ML20205T561
| ML20205T561 | |
| Person / Time | |
|---|---|
| Site: | Millstone  |
| Issue date: | 06/11/1986 |
| From: | Carfagno S, Con V, Stilwell T CALSPAN CORP. |
| To: | NRC |
| Shared Package | |
| ML20205T565 | List: |
| References | |
| CON-NRC-03-81-130, CON-NRC-3-81-130, TASK-03-07.B, TASK-3-7.B, TASK-RR TER-C5506-436, NUDOCS 8606160051 | |
| Download: ML20205T561 (57) | |
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FRANKLIN RESEARCH CENTER DIVISION OF ARVIN/CALSPAN REVIEW OF LICE l1SEE RESPO!!SES TO SEP TOPIC II -7.B.
DESIGM CODES, DESIGN CRITERIA, A!;D LOADIt1G COMDIt3ATIOtiS 13ORTilEAST NUCLEAR EttERGY COMPA!!Y MILLSTot!E tiUCLEAR POWER STATIO!! UNIT 1 TER-C5506-436 TECHNICAL REPORT l*
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SUPPLEMENTARY l.
TECHNICAL EVALUATION REPORT k
NRC DOCKET NO. 50-245 PgG PROJEC/i C6606 N RC TAC NO. --
PE:AS$1GNMENi 10 NRC CONTRACT NO. NRC OH1130 PRC TASK 436
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REVIEW OF LICENSEE RESPONSES TO SEP TOPIC III-7.B, DESIGN CODES, DESIGN CRITERIA, '
AND LOADING COMBINATIONS, NORTHEAST NUCLEAR ENERGY COfEMANY MILLSTONE NUCLIAR POWER STATION 17 NIT 1 TER-C5506-436 y
Prepared for 5
Nuclear Regulatory Commletion FRO Qroup Leader:
T. Stilwell Wr.shington, o.C. 20$$$
NRC Land Engineer:
t'. Y. Chen n
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This report was prepared as an account cf werk eponsored by en agency of the Unite:1 States Government. Neither the United Sintes Government nor any agency thereof, or any of their employees, makes any warranty, empressed or implied, or soeumes any hyn; liability or responelbility for any third party a use, of the f6sulte of such use, of anyinf)nmetion, appa.
refue, product or procese disclosed in thle report, or represents that its une by such third party would not infringe privately owned rights.
Prepared by:
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CONTENTS
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Section Title Pa y
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1 INTRODUCTION
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DESIGN CODE CHANGES DESIGNATED SCALE A.
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- 2. 3, Shear Connectors for Composite Beams 2
e' 2.2 ~ i*omposite Beans or Girders with Formed Steel Deck.
3 2.3 Flangc'Strass in Hybrid Girders 3
i 2.4 Stresses in Unstiffened Compression Elements 4
2.5 Maximm Loed in Riveted or Bolted Tensile.,Nembers.
4 2.6 Shear Load in Coped Beams.
6 2.7 Column Web Stiffeners at Frame Joints.
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.8 Lateral Support Spacing in Frames.
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2.9 Brack.ets and Cerbels 2.10 Special Prod sion for Walls 8
2.11 Elements Loaded in Shear with No Diagonal Tension.
9 2.12 Elements Subject to Temperature Variations.
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2.13 Columns with Splitad' Reinforcing 10 2.14 Embedmonts.
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2.15 Ductile Respo;se to Impulse Loads.
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'l 2.16 Tangentiel Shear (Containments) 11 2.17AreasIfCon6.ainmentShellSubjecttoPeripheralShear.
12 2.18 Areas of Containment Shell Subject to Torsion.
12 2.19 Thermal Loads.
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2.20 Areas of Containment S' hell Subject to Biaxial Tension.
13 2.21 Brackets and Corbels (On the Containment'Shell) 13 f
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3 CONTENTS (Cont.)
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3 REVIEN METHOD AND TABULAR PRESENTATIONS.
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TABULAR SIMIARY OF FIND 1'AGS OF LICENSEE COMPLIANCE STATUS CONCERNING IMPLEMENTATION OF SEP TOPIC III-7.B 16 IMPACT OF DESIGN CODE CHANGE 3.-
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5 LOADS AND LOAD COMBINATIONS 29 6
SUMMARY
OF REVIEN FINDINGS.
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CONCLUSIONS AND RECOMMENDATIONS.
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TER-C5506-436 FOREWORD
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This Technical Evaluation Report was prepared by Franklin Research Cente:
under a. contract with the U.S. Nuclear Regulatory Commission (Office of Nuclear Reactor Regulation, Division of Operating Reactors) for technical assistance in support of NRC operating reactor licensing actions. The technical evaluation was conducted in accordance with criteria established by 1
the NRC.
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INTRODUCTION j
Current design criteria for nuclear power plant structures contain requirements that were not in effect when older plants were designed and licensed. Conseguently, one aspect (designated Topic III-7.B) of the implementation of NRC's Systematic Evaluation Program reguires licensees to review changes that have occurred in structural design criteria since their plant was built and also to review the loads and load combinations used for design of plant structures by comparing them with the loads and load combinations now specified for current construction. The licensee's objective is to assess the impact that these changes may have on margins of safety of Seismic Category I structures as they were originally perceived and as they would be perceived under current criteria. Upon completion of thia work, 1
licensees report their findings to the NRC.
l' To assist in this review, the NRC provided licensees with plant-specific Technical Evaluation Reports (TERs) concerning these issues (e.g., Reference "O
1).
The TERs listed design code changes and, on a building-by-building basis,-
the load and loading combination changes to be addressed in the licensee i
review. The items listed were ones judged to have the greatest potential to degrade the originally perceived margins of safet*f.
In May 1983, unde contract NRC-03-81-130, the NRC retained the Franklin Research Center (FRC) to assist in its review of licensee findings. The s
present report (Supplementary TER-C5506-436) describes the review for the Millstone Nuclear Power Station Unit 1 and summarizes Northeast Nuclear Energy Company's (NNECo) compliance status with respect to the implementation of SEP Topic III-7.B.
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TER-C5506-436 2.
DESIGN CODE CHANGES DESIGNATED SCALE A Current structural design codes contain provisions that differ from, or did not appear in, the codes to which older plants were designed and con-structed. Changes that were judged to have the potential to significantly affect perceived margins of safety have been designated as Scale A.
For reference, changes in ACI-63 and AIiiC-63 designated Scale A are briefly discussed in this section of the report. Although all such changes were considered in the Topic III-7.B assessment of all plants constructed to these codes, not all appear among the issues the Licensee was requested to address. On a plant-specific basis, some were eliminated as not applicable to the type of construction employed. When this was done, the eliminated code changes were listed (together with the reason they were considered inapplica-ble) in Appendix A of Reference 1, and the Licensee was requested to confirm the validity of Appendix A.
2.1 SHEAR CONNECTORS FOR COMPOSITE BEAMS Four major modifications to the 1963 AISC Code (2) related to the type, distribution, and spacing of shear c'onnectors for composite beams occur in the 1980 Code [3]. These modifications are:
a.
Permission to use lightweight structural concrete (concrete made with C330 aggregates) in composite designs b.
Allowance of design for composite action in the negative moment
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region of continuous beams and provision of design guidance for including the longitudinal reinforcing steel in the negative moment resisting section c.
Design requirements for the minimum number of shear connectors in regions of concentrated load d.
Maxinum and minimum spacing requirements in terms of stud diameters.
The first two modifications will not affect old designs because they were not
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allowed by the previous code. The new provisions *concerning the number of studs in the region near concentrated loads and the new limits concerning y
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i TER-C5506-436 spacing of studs may adversely affect the margin of safety in older designs when checked against the new code provisions. These new requirements are of 4
special concern in the case of composite beams subject to large concentrated loads, such as those associated with extreme environmental or critical accident conditions.
2.2 COMPOSITE BEAMS OR GIRDERS WITH FORMED STEEL DECK The 1980 AISC Code (3) contains a new section covering stay-in-place formed steel deck when used in a composite design. These provisions for formed steel decking, depending on the rib geometry and the direction of the ribs relative to the beam, may affect the load capacity of the shear studs and the effective flange width of the assumed concrete compression flange. They provide for reduction factors, to be applied to the shear stud allowable capacity, which account for the structural irregularity introduced iato the composite slab.
Composite beams with formed steel decks that were designed to the previous code could have less conservative margins of safety when compared to present requirements, especially in cases where extreme loadings are to be considered.
2.3 FLANGE STRESS IN HYBRID GIRDERS The AISC Code section covering reduction of bending stress in the compression flange was modified in the 1980 Code.
The original flange stress reduction formula in the old code was needed to account for stress transfer which may occur in ordinary beam webs if the compression region should deflect laterally, thereby changing the bending capacity of the cross section.
In hybrid girders, the amount of the loss of a
bending resistance resulting from this phenomenon wi*l vary depending on the relative properties of the web and flange steel. A reduced bending stress formula reflecting this interaction was introduced.
In order to keep the I
formulation relatively simple, the reduced bending stress was made applicable to both flanges of the hybrid member.
Where the ratio of web yield str2ss to flange yield stres's is less than 0.45 and the ratio of the web area to flange area is low, beams or girders
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febricated from plate where the flange and web steels are different could have lower margins of safety under the new code than were thought to exist under
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2.4 STRESSES IN UNSTIFFENED COMPRESSION ELEMENTS i
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New requirements provide stress reduction factors for unstiffened
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elements subject to compression with one edge - an edge parallel to the compressive stress - free.
Previous code provisions allowed the designer to neglect a portion of the area of such elements. The new code requirements provide equations for var-ious elements based on the critical buckling stress for plates. The new analytical approach is more conservative for the stems of tees and less conservative for all other cases.
Where structural tees are used as main members and the tee stem is in compression, the margin of safety for older designs (if checked under the new code) could be significantly less than was thought under prior code requirements. Since buckling is a non-ductile type failure, these new requirements are of special concern in the case of tee shapes subjected to the extreme environmental or critical accident conditions.
2.5 MAXIMUM LOAD IN RIVEIED OR BOLTED TENSILE MEMBERS The 1980 AISC Code [3] introduces codes changes which affect the maximum load permitted in tensile members.
