Building I ny ph Peck {0 Report II. Peck O O 2 Trankcriptat Report 4/19/ E iStsofkracksonServitructuresatMI0 land il20 0 82 a 12. Corley, et. al. ty o Plant 13 CPC FSAR Ch. 16 45 9/82 Tech. Spec. 16.3/4.13 Settlement Ann Arbor FSAR i Monitorina DGB Areas for Crack Widtla Monitor-Partial / oO Ing During Operation of the Plant Ann Arbor,II/18/83 Corres. 14. CPC Exhibit 29R 0 Meeting l/9/ Diesel Gen. Bldg. Reanalysis Using Ann Arbor Calc b 15 Bechqel \\ <.i DQ-52.0(Q) 2 3 Revised Set tlement Load Case Z k
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.____g,_, ATI ACleaENT 5, Pl.32SI.881. 54V 2. REFERENCES / SOURCES OF lif0RMATION i 3 topic TITLE Civil / Structural DesIan Consideratlons. Foundat lo'is-TOPIC NO. I PAf2 2 OF ENGNEERING EYAI.t[A N af Na1. of the Diesel Generator aldo rONT. lD.NO.3201-001-031 FIEV DATE 0 12/30/8; ORIGINA ORC./ IDENT W REV. DATE TITLE OC 5/2/ DGB Settlement Analysis - Load l 16. Bechtel DQ-52.l(Q) 1 82 Case lA Ann Arbor Calc [2 ggeIB 12; S '***" ^" ~ 17 Bechtel DQ-52.2(Q) 0 Ann Arbor Calc h28' DGB Surcharge Condition (2A) Ann Arbor Calc 18. Bechtel DQ-52 3(Q) I h28' DGB Settlement for 40 yr Life (28) Ann Arbor Calc 19 Bechtel DQ-52.4(Q) O h7/ DGB Analysis for Uniform Torsion Ann Arbor Calc 20. Bechtel DQ-52.6 (Q) I $7/ gB, Anal. Imposing 40 yr displace-Ann Arbor Calc 21. Bechtel DQ-52.7 (Q) I [' [f$c(fy*oJS SeydI"9 Ann Arbor Calc 22. Bechtel DQ-12(Q) I c s;/18 Optcon ACl-349 - Nonseismic Load 23 Bechtel DQ-52.0-C7(Q) 0 82 Cases 7 Diesel Gen. Bldg. Ann Arbor Calc Settlement Analysis (partial) DGB Load Combination (partial) Ann Arbor Calc 24. Bechtel DQ-52.0-C2(Q) 0 5/12, DGB Settlement Analysis - Load. 25 Bechtel DQ-52.2-05(Q) 0 82 Case IB - Free Body Analysis Ann Arbor Calc 1 of Trial #3 (partial) 9/28/ DGB - Settlement Case 2A - Free 26. Bechtel. DQ-52.3-C7(Q) 0 83 Body Analysis on Best Fit (Sur-Ann Arbor Calc i charge) (Partial) I 5/12/ DGB Analysis - Free Body Analysis 27 Becntel DQ-52.4-C4(Q) 0 82 of Best Fit 40-Year Case Ann Arbor Calc h/II' DGB Roller Support (FSAR Criteria) Ann Arbor Calc 28. Bechtel DQ-23-C4(Q) O i 29 Bechte' S-110 1 11/)) Static & Dynamic Spring Constant 82 of DGB for Structural Stress Anal. Ann Arbor Calc j I 2/22/ Update of Settlement Prediction g 30. Bechtel S-175 3 82 DGB - After Surcharae Removal Ann Arbor Calc a gI5/ g t g g DGB Between 9/14/79 31. Bechte[I k E-238 0 7 i. I l 'l4 1;
~ .. a..:. .-.L ATT ACHMENT S, Pl.MSI-801, IdV 2. REFERENCES / SOURCES OF IWORMATION 8 Civil / Structural Design Considerations. Foundations. TOPIC HO. ~ ' 3 OF 3 TOPIC' TITLE Concrete /5tructural Steel 0 12/30/8: ENGlEERING EVALUATION Ktructural Fual_ nf the Diesel Ceneratnr R 1 dar'ONT. lD. NO. 3201-001-031 REV DATE WHERE/HOW DOCUMENT l ORIGINATING ORG./ IDENTIFICATW REV. DATE TITLE AUTHOR NUMBER LOCATED TYPE h2/ e c Analysis of DGB and DG 32. Bechtel** SQ-147(Q) I p h9/ gBj{guytjynofSettlement 33 Bech t'el DQ-52.II(Q) O Ann Arbor Calc g/5 Settlement Data for DGB Ann Arbor Drawing 34. Bechtel SK-C-2343-1/24 r Agt.2toTestimong File 0485.16 8/2/ Midland Concrete Wall Repair 35* CPC o Corley @ p.ll20 Letter Serial 18371 0 82 Program Trip Report - Midland DGB Struc-h29/ tural Design Audit Docket Report 36. NRC 50-329/330 0 k*735h088'**' t i 1975 Properties of Concrete Library Text Book 37 Neville gj 30s uraIAna1],s),,sofDiesel gy{ Proj. 38. TERA 3201-003-007 0 Calc , n,, 8/12/ Response to NRC Qu'estion 26 Re: Ann Arbor Calc 39 Bechtel DQ-14(Q) I 83 Diesel Generator Buildina hfII' y dea $ Ina " yM Ann Arbor Calc 40. Bechtel DQ-23(Q) I t 4 e 9 O gaa t z 1i I
m-__ 4.0 ACCEPTANCE CRITERIA i 4.1 LOAD COMBINATIONS The loads and load combinations employed for the original design and analysis were provided in the FSAR subsection 3.8.6.3 (revision 0, dated November 1977). These original design criterio did not contain settlement effects. Four odditionul loading combinations were established cad cornmitted for consideration as a result of Question 15 of the NRC Requests Regarding Plant Fill of September 1979. These looding combinations combined differential settlement with long-term operating loads and either wind or the operating basis earthquake (OfsE). As Wiedner (reference 4) and CPC (reference 5) point out these expressions are more stringent than the requirements of ACI 318 (reference 7), but less stringent than ACI 349 (reference 8). In the latter cose the fooding combinations combine differentloi settlement with extreme loods such as tornadoes and the safe shutdown earthquuke (SSE). Subsequently, in response to Question 26 of the NRC Requests Regarding Plant Fill, a commitment was mode to undertake o separate structural reonalysis of the DGB in accordonce with ACI-349 as supplemented by NRC Regulatory Guide 1.!42 for comparison purpose only. The following foods were considered in the reonalysis: (a) dead loads (D) (b) effects of settlement combined with creep, shrinkoge and 4 tenperature (T) l (c) live loads (L) (d) wind loads (W) (e) tornado loods (W') i-(f) OBE loads (E) (g) SSE loods (E') (h) thermal effects'(To) 4-1 i l TERA CORPORATION i I er tr wa-
It is to be noted that thermal effects appear twice by virtue of the manner in which the loading combinations were developed. The food combination estab!Ished and committed to in response to NRC Requests Regarding Plant Fill, Question 15 are as follows: l a. l.05 D + 1.28 L + 1.05 T l b. l.4 D + l.4 T c. l.0 D + 1.0 L + 1.0 W + 1.0 T d. 1.0 D + 1.0 L + 1.0 E + 1.0 T I A number of load cases appearing in the load combinations for Seismic Category I structures listed in FSAR Subsection 3.8.6.3 do not occur in the diesel generator building and other load combinations con be eliminated from the l analysis offer comparison with more severe loods or lood equations (reference 5). 1 As a result the remaining load combinations to be considered are: e. l.4 D + 1.7 L i f. 1.25 0 + L + W) + 1.0 To g. l.4 0 4 L + E) + 1.0 To 4 h. 0.9 D + l.25 E + 1.0 To _ i. l.0 0 + L + E') + 1.0 To 1 J. 1.0 0 + L + W') + I.0 To 'j 4.2 ALLOWABLE MATERIAL LIMITS l in accordance with regulatory requirements, the maximum robar tensile stress allowed in the diesel generator building rebor should not exceed 0.90 f (where fy y equois yield strength) for computation of section capacities. Because the diesel l generator building rebor has an f value of 60 ksi, the maximum allowable tensile f-j. I y rebar strees due to flexural and axial loods is 54.0 ksi. Accordingly, reinforced concrete section capacities for the diesel generator building were based on this_ a d 4-2 1 1 ERA CORPORADON h q
..x a maximum allowable rebor stress value (54 ksi), a design concrete compressive strength of 4000 psi and a maximum allowab:e concrate compressive strain level of 0.003 in./in. 4 8 1 f 4 I J l 1 I r t i i % e I l ^ 1 A 4-3 TERA CORPORATION w I j. e-
i 5.0 BASES FOR SAMPLE SELECTION The diesel generator building (DGB) was selected for review because it serves on important support function in providing protection against external hazards for the diesel generators which are integral components of the Standby Electric Power (SEP) System. The DGB falls within the sample selection boundaries defined in the Engineering Program Plan (reference 9). Commitments were made in this reference to review civil / structural design considerations for the 4 DGB Including foundations and concrete / steel design. Based on programmatic commitments, emphasis is to be placed on structural performance and not detailed sail mechanics aspect; which are not within the serpe of the Midland independent Design and Construction Verification Program (IDCVP). This engineering evaluation addresses the potential effects of settlement induced f cracking on the ability of the DGB to meet its intended performance requirements. Accordingly, verification of the Midland project treatment of the settlement / cracking issues which have offected several structures of the Midland site is oddressed herein. While a structural review of the auxiliary building is also within the IDCVP scope os part of the Auxiliary Feedwater (AFW) system review, the specific settlement / cracking issue os it may offect the auxiliary building is not being treated directly by the IDCVP. Thus, this evoluotion of the DGB represents the IDCVP sample uddressing the settlement / cracking issues. It is estimated that approximately one third of 'the project's calculations and evaluations addressing the structural design of the DGB were selected for i review. Emphasis was placed on the selection of portions of the project's evaluations that address controlling design conditions (e.g. Important load combinations producing the highest predicted stresses or strains, as appropriate). l Principal project consultant reports were reviewed as well as other docketed Information that documents CPC commitments to the NRC (see section 3.0). = L 3 I ~ f 51 i LJ m c mpc m on a
l 6.0 ENGDEERING EVALUATION 6.1 BUILDING PERFORMANCE REQUIREMENTS The diesel generator building (DGB) is a two story reinforced concrete box t>p building portitioned into four boys, each ' boy containing one diesel powered electric generator (see Figure 6-1). The purpose of the diesel generators is to f supply ston&y electrical power to operate the Midland plant during power outoges and to p* ovide the necessary power to ere.ure safe shutdown of the plant in the event of a design basis event. Accordingly, the diesel generators and the f DGB are classified as Seismic Category 1, and as a result must maintain functionability during external events such as earthquakes and tornadoes. The DGB provides protection for the diesel generators and associated supply ano service lines, instruments and equipment, assuring ready availability of this supplementory power source. This protective function includes not only the normal sheltering of building contents from rain, snow, wind, and ice, but in addition, resistance to the effects of earthquakes and tornadoes including tornado generated missiles, it is these latter effects which are of principoi structural interest, and which dictate a more massive type of construction than normally would be employed for shelter from the commonly considered weather ^ extremes. i The DGB was founded on plant fill and constructed between the Fall of 1977 and the Spring of 1979. During that period it was discovered that the building was l experiencing on unusual rote of unequal settlement, and duct bonks had mode contact with the footings which led to building distortion and reinforced concrete cracking. The details of the settlement monitoring, duct structural modifications, and surcharge consolidation program are described in detail in references 3 and S. t
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I l 6.2 ACCEPTANCE CRITERIA i. In response to applied loadings (dead, live, earthquake-induced, wind, tornado, tornado missIIes) and certain secondary effects such as settlement, local internal forces are developed throughout the structure. These local forces consist of in-plane forces, sometimes termed membrane forces, and out-of-plane forces, i.e., transverse shear forces, and bending moments. In design it is customary for the internal forces associated with a particular fooding to be multiplied by a specified "lood factor" and these load factored sets must be combined for the several specified loadings to obtain what may be called a local internal demand. i This demand must not exceed the local " strength", i.e., capacity of the structure. The acceptance criteria consists of the following: I l Statements of the several different load combinations that must be i e satisfied, and the load factors to be applied to each of the loodings l (dead, live, tornado, etc.) within that combination. i e Specific expressions, or procedures, for determining the local strength which must not be exceeded. it may be noted that certain of the specified load combinations focus on I serviceability of the structure. These do not include the infrequent extreme ~ j loadings, but Irespcsate relatively large load factors to assure a modest demand / capacity ratio for (unfoctored) loadings experienced in normal operating i conditions. For the combinations which include extreme and rare foodings, safety in the sense of protecting personnel and equipment, yet retaining / functionability, is the primary consideration rather than serviceability. Thus t crock widths, including those widths which may reflect yielding of the j tension robars, are not a consideration provided that they do not imply a ] reduction in the local strengths. Accordingly, such specified factored lood cornb' nations typically incorporate smaller specified load factors. In effect a ,)- larger demand / capacity ratio for these unfectored lood combinations is l 3 [ j occeptable for these rare conditions. 4 ] 6 .] TWA CCMGATICW 3 I
It should be noted that the specified expressions, or procedures, for determining the local Internal strength do not typically include any direct limitation on rebar j tensile strain, or on crock widths which occompany such strain, although there ore Indirect limitations for certain conditions. (Note that the limiting condition specified by various ACI codes (references 7 and 8) are related to maximum allowable concrete compressive strains where a value of 0.003 in./in. is 4 specified). This strain reflects the fact that certain components of local strength are not sensitive to rebor strain but only to the tensile yield strength of the rebars. As an example, full development of the local out-of-plane bending strength of a slab, or beam, with a modest rebar ratio may imply tensile rebor j strain into the yield range. Indeed this is specifically recognized by codes which specify that, for rebor strains in excess of the elastic strain at yield stress the stress must be assumed to be constant at the yield stress value. This approach often is overlooked because, for the majority of local conditions of interest it is i computationally much more convenient to evaluate local sections on the assumption that the steel strains remnIn within the elastic range, and to compute i rebar stresses associated with the particular factored load combination aemand rather than to compute the local section strength, per se. In some cases this approach I's slightly conservative, but often there is no difference whatever. However, the fact that there are circumstances, where small tensile rebar strains into the yield range occur, yet are acceptable, and do not degrade the required local strength, may be unrecognized because of the focus on elastic behavior inherent in the computation process. Margins of strength, as reflected in codes, are implicitly based on the ductile teehavior of structural systems as Just noted. I l 6.2.1 Structural Primary Loadings i i The DGB must resist the following principal primary loadings: e Gravity-induced dead and live loods .j e Earthquake-Induced loads e Tornado-Induced differential air prestare e Tornado-borne missiles i 6-3 L 1 ERA CORPORATK)N -e---,. -,,.w,.----- --.,-.--.,---..,r,-r-.,,w--v.,,e--_.--re-g-eye-w----.
