ML20127J539

Connecticut Yankee Structural Reevaluation of Plant Structures to Address SEP Topic III-7.B Load Combinations Code Changes

ML20127J539
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Site:	Haddam Neck File:Connecticut Yankee Atomic Power Co icon.png
Issue date:	11/30/1992
From:	HARSTEAD ENGINEERING ASSOCIATES, INC.
To:
Shared Package
ML20127J505	List: B14334, Forwards Rept, Connecticut Yankee Structural Reevaluation of Plant Structures to Address SEP Topic III-7.B Code Changes, Determining That All Structures Are Capable of Withstanding All Design Conditions Stipulated by SEP Topic ML20127J539
References
TASK-03-07.B, TASK-3-7.B, TASK-RR 9203-01, 9203-01-R00, 9203-1, 9203-1-R, NUDOCS 9301250169
Download: ML20127J539 (55)

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ll CONNECTICUT YANKEE

E STRUCTURAL REEVALUATION OF PLANT STRUCTURES TO ADDRESS SEP TOPIC III-7.B LOAD COMBINATIONS 4

CODE CHANCES j

Report No. 9203-01 Submitted to Northeast Utilities Service Company P.O.

Box 270 Hartford, Connecticut 06101 Prepared by HARSTEAD ENGINEERING ASSOCIATES, Inc.

Valley Office Park 180 Old Tappan Rd.

I Old Tappan, NJ 07675 November 1992 g

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I Report No. 9203-01 Revision 0 TABLE OF CONTENTS I

2.0 BACKGROUND

3.0 EXECUTIVE

SUMMARY

4.0 REEVALUATION, LOADS & LOAD COMBINATIONS 5.0 REEVALUATION, CODE CHANGES

6.0 CONCLUSION

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7.0 REFERENCES

FIGURES:

1-1 SITE PLAN OF CONNECTICUT YANKEE ATOMIC POWER PLANT, Figure 1, Ref.2 4-1 MEAN WINDSPEED FREQUENCY CYPLANT TARGETS, Figure 9.3-2, Ref.S APPENDICES:

A STRUCTURES AND LOAD COMBINATIONS REQUIRING REEVALUATION B - LOAD DEFINITIONS I

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Report No. 9203-01 Revision 0

1.0 INTRODUCTION

I A review and evaluation was undertaken of the safety related structures and structural components of the I

Connecticut Yankee Plant, Haddam Neck, CT. This review was required by NRC SEP Topic III-7.B,

" Design Codes, Design Criteria and Load Combinations-Haddam Neck", (TER-C257-319), prepared by Franklin Research Center (FRC),

(Ref.1).

I The Seismic Category I structures listed in Section 8 of Ref.

1, in which it was noted that the Turbine Building and the Radwaste Building were not classified as Seirmic Category I.

Seismic Category I structures as follows:

I containment Primary auxiliary building (including pipe gallery)

New and spent fuel building Control room and switchgear room in service building Diesel generator building Service water intake (screenwell house) and pump house Discharge structure.

The SEP effort compared the actual criteria used in the design of the plant and the then current (circa 1982)

I structural design criteria for the Seismic Category I structures at the time of the SEP. The objective was to determine the margins of safety to ultimate strength and the extent to which the design would meet the then existing criteria.

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I Report No. 9203-01 Revision 0 1.1 LOAD COMDINATIONS The purpose of this report is to document the results of a program of limited structural reevaluation of existing I

structures at Connecticut Yankee to resolve load and load combination issues raised by the NRC in their evaluation of SEP Topic III-7.B. The safety objective of this SEP I

topic is to assess the capability of all Seismic Category I structures to withstand all design loads and load combinations that may be imposed on the structures to a degree sufficient to assure that the plant can be safely-shut down. Current NRC requirements on loads and load combinations are defined in applicable sections of Standard Review Plan 3.8. These requirements were not in I

effect when Connecticut Yankeo was constructed and licensed.

I According to SEP III-7.B a comparison of loads indicates several loads which are not part of the original design which could have an effect upon the margin of safety and were ranked A, (Ref. 1) where A, is defined as requiring I

an assessment of the potential magnitude of the effect upon margins of safety:

LOADS STRUCTURE LOAD

1. Concrete Containment & Liner pipe reactions, R,, tornado W, I

2. Primary Auxiliary Building R,

W L Roof Loads

3. New and Spent Fuel Building R,

W,

4. Control Room and Switchgear None Room in Service Building identified I

5. Diesel Generator Building None identified I

6. Service Water Intake and W,

Pump House 7.

Discharge Structure W,,

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Pipe Gallery Containment I

i Structure p

I-P rlina ry Auxillary Building Auxillary Feedwater I

Pumphouse I

I Service Building New Diesel I

Generator Building' Turbine Building I

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I Office Building I

e screenwell House I'

h '. C. /' '.

- --. a I

' k,%

Connecticut River SITE PLAN OF COriNECTICUT YANKEE ATOMIC POWER ( Re f. 2 )

Figure 1-1 I

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I Report No. 9203-01 Revision 0 LOAD COMBINATIONS STRUCTURE LOAD COMBINATION Concrete Containment & Liner 7 & 14 Primary Auxiliary Building Concrete 10 & 13 Steel 8 & 11 New & Spent Fuel Building Concrete 10 & 13 Steel 8 & 11 Control Room Concrete 10 & 13 D.G.

Bldg.

NONE Service Water Intake Concrete 10 I

Steel 8

Discharge Structure Concrete 9,10 I

Note that the Auxiliary Feedwater Building and the New Switchgear Building are not listed in Reference 1.

I Modifications to the Auxiliary Feedwater Building have been proposed (Ref.12).

1.2 CODE CHANGES As part of this effort, the NRC conducted a comparative review of design codes in effect at the time of design of I

Connecticut Yankee with then current design codes.

The code changes were ranked according to their potential to alter perceived margins of safety. A total of 20 code changes were identified as -having the potential for I

impairing margins of safety. The NRC recommended that the impact of these code changes on plant structures be assessed. NUSCO committed to perform a limited I

reevaluation of structures for those code changes. The results of this structural reevaluation are described in this report.

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2.0 BACKGROUND

The Systematic Evaluation Program (SEP) was initiated by the Nuclear Regulatory Commission (NRC) to review the I

design of older operating nuclear power plants and to reconfirm and document their safety. The review compares the as-built design with current review criteria in I

different areas defined as " topics".

Topic III-7.B,

" Design Codes, Design Criteria and Load Combir.ations", is charged with the comparison of structural design criteria in ef fect in the late 1950's to the late 1960's (when SEP I

plants were constructed) with those in effect during the SEP, Other SEP topics also address other aspects of the integrity of plant structures. All these structurally I

oriented

tasks, taken

together, will assess the structural adequacy of the SEP plants with regard to current requirements.

The NRC has completed its review of submittals from Northeast Utilities in response to the use of a

probablistic approach to address Systematic Evaluation Program (SEP) Topics III-2 and III-4.A, Wind and Tornado Loadings and Tornado Missiles (TAC No. 51938). This was documented in a USNRC letter dated Oct. 21,1992 from Mr.

I Alan hang to Mr. John F.

Opeka (ref.9). An outline of modifications that would significantly reduce the tornado wind and missile hazard at the Haddam Neck site was I

provided to the USNRC in Reference 11. As a followup to the tornado wind and missile analysis CYAPCO now intends to implement significant modifications to its auxiliary feedwater system. An outline of these modifications was I

provided to the USNRC in Reference 12. CYAPCO is now updating the probablistic analysis to reflect these modifications and to develop a recommendation for the I

USNRC to resolve SEP Topics III-2 and III-4.A, wind and tornado loadings and tornado missiles.

The NRC considers SEP Topic III-6, Seismic Design I

Considerations to be closed. This was documented in a USNRC letter dated July 24, 1991 from Mr. Alan Wang to Mr. Edward J. Mroczka (Ref.10).

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Report No. 9203-01 Revision 0 3

2.1 LOAD COMBINATIONS In their SEP review of Topic III-7.B for Connecticut Yankee, the NRC retained Franklin Research Center (FRC) to conduct a comparison of load combinations used in the I

design of that plant with current criteria. For each structure, up to 14 load combinations were considered based on the appropriate SRP 3.8 criteria. These load I

combination requirements were not all in effect when Connecticut Yankee was designed. Consequently, other sets of load combinations were used. In comparing actual and I

current criteria, FRC attempted to match each of the load combinations actually considered to its nearest counterpart under present requirements. When deviations were found, FRC made c judgement (in the form of a scale I

ranking) on the potential impact of the deviation on perceived margins of safety. However, when the number of load combinations considered in the design was I

substantially fewer than curre?.'

2riteria require, only a

limited number of load cocinations were ranked (usually two).

I Selection of these cases were based on consideration that the most severe load combinations include accident and seismic or tornado loads. If demonstration of structural I

adequacy under the most severe load combinations currently specified for emergency and accident conditions is provided, a reasonable inference can be drawn that the structure is also adequate to sustain the less severe I

loadings associated with less severe consequences.

As a result of this study, FRC recommended that margins I

of safety of Seismic Category I structures under loads and load combinations corresponding to current criteria be reexamined. FRC identified the cases which they judged I

to have the potential to impair margins of safety (Scale A

or Scale Ax rating) as cases which should be reevaluated. Appendix A gives the list of structures and load combinations requiring reevaluation.