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Two interacting code changes are involved in establishing this limit, and the mutual effects of both must be considered in assessing the impact of the new code upon the perception of margins of safety in tension members. The two l
provisions involved concern:
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the tensile area permitted to be used in establishing load carrying capacities 2.
the allowable stresses to be used in conjunction with these areas.
Both effects are taken into account in ranking this change. The potential magnitude of the mutual effects of the two changes is discussed below.
.s TER-C5506-436 Tne 1980 AISC Specification definition of " Effective Net Area" introduces b
a reduction coefficient which is to be applied to the traditional definition of not area. This essentially changes the design capacity of a tension memter when compared to older versions of these specifications. First consider only the effect of the critical area used for the design of a tension member as defined.in the new code compared to the critical areacused for the design of the same member as defined in the old code. Clearly # if all other factors are 3
equal, the new code is more conservative. However, all other factors are not the same. The changes in allowable tensile stress (on the gross area and on the effective net area), which were introduced simultaneously with the new definition of effective not area, modify the above conclusion.
In addition, the traditional upper limit on the critical net area:iof 85% of the gross area (a requirement of the old code) is no longer a requiesment of the new code.
Both of these changes interact with the new effectivrinet area requirement.
A valid assessment of the effect of these changes is best accomplished by acomparisonoftheallowableloadeachcodepermitsinjensionmembers.
If le J one considers the allowable load on the effective not area, the value based on 4
the new code is a function of three variables: the new reduction coefficient, the net area,* and the ultimate tensile strength of the steel. The allowable i
t load based on the old code is a function of only two variables:
the net area and the yield strength of the steel. First,formthe51oadratioofthe allowable load defined by the new code criteria to the allowable load defined by the old code criteria. Next, consider the ranges of all of the parameters mentioned above, this ratio will have defined upper and lower limits which are a function of the ratio of the not areas, the new code not area reduction factor, and the ratio of the steel ultimate strength to the yield strength.
For all the steels allowed under the new code, this load ratio ranges I
j from 1.5 to 0.69.
For all the steels allowed under the old code, this load l.
ratio ranges from 1.6 to 0.88.
It is apparent that, for those steels with reduced load ratios, the new code is less conservative than the old. The margin of safety of some older designs therefore could be significantly lower when checked against the new code requirements.
- In making this comparison, one must be careful to note that the net area is not always the same under the old and new codes.
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TER-C5506-436 2.6 SHEAR LOAD IN COPED BEAMS The 1980 AISC Code (3) introduces additional control over the shear load permitted at beam end connections where the top flange has been coped.
Web shear control in older codes did not distinguish between coped and uncoped beams or between shear allowed at connections and over the free span (except'for requiring reinforcement of thin webs at connections). The shear load allowed was given by:
allowable shear load = 0.4 (yield strength) (gross web section).
The 1980 Code retains this limit, but introduces an additional requirement to protect against a failure mode associated with coped beams.
For coped beams (and aimilar situations), a portion of the web may sever, failing along the perimeter of the connection holes.
In particular, coped beam web connections where the fastener holes lie close to the butt end of the beam may be prone to such failures.
This web " tear out" failure is actually a combir.ation of shear failure through the line of fasteners together with tensile failure across the shortest path to the beam end. The failure surface turns a corner with shear failure along a line trending upward through the holes, combined with tensile failure across a more or less horizontal line running out to the beam end.
The newly introduced shear limit is given as a function of the minimum not failure surface and the steel ultimate strength. Thus, the new requirements may or may not control a coped beam's allowable capacity in shear. Whether or not it does depends on both the connection geometry and the type of steel used.
When this requirement is controlling, coped beams designed by previous rules may be found, if checked against the new criteria, to have significantly smaller margins of safety than previously thought.
2.7 COLUMN WEB STIFFENERS AT FRAME JOINTS The more recent editions of the AISC code mandate which columns must be stiffened at locations where beams of girders are rigidly attached to the column flange and also establish requirements for the geometry'of such web l '
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stiffeners. These requirements are introduced to priclude local crippling at such frame joints.
No sisch epiirianca was provided by AISC-63 (2]. Older codes (such as AISC-63) left such matters to the designer's discretion. Consequently, there is no assurance that all such columns are adequately stiffened for current accident.and faulted loadings.
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2.8 IATERAL SUPPORT SPACING IN FRAMES (PLASTIC DESIS. METHOD)
The 1980 AISC Code contains changed spacing requirements for lateral supports in portions of members in frames where failursumechanisms are expected to form at ultimate load.
Members of such frames must not only be capable.of developing a plastic hinge, but must also be stable enough to sustain moments larger than those computed on an elastic-perfect-plastic theory (because real steels work-harden at strains expected to occur at hinge locations). Previous lateral bracing requirements were developed for a limited range of: steels'. Research on high-strength steels has shown that, for certain ranges of slenderness ratio of the compression flange of such frame members, older specification bracing requirements were not sufficiently conservative.
The new specification requirements make the slenderness ratio limits a function of the steel yield strength and the member curvature (as expressed by the ratio of the lesser bending moment at the endri of _the unbraced segment to the plastic moment).
The new specifications are more conservative for (13 any segment bent in double curvature regardless of its steel specification and (2) very high-strength steel members. The adequacy of frame.saembers bent in single curvature and constructed of steels whose yield strength exceeds 36 kai should i
be examined on a case-by-case basis.
The new requirements may reduce the margins' of safety thonght to exist in:
1.
structures designed under the plastic requirements of older codes 2.
elastica 11y designed structures sized to carry a smaller maximum load than is now required by current accident and faulted load l 1 I
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TER-C5506-436 combinations.
In this case, plastic logic may.have to be invoked to justify the adequacy of exisiting structures.. Nonconformance with current bracing requirements may substantially restrict the capability of frame members to carry code-acomptable overloads.
2.9 BRACIGTS AND CORBELS ACI 349-76 [4), Section 11.13 contains design requirements for short brackets and corbels which are considered primary load-carrying memberrs; no comparable requirements are provided in ACI 318-63 [5].
The requirements apply to brackets and corbels having a shear span-to-depth ratio of unity or less. They provide minimum and maximum limits on tension and thear reinforcement, limits on ultimate shear stress in concrete, and constraints on member geometry and location of reinforcement.
Brackets and corbels designed under earlier codes may or may not satisfy the newly imposed limits. If they do not, they may be prone to non-ductile failure (which occurs suddenly and without warning) and may exhibit smaller margins of safety than those currently required.
e 2.10 SPECIAL PROVISIONS FOR WALLS 2.10.1 Shear Walls ACI 349-76, Sections 11.15.1 through 11.15.6 specify requirements for reinforcing and permissible shear stresses for in-plane shear loads on walls.
The ACI 318-63 Code had no specific requirements for in-plane shear on shear walls.
2.10.2 Punchina Shear ACI 349-76, Section 11.15.7 specifies permissible punching shear stresses for walls. ACI 318-63 had no specific provisions for walls for these stresses. Punching loads are caused by relatively concentrated lateral loads U
on *he walls. These loads may be from pipe supports, agsipment supports, duct supports, conduit supports, or any other component producing a lateral load on a wall.
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TER-C5506-436 2.11 ELEMENTS LOADED IN SHEAR WITH NO DIAGONAL TENSICN;(SHEAR FRICTION)
The provisions for shear friction given in ACI 349-76 did not exist in ACI 318-63. These provisions specify reinforcing and stress requirements fo-situations where it is inappropriate to consider shear as a measure of diagonal tension.
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2.12 ELIMENTS SUBJECT TO TEMPERATURE VARIATIONS The ACI 349-76, Appendix A requirements for thermal considerations in nuclear safety-related, reinforced concrete strucutres do not have a comparable counterpart in ACI 318-63.
I The new provisions give guidance in the form of general design require-ments and limiting concrete temperatures. New design \\ provisions require that the effects of temperature gradients and the effects af the difference between mean temperature and base temperature during normal operation of accident conditions be considered. Also, thermal stresses.are to be evaluated l
considering the stiffness and rigidity of members and the degree of restraint of the structures. Concrete temperature limits are specified, both for normal operation or other long-term periods and for accident or other short-term periods. In addition, special temperature limits are'provided for localized conditions such as around penetrations and from steam or water jets that might 4
strike concrete structures as a result of postulated pipe breaks.
All requirements of the older codes are a result of experience and research with reinforced concrete at temperatures primarily related to normal weather conditions. Consequently, the older codes did not reflect major effects of high-temperature exposures.
Research into the effects of temperature on mechanical properties of concrete reveals that generally both strength and stiffness degrade significantly with high temperature beginning at about 120* to 150*F.
Both properties are reduced as a result of a combination of mechanisms. Above these temperatures, microcracking (which results from differential exp'nsion a
of aggregate and the cement paste matrix) and paste dehydration are significant contributors to loss of strength and stiffness.
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TER-C5506-436 The new requirements may reduce the margins of safety previously thought to exist in older designs if the newly specified general design requirements 4
were not given appropriate consideration or if current temperature limits are exceeded. In addition, the new code provides specific guidance for thermal stress analysis in cases where thermal gradients exist and defines (in the commentary to Appendix A) three acceptable approaches to the analysis.
It is possible that the structural analysis of some plants designed to earlier codes may not have fully taken into account stresses from thermal loadings. Where this is true, the computed margins of safety may overstate the actual structural integrity.
2.13 COLUMNS WITH SPLICED REINFORCING The ACI 349-76, Section 7.10.3 requirements for columns with spliced reinforcing did not exist in the ACI 318-63 Code. The ACI 349-76 Code requires that splices in each face of a column, where the design load stress in the longitudinal bars varies from f in compression to 1/2 f in tension, be developed to provide at least twice the calculated tension in that face of the column (splices in combination with unspliced bars.can provide this if applicable). This code change requires that a minimum of 1/4 of the yield capacity of the bars in each face of the column be developed by both spliced and unspliced bars in that face of the column.
2.14 EMBEDMENTS Appendix B of ACI 349-80 provides rules for the design of steel embedmonts in concrete; the design of embedmonts is not specifically addressed in ACI 318-63.
Current requirements of Appendix B are based upon ultimate strength design using factored loads. The anchorage design is controlled by the ultLante strength of the embedment steel. Ductile failure (i.e., steel yields before concrete fails) is postulated.