Gravity-Induced foods produce out-of-plane shear forces and bending moments in the floor and roof systems and in portions of the walls immediately adjacent thereto. These foods also produce in-plane forces in the walls and, of course, bending moments and shear forces in the strip footings. Earthquake-Induced loads produce in-plane forces in the walls which are substantial, and more modest in-plane forces in floor and roof slabs. They also produce out-of-plane shear forces in floor and roof slabs and walls. Tornadic winds produce in-plane and out-of-plane forces in walls and roofs. Tornado-induced differential air pressures are the principal source of out-of-plane shear forces and bending moments in floor systems and walls, and they also produce in-plane forces. l Tornado-borne missiles produce highly localized out-of-plane fooding of the walls. The capacity of the wall to resist such missiles is evaluated Independently of all other loadings. j 6.2.2 S w.w A f Loadings i Restrained non-lood-Induced volume changes (e g., due to concrete shrinkoge and l or temperature strains) may produce internal forces. It has long been recognized that these forces rarely have any iignificant effect on the local strengths, and in most cases they are neglected. The reasons relate directly to the ductility of I the tension rebars if the local strength is mobilized, by an imposed set of local f demand forces, it typically will be the some whether or not the forces associated with the non-load induced effects are included. The difference will be that the tensile rebar strain, including some yield strain, will be larger when these secondary forces are included. This yielding has the effect of decreasing, and sometimes completely eliminating, the local forces which were initialy introduemi by the non-load effect. It is for this reason that the forces associated with such non-lood induced effects often are termed "self-relieving" or j-secondary. ? j r i I f N TERA CORPORATION il j
l In the design of most reinforced concrete buildings the local internal forces arising from restrained shrinkage and thermal strains as well as that induced by se'ttlement are not included in the application of the strength criteria. In the design of nuclear safety related concrete structures it is the accepted practice to account for through-the-wall thermal gradients, although shrinkage effects are not typically included. Even accounting for the thermal gradients is a conservative requirement the justification for which is at least debatable. l However they were accounted for in the DGB design as required by the acceptance criteria. It may be noted that underlying codes, from which the occeptance criteria were developed, typically called for inclusion of these non-4 lood-Induced forces with the lood-induced forces only where their structural effects may be significant. In the case of the DGB it may reasonably be debated i f whether such effects are indeed "significant", as envisioned by the code. In the initial design of the DGB it would not reasonbly have been assumed that the forces associated with foundation settlement could be significant nor, that they should be included with the food-induced forces in the factored load combinations. Clearly, the building was designed for continuous support on what was intended to be a relatively homogeneous soil medium. Thes the designer could justifiably assume that there would be little if any redistribution of the upward soil reactions on the strip footings due to major point-to-point variations in local stiffness of the supporting medium. When the building was onhy partly completed it became evident that such stiffness variations did, in fact, exist i.e., j a very stiff support at the location of footing contact with ducts, together with i poorly consolidated soil (Iow in stiffness, and non-uniform) elsewhere. These conditions caused an extreme example of non-uniform settlement which did indeed induce Internal forces sufficient to cause cracks in the walls of the then j partially completed structure. Upon noting that the settlement had led to Interference between the foundation j l and buried ducts, the unintended footing-to-duct connections were physically disengaged and the unsatisfoetory foundation condition was corrected by a surcharge loading procedure. It is to be noted (reference 36) that the su' charge h __ r / loading procedure begon on January 26, 1979, incrementally, and that 1 i l 6-5 TERA CORPORATION t t e 4 t g e.---e-. , +, -,,,, ,-~w -e a -a + -, .---or,.,- - - -,...-e, ,-,,,e,----
..s I F construction of the DGB continued thereafter. The final surcharge placement took place between March 22,1979 and April 7,1979, just as the roof and parapet
- onstruction was completed. The subsequently completed DGB structure has been in place, in its completed condition for more than four years with no indications of additional distress in any way comparable to that associated with the footing-to-duct contact and the poorly consolidated soil. It may be argued that the structure now is supported as was intended at the time of design, that the effects of any future differential settlement will not be significant, and that the effects of such cracking as developed in the partially completed structure also are not significant to local internal strengths relied upon to resist the forces associated with applied load combinations. From all this it would naturally i
follow that the Internal forces induced by differential settlements need not necessarily be included with the food-induced forces in the combinations speelfied by the acceptance criteria. These arguments may be justified but, in fact, there is a licensing commitment to include the settlement-induced forces in the relevant lood combinations. r Since the internal forces induced by a specific non-uniform settlement are self-relieving (as was desseribed earlier, for thermally induced forces), why must they be included; i.e., when may their effects be "significant". In some structures the i magnitude of possible future settlement may be uncertain, and there may be' little or no prospect for monitoring of the settlement or the state of the structure during its service life. Accordingly, inclusion of settlement-induced forces in the design would be appropriate to limit the possible development of f structural distress which would bu costly to repair, or which in some special cases, like a containment structure, may affect functionability by creation of large liner strains. For other structures these forces might prudently be included t to avoid excessive yield strains in the tension rebars (and the associated large i crack widths) which might degrade the local internal strength under some set of the local ' internal forces associated with applied loods, particularly if no monitoring of the structure for such effects could be ar.ticipated. For the DGB structure the principal structural elements are relatively accessible, and a monitoring program is planned. Nevertheless it is required to t l 1 i O 1 ERA CORPORATION g i' y u .L..- ---..,2- .1
dernonstrate by applicotton of the relevant occeptance criteria, including the effects of differential settlement, that the local Internal strengths are not presently degraded and are unlikely to be degraded by any probable future differential settlements. The acceptance criterio do not include any specification of the method by which the ossociated internal forces are to be determined. This is on important consideration in any effort to apply the acceptance criterio. There are essentioly three alternatives: c) One may assume o mognitude and distribution of differential settlement and impose this displacement pottern upon the structure. In contrast to the situation of the design stage the onclyst for the DGB has settlement measurements to consider in arriving at the postulated differential settlements to be used. 5 b) One may postulate one or more perturbations of the distribution of upward soli reactions associated with dead load which may be associated with differential settlement, and determine the local internal forces for each it will be opporent that this approach produces the forces due to dead loads plus differential settlement. This is not on unreasonable approach, if sufficient attention is given to parametric variations, particularly if the analyst locks dato on differential settlement which he considers sufficiently precise to use directly in method-(o). c) One may postulate the local internal forces directly from the observed condition of an (existing) structure; i.e., the crack widths in the DGB. This is on option clearly not ovoilable of the time of design. The method of imposed differential settlements may lead to unrealistically large internal forces unless the onelysis con account for cracking, and time-dependent l concrete properties. The cost-benefit of such on analysis may not be justified, particularly if other suitable options (b or c) exist. The method of analyzing the dead food condition for several postulated distributions of soil reoction is suitable, but it muy be difficult to choose sets of distributions which cover the possible differential settlements but which bre not n, unjustifiably extreme. ~} TERA CORPORATION 1
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f t { For the DGB, which has been observed in its completed state for more than four years, inference of the internal local forces from the condition of the existing structure (c) seems to be the most attractive approach. It is the most direct. It is particularly attractive since any significant changes in the condition of the structure will be observable during its service life. Observations related to this approoch follow. 6.3 EVALUATION OF BUILDING PERFORMANCE CAPABILITY the The perferirar.cs capability of the. structure is to be assessed in two steps: first one considering the building in its present state and the other addressing its structural Integrity and serviceability over the next 40 years. Inputs to the evaluation are keyed to a number of elements such as: ovailable physical data, analytical studies, understanding of concrete behavior and engineering Judgement. 6.3.1 Available Data i The most important data available to estimate the present state of stress in the DGB consists of: l. Observations of the building as it exists today. 2. The record of the crack monitoring program.
- 3.. The settlement history of the building.
h The cracks have been surveyed on several occasions (Reference. 3). The l maximum crack width recorded during the monitoring program prior to isolation t of the duct banks was 28 mils. After the isolation of the duct banks, the crocks decreased in size (testimony Peck and Weidner references 11 and 4 respectively) Implying a stress decrease in the higher stressed areas. Presently the largest cracks are of the order of 20 mils. An evaluation of the existing cracks has been N __ performed by two Bechtel consultants, Dr. Mete Sozen (reference 10) of the 7 j, l University of Illinois and Dr. W. Gene Corley (reference 12) of the Portland Cement Association. 1 ERA CORFORATION H A% WA - = a m y y y g
j' )' .n....._. ~ 1 The building sedlements have been monitored at close intervals during the construction period and thereafter. Figure 6-2 presents the location of the settlement markers indicating where survey measursments are taken. The data spans over a period of 5 years with measurements taken approximately every other week. This large amount of data allows one to follow the settlement j history through the stages of construction, duct bank isolation, surcharge period, dewatering, and up through the present. It also provides a means of assessing The Midland potential random and systematic errors in the measurements. project has concluded that significant errors exist in the measurements due to a verlety of circumstances. A study of these data is presented in the following section. 6.3.2 Midland Project Evaluations The Midland project followed two separate approaches to estimate the state of stress in the building: study of the cracking history e study of the settlement history. e The future state of stress due to settlement was estimated based upon predicted \\ settlements. l t i 6.3.2.1 Evaluation of DGB Based on Observed Cracking In its present condition the DGB has cracks which appear to be settlement-induced or settlement-intensified, generally arising during the early construction l phases. Maximum present crack widths are reported to be about 20 mils, and Dr. Sozen (reference 10) has shown that the associated robar stress as estimated in a . region of numerous. cracks, adjacent to a duct bank penetration of the center wall, may be judged to be between 20 and 30 ksi. We find his evaluation to be reasonable incorporating techniques that are state of the art, widely accepted h _-- / and supported by laboratory tests. Dr. Sozen also has argued that the presence of initial cracks doas not degrade the capacity of a reinforced concrete element
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= _ I in any of the important structural modes; i.e., direct tension force, direct compression force, in-plane shear force, and out-of-plane bending. Again, we j ogree with Dr. Sozen that procracks of the width thus for evidenced in the walls l of the Midland DGB would not significantly degrade capacities in the several modes developed by the principal foodings, onc in their required factored f combinations, t i Dr. Sozen did not specifically address the possible influence of an initial rebor f stress which is associated with a self-relieving internal force, that is, a force l caused by foundation settlement. He does not Indicate his opinion whether or l not the self-relieving ir.ternal force implied by the initial rebar stress should be Included with the internal forces due to applied loadings or can be neglected because it is self-reIIeving. It is our understanding that the Bechtel evaluations of the DGB for the effects of dead load plus foundation settlement did ret utilize the initial rebar stress magnitude estimated by Dr. Sozen but rather computed it based on the settlement history of the building. 6.3.2.2 Evaluation of DGB Based on Settlement History The settlement effects were modeled by Bechtel into the structure considering four distinct time periods. Measured or estimated settlement values f corresponding to each of the time periods were used: e Case I A: 3/28/78 to 8/15/78 (Structure partially completed to elevation 656.5') - A long hand calculation was used to determine the stresses due to early settlements. The structure was assumed fully cracked and the stresses in the reinforcing steel were==W based upon local strains corresponding to an imposed differential i settlement (reference 16). e Case IB: 8/15/78 to 1/5/79 (Structure partially completed to elevation 662.'O.)- The duct banks were seperated from the structure which caused the north wall to settle rapidly. (reference 17) i 'i .] ? ~ a 6-10 g ~J ~ 1 ERA CORPCRATION N-.
e Case 2A: t/5/79 to 8/3/79 (Structure in process of completion.)- t Surcharge period. (reference 15) Case 28: Forty year settlement composed of: o measured settlements from 8/3/79 to 12/31/81, and e predicted sagy consolidation settlement from 12/31/81 to e 12/31/2025. (reference 19). ) The last three analyses used - a finite element model having stiffness r i l corresponding to an uncracked ccadition, in these analyses the foundation stiffnesses have been varied, in an iterative process, to achieve final settlements approximating a set of target settlements. These target settlements were based upon a linear best fit through the measured settlement data. The analyses have 'f been criticized (reference 2) because the analytically predicted settlements do I not match variations in the measured settlements, it is appropriate to ask 1 1 j-l whether the iterated non-linear foundation stiffnesses are realistic since the ~ ~ ~ _ target settlements were not the measured settlements but a linear best fit, essentially assuming rigid motion of the North and South walls. The best fit data were utilized in an attempt to deal with scatter in the measured data. Such scatter potentially due to either random or systematic errors was estimated to be of the order of plus or minus 0.125 inches. In our opinion the descrit ed method of accounting for foundation stiffnesses 2 utilizing the linear best fit data rnay not be sottsfactory for correlation with b. l observed cracking in relation to differential settlement. We concur that f settlement measurements may not be of sufficient accuracy to permit a [ precision computation of settlement-induced internal forces. Furthermore, the marker locations are spaced at wider intervals than would be desirable as input l to analyses of building stroins. Nevertheless, the general level of stress implied by the mognitude of crocking is not in controdiction to that which may be derived from the measured settlement data, realistically accounting for M' flexibility including consideration of phenomena such as creep (see section 'I ~ 6-11 TERA CORPORATION - g L'? -.- -d .w,_ s eg, ..r,-. -w.~ ,..,w,.,, e ..n..,.g4
6.3.3 for a more detailed discussion). As discussed in Section 6.2.2, an exact determination of ww.dsy stress levels is of lesser importance given the nature of the loading and the fact that capacity is not adversely offected. ) In separate sensitivity studies Bechtel engineers considered among others, the i-two following cases: The zero spring condition analysis (reference 3) which investigated e A zero soil the structure's ability to span any soft soil condition. spring value was used at the junct;on of the south wall and east center wall. Soll values were increased linearly back to their original value within a distance of approximately 15 feet from the zero spring. The stresses in the building underwent moderate increase in the area of the bridging. In our judgement this is a reasonable approach, but one may ask whether the size and locations i l of such postulated " soft" zones were bounding. 2 1 The imposed 40 year settlement analysis (reference 21) which forced l e the building to match the predicted settlement values at 10 points 4 along the foundation. This analysis led to very large reaction forces l of the points of imposed settlements, and some of these acted downward on the structure, i.e., implying tensions in the soil, which is l ] not possible. Moreover, the analysis ind!cated very large rebor tensile stresses, where at several points a multiple of the yield strength was Indicated. Of course % structure does not display the l j For very wide cracks which would accompany such high stresses. these reasons Bechtel engineers concluded that the settlement measurements cannot be an occurate representation of the octual I l l settlement nonuniformities. i q We have noted that the settlement data may not be an odequate basis for computing settlement effects. However, we believe the described analysis exaggerates the effects of the displocement input data which was questioned the project. Our reatens are that the analysis assumed uncrocked concrete and l t 6 12 -i =* c=- j e
3 E w am used the short-term concrete modulus of elasticity. Appropriate reduction of ' -the concrete mddulus, to reflect creep under sustained loading, would have lead ^ ho reactions and internal forces perhaps 50 percent less than were obtained. Decreases in stiffness associated with cor. crete cracking could result in additional large reductions. An excellent discussion of the physical and engineering significance of creep is found in chapter 6 of reference 37. Perhaps more important, rebor stresses appear to have been computed on the assumption that the local Internal tensile forces developed in the uncrocked conc <ete are 'unreduced by cracking, i.e., this unreduced force is imposed on the rebors in our judgment this is not the best physical representation. The rebor . stresses are expected to 'be more nearly indicated by the local strains in the concrete (uncrocked) than by the forces in the concrete (uncrocked). Thus, the rebor stresses are better opproximated by the product of steel modu!us and f concrete strain (uncracked);'I.e., by the product of modular ratio, n, (Youngs modulus of the steel / Youngs modulus of the concrete) and concrete stress. ~ fsenfe r in contrast we believe that the following expresston was used fs k lfc { P ) r where p is the' reinforcement ratio (rebor area /section area). This later expression grectly overestimates rebor stress. To illustrate, for p = 0.0043 and n 3 = 8, the suggested approach gives rebor stress about 1/30 of the Bechtel computed value. While reality is like_ y in between, and the former expression is l 4 app'roximate, we believe that it[ is a closer representation of the ' existing situation. t q j- ~ L f ,l '_ 6-13 f h j-7 _;. i. TERA CORPORATION i l y( r, ,,s 4 s A bs \\ \\ ^ ,n ',w 4, j. u, ~ '
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1 6.3.3 IDCVP EVALUATIONS In addition to reviewing the information generated by the project and the studies performed by others, the IDCVP concentrated attention on two major elements in the review processa j Observations of the building and its present state of cracking, and e e The settlement history of the building. Settlement data Gross stress estimation i l 6.3.3.1 Building Inspection A careful inspection of the building was performed together with a review of the i crack mapping data. As it exists at present, many cracks of small size are evident in the building but there is no evidence to support that these cracks are Indicative of a high state of stress in the building and degraded capacity. Post experience and laboratory tests indicate that concrete elements in a state of distress -particularly stiff shear walls of the type in the DGB - exhibit large deformations and cracks, much greater than present in the DGB. This would probably be accompanied by scabbing and other phenomena which are not apparent 5 the DGB. i Our conclusion from visual inspectio.n of the building is that its state of stress is f low and would not impair its performance and functionability. A body of I relevant Information developed in industry, university and government programs 1 and structural experience supporis this conclusion. ] 6.3.3.2 . Settlement Dato l .l A study of the settlement data recorded between 11/24/78 and 8/28/80 is j presented in reference 5. We reproduced and expanded this analysis to include M t i - the most recent data (reference 38). The two time periods covered were from i l. i 6-14 ,-j TERA CORPORATION ?
