ML19270E836
| ML19270E836 | |
| Person / Time | |
|---|---|
| Site: | Trojan File:Portland General Electric icon.png |
| Issue date: | 12/21/1978 |
| From: | Mccollum K, Mark Miller, Paxton H Atomic Safety and Licensing Board Panel |
| To: | |
| References | |
| TAC-07551, TAC-08348, TAC-7551, TAC-8348, NUDOCS 7901020187 | |
| Download: ML19270E836 (66) | |
Text
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M NRC PUF.L'C DOCUMENT RCOM y,
UNITED STATES OF AMERICA W*ho
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NUCLEAR REGULATORY COMMISSION c.
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- s ATOMIC SAFETY AND LICENSING BOAP3 i
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Marshall E. Miller, Chairman g
Kenneth A. McCollom, Member Hugh C. Paxton, Member W
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}iEn DEC 2 c..a In the Matter of
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. PORTLAND GENERAL ELECTRIC COMPANY,
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(Troj an Nuclear Plant)
)
December 21, 1978
)
PARTIAL INITIAL DECISION (Interim Operation)
Accearances Roland F. Banks, Esq., Souther, Spaulding, Kinsey, Williamson & Schwabe, Standard Plaza, Portland, Oregon 97204 Maurice Axelrad, Esq., Lowenstein, Newman, Reis and Axelrad, 1025 Connecticut Avenue, N. W.,
Washington, D. C.
20036 Ronald Johnson, Esc., Portland General Electric Company, f21 S. W.
Salmon Street, Portland, Oregon For Portland General Electric Co., et al., Licensee William Kinsey, Esq., 1002 N. E. Holladay, Portland, Oregon For Bonneville Power Administration, Intervenor John H. Socolofsk7, Esc., Decartment of Justice, State Office Buildihg, Salem, Oregon For State of Oregon, Inte: venor 79010201
d
_ Joseph Gray, Esq. and Marj orie Ulman, Esq.,
Office of Executive Legal Director, U. S.
Nuclear Regulatory Commission, Washington, D. C.
20555 For U. S. Nuclear Regulatory Commission. Staff Gregory Kafoury, Esq., Kafoury & Hagen, 202 Oregon Pioneer Building, 320 S. W.
Stark Street, Portland, Oregon Michael Rose, Esq., Nepon & Rose, Suite 101 Kellogg Building, 1935 S. E. Washington, Milwaukie, Oregon 97222 For Columbia Environmental Council, Intervenor Eugene Rosolie, 215 S. E.
9th Street, Portland, Oregon 97214 For Coalition for Safe Power, Intervenor, cro se Nina Bell, 632 S. E.
18th, Portland, Oregon C. Gail Parson, 800 S. W. Green #6, Portland, Oregon David McCoy, 348 Hussey Lane, Crants Pass, Oregon Stephen M. Willingham, 555 North Temahawk Drive, Portland, Oregon, cro se
TABLE OF CONTENTS PAGE NO.
I.
PRELIMINARY STA N NT 1
A.
Issues 1
B.
Evidentiary Hearing 5
II.
FINDINGS OF FACT (INIERIM OPERATION) 7 A.
Description of Building Co= plex 7
3.
Seismic Design Criteria 8
C.
Design Deficiencies in the Control Building 10 D.
Seismic Design and Reevaluation of the Building Complex 12 1.
Original Evaluations and Analyses, 1970-71 12 2.
Reevaluation Methods and Assumptions 13 3.
Reevaluation Using the Stick Model 19 4
Independent Evaluation Using the TA3S Program 20 5.
Reevaluation Using the STARDYNE Program 21 6.
Conservatis=s in Analyses 26 7.
Indpendent Checks on the Design 28 8.
Conclusions on Seismic Capability of the Building Structure 30 E.
Seismic Effects on Equipment 31 1.
Effects of Structural Displacement 31 2.
Effects Using Floor Response Spectra 32 3.
Conclusions on Seis=ic Capability of Safety-Related Equiptent 40
. PAGE NO.
F.
Instrumentation and Oceration to Assure Safe Shutdown 40 1.
Instrumentation to Measure Seismic Events 40 2.
Operational Procedures to Respond to a Seismic Event 41 3.
Capability to Shut Down in Case of an SSE 42 4
Conclusions on Ability to Shut Down Safely 43 G.
NRC Staff Inspection and Evaluation Following A Seismic Event 44 1.
Procedures for Notification of NRC by Licensee 44 2.
Procedures for Inspection of the Facility 44 3.