Under the provisions of ACI 318-63, the design of embedments was left to the discretion of the designer. Working stress design methods were widely used.
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TER-C5506-436 Consequently, it is likely that original embedmont designs do not fully conform to current criteria. Review of such designs to determine the implications with respect to margins of safety is therefore judged a desirabl rrecaution.
2.15 DUCTILE RESPONSE TO IMPULSE LOADS I
Appendix C to ACI 349-76 [4] contains design rules for structures which may be subjected to impulse or impact loads; no such provisions occur in ACI-318-63 (5].
The rules of Appendix C are intended to foster ductile response (i.e.,
steel yields prior to concrete failure) of nuclear structures if and when they experience impulse or impact Icads. For structures built to codes not containing such provisions, there is no assurance tnat sufficient design effort was directed toward proportioning members to provide energy absorbtion capability. Consequently, such structures might be prone to non-ductile, sudden failure should they ever experience postulated accident loadings such as jet impingement, pipe whip, compartment depressurization, or tornado missiles.
2.16 TANGENTIAL SHEAR (CONTAINMENTS)
Paragraph CC-3421.5, Tangential Shear, of Section III, Division 2 of the ASME Boiler and Pressure Vessel Code (6) addresses the capacity of reinforced concrete containments to carry horizontal shear load.
It provides code-acceptable levels of horizontal shear stress that the designer may credit to the concrete. No specific guidance in this matter exists in ACI 318-63.
The provisions associate the allowable concrete stress in horizontal shear with the concrete properties, the menner in which lateral loads are imposed on the structure, and the presence of sufficient reinforcement to assure that the assumed shear capacity of concrete can be developed.
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Sufficient diagonal reinforcement (or its demonstrated equivalent) is to be supplied to carry, without excessive strain, shear in excess of that permitted in the concrete. A major consideration here is the preservation of the structural integrity of the liner.
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In containmentt constructed to older codes, such matters were left to the discretion of the designer, who may or may not have provided the horizontal shear capacity at controlled strains that the code currently requires.
2.17 AFEAS OF CONTAINM2NT SHELL SUBJECT TO PERIPHERAL SHEAR Concrete containment design is currently governed by the ASME Boiler and Pressure '.'assel Code,Section III, Division 2, 1980 [6]. The provisions for peripheral (punching) shear appear in code Section CC-3421.6. These provisions are similar to the ACI 318-63 Code (5) provisions for slabs and footings, except that the allowable punching shear stress in CC-3421.6 ir.cludes the effect of shell membrane stresses. For membrane tension, the allowable concrete punching shear stress in the ASME Code is less than that allowed by ACI 318-63.
4 2.18 AREAS OF CONTAINMENT SHELL SUBJECT TO TORSION Concrete containment design is currently governed by the ASME Boiler and Pressure Vessel Code,Section III, Division 2, 1980. Section CC-3421.7 of the-code contains provisions for the allowable torsional shear stress in the concrete. Such provisions were not contained in the ACI 318-63 Code. The present allowable torsional shear stress includes the effects of the membrane 4
stresses in the containment shell and is based on a criterion that limits the principal membrane tension stress in the concrete.
2.19 THERMAL LOADS
- t ACI 349-76 Appendix A and ASME B&PV Code,Section III, Div. 2, CC-3440 l
contains requirements for consideration of temperature variations in concrete i
that are not contained in ACI 318-63.
The new provisions require consideration of the effects of thermal gradients and of the effects depending on the mean temperature di,stribution and the base temperature distribution during normal operation or accident conditions. The new provisions also require that thermal stresses be eval-usted considering the stiffness and rigidity of members and the degree of restraint of the structure.,__
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s TER <5506-436 An assessment is to be made of the analytical methods used to determine-thermal stresses as compared to current code-acceptable practices, e.g., thore discussed in ACI 349.1R-80 and the connentary to ACI 349R-80.
If the methods used for design produce stress results which are signifi-cantly different from those current procedures generate, perceived margins of safety could be affected.
2.20 AREAS OF CONTAINMENT SHELL SUBJECT TO BIAXIAL TENSION Increased tensile development lengths are required by Section CC-3532.1.2 of Reference 6 for reinforcing steel bars terminated in areas of reinforced concrete containment structures which may experience biaxial tension. For biaxial tension loading, bar development lengths, including both straight embedmont langths and equivalent straight length for standard hooks, are required to be increased by 25% over the standard development lengths required for uniaxial loading. Nominal tem'perature reinforcement is excluded from these special provisions. ACI 318-63 had no requirements related to this increase in development length.
2.21 BRACKEIS AND CORBELS (ON THE CONTAINMENT SHELL) e The ACI 318-63 Code did not specify requirements fior brackets and corbels. Provisions for these components are included in the ASME Boiler and Pressure Vessel Code,Section III, Division 2, Section CC-3421.8. These f
provisions apply to brackets and corbels having a shear-span-to-depth ratio of unity or less. The provisions specify minimum and maximum limits for tension I
and shear reinforcing, limits on shear stresses, and constraints on the member geometry and placement of reinforcing within the member.
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REVIEW METHOD AND TABUIAR PRESENTATIONS 3.1 REVIEW DOCUMENTS The information relating to SEP Topic III-7.B which was supplied to the NBC by Northeast Nuclear Energy Company and made available for this review is contained in the following documents:
1.
W. G. Counsil and R. W. Bishop, Northeast Utilities Letter to D. M. Crutchfield, Chief, Operating Reactor Branch No. 5, USNRC
Subject:
Millstone Nuclear Power Station, Unit No. 1, SEP Topic III-3.B, Flooding Potential and Protection Requirements; SEP Topic II-2, Wind and Tornado I4adings: SEP Topic III-3.A, Effects of High Water Level on Structures; SEP Topic III-7.B, Design Codes, Design Criteria, and Load Combinations Docket No. 50-145 February 2, 1984 2.
No'etheast Utilities Service Company Report Prepared by Impell Corp.
Subject:
" Millstone Unit 1 Reevaluation of Plant Structures to Address Structural Issue Raised Under SEP Topics II-3.B, III-2 and III-3.A" Janauary 1984 3.
Northeast Utilities Service Company Report Prepared by Impell Corp.
Subject:
. Millstone Unit 1 Reevaluation of Plant Structures to Address Structural Issue Raised Under SEP Topics III-7.B" December 1983 3.2 REVIEW PRESENTATION Before undertaking licensee report reviews, FRC prepared tabular forms to be used as a working tool during the review process and also to document the review work and its findings.
These tables are intended to:
1.
establish a systematic and comprehensive review procedure 2.
standardise, as much as possible, the review process for all licensees 3.
present a relatively compact overview of each licensee's SEP Topic III-7.B compliance status.
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TER-C5506-436 4
The form sheets summarize key information reported in licensee 2
responses. Certain items (such as descriptions of Scale A code changes, conclusions, and comments) frequently are not adaptable to abbreviated summary. For such items, the form sheets refer the reader either to sections of this TER where the matter is developed more fully or to an extended note list compiled on separate sheets. The note list, although detached from the main table in order to allow a fuller discussion, should be regarded as an integral part of it.
l The form sheet consists of four major columnar sections which:
1.
identify each Scale A item j
2.
state the action that the licensee took or the logic that the licensee presented to resolve the item 3.
provide an assessment of engineering conclusions that may be reasonably drawn from the evidence provided 4.
summarize the licensee's compliance status with respect to the item.
I'tems listed on the tables are design code changes designated Scale A.
This list is drawn directly from TER-C5257-323, the previous Technical Evaluation Report on this topic (1].
Form sheets summarizing the review findings concerning the licensee's compliance status with respect to the implementation of SEP Topic III-7.B aspects related to design code changes follow in Section 4.
A discussion of the review findings concerning the licensee's compliance status with respect I
to load and load combination changes is presented in Section 5.
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TER-C5506-436 4.
TABULAR
SUMMARY
OF REVIEW FINDINGS OF LICENSEE COMPLIANCE STATUS CONCERNING IMPLEMENTATION OF SEP TOPIC III-7.B IMPACT OF DESIGN CODE CHANGES Form sheets sumunarizing the review findings concerning technical aspects with respect to the implementation of SEP Topic III-7.B as related to design code changes follow.
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PL Asti: Millstone h it 1 Suett2V OF LICENSEE CgetIAIKE STATU$ -
SipUCIUpt : All Selsmic Category I IMPACT Of DESIGN Coet CMmesGE5 Steel Structures Sheet I of 5 COM CNAf0GT CITED A$ $CALE A tlCfM5ft'$ ACiless to ef 50tVE teLILil-ts2st-323 POIENLIALCnurraN
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tlCEll5ELSIATV5 15 $Uf flCitNI ettfatNCte Costs etsCatelloN Or I$ MIMOD EVIDEIICE STATUS WIIM
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t.9.1.2 1.9.9 Compresslea Befs. 7 3-1 Check sample members Yes
$ efficient C-1 Open Belate test and elements having and d-1 where b/t ratio is evidence samples to Appeadle b/t ratie greater 8 3
esteeded may have osage plaat-wide
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than specified been de-la 1990 Code veloped but et is (2.49 not se documented I
1.l4.2.2 feaslea members Refs. F 3-2 Connectlens for A-36 Ves Yes C-2 Resolved Issae M
where lead is and d-2 steel members (the major 4
transmitted by 8
9 maternal of plant I
belts er rivets constructioni were v
(2.5) cherned I.5.1.2.2 Ceped beam Refs. #
3-2 team slees taema to have tee.
No C-3 Open Apply me=neum ceanectieas whea and d-1 beca ceped were checked Actual service shear subject to shear 8 12 assuming both ceanectier ' leads leads to beams details and the lead should (from AI5C entfore lead be used tables) 3.15.5.2 Column web pets. F 3-3 erawinys were reviewed Yes Yet Adequate sesolved steae theengh stiffeners and d-3
. for this type of stiffness I.15.5.4 for sement constrectlen. Where is provided carrying er 8
23 losad, st6ffeaers Cd restralmed end mere checked to require-connections ments (2.F) 2.9 2.9 Spaclay of Refs. 7 3-3 Drawlays were chected Yes Yes Plastic Resolved 88 ear I
lateras supports and 4-3 for evidence of plastic design ta meshers de-design methods methads aet e-I signed to plas.