5/12/78 to 9/14/79 (reference 33) and 9/14/79 to 8/23/83 (reference 34). Our goal was two folds (l) assess the overall deformation of the building with time and (2) estimate the random error present in any one set of measurements. We studied the following dato. 1 I. Cumulative settlement recorded overtime. l 2. Incremental settiement between successive readings. 3. A measure of the curvature between any three l consecutive markers along the foundation as it varies with time. The curvature d"; of marker i is defined as: d"1 = 0.5 (dg.l + d + l} - di i 1 where d is the total settlement. i The quantity d" equals zero when the three points are on a straight line; it remains constant in time if the three points move as a rigid body. 4. A measure of the deformation of the building with respect to its rigid body motion. The rigid body motion is " removed" by computing the vertical position of all markers with respect to the plane defined by three corner markers. This analysis was done both for each incremental reading and cumulatively. kn upper limit of the random error in any set of readings is given by the j maximann difference of incremental settlement between any two markers from i one reading time to the next. When the building has not experienced any settlement between two readings, this quantity is the rondom errors it bounds it otherwise. At the beginning of the record, this quantity is large where the j building was undergoing large differential settlements and reading occurocy might have been reduced by n,orker trcnsfer necessitated by the placement of surcharge. However, this quantity decreases rapidly and offer June 1979 is never greater than 0.150". After the removal of the surcharge for the readings starting 9/19/79 which we will refer to os the recent readings, the random error is smaller l than 0.125", 93 percent of the time which would give a random error of about : / ~ ~~ 1/16 of an inch. This implies that a higher level of confidence con be given to the recent measurements. l-6-15 1 f EA CCWCRADON U '\\;^
I Jumps in readings from one period to the next are sometimes large implying that the building would rapidly move up or down by a uniform amount. These jumps are attributed to systematic errors in locating the reference elevation. 4 Figure 6-3 shows the incremental settlement for 6 time periods between July 1978 and August 1979 for the south wall of the DGB. The first three j measurements show large differential deforn ations and introduction of curvature in the wall. The latter ones show stabilization of differential settlements implying that the wall is still settling but as a rigid unit, introducing little additional Iglane bending. For more recent recordings the stabilizing trend is even more noticeable. Study of the foundation curvature variation and deformation of the building with respect to its rigid body motion point toward i the some trend. This is supported by an evaluation discussed in reference 4, where it was noted that the settlements occ tring during the time periods represented by lines e and d (reference 4, figure DGB-7), were those that are expected of a rigid body. In figure DGB-7, line c represents settlement during the surcharging period (1/79 - 8/79) and I!ne d represents estimated settlement during the post-surcharge period (9/79 - 12/2025). The point here is that the early cracking occurred when the building was only partially completed. Upon completion, the five sided (four walls and a roof) structure is now responding as a stiffer, essentially rigid body as would b, expected. 4 Hence during its construction _stoge, the building underwent substantial differential settlement that introduced in-plane curvature in the walls with l resulting stress and crocking compounded with normal shrinkoge cracking. As . l the building was completed and the concrete oged, its tended to behave more and } more as a rigid unit, the whole foundation (or building) moving as a plane (or a unit). The recent data indicates that for the last four years the building has generally settled as a rigid body introducing relatively little additional distortion In the structure. We expect this behavior to persist in time. j-E One may speculate art the mognitude of the absolute settlements over the service life; however, these are of lesser structural concern to the building,M - l~ j itself, and would only affect clearance to obstructions and connected items. L 6.16 TEi?A CORPORATION ~- 'n.
These latter eierwnts con occommodate some degree of distortion and con be t modified in the future if worronted. 1 \\ i I 6.3.3.3 Gross Stress Estimation i Even though we have noted that settlement data may not provide an acceptable basis for computing settlement effects, it is our opinion that if credit had been taken to account for: creep and stress relaxation in young concrete, reduced stiffness associated with the geometry of the uncompleted structure stiffness reduction due to cracking the exact recorded settlement could have been imposed on the structure without generating stresses in gross contradiction to that observed via crock patterns in i the DGB. This would have qualitative value to an overall understanding of building behavior. In order to improve our understanding of building behavior and to generally quellfy the influence of these effects, we modeled the north and south walls of the building using a simplified finite element model (reference 38). As a first order check of our partial model, we reproduced the 40 year imposed settlement analysis performed by Bechtel on the uncrocked structure. We obtained stresses l within 25 percent of Bechtel's which is reasonable considering the simplified model we used. l We imposed the recorded settlements on the incomplete wolf for Case lA and IB and on the complete wall for Case 28. For crocked concrete, the stresses were j computed as described in Section 6.3.2.2. ,i i 4 em l 1 6-17 TERA CORPORATION a
The following opproximate maximum values of stress were obtained: LOADING STEEL (ksi) CASE lA I l.3 i CASE IB 3.5 CASE 2A 4.6 This leads to a total stress of 19.4 ksi which is in good agreement with Dr. Sozen's independent analysis (see section 6.3.2.1 and reference 10). We recognize that the above onclysis represents a simplified approximation of e4 the very complicated effects of creep and crocking but it provides a qualitative i estimate of the state of stress of the building. We believe the results of our onalyses, properly interpreted are both useful and positive, specifically. e When modified for the effect of concrete creep and concrete cracking the foundation reactions when combined with reactions due to dead load, would not imply a physically impossible state of tension stress in the soll. ~ e When the rebor tension stresses are properly determined, that is on the bas's of strain in the uncrocked concrete rather than on the basis of stress In the uncrocked ,i
- concrete, they are quite modest rather than unrealistically lorge.
I \\ 6.3.4 IDCVP Assessment / Interpretation of Results in our opinion the settlement-induced internal forces implied by ti e associated rebor stresses, as they presently exist in the Midland DGB will not degr6de the N,_ I d capacities to resist the Internal forces and moments caused by the factored load .i \\ ~ ~ ) l J c', a 1 i ~ .k
N e TABLE OF CONTENTS 4 1. INTRODUCTION 1 2. DESCRIPTION OF THE DGB AND ITS PROBLEMS 2 3. SETTLEMENT AND CRACKING ISSUES 4 4. STRUCTURAL RE-ANALYSES 6 5. VIEWS ON THE ISSUES RAISED 10 6. ASSESSMENT OF THE DGB 17 7. CONCLUSIONS AND RECOMMENDATIONS 20 TABLE FIGURES APPENDIX I COMPOSITION OF TASK GROUP APPENDIX II
SUMMARY
OF MEETINGS APPENDIX III BNL REPORT APPENDIX IV LANOSMAN MEMO STATING DGB CONCERNS AT MIDLAND l i f ) l j 1
4 r 1. INTRODUCTION The Diesel Generator Building (DG8) at the Midland Nuclear Power Plant (NPP) is a reinforced concrete structure which has undergone excessive unequal settlement since its construction. The concrete walls of the DG8 have been i more extensively cracked than usually expected of such a concrete structure. OnthebasisofreviewandevaluationoftheApplicant's(ConsumerPowerCo.) various analytical studies, remedial measures taken, and the conunitments made and of the staff's own assessments, the original structural engineering staff t reviewer came to the conclusion that the DG8 was acceptable. However, an NRC l 1 regional inspector disagrees with the conclusion as to the acceptability of i the DG8 and has expressed his concerns in a hearing before a Congressional l Government Oversight Conuntttee. 2 Inthewakeofthiscontroversy,theDivisionofEngineering(DE)formedan independent Task Group to re-review the structural adequacy of the DG8. The l 1 j Task Group consists of three unbe~rs from the structural engineering staff 1 and a consultant team from Brookhaven National 1.aboratory. The consultant team provides expertise in both structural and geotechnical engineering. The l charter of the group and its composition, the names of the Staff, and its a l consultants involved are included in Appendix I to this report. The Charter of this Task Group has three elements.that are interwoven and do not lend themselves to neat separation. The Task Group was charged: i I l (1) to re-evaluate the structural design and construction adequacy of the DG8 as accepted by the structural engineering staff reviewer >4
2-(2) to assess the concerns as indicated by coments from other NRC personnel, and (3) to make recommendations to resolve any lingering concerns. It is acknowledged that the Task Group has had outstanding cooperation from the Applicant, the structural engineering staff reviewer and its consultants, the geotechnical engineering staff reviewer and its consultant, and NRC Region III Inspector, in either group's on-site inspection, interviews, or design audit in Applicant's A/E office. It is this cooperation that enables the Task Group to assemble all the necessary infonnation and facts in a short period of time. The chronology of the group's various activities and persons contacted are presented in Appendix II to this report. An independent report written by Brookhaven National Laboratory is included 1 in Appendix III of this report. ~ 2. DESCRIPTION OF THE DG8 AND ITS PROBLEMS i i The DGB is a two-story, box-type reinforced-concrete (RC) structure with three cross walls that divide the structure into four cells, each of which contains a diesel generator unit. The building is support'ed on continuous RC l footings 10' - 0" wide and 2' - 6" thick founded at plant eievation 628' and i resting on a fill that extends down to approximately elevation'603'. The building has exterior, wall thickness of 30", roof slab and interior wall thickness of 18". Plan dimensions'of DG8 are 155' x 70 wit'h a total 'l internal height of approximately 44'. Each diesel generator rests on a 6'-6" thick, RC pedestal that is not structurally connected to the building foun(ation. Figure 1 shows the general layout of the DG8. l ,w-y
o ' The DG8 as implied by its name is a building which houses the diesel generators and is classified as a seismic Category I structure. As such it is designed against the effects of extreme environmental conditions such as seismic-load and tornado wind load. The latter includes a wind pressure, a f differential pressure and tornado missile impact. The use of thick exterior walls and roof slab is basically a result of the consideration of the effects of the tornado missile impact load. 1 l When the building was approximately 601 complete, unusual settlement and j~ cracking of concrete walls were observed. The building was settling due to l the consolidation of the underlying fill while it was partially supported l along the north portion by.four electrical duct banks acting as vertical i piers resting on natural soil below the fill. A soil boring program to determine the quality of the backfill under the foundation discovered that l the fill was uncontrolled and improperly compacted. The fill consisted of 1 both cohesive soil, granular soil and lean concrete. The fill ranged from very soft to very stiff for cohesive soil and from very loose to dense for o j grinular soil. At the time of the soil exploration, the groundwater level was observed to be ranging from elev. 616' to 622' and the cooling pond, located about 275 feet south of the building, had a water level at l approximately elev. 622'. l In view of the condition of the DG8 as described above, it was apparent that i t corrective measures must be taken to relieve the DGB from its distress. The remedial actions taken by the Applicant can be summarized as follows: l I l i .I
4-2 (A) Separate the DGB from the duct banks - The duct banks entering the DGB were isolated from the building, thus relieving the building from the effects of the rigid supports. j (B) Surcharge the DGB and the surrounding area - The purpose of the surcharge was to accelerate the settlement and consolidate the fill material. so that future settlement under the operating loads would be i 'i ' within tolerable limits. s I i j (C) Install a permanent dewatering system - The purpose of the permanent 4 dewatering system is to maintain water level below elev. 610' in the area of DGB, thus minimizing the potential of liquefaction of the loose sands contained in the fill. The effects of the remedial measures taken can be observed from the amount of settlement which the DGB has gone through.as indicated in Figure 2 and also ~ from the crack sizes and crack patterns of the walls as shown in Figure 3. Details of both settlement and cracking issues are discussed in the following i l sections. l 2 1 l 3. SETTLEMENT'AND CRACKING ISSUES As a result of the remedial actions taken by the Applicant, it appears that the settlement.of the DG8 has'mostly stabilized.' However the fact still remains that the building has undergone unusual settlement and its walls have experienced extensive cracking. It has given rise to the concern of the DG8's j I
4 ' 5-structural capability to fulfill the function of protecting the safety-related equipment located therein as originally designed. In order to T alleviate this concern and to assure that the structural integrity.is preserved, the Applicant undertook a number of structural re-analyses using i the FSAR criteria and the ACI 349 criteria and taking the settlement and cracking into consideration. On the basis.of the results of the re-analyses, the Applicant concluded as follows: (a) The settlements during early stages of construction and during the surcharge did not cause any unusual distress or significant loss of. structural strength. As 'a result of surcharging, future settlement can be conservatively predicted and will not be excessive. The installation ] of the permanent dewatering system has eliminated any potential for liquefaction of the sand backfill below the DG8 during a seismic event. (b) Cracking of'the walls during construction and surcharging has not I impaired ~the ultimate strength'of the structure. 4 ) (c) The building will be re-evaluated for its structural adequacy when the allowable limit for the cracking width is exceeded under the established monitoring program, thus insuring its safety function. The. structural engineering staff reviewer and its consultants with findings of their own independent assesss9nts in essence concurred wi'th the Applicant's conclusions. However. the geotechnical engineering staff reviewer and its consultant together with the Region III inspector disagreed. I n l s i
h . A major point of contention was that the Applicant's analyses linearized the unequal settlements and thus the effect of unequal settlements has not properly been considered. The Region III inspector also contended that, because actual cracking of the concrete walls was not considered in the Applicant's analyses, the rebar stresses as calculated by the Applicant'were not representative of the stress for the loading combinations considered. In what follows the Task Group shall present its major observations of the l analyses performed by the Applicant and by the consultants to the structural engineering staff, the issues raised, and its assessment of the Applicant's conclusion on the DGB structural integrity. 4. STRUCTURAL RE-ANALYSES. In the preceding section, it is indicated that the Applicant has made a number of structural re-analyses and used the results of the re-analyses to ~ justify the DGB structural adequacy, and that there have been concerns expressed as to the appropriateness of the re-analyses. The essential elements of the applicant's re-analyses are succinctly sununarized. I Settlement Analyses Settlement of the DGB is time-dependent and load-de' pendent, but'a' complete and accurate settlement history does not exist. On the basis of the availability of the measured or estimated settlement values at various stages i of construction, four. cases of settlement analyses were performed by the f Applicant as listed in Table 1, with the corresponding settlement' values I t i l 4 l 'I
F ~ l o 7-shown in Figure 2. With the exception of Case 1A which was analyzed by long i I hand computation and by idealizing the partially completed DGB as a series of individual beams, the other three cases were analyzed by computer through the discretion of the DGB into a number of finite elements as exemplified in i Figure 4. Case 1A was accomplished by passing deflection curve through any three measured neighboring settlement points and selecting the one with the largsst curvature for moment camputation, and eventually, stress detemination. This calculation indicated that the measured displacements would result in a maximum rebar stress of 11 ksi. For the other three settlement cases, individual finite-element models were used. For settlement Case IB, the finite-element model represents the structure as built to el. 1' 662 f 0 in. For settlement Cases 2A and 28, the finite-element model represents a fully l completed structure. For Cases 18, 2A, and 28, springs were typically i calculated at each nodal point along the foundation by dividing the structural load represented at the' selected point by the measured or 1 i predicted settlement at that point. The finite-element analysis of each case I then involved several iterations in which the soil springs were varied until the deflected shape of the DG8, as calculated by the model, approximated the "best fit" settlements. The resulting deflections of the DG8 from these analyses as shown in Figures 5 ar.d 6 are not in conformance with the measured values and are almost linearly related. The magnitude of stresses would depend on the final cycle of iteration selected and would bear no 1 ' l i relationship to the actual stresses resulting from settlement. Other - l analyses perfomed by the Applicant consisted of (1) using zero and near zero i I soil springs to s t_.