Conclusions on Assuring Adequate Notification and Inspection 46 H.
Preliminary Activities Relating to Later Plant Modifications 46 I.
Environmental Considerations 47 J.
Concerns of Intervenors and Limited Appearances 49 III.
CONCLUSIONS OF LAW 51 IV.
ORDER 54 APPENDIX
P e
UNITED STATES OF AMERICA NUCLEAR REGULATORY COMMISSION BEFORE THE ATOMIC SAFETY AND LICENSING BOARD In the Matter of
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PORTLAND. GENERAL ELECTRIC
)
Docket No.50-344SP COMPANY, ET AL.
)
)
(Troj an Nuclear Plant)
)
PARTIAL INITIAL DECISION (InterLn Operation)
I.
PRELIMINARY STATEMENT A.
Issues This Partial Initial Decision involves the issue of whether interis operation of the Trojan nuclear facility should be per=itted, pending the approval and completion of certain codifications to the Control Building required to meet the seismic design criteria of the Final Safety Analysis Report (FSAR).
Interim operation of the facility with the Control Building in its as-built condition would require an arendment to Operating License No. NPE-1 for the Trojan plant.
This facility operating license would have to be modified to waive certain Technical Specifications concerning seismic design criteria during interim operation, provided that such operation would be in accordance with specified conditions.
, The Troj an plant is located 42 miles northwest of Portland, Oregon on the Columbia River.
The design of its Control Build-ing was completed in 1970, and a Construction Permit was issued on February 9, 1971.
Construction of the building, including the maj or composite shear walls, was completed in late 1972.
The facility operating license was issued on November 21, 1975 (PGE Exh. 13, pp. 1-2).
While the plant was shut down for refueling in April 1978, the Bechtel Power Corporation studied the feasibility of cutting an opening and installing a security window in a wall of the Control Building.bl During this evaluation of the shear walls of the building, Bechtel identified a potential noncon-formance with the design criteria stated in the FSAR (PGE Exh.
13, p. 2).
This potential nonconfor=ance was promptly reported to NRC's Office of Nuclear Reactor Regulation, which obtained further information and evaluated its significance (PGE Exh.
6, 7).
On May 26, 1978, the NRC's Director of Nuclear Reactor Regulation issued an Order for Modification of License, directing the Licensees l to perform modifications to the 1/ echtel was the architect-engineer for the Licensee Portland BGeneral Electric Company (PGE), and it executed the design for the Control Building and other Troj an structures.
- FGE, the City of Eugene, Oregon, and Pacific Power and Light Ccmpany.
3-Control Building to bring it into substantial compliance with the requirements of the operating license.3/
That Order set forth findings that several design errors with respect to the shear walls reduced the seismic capability of the Control Building.
It further found that the originally intended seismic capability and safety margins should be substantially restored by modifications to that structure, and that operation of the facility with the Control Building in its as-built condition would violate the existing facility license.
The Order also stated that the Control Building had adequate structural capacity to resist the licensed Safe Shutdown Earthquake (SSE), and that the facility operating license should be deemed modified to permit operation, with conditions,4/ in the interim period prior to approval and completion of the required modifications.
3/ rder for Modification of License, May 26, 1978, published O
in 43 Federal Register 23768 (June 1, 1978).
4/
- The conditions under which interim operation would be per-mitted are:
(1) no =odification which may in any way reduce the strength of the existing shear walls shall be made without prior NRC approval; and (2) in the event that an earthquake occurs that exceeds the facility criteria for a 0.llg (reduced at the evidentiary hear'.ng to 0.08g]
peak ground acceleration at the plant site, the facility shall be brought to a cold shutdown condition and inspected to determine the effects of the earthquake on the facility.
Operation cannot resume under these circumstances without prior NRC approval.
(Order, p. 9.)
. The Order for Modification of License further provided that any perton whose interests might be affected by the Order could file a request for hearing.
The issues that could be raised by a request for hearing were:
(1) Whether interim operation prior to the modifications required by this Order should be permitted, and (2) Whether the scope and etneliness of the modifications required by this Order to bring the facility into substantial compliance with the license are adequate from a safety standpoint.
Pursuant to the opportunity for hearing provided by the May 26 Order, timely requests for hearing were filed by the Columbia Environmental Council (CEC), Eugene Rosolie, acting in his own behalf and as representative of the Coalition for Safe Power (CFSP), and by Bonnie Hill, John A. Kullberg, Stephen M. Willingham, David 3. McCoy, C. Gail Parson and Nina 3 ell.
