ML20134E158

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Containment Integrity at Surry Nuclear Power Station
ML20134E158
Person / Time
Site: Surry, 05000000
Issue date: 02/28/1984
From: Pananos W, Reeves C
STONE & WEBSTER ENGINEERING CORP.
To:
Shared Package
ML20134E148 List:
References
FOIA-85-457, RTR-NUREG-1150-2-V2-B.26, RTR-NUREG-1150-2-V2-C.8.04 NUDOCS 8508200048
Download: ML20134E158 (7)
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CONTAINMENT INTEGRITY AT SURRY NUCI. EAR POWER STATION By W. J. Pananos and C. F. Reeves Stone & Webster Engineering Corporation Boston, Massachusetts February 1984

SUMMARY

AND CONCLUSIONS This paper summa rizes results of a study by Stone & Webster Engineering Corporation (SWEC) of the structural capacity of the Surry Nuclear Power Station reactor containment building. In this study an analysis was conducted to determine the minimum pressure required to produce yielding

  • stresses in all load resisting elements, the location in the pressure boundary where' such yielding would first occur, and the effects of changes in liner temperature on the response of the containment to pressurization.

This paper discusses the design bases, details of construction, inherent conservatisms of the containment, and the Structural Acceptance Test. It describes the SWEC analysis; presents an abridgment of the results; and makes certain observations based on those results. The paper shows that Nuclear Regulatcry Commission design criteria and standard design practice co.ubine to guarantee a mininium yield capacity for a large dry pressurized water reactor concrete containment of at least twice the design pressure loading. Containment response at penetrations and at the junction of the wall and the foundation mat are also described. The study led to the followirg conclusions:

The minimum theoretical yield capacit/ of the Surry containment is  ;

119 psig. The design pressure is 45 psig. First tensile yielding  !

of the reinforcement and liner would occur in the hoop direction {

in free membrane zones of the wall at locations away from struc-tural discontinuities.

The inside hoop reinforcing bars would be the first structural elements to yield provided there is no significant temperature differential through the concrete wall. The liner would be the last element to yield.

svous a weserva

  • Liner temperature changes affect strains in the liner and rein-forcement, radial displacement of the pressure boundary, and widths of cracks in the concrete. Temperature change also affects the pressure at which the reinforcement would begin to yield, b
  • Liner temperature changes do not affect the full yield capacity of the wall over the range of temperatures considered.

~

I

  • Cracks would not form in the liner under loss of coolant accident I (LOCA) conditions because the liner would be in a state of biaxial compression.
  • The liner is not likely to crack at full yield capacity because the liner material is very ~ ductile and the most severe liner strains, which occur at pen,etrations, are only slightly greater than the yield strain.

DESCRIPTION OF SURRY CONTAINMENT The containment analyzed is a right cylinder with a hemispherical dome. The cylinder is outfitted with an equipment hatch, a personnel hatch, and numerous penetrations for piping, electrical conduits, and instrumentation leads. The cylinder has an inside diameter of 126.0 ft and a wall thickness of 4.5 ft; the dome is 2.5 ft thick. A 10 ft thick foundation mat supports the structure. Concrete design is based on a minimum compressive strength of 3.0 ksi.

The concrete in the cylinder and dome is reinforced with continuous 2.25 in.

diameter (No.18S) steel reinforcing bars arrayed in the meridional and hoop '

  • directions. Supplemental reinforcing steel was installed around all penetrations to account for stress concentrations. Heavy reinforcement was provided at the junction of the cylinder wall and the foundation mat to control flexure and shear at this discontinuity. The cylinder also contains tangential / diagonal reinforcement designed to resist earthquake forces. The foundation mat is reinforced with 2.25 in. diameter reinforcing steel in radial and circumferential arrays at the top and in a rectilinear pattern at the bottom. Reinforcement is ASTM A408 Grade 50 with a minimum yield-strength of 50 kei. Reinforcing steel was proportiened using the ultimate strength design (USD) method with combinations of various factored loads.

These loads include the pressure (45.0 psig) and temperature (280'F) effects caused by a postulated LOCA, earthquake force, internal and external missiles, tornado wind, pipe rupture forces, and working loads. The largest ,

single demand for strength in the pressure boundary. comes from application of the LOCA pressure, which was factored by 1.5.

The containment is fully lined throughout with 0.375 in. thick steel plate in the cylinder, 0.5 in. plate in the dome, and 0.25 in. plate covering the foundation mat. All liner welds are leaktight and shrouJed with steel test channels. Liner steel is ASTM 516 Grade 60 with a minimum yield strength of 32 ksi.