r i ~ l simulate the soft soil condition, and (2) considering the DGB to be simply ( supported. The purpose of these analyses was to study if the,DGB has the ' capability of bridging voids and soft spots in the soil. e i j In an attempt to provide more insight into the problem the consultant t'o the { structural engineering staff was requested to make an independent analysis by using the measured settlew nt values at 12 locations as input. It was found i i that the DGB should have cracked extensively and yielded to failure. l However, the cracking condition.as exhibited by the DGB does not bear out the l conclusion of the aralysis. It was, therefore, concluded by the staff's 4 consultant that the DGB did not experience the settlement as ' measured and that the analysis did not reflect the actual settlement history of the DGB. Cracking Analysis Cracks in reinforced concrete (RC) members may be caused by the conditions of hardening or curing of the concrete (its shrinkage) or by excessive stresses in the materials (induced by too heavy loads, settlement of the footings and/or changes in temperature). Cracks due to excessive stresses appear most i frequent in the tension zones and are seldom encountered in the compression' l f zone of concrete members. Cracks in the RC walls of the DG8 are caused by a t i i combination of shrinkage, unequal, settlement and temperature changes. i Drying shrinkage and themal contraction cause shallow cracks at surface.As ~ I soon as the cracks are formed the tensile strain is relieved. In the case of i cracks due to unequal settlement the tensile strain is to be resisted by the reinforcing steel. The purpose of the cracking analysis is to determine the i rebar stresses from the measured crack width. First, the Applicant made an i } >v .,-n.- .w e v .n-, w-,,
- _ - - _ = i 9 analysis of a single through crack in a subsection of the east wall of the DGB by using the Automatic Dynamic Incresental Non-linear Analysis (ADINA) 1 computer program. The purpose of this analysis was to evaluate the ultimate capacity of a concrete section containing a single crack. As such, the results of the analysis are of only limited value in assessing the effects of i the cracks. As a further attempt to resolve the concerns on cracking, the i Applicant sought the opinion of Professor M. A. Sozen of the University of Illinois. On the basis of the crack patterns and crack-size, Prof. Sozen i estimated the stresses in the rebar across the cracks to be in the range of 20 to 30 ksi. l The structural engineering staff reviewer also made his own assessment by combining the rebar stresses estimated from crack widths with stresses resulting from the Applicant's analyses for other operating loads. It showed thattheresultantstresswaswithintheacceptancecriteria(Tr.11086). i 4 t in order to assure the structural fntegrity of the DG8, the Applicant has t proposed a crack monitoring and evaluation program to be used during the life of the DG8, in addition to an initial repair program. Specific acceptarce j criteria (i.e. alert limits and action limits) for crack width and crack 4 width increases have been specified by the structural engineering staff reviewer and agreed to by the Applicant. t
10 I 5. VIEWS ON THE ISSUES RAISED-i The four concerns as raised by Region III inspector, Dr. R. B. Landsman, are directly quoted from his memorandum to R. F. Warnick, Director, Chief of Special Cases of NRC Region III, dated July 19, 1983, as follows. I. Concern: "My first concern deals with the finite element analysis that Consumers Power Company (CPCo) used to show that the building is structurally sound. Their model of the building assumed a very rigid structure without any cracks._ The building has numerous cracks, reducing the rigidity of the structure. The effects of these cracks have not been I taken into account in the analysis. CPCo's interpretation of the settlement data as a straight line approximation always stems from their position that the building is too rigid to deform as indicated by actual settlement readings. The settlement of the building occurred over a period of time during different phases of construction. It is this time dependent effect that was also not used in their model. Even CPCo expert Dr. Corely testified at the ASLB hearings that the analysis should have "taken into account cracking and time dependent effects" in order to give correct results. Finally, the staff's official position, as stated by Dr. Schauer, on CPCo's analysis was, "The staff takes no position with regard to that analysis." Connent: The first part of this concern'is that the cracks have not been considered in the Applicarit's analyses. As' indicated in previous discussion, cracks in the walls.of the DG8 are due to a combination of shrinkage, unequal settlement and temperature changes. Ordinary' drying i shrinkage and temperature change cracks are generally surface cracks. As soon as the cracks are formed, the tensile strain is relieved, f Cracks due to differential settlement are generally through cracks I across the wall thickness and, therefore, reduce the, stiffness of the I structural members. Structural engineers involved in reinforced I concrete design are well aware of this fact. In order to take cracking l 4 1
11 - of structural members into consideration, structural engineers first assume these members are uncracked and perform the structural analyses to obtain the mimients, shears and axial forces required for the design .of member sections. In designing the members concrete is then assumed to be cracked and does not take tension. Such a procedure of analysis and design is a standard practice anc' is, in fact, reconsnended by the ACI 318-77 code. The second part of this concern is that the actually measured i settlements have not been used in the Applicant's analyses. From the settlement data avail'able it is obvious that settlement was ~ continuing with the progress of construction with the maximum attained after the removal of the duct bank restraints and at the end of surcharging. In the early stages of construction the components such as l, the continuous strip footings, and wall portions forming the lower part i of the DGB were most likely very flexit,le, ar.d deflected in conformance 4 with the, settlement without creating any excessive stresses in the as-built portion of..the D'GB.- inere might be cracks in some of the components of this portion of the DGB due to shfinkage'and/or displacement of the green. con' crete as 'a result of settlement. In order d I to adequately'cor. sider effects 'of settlement over the period of time l duringdiffe' rent'phNsesbfconstruction,theanalyticaltmdelswould y have to beidifferert'for different phases of construction and to be meaningful',theri shoul_d be settidssnt:r.casurements' corresponding to each N N- -t s s j v l 3 v a. c y '^; O C^" N. ' d.
1 , phase. However, there are no such detailed settlement measurements available, especially for the early stages of construction. The settlement measurements which are available correspond to those in j the later stages of DG8 construction, that is, when the as-built portions of the DGB are relatively rigid. The Applicant perfonned three separate finite element analyses for which measured and/or predicted settlement values are available. The measured and/or predicted settlement values are used as data points in linearizing the settlement. l The differences between the measured / predicted settlement values and the resulting linearized values have been discounted as survey inaccuracies. t This is basically equivalent to assuming that the north and south walls i underwent rigid body motions. The computed stresses from this model are due to racking only. The stresses obtained in th'e process of 'linearizing the settlements, therefore, do not represent the actual l settlement stresses. i The use of survey inaccuracies to discount the differences between the measured / predicted settlements and the linearized values is not convincing in view of the fact that all the settlements have not occurred after the completion of the'DG8 construction. The third'part of.this concern is. that the time dependent effect has not been considered in the Applicant's analyses. The Applicant has considered the four stages of-construction, therefore the time factor has been taken into consideration but in a very gross manner. As indicated in the preceding connent in order to assess accurately the 3 4
- i. P.,
2 3
i stresses in the walls of the DGB, detailed information on wall cracks (time-dependent) and on settlement values (also time-dependent) would be required for each step in the construction. There is no detailed information on either the cracks or the settlement values to cover the whole time span of construction. Basically this portion of the concern is inherent in the above two portions of the concern. The fourth portion of the concern is that the structural engineering staff reviewer has taken no position with respect to the Applicant's analysis. From the preceding.conenents it is obvious that the adequacy of the Applicant's settlement analysis is questionable and it cannot be relied on to reach any conclusion. The structural engineering staff reviewer took a prr.ctical approach by ignoring the analysis, and resorted to the solution through crack analysis. II. Concern: "My second concern deals ~with ihe acceptance of the diesel generator j building in the SSER #2 which was sub, ject to the results of an analysis to be performed by the NRC consultants using the actual settlement values. The consultants testified at the ASLB hearing that this analysis gave unacceptable results and this portion of the SSER sho'uld be stricken. They are basing their unacceptable results and comments on their finding of very high stresses obtained in areas where no cracks exist. Therefore, the actual settlement values are not accurate enough (are in error) to be used in an analysis. The consultants, as well as CPCo, ran a linear analysis (structure always in the elastic range) l instead of a plastic analysis which would allow a redistribution of loads in the structure. Therefore, supposed areas of high stress, where cracks are not located, may not exist due to redistribution of loads. Finally, the staff's official position, as statea by Mr. Rinaldi, on this analysis as perfomed by the consultants, was that the actual settlement values could not be relied upon to determine if the diesel generator building meets regulatery requirements." 5 iww-e-< 4-- o-qs e-w g g. h g I
l 14 - Coment: The first portion of concern i.s that the structural engineering staff 4 reviewer disregarded the results of an analysis done by its consultants on the basis of the actual settlement values. This portion of the ) concern is in essence the same as the first concern. It is indicated in the coment on the first concern that the settlement was continuing with the progress of construction. When the strip footing concrete was l placed, settlement started. Since the footing is a comparatively thin i slab, it would likely deform with the settlement without creating l l excessive stresses. With the build-up of the walls, settlement increr.ses and rigidity also increases. When the intennediate floor slab i and the roof slab were completed, the complete structure became a very f rigid structure and any settlement should be nearly linear unless there j were weak sections across the building. To analyze the completed DGB on the basis of the settlement values which were accumulated during the construction and after its completion would result in exceedingly high i I stresses which are not representative of the actual values. The second portion of this concern is that the staff has not used plastic analysis. It is suggested, that in order to conform to the meas 0 red settlement value's a. plast'ic analysis should be made to allow redistribution of loNs in the structure. This observation is valid providing that rebar in the walls and slabs of the DGB have undergone a s yielding and plastic hinges have formed. It is the judgment of this Task .'3 i o) L:J ' q ~ a .-+. r _ _, E. ,h,._'
is ' Group that, without the knowledge of accurate geometry of the DGB at the various phases of settlement, a non-linear model accounting for plastic effects would not be meaningful. 1 i The third portion of this concern is the staff's official position that the results of the analysis by the staff's consultants on the basis of actual settlement measurements cannot be relied upon to detemine if the i DGB meets regulatory requirements. From the areceding comments, one cannot accurately calculate the stresses in the completed DGB without settlement data from the initial phase of construction. Given the l unavailability of the data necessary to complete the input to the i analysis by the staff's consultant, the prev _fousiv stated staff position is reasonable. s III. Concern: 1' "My third concern deals with the fact that we are not following normal 4 engineering practice in accepting the building by using a crack analysis approacn because there is no prat:tical method available today to analyze a complex structure with cracks in it. The. basis of this concern is that there are no fomulas available that can estimate stresses in a complex stress field like those which exist' in this building. Thus, the evaluation of the structure based on the staff's crack analysis using j empirical unproven fomulas to determine the rebar s~ tresses is .j unacceptable." Comnent: This concern is related to the use of' crack analysis to accept the DGB.' ~ Contrary.to the concern expressed there are computational-tools ] available to relate crack width to rebar stresses, but in effecting the a .1 analyses one still has to make some major simplifying assumptions which I i i i I- + ). V d y ~
16 - requires the judgment of the analyst. The results of such analyses in most likelihood will not be exactly the same as what actually exists. In the case of DGB the estimation of rebar stresses from the sizes of cracks is admittedly an approximation. However, it is the judgment of the Task Group that this is the only practical approach available to evaluate the DGB rebar stresses. A 1 In evaluating the rebar stresses estimated from crack widths the following, as a minimum, needs to be considered and docsmented by the Applicant: whether or not the cracks are through the wall thickness; the sizes and locations of the cracks; whether or not the cracks are 1 growing in width and/or length; whether or not the number of cracks are increasing; and whether the estimated rebar stresses due to settlement are -less'than the allowable values after accounting for load ) combinations is made. 4 1, 1 IV. Concern: 1 "My fourth concern deals with the staff accepting the building by 4 relying on a crack monitoring program to evaluate the stresses during I the service life of the building. If cracks exceed certain levels, recommendations will be made for maintaining the structural integrity of the building. The basis for my concern deals with the lack of crack l size criteria and the lack of foriiulated corrective action to be taken when the allowed crack sizes are exceeded." -fj 1 Comnent: This. concern questions the staff's acceptance of the DGB on the basis of a crack monitoring program which is not well defined'in. crack size criteria and in corrective action. The DGB is designed for combinations 1 9 t ,.w _am A
17 of dead, live, tornado and earthquake loads, and therefore it is expected to be able to resist these loads and their loading combinations with adequate margins of safety as designed. However, as a result of_ settlement which was not considered in the original design, the margins __ ,of safety have been reduced to some extent and there is some uncertainty as to its capability to resist the design loads. The purpose of monitoring the cracks is to insure that if there is any change in the condition of the structure it will be observed and appropriate actions can be taken, if necessary. The structural engineering staff reviewer ~ has specified and the Applicant has agreed to tfie crack size criteria f and the corrective action to be taken when the allowed sizes are 4 exceeded. The Task Group is of the opinion that, while the approach is. reasonable, details of the program should be further examined and improved. It should also be noted'that the crack monitoring program should be-in complement with a settlement monitoring program, since any assessment based on either of the' two monitoring programs alone may be misleading.
- 6. AN ASSESSMENT OF THE DGB Before assessing the structural adequacy of the DGB, let us examine i
- ] general characteristics of structures in their capability to adapt to 1 the settlement of the foundation soil. Structures may be classified as i highly flexible' practically flexible, highly rigid and practically 5 i 't f. ~ i l
9 t ' rigid on the basis of their defomability with respect to the settlement of the foundation soil. I j Highly flexible structures follow the displacement of the foundation soil surface at all points. An' example of such a structure is an earth f embankment. Non-uniform (differential) settlements do not give rise to any complications in the deformation of such a structure. Highly rigid structures either have a uniform settlement when subjected to a symetrical load with symetrical distribution of the soil compliance, or else tilt without bending. As an example of this are grain elevators, factory chimneys (smoke stacks), blast furnaces, etc. 4 These structures level out the settlements, i.e., they perfom in conjunction with the soil bearing material..It is because of re-distribution of the pressure by the structure that differential settlement effect of the supporting material diminishes. Practically rigid structures, which include most buildings and many engineering structures (multispan trestles and bridges with continuous structural members, reservoirs,. storage tanks, etc.), cannot closely follow the foundation soil defomations at all points and, because of differential settlement, are subject to bending. Such structures level l out only in part.the non-unifom settlements of the foundation soil surface. This results in the development of additional forces in the supporting members of the structures, which are us'ually disregarded in j 1 i .j i x 2. -._ u H. .a 5
- the course of their designing. Hence the possible development of cracks in such members.
Practically flexible structures largely follow the displacements of the soil surface, i.e., they bend (such as low single-story buildings), but over short sections they are capable of levelling out to a certain extent the differential settlement. This results in the emergence of usually insignificant additional forces in~ the supporting members. In t the event of highly non-uniform settlements th'ese force's can cause the i development of cracks and fractures. On the basis of above classification and because of the box-type construction with heavy reinforced concrete walls and slabs, the completed DGB can be considered as a highly rigid structure. However, in the process of construction, the as-built portions of the DGB at different stages of construction can be considered to vary from highly flexible, practically flexible. practically rigid to highly rigid. It is believed that most of'the tettlement and' settlement cracks appeared ' at the v'arious stages of construc' tion. However, the cracks have not 'cen carefully studied and mapped at each stage of construction so that o j a reasonable correlation of the cracks with all the causes can be t' established. Only the cracks which were mapped in January 1980 have been identified as shrinkage and/or settlement cracks. Most of the 'I cracks which have been identified to be due to unequal settlement are the cracks in the cross-walls,.the movement of which was restrained by the duct banks. l j l -~...#
i 20 - The DGB design,~as indicated by pplicant's analyses, is. controlled by the tornado wind. Under such a load, especially the postulated internal pressure, the full streng~th of the walls will be mobilized, and there will be a redistribution of the load, if there exist localized high i stress areas. This will also be true if the seismic loads are considered. One can make such judgments on the basis of the observation that the DGB is a highly redundant structure. The structural elements i. are not columns and beams. They are heavy reinforced concrete walls and slabs. With necessary repair work to be done and with adequate 5 _monitorina nranrams, there is reasonable assurance that the structural 2 integrity of the DGB will be maintained and its functional requiremnt will be fulfilled. ___ 7. CONCLUSIONS AND RECOMENDATION l Most of our conclusions have been expressed in our comments to the I concerns,'5ey may be sununarized as follows: I j 1.. . Analyses of the DGB either by linearizing the settlements or by i i applying the settlements as measured render unrealistic results. f The stresses due to settlement are either underestimated or 1 overestimated. A realist'ic analysis would be one which simulates ') l the stage-by-stage construction of the DG8, and uses the actual and more detailed' settlement measurements at each stage. However, such settlement history for the DGB does not exist.1 For this recson, l-the Task Group' believes that a rigorous' analysis to compute rebar f i stresses.is unattainable. l ~ .1] q ~ + L: 9 z.