The load definitions used in this report are given in Appendix B.

The load combinations involve operating plus tornado load combinations and accident plus safe-shutdown earthquake I

combinations. The FRC did not recommend full reanalysis of all structures.

Hand calculations or appropriate modifications of existing results -were noted-as an I

acceptable means of demonstrating structural adequacy.

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Report flo. 9203-01 Revision 0 2.2 CODE CHANGES In their SEP review of Topic III-7.B for Connecticut Yankee, the NRC retained Franklin Research Contor (FRC) to conduct a comparison of design codes in offect at the time of design of that plant with current critoria. FRC performed a detailed comparison of the following old and current codes:

Codes used in the design:

AISC Manual of Stool Construction, 6th Edition, 1963 ACI 318-63 Building Code Requirements for Reinforced Concrote, 1963 Codes used in SEP Review:

AISC Manual of Stool Construction, 8th Edition, 1980 ACI 349-76 Codo Requirements for Nuclear Safety Related Concrete Structures, 1976 ASME Section III, Div.

2 Code for Concrete Reactor Vessels and Containments, 1980 I

3.0 EXECUTIVE

SUMMARY

3.1 LOADS AND LOAD COMBINATIONS The major differences betwoon Connecticut Yankee and I

later codes and SRP, are concerned with tornado loads.

The conclusion was that the lateral wind pressure loads were less than-tha SSE lateral seismic loads; therefore, I

load paths required for scismic loads would be more than adequate. Tornado pressure drops would be resisted by the reinforced concrete walls. Under tornado wind loads on structural steal portions, it was assumed that siding and roofing will blow off. The frame with bracing will remain intact.

I Tornado driven missiles were the greatest problem.

Scabbing, (inside face concreto spalling), could not be prevented for walls, less than about 18" for the heavier I.

pipe missiles. However, most of these walls are actually 7

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Report tio. 9203-01 Revision 0 I

shielded from missile strikes due to adjacent structures.

Using the tornado missile critoria for this plant (Ref.13),

it was concluded that all the reinforced concreto portions of the structures evaluated herein are adequate to resist tornado missiles.

The structural steel portions of buildings offer no I

tornado missile protection. The potential for tornado missile damages in structural stool portions is evaluated in SEp Topic III-2 and III-4a (Ref.11).

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I Report No. 9203-01 Revision 0 3.2 CODE CHANGES AISC, 1963 vs. AISC, 1980 I

This comparison was concerned with the structural steel design of Category I structures.

Item #1. b/t ratios. In fact only Tee sections depths greater than I

6W were affected by this code change, none of which were found on the Connecticut Yankee drawings.

I Item #2. Axially tension members. The net effect of code changes is that AISC 1963 is actually more conservative.

I Item #3. Coped flanges. Several beams were picked at random and stress evaluations were made. In every case, the beam connections were well within the new requirements.

I Item #4. Welded beam to Column Connections. No connections heavy enough to be affected by this requirement were found.

I Item #5. Bracing of Members at locations of Plastic Hinges. This change would only affect moment resisting frames with members in double curvature, a

situation which does not exist in the Connecticut Yankee design.

ACI 318-63 vs. ACI 349-76 I

This comparison was concerned with the reinforced concrete structures.

I Item #6. Brackets and corbels. The new requirement essentially affects those with ratios of span to depth between 0.5 and 1.0. For ratios above 1.0, the bracket would actually be a cantilever beam which of course was covered by ACI 318-63.

For ratios less than 0.5, minimum steel requirements are specified.

A review of the drawings indicates that all bracP.ets and corbels I

are heavily reinforced and need not rely on any capacity of the concrete section.

Item #7. Tangential shear in walls. The changes in minimum steel I

were compared to that provided by the Connecticut Yankee design.

The Connecticut Yankee design provides the required amount - of horizontal and vertical steel. Calculations indicated the applied I

seismic tangential shear was well below the capacities of the reinforced concrete walls.

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I Report !!o. 9203-al Revision 0 Item #8. Shear-friction. 130 situations were found.

Item #9, Reinforced concreto shell structuros with walls 12" or larger, llo such structuras woro found in Connecticut Yankoa. The Containment Structuro is not part of ACI 349-76, soo itomo 14-20).

Item #10. Thermal of fects. According to llRC SEp III-78, (Rof.1),

for structures not subject to effacts of pipo break accident, I

thermal stresses are unlikely to bo significant. Thorofore only local and temporary temperature limits are important only in structures subject to pipo break, ACI 349-76 allows 650' F.

It is not expected that concreto surfaces can be subjected to this I

temperature but oven if they woro it is unlikely that failuro due to thermal stresson could occur because of the self relieving nature of local thermal stresses.

Item #11. Variations in column stresses from f. in compression to

0. 5 f, or loss in tension. This situation co'uld only occur in I

reinforced concreto moment resisting framos subject high lateral unismic loads.

The Connecticut Yankoo reinforced concreto structural systcms for resisting lateral loads is by means of choar walls. With relatively small lateral displacements, such_ stress I.

roversals cannot occur in the reinforced concroto columns.

Item #12. Stool Embodmonts. A :oview of the anchor bolts indicatos I

that the Connecticut Yankco details conform to ACI 349-85. A numerical chock of the anchorage of lateral bracing indicatos considerable conservatism in the Connecticut Yankoo detail when compared to ACI 349.

Item #13.

Impulso and Impact.

While some exterior walls are susceptible to acabbing for the full Spectrum I missilos, thoso I

walls tend te be chiolded by adjacent structuros. According to liRC critoria it can be concluded that the reinforced concreto portions are adequato.

ASME III, Div. 2 vs. ACI 318-63 Item #14. Tangential shear. For soismic loading combined with dead I

load the concrote section capacity exceeds the applied shear. Under accident internal pressure as well as soismic and dead loading, the linor carrios the tangontial shear. This is at varianco with ASME I

III, Div. 2. Ilowever, the linor strength capacity was later used in many subacquent applications at other plants. If avertholoss, the con ~ rote walla can resist the tangential shear without the contribution of the steel linor.

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Items #15 & #16. Peripheral & Torsional Shear. For the Containment Structure under internal pressure, concrete capacity becomes academic and the additional reinforcing bars and additional robars local to discontinuity accommodates these local shear loads.

I Item #17. Short term thermal loading. Under accident conditions the liner could see 260* F. This is well below the allowable of about I

360*

F. The concrete is somewhat protected by the 3/8" liner:

nevertheless, for this condition 650' F would be allowed, which is in excess of expected local short term temperature.

Item #18. Development length in biaxial tension. Containment bars tend to be continuous except for added reinforcing at openings. A review of the drawings indicato development length would be no problem.

Item #19. Drackets & Corbels. tione were found on the reinforced concrete drawings.

Item #20. Liner and liner components. There is general conformance with AS!4E III, Div.

2, with the exception of the fact that the Connecticut Yankee design calls for the liner to resist seismic tangential shear. An independent study for the 11RC-11RR concluded that the liner system would perform satisfactorily and conforms to As!4E III, Div. 2 with the exception of a slight increase in stud deformation.

The original design and subsequent modification and strengthening I

has been evaluated and judged that the plant meets the additional requirements proposed by SEP in the areas of loads and load combinations as well as code changes.

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I Report No. 9203-01 Revision 0 4.0 REEVALUATION, LOAD COHDINATIONS Roovaluation shall be based on the Technical Evaluation Report (TER-652 57-319) by FRC (Franklin Roscarch Contor),

(Ref.1) and the roovaluation includes:

I a.

Comparo design codes employod at the timo of the original design to codos present during SEP.

b.

Generic codo versus codo compariscn without investigating how the original code was applied.

c. After review of the structures, cortain portions of the codos may not be applicable.

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d. Compara thu loads and loading combinations in the FSAR to thoso required at the timo of SEP or the present ovaluation, applicablo loading combinations have boon identitled for roovaluation.

4.1 GENERAL LOAD CONDINATIONS I

A limited structural roovaluation of existing structures and comments at Connecticut Yankoo was performed to address the load and load combination issues raised by I

the NRC in their ovaluation of SEP Topic III-7.B.

In accordance with Franklin Rascarch Contor's (FRC) recommendation, load combinations assigned a Scale A or i

Scalo A, ranking in their study (Ref.1) were considered.

Structural rcovaluations to current

loads, load combinations and acceptanco critoria woro performed on a sampling basis for the following structuros:

Subsequent to and in response to the NRC SEP review, URS/Blumo performed a

seismic review and published I

reports concerning their review and recommended structural modifications, " Seismic Roovaluations of Major Structures of the Connecticut Yankoo Atomic Power Plant",

1983, (Ref.2).

In response to NRC SEP Topic III-2, Wind and Tornado Loading, and Topic III-4.A, Tornado Missilos, (Ref.4), a I

tornado risk assessment was performed by Applied Roscarch Associates, Inc. in 1989, (Ref.5). This analysis is now being updated in order to evaluato anticipated on going

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Report No. 9203-01 Revision 0 plant modifications and to review modifications which I-have been determined to be significant in reducing the core malt frequency for the plant. This list has been submitted to the USNRC in Reference 12.

alRQQIURES AFFRQIED_D_Y_LQAQS_hND LOAD COMD_INATIO11g:

Affected Structures I

1 Containment Structure (Concrete) 2 Containment Structure (Steel Liner)

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Primary Auxiliary Building - Concrete Structure (including pipe gallery) 4 Primary Auxiliary Building - Steel Structure 5

1 New and Spent Fuel Building 6

Control Room and Switchgear Room 7

Diesel Generator Building Service Water Intake (screenwell house) and Pump House 8

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Discharge Structure 10 Waste Disposal Building LOADS The load combinations rccommended by FRC are:

I a) Normal operating loads and tornado loads.