8 28 esed C-5 tics analys6s 6
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ACI 349-76 ACI 318-63 15.13 Short brarbets Refs. 7 3-3 A sample bracket with Yes Yes Orac ket tessived peone and cerhels and 4-4 a/d ration t I esos chected
[ Reviewers found
$2.9) 8 29 under other reassessment assume the adequate programs is cited one bracLet C-6 checked was a worst case theite]
38.55 Shear walls Refs. 7 3-4 Old and current shear Yes Yes C-7 8esolved scene f
used as primary and 4-4 provistoms for walls were lead carrying 8
34 analytically compared members II.14 Elements leaded Refs. 7 3-4 Precast elements were this Yes Galy pre-Sesolved scene la shear where and 4-5 checked to current responds cast elements it is inappre-S 42 criteria to issue thatchesi as raised are code priate to con-acceptable steer shear as (C-al a measure of diagonal tension Append 6s Concrete reglens Bef. 7 3-5 Enge are of concrete at Yes Yes Concrete tesolved scene A
subject to high and 4-6 M651stene I to code limit will meet temperatures and S 46 thermal conditions was current transients (2.921 checked thermal l6mitations (C-91 i
l 7.88.3 805 Columns with Ref. 7 3-6 The fatigue envireament Me No C-It Open test coluna N
spliced rein-and 4-7 of celemas discussed moder most h
severe moment forcement subject 8 49 reversal a
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IMPACT OF DESI(d8 000E CMaNisE5 Concrete Structures i
Sheet 4 et 5 i
i Cast CnanEE CBIES a5 5Catt a iICEas5EE'S attlem to RE50tWE tm Ita rou-123 rg![ggiat raurram tuntiasII M Af LICERI5EE*5 aflim terra car uatan 15 Suff8CIENI MffsteICES CenE5 BESCRIPiless GF 15 satisme EVIM NCE 5tates$ ItifM i
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NE-3122.4 5 23 Wessel meterial Defs. 7 3-7 ge411stene vessel Yes Yes staterials tesolved Itsee acceptab616ty and 4-12 meterials were checked are code 9
2 vs 1980 code acceptable (C-13) 5 25(d) Ipse of telltale Sefs. 7 3-e Bees not apply sesolved mene g
holes and 4-12 at IO411stene i
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est-3931 Eleitation en Refs. 7 3-e Seesegment analytical Ves Yes Intent of Resolved Insee vessel design by and 4-12 reviews of origleal IIE 3131 is formulae 9
4 destga to formula met (C-15) seE-1938.5 WG-29 Stiffentag rises sets. 7 3-9 Centalasset stiffenlag Yes Yes e6nes are Besolved lamas en shells subject and 4-13 clags were chected adeguately to esternal 9
5 stiffened pressere per current requirements I
NE-3933.5(b) -
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, Check ring and shell Yes Yes testerials Sesolved Itene
. i et mater 6als and 4-14 materials are the I
etter than esed 9 5
same (C-17)
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..e TER-C5506-436 NOTES:
1 In the following notes, the Licensee's conclusion is presented first, followed by the reviewer's comments, if any, in brackets.
C-1.
The review of all 1963 AISC manual standard shapes showed that all I-shape and channel sections satisfy present AISC code require-i monts, but some standard angle sections and the majority of standard teos, do not.
Angle section members at Millstone Unit 1 are deemed to be adequate.
Because the webs of most standard tee sections do not satisfy 1980 i
limits, and a number require significant stress reductions, a i
sampling of specific cases at the Millstone plant was evaltated.
only one case was noted where the web b/t violated the 1980 code limit. Since this violation occurred in members used as stiffeners i
for a manhole pit cover, it was concluded that the applications of tee sections at Millstone Unit 1 are acceptable for this code change.
(The reviewers deem evidence from a sampling approach a reasonable engineering basis for making plant-wide projections provided the sample selected is representative of all applications.
i l
The Licensee checked a sample of the applications in which toes are used at Millstone Unit 1.
However, no description is given of the sampling procedure, of the sample basis, and of how comprehensive l
it was relative to all structural employments (of any kind) throughout the plant.
The assurance sought in Topic III-7.B is that tee shapes are i
nowhere used in critical applications in Millstone Unit 1 (or at i
least, that it is unlikely that they are so used) or, if used, that they do not degrade safety margins.
This assurance is implied in the response, but it is not quantified 4
in a way that permits safety judgments to be made.)
l C-2.
The reevaluation approach for this item was to compare AISC 1963 to f
AISC 1980 code provisions for calculating acceptable tension stresses in structural steel members.
4 The tension allowable stress was changed from 0.6 F to 0.5 F e y
u which for the A36 steel members at Millstone Unit 1 meant a 34%
increase in allowable.
When the counterbalancing effect of only the increase in allowable was set against the decrease in area, it was found that axially I
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1 TER-C5506-436 loaded tension members designed to 1963 code criteria are acceptable for the new 1980 code guidelines.
(The reviewers agree that members constructed of A36 steels are nct adversely affected by the code change.]
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-i C-3.
Evaluation of this code change item required analyzing a sampling 7: '
of Millstone Unit 1 beam connections assuming standard AISC friction connections with A325 high strength bolts. Also, the AISC maximum uniform load tables were used to obtain upper bound shear g
reaction values for the beams.
Based on the ca'1culations performed for the sampling of
)
connections, it has been determined that all of the bolted or C
riveted beam connections at Millstone Unit 1 where the top flange is coped are adequate for the new 1980 AISC code provisions.
[Except for identification of beams which were coped in Millstone structures, the analysis makes little reference to actual applications in service. Connection details and beam shear loads are both assumed. Given the paucity of information on connection details, it is not unreasonable to assume that a standard connection detail was used. However, the shear loads on the connection should be taken from computations of the most severe loadings. imposed on the beam in actual service.)
C-4.
The review of Millstone Unit 1 Category I structural steel drawings indicated that only two areas of moment resisting beam to I-shape column connections exist. Since all of the connections in these two areas were fully stiffened, only the size of the existing stiffeners needed to be evaluated in accordance with the 1980 code criteria. The evaluation of these stiffeners showed them to be of
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sufficient size.
C-5.
A review of the Category I structural steel drawings for Millstone Unit I was performed which indicated that there was very little use of moment-resisting connections in the structures. Since an i
extensive use of pinned connections provides very little of the redundancy necessary for plastic design, it is concluded that plastic analysis procedures were not used at Millstone Unit 1.
Therefore, this code change item does not affect this plant.
1k (This seems a reasonable inference. However, if plastic logic is subsequently used to justify member integrity under severe loadings, the impact of this code change should be reconsidered.]
r C-6.
A review of the Category I structural concrete drawings for Millstone Unit 1 indicated that there are a number of concrete brackets in the turbine building structure with a shear-span-to-depth ratio of unity or less. All of these brackets have a/d ratios of 0.5 or less, except for one case which.has a ratio of 0.62. _
TER-C5506-436 J
A typical bracket (with a/d = 0.33) for the turbine building was checked against Section 11.13.
. i
)
The analysis of the' bracket chosen showed it to satisfy the-intent I
of Section 11.13. Therefore, it is concluded that the brackets and corbels at Millstone Unit 1 meet the requirements of ACI 349-76.
1 C-7.
A comparison was made between the shear sections of ACI 318-63 and Section 11.15 of ACI 349-76. The following five values were 4
compared:
1.
calculated shear stress 2.
total design shear stress allowable 3.
design concrete shear stress allowable 4.
steel reinforcement 5.
punching shear stress allowable.
The result of the comparisons are as follows:
I 1.
The calculated shear stresses are the same using both methods provided d (distance from compression face of wall to the centroid of tension reinforcement) used in the 1968 code is j
assumed to be equal to 0.8 of the wall thickness.
1 2.
The total design shear stress allowables are the same.
l 3.
By conservatively comparing an upper bound value of ve for i
the 1963 code to an assumed lower bound value of v of the e
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i 1976 code, only a potential 11% decrease in allowables was calculated. Therefore, based on the conservative assumptions used in this comparison, the two concrete allowable shear stresses are considered to be equivalent.
4.
The lower bound percentage of horizontal reinforcement is the i
same for both codes. However, the lower bound significantly j
increased for the 1976 code. A sampling of building walls was checked which showed that the 1976 lower bound percentage of vertical reinforcement has been met for the shear walls at
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Millstone Unit 1.
l 5.
The punching shear stress allowable for the 1976 code is l
greater than, or equal to, the allowable for the 1963 code.
Therefore, based on the results given above, it is concluded that l
the shear walls at Millstone Unit 1 meet the requirements,of ACI l
349-76s l
C-8.- A sampling of concrete hatches was checked to verify that the amount of steel reinforcement meets the requirements of Section l
11.14 of ACI 349-76.
i To perform these calculations, an area of reinforcement needed for i
deadweight was determined assuming minimum values for coefficient
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TER-C5506-436 2
of-friction and yield strength of reinforcirv;p bars. This area was then compared' to the actualexisting area to detemine bload i' ;
factor available in the existing reinforcement./ This loah factor 1
would need to be large enough to accounts for live loads, seismic
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M The minimum load factor calculated for the sar:.pling of, hats 9s analysedwas15.5,whichwasconsideredmorethahadeejuatefor total loadings. Therefore, it is concluded that the~ concrete hatches at Millstone Unit 1 meet the requirements of Section 11.14 3
of ACI 349-76.
(Hatches were checked as the only precast concrete structures used in Millstone Unit 1.
This application of the code revision was the
, E-one the Licensee was specificallp requested to check.')
^f C-9.
The structures have seen no idverse effects fr6m nomal operations
~
over the many years of plant operitions. '.2herefore,, there is no reason to expect problems resulting from future normal opspations.-
The temperature limitations for accident conditions according to ACI 349-76 are as follows:
i.
1.
Temperatures shall nr.,t exceed 350'F for the su$ce, v:
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' 2.
tocal areas shall not exceed 650*F.s I
. Structures at Millstone Unit I will most likely not see lemperature in excess of the ACI limitatione.for accidents.