A duly established Atomic Safety and Licensing Board considered these requests for hearing at a Special Prehearing Conference held in Portland, Oregon on July 26-25, 1978.
By an order dated July 27, 1978, the Board granted the hearing requests and intervention petitions of CEC, Eugene Rosolie and CFSP, Mr. Willingham, Mr. McCoy, Ms. Parson and Ms. Bell.
Mr. McCoy, Ms. Parson and Ms. 3 ell were conso'idated
. pursuant to 10 CFR 52.714(e) and adnitted as a single party.
The State of Oregon was granted leave to participate as an interested state pursuant to 10 CFR 52.715 (c).
Subsequently, an untimely petition filed by the Bonneville Power Administra-tion (SPA) was granted, and BPA was consolidated with the Licensees as a party to the proceeding.
B.
Evidentiarv Hearinz A Notice of Evidenciary Hearing was issued by the Board on August 1, 1978 and was published in 43 Federal Rezister 34847 (August 7, 1978).
That notice set forth the scope of the evidentiary hearing as limited to the following two issues :
(1)
Whether interim operation prior to modifications required by the May 26, 1978 Order for Modifi-cation of License should be permitted; and (2)
Whether the scope and timeliness of the modifications required by the May 26, 1978 Order to bring the facility into substantial compliance with the license are adequate from a safety standpoint.
By an order dated Augu:~ 25, 1973, the Board granted the Licensees' notion to bifurcate the proceeding into two phases.
Phase I would involve an evidentiary hearing and a decision on interim operation prior to modifications of the Control
. Building.
Phase II would involve a consideration of the proposed modifications themselves from a safety standpoint.
It was also held that stated contentions regarding the issue of interim operation were not required as to Phase I, because the notice of opportunity for hearing set forth with sufficient precision the issue to be determined (Tr. 6584-85).
The evidentiary hearing on Phase I was originally scheduled for September 6, 1978, but it was rescheduled to October 23, 1978 after the Licensees informed the Board and the parties of additional information which became available in August 1978.
This Partial Initial Decision addresses the Phase I issue of interim operation of the Troj an nuclear facility with the Control Building in its as-built condition.
The Licensees prefiled the written direct testi=ony of Donald J. Broehl, S. R. r?.ristensen, Bart D. Withers, Myle Y. Holley, Jr., Boris Bresler, Richard C. Anderson, George Katanics, Theodore E. Jchnson and William H. White on October 3, 1978.
The State of Oregen prefiled the testimony of Harold I. Laursen on October 6, 1978.
The NRC Staff prefiled the testinony of its witnesses Kenneth S. Herring, Robert T. Dodds and James E. Knight on October 13, 1978.
Additional testimony of Mr. Herring was prefiled on October 16 and November 25, 1978.
. The evidentiary hearing on the issue of interim operation were held in Salem, Oregon from October 23-25, October 30-November 3, and December 11-14, 1978.
Limited appearance state-ments from members of the public were heard in Portland, Oregon on October 26-17, 1978.1/
There were 2,996 pages of transcript.
Wit esses were presented by the Licensees, the State of Oregon and the Staff.
The Intervenors CEC, CSP and Eugene Rosolie, and the Consolidated Intervenors (through Ms. Bell) attended the hearing and cross-examined the other parties' witnesses, they presented no witnesses of their own.6/
Appendix A, but attached hereto, lists the exhibits which were ad=itted into evidence.
II.
FINDINGS OF FACT (INTERIM OPERATION)
A.
Descriction of 3uilding Comolex 1.
The Control Building is ccaposed of a structural steel framing system with steel bea=s and colu=ns supporting rein-forced concrete floor slabs, with shetr walls designed to 5/The Board also accepted all written linited appearance statements which were handed up at any time during the evidentiary hearings (Tr. 523, 632, 1516).
5/ s. Bell offered into evidence Consolidated Intervenors MExh. 3, which was admierec (Tr, 2013).
resist lateral seismic loading or force (PGE Exh. 10, pp. 2-4).
The major shear walls are located around the perimeter of the building, and generally consist of a reinforced concrete core placed between two layers of reinforced concrete block.
The two block layers generally sandwich the structural steel frame so that the reinforced concrete core is partially or completely interrupted by the steel frame members (PGE Exh. 6, Attachment 2, Fig. 3 and 4).
Thus, the building is designed with the steel frame carrying most of the normal vertical floor load, and the block and concrete walls carry most of the lateral load caused by earthquakes (PGE Exh. 10, pp. 2-4).