2. The estimation of rebar stresses from the crack width is admittedly a approximation. The estimated stresses of 20 to 30 ksi appear to Howevertobeconvincing[adetailedprocedureoff be reasonable. ,~ -crack analysis should.be documented and provided. ~ Inconsistences in the documentation of the settlement history needs [, 4 3. / N to be resolved.T/ For example, the Midland Units 1 and 2 Executive Sun. mary dated August,1983 states that for the July 1978 period, the maximum settlements recorded were 3.5 inches while Figure ES-14 of the same document indicates a maximum of 1.99 inches for the same period. 4. The current monitoring program is inadequate to deduce future distress. Thus, an adequate monitoring program for both settlemen g fandcracksshouldbedevelopedandimplementedtoassurethatthe structural integrity of the DGB should be maintaine'd during the i life of the plant. i i 5. On the basis of the overall evaluation, it is nevertheless felt that the DGB in its current state can fulfill its functional _ requirement _. I 6. It is recoamended that a repair program be developed and sN implemented. t g
~ TABLE 1 e DIESEL GENERATOR BUILDING SETTLEENT CASES CASE TIME PERIOD ~ PERIOD PORTION OF BLDG COMPLETE lA 3/78 - 8/78 PRE-SURCHARGE WALLS TO ELEY 654' ~ 18 8/78 - 1/79 PRE-SURCHAR6E WALLS TO ELEY 662 (BELOW MEZZANINE SLAB) 2A 1/79 - 8/79 SURCHARGE COMPLETE BUILDING 28 9/79 - 12/2025 40 YEAR COMPLETE BUILDING J
rYR PEDE.SYAl. .SEE F/G B -2 N c Q 8AY / 84Y'2 8AY3 bay 4 ..m% / ag!so* TYR t y w u u 6 PL A N i 1 C t i i i 9 ~ SECTION ~ LO CKluG UCa rd l t i ~0 9 4 7 3 N 4 i 4 m N 'i. = l f-7
- r7 MIDLAND PLANT UNITS 1 & 2 CCNSUMERS FOWER CCMPANY FIGURE.1
- SECTION DIIsu. cE5ERATOR BL::C LQQMJAIG WEST tta s szcT10:ts M PE DATE. 4424/73 9 1 .a +- ,p ,m- ,gw-<e m l
- 2..
0.90 0.85 0.76 LINE A 1.19 1.02 LINE B 0.77 1.09 1.G4 1.98 2.41 LINE C 1.50 1.51 1.78 1.86 1.91 LINE D 1.33 1.15 1.19 1.18 1.29 TOTAL 4.79 4.77 5.41 5.87 6.37 0 0.. "H O 59 80 o w .... y.y3., . w. u.m w., w r...- c,3 .i m c. s b a a j 1 3 3 3 1 NORTH , d . f . ? f j g t t t t BAY I BAY 2 BAY 3 BAY 4 H 5 i i i i -...e itcirs.:..za. .x Am mw: w. re. 4g.:.s w.w.w..-.4.; g O O O O O LINE A 1.67 1.42 1.28 1.44 1.99 LINE'8 1.14 1.12 1.46 1.92 2.21 LINE C 3.00 2.92 3.16 3.37 3.24 -LINE D 1.62 1.67 1.69 1.98 1.89 TOTAL 7.43 7.13 7.59 8.71 9.33 LEGEND O DIESEL GENERATOR DIESEL GENERATOR BUILDING BUILDING SETTLEENT MARKER FIGURE 2 EXECUTIVE
SUMMARY
SETTLEENT IN INCHES FOR
SUMMARY
OF ACTUAL AND PRE-SURCHARGE PERICO (3/78-8/78)............LINE A ESTIMATED SETTLEMENTS PRE-SURCHARGE PERIOD (8/78-1/79)............LINE B SURCHARGE PERIOD (1/79-8/79) ...............LINE C POST SURCHARGE PERIOO (9/79-12/2025)........LINE D FIGURE ES-14 ASSUMING SURCHARGE REMAINS IN PLACE b-
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- t. fot ctAct Marstato,oFWatt s feoM f t.4 6 4 'o
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- \\
\\ N J h / h / s J/ N N \\ \\ r sesu V NORTH s \\ N / lll \\ / I N f g DIESEL GENERATOR BUILDING typtcol vertIcol EXECUTIVE
SUMMARY
tranalatIonct spring FINITE-ELEMENT NODEL (for ease of presentation. FIGURE 4 on1Y vertical translational springs have been depicted) FIGURE ES-13
REFERENCE SLEFACE i / ~ / 1DD 1.09 D.TT ~ 1.54 I I. I41 .97 1 l.98. --..... BAY I BAY 2 BAY 3 8AY 4 2.41 EASURED SETTLEENTS I i t.12 i b I 't.46 k 1.14 ~.- g I 1.27 I -ERROR CONSISTS t 1. 56 1 0F
- DUE TO I 1. 56 I I 2.17 I CALCLLATED LIMITS OF SURVEY
"'T?... ACCURACY SETTLEENTS l.92 2.21 DIESEL GENERATOR BUILDING EXECUTIVE
SUMMARY
COMPARISON OF SETTLEMENT VALUES FIGURE 5 PRE-SURCHARGE PERIOD .tUGUST 1978 - JANUARY 1979 1 FIGURE ES-15
s / NORTH I 1.481 g.St '. '. '. '. '..........g..... K.... ' ^9f.[*%$$fA - ,,5.'5h-'!.,k;.;.{.,' l l.[,(,; j;'f-; t.50 I I 83I I I.60I ~ ' ' '^:Ed MO"7:R t-7.:. 1.91 1.78 3.86 BAY t BAY 2 BAY 3 BAY 4 I ..4 i -ERROR '8AND CONSISTS OFs 2.92 I 3 Isl
- 1.
- V8" CUE TO EM
- f. f...,*:
7 2 5 s s ? AW M 3,_ ,..... w yM SURVEY 1 3.24I 3.24
- * * ' '"77.EO..*:?.i-6;-i+y,A.r
...:.'.'.Yd..
- 2. AVERAGE SYSTE-C I3.05 1
3.I6 "" **" ~* EASURED MATIC ERROR OF N 37 0.t0 INCH CARRIED 3* CALCLA.ATED SETTLEENTS SETTLEENTS IN THE SURVEY OATA FOR THE PERIOD 3-20-79 TO 9-6-79 DIESEL GENERATOR BUILDING EXECUTIVE
SUMMARY
COMPARISON OF SETTLEMENT VALUES FIGURE 6 SURCHARGE PERIOD JANUARY 1979 - AUGUST 1979 1 FIGURE ES-16
4.-- REFERENCE SURFACE j NORTH o.45
- 0.40
,o,43
- 0.39
/ . 0.51 / .. S 3 ,- /4*-Mi..-5:*f 3 f.: /.:::.. ; L.. .. : f. : :.. :......;.;.,3. g,3...,..(,,y, pyy. :......7 :. - .-s.- /.33
- BAY !
8AY 2 BAY 3 BAY 4 / O.42 :, M / ~ ' 0.47 '0.47 '0.49 0.43 EASURED / PREDICTED ERROR BAND /SETTLEENTS CONSISTS OF: 1.6T . 69 1.62, K4.. :.-:.-::...:...- ~ - - TO LIMITS OF 10.20 INCH DUE ' ~C - % M +.'.~....... .......-y 1.89
- h ei PREDICTION I1.T1 A ACCURACY NC CULATED 3.93 E
SETTLEENTS . ACTUAL EASURED SETTLEENT FROM SEPT.14,1979 TO DEC.31,1988. THESE INCLUDE EFFECT OF DEWATERING TO' APPROXIMATELY EL. 595', .AND REPRESENT WOVEENT OF THE STRUCTURE DUE TO SETTLEENT OF THE FILL AND NATURAL SOIL BELOW. ~ ACTUAL EASURED SETTLEENTS FROM SEPT.14,1979 TO DEC.31,1981 PLUS ESTIMATED SECONDARY COWRESSION SETTLEENT FROM DEC.38,1988 TO DEC.38, 2025 ASSUMING SURCHARGE REMAINS IN PLACE. DIESEL GENERATOR BUILDING EXECUTIVE CUMMARY FIGURE 7 COMPARISON OF SETTLEMENT VALUES POST-SURCHARGE PERIOD SEPTEMBER 1979 - DECEMBER 2025 FIGURE ES-17
APPENDIX I COMPOSITION OF TASK GROUP NRC Staff: Task Group Leader Dr. Pao-Tsin Kuo, Section Leader Structural Engineering Section B Structural and Geotechnical Engineering Branch Dr. Chen P. Tan, Structural Engineer Structeral Engineering Section 8 Structural and Geotechnical Engineering Branch Mr. horman D. Romney, Structural Engineer Structural Engineering Section B Structural and Geotechnical Engineering Branch NRC Consultants: Dr. A. J. Philippacopoulos, Associate Scientist Structural Analysis Division Brookhaven National Laboratory (BNL) Dr. Charles A. Miller, Senior Consultant Structural Analysis Division Brookhaven National Laboratory Dr. Carl J. Costantino,' Senior Consultant Structural Analysis Division Brookhaven National Laboratory t f V 1 t i e e
8 g UNITED STATES
- 8 NUCLEAR REGULATORY COMMISSION o
{ I j WASHINGTON. D. C. 20555 AUG 8.1983 i MEMORANDUM FOR: C. P. Tan Norman Romney Structural Engineering Section B Structural and Geotechnical Engineering Branch, DE e THRU: George Lear, Chief g; Structural and Geotechnical Engineering Branch, DE 6' FROM: P. T. Kuo, Structural Engineering Section 8 Leader i Structural and Geotechnical Engineering Branch, DE
SUBJECT:
EVALUATION OF LANDSMAN'S CONCERNS REGARDING DIESEL GENERATOR BUILDING AT MIDLAND
Reference:
Memorandum from R..H. Vollmer to D. G. Eisenhut, dated July 21, 1983 Per the enclosed memo from R. H. Vollmer to D. Eisenhut, a task group to re-evaluate the structural design and construction adequacy of the i Midland Diesel Generator Building has been formed and I have been designated as the leader of the group. You are assigned as members of this group. The mission of the group is described in the enclosure. A . T. Kuo tructural Engineering Section B Leader Structural and Geotechnical { Engineering Branch, DE j
Enclosure:
As stated i cc: w/o enclosure R. H. Vollmer J. P. Knight [- d G. Lear ,, a .t \\ G t V 'l I O .1 .. [ f ~
,4 a( ' ENCLOSURE f,,, %,. UNITED STATcs 3 NUCLEAR REGULATORY COMMISSION g-WASHI:4GTON, i3. C. 20G55 Q R I ~ 4lL 21 1503 .MEMORANDuft FOR: Darrell G. Eisenhut, Director Division of Licensing' ~ FROM: Richard H. Vollmer, Director Division of Engineering
SUBJECT:
$VA(OATION OF LANiiSMAN'S CONCERNS REGARDING DIESEL GENERATOR BUILDING AT MIDLAND l i Responding to your memorandum, subject as above dated June 27, 1983, J. . Knight, Assistant Director for Components & Structures. Engineering, has formed a task group to re-evaluate the structural design and construction adequacy of the Midland Diesel Generator W ilding. The group, headed by Dr. P. T. Kuo, will review the design review documents and the construction reports; physically inspect the building; search out and interview concerned individuals, including Mr. Landstren; and i prepare a final report on the adequacy of the Midland NPP Diesel Generator Butiding. The particulars of the groups' composition and charter are developed in more detail in the attached document. Note ~ that we intend to ucc a consultant ~1n a capacity to critique our findings on tir. Landsban's concerr.s. The consultant's views will be provided i.n our report. Mc4Llw 2* Richard H. Vollmer Director y Division of Engineering } cc: H. Denton ~ ~ 1 J. Knightf ~ t J. Keppler + T. Novak s E. Adensam' l G. Lear j P. Kuo F. Rinaldi - o s I D. Rood a p 5 lC 'y f 'l ,\\ ay ' Q '., c-, n 'V j\\ ^ ~q c. J, I f dq ; :[g -[ ~ [D b.2p$ - a { *. ' f e +. .,3 , s 3 t
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IMPLEMENTATION CONCEPT REVIEW OF THE HIDLAND NPP DIESEL GENERATOR BUILDING 1. HISSION A review will be conducted as to the structural adequacy of the w' Midland NPP diesel generator building. All information available g from NRC regional inspectors in this matter will be obtained and i the impact of that information will be fully considered in the j review. s 2. BACKGROUND The NRC structural engineering staff (headquarters) has reviewed the Midlend NPP diesel generator building's engineering design and construction and has indicated that the building is structurally ' adequate to resist its design loads. However, during hearings \\ before,a NRC Congressional Oversite Committee, the structural adequacy of the Midland NPP diesel generator building was questioned by an NRC employee, Mr. Ross Landsman, a Region III site inspector for the Midland project. It is considered prudent that a . review be undertaken by a technical group to assure that Mr. i Landsman'r, concerns are fully heard and carefully evaluated so that ,the adequacy of the diesel generator building may be further assured.
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3. ORG.aNIZATION The review group is composed'of four technical members - ,4' e t .W g _9 p g a
v e -a_ a group leader, two team members from the structural review staff 1 and a struct2ral consultant. The consultant will be asked to i provide his critique of Landsman's concerns and our findings directly into the final report. tj. 4. SUPPORT The NRC structural review staff will provide the background technical studies, reports, and other review materials that formed' the basis for their review and technical conclusions.. The NRC project staff for the Midland NPP will provide general administrative arrangements to facilitate the review. Region III will provide a complete listing 'of Mr. Landsman's concerns. C SCOPE OF EFFORT The efforts of the review group may include but will not be limited 4 to 1) review of all pertinent technical materials, 2) on-site inspection of the diesel generator b ildin'g,3)on-siteinterviews u with all inspection personne.1 that have information to contribute 1 and 4) preparation of a technical report summarizing their activities, considerations and findings. 'The report will include, t i as a separate attachment, the opinion of the consultant group m, ember. ~! 3 -m. ' ' ~ y As ES = 3,, I-
3-6. TIMING Review activities should be completed ilLT 30 working days after receipt of a written statement of Mr. Landsman's concerns and the final report will be due to the Director, DE NLT 15 working days after completion of the review. tj 7. DESIRED PRODUCT The desired final report of the review is a report that discusses .ea,ch of Mr Landsman's concerns, as well as any other concerns that might be offered during the review, and prov.ide a basis for acceptance or. rejection of each concern. A technical review of the adequacy of the diesel generator building should then be presented that is reflective of the groups' final recommendations in this matter in l'ight of new information furnished by Mr. Landsman and others. I assup 9 4 x i q-t e i t e { ) ,o '^ -l x 'p"' y W
i APPENDIX 11 i SU M ARY OF MEETINGS i August Meeting with Applicant and Site Visit j On August 24, 1983 members of the Task Group met with Bechtel and f Consumers Power Co. staff in the Bechtel, Ann Arbor, Michigan offices. At this meeting, presentations were made by.the applicant and their consultants to provide background on the history of the DGB construction original design philosophy and the analyses done to demonstrate the adequacy of the structure following settlement. On the evening of August 24 and during the morning of August 25, 1983 the members of the Task Group visited the Midland site to observe the l DG8. The Task Group members observed the cracks in the DG8 and held discussions with construction personnel to determine the sequence of concrete placement during construction of the DG8. At the site crack i i I maps of the DGB were provided by the Applicant. Task Group Interviews With Original Reviewers 9 On September 8,1983 the Task Group met individually with the original NRC staff reviewers responsible for the Geotechnical and Structural j Engineering evaluation of the Midland DGB. The persons interviewed l were: Dr. Harry Singh of the U.S. Amy Corps of Engineers, Chicago a i A II - 1 i .p ] Jp' 4
l (geotechnical engineering consultant); Mr. Joseph Kane of the ] Geotechnical Engineering Section, SGEB; Dr. Lyman Heller, Geotechnical j Engineering Section Leader, SGEB; Mr. Frank Rinaldi, Structural l Engineering Section B SGEB, Mr. John Matra, Naval Surface Weapons Center, (structural engineering consultant); and Dr. Gunnar Harstead, Harstead Associates (structural engineering consultant. The purpose of the interviews was to gain an understanding.and/or clarification of the concerns each reviewer had regarding the Midland DGB. Dr. Harry Singh was retained by the Geotechnical Engineering Section after discovery of the soils problems existing at the Midland site. i Dr. Singh was concerned that the structural analysis of the DGB did not take into account the settlement data as measured. Dr. Singh was 4 concerned with the appropriateness of using crack widths to evaluate i rebar stress due to settlement; although he did recomend that the cracks should be monitored as a measure of the DGB's structural adequacy. Generally, Dr. Singh expressed his opinion that the cracks in the DG8 were much more extensive than one sees in normal concrete work. Dr. Singh is of the opinion that the DG8 is in secondary settlement and that future long term settlement would be about 1-1/4 inches over 30-40 i years. \\ I The primary concern of Mr. Joseph Kane involved the Applicant's assumption of a straight line, rigid body motion in the structural evaluation of the effects of settlement on the DGB. Mr. Kane was of the A' i opinion that the settlement values measured by the applicant are 3 A II - 2 i a j j ~n 's
I appropriate to use in the structural analysis because the building did i settle as the soil conditions would have indicated (i.e., nonuniform). Furthermore, Mr. Kane was not concerned about the accuracy of the settlement data because they are the best data available from the Applicant and were more appropriate to use than to assume straight line settlement. With regard to the structural analyses using actual I settlement data, Mr. Kane observed 70-80% of the cracks to be in areas i j where the analyses indicated areas of high stress. Mr. Kane has f documented his concerns in memos dated August 2,1983 and are included in Attachments 1 and 2. i Dr. Lyman Heller met with the Task Group to express his concurrence with l the concerns expressed by Mr. Kane. Dr. Heller also offered an i explanation as to why cracks were observed in areas where the analyses of the DGB indicated low stresses. The explanation offered was that the i ~ settlement of the concrete fonns (1 e., yielding) during the pour ~ created discontinuities in the finished concrete which served as preferred paths for the development of cracks. Dr. Gunnar Harstead, Mr. John Matra and Mr. Frank Rinald.1 were I interviewed together. Mr. Rinaldi, Mr. Matra and Dr. Harstead ..l. maintained that use.of the measured settlements would be inappropriate 3 given the accuracy between survey measurements of +.or 1/8". Such. 1 inaccuracies in the survey data would result in unrealistic concrete stresses. Mr. Matra discussed the finite. element models he prepared and 'f executed for.Various stages of construction using the settlement measurements n inputs. B gj A II - 3 ,d us a s,.