The maximum main steam temperatures for Millstone Unit I will be approximately 550*F based on documented temperatures for the Oyster
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Creek plant, which is similar in design and size. An accident of S
this type is of short duration, and the temperatures will decrease
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rapidly over time and distance from the source; overa?,1 surface r
j-temperatures will not exceed the 350'F limit.
C-10. [The Licensee presented a discussion of the " Fatigue Eav konment" of concrete columns in Scismic Category I buildings, expressing the opinion that fatigue usago would be found saall and leading to the.
following conclusion:
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" Based on the discussions given above for the general fatigue environment for building columns, it is concluded that column j
reinforcement splices designed to ACI 318-63 will be adequate for alternating stresses."
i Although the provisions of this code requirements do increase 'the capacity of concrete colune.s to withstand fatigue loadings, the current code requires design to currer.t rules for columns which may
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be subject to any load reversal at all. The magnitude of the most
"'f4 severe load reversal should be identified and the integrity of the
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splice under maxista reversed mome.,nt load should be checked.)
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'T C-11. '.t.: i:.:ic types of.embedmontr have been noted in the Millstone
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Unit.1 drawings:
1.
anchor bolts 2.
stud anchors
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3.
expansion anchrrs l
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- 4.. embedded shapes and plates, shear lugs.
g Anchor bolts have'been used extensively in steel beam to concrete wall, and steel column to concrete slab connections. The majority see little, if any, tension since the beam connections are for shear, and the columns will have small liftoff loads. A conservative example for anchor bolts was analyzed by checking a crane column connection ist the reactor building assuming the total r/
vertical downward load acts upward. This connection had four anchor bolts with oveels,. ping shear cones, shear lugs and two anchor bolts near the 4dge of a concrete slab. The pullout, lateral bursting, and edge distance requirements have all been 0'
ratisfied for this connection. The remaining anchor bolt 7~
fesu'ections are considered adequate by comparison to this i
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conservative example.
b
. Stud anchors have also been_ ussd extensively at Millstone Unit 1.
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.y'/dost are used to attach steel angles and plates to concrete corners and edges for protection against crumbling of the concrete.
Nelson studs have.'been used in the turbine building as shear connectors betweeh a honcr6te slab and steel beams to create composite girders.- The1980 code changes do not apply to these applications.
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Expansion anchors have been used at Millstone Unit 1 to attach pipe
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supports and light structures to the Category I concrete structures.
[
All: expansion anchors used in large bore piping supports have been jj evalmted per NRC IE Bulletins 79-02'and 79-14, and therefore need not be considered in this review. Note that these bulletins e
required checking of bolt spacing, edge distance, and shear-tension 1
interaction.
All expa sion anchors are considered adequate.
A numbe'r M miscellaneous embedded shapes and plates have been notsd on the Millstone Unit 1 drawings and all embedded shapes and plates ara considered adequata.
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'C-12. Missile impact test.1 have been performed by various companies to p3-(
determine concrete thickness nece.ssary for'the preclusion of
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'd-scabbing. Table 6.6 on page 342 of Reference 10 gives results of some of these tests. The results show maximum thicknesses of 24
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NY inches for the worst case impacts Oith most thicknesses less than 9,,
12 inches. The majority of the main structural walls of u
M111 stone's Category I structures have thicknesses in excess of th, i
test values, indicating that scabbing wculd probably not occur.
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Section 6.4.1.2.6 of Reference 10 recommends about 0.3%
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longitudinal reinforcing" steel'in each direction to inhibit mass s
trb cracking, spalling, and scabbing. Of this? reinforcing steel, at least 50% should be located close to the rear face and at least 25%
should be located near the front face.
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Based on the wal's checked for reinforcement percentage in the Item 7 section, the 0.3% recomunendation has been met at Millstone Unit 1.
Also, the reinforcing bars have been placed so that 50% of the reinforcement is located near each face of the walls.
Tornado missile impact studies have also been done specifically for
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Millstone Unit 1 structures as another part of the SEP evaluations. All areas identified by the NRC as being vulnerable to tornado missiles have been shown acceptable on the basis that either the vulnerable equipment is not essential for a safe shutdown or that there is sufficient redundancy in the safety systems to bring the plant to a safe shutdown condition.,This study!would indicate a-similar acceptability for other external 4
missiles.
7 t:- '
Areas identified by the NRC as being adequate for tornado missile
!I impact have been further. evaluated in accordance with Appendix C of ACI 349-80 for the SEP loading combination changes.
4 i(' '
Based on the testing and analysis information done both specifically for Millstone Unit 1 and generically, Millstone Unit 1 i
Category I structures are considered adequate for the intent of Appendix C of ACI 349-80.
'l,.
C-13. The material for the shell of the drywell, suppression chamber, and interconnecting vent system is ASTM A516, Grade 70.
Materials used for penetrations which form part of the pressure boundary are A516, Grade 70, A333, Grade 1, and A530, Grade LFI. All of these materials are listed in Table 1.10.1 of the 1980 code. Therefore, this code change does not affect Millstone Unit 1.
C-15. The primary containment system at Millstone Unit I was " Designed by Formula." The overall integrity of the primary containment system has been demonstrated by rigorous analyses done by General Electric and NCT Engineering (California). The General Electric report, w
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Reference 11, deals in detail with all aspects of primary containment system qualification.
It qualifies the system for all i
levels of service conditions. The NCT Engineering report,
" Systematic Evaluation Program Structural Review of Millstone Unit No. 1 Drywell Containment Structure," dated April 1982 (12]
qualified the drywall for Service Level O and LOCA with an SSE horizontal peak ground acceleration of 0.2 g.
Moreover, the allowable stresses used in the General Electric report per the 1965 code are lower than allowable stresses per the 1980 code.
C-17. The material of stiffening rings and primary containment is the same, making this code requirement not-applicable to the primary containment of Millstone Unit 1.
C-18. The calculated R /t ratio is much greater than 24; the margins of L
safety are not affected by the changed requirement.
C-19. None of the closures at Millstone Unit I are quick actuating closures as defined in the provision of the code. Therefore, this code change is not applicable.
C-21. This comment was addressed by establishing that primary containment does not require fatique analysis. ASME III, Subsqction NE-3221.5 (d) sets forth six conditions.
If they are met, then no fatigue analysis is required. Primary containment was evaluated for all these conditions, and it was established that all of them are satisfied. Therefore, this requirement of the code does not apply to Millstone Unit 1 primary containment.
[It does not appear that cyclic effects associated with suppression pool dynamics were considered in this evaluation. Containment openings in affected locations may not qualify for exclusion from fatigue design requirements. However, results from the Mark I containment review program are understood to have provided justification of integrity of all major torus openings, and on this basis the issue is accepted as resolved.]
e g
t
=.
-^~
^~
^
- ^
TER-C5506-436 5.
LOADS AND LOAD COMBINATIONS For Seismic Category I structures, NRC's Standard Review Plan [14]
states, in generic terms, the loads and load combinations which currently must be considered in structural design.
In specific applications, loads in all generic categories may not~ occur; or some, even if applicable, may be negligible in comparison to the dominant loads. Moreover, for certain structures, some of the loads included in the generic load combinations may:
1.
be absent 2.
be negligible 3.
not occur simultaneously with all loads specified in a given load combination.
Consequently, the previous TER on Topic II-7.B [1] presented, on.a I
structure-by-structure basis, a tentative list of loads and a list of load combinations where design requirements were reduced to include only those loads and load combinations deemed appropriate to each specific structure.
Licensees were requested to verify the accuracy of these findings.
Confirmation by the Licensee establishes the structure-specific loads and load combinations appropriate under current regulatory requirements.
In addition, current requirements may include loads not considered in the original design or load magnitudes different from those originally treated.
Disparities of this kind were identified in Reference 1 by structure.
If they I
were deemed to have the potential to significantly degrade the originally l-computed margins of safety, they were, in addition, designated Scale A.
l l
Noreover, disparities may exist between load. combinations originally treated and those currently specified. Disparities with adverse impacts may 7
arise if the load combinations originally considered:
1.
Employed loads of lesser magnitude than current requirements, prescribe.
2.
Omitted load categories now required in the nombination.
l
, i
-, -,. ~, - - - -, -... -.. -,
~
TER-C5506-436 i
On a structure-by-structure basis, Reference 1 identified such l
disparities, if they existed. Moreover, certain loading combinations (associated with extreme loadings) were designated Scale A if the potential existed that originally computed margins of safety might appear to be appreciably smaller when current requirements were invoked. For load combinations designated Scale A, licensees were requested to assess the actual impact of current load combination requirements on safety margins. These findings follow on a structure-by-structure basis.
5.1 REACTOR BUILDING CONCRETE 5.1.1 Structure-Specific Load Combinations Reference 1 proposed a tentative set of structure-specific load
.I combinations which would be appropriate for this structure were it to have been designed and licensed in accordance with current criteria of Reference
- 14. The following findings of the Licensee are relevant to these load combinations:
" Normal operating temperature (T ) for the Reactor Building ranges o
between 85'F and 95'F.
Such temperatures would not have significant effects on the structure. A field survey indicated that no large piping systems are supported by the exterior walls of the Reactor Building.
These loads were, therefore, also eliminated from the combination."
l FRC concurs. Accordingly, the generic load combinations of Reference 14 reduce to the following structure-specific load combinations:
1.
1.4D + 1.7L 2.
1.4D + 1.7L + 1.9Eo 3.
1.4D + 1.7L + 1.7W l
4.
0.75 (1.4D + 1.7L) 5.
0.75 (1.4D + 1.7L + 1.9Eo) 1 6.
0.75 (1.4D + 1.7L + 1.7W) 7.
1.2D + 1.9Eo 8.
1.2D + 1.7W l
9.
D + L + E' l
10.
D + L + Nt 11.
D + L + Ta + 1.5 Pa I
l i
1 l l
., ~
s-
<s
[j TER-C5506-435 D + L + Ta + 1.25 Pa + 1.25E + Y D + L + Ta + Pa + E' + Yj + Ym* j + Y,*7 12.
y 13.
g
[
5.1.2 Sc&1. A :~.d Combinations LoadcombinationscitedasScaleAinRefeNence1areshownbelowinthe structure-specific form developed in the previous section.