I b) Accident loads are the bounding loading combination out of 14 per SRP recommended combinations and, if the structural integrity demonstrated are reasonable, an I

inference can be drawn that the structure is also adequate to sustain the less severe loadings associated with less severe consequences.

I Therefore, the scope was not required to be an extensive reanalysis of structures under all load combinations currently specifled. The loading combinations for each of I

the above structures in the current reevaluation program are the loading combinations that occur under operating and accident conditions associated with the greatest consequences to public health and safety.

Therefore, scope involves the review individually all seismic Category I structures by performing a simple hand I

computations to qualify as an acceptable means of demonstrating structural adequacy.

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I Report No. 9203-01 Revision 0 Load Definitions D

Dead Load

=

L Live Load

=

E OBE (Operating Basic Earthquake's Effect)

=

E'

=

SSE ( Safe Shutdown Earthquake's Effect)

P.

Pressure Load Due to Accident Conditions

=

(pipe break)

P, = P, Loads Due to Normal Operating Conditions a

R, o r R, =

Pipe Reactions Under Accident Conditions R,

Pipo Reactions During Start-Up, Operating,

=

and Shut Down Conditions T.

Temperature Effect Due to Postulated Pipo

=

Break and Including T, T.

The Effect of Temperature Transients Due to

=

Operating conditions W,

Wind Pressure, Differential Prosaure and

=

I Missiles due to tornado based upon total tornado wind speed of 315 mph. SRP 3.5.1.4 missile spectrum I; particularly the 1 inch steel rod and utility pole. Maximum pressure drop of 2 psi, (Ref2).

Y Jet Implingement Load Due to a Postulated

=

3 Pipe Break Missile Impact Load Due to Pipe Whip of a Y,

=

Postulated Pipe Break Y,

Loads Due to the Reaction of Broken Pipe

=

During a Postulated Break

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Report No. 9203-01 Revision 0 4.2 DTRUCTURES 4.2.1 CONTAINHENT STRUCTURE (Concrete)

Loading Combination (7)

D + L + p, + T, + R, + W, Loading Combination (14)

D + L + P, + T, + R, + E '

I The ovaluation of tornado missilos for the containment structuro has boon addressed in a separato document I

(Ref.13) and is not part of the scopo of this document.

In Ref.13, the NRC concluded that tornado missilos are not a concern for the containment structure.

From the above load combinations it is obvious that if the horizontal wind loading is less than the horizontal seismic loading, the containment structure is capable of I

resisting tornado wind loads. Calculations were mado comparing the baco shears, as follows:

Tornado Seismic Base Shear (kips) 2212 14918 The tornado wind pressure was based upon 315 mph; however, it is obvious that the containment structure is adequato for 360 mph (Ref.14).

The maximum pressure drop of 2 psi is trivial in that the design accident pressuro la about 20 timos this value.

The only two loads considered as A, are R. (Pipo reactions under accident conditions) and W, (tornado wind pressuro, tornado --created differential pressure, and tornado generated missiles).

The load R is in combination with P,, accident pressure, I

and E' (SSE). The load R, is caused by thermal growth. A review of the CB&I pipe penetration drawings indicates that pipe passes through a sleevo in the 4'-6" vall. The I

pipe is wolded to a fuel heat which is in turn volded to the ombedded alcovo. Those pipo reactions could not lead to failuro for throo reasons:

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1. The thormal load is self relieving;

2. The 4 '-6" heavily reinforced concreto wall has a high capability of accommodating those pipo I

reaction loads. The S&W concroto drawing indicatos extensivo additional reinforcing and U bars were used to resist lateral forces at all panotrations (DWG 16103-50086, FC-35G).

3. The offects of local loading damps out as the distance from the panotration increases.

I The pipo can introduce radial forces, bonding moments about the horizontal and vertical axos, and torsion I

moments about the radial axis. Such loading is limited by the clastic strength of the pipe itself.

I A calculation was mado concerning the 42 inch diamator ponotration located on the containment wall at EL.

25'-

9". The capacity of the reinforced concreto Wall to resist local forces and moments was restricted to only I

the additional diagonal bars. Local bending was resisted by using diagonals on the insido and outsido surfaces.

Shear forcos are resisted by the mid-dopth diagonals acting in shear friction.

Using reinforced concreto capacities as described above the following capacitics have boon calculated:

Type of capacity L9Atling Mannitude Radial 23700 kips Moment 41500 ft-kips Torque 27440 ft-kips i

The above capacities are used to datormino the thickness of main steam (conservatively assumed to 36 inch diameter) necessary to develop the plastic moments and forces to the levels of the reinforced concreto as follows:

Equivalent LgAd Thickness of Pipo i

Radial 6"

l Moment 8"

Torque 11" 16 I

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The equivalent thickness is that which would be necosuary to yield the plastic moments and forcos which would exccod the local capacity of the chull.

I It is obvious that the capacity of the reinforced concreto exceeds the plastic piping loads by very wido margins. Thorofore, no local failuro can occur duo to I

penetration forces and moments. Since the offects are local and are resisted by additional diagonal reinf orcing bars, thoro will be no diminution of overall strength in resisting internal proscuros and poismic forces.

Thororcro, Load Combination #7 is less savoro than Load Combination #14 and Load Combination #14 is satisfied in I

that with the exception of R,,

Load combination #14 has boon previously satisfied, (Ref.3).

It was demonctrated the R, is a local load which cannot possibly result in local failure.

The containment structuro is supported by a 6"

bed of loan concreto on rock. The allowable bearing of the rock under normal loading ja 20 kaf. The normal bearing is about 10 kaf; so even with poismic loads the peak bearing stress will be under the normal allowable bearing. Under I

soismic loads the allowablo rock bearing could bo establiahod at much greator values then 20 ksf. 20 kof corresponds to 144 psi. This is a very low requiremont for loan concreto.

I 4.2.2 Containment Structure (Steel Liner)

Loading Combination (7)

D + L + P, + T, +

R,, + W, Loading Combination (14)

D + L + P. - + T, + R, + E '

Demonstrate that the Loading Combination (7) is less I

critical than Loading Combination (14),

except for tornado missiles hitting and puncturing the liner, and thus jeopardizing the integrity of leak barrior.

The containment etructure is fully protected against tornado missilos as noted in Ref.13.

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I Report 110. 9203-01 Revision 0 Due to the relativo stiffnossos of the stool liner and the concreto shell, the stool linor, in general, goes along for the rido. According to UFSAR the linor can be rolled upon to carry tangential shear. In reality the actual shear will be carried partially by both structural I

systems, so that, the most cignificant point in that the seismic baco shear exceeds the tornado base shear.

I The stool linor is in reality not required to carry any primary loads. The containment reinforced concrete wall is 4'-6" thick and heavily reinforcod. This means that tornado missiles will not have any significant offect.

I Even though it la claimed that the stool is designed for tangontial shear (Ref.8),

in reality the rainforced concrete will actually carry the major portion of the I

tangential shear caused by E' and We Thorofore, the Load Combinations #7 and /14 are satistiod.

4.2.3 PRIMARY AUXILIARY DUILDING (Concrete)

Loading Combination (10)

D+ L +

R,, + W, Loading Combination (13)

D + L + T, + P, + R, + E ' + Y, + Yj + Y.

The following structural analysis shall be performed to demonstrate that the PAD moots the above load combination requirements.

Load Load Cn g Combination S.t;ructu re 1

(10) a) PAD north wall olevation between 21'-

6" and 35'-6".

A critical wall panel shall be selected for the I

roovaluation. The approach shall be performing a strength ovaluation of the wall element for the reinforcement I

provided.

Dotormino equivalent negative pressure and the corresponding wind spood.

If I

necessary, determine the wind spood excoodence frequency by using the probability curve.

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(10) a) Chock a wall for overall wind shear I

in the plano of the wall due to the projected tributary sail area of_the orthogonal wall.

b) Check the stability against overturning moment-(OT).

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(13) a) Assoas offects of Y, + Yj + Y, f o r pipe whips and jot offects.

I b) Effect of E' along with other loads has boon ovaluated por SEP III-6 and shall be considered if it is an I

additivo.

The Primary Auxiliary Building is a reinforced concreto structure up to Elevation 35'-6". Abovo Elevation 3 5 '-6",

I the structuro is structural stool framing, except for two concreto structuras which houso ducts and the volume control tank. Under tornado wind the exterior siding I

blows off, leaving the two structures as "ponthouses" abovo El.

35'-6".

The shear in kipu at El.

21'-6" is NS EW Tornado 999 481 Seismic 3370 3510 The above comparison in based upon a total 315 mph tornado wind (Ref.2). It is clear that tornado wind I

pressure offects are much loss than horizontal seismic offects.

I The individual "ponthouses" would be subjected to the offects of pressure drop and wind prosauro. The worct case of the following:

W = W + 0. 5 W, W, = W + W.