2.
The Fuel, Auxiliary and Control Buildings constitu-a " Building Complex" and they are interconnected by their foundation systems and floor slabs, which are continuous for the three buildings.
The Auxiliary Building is located between the Fuel Building and Control Building (PGE Exh. 6, Attachment 2, Fig. 1).
The Auxiliary Building is supported laterally in part by both the Control Building and the Fuel Building, with the reinforced concrete floor slabs acting as diaphragms to transfer lateral loads (PGE Exh. 10, p.
4, Tr. 738).
3.
Seismic Desizn Criteria 3.
The requirements governing the design of the Building Complex walls to resist the lateral loads arising f cm an
. earthquake, wind or tornado were in accordance with those from the American Concrete Institute (ACI 318-63) Code for reinforced concrete (Ultimate Strength Method) and the 1967 edition of the Uniform Building Code (UBC-67) for reinforced grouted masonry.
4.
Based upon an evaluation of the maximum earthquake potential at a site, the Safe Shutdown Earthquake (SSE) is that earthquake which produces the maximum vibratory ground motion for which certain important structures, systems, and components at a nuclear plant are designed to remain functional (PGE Exh.
10, p. 8).
The SSE for the Troj an plant as defined in 52.5.2 of the Final Safety Analysis Report is 0.25g and is not in controversy in this proceeding.
5.
In addition to the SSE, Appendix A to 10 CFR Part 100 also provides for the establishment of an Operating Basis Earthquake (OBE), a lower level earthquake than the SSE.
If vibratory ground motion exceeding that of the 03E occurs,
shutdown of the reactor is requ red.
Prior to resu=ing opera-i tion, a licensee =ust demonstrate to the NRC that no functional _
damage has occurred to those features necessary for continued operation without undue risk to the health and safety of the public.
The 03E for the Troj an plant as defined in 52. 5. 2 of the Final Safety Analysis Report is 0.15g and is not in controversy in this proceeding.
. 6.
The OBE for the Trojan Plant controlled the actual design, rather than the SSE, although effective peak ground accelerations were designated as 0.15g and 0.25g, respectively.
Because three percent greater structural damping is permitted for the SSE than for the OBE, calculated earthquake loadings would be essentially the same except for different load factors imposed in the FSAR.
When these factors are used, 1.4 for the OBE and 1.0 for the SSE, the greater factored load from the OBE imposes the more stringent design requirements (Staff Exh.
5, Footnote 2, pp. 3-4; PGE Exh. 10, pp. 20-22; Tr. 858, 1442-3).
C.
Design Deficiencies in the Control Building 7.
In April 1978, while the Plant was' shut down for refueling, an investigation by the Bechtel engineers of the feasibility of cutting an opening and installing a security window in a wall of the Control Building disclosed a deficiency in the original design (?GE Exh. 10, pp. 4-5).
By letter dated April 28, 1978, the Licensees inforced the Nuclear Regulatory Cocmission's Office of Inspection and Enforcement and the Office of Nuclear Reactor Regulation that design errors existed with respect to the walls of the Control Building and that these walls did not conform to the cesign criteria set forth in the Final Safety Analysis Report for the facility
(?GE Exh. 13, p. 2).
11 -
8.
The nonconformances with criteria, identified as design deficiencies, fall into two major categories.
- First, both the horizontal and vertical reinforcing steel embedded in the inner concrete core of the Control Building shear walls is generally discontinuous, in that it is not anchored to the steel beans and colunns of the Control Building's steel frame (Staff Exh. 5, p. 2; PGE Exh. 10, p. 5).
Under the applicable codes and standards with which the Control Building must comply, steel reinforcement must be adequately anchored by bonds, hooks or mechanical anchors, or otherwise be anchored by being welded to or run through the steel beams and columns.
The construction drawing details used to place the steel in_the walls during construction failed to show the proper anchorage wherever the steel frame intersected the steel reinforcement (Staff Exh. 5,
- p. 3).
9.
The second design deficiency resulted from misapplica-tion of ACI 318-63 shear design for=ulae in combinatien with the applicable liniting OBE seismic loading, which resulted in less than the required amounts of reinforcing steel in the shear walls.
The effect of these errors was to credit the concrete shear capacity at about 2.5 times what it should have been under the applicable design criteria.
This resulted in too little steel reinforcement specified for the Control Build-ing walls to comply with ACI 318-63 (Staff Exh. 5, pp. 3-5; PGE Exh. 10, p. 6).