Icad Combination Number Load Combination Load Combination 10 D+L+Mt Load Combination 13 D+L+T_a+Pa + E' + Yj +Y,
,x 5.1.3 Licensee Review Approach
..: z Three walls were evaluated for load combinatiess 10 using current tornado load criteria appropriate to Millstone Unit 1.
,j Structure Purpose of Analysis Loads
.g RB Walls at El.
Establish wall shear 300 mph tornado wind 3
- J 14'-6" and moment capacity to (W,& W included)
^
p withstand Wt South Wall Between Panel response to 300 mph tornado wind +
El. 14'-6" & 42'-6" tornado wind and missile utility pole impact **
East Wall Between Same as above (protection: 300 mph tornado wind +
El. 82'-9" & 108'-6" of isolation condenser std. steel rod system)
Load combination 13 appears to have been evaluated in two parts:
, 3 13(a) Overall effects:
D + L + 2' T,P,Yj,Y 13(b) Local effects:
o a
a Reactor building walls were evaluated for the 13(a) combination.
- The Licensee has taken the position (see Reference 15) that the simult'aneous occurrence of pipe rupture and seismic load is not appropriate for inclusion 4 ',
in the design basis of Millstone Unit 1.
- Penetration effects considered elsewhere in Licensee evaluation.
3 i
w -. -
?
TER-C5506-436 4
Structure Purpose of Analysis Loads RB Walls at 14'-6" Establish wall shear NRC 0.2 g ground and moment capability to response spectrum resist SSE In addition, a pipe-break and target identification and effects analysis was performed for Y3 and Y,.
5.1.4 Licensee Findinos The reactor building has sufficient base shear and moment capacity to withstand a 300 mph tornado and also a 0.2 g SSE. The largest wall panel when impacted by a tornado pole missile will deform plastically but has sufficient ductility to prevent failure. The condenser room wall has sufficient strength to withstand a 300 mph tornado.
5.2 REACTOR BUILDING (STEEL SUPERSTRUCTURE) 5.2.1 Structure-Specific Load Combinations Reference 1 proposed a tentative set of structure-specific load combinations which would be appropriate for this structure were it to have been designed and licensed in accordance with current criteria of Reference
- 14. The following findings of the Licensee are relevant to these load combinations:
"The comments stated for the concrete protions of the reactor building i
also apply to the steel portions."
Accordingly, the generic load combinations of Reference 14 reduce to the following structure-specific load combinations:
1.
D+L 2.
D+L+E 3.
D+L+W 4.
D+L 5.
D+L+E 6.
D+L+W 7.
D + L + E' 8.
D + L + Wt.
a.-:-
...~
r 90 TER-C5506-436 9.
D + L + Ta + Pa
- 10. D + L + Ta + Pa + E + Y5+Y m
- 11. D + L + Ta + Pa + E' + Tj + Y m
5.2.2 Scale A Load Combinations Load combinatins cited as Scale A in Reference 1 are shown below in the structure-specific form developed in the previous section.
Load Combination Number Load Combination
/*
Load Combination 8 D+L+Wt Load Combination 11 D + L + T. + Pa + E' + Yj + Ym 5.2.3 Licensee Review Approach Roof beams with supporting columns were evaluated for load combination 10.
Structure Purpose of Analysis Loads 14" roof beam and Tornado resistance of-300 mph tornado north & south side roof beams and columns 245 mph tornado steel columns (roof deck removed)
Roof steel and wall columns were evaluated for load combination 11 in a region where large piping does not exist (eliminating T,, P,, R,, Y,,
Y, and Y,from consideration).
3 Structure Purpose of Analysis Loads Roof steel and wall Overall structure D + L + E' using floor columns integrity under SSE response spectra associated with site-specific ground response spectrum (envelope of 0.17 g and' 0.19 g curves)
- The Licensee has taken the position (see Reference 15) that the simultaneous occurrence of pipe rupture and seismic load is not appropriate for inclusion in the design basis or Millstone Unit 1.
TER-C5506-436 d
5.2.4 Licensee Findings The roof deck and walls do not have the capacity to withstand a 300 mph tornado wind, but with roof deck removed the support beams and columns are
-6 capable of withstanding a 245 mph tornado wind (1 x 10 probability of exceedance). Moreover, the structure has sufficient strength to withstand the site-specific SSE.
5.3 SPENT FUEL POOL (CONCRETE) 5.3.1 Structure-Specific Load Combinations Reference 1 proposed a tentative set of structure-specific load combinations which would be appropriate for this structure were it to have
- j been designed and licensed in accordance with current criteria of Reference
~ t
- 14. The following findings of the Licensee are relevant to these load combinations;
" Accident temperature is 140*F."
i The structure-specific load combinations according are as stated in
~
Reference 1:
1.
1.4D + 1.7L 2.
1.4D + 1.7L + 1.9E 3.
1.4D + 1.7L 4.
0.75 (1.4D + 1.7L) 5.
0.75 (1.4D + 1.7L + 1.7 + 1.9E) 6.
0.75 (1.4D + 1.7L + 1.7 + 1.7W) 7.
1.2D + 1.9E 4
8.
1.2D 9.
D + L + E' i
- 10. D + L + Nt
- 11. D + L + Ta l
- 12. D + L + Ta + 1.25Eo
- 13. D + L + Ta + E' o
5.3.2 Scale A Load Combination The load combination cited as Scale A in Reference 1 is shown below in the structure-specific form developed in the previous section.
t
$ i
,..,-,-.--,.=-,-_----..--n.,
..-,.....n.-,,__
- - -,. ~,..,. -. - - - - - - -. -
c.
~.
..c 7
TER-C5506-436 Load Combination Number Load' Combination r.
Load Combination 13 D+L+Ta + E' 5.3.3 Licensee Review Approach A typical pool wall was examined for load combination 13.
Structure Purpose of Analysis Loads Spent Fuel Pool Wall Pool retention under Site-specific seismic load spectrum (compo-site 0.17 g and 0.19 g envelope). Seismic response of water and fuel racks included.
2-5.3.4 Licensee Findings The spent fuel pool has sufficient integrity to withstand the site-specific SSE.
5.4 CONTROL ROOM /RADWASTE BUILDING (PORTION HOUSING CLASS 1 EQUIPMENT) 5.4.1 Structure-Specific Load Combinations Reference 1 proposed a tentative set of structure-specific load combinations which would be appropriate for this structure were it to have been designed and licensed in accordance with current criteria of Reference
- 14. The following findings of the Licensee are relevant to these load combinations:
" Thermal loads are insignificant."
Accordingly, the generic load combinations of Reference 14 reduce to the following structure-specific load combinations:
1.
1.4D + 1.7L 2.
1.4D + 1.7L + 1.9E 3.
1.4D + 1.7L + 1.7W s
4.
0.75 (1.4D + 1.7L) 5.
0.75 (1.4D + 1.7L + 1.9E) 6.
0.75 (1.4D + 1.7L + 1.7W) '
l TER-C5506-436 7.
1.2D + 1.9E 8.
1.2D + 1.7W 9.
D + L + E'
- 10. D + L + Wt
- 11. D '+ L + 1.5 Pa
- 12. D + L + 1.25 Pa + 1.2SE +Yr + Yj + Y m
- 13. D + L + Pa + E' +Yr + Yj + Y a
5.4.2 Scale A Load Combinations Load Combinations cited as Scale A in Reference 1 are shown below in the structure-specific form developed in the previous section.
Load Combination Number Load Combination i.
Load Combination 10 D+L+Wt l
Load Combination 13 D+L+Pa + E' + Yr + Yj + Ym 5.4.3 Licensee Review Approach The roof and walls of the control room and radwaste building were investigated for load combination 10.
Structure Purpose of Analysis Loads Control Room Roof Integrity of control 300 mph + utility pole of control room under tornado East Wall of Control Integrity of control
- a. 300 mph + utility Room between El.
of control room under pole 34'-6" and 54'-6" tornado
- b. tornado differential pressure Load combination 13 appears to have been addresed in two parts:
13(a) Overall Effects:
D + L + E' 13(b) Local Effects:
D + L + Pa + Yr + Yj + Ym A wall section of the control room /radwaste building was analyzed under load combination 13(a).
- The Licensee has taken the position (see Referene 15) that the simultaneous occurrence of pipe rupture and seismic load is not appropriate for inclusion in the design basis of Millstone Unit 1..
t,.,
TER-C5506-436 Structure Purpose of Analysis Loads Building Wall at Assa,ssment of wall.to D + L + E' El. 14'-6" resist SSE lateral-Two independent load analyses made using:
1.
NRC (0.2 g')
2.
Impell (site-specific spectrum)
In addition, the combination D + L + p, + Yg+Y,+Y,was previously addressed.
Licensee Findings The control room building can withstand the fulleeffects of a 300 mph tornado including strikes of a standarized utility gale missile on either the roof or walls which then deform plastica 11y withouEfailure. The building also has adequate strength to withstand a 0.2 g SSE.
5.5 GAS TURBINE BUILDING n
5.5.1 Structure-Specific Load Combinations Reference 1 proposed a tentative set of structure-specific load combinations which would be appropriate for this structure were it to have been designed and licensed in accordance with current criteria of Reference
- 14. The following findings of the Licensee are relevant to these load i,
l
combinations:
" Normal temperature in the building is close to ambient."
Accordingly, the generic load combinations of Reference 14 reduce to the following structure-specific load combinations:
1.
1.4D + 1.7L i
2.
1.4D + 1.7L + 1.9E 3.
1.4D + 1.7L + 1.7W 4.
0.75 (1.4D + 1.7L) 5.
0.75 (1.4D + 1.7L + 1.9E) 6.
0.75 (1.4D + 1.7L + 1.7W) 7.
1.2D + 1.9E i
1.
TER-C5506-436 8.
1.2D + 1.7W 9.
D + L + E' 10.
D + L + Wt 11.
D+L 12.
25E 13.
D + L + E' 5.5.2 Scale A Load combinations The load combination cited as Scale A in Reference 1 is shown below in the structure-specific form developed in the previous section.
Load Combination Number Load Combination Load Combination 10 D+L+Wt 5.5.3 Licensee Review Approach The gas turbine building roof, walls, and concrete columns were examined for load combination 10.