W, = - W, + 0. 5 W, + W, I

The above equations are given in the NRC Standard Review Plan (SRP) NUREG 0800, Section 3.3.2-3, (Ref.6).

I 19 I

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I Report fio. 9203-01 Revision 0 The penthouse housing the duct opening would survivo the iI ef f ects of wind pressure and pressure drop. However it is doubtful that the wall would not be penetrated by a tornado missile in combination with the pressure loads.

The penthouse housing the Volume Control Tank has very thick walls, at least 2 '-6". Thereforo, these walls would survive the pressure and missile effects of the tornado.

The reinforced concrete north wall, with thicknesses of I

l ' -6" a nd 2 ' -0", possesses sufficient strength to resist the tornado pressure and missile loads.

According to the 11RC staf f evaluation of the reinforced concrete walls up to El.

2)'-6" provide acceptable tornado missile protection (Ref.13). The flRC staff also found that the reinforced concreto portions of the PAB I

are adequate to withstand the design tornado loads, (Ref.14).

g The 12" walls at the duct opening above El. 35'-6" would g

be susceptible to the 12" pipe missile; but in reality these walle are surrounded by structural stool framing and interior partitions which would mean that in reality the normal strike of a tornado missile would be highly

(

unlikely just due to the sequence of events that would bo l

required.

lievertheless, for the 11RC required missiles Ref.13, the walls are adequato.

Inasmuch as the tornado wind pressure is much less the E' and the tornado missiles are not capable of causing failure it is clear that Load Combination #10 is satisfied. The Primary Auxiliary Building exterior wallr.

have shown capable of resisting tornado wind pressures and pressure differentials which woro based upon:

W + 0. 5W, For the Primary Auxiliary Building this is conservatively assumed to be about 345 psf. This exceeds an expected accident pressure f rom pipe break of about 0.75 psi which is equivalent to about 100 psf.

20

I Report No. 9203-01 Revision 0 According to the NRC staff evaluation, the reinforced I

concreto portions of the PAD are adequate to withstand the design tornado loads (Ref.14).

g 5

The other impact and impulco of fect of pipo break Y + Y, 3

+

Y, are not significant due to small diamotor high energy pipes which are present in the PAB. Thorofore, sinco tornado missiles are not likely cause failure, it I

can logically bo inferred that Y, + Y, + Y, will not cause failure.

I The PAB is supported on rock. There is no doubt that rock has the capability to withstand the bearing proscuros from load combinations 10 and 13.

Thorofore, Load Combinations #10 and #13 are satisfied.

4.2.4 PRIMARY AUXILIARY DUILDING - (Steel) a) The top portion of the PAB consists of a single story I

stool superstructure starting from Elevation 35'-6" to 53'-6". The walls and the roof is of a stool framing with metal docking, b) The original design requirements for tornado loads are that the metal siding is designed to blow out and the framing would remain intact due to oversized connections.

c) Design was also performed on the superstructure to I

maintain structural integrity under seismic (SSE) requirements.

The loading combinations proposed by FRC to review its I

integrity are the following:

Loading Combination (8)

D + L + R, + W, Loading Combination (11)

D + L + T, + P, + R, + Yj + Y, + Y, In order to assoas the ability of the building to withstand the above loading combinations, the following critical olomonts shall be investigated.

21 I

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Report No. 9203-01 Revision 0 a) A stool roof beam.

b) The stool framing including bracing.

c) For the roof slab, a beam (stool) shall bo selected for roovaluation to verify that those structural olomont capablo of withstanding loads due to ponding.

The voight on the member (pof) shall be based on the water weight equal to the parapot height of the structuro.

I A review of the drawings indicatos that thoro are 4" high curbs along the North and South edges of the roof 9 El 35'-6". Thora doesn't appear to be similar curbs I

along the East and West edges of the roof. The ponding is insignificant. This was confirmed by further review of drawings. If, in fact, 4" of water can stand on the roof, this will represent about 21 psf. The snow load excoods I

20 paf. Thorofore, this load is insignificant on two counts.

I Under tornado wind the Galbosto siding will blow off, leaving the exposed structural stool columns and beams.

The exposed structural stool framing is subjected to wind I

pressures after the siding has blown off. The projected area of the beams and columns is small, so even using a drag coofficient of 2.0, the latoral tornado wind chear is significantly less than the lateral seismic force.

I Even conservatively assuming a drag coefficient of 2.0 the lateral shears due to tornado wind are significantly loss than the soismic shears for which the structure has I

boon datormined to be capable _of; namely, 1424 ind.1733 kips in the north-south and east-west directions, respectively.

Under tornado winds, lift pressures will develop on the roof. A very light roof beam 14B26 was selected. Even assuming that roof does not blow off, the maximum beam stress will not yield stress.

I In the NRC staff ovaluation, two roof _ beams (14B22 and 12WF27) and a column W8x24 Wore considered to fail (Ref.14). llovever, the above was based upon the roofing and siding remaining intact. Wind loads cause uplift on I

flat roofs, in this caso stool dock roofing, the roof would be blown away beforo significant uplif t loads were imposed upon the structural steel beams.

It is; therefore, more realistic to assume that the siding and 22 I

I

a Report No. 9203-01 g

Revision 0 roofing will be blown

away, thereby reducing wind I

pressure and differential pressures on the structural steel frame.

I Therefore, Load Combinations 8 and 11 are satisfied.

4.2.5 NEW AND SPENT FUEL DUILDING Not an SEp III-7.B programmed structure (Ref.1).

I 4.2.6 CONTROL ROOM AND DWITCl! GEAR ROOM I

a) The Switchgear Room extends from Column Line (8) to (12) and (D) to (F). It is a steel framed structure I-with netal aiding for walls. The floor is on steel framing and metal docking topped with concrete slab at Elevation 41

'-6".

The roof of the Switchgear Room is the floor of the Control Room having a 14 inch thick concrete slab on steel framing. The Switchgear Room walls are not I

missile protected. The framing of the structure is designed for tornado Wind pressure to remain intact and prevent it from collapse.

The following loading combinations are required to be reviewed for the Switchgear Room:

Loading Combination (10)

D + L + W, Loading Combination (13)

D + L + T. + P, + E ' + Y, + Yj +

Y,,

Reevaluation -Approach The following shall be satisfied to demonstrate that the Switchgear Room I

meets the above loading combination requirement:

I I

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Report flo. 9203-01 Revision 0 Load Load Cagg Canblnation Structure 1

(10) a) Wall siding is assumed based on I

its design to blow off and the wind prosauro on the bracing system and the corapression /tonsion forces on the column (ll-E corner and S-E I

cornor) shall be ovaluated by taking the load path offect of wind pressure on the control room walls I

above the switchgoar room.

2 (10)

Evaluate the lateral shear strength capability of the walls of I

the braced framo system to transfer inplano shear force from the roof level to the foundation lovol.

Determino the wind speed its 3

corresponding wind speed exceedence 5

frequency of the braced system by using the probability curve.

3 (13)

Assess offects of loading due to E'

+

Y,

+ Y

+

Y, including tho equipment rea,ctions and the offect of piping loads.

b) The control room's walls and roof are about 22" thick.

I The building extends from Column Line (12) to 10' south of Column Lino (10) in 11-S direction. In E-W direction, it extends from (c) lino to (f) lino. The floor slab is located at Elevation 59'-6".

The roof is at Elevation 70'-6".

The structure is missile protected by design.

I Load Load Caso combination sinicturo I

4 (10)

Select a wall panel for the roovaluation. The approach shall be by performing a strength ovaluation of the wall olomont for the I

reinforcement provided in the out-of-plano direction. Determine the equivalent negativo prosauro and I

the corresponding wind speed. Then datormine the wind speed exceedence frequency from the probability 1

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Report flo. 9203-01 Povision 0 curve.

5 (10)

Perform overall lateral shear on tha structuro in N-S and E-W I

direction due to W,. If shear due to W,

s E'

then the structural integrity is justified por SEP Topic III-6 or provido roovaluation.

6 (13)

Assoas loads duo to E' + Y, + Y +

I 3

Y, due to piping supports or equipment support loads.

I 7

(13)

The structure has boon checked for its integrity for D + L +

E'.

Anness the of fect due to P and T,.

I 8

Ponding The roof's structural components Effect have boon designed for 40 psf on Roof live load in the original design.

I The prosent roovaluation shall includo datormination of weight of the water of a depth equal to the parapet height.

If this load is greater than 40

psf, ovaluato capacity.

I In the present roovaluation, it was dotermined that sciamic shoars at the base of the Control Room are 929 kips and 826 kips in the north-south and cast-wont I

directions, respectively.

This comparos with tornado ahears of 475 kips and 354 kips in the north-south and east-west directions respectively. The south wall was chocked for the latoral wind pressures including the I

offects of the pronouro drop. This wall assuming one way action was found to be capable of resisting the wind pressure loads. The east and north walls are heavior and I

therefore have greator capability. The west wall as well the east wall can resist wind pressures-as two way as alaba; thereby, greatly increasing the~ capacity of the wall than would be the case with one way action.