f He indicated that there was not sufficient settlement data points to make a reasonable stress analysis. To obtain the required input, Mr. Matra stated that he linearly interpolated between the measured settlement data points. As expected there was extremely high stress in areas where no cracks in concrete were observed. Both Dr. Harstead and Mr. Matra mentioned that stresses depended on higher order derivatives. These higher order derivatives cannot be determ.ined accurately from the five measured data points. Mr. Rinaldi indicated the most appropriate method of estimating rebar stresses due to settlement was to estimate stresses from crack widths. This method produced rebar stresses of 1 about 5 ksi which when added to the stresses from the controlling load f cases was less than the 54 ksi allowable. Mr. Rinaldi described the i crack monitoring program the Applicant aqreed to (0.05 /10' as alert I limit and 0.06" or 0.020"/10' asactionlimit). Finally, Mr. Rinaldi and Mr. Matra indicated that the controlling load case for the DGB was tornado depressurization which assumed the DGB to be unvented which is l conservative considering the building is vented., Mr. Rinaldi documented his response to Landsman's concerns in a memo in Attachment 3. t ? Task Group Audit of Design Calculation t-The Task Group visited the Bechtel, Ann Arbor, Michigan offices on September 12 and 13, 1983. The purpose of t'he visit was to conduct an l audit of the stiuctural design calculations of the Midland DGB. A II - 4 4 h Ld 4 g e w w s v
~ 1 On Monday, September 12, 1983 the NRC Task Group reviewed the following DG8 calculations: - concrete /rebar stresses using settlement data by Karl Wiedner; - straight line (rigid' body) settlement by Karl Wiedner; - concrete /rebar stresses assuming the DGB is supported at four points; I - stress totals from all load combinations; - finite element modal for DGB. On Tuesday, September 13, 1983, the NRC Task Group discussed with Dr. Mete Sozen the calculations he did on rebar stres:;as estimated from l concrete crack widths. Dr. Sozen had made calculations estimating rebar stresses from crack widths for the center cross wall only. A call was made to Mr. Rinaldi in Bethesda to verify how he made his calculations on the other walls. Mr. Rinaldi indicated he did the same type of i analysis using Dr. Sozen's approach for other walls. However, Mr. I Rinaldi did not document the details of his analysis. I A II - 5 } .e f g ,.w.g
Landsman Interview The Task Group interviewed Dr. Landsman on September 13, 1983 for about 3 hours. Dr. Landsman aiscussed each of his concerns at length. During the intervi discussed ;,ew, potential resolution of the problem of the DGB cracks was uk. Landsman agreed that stresses determined from analysis ] 3 or crack widths would be acceptable. provided that: (1) these calculations were sufficiently documented; and
- S-(2) an acceptable crack monitoring program was specified and
(_ implemented. A copy of Dr. Landsman's memo of July 19, 1983 documenting his concerns en the Midland Diesel Generator Building is included as Appendix IV. i ~ 1 i t l l l 1 1 l. l A II .6 i I I I' .l
l APPENDIX III Review of Diesel Generator Building i at Midland Plant by i C.A. Miller and C.J. Costantino l f Structural Analysis Division Department of Nuclear Energy Brookhaven National Laboratory Upton, NY 11973 l l October,1983 1 i ^I i i
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Table of Contents 1.0 Introduction.................................................. 1 2.0 Evaluation of Petinent Work ................................... 2 i 2.1 History of Structure..................................... 2 2.2 Settlement History....................................... 3 2.3 Crack Patterns ........................................... 6 2.4 Structural Analysis...................................... 7 2.4.1 Bechtel's Computation of Settlement Stress (Ref. 2).......................................... 8 2.4.2 Bechtel's Analysis Using Measured Settlements (Ref. 3).......................................... 9 2.4.3 Matra's Analysis Using Heasured Settlements (Ref. 4)......................................... 10 2.4.4 Estimation of Stresses from Crack Data (Ref. 5) .........................................10 2.5 Stress Totals ........................................... 11 2.6 Survey Data............................................. 12 + 3.0 As ses s ment of the Di esel Generato r Bui l di ng.................. 12 4.0 Response to Concerns of R.B. Landsman.....'................... 13 5.0 Conclusions.................................................. 16 References........................................................ 18 Appendix ..........................................................A-1 I I k
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1.0 INTRODUCTION
This report describes a study undertaken by Brookhaven National Laboratory (BNL) to evaluate the extent to which settienent cracks observed in the Diesel Generator Building (DGB) at the Midland Nuclear Power Plant impact on the ability of the building to satisfy design requirenents. Dr. R.B Landsman, of Region III, has raised questions regarding this safety issue (Ref.1). The specific objective of this study is to assess the significance of his connents and to prepare a written response. This objective was achieved by reviewing the existing pertinent work (published reports, testimohy and analytical studies), and by interviewing key j personnel so that a correct, interpretation of the work performed could be made. Additional calculations were specifically omitted from the scope of this study. _All of the conclusions drawn in this report are based on'an assessment of calculations and studies performed by others. The stu@ described herein was carried out during the period of August through Septenber 1983. On August 4, a meeting was held at NRC to discuss the problem and to obtain some of the pertinent literature. Some of this litera-ture was carried back to BNL while other documents were mailed to NRC during the following week. Appendix A contains a listing of all reports used during the program. On August 24, a meeting was held at 8echtel Corporation offices l. in Ann Arbor Michigan. Presentations were made by Bechtel and Consumers Power staff summarizing the work performed by project personnel to demonstrate the adequacy of the DGB. Their consultant's (Dr. M. Sozen of the University of Illinois and Dr. G. Corley of Construction Technology Laboratories).also discussed their work. 1 An inspection of the DGB was held on the evening of j August 24 and during the morning of August 25. At this inspection, the cracks } were observed although no new detailed crack maps were made. Discussions were held with construction personnel to determine the sequence of concrete place-ment. Further interviews were held at MC on September 8. Indiv1 dual inter-views-were held with Dr. Harry Singh (soils consultant for NRC from the Army Corps of Engineers). Joseph Xane (fftC staff), and Lyman Heller (NRC staff). l s .....-._J.......-+. re ...*,,.e-
- = - - i A combined interview was also conducted with Frank Rinaldi (NRCstaff), John 4 Matra (structural consultant for NHC frum Naval Special Weapons Center), and Dr. Gunnar Haarstead (structural consultant for NRC). The purpose of these interviews was to explore the role each played in the design and analysis of the DG8 and to learn of their concerns regarding the adequacy of the DGB. An audit of the DG8 calculations by the task group was held at 8echtel's Ann Arbor offices on September 12 and 13. Dr. Sozen was present on September
- 13. The following itens were reviewed in detail during this audit: nume ri-cal models used by Bechtel to calculate stresses in the DGB due to settle-ment; the magnitude of. stresses due to the various load cases; the method of determining stresses from c' rack data; the accuracy of the survey methods used i
to monitor sett1ments; and t.he concrete pour data. A meeting was held with Dr. Landsman of Region III on September 13 at which time his specific con-cerns raised in Ref. I were discussed. This report is organized as follows. An evaluation of the literature is presented in Section 2 of the report. Section 3 contains BNL's assessment of the adequacy of the DG8, while specific responses to Dr. Landsman's concerns are given in Section 4. Conclusions are listed in Section 5. 2.0 EVALUATION OF PERTIIENT WORK 1 j The eterial on the DG8 which $tas reviewed during the course of this study is divided into six categories; namely, historical description of the structure and its settelsent behavior; developed crack patterns; structural l l analyses to evaluate settelment stresses; treatment of other loads and l stresses; and survey data. The noterial in each category is described and evaluated in this section of the report. l 2.1 History of Structure t i The DGB is.a.reinforc'ed concrete shear wall building consisting of five t cross walls connecting a north and south wall. The interior walls are 18" i thick while the exterior walls are 30" thick. The structure is 155' by 70' in l 2- .i -r, _w,$_ ,.y.- ..~,. - -,. g. ..e,.,, .,. ~~.,,. _y..-__. 6
plan and is 51' high with an intennediate floor slab located 35' above the foundation. Wall footings are located under each of the walls, the footings being 10' wide and 30" deep. The building is founded on about 30' of various fills overlying the natural glacial till. The fill was placed from 1975 through 1977 with construction of the DG8 begun in October 1977. Concrete was placed in 6 lifts as follows: October 1977 to Elev. 630.5 (foundation) December 1977 to Elev. 635.0 March 1978 to Eley. 654.0 August 1978 to Eley. 662.0 December 1978 to Elev. 664.0 Februa ry 1979 to Elev. 678.3 Within each lif t the pours were generally made from east to west. Construc-tion joints occur in the middle of the cross walls and at the west end of each b4y for the north and south walls, t Large settlements and cracks in the concrete were noticed while the lif t going to Elev. 662 was being poured. Construction was halted while the pro-blem was being studied. It was concluded that the large settlement was due to poor compaction of the fill material. This settlement caused the structure to " hang up" cn the duct banks which penetrate the footings on the cross walls. i The duct banks were cut loose from the DGB foundation in November 1978 and i construction of the building restarted. In January 1979, 20' of sand sur-charge was placed on the site to consolidate the fill. This remained in place until August 1979. In September 1980, a permanent dewatering system was in-i stalled to maintain the water table below Elev. 610. 2.2 Settlement History i t The DGB is founded on approximately 30' of fill material, underlain by a l very stiff glacial till about 190 feet thick. A dense sand layer about 140' thick lies bel'ow the till, which is in turn underlain by bedrock. The j ? ~.
I 4 majority of the fill was placed at the site between 1975 and 1977, with act ual foundation construction completed by January 1978. Iluring July 1978, settle-ments of the order of 3.5 inches (Ref. 7) were noted which were greater than the original 40 year predicted settlenents. Apparently consolidation of the [ fill was taking place as structural dead loads were applied. In addition, the four electrical duct banks under the structural crosswalls were acting as hard points to the foundation since they were in turn being supported by the stiff natural soils below the fill. This caused rotation of the building about the duct banks. Construction was halted during August 1978, a soil boring program under-l taken to determine the problem with the fill and Drs. R.B. Peck and A.J. l Hendron retained to advise on the remedial action. The exploratory program ) consisted of 32 borings (with no undisturbed sampling) and 14 Dutch cone penetreeters. These confimed that the fill had been improperly placed (in j an extremely variable density state) and consisted of varying amounts of co-j hesive as well as granular backfill. Lean concrete was also encountered in i i the backfill. The thickness of silty clay backfill was found to be~ greater j under the south-east side of the building leading to the generally larger settlements on this side. A surcharge program was implemented to attempt to consolidate the fill ) more unifomly. 'In addition, the duct barks were cut loose from the founda-tion in Novesber 1978 to eliminate the foundation hard points. Surcharging began in January 1979 and remained in place unt11' August 1979, when it was i determined that primary consolidation had been completed. Instrumentation (primarily settlement plates and Borros anchors) placed in the fill was used to arrive at this conclusion. It should be noted that the consolidation test results, obtained from undisturbed samples taken after completion of the sur-charge program, did not confirm this conclusion. Da":a.was sufficiently scattered to indicate that the fill may not be uniformly consolidated. Unfor-tunately, the boring' program conducted after the surcharge' program was com-plated, did not include cone penetrometer soundings for caparison with the j . readings taken before the surcharge was applied. j ;. 1 1 I i i- --~~ " - - ~ . i - - - - - -, - - -. -. ~ ~ - 45
At the conpletion of the surcharge program, it was decided that since loose sands still existed in the till, a pernenent dewatering system would be installed to preclude the potential for soil liquefaction during a seismic event. This dewatering caused additional settlenents to be developed at the site, but apparently these were related to deep seated consolidation of the ) natural soils under the fill, and would be nere uniform than the settlenents l caused by the fill consolidation. It is questionable whether the piezometer data was of ary significance in analyzing the excess pore pressure condition developed in the fill during the consolidation process. The readings indicate generally very low pore pres-j sures, about 1/20 the mapitude of the applied surcharge pressures. It is not clear in fact whether the fill was ever fully saturated at the time of the surcharge program, i Peak settlements anticipated at the end of 2025 (actual settlenents to date plus secondary settlements from now till then) are specified in Ref. 7 to vary from 4.79 inches (under the NW corner) to 9.33 inches (under the SE i t corner). However. It should be mentioned that the exact settlement history at the various settlenant narkers at the DG8 is open to question. For example, i j It is mentioned in Ref. 7 that the maximum settlements in August 1978 were about 3.5 inches. Yet the data used in the stress analyses for the i presurcharge period (Figures ES-14 of Ref. 7) indicates peak settlements of only 1.99 inches.. It was stated at one of the Bechtel presentations that i prior to cutting the duct banks 1oose from the footing, footings along the ~ North wall actually lifted off from the soil, with the DG8 rotating about the l duct banks. There is no indication of this behavior in ary of the settlement l data used in the computations. Ref. 8 lists the settlement increment from 8/79 to 12/2025 to be 2.36 inches under the SE corner of the building. For the same period Ref. 7 lists this data as 1.89 inches. Thus some inconsistencies appear to exist in the various documents. } l L,i na =-
2.3 Crack Pattisrns Af ter it was detennined that settlement was a problem, Bechtel initiated a program to nonitor cracks in the structure. In general cracks wre visually observed and an optical comparator used to detennine crack width. Crack widths greater than 10 mils wre of specific interest as this corresponds to reinforcing stresses of about 10 ksi. Crack maps were prepared based on surveys conducted during Decenter 1978, Septenber 1979, February 1980 and July l 1981. Dr. Corely observed the cracking in January 1982 (Ref. 6) and confinned that the general pattern of cracks agreed with the July 1981 Bechtel crack maps. He prepared a detailed crack map for the center interior wall. A comparison of this center w'all map (Fig. 4.21 of Ref. 6) with that prepared by Bechtel in July 1981 (Fig. 417) indicates that more cracking had occurred although the widths of the cracks appear to be about the same. Cracks were observed during the BNL. Inspection of the plant on August 25, 1983 and some photographs taken. In general the pattern of cracks appears to = be similar to the previously mapped cracks. However cracks, which had not been shown on arty of the Bechtel cracks maps, were noted in both the north and south walls. These additional cracks are in the lower level (up to Elev. 664) and run at 45 degree angles to the horizontal up to the cross walls. The first crack maps prepared from the December 1978 survey indicate vertical cracks in the cross walls dich begin near the bottom of the wall and run up to Eley. 664 (this was the too of the concrete pour at the time the settlement problem was first noticed). The pattern of cracking is more severe i I in the east side of the building. This crack pattern is compatible with the model that assumes the cracks result from flexural stresses caused by the building " hanging up on the duct banks". No crack maps were prepared for the north or south walls. Th second set of crack maps were prepared from the September 1979 survey. In general. mary of the cracks which occurred in the east wall prior to { placing the surcharge do not appear on these maps. The east center and center walls show the same type of crack patterns as shown on the first crack maps i except for the appearance of additional cracks. These maps also show cracks l.