Structure Purpose of Analysis Loads Roof Slab, Roof Steel Building integrity under 300 mph tornado Concrete Walls, and tornado including Columns (NRC) differential pressure Coltens Only Rexamined under different Tornado differential (NUSCO Analysis) boundary condition pressure (this is the assumption.
most severe effect) 5.5.4 Licensee Findings The gas turbine building is not adequately protected against tornado missiles, but in their absence can withstand the full effects of a 300 mph tornado.
5.6 INTAKE STRUCTURE 5.6.1 Structure-Specific Load combinations Reference 1 proposed a tentative set of structure-specific load combinations which would be appropiiate for this structure were it to have
- ; - - 7, 7-t TER-C5506-436
- k been designed and licensed in accordance with current criteria of Reference
- 14. The following findings of the Licensee are. relevant to these load combinations:
"The normal temperature in the building is close to ambient. Normal pit reaction forces were not applicable. A field inspection indicated that there are no large piping systems supported on the exterior walls or roc structure."
l 'J'.
The Licensee also noted that the discharge structure, which was includec in Reference 1, is not significant at Millstone Unit 1 and should have been
..g
"(
omitted. Accordingly, for the intake structure, the generic load combinations of Reference 14 reduce to the following structure-specific load combinations:
s,~.
1.
1.4D + 1.7L 2.
1.4D + 1.7L + 1.9E 3.
1.4D + 1.7L + 1.7W 4.
0.75 (1.4D + 1.7L) 5.
0.75 (1.4D + 1.7L + 1.9E) 6.
0.75 (1.4D + 1.7L + 1.7W)
- 3.,
7.
1.2D + 1.9E 8.
1.2D + 1.7W 9.
D + L + E'
- 10. D + L + Wt
- 11. D + L
- 12. D + L + 1.25E
- 13. D + L + E' j
S.6.2 Scale A Load Combinations The load combination cited as Scale A in Reference 1 is shown below in the structure-specific form developed in the previous section.
Load Combination Number Load Combination Load Combination 10 D+L+Nt 5.6.3 Licensee Review Approach The roof, walls, and columns of the intake structure were investigated for load combination 10.
\\
i f
e 39-
-*i we-e mir-re--w-w w
-rea-w
-e n-www-
-'a---.
m-
+-vWP
,p--g-=+
_Wy'-
v-v-'-we--py i-*w-wg-
.,y--r
iy-eg"
TER-C5506-436 Structure Purpose of Analysis Loads North and South Building integrity with 300 mph tornado wind
~ Walls, Their Concrete hatches blown 281 aph tornado wind Columns, Roof Slab, and Beams, Center Girder, and Interior-Steel Columns 5.6.4 Licensee Findinos Building hatches will blow off in a tornado; with the building thus vented, the wall panels of the intake structure are capable of withstanding a 221 mph tornado wind (probability of exceedance 4 x 10~7).
5.7 TURBINE BUILDING (PORTION HOUSING CLASS I EQUIPMENT) 5.7.1 Structure-specific Load Combinations
. Reference 1 proposed a tentative set of structure-specific load combinations which would be appropriate for this structure were it to have been designed and licensed in accordance with current criteria of Reference
- 14. The following findings of the Licensee are relevant to these load combinations:
Normal operating temperature (T ) for the Condenser Room is 130'F."
o Accordingly although credit may be given for further reductions in portions of the structure (e.g., one wall cited as supporting no pipes), the generic load combinations of Reference 14 applicable to this structure are:
1.
1.4D + 1.7L 2.
1.4D + 1.7L + 1.9Eo 3.
1.4D + 1.7L + 1.7W 4.
0.75 (1.4D + 1.7L + 1.7 To'+ 1.7 R )
o 5.* 0.75 (1.4D + 1.7L + 1.7 To + 1.7 Ro + 1.9Eo) 6.
0.75 (1.4D + 1.7L + 1.7 To + 1.7 Ro + 1.7W) 7.
1.2D + 1.9Eo 8.
1.2D + 1.7W 9.
D+L+To+Ro + E'
- 10. D + L + To+Ro + Mt
- 11. D + L + Ta + 1.5 Pa+Ra
TER-C5506-436 12.
D+L+Ta + 2.5 Pa+Ra + 1.25E + Yr+Yj+Y m
13.
D+L+Ta+Pa+Ra + E' + Yr + Yj + Y a
e 5.7.2 Scale A Load Combinations Imat combinations cited as Scale A in Reference 1 are shown below in the structure-specific form developed in the previous section.
Load Combination Number Load Combination Load Combination 10 D+L+To+Ro+Nt i:
Load Combination 12 D+L+Ta + 1.25Pa+Ra+
1 1.25E + Yr + Yj + Im i.
The Licensee found, however, that load combination 13 contains loads which produce higher stresses and substituted this for load combination 12.
i Load Combination 13 D+L+Ta +'Pa+Ra 4 E' +
[.
Yr + Yj + Ym u
5.7.3 Licensee Review Approa t Theturbinebuildingwallswereinvestigatedfor.Ioadcombination10
)..
(less R,, which is not appropriate since no significant piping is supported on the building walls).
ps Structure Purpose of Analysis Loads Building Walls Protection of safety 300 mph wind and systems in building differential pressure during tornado No missiles (it penetrates)
Load combination 13 appears to have been addressed in twc parts:
c 13(a)
Overall Effects:
D + L + E' 13(b)
Local Effects:
D+L+Ra+Yr + Yj + Y,
l
- The Licensee has taken the position (see Reference 15) that the simultaneous I
occurrence of pipe rupture and seismic load is not appropriate for inclusion j
in the design basis of Millstone Unit 1.
4
---w--~~+w
,,m-7,--,,--em.,._,...yw
_n_.-,-._-...m-_-m-__m,,.
__,m,..,
,,,,. ~.,,...... _ - _ _..
,_-_r
TER-C5506-436 A wall of the condenser room was selected as a potentially critical structure under load combination 13(a).
Structure Purpose of Analysis Imads Condanser Room Assessment of integrity D + L + E', using of concrete shield wall 0.2 g ground response under lateral SSE spectrum In addition, the effects of load combination 13(b) were previously i
addressed in a 1973 WRC study.
Licensee Findines Although the condenser roora is not tornado missile protected, it can withstand a 300 mph tornado wind and a 0.2 g SSE.
5.8 TURBINE BUILDING (STEEL) 5.8.1 Structure-Specific Load Combinations Although Reference 1 did not cite the steel superstructure of the turbine building in the list of structures to be examined, the Licensee included it for completeness. The Licensee made the following observations with respect to load combinations appropriate to this structure:
Imads due to temperature and pipe reactions were stated as not considered in the analysis made (the overall ability to resist wind loads) because they were irrelevant to the assessment, not because they are absent in the structure. They are included below:
1.
D+L 2.
D+L+E 3.
D+L+W 4.
D + L + To + Ro 5.
D + L + To + Ro + E 6.
D + L + To + Ro + W 7.
D + L + To + Ro + E' 8.
D + L + To + Ro + Nt 9.
D + L + Ta + Pa + Ro J
l 1
TER-C5506-436 10.
D + L + Ta + pa + Ra + E + Y.i + Yr+Ym 11.
D + L + Ta + pa + Ra + E' + Tj + Yr+Ym
- 5.8.2 Sc4. A Lv.d Combination Load combination 8 was selected by the Licensee for consideration.
It shown below as developed in the preceding paragraph.
Load Combination Number Load Combination Load Combination 8 D+L+To+Ro+Wt
., l 5.0.3 Licensee Review Approach The turbine building steel was evaluated for load combination 8 (less f
normal temperature and pipe reaction loads, which are not significant for this overall analysis) assuming the roof deck in place [ed also absent.
Structure Purpose of Analysis
~
Loads Steel Columns and Determination of tornado Tornado winds 175 mph Roof (various load limiting structural..and over assumptions) elements
\\
\\
In addition, the seismic resistance capacity of the turbine building steel was considered in the SEP as documented in NUREG/CR-2024.
b.
5.8.4 Licensee Findings Although not explicitly stated, it appears that the steel superstructure of the turbine building is not tornado missile protected.~ Evaluations of the structure assume that the roof deck will blow off and that the siding may or
~
may not do so. The tornado resistance of the frame is 1imited by the tornado wind loading on the web of the 50-inch deep girder. It can withstand a 175
-5 mph tornado wind (probability of exceedance 1 x 10 3,
- The Licensee has taken the position (see Reference 15) that the simultaneous occurrence of pipe rupture and seismic load is not appropriate for inclusion in the design basis of Millstone Unit 1.
1
TER-C5506-436 5.9 DRYMELL STRUCTURE 5.9.1 Structure-Specific Load Combinations Reference A proposed a tentative set of structure-specific load combinations which would be appropriate for this structure were it to have t
been designed and licensed in accordance with current criteria of Reference
- 14. The following findings of the Licensee are relevant to these load combinations.
" Loads due to Ps, Rs and Ts are related to the discharge of safety relief valves into the suppression pool and, therefore, need not be considered in any structural evaluation of the drywell."
This statement is correct except that substantial dynamic loads accompanying discharge of safety relief valves may be transmitted to the drywell structure. Thus, these effects are retained in the load combinations and the full set of generic load combinations of Reference 14, without reduction, is considered to be structure-specific.
5.9.2 Scale A Load Combination The load combination cited as Scale A in Reference 1 is shown below in the structure-specific form developed in the previous section.
Load Combination Number Load Combination Load Combination 13 D + L + Ta + Pa + Ra + E' +
Yr + Yj + Ym 5.9.3 Licensee Review Approach The Licensee reviewed existing drywell ec:,atations in the light of current requirements implicit in load combination 13. The drywell had previously been shown capable of withstanding combined SSE and LOCA. These events, nevertheless, were separated in accordance with the Licensee's
. position that the simultaneous effects of pipe rupture and seismic loads are not appropriate for inclusion in the Millstone Unit 1 design basis. Loads' caused by discharge of safety relief valves into the suppression pool were also removed from the combination, reducing it to a previously analyzed case.
TER-C5506-436 In addition, a seismic event in conjunction with flooding was investigated to evaluate the effects of the incremental seismic load needed --
correspond to current criteria.
5.9.4 Licensee Findings The containment vessel has previously been investigated in depth. The drywell has sufficient safety margins to withstand the incremental loadings associated with current response spectrum requirements.