The capability of the switchgoar structure to resist the overall tornado wind loading was confirmed by comparing I

the shears resulting from tornado and earthquake. The basa shear introduced to the structural steel framing from tornado is only about 1/2 of that from soismic I

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Report No. 9203-01 Revision 0 I

loading. This fact coupled with the assumption that the metal exterior siding of the switchgoar room below blows off, indicates that the tornado loading will result is loss stress in the structural stool than the seismic loading.

local offocts of the tornado wind and pressure drop The I

were evaluated for the south wall with a thickness of l'-

8". This wall has reservo capacity to rosist tornado missiles in combination with the tornado pressuros. The l

cast and west walls are heavior and the west wall can act as a two way slab. Thoroforo, the control Room has the capability to resist tornado loading.

I According to the !!RC staff evaluation, the reinforced concreto control room is adoquately protected from tornado missiles (Ref.13).

The structural drawings of the Control Building do not indicato any parapets or curbs on the roof. The only curbs are located around the opening for the elevator I

shaft. The absence of curbs was datormined by reviewing the concreto drawings. The design roof livo load of 40 paf is equivalent to a depth of almost 8"

of water.

Thorofore, ponding has no offect.

Thoroforo, Load Combination #10 is satisfied sinco % is-a loss severo load than E. In Load Combination #13 T, is l

a self-relievir.g load. The exterior reinforced concrete walls and roof slab, capable of withstanding tornado wind pressures and pressure differentials would have no I

problem in resisting any internal accident pressure even though the possibility of such pressure is minimal. The capability of the walls and roof slab in withstanding I

tornado missilos means that any internal missiles resulting f rom small diamotor pipes would have negligible offects.

The reinforced concreto control Room has capability to resist wind pressures and pressure drop and it also has capability to resist internal prosauros, particularly in light of the openings prosent in the wall. P, and the impulsivo loads which are applicable to the structure (ref. SEP III-7.B).

According to the NRC staff evaluation, reinforced I

concrete walls and roof slabs, as well as the supporting structural steel bracing, are adequate to withstand the design tornado pressure loads (Ref.14).

I 26 I

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Report Ho. 9203-01 Revision 0 The service building, of which the control room and I

switchgear room are part, is typically founded on rock.

Thoroforo, the rock can easily withstand the boaring stressos resulting from load combinations #10 and #13.

In summary, Load combinations #10 and #13 are considered satisfied.

I 4.2.7 DIESEL GENERATOR DUILDING (new)

I The Diosol Conorator Building was an addition to the plant. The soismic analysis performed by S&W Engineering I

Corporation which conforms to Rog. Guido 1.60 (spectrum) and 1.61 (damping) normalized to 0.17g carthquake. The structure also designed for tornado wind of velocity 360 mph (W,). Thorot'oro, the now Diosol Generator Building _ is I

not rolovant to SEP Topic III-7.D. However, ponding of water on the roof slab was checked for loads due to the water height equal to the height of the parapot wall.

The roof with 6" high parapets, has a drainage system.

Assuming that the drainage piping becomes clogged, the I

averago woight of water would equal 47 puf. This slightly exceeds the live load (snow) of 40 psf. Even the total livo load of 40 psf is only 2% of the flexural capacity of the roof slab. Thoroforo, ponding is negligible.

4.2.8 SERVICE WATER INTAKE (Screenvell House and Pumphouse)

The intake structure consists of a two story concreto structure from Elevation-18'-0" to Elevation 218-6" and a one story structural stool frama from Elevation 218-6" to Elevation 35'-6".

Tho grado is at Elevation 21'-6".

The walls of the stool framed structure consist of insulated Galbesto siding on steel framing.

The concreto portion of the structure is below grado I

level on throa sides and one sido is exposed to the river. The wind pressure due to W, from that direction has little offect on the structure.

I Thorofore, it is judged that the W, affect on the stool structure shall be evaluated and its offect on concreto elements below grado level shall be determined.

27 I

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I Report No. 9203-01 Revision 0 I

For roovaluation, the following loading combinations have boon rticommended:

a) Concreto:

I Loading Combination (10)

D + L + R, + W, b) Stool:

Loading Combination (8)

D + L + W, Under tornado loading, the structure is assumed based on its design to blow off by and the framing shall remain intact during the ovent.

Thoroforo, ovaluato a) Lateral shear on the framing in both E-W and N-S direction, b) Check stool framing for their strength to resist the abovo loads.

I c) Carry the horizontal shear below Elevation 21'-6" to the concroto structure and confirm that the I

olomonts would withstand the forces due to W,.

d) Check a horizontal beam at Elevation 35'-6" for loads due to ponding of water to a depth equal to the parapet wall height.

This structuro is also known as the Scroonwell House I.

and Pumphouse. The reinforced concreto portion of the structure extends from the foundation at El.-18'-0" to El.

21'-6".

One side faces the river while the opposite side is below grado. The side walls are I

partially exposed sinco grado extends diagonally from the back and to the river level. Based upon this configuration and the thickness of the walls, the I

reinforced concreto portion can withstand the tornado winds and missilos. Pressure drop loads would not develop due to soveral floor slab oponings. Thorofore, load combination #10 is satisfied.

Tho-scroonwell building is supported by loan concrote over bedrock. The bearing stressos resulting from load I

combination 10 will be well below the capability of the rock.

I 28 lI

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Report No. 9203-01 Rovision 0 Tho structural stool portion is supported by the I

reinforced concreto._

Under tornado

winds, the corrugated stool niding blows off.

The remaining structural stool framing is subjected to wind I

pronouro. Conservatively using drag coefficients of 2.0, the base chears resulting from the tornado wind prosaura were found to be about one half of the coinmic base shears. Thoroforo, the structure was I

found to be capablo of withstanding the tornado loads, and load combination #8 is satisfied.

I According to the NRC ovaluation, the siding of the acroonwoll house will bo blown off under tornado winda (Ref.14). Thorofore, the motors of the service water pumpo will bo expocod to tornado missilos (Ref.13).

This losuo la being addressed as part of SEp Topic III-2 and III-4A (Ref.11).

I The roof la about 1/2 hatch and vont openings. In the event the drainage piping becamo clogged, tha coverago depth of water would bo 6".

Tho load of 31 pot is I

about the design livo load of 30 psf. Thorofore, thoro is no problem.

4.2.9 DISCHARGE TUNNEL STRUCTURE Loading Combination recommended for review:

Loading Combination (9) D + L + E' Loading Combination (10) D+L+W.

Since the tunnel runa below grado lovel, Loading Combination (10) is not applicable.

a) Evaluate the structuro under solomic loads, E'.

I The dischargo tunnel is below grado and; thorofore, is not nuaceptible to tornado offects.

Tho tunnel is rectangular in cross section with thick

walls, base and roof.

Structurally the tunnel acta laterally as a rigid framo. The tunnel is located in a tronch dug into rock. The sidos are backfilled. With thin I

configuration, the maximum acceleration at the base would be limited to the ground accoloration. Furthermore the backfill would tend to mitigate the rolatively low I

29 I

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Report flo. 9203-01 Revision 0 solamic input.

4.2.10 WASTE DIDPOSAL DUILDING This structure is not part of the structures to reviewed por SEp topics.

I I

I I

I I

I

'I I

I 1I I

30 I

il ' I l*jq4 e j i j,; < j..jij;ji,

i 6

i g

I Coreltlcut Yank ee Plgt I

P1 ant Target g.:

I i

=

~

l t,

• 1

~

\\

7

~

_~

l-D C

I,.

o

+

g

~

I m

w e

y I

j w

E it - 5 w

b E

{

l a

c,

?

i 4

I n-s E

I n-1 I

I l1 lt l1 lt ilililili i l1I rli!i tiiilii-

iiiliit, I

1 g.:

I e,

Windspeed Vj' (mph)

Mean Windspeed Frequency - CY Plant Targets Figure 4-1 31 I

_..,._m.._.

. _. ~. _ _...

I I

Report No. 9203-01 Revision 0 5.0 REEVALUATION, CODE CHANGES Each of the 20 code change items identified by Franklin Research Center as needing further investigation will be I

listed below along with the evaluation for each item. The 5 AISC items will be listed first, followed by the 8 ACI items and the 7 ASME D&PV items.

AISC CODE CRITERIA CHANGES Between 1963 and 1980 ITEM #1 1980 - Section 1.9.1.2 App. C 1963 - 1.9.1 Structural elements affected:

Slender compression unstif fened elements subject to axial I

compression or compression due to bending when actual width-to thickness ratio exceeds the values specifled in subsection 1.9.1.2.

According to Case Study 10 (Ref.2, SEP III-7.B), the 1963 code is more conservative for single and double angles, and other situations except for the stems of Tee sections, when (L/t) > 25.0.

For Tees ST-W6 and smaller, AISC 1963 is not more I

conservative than AISC 1980, because for those ST's (L/t) < 25.0.

I Structural steel drawings of the Control

Building, Auxiliary Feedwater Pumphouse, Reactor Containment Building, and Primary Auxiliary Building were reviewed.

I ST W's with depths greater than 6" were not found on the above structures.

Nevertheless, the b/t ratios were checked and, where I

loads were available, the compressive stresses were calculated. In all cases the requirements of the 1980 code were met.

THE DESIGN OF CONNECTICUT YANKEE MEETS THE UPDATED CRITERIA i

I 32 I

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Report lio. 9203-01 Revision 0 ITEM #2 1980 - Section 1.14.2.2 1963 - flo requirement Structural elements affected:

Axially loaded tension members where the load is I

transmitted by bolts or rivets through some but not all of the cross sectional elements of the member.