10.
As a result of these design deficiencies, the capacity of the Building Complex together with the contained systems and components to withstand seismic events is lower than intended.
The reduction in the seismic capacity due to the design deficiencies has been estimated to range from about 30% to about 50% (Tr. 574-5, 978, 1583, 2128-29, 2183, 2291-92).
The first step in considering either restoration of the seismic capability of the Building Complex to the original design intended, or operation of the Troj an facility during the interim period, requires reevaluation of the capability of the Building Complex to withstand seismic forces or loadings in the as-built condi-tion.
D.
Seismic Design and Reevaluation of the Building Cocolex 1.
Original Evaluations and Analvses, 1970-71 11.
The original seismic evaluation of the Control Building used a fixed-base, beam-stick model.
The analysis applied to the Control, Auxiliary and Fuel Buildings, but the Auxiliary Building was considered to have ao lateral resistanca except for a few walls.
The mass considered in the analysis was based on the design dead weight and 50% of the specified ticor live load.
The stiffness of the structure was based on uncracked section properties.
The =odal analysis spectrum responses technique was used for the determination of inertia
.. loads.
The modal responses were combined using the Absolute Sum Value technique (PGE Exh. 6, Attachment 1).
2.
Reevaluation Methods and Assunctions a.
Four Analvtical Studies of Seismic Cacability 12.
Since the original evaluations and analyses were made, and since the discovery of the design deficiencies, four additional separate seismic analyses have been performed on the Troj an Building Complex.
They are:
(1) a reevaluation of the original spectral response analysis in April 1973, using the fixed-base, beam stick model, esti=ated as-built weights,
and the application of the Square Root of the Sum of the Squares method to combine the contributions of the-building response modes (PGE Exh. 6, pp. 1-7) ; (2) an analysis by an independent consultant utiliting the TA3S program in June 1978 (PGE Exh. 3, pp. A-4, A-5), (3) an analysis using a three dimensional finite element model and the STARDYNE program with flexible base to account for the effect of rocking due to the foundation flexibility, in August 1973 (?GE Exh. 3), and (4) an analysis using the same model as in (3) and the STARDYNE program with fixed-base essuming no flexibility in the foundation of the 3uildings, in August 1978 (PGE Exh. 3).
b.
Assumotions Different from Critinal Analvses 13.
'Jith the specified SSE of 0.25g and the specified OBE of 0.15g in mind, the reevaluations of the lateral seismic resistance of the Building Complex were under-taken to determine more realistic seismic loadings and to calculate the shear capacities of the individual walls using the as-built structure with the following significant changes in assumptions:
(1)
The concrete strength for the Building Complex shear walls was 6,000 psi based on cylinder test results for the concrete actually used in the Control Building, rather than the value of 5,000 psi specified in the FSAR (PGE Exh. 6, ).
(2)
The mini =um yield strength for the reinforcing steel was 45,000 psi based on the mill test certificates for the actual material furnished and used in construction, rathei than the 40,000 psi specified in the FSAR (PGE Exh. 6, ).
(3)
The actual weigh;: of the Control Building and the equipment it houses was used based on a review of the as-built conditions, rather than the design dead weight and 507, of the specified floor live load (PGE Exh. 6, ).
(4)
The capability of some interior walls in the Auxiliary Building was considered in the reevaluation studies as reducing the amount of shear force transferred from the Auxiliary Building to the Control Building (PGE Exh.
6, ).
(5)
The contributions of the building response modes were combined by the Square Root of the Sen of the Squares method rather than the Absolute Sum Value technique (PGE Exh. 6, ).
c.
Procedure of Su= ming Wall Cacacities 14.
The procedure of sc= ming individual wall capacities to determine the resistance of a given wall system to the lateral loads parallel to their direction differs from the normal procedure followed in the reinforced concrete shear wall design process.
In the rormal procedure, the total loads resulting f cm a linear elastic seismic analysis would be proportioned to each wall according to its relative stiffness.
Each wall would then be designed to have the ACI 313 Code Ultimate Strength capacity to resist the proportioned load.
While this does not guarantee that each wall will reach its capacity at the same deflection, the procedure has been founc to be conservative (Staff Exh.
5, p. 11).
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17 -
new criteria for evaluating the fully grouted hollow concrete block walls of the Building Complex, was based on two sets of test data considered applicable.
Bases for the criteria were<
an empirical relationship derived by Schneider from tests of
=asonry wr.lls he conducted at California Polytechnic College, Pomona, and the results of subsequent shear-wall tests at the University of California, Berkeley (PGE Exh. 8, Appendix 3, pp. 2, 3, 4).