in the upper level of the building. These cracks occur near the south side of l the building in the cross walls. The cracks tend to be vertical with some i inclination of the cracks near the south wall. Some cracks are indicated in these maps for the south wall. Primary cracking occurs in the east side of the wall and are concentrated in the upper portion of the wall. The north wall is shown to be more severely cracked than the south wall and contains mostly vertical cracks in the upper part of the wall. The cracks appear to be 1 centered about the three interior walls. l The third set of ciack maps were prepared from the July 1981 survey. These maps indicate the same type of cracking as before although the cross wall now contain more cracking near the north side of the building than was i evident before. The west wall contains many more cracks than were shown previously. These cracks run from the Elev. 664 level down to the base of the structure. l it appears that many of the cracks which have occurred may be attributed f, to the building resting on the duct banks. Other cracks have occurred.' how-i ever, which were most likely caused by differential settlement of the wall - 3 footings. Comparison of successive crack observations generally indicates that more cracks are occurring, but that the maximum size of the cracks is still about 20 mils. 2.4 Structural Analyses t The various analyses which have been used to evaluate stresses in the DG8 { are discus' sed in this section. The first analysis described is the method used by Bechtel to estimate stresses due to settlement for use in its load cabination study. This analysis makes use of the straight line approxime-tions to the profiles of the settlements of the north and south walls. The second and third analyses described are the Bechtel and Matra studies, which attempt to use the actual measured,settlemente to estinte settlement stresses. These analyses. *"ah different in detail, lead in tha similar gecemc/W. _ conclusion that the settlement masurennts were (and continue to'be significant error. The fourth analysis describes a cruder modni which attenets to approxiste an upper bound to settlem -f ) ca.r-Ke*2l PI A 1. d y.s c
the crack measurements. The first three analyses are based on detailed finite elenent models. *ile the fourth is based on crack patterns and crack widths. 2.4.1 Bechtel's Computation of Settlecent Stresses (Ref. 2) Since the building settlements occurred den the structure was in various stages of construction, the settlement stresses were evaluated fc r four dif-ferent time periods. The first period spans from the beginning of construc-tion through August 1978 at which time construction was halted. The second time period extends from August 1978 to January 1979 during which the duct banks were cut loose fran the structure and construction resumed. The third time period extends from Jahuary 1979 to August 1979 during which time the surcharge was placed. The last time period extends to the year 2025 and includes measured settlemnts from August 1979 to December 1981 as well as the predicted settlements over the forty year life of the structure. The actual measured settlements were used to calculate stresses for the first perio'd. Stresses were calculated in each of the walls by determining the arc of a circle which fit any three adjacent measured displacements. The - radius of the arc was then used to find the resulting bending mount in the wall, and the moment used to calculate stress. The maximum stress in each of the walls was assumed to exist over the entire wall. The stress in the south l wall was 11.3 ksi; the east wall 6.6 ksi; and all other walls 2 ksi. The incranents in stress which occurred during each of the other three i time periods were evaluated using a finite elenent model of the DGB. This model was constructed and run on the 8echtel version of SAP (BSAP). The l building was defined with 853 nodal points. Plate alements are used to model the walls, and beam elements used for the footings. Eighty-four (84) boundary elements were used to model the vertical soil stiffness (equivalent to the coef ficient of subgrade reaction). An iterative process was then used to determine the stif fness of these boundary elements. A best fit straight 1tne was first fit through the measured ' settlements for the north wall and another straight line fit to the data for the south wall. It was shown that the measured displacements departure fran the best fit straight lines is within the tolerance of the survey data. Dead load reactions were next estimated at
e each of the 84 boundary elements. The stiffness of atly soil element was then determined as the ratio of the dead load reaction to the displacenent of the best fit straight line. The BSAP program was run and the reaction found at each of these boundary elements. A new stif fness was then calculated as the ratio of the reaction to the displacement of the best fit straight line. This process was continued for several iterations. It is our opinion that this model will yield unconservative estimates of i stresses. If tne iteration process were successfully completed, the deforma-tion of the north and south walls will be straight lines. The only stresses that would be competed would then occur due to racking of the structure caused j by the difference in the north and south wall straight ines. It should be clear that if a best fit plane could be passed through all the settlement points under both the north and south walls, no stresses would be computed artywhere in the building. The stresses computed by this approach are a function of Wiich iterative cycle is used to define to soil spring parameters, and bears no resemblance to the acturi soil conditions at the site. There is { no reason to expect that the soil stiffness should vary from point to point as j shown by the analyses. We therefore conclude that this approach to compute j settlement stresses is inappropriate. 2.4.2 Bechtel's Analysis using Measured Settlenents (Ref. 3) This analysis was performed using the same finite elenant model described a bove. This time however, the known survey displacement data was input to the program at the ten (10) wall intersection points. The settlements used were the displacement increments measured for the fourth time period described above. At the remaining 74 boundary elenent points, the structure was allowed to deform as' required to maintain equilibrium (forces equal zero). It was found that computed stresses were very high in those elements adjacent to the wall intersection, but fall.off rapidly away fran these points. This indi-cates that the analysis overly penalizes the structure by imposing large con-centrated forces at the wall intersections. In fact, at some points, the soll 1s required to pull the structure downward to match these known displacements. .g. i -+
t A modified analysis was perfonned by Bechtel at the suggestion of the ( task group. Rather than input only the ten known displacenents, a snoothed curve was generated which matched the known settlement data, but eliminated the sharp profile changes developed in the analysis described above. A best fit polynonial was passed through both the north and south wall settlements, l and displacenents computed at all boundary element points of the finite j element model. Comparative plots of wall profl]esJdicate that this appr ch would still yield high stresses. 2.4.3 Matra's Analysis Using Measured Settlements (Ref. 4) l The analysis performed'by Matra is similar in intent to that described i a bove. Differences between the two are as follows. First, this finite element analysis was performed for all four time periods described in Section 2.4.1. Three separate finite element models were used to define the DGB at various stages of construction. For each problem analyzed, the known settle-i ment data at the wall intersection points was input to the models. The report l does not specifically state dat input was used at the rennining boundary element points between the wall intersection. However, at the interview, Matra stated that a linear displacement profile was assumed between these points. The stress results of the analyses are similar to those described above for the Bechtel study, with similar conclusions reached. In fact, it I can be anticipated that the Matra stress calculations would be even higher l than the corresponding Bechtel results due to the. linear assumption between data points. If in fact this was done, the conclusions reached in that report would be of little value since such high bending stresses would be generated 1: at these discontinuities. 2.4.4 Estimation of Stresses from Crack Data (Ref. 5) Sozen considered the problem of predicting reinforcement stresses from a knowledge of the crack patterns. He observed that the usual problem is to predict crack width based upon a given reinforcement stress. When these methods are applied to the DGB center wall, a 20 ksi steel stress is consistent with c crack width of 20 mils. He also adds the crack widths for a series of cracks in the center w111.and equates this to the total' elongation '} J ' - :) ~ Ei b
- _ ~. r in the reinforcement. Ilsing an estimated gage length over which this elongation occurred he obtains an estimted stress of 24 ksi, and indicates a probable range of 20-30 ksi considering the uncertainties of the method. (This was preserted by Sozen at the August 24 neeting). It is likely that 4 these stress values would be reduced with time. A major cause of cracking was the hard points provided by the duct banks. Mien these were cut free, one l would expect the stresses induced by the uneven support to be relieved. Creep in the concrete would also tend to relieve the settlement-induced stresses. Rinaldi (pg.11086 of the testimony) reported at the interview of Septanber 8, that he calculated stresses using Sozen's method in each of the 5 cross walls, as well as the' north and south walls. He then added these stresses to the maximum stress reported in each of the walls by Bechtel. The resultant maximum reinforcement stress was found to be less than 54 ksi (the allowable limit). It was noted that the Bechtel stresses already included settlenent stresses (to an unknown degree however) from the analyses described in 2.4.1. The crack-based estimates of settlement stresses were added to the i maximum of the Bechtel stresses without regard to Wiere they occurred. While this is a conservative approach, there is no documentation of the computa-j tions. It should be noted that there would be some question,in the applica-tion of this method on those walls where relatively few cracks occurred. } l 2.5 Stress Totals i The finite element model described in 2.4.1 was used to calculate wall i forces from all loadings except for the seismic loading. A lumped ness model i j was used to detennine forces resulting from the seismic loading. These forces were then combined according to the load combinations required in ACI 318 and ACI 349. Critical elements were then identified in each of the walls and Bechtel's program OPTCON used to evaluate reinforcement stresses. OPTCON i - detemines the reinforcement stress resulting from out-of-plane bending moment plus in-plane shear loading. The shear capacity of the concrete is deducted from the total shear load with the difference assumed to be carried by the reinforcement. The following are peak ' reinforcement stresses reported by Bechtel fcr the critical load cases: north wall - 22 ksi; south wall - 34 ksi; west wall - 29 ksi; east wall - 23 ksi; and interior walls - 20 ksi. 4 The allowable steel streess is 54 ksi. 4 ' %s a ,.,,,..g n-- 4
2.6 Survey Data i Bechtel reports that the accuracy of the survey data oescribing the DGB settlements is 1/8" until the surcharge was removed and 1/16" since that time. 4 l Standard survey techniques and equipment were used. 3.0 ASSES $ MENT OF THE DIESEL GENERATOR BUILDING l The DGB has undergone very large settlements which have undoubtedly ) caused serious structural distress. This distress is manifested in the cracks which have occurred in the building. The purpose of this section of the report is to give an opinio'n as to (1) whether the building is structurally sound and (2) whether the bu.ilding still meets the criteria as stated in the FSAR. An important issue is whether the major part of tha settlement has occurred. The settlement data indicate that settlements are well into the secondary consolidation phase so that large additional settlements would not be anticipated. This leads to confidence that predictions of the adequacy of the structure based on settlenents which have taken place to date should hold for the 11fe of the structure. Certainly, settlements should be monitored and the problem reconsidered should more than the anticpated additional settle-l ments occur. Relative settlements of points on the structure of.005" are I significant. The accuracy of the settlement naasurenents should be refined to reflect this requirenent. While significant cracking has occurred in the structure, it would appear that there is little evidence'to indicate that the structure is unsound. The _ structure is very massive and is not subjected to large loadings. Even the f tornado and seismic loadings do not Nroduce large stresses and usually th'es'e stresses occur at locations that are not critical locations for the settlement ' stresses. ~ It is difficult to show that the stresses in the DG8 nest the criteria of _ the FSAN. Bechtel's straight line analysis (see 2.4.1) is based on the clain' j that the settlenent survey data is not sufficiently accurate to calculate ], ?
n structural stresses. The adjustent they make to account for this inaccuracy gives results that are likely unconservative. If conservative assumption, are made then the calculated stresses are too large to satisfy the criteria and not consistent with the crack patterns observed in the structure (see 2.4.2). It is doubtful whether any analysis could now be developed which would pro-vide more realistic estimates of settlement stresses with the required degree of confidence. 8 The most likely source for obtaining reasonable estimates of settlement stresses are the crack studies (see 2.4.4). However, these studies must be documented much more completely than has been done to date. It is imperative that significantly better mettio'as~be used to monitor crack growth than is ~ i currently being considered..Whitamore strain gages should be used exten-sively. Plugs are attached to the concrete on a 2" gage. An instruant is then used to measure the distance between the plugs. Accuracies of.0001" is routine. Such gages would give a good picture of the overall behavior of the crack s. It should be noted that the repair of cracks would not interfere with the use of these instruments. No special " windows" need to be maintained during the crack repair program. This program of crack monitoring is also important because there is some indication that cracks in the DG8 have not - stabilized and that the number of cracks may in fact be increasing. 4.0 RESPONSE TO CONCERNS OF R.B. LANDSMAN i The Region Ill inspector has raised four concerns (Ref.1) regarding the adequacy of the DGB. Each of these is addressed in the following. Concern 1: FINITE ELEENT ANALYSIS i The first (;oncern deals with the Bechtel finite element models (see 2.4.1 ~j and 2.4.2) of the UGB used to evaluate stresses due to settlement. There are four objections made to the models. Concern is raised with regard to the use of uncracked section properties while the concrete is known to be cracked. All concrete structures are 1, i i l j
N cracked and it is standard practice (specifically pennitted in the ACI code) to determine forces in concrete structures based on gross section properties (i.e., neglect the cracks in the concrete and the reinforcement). If cracked section properties were used then the stresses calculated by Bechtel (2.4.1) would have been smaller. Therefore neglecting cracks in this analysis is a l conservative approxistion. On the other hand, the analysis reported in 2.4.2 was used to show that the measured settlements result in stresses which are so a high that much more severe cracking would be expected than was observed. It was then argued that the measured values must be in error. If cracked sections were assumed for this analysis the calculated stresses would have been smaller, but probably still not consistent with the observed crack 4 patterns. i The straight line representation of the settlements along the north and south wall for the analysis reported in 2.4.1 is said to be in error. As in-dicated in that section of this report, it is our opinion that this analysis 4 l will result in unconservative predictions of stresses due to settlements. As such, it is considered to be an inappropriate analysis. 1 1 The third part of this concern iaises questions regarding the time effects of the settlements. Bechtel does calculate stresses for different I l phases of the settlement. The structure was changing during the significant settlement period. Construction was-still in progress during the largest j settlements. Therefore the structural geometry changed as did the concrete properties (while maturing).- The Bechtel models did not account for these I changes. This wou'Id have been conservative for the calculation of stresses, but would result in lower stresses in the analyses perfonned using the measured r,tttlements as input. i 4 The fourth objection deals with the claim that the NRC staff did not 4 approve of the Bechtel analysis. It appears that this is the case and the intention of the staff was.to use settlement stress data based on an analysis of the cracks rather than the finite element analyses. , 4 1 .v-, -g-