Allowable tensile stress on not section, F,: (1.5.1.1) 1963 1980 0.6 F, 0.5 F.

The ratio of allowable stresses on the not section for A36 steel is:

21.6/29.0 = 0.744 1

The values of the reduction factor C,

(AISC 1980) indicato valuns from 0.75 to 0.90.

The difference in allowable stresses, higher allowables for 1980, means I

that AISC 1963 is no loss conservative than AISC 1980. In fact, for all but connections with two fasteners in lino, AISC 1963 is significantly more conservativo, when values of C,are 0.85 and 0.90.

L EFFECTIVE ALLOWABLE STRESS

• I (ksi)

AISC AISC 1980 1963 Ct I

0.90 26.1 21.9 0.85 24.7 21.9 0.75 21.8 21.9

• The offectivo allowable stress is the total axial load divided by the not area, A,. For A36 stool F, a 36 ksi, F, = 5 8 ka i.

I AISC 1980 did impose an added check on gross section of 0.6F This in obviously less conservative than AISC 1963 I.

whic5). imposes the same stress allowable but on the not section as described above.

I 33 I

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I Report 110. 9203-01 Revision o Tile DESIGli OF CollllECTICUT YAllKEE MEETS TiiE UPDATED CRITERIA ITEM #3 1980 - Section 1.5.1.2.2 1963 - fio requiremont Coped flanges at beam connections.

Structural olomonta affectod!

Beam and connection where the top flange la coped and subject to ahear, or failuro by choar along a plane I

through factoners or by a combination of shear along a plano through factonora plus tension along a

perpendicular.

Check shear along a plano through fauteaura or a

combination of chear along a plano through factonoru plus I

tonnion along a perpendicular plano on the area resisting tearing failuro.

The allowablo otroas = 0.3 P,=

17.4 kal por code I

Structural stool drawinga of the Scroonwell liouso,

Control Building, and Primary Auxiliary Building woro I

reviewed.

An ovaluation was based upon the maximum allowable loada and standard framed beam connections according to AISC, 1963.

Rouults are ao follows:

Scroonwell Deam Strons (kai)

W10X25 11.2 WdX17 11.4 Service Puilding W24X68 7.0

_g W21X55 6.3 5

"16x40 7.1 WlaX50

.7.2 l

W27X94 9.8 i

W16X36.

10.7 l

812X16.5 7.7 I

34 I

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Report 110, 9203-01 Revision 0 PAB B

B14X26 4.8 B8X10 7.7 W12X27 8.6 Based upon conservative calculations the actual stresses in the beam are much less than the allowable stress.

Furthermore, according to AISC 1980, commentary, the tension allowable is 0.5F,. The use of 0.3F, in the web region subject to tension is, thereforo, an additional conservatism.

Tile DESIG!l OF C0!illECTICUT YAlfKEE MEETS THE UPDATED CRITERIA ITEM #4 1980 - Section 1.15.5.2 1963 - 11o requirement Structural elements affected:

Restrained members when flange or moment connection plates for end connections of beams and girders aro welded to the flange of I or 11 shaped columns.

Moment connections in which flange or connection plates I

are wolded to the flango of I or 11 columns. Column web stiffeners are required when the force exceeds certain values. This requiremont comes into play when the forco g

is very largo. This would indicate substantial moment

~

g connections. A review of the structural steel dravings indicates that moment connections woro not detailed.

In general, lateral loads were designed to be resisted by I

bracing rather than moment resisting frames with moment connections.

I Tile DESIGN OF CON!iECTICUT YANKEE MEETS THE UPDATED CRITFRIA I

I I

35 I

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Report tio. 9203-01 Revision 0 ITEM #5 1980 2.9 1963 2.8 Lateral bracing of membora to resist lateral and torsional displacement.

Structural olomonts affectod:

Isracing of members at locations of plastic hingos.

I According to AISC 1980 those provisions nood not apply to the last hingo to form. According to Caso Study 7 (SEP III-7.B), AISC 1980 10 only more conservativo when then member in subjected to reverso curvature, O < M/!4 < l. 0.

Hoverso curvature is associated with moment resisting framos subject to lateral loads. The structural stool I

drawings indicato that neither moment resisting framos woro employed, nor woro plastic design methods employed.-

I T!!E DESIGil 0F C0!!!iECTICUT YAtlKEE MEETS Tile UPDATED CRITERIA ACI CODE CilAllGES, ACI 318-63 to ACI 349-76 ITEM #6 Special Provisions for Brackets & Corbels.

ACI 349 Section 11.13 ACI 318 tio requirement I.

Structural olomonts affectod:

Short brackets and corbols which are primary load-carrying members.

These provisions apply when the shear span to depth ratio, a/d = 1.0 or loss. When a/d = 0.5 or loss, the I

provisions for walls apply, (11.15). When a/d excoods 1.0, the bracket would bo treated as a cantilover beam in which caso ACI 318-63 is conservativo. For each version I

of the code, other than 0.5 < a/d < 1.0,_the allowablo shear stress would be about the same. A review of the reinforced concreto drawing indicate that most brackets I

36 I

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I Report flo. 9203-01 Revision 0 I

fall outsido the requirements of ACI 349-76, section 11.13. One bracket on the south end of the east wall of the Scroonwell llouce would fall under 11.13 ACI 349-76.

Ilowever this bracket in very heavily reinforcing bars and I

very 1ikely does not rely on any shear strength of concreto.

I For a/d 1.0, the bracket becomes, in effect, a

cant 11over beam which is of courso covered in ACI 318-63.

For a/d < 0.5, ACI 349-76 11.15 applios. For d = 1/2 1,,

the allowable concrote shear stress por ACI 349-76 I

excoods the allowables por ACI 318-63 which would be based upon shour as a measure of diagonal tension and henco very conservativo.

Tile DESIGli OF C0!!!!ECTICUT YAlmEE MEETS Tile UPDAfED CRITERIA I

ITEM #7 ACI 349 - 76: Section 11.15 ACI 318-63: flo requiromont structural olomonts affected:

All structural walls those which are primary load

carrying, e.g.,

shear walls and those which serve to I

provido protection from impacts of missilo type objects.

Under seismic conditions, the shear walls at Connecticut I

Yankoo are not subject to axial tencion. This is so because the vertical accoloration would not exceed 1.0g.

I Thoroforo, the shear requirements of ACI 349-76, 11.15 would reduco to at least 2.0 Vf',.

The quantity of shear reinforcing stool provided by ACI 318-63 would moot or execed that required by ACI 349-76.

I Comparison of minimum ratios of reinforcing.

ACI 349-76 ACI 318-63 p,

0.0025 0.0025 p,

0.0025 0.0015 I

37 I

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I

.I Report No. 9203-01 Revision 0 Therefore, ACI 349-76 is more conservative for minimum

_ q steel in the vertical direction.

In order to assess the minimum steel requiroments, the I

reinforced concrete drawings of the Screenwell House, the Control Building, the Primary Auxiliary Building, and the Discharge Tunnel were reviewed. A total of 15 walls were checked. In all cases, the walls at Connecticut Yankee I

have ratios of reinforcement all within the minimum requirements of ACI 349-76.

I Shear stresses for the critical shear walls were calculated using the seismic shear forces 'from the Blume seismic Analysis.

Wall Shuar Stress Shear Stress Applied (psi)

Allowable (psi)

Control Building South 33 180+

West 41 180+

East 34 227 Primary Auxiliary Building East & W:

125 223 I

The walls of Connecticut Yankee would; therefore meet the requirements of ACI 349-8S.

For missile impacts see ITE.M #13 I

THE DESIGN OF CONNECTICUT YANKEE MEETS THE UPDATED CRITERIA ITEM #8 ACI 349-76: 11.14 I

ACI 318-63: No requirement Shear-friction. Reinforcing perpendicular to shear plane.

Structural elements affected-Elemtents loaded in shear where it is 38 I

t

I Report No. 9203-01 Revision o inappropriate to consider shear as a measure of diagonal I

tension and the loading could induce direct shear type cracks.

Since 318-63 had no provisions for shear-friction, the I

designers at that time would have used techniques, such as Mohr's circle, to calculate principal stresses. With this information reinforcing would have been determined.

However, no cases of shear friction were found after a review of the Reinforced Concrete Drawings.

THE DESIGN OF CONNECTICUT YANKEE MEETS THE UPDATED CRITERIA ITEM #9 ACI 349-76 Chapter 19 ACI 318-63: No requirement Reinforced Concrete Shell Structures Structural elements affected:

I Shell structures with thickness equal to or greater than 12".

I After a review of the reinforced concreto drawings, no shell structures with thicknesses greater than 12" were identified.

THE DESIGN OF CONNECTICUT YANKEE MEETS THE UPDATED CRITERIA I

ITEM #10 ACI 349-76, Appendix A ACI 318-63: No requirement Structural elements affected:

All elements subject to time-dependent and position-dependent temperature variations and restrained so that thermal strains will result in thermal stresses.

The most obvious structure subjected: to temperature I

ef f acts is the spent fuel storage pool. The walls are 6'-

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I Report No. 9203-01 Revision 0 0" thick and are subsequently reinforced each way and each face.

These walls are subjected to hydrostatic pressure as well I

as thermal gradients. For hydrostatic pressures, bending moments at the corners result in tension on the outside face, while at mid width the bending moments result in compression on the outside face.