5.10 REVIEW COMMENTS - LOAD AND LOAD COMBINATIONS In general, the Licensee has applied a consistent approach to the review of Millstone 1 Seismic Category I structures against modern criteria. The Licensee has selected representative structural components for analysis from each of the structures that were to be investigated. The Licensee then applied loads and load combinations which are representative of some of the very severe loadings for which nuclear structures currently are designed; analyzed them in accordance with current code rules; and evaluated them to current design code acceptance limits.
This course is a straightforward way of testing, on a sample basis, the integrity (based on modern requirements) of Millstone Unit 1 structures against the selected loads.
In some cases, the Licensee has used results of analyses condu.cted to investigate other SEP topics to respond to the intent of SEP Topic III-7.B.
This usage (as far as it goes) is both reasonable and proper.
However, the findings with respect to structural capability to withstand the SSE with concurrent LOCA rest upon a segregation of load combinations containing dead weight, live loads, and seismic (SSE) loads from loads associated with pipe rupture. Current load combination requirements st,ipulated by NRC's Standard Review Plan call for their simultaneous consideration.
The Licensee has taken the position tnat the simultaneous occurrence of pipe rupture and seismic load is not appropriate for inclusion in the design basis of Millstone Unit 1 and has addressed Topic III-7.B accordingly. Since this is a clearly stipulated requirement of NRC's Standard Review Plan, the
}
TER-C5506-436 Licensee should be requested to supply the technical grounds.for, and assess the implications of, its omission.
One additional item was not fully reported in this document--the capability of roof structure to withstand the extreme environmental snow load. The magnitude of this load was identified in SEP Topic II-2.A, but this task was not charged with assessing the capability of Seismic Category I plant structures to withstand it.
Buildings for which this load had been designated Scale A are to be reviewed for their ability to support the designated load undc e Topic III.7-B.
The Licensee should be requested to report on this issue.
4 I
I i
3 v.h
- *~
~
_. a
~
TER-C5506-43' 6.
SUMMARY
OF REVIDi FINDINGS s..
This section focuses on issues not considered to be fully resolved by tt Licensee's submittal. Four of these relate to the assessment of post-constrw tion design code changes and their impact upon perceived margins of safety fo:
Seismic Category I buildings at the Millstone plant. Two others relate to thx corresponding assessment of the impact of the current criteria for design loads and load combinations.
6.1 DESIGN CODE CHANGES Of the four items in this category, the one relating to design requirements for bellows expansion joints has been deferred by the Licensee pending a review by the bellows manufacturer. The current design requirements are found in paragraph NE-3365.2 of subsection NE of the ASME Boiler and Pressure Vessel Code, Section III: no corresponding design guidance was provided by the codes to which the Millstone plant was constructed.
For all other design code change items, the Licensee provided information; but in three cases (discussed individus11y below), the information supplied was deemed inadequate to resolve the issue.
1.
C - ression Elements with Laroe b/t Ratios (AISC 1.9.1.2)
Current code requirements provide stress reduction factors for unstiffened formed shapes in compression.
Previous codes allowed the designer to neglect a portion of the area of such elements.
j i
For some structural tees, current requirements require significant stress reduction beyond those inherent in the previous method (see the discussion in Section 2.4 of this report).
l The Licensee adopted a sampling procedure to address this issue, but did not furnish a description of its extent, plant-wide applicability, or quantitative findings (see our cassent C-4 on page 23).
l.
l,'
Evidence derived from a sampling approagh provides a reasonable l-engineering basis for making plant-wide projections and judgments
[*
concerning this issue. However, a more complete description of this effort is needed to demonstrate the validity of a conclusion of j
plant-wide adequacy. The information sought should includes a.
the sample size b.
the range of shapes investigated <
.u
]
TER-C5506-436 c.
an estimate of the total number of structural toes plant-wide and the number in each size d.
the method of selection for the samples to be investigated e.
the safety margins found in the samples.
f.
a sununary of any other factors contributing significantly to the conclusions drawn.
l 2.
Cooed Beam Connections (AISC 1.5.1.2.2)
AISC-80 requires that the' design of beam connections where the beam is coped consider the possibility of " block shear" failure (see Section 2.6).
This requirement did not exist in the 1963 code.
In reviewing N111 stone structures for the impact of this code change, the Licensee appears to have done the following:
1.
Identified beams in Millstone strucutres (or a sample of such beams) that are coped.
2.
Assumed (because actual connection details were not available) that the designer had specified ASME standard connections for these beams.
3.
Assumed the beam was uniformly loaded, taking the load as the maximum uniform load recommended by the AISC specificatica for the given beam.
4 4.
Computed the cor' responding block shear in the member.
Except for identification of beams which were coped in Millstone structures, the analysis makes little reference to actual applications in service. Connection details and beam shear loads are both assumed. Given the paucity of information on connection details, it is not unreasonable to assume that a standard connection detail was used. However, the shear loads on the connection should be taken from computations of the most severe loadings imposed on the beam in actual service.
3.
Columns with Soliced Reinforcements Subiect to 5:ress Reversals (ACI 7.10.3)
For concrete columns built using spliced reinforcement, which can experience stress reversals (due to column moments from design loads, for example), ACI-344-76 supplies guidance for splice design (see Section 2.13).
No similar requirements were provided 1,n ACI-318-63.
The Licensee's response (cited in comment C-10) discusses column adequacy in fatigue. This skirts the issue since the code requirement applies to any column that will ever experience stress reversal in one of its faces.
The justification of column adequacy should address this point, not fatigue adequacy alone.
i j
.; o. - e TER-C5506-436 6.2 LOADS AND LOAD COMBINATIONS s,
Loads and loading combinations are individually reviewed for each Seism.
Category T kni W ag'in Section 5.
The Licensee was asked to review margins of safety for buildings under selected current load combinations, usually two per structure. Where applica-bletodivenstructures,thetornadoloadcombinationandthecombination containing SSE and LOCA were usually cited for investigation.
Millstone Unit 1 Seismic Category I buildings do not all fully comply with current design requirements for tornado protection. Three qualify under reduced maximum wind speeds and several could be penetrated by tornado missiles. However, all such issues have been resolusd on other grounds, such e
a as the low probability of withstandable tornado winds and the protection of safe shutdown capability even if vulnerable buildingswere penetrated by a L
missile.
On a sample basis, the Licensee has demonstrated that all Seismic Category I structures are capable of withstanding en SSE in conformance with modern requirements. However, this demonstration does not extend to the g.,
' ("
simultaneous occurrence of SSE and LOCA. Although this is a requirement currently demanded of Seismic Category I structures in hazard, the Licensee takes the position that a postulated accident involving the simultaneous occurrence of SSE and LOCA is not appropriate for inclusion in the design basis for Millstone Unit 1.
In addition, the capability of structures to withstand the extreme environmental snow load identified in SEP Topic IIm2.A is not reported.
t
,a l-l I
i -, _... -. _.. -. -, -. -..
1 TER-C5506-436 7.
CONCLUSIONS AND RECOMMENDATIONS Northeast Nuclear Energy Company has submitted its appraisal of SEP Topic III-7.5 issues as they relate to the Millstone Unit 1 Nuclear Power Station.
The Licensee's submittals have been reviewed and, based on the assurances provided therein, many of the SEP Topic III-7.B issues of concern are considered resolved.
However, the submittals do not provide sufficient information to fully resolve all issues. As discussed individually in Section 6, these issues remain open:
Code Chances:
AISC 1.5.1.2.2 - Coped Beam Connections AISC 1.9.1.2 - Compression Elements with b/t Ratios ACI 7.10.3 - Columns with, Spliced Reinforcements Subject to Stress Reversals
Accident load cases requiring simultaneous consideration of SSE and LOCA o
Extreme environmental snow loads on roofs
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a TER-C5506-436 8.
REFERENCES Y.
1.
Franklin Research Center, Technical Evaluation Report Design Codes, Design Criteria, and Loading Combinations (SEP Topic III.7.B), Northeast Nuclear Energy Company, Millstone Point Nuclear Powe Plant Unit 1, TER-C5257-323 May 19, 1982
- 2. _" Specification for Design, Fabrication, and Erection of Structural Steel for Buildings," Sixth Edition American Institute of Steel Construction, Inc.
New York, NY
(
1963 3.
" Specification for Design, Fabrication, and Erection of Structural Steel for Buildings," Eighth Edition American Institute of Steel Construction, Inc.
New York, NY 1980 4.
" Code Requirements for Nuclear Safety,Related Concrete Structures" (ACI 349-76)
American Concrete Institute, Detroit, MI i
5.
" Building Code Requirements for Reinforced Concrete" (ACI 318-63)
American Concrete Institute, Detroit, MI 6.
ASME Boiler and Pressure Vessel Code,Section III, Division 2
" Code for Concrete Reactor Vessels and Containments" New York, NY 1980 i
7.
N111 stone Unit 1 Structural Reevaluation of Plant Structures to Address SEP Topic III-7.B Code Changes, Prepared by Impe11 Corporation, Report No. 02-0240-1150, Revision 0 i
December 1983 i.
8.
Impe11 Corporation, Calculation No. 24-08-001 12/16/83 9.
Impell Corporation, Calculation No. 24-08-002 12/16/03
- 10. Structural Analysis and Design of Nuclear Plant Facilities, ASCE Manuals and Reports on Engineering Practice No. 58 February 1962 1
- 11. FSAR, Amendment 13, Millstone Unit 1, Docket No. 50-245, Appendix D, prepared by General Electric Company with the assistance of EBASCO Services, Inc. _.
i TER-C5506-436
- 12. NCT Engineering, Inc., Report, " Systematic Evaluation Program Structural Review of the Millstone Unit 1 Nuclear Power Plant Drywell Containment Structure Under Combined Loads" April 1982
- 13. Millstone Unit 1 Reevaluation of Plant Structures to Address Structural Issues Raised Under SEP Topics II-3.B, III-2, and III-3.A, Prepared by Impell Corp.
January 1984 14.
Standard Review Plan NRC, Rev, 1, July 1981 NUREG-0800 (formerly NUREG-75/087)
E.
Letter, W. G. Counsil to D. M. Crutchfield, SEP Topic III-7.B, Design 4
Codes, Design Criteria and Load Combinations August 11, 1982 s
9 e
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