The new criteria obtained by Bechtel engineers are referred to as Modified Schneider Criteria.
Cyclic degradation was included in the Criteria by comparison with cyclic tests.
The composite strength is higher in all of the walls at Troj an than the strength of the blocks used in the Berkeley and Schneider tests.
In additien, comparisons to Portland Cement Association's (PCA's) reinforced concrete shear walls tests, with transverse members at both ends acting as flanges, confir=ed that the Modified Schneider Criteria results were conservative as applied to walls of the Building Complex (PGE Exh. 8, Appendix 3, pp. 5, 6).
18.
The Modified Schneider Criteria correlate very well with both the Schneider and 3erkeley tests in terms of resistance capacity.
All test specimens had vertical restraint that prevenced failure by bending, but per=itted failure by shear or lateral displacement.
In general, bending failures of a structure are prevented by constraints due to separation into stories or by the application of fixed or dead loads.
The Trojan Building Complex satisfies both of these conditions.
The major walls have significant dead load or can mobilize it by small movements that would lead to transfer of load from the steel columns to the shear walls.
Floor diaphragms provide further bending constraints.
Thus the conditions on which Modified Schneider Criteria are predicated are satisfied in the Control Building Complex (Tr. 594-7, 837-9).
19.
In the Building Complex shear walls, the masonry blocks that sandwich a concrete core have about one-half of their volume filled with concrete grout.
Thus, for a typical wall, appreciably less than one-half is masonry and the remainder is concrete.
Both the Berkeley masonry tests and the PCA reinforced concrete tests had shear strains in about the szne range when the maxi =un capacities were achieved.
Consequently, the Bechtel engineers concluded that the calcula-tion of shear capacities of composite walls, based on masonry strength values for both materials, was reasonable (PGE Exh. 8, Appendix C).
20.
From the experimental supporting evidence described above and the development of the Modified Schneider Criteria, the 3echtel engineers recalculated all shear wall capacities for the Building Complex.
Although the resulting shear wall capacities for use with the STARDYNE analysis were higher than those used with the Stick Model, the 3echtel engineers concluded that these were both realistic and still conservative for use with the more sophisticated finite element analysis techniques.
3.
Reevaluation Using the Stick Model 21.
The beam-stick codel employed in the original analysis and in the initial reevaluation study consists of lu= ped masses, sticks, and beams.
In this model, all the mass associated with each of the ficors in the Control Building, the Auxiliary Building, the Hold-up Tank enclosure structure, and the Fuel Pool is lu= ped into one concentrated mass.
These concentrated masses are interconnected by vertical sticks and horizontal bea=s representing the stiffness characteristics of the walls and floors, respectively (PGE Exh. 10, pp. 14-15).
22.
The initial reevaluation using the Stick Model was completed by 3echtel engineers with the assu=ptions listed in Paragraph 15 above.
Use of the recalculated loads resulted in a 13". reduction from the original design loads (later reevaluated as an 8" reduction for the STARDYNE analysis).
Cccpared to the original Stick Model analysis, the total recalculated base shears for the critical North-South direction SSE were raduced abcut 30". for both the Control Building and the Fuel Building.
The actual shear capacity of the walls
f
. with the new assumptions increased by 10'. over that of the original design value.
The comparison of these predicted loads with calculated capacities of the shear walls of the Building Complex led Bechtel engineers to conclude that the ground motion associated with the SSE was acceptable.
However, the OBE criterion as specified in the FSAR was not met, but rather an effective OBE of 0.llg ground acceleration appeared to be appropriate based ou the recalculation (PGE Exh. 6, Attachment 3).
23.
As part of the reevaluation study, the Control Building structure was also examined by completely disregarding the concrete shear strength and considering only the resistance of the reinforcing steel and the embedded steel columns.
This analysis was done to provide additional confidence as to the adequacy of the Control Building, although the technique is not normally required or performed in typical seismic design for buildings (PGE Exh. 10, p. 12; Staff Exh. 5, pp. 14-15, 27).
This evaluation demonstrated that the structure had a minimum shear resistance capacity approximately 1.4 times the required SSE capacity at a given elevation, giving further confidence in the capability of the structure to resist SSE loadings (PGE Exh. 10, pp. 12-13).
4 Indecendent Evaluatien Usinz the TA3S Prceram 24 The second reevaluation of the seismic capability of the Building Structure was performed using the TA3S Program