The thermal gradients tend to result in tension on the outside face.

Therefore, at the corners the thermal I

stresses would tend to reduce the bending stresses. At mid width the thermal stresses would tend to be additive.

However, thermal stresses are self relieving. Under I

ultimate loading, the stress in the reinforcing bars will be composed of the primary stress and a portion of the secondary stress. Excess secondary strain will result in very limited inclastic deformation.

Similarly, local hot spots due to pipe break, will potentially expand but be under restraint by adjacent I

cooler regions. This will result in the hot spot being in compression while the adjacent cooler concrete will be in tension. The stress relieving nature of thermal stresses will, therefore, inhibit any overstress. The limitation per ACI 349-76 for local short term temperature at the concrete surface is 650' F. There are known instances in which temperatures could reach this very high limit.

As stated by NRC: "For structures not subject to effects of pipe break accident, thermal stresses are unlikely to be significant.

THE DESIGN OF CONNECTICUT YANKEE MEETS THE UPDATED CRITERIA ITEM #11 ACI 349-76: 7.10.3 ACI 318-63: Section 805 Reinforcing Bar Splices in Reinforced Concrete Columns.

Structural elements affected:

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I Report No. 9203-01 Revision 0 Columns designed for stress reversals with stress in I

reinforcing bars at column face varying from f,

in compression to 1/2 f, or less in tension.

I The total tensile capacity then should be designed as twice the calculated tension. This situation can occur in moment resisting frames, subject to vibratory lateral loads such as earthquake. However, lateral resistance for the reinforced concrete structures is provided by reinforced concrete shear walls.

I Inasmuth as the stiffness of the walls is much greater than rny beam-column

frame, the columns cannot be subjer.ted to tensile stresses.

Therefore, this requirement would not be applicable.

THE DESIGN OF CO!1NECTICUT YANKEE MEETS THE UPDATED CRITERIA ITEM #12 ACI 349-76: Appendix B

. I ACI 318-63 No requirement Structural elements affected:

All steel embedments used to transmit loads from attachments into the reinforced concrete structure.

Reinforced concrete drawings were reviewed and anchor I

bolts, strap anchors, etc, were examined. The details of the anchors were observed to be in conformance with Figures B.1-1 and B.1-2, ACI 349-76. In all cases of anchor bolts and straps, positive anchorage was obtained by means of hooks, washers, or bends. A specific anchor bolt embedment subject to very high load was examined; namely, Control Building (DWG-16103-51031, 51032, FS 14A I

& 14B). It was found that the capacity of the embedment according to ACI 349-76 was much greater than the applied load. The conclusion is that the steel embedments would meet ACI 349-76, App. B.

The applied load vertical load was 1436 kips which compared with a capacity of 8686 kips, calculated in I

accordance with the 45* cone method of App. B, ACI 349-76.

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Report No. 9203-01 Revision 0 THE DESIGN OF CONNECTICUT YANKEE MEETS THE UPDATED CRITERIA.

ITEM #13 ACI 349-76: Appendix C ACI 318-64: No requirement Structural elements subjected to impulsive and impactive loads.

Structural elements affected:

I All structural elements whose f ailure under impulsive and impactive loads must be precluded.

The most severe effects are those resulting from tornado generated missiles.

Scoping calculations were based upon a total wind speed I

of 315 mph. This corresponds to that proposed by NRC, which was 2 5 5 + 6 0 = 315 mph, (Ref.2). This is based upon the expected occurrence-intensity relationship at a probability of occurrence less than 10-7 as indicated in Fig. 6 and Table 5 Enclosure 2, (Fig.4-1).

various pipe missiles and 1"

diameter rods of SRP I

Spectrum I missiles were evaluated. The wood plank and the utility pole were found to have little effect upon reinforced concrete structures. The automobile was not I

reviewed because it cannot effect the reinforced concrete control room. The automobile is in general not a problem of perforation, but rather one of plastic deformation. So I

if a wall is not capable of preventing spalling of

that, a

12" pipe missile it probably cannot resist the automobile missile.

I The PAB has in ei;fect two penthouses above El.

35'-6",

af ter the siding of the structural framing has been blown off. 10" walls are used around ducts.'It is estimated I

that spalling would occur with the larger pipe missiles.

On the other hand the walls surrounding the volume-control tank are very heavy; i.e., Three walls are 3'-1" and the fourth is 2'-6".

The roof slab is 2'-10".

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Report No. 9203-01 Revision 0 I

The reinforced concrete walls of the PAB vary from 12" to 2 '-0". Most of the 12" valls are protected by surrounding structures, in essence leaving only the 18" and 2'-0" valls exposed. These walls would be sufficiently thick I

and reinforced to withstand the pipe missiles, although some spalling may occur.

I The Control Room is more than 30 ft. above grade and is therefore unaffected by utility pole or automobile missile. The roof and the north and east walls would be insignificant 1y af fected by missile. While the potential I

for some scabbing exists for the south and west walls. These walls are actually interior walls which greatly reduces a perpendicular strike of a tornado missile used in full velocity.

The above is based on perpendicular strikes, it was found that even small departures from perfectly normal greatly reduces the missile effects.

According to the NRC staff evaluation, required wall and I

slab thicknesses for f ',=3 000 psi are 23" and 18" respectively, for tornado winds of 360 mph, (Ref.13).

This was based upon two missiles; namely 1" diameter I

steel rod at 317 fps and a utility polo and 211 fps, which is appropriate for OL applications which were not required to be protected against the full tornado missile I

spectrum during CP stage (Ref.13). Calculations and test data indicate that no scabbing will occur on 12" thick walls, with 1" rods at a striking velocity of 435 fps.

Similarly, the utility pole causes only cracks on a 12" wall at a velocity of 205 fps, (Ref.15).

Therefore, it can be concluded that all reinforced concrete structures are protected against the tornado missiles as required by USNRC (Ref.13).

THE DESIGN OF CONNECTICUT YANKEE MEETS THE UPDATED CRITERIA ASME III, Div.2 compared to ACI 318-63 I

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Report No. 9203-01 Revision 0 ITEM #14 Structural elements affected:

Containment and other elements transmitting in plane shear ASME III, Div.2 - CC-3421.5 ACI 318 No requirement I

A calculation was made using the seismic base shear of approximately 15,000 kips. The maximum imposed tangential shear was calculated to be about 145 psi, according to ASME III, Div.2 CC-3421.5. This approximate calculation I

is consistent with values presented in UFSAR, p. 3.7.16, (Ref.8).

The tangential shear carried by concrete, v,

equals I

about 145 psi while the applied tangential shear, v,,

equals about 100 psi. In addition, the liner alone is designed to resist tangential shear, (Ref.8).

The conclusion is that the design for tangential shear is compatible with ASME III, Div.2.

THE DESIGtJ OF CONNECTICUT YANKEE MEETS THE UPDATED CRITERIA I

ITEM #15 ASME III, Div.2, CC-3421.6 ACI 313-63, 1707 Peripheral Shear.

Regions subject to peripheral shear in the region of I

concentrated forces acting normal to the shell surface.

The basis for the equations of concrete capacity : v, - -

4 V'f'.. However, ASME III, Div.2 does derate the concrete I

capacity due to the presence of membrane tensile stresses.

I Calculations indicate that under seismic and dead loads the concrete shear capacity is very high; namely, 217 psi, which would be equivalent in both-codes.

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I Report No. 9203-01 Revision 0 However, when combined with accident pressure, very high I

membrane tensile stresses would result, such that no concrete capacity would be developed.

Therefore, in effect, there would be no concrete shear capacity. The original design would have recognized this and; I

therefore, reinforcing would have been designed to resist the full peripheral shcar.

I A review of the reinforced concrete drawings indicate that all openings are very heavily reinforced with walls 4'-6" thick with a 3/8" steel liner, anchored to the concrete wall with Nelson studs.

This was confirmed by a review of a large penetration in I

the containment wall as discussed previously.

is obvious that the reinforced walls have sufficient It capability to resist local peripheral shear.

THE DESIGN OF CONNECTICUT YANKEE MEETS THE UPDATED CRITERIA I

ITEM #16 ASME III, Div.2 CC-3421.7 ACI 318-63: No requirement Structural elements affected:

Regions subject to torsion.

The limitation on the concrete capacity to resist pure I

torsional stress is similar to peripheral shear; in that, it is dependent upon the tensile strength of concrete. Under I

seismic loading there is capacity in the concrete to resist torsional stresses.

However, under accident pressures, the membrane meridional and hoop stresses I

would diminish the capability of the concrete in resisting torsional shear stresses to the point that the provision in ASME III, Div.2 would not be applicable.

Therefore the designers would have to resist torsion without reliance upon the concrete regardless of which code were used. Again the reinforced concrete walls would be capable of resisting local torsional shear stresses.

This was confirmed by a review of a large penetration in I

the containment wall as discussed previously.

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Report No. 9203-01 Revision 0 THE DESIG11 OF CO!1NECTICUT YANKEE MEETS THE UPDATED CRITERIA ITEM #17 ASME III, Div.2 - CC-3440 (b), (c)

ACI 318-63: No requirement Limitations on short term thermal loading.

Structural elements affected:

All concrete elements which could possibly be exposed to short term high thermal loading.

The temperature limitations for general areas as well as local areas are 180C and 345C, respectively.