e a b - 7 Concern ?!' HELIABILITY OF MEASURLD SETTLEMENT VALUES y s . s. \\ Th& analytes"repiirted in,2.4.2 and 2.4.3 were used to show that stresses s .s compu?.ed fr'on'strustbral mdelS subjected to the measured settlenents are very 'N v. . t s s Mgh'and would indicate cracktre in the structure where no cracks are ob-i terved. 'he objection is' raise.d Ulat a linear model was used and that a non-linear model, accounting br plastic ef fects would result in a redistribution ^ 1 of st7 esses and the same c00clusicn oay not apply. This observation is true, 1-but by itself would not change the ofKlusions drawn from these analyses. ~ m. s s ~~ ~ As stated above, however, there 4re other factors which when coupled with l this objection may result in a different conclusion. The other important factors are: the assumed shaps of the settlement between the measured points; ei t,the differing geomet.y of the DGB when the various phases of settlement occurred. Concern 3: STRESSES DETERMINED FROM CRACX SIZES s If the finite element analyses are not reliable then one alternative ' approach is to find settlement' stresses frm a study of the crack sizes The N \\ a
- ,^
objection raised is that this appr'oach is not consistent with nonnal engi-l reering practice and that there ire no equatkons avillable to evaluate j . stresses from crack data when the stress fields are as complex as occur in the DG8. 'It is true tMt this would not be standard practice, but "non-standaro" 'anaiys'e'i may bp used provided they are sufficiently_ powmented and shown to ~ - gQresults that are conservative. .' \\ s. s s.- i 'N 's Anapgoa%ch that could predict approximate settlement stresses in the DGB s could preably be used to deyonstrate its adevacy. This is true for two s reasons. VlNt.~5 tresses In the structure due to otherloadings are rather low and therv(15 a large reserve for settlement stresses. Second, if large settlement stre'sses and local yieldin,g 'of the rettiforcement occurs, the s i n 1 resulting deformatjons of the structure will<'redace the settlement induced s x, ~ S ~ s loadings. ] s .4 ,e. gg . ) ,13, g s s \\ ' ' l '\\,' [ g x i s,,j ~.6.{- -) \\'" .l. ' **,\\. j. ' i p %'., .1 v j' 'l 3. .m
I The documentation of the crack analyses used to determine stresses is not su f ficient. There is no calculation on record which calculates stresses in all of the walls using this metnod. There is also no written justificatio} sht, wing that the trethod may be used for structures like the DGB. Concern 4: CRACK MJNITORING l This concern deals with the lack of a good crack monitoring system and specification of action to be taken if the cracks exceed certain limits. As stated in Section 3.0, it is our opinion that the planned crack monitoring ~ ~ systen is not adequate. More reliable gages (e.g., WhTtemor'eitr'ain Gages) should be placed in areas where cracking is now evident. These gages can be used even af ter crack repairs are made. Two limits are now defined in the current crack monitoring program. If the crack width reaches.05" (Action Limit) a meeting will be held to evaluate what steps to take when the cracks reach the next limit. The next upset limit is set at.06" (Alert Limit). It is our opinion that the form of this plan is adequate, but that the specific threshold numbers must be based on a resolu-tion of the current settlenent stresses. A safety argin must be left for the other potential loading events, such a's tornado or seismic loads, with the re-maining allowable stress allocated to future potential settelnents. I Unce this limit was reached the only solution would be to make a struc-tural repair. The exact fonn of this repair would depend on the location and l extent of the crack which exceeded the limit. The planned response could not specify the nature of the repair, but could indicate that an exceedance of the l Alert Limit would result in a structural repair rather than performing addi-l tional analyses. I 5.0 CONCLUS!UNS Based on the review of the studies performed to demonstrate the adequacy of the DGB, the following conclusions are drawn: ! i
\\ l 1. The settlenent data indicates that primary consolidation of the fill is comoleted." How it is recommended that the faiGimolles in the documentation of the settlement history be e w resolved. (See last paragraph of Section 2.2). t 2. It is unitkely that a satisfactory stress analysis can be m perfomed based on the measured settlement data. 'It is 7ecommended'that settlement stresses be estimated from the N { crack width data. The existing work that has been done in j this a rea must be completely documented. 1. It appears that,th'e nusber of cracks in the DGB are con-tinuing to increasey J It is essential that a better .s crack monitoring program be established as outlined in N Section 3.0. L w 4. The upset crack width levels specified in the crack monitoring program should be chosen so that a sufficient Q stress margin is available to resist the critical load combinatic'ns. 2 1 5. If the Alert Limit (in @ack width) were exceeded, specif st@ctural @epaifs should be mandated. C j
- h. While significant cr'acking has occurred'in the DGB, it i
.is our npinion that the st(r) cture will continue to fulfill its functional. requirement. This conclusion is based on the f act that stfessasinduced in the stfu'cture by all other ext @eme loadings are small.. l r .J G-h ~ ] g a 1 ~ 1 _ 17-1 i.., c
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REFERENCES 1. Hemorandum for R.F. Warnick through J.J. Harrison from R.B. Landsman, Subject Diesel Generator Building Concerns at Midland, dated July 19, 1983. 2. Bechtel Calculation No. DQ-52.0 (Q), Rev. 2. 3. Bechtel Calculation No. Dy-52.7 (Q) - Finite Element Calculation of Settlenent Stresses Using Actual Displacements. 4. Structural Reatalysis bf Diesel Generator Building Utilizing Actual Measured Deflections as, Load Input, by John Matra, Naval Surface Weapons Center. 5. Evaluation of the Effect on Structural Strength of Cracks in the Walls of the Diesel Generator Building Midland Plant Units 1 and 2, by Mete Sosen, February 11, 1982. 6. Effects of Cracks on Serviceability of Structures at Midland Plant, by W.G. Corely, A.E. Fiorato, and D.C. Stark, April 19, 1982. 7. Executive Summary, Diesel Generator Building, Midland Plants Units 1 and 2 August 1983. 8. Letter from CPCo to NRR dated October 21, 1981; Enclosure 1 Tech. l Report, Structural Stresses Induced by Differential Settlement of the DGB. .1 i 'I i l i i i i t ( A
APPENDIX A: SUURCE MATERIAL FOR STUDY Site Specific Response Spectra Midland Plant Units 1 & 2 Addendum to Part 1 Response Spectra--Orginal Ground Surfaco Jan 81 Weston Geophysical Corp Site Specific Response Spectra Midland Plant Units 1 & 2 Part II Response Spectra Applicable for the top of fill material at the plant site April 81 Weston Geophysical Corp Site Specific Response Spectra Midland Plant Units 1 & 2 Part III Seismic Hazard Analysis Feb 81 Weston Geophysical Corp Soil Boring and Testing Program Midland Plant Units 1 & 2 Test Results Foundation Soils t i Auxiliary Building Woodward-Clyde Consultants Aug 81 i Docket No. 50-329,50-330 Test Results Perimeter and Baffle Dike Areas Soil Boring and Testing Program i Volume II Supporting Data July 81 Docket Nos. 50-329,50-330 Test Results Perimeter and Baffle Dike Areas Soil Boring and Testing Program Volume I Woodward-Clyde Consultants July 81 Docket Nos. 50-329,50,330 Estimates of Maximum Past Consolidation Pressure of Cohesive Fill Materials Diesel Generator Building July 81 Woodward-Clyde Consultants j Docket Nos. 50,-329.50-330 USA /NRC Before The Atomic Safety and' Licensing Board 12/7/82 testimony of; Frank Rinaldi l John Matra f Gunnar Harstead with respect to the Structural Adequacy of -The Diesel Generator Building at Midland Official Transcript Proceedings Before NRC Atomic Safety and Licensing Board L DKT/ CASE No. 50-329,50-330 OL & OM 12/10/82 pages 11008 through 11228 A-1 i i b n.
Evaluation Report for Concrete Cracks in the Diesel Generator Building Consuuers Power Conpany 2/16/82 Evaluation of the Effect on Structural Strength of Cracks in the Walls of the Diese1 Generator Building Mete A. Sozer. 2/11/82 Relationship of Observed Concrete Crack Widths and Spacing to Reinforcement Residual Stresses Consumers Power Company 6/14/82 I Observed Cracks in Walls of Midland Plant Structures 6/14/82 Corley and Fiorato Portland Cement Association Safety Evaluation Report related to the operation _ of Midland Plant Docket Nos. 50-329 and 50-330 Consuners Power Company USNRC 5/82 Effects of Cracks on Serviceability of Concrete Structures and Repair of Cracks Consumers Power Company 4/30/ 82 Effects of Cracks on Serviceability of Structures at Midland Plant Corley, Fiorato, Stark Portland Cement Association Summary of Sept. 8,1981 Meeting on Seismic Input Parameters Midland Plant USNRC 12/3/81 1 ~ USA /NRC Before the Atomic Safety and Licensing Board 50-329,50-330 t.estimory of Jef frey K. Kimball 9/29/81 s NRC Atomic Safety and Licensing Board 50-329 OM,0L 50-330 DM,0L witnesses; - Johnson j Burke .Corley i, Sozen Gould NRC Before the Atomic Safety and Licensing Board (nodate)' NRC staff testimony of Joseph Kane on Stamiris Contention 4.B Docket Nos. 50-329 OM,0L 50-330 UM,0L Safety Evaluation Report related to the operation of Midland Plant October 82 Docket Nos. 50-329 50-330 l USNRC NUREG-0793 Supplement No. 2 l Safety Eval'uation Report related to the operation of Midland Plant June 82 Docket Nos. 50-329 50-330 L USNRC NUREG-0793 Supplement No.1 i t A i
u
w
e NRC Atomic Safety and Licensing Board 9/29/81 Applicant's Brief on Compatibility of Site Specific Response Spectra Approach with 10 CRF.part 100 Appendix A Safety Evaluation Report related to the operation of Midland Plant May 82 Docket Nos. 50-329 50-330 NUREG-0793 ~ Response to the NRC Staff request for Settlement Related Analyses for the Diesel Generator Building 6/1/ 82 Consumers Technical Report Structural Stresses Induced by Differential Settlement of the Diesel Generator Building Consumers Power Compar1y Test Results of Soil Boring. and Testing Program for Diesel Generator Building Docket Nos. 50-329 50-330 7/31/81 . Consumers Power Company Final Results of Soil Boring' and Testing Program for Perimeter and Baffle i Dike Areas 7/27/81 Docket Nos. 50-329 50-330 Consumers Power Company NRC Atomic Safety and Licensing Board Docket Nos. 50-329 OM,0M' 50-330 OM,0L Witnesses; Hood 12/3/81 Kane Singh Rinaldi NRC Atomic Safety and Licensing Board Docket Nos. 50-329 OM,0L : 50-330 OM,0L Witnesses; Kennedy 2/17/ 82 Campbell Rinaldi Kane Matra Hood Singh CSE Input to the Midland SER Supplement Aug. 82 Geotechnical, structural, mechanical and hydrologic inputs for the Midland Ser Supplement i t Transcript of Proceedings USA /NRC 1/6/81 . Deposition of Frank Rinaldi Transcript of Proceedings USA /NRC 1/9/81 Deposition of Pao C. Huang Transcript of Proceedings USA /NRC. Dock'et Nos. 50-329 OM, OL 50-330 OM,0L Deposition of Jchn P. Matra 1/7/81 l i .A-3 i. ...a I ^ .;-e 4' J r . ~.. - ,+ +
USA /NRC Before the Atomic Safety and Licensing Board Docket Nos. 50-329 UM-OL 50-330 UM-OL i NRC Staff Brief in Support of the use of a Site Specific Response Spectra to comply with the Requirenents if 10 CFR Part 100, Appendix A 9/29/81 USA /NRC Before the Atomic Safety and Licensing Board Docket Nos. 50-329 OM-OL 50-330 OM-OL 4 Testimony of Dr. Paul F. Hadala with Respect to the Study of Amplication of Earthquake Induced Ground Motions and the Stability of the Cooling Pond Dike Slopes Under Earthquake Loading 9/29/81 4 USA /NRC Btfore the Atomic Safety and Licensing Board Docket Nos. 50-329 UM,0L 50-330 OM,0L Witnesses; 8cos Hendron Hanson Testimony of Ralph B. Peck before the Atomic Safety and Licensing Board, in the the matter of Consumers Power Comparty (Midland Plant, Units 1 and 2), Docket Nos. 50-329 OM,.50-330 DM, 50-329 OL, 50-330 OL, notarized Nov. 3,1982. Letter from CPCo to H.R. Denton dated June 14, 1982 with Enclosure " Response to the NRC Staff Request for Additional Infonnation Required for Completion of Staff Review of Soils Remedial Workd dated June 14. 1982. ~ Summary of August 17, 1982 Meeting on Soils-Related Construction Release, dated Septanber 7,1982, by Darl Hood. 1 " Structural Reanalysis of Diesel Generator Building Utilizing Actual Measured Deflections as Input", by John Matra.. Letter from CPCo to H.R. Denton dated October 21, 1981 with
Enclosures:
" Structural Stresses Induced by Differential Settlement of DGB", "Subgrade Modulus & Spring Constant Values for DGB Structural Analysis", 4 l " Bearing Capacity Evaluation of DGB Foundation" { "Logtern Monitoring of Settlenent for DGB", l " Relative Density and Shakedown Settelsent of Sand under DGB", " Estimates fo Relative Density of granular Fill Materials DGB", l " Review and Control of Facility Chagnes to DGB", l "DGB Bearing Pressaure due to Equipment and Connodities", Report form Woodward-Clyde to CPCo dated June 10,1981, " Preliminary Test Results. Soil Boring & Testing Program, Perimeter and Baffle Dike Areas", " Seismic Margin Review, Midland Energy Center Project": Volumne 1. Methodology and Criteria, dated February 1983. Volume V Diesel Generator Building, dated July 1983, prepared for CPCo by Structural Hechanics Associates. ~A-4 .i .. ' x' 3%v:3, 's;-&. ~ o
O Applicant's Propsed Findings of Facts and Conclusions of Law on Remedial Soils Issue Docket Nos. 50-329-0M 50-330-0M 50-329-OL 50-330-OL Testimony of Karl Weidner for the Midland Plant Diesel Generator Building September 8, 1982 Docket Nos. 50-329-OL 50-330-OL ~ i 50-329-0M 50-330-0M Find Report on the ADINA Concrete Cracking Analysis for the Diesel Generator Building by Gygna Energy Services September 16, 1981 4 l 4 - j A-5 l .~
S' 8 ~ APPENDIX IV. "ENCLO8URE g**Weg% UNITED STAf ts NUCl. EAR REGULATORY COfArAISSION f I ntason seg too noosavsty noao otsu sLt.vu, ett.swoes so) 7,, , r r mr i MEMORANDUM FOR: R. F. Warnick. Director. Office of Special Cases J.g W. THRU: . Barrison. Chief. Section 2. Midland. FROM: R. B. Lands?.au. Reactor Inspector
SUBJECT:
DIESEL CENERATOR BUILDING CONCERNS AT MIDLAND At the recent hearing before Co' ngressman Udall's subcommittee. I
- expre i
because of numerous structural cracks that have occurre building over the years. I also expressed the same concern during the recent ASLB hearings. Mr. Eisenhut.has requested me to document the basis of my concerns about the building so an independent review group can analyze them My first concern deals with the finite element analysis that Consu:sers Power Company (CPCo) used to show I Their model of the building assume,that the building is structurally sound. d a very rigid structure without any cracks. The building has numercus cracks, reducing the rigidity of the structure. The effects of these cracks have not been taken into accou in the analysis. CPCo's interpretation of' the settlement data as a straight line approximation always stems from their position that the t i building is too rigid to deform 'as indicated by actual rattlement readi The settlement of the building occurred over a period of time during diff ngs. phases of construction. It is this time dependent effect that was also not erent used in their model. 3 Even CPCo expert Dr. Corely testified at the ASLB i hearings that the analysis should have "taken into account cracking and ti i dependent effects" in oider to give correct results. me official position, as stated by Dr. Schauer. on CPCo's analysis wasFinally, the st staff takes no position with regard to that ' analysis." . "The My second concern deals with the acceptance of the diesel generator building in the SSER #2 which was subject to the results of an analysi to be performed by the NRC consultants using the actual settlement ) s The consultants testified at the ASLB hearing that this analysis gave values. t unacceptable.results ~and this portion of the SSER should be stricken are basing their unacceptable results and comments on their finding of . -They 1 [ 7 / i Q G A ) 4 .. q. .~..a
t 'JUL1998$ ?. R. F. Warnick. e very high stresses obtained in areas where no cracks exist. Therefore, the actual settlement values are not accurate enough (are in ' error) to be ~ used in an analysis. The consultants, as well as CPCo ran.a linear analysis (structure always in the elastic ran,:e) instead of a plastic analysis which would allow a redistribution of loads in the structure Th erefore. supposed areas of high stress, where cracks are not located, may not ex'ist due to redistribution of loads.. Finally, the staff's official position, as stated by Mr. Rinaldi, on this analysis as performed by the consultants, was that the actual settlement values could not bs relied upon to determine if the diesel generator building meets regulatory requirements. My third concern deals with the fact that we are not following normal engineering practice in accepting the building by using a crack analysis approach because there is no practical method available tgaay to analyze , a complex structure with cracks in it. The basis of this' concern is that there are no formulas available that can estimate stresses in a complex stress field like those which. exist in this building. Thus, the evaluation { of the structure based on the ' staff's crack analysis using empirical
- unproven formulas to determine the rebar stresses is unacceptable.
i I My fourth concern deals with the staff accepting the building by relying on a crack monitoring program to evaluate the stresses during the service' life of the building. If cracks exceed certain levels, reco:=nendations will be made for maintaining the structural integrity of the building. The basis for my concern deals with the lack of crack size criteria and the lack of formulated corrective action to be taken when the allowed i crack sizes are exceeded. These concerns which I have just enumerated are also shared by members of Mr. Vollmer's engineering staff, as well as their consultant. These concerns ve e documanted in the ASLB hearing transcripts of December 10 1982, prior to my ever expressing my concerns before the ASLB hearing or i Congressman Udall's subcommittee. In summary, since it is impossible to analyze this severely cracked structure to the total staff's approval. I rr. commend some remedial structural fixes be undertaken to ensure the s,tr6ctural integrity of the building.to provide an adequate margin of safety'. ..] ( )bu <h y % Ross B'. Landsman Reactor Inspector cc: DMB/ Document Control Desk (RIDS) e l ....,.v = v=use**r- --- - -- -}}