These I

temperatures are higher than that which could result from the design basis for the Connecticut Yankee Containment Structure: namely, 127C (260F).

THE DESIGN OF CONNECTICUT YANKEE MEETS THE UPDATED CRITERIA ITEM #18 ASME III, Div.2 - CC-3532.1.2 ACI 318-63 Development length in biaxial tension fields.

Structural elements affected:

I Where biaxial tension exists.

ASME III, Div.2 requirements are such that reinforcing shall be terminated in anchorage in hooks, mechanical I

splices, etc. Bar development lengths shall be increased 25%.

A review of the structural drawings indicate that

-I mechanical splicing, hooks were widely used. At the base of the cylindrical. wall, reinforcing bars are placed to resist discontinuity

moments, which are secondary I

moments, as well as vertical tenwile forces. These bars are cadweld spliced so as to be continuous.

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Report tio. 9203-01 Revision 0 I

Additional bars at openings, such as diagonal bars, are very long and would easily meet the requirements of ASME III, Div.2.

I The design would in all significant aspects meet the requirements of ASME III, Div.2.

I THE DESIGli OF COlitiECTICUT YANKEE MEETS THE UPDATED CRITERIA ITEM #19 ASME III, DIV.2 CC-3421.8 ACI 318-63: No requirement structural elements affected:

Brackets and Corbels A review of the reinforced concrete drawings indicates that no brackets and corbels covered by CC-3421.8 were employed in of the design of the containment.

THE DESIGN OF Coll!IECTICUT YANKEE MEETS THE UPDATED CRITERIA ITEM #20 ASME III, Div.2 CC-3600 to CC-3800 Structural elements affected:

I Liner and liner components.

Provisions for liner design were not available at the time of the construction of the Connecticut Yankee containment.

The provisions of ASME

III, Div.2 provide strain limitation rather than stress limitations. The strain limitations are very high, well above that which could be expected for the Connecticut Yankee containment liner.

Provisions for penetration assemblics in ASME III refer I

to code provisions of Div.1, which was based upon previous ASME Boiler & Pressure Vessel codes.

I A review of the liner drawings indicate that full i

penetration butt welds were used for the liner to penetration connections.

The codes used for design, welding, and inspection were I

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Report No. 9203-01 Revision 0 the then current ASME codes. These coda: became the basis of the liner portions of ASME III, Div.2.

Section Specifics CC-3121 General I

"The liner shall not be used as a strength element." The liner does not participate in resisting containment loads, with the possible exception of tangential seismic shear, which in reality would not carry significant membrano tension.

CC-3720 Liner The stresses in the containment liner during the accident internal pressure are about 10 to 27 ksi compression, Table 3.8.4, UFSAR. (Ref.8). This is well within the limitations of Table CC-3720-1, Liner Plate Allowables.

CC-3730 & 3810 Liner Anchors Nelson studs, 1/2" x 5-3/16" 0 17" o.c. This was very typical of liner anchorage.

CC-3740 Penetration Assemblies CB&I drawings were reviewed. In all cases reinforcing rings and shear plates were provided.

CC-3760 Fatigue No significant cyclic loads are expected.

CC-3840 Welded Construction 4

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All liner joints specified by CB&I were butt welds which would conform to ASME III, Div.2.

The NRR-NRC commissioned an independent review.

The resulting report was

" structural Review at the I

Connecticut Yankee Nuclear Generating Plant, Containment structure Under Combined Loads", (Ref.9). In Section 4.2, Liner-Plate System, it is stated that except for a

slight, 10%,

excess deformation of the Nelson stud I

anchors the liner system is well within the applicable code design limits of ASME II, Div.2.

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Report No. 9203-01 Revision 0 TiiE DESIGN OF CONNECTICUT YANKEE MEETS THE UPDATED I

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I I-Report flo. 9203-01 Revision 0 6.0 ColicLUSIori While there were additional loads and load combinations to be considered, it was found that due to the original criteria as well as subsequent analyses and strengthening, the structures possessed structural I

capability to be able to accommodate overall loads such as tornado offects and local effects such as accident pipe reactions.

The capability of-the plant to withstand local tornado missile effects and achin.ve safe shutdown is being addressed by using PRA techniques SEP Topic III-2 and III-4.A (Ref.11).

Similarly, with code changes, it is found that the new I

code requirements would have not applied or that the structure would have qualified for new code requirements.

I Therefore, based upon this review per SEP III-7.B when integrated with other interfacing SEP

topics, the capability of all Seismic Category I structures required by SEP III-7B (Ref.1) has been assessed to be capable of I

withstanding all design conditions stipulated by SEP III-7.B, TER-C5257-319.

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7.0 REFERENCES

I 1.

Design

Codes, Design

Criteria, and Loading Combinations, NRC SEP III-78, Franklin Research Center, TER-C5257-319, 8-20-82 2.

Seismic Reevaluation of Major Structures of the Connecticut Yankee Atomic Power Plant, URS/Blume, April 1983

3. NRC SEP Topic II-2A, Severe Weather Phenomena,12-8-80

4. NRC SEP Topic III-4A, Tornado Missiles S.

Tornado Probabilistic Risk Assessment of the I

Connecticut Yankee Atomic Power Station, Applied Research Associates, Dec. 1989

6. NRC Standard Review Plan, NUREG 800

7. Haddam Neck Plant, UFSAR I

8. Structural Review of the Connecticut Yankee Nuclear Generating Plant, Containment Structure Under Combined

Loads, C.Y. Liaw & N.C. Tsal, sponsored by NRR-NRC.

9. USNRC letter dated Oct. 21, 1992 from Mr. Alan Wang, USNRC to Mr. John F. Opoka, Northeast Utilities, SEP Topics III-2 and III-4.A, Wind and Tornado Loadings and Tcrnado Missiles

10. USNRC letter dated July 24, 1991 from Mr. Alan Wang, i

USNRC to Mr. Edward J. Mroczka SEP Topic III-6, Seismic Design Considerations.

11.

NUSCO letter dated July 11, 1991, from-Mr.

E.J.

I Mroczka to the USNRC, SEP Topics III-2 and III-4.~ A, Wind and Tornado Loadings / Tornado Missiles.

I

12. NUSCO letter dated Dec.24, 1991 from Mr. J.F. Opeka to the USNRC, Proposed Modifications to the Auxiliary-Feedwater System.

13.

USNRC letter dated August 2,

1982 from Mr.

D.M.

Crutchfield to Mr. W.G. Council, N.U., Tornado Missiles -

Haddam Neck.

14. USNRC letter dated September 2, 1982 from Mr.

D.M.

Crutchfield to Mr.

W.G.

Council, N.U.,

SEP III-2, Wind and Tornado Loadings, ifaddam Neck Plant.

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I 15.

Full-Scalo Tornado Missile Impact Toots, Sandia I

Laboratories, EPRI NP-440 July 1977, I

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I APPENDIX A LOAD COMBINATION CONTAINMENT STRUCTURE (7)

D + L + P, + P, + W

+ R.

I e

(14) D + L + T, + P, + R, + E '

PRIMARY AUXILIARY BUILDING CONCRETE (10) D+L+R + W o

(13) D + L + T, + P + R, + E ' + Y, + Y. + Ym STEEL (8)

D+L+R + W I

o t

(11) D + L + T + P, + R, + E ' + Y, + Y + Y 3

m CONTROL ROOM & SWITCHGEAR ROOM I

(10) D+L+W t

(13) D + L + T, + P, + E ' + Y, + Y3 + Y.

SERVICE WATER INTAKE CONCR M (10) D + L + R, + W t STEEL (8)

D+L+W t

DISCHARGE TUNNEL (10) D+L+W I

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I APPElfDiX B LOAD DEFINITIOllS D

Dead loads or their related internal moments and forces (such as permanent equipment loads).

E or E.

Loads generated by the operating basis earthquake.

E' or E,,

Loads generated by the safe shutdown earthquake.

F Loads resulting from the application of pre-stress.

Hydrostatic loads under operating conditions.

II, I

Hydrostatic loads generated under accident conditions, such as post-accident internal flooding. (F is sometimes t

used by others to designate post-LOCA internal flooding.)

I L

Live loads or their related internal moments and forces (such as movable equipment loads).

I P,

Pressure load generated by accident conditions (such as those generated by the postulated pipe break accident).

P, o r P, Loads resulting from pressure due to normal operating conditions.

R, or R, Pipe reactions under accident conditions-(such as those I

generated by thermal transients associated with an accident).

I R.

Pipe reactions during startup, normal operating, or shutdown conditions, based on the critical transient or steady-state condition.

T, Thermal loeis under accident conditions (such as those generated b; a postulated pipe break accident).

.E T

Thermal effects and-loads during

startup, normal o

R operating, or shutdown condition, based on the most critical taansient or steady-state condition.

T, All thermal loads which are generated by the discharge of safety relief valves..

W Loads generated by the design vind _ specified for the plant.

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W' or W, Loads generated by the design tornado specified for the plant. Tornado loads include loads due to tornado wind

pressure, tornado-created differential

pressure, and tornado generated missiles.

I Y,

Equivalent static load on the structure generated by the impingement of the fluid jet from the broken pipe during the design basis accident.

Y, Missile impact equivalent static load on the structure I

generated by or during the design basis accident, such as pipe whipping.

Y, Equivalent static load on the structure generated by the I

reaction on the broken pipe during the design basis accident.

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