It was a licensing requirement that no credit be allowed for the load carrying capacity of the liner. It also was a requirement that the capacity of cracked concrete to resist earthquake forces be ignored, so the 2

STONE & WESSTER

tangential / diagonal reinforcing steel had to be designed to withstand all of the earthquake shear force.

Note that only specified minimum yield strengths were used in the Surry design and in this study. However, actual yield strengths of reinforcing and liner steels are typically 10 percent higher than their minimum speci-fled strengths.

i Production concrete strengths are typically 20 to 30 {

percent higher than specified design strengths.  !

In addition to the above conservatisms in uthe design basis, construction 1 efficiency in placing reinforcement at the top of the foundation mat and around penetrations dictated spacing of the bars that resulted in approxi-mately 10 percent excess reinforcement. The safety provisions of the USD method specify that strengths must he computed using ma te rial capacity reductio'n factors, which provide another conservatism.

All of these conservatisms contribute to the overall strength of the con-ta irunent. As material strengths greater than the specified minimum were not included in the SWEC analysis, the results of that analysis are conservative.

ANALYSIS AND RESULTS The SWEC analysis established shell behavior in the hoop and meridional directions in terms of liner and reinforcement stresses and strains, under various combinations of incremental pressures (P) and changes in liner temperature (AT), between P = 45 psig and 100*F AT, and P = 120 psig and 325'F AT. The analysis is based on the between the liner and the reinforced concrete. assumption of full compatibility Calculations were terminated -

at the strain.

latter point, with the reinforcement at approximately two times yield Radial displacement of the cylinder wall under this condition would be approximately 2.5 in. The SWEC analysis did not examine the behavior of the containment at the ultimate (tensile) capacity of the reinforcement because the containment would have to expand several feet before ultimate stress and strain could be reached.

The method used to perform this analysis also was used to calculate strains and deflections under structural acceptance test conditions -- 52 psig and AT = 0'F. Analytical results were approximately 15 percent greater than i

observed values of liner strain and radial deflection. It is believed that '

the difference forcing between is the duecracks.

to the stiffness of the concrete blocks on the rein-Extrapolation of test results and further analysis indicate that observed and calculated v,alues would be approximately the same at pressures above 65 psig. i i

Table 1 presents an abridgment of the stress and strain analysis results fer the cylinder wall reinforcement and liner in the hoop direction in the free membrane zone, 65 ft above the foundation mat. Table 2 presents a similar abridgment for the meridional direction at the same location. Review of Tables 1 and 2 leads to the following observations:

( For any given AT, the reinforcement and the liner will yield at a lower pressure in the hoop direction than in the meridional direction.  ;

)

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STONE & WESSTER g

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  • The liner can yield in compression in either the hoop or meridional direction because of the ef feet of temperature change.
  • For AT = 200*F, a change which could be associated with a LOCA, g the liner remains in compression in the hoop direction until pressure reaches approximately 78 psig. The liner is the last load carrying element to reach tensile yielding strain, which occurs at 119 psig.
  • Changes in liner temperature affect the strains in the liner and reinforcement, and the pressure at which the reinforcement begins to yield.
  • Changes in liner temperature do not affect the full yield capacity of the containment.

An approximate but conservative analysis was made to evaluate stress and strain in the 1.0 in. thick liner plate and welds that secure the 8 in, dia-meter schedule 40 electrical penetrations. The analysis considered pres-sures from 100 to 120 psig and temperature changes from 100 to 325'F AT. It was determined that, as an upper bound, liner strains will not exceed three times general liner yielding strains. Therefore, the pressure boun,dary will remain intact at the penetrations over the range of pressures and tempera-tures changes considered in this analysis.

The thick, reinforced concrete (boss) around the equipment hatch was not included in this analysis. liowever, the boss is a very rigid inclusion in the membrane field of the containment wall. Because it is much stiffer than the membrane, cracks in the concrete in the hatch should be narrower than -

those in the free field.

Bounding calculations show that the connection between the wall and founda-tion mat is capable of withstanding 120 psig. The formation of a plastic hinge at this location, at a pressure which is well below tne yield capacity of the containment, would prevent development of a shear force sufficient to cause the radial shear reinforcement to yield. Therefore, it is reasonable to presume that a gross shear slip would not occur and that the integrity of j

the liner would be maintained. l 1

Liner strains measured during the structural acceptance test were very uniform except at penetrations. This indicates . that the bond between the liner and the concrete was broken as the structure was strained during pressurization. ,-

Concrete cracks which formed during the structural acceptance test, having esse.itially closed after depressurization, will cpen during any subsequent pressurization. Typical vertical cracks in the cylinder wall are spaced at approximately 2 ft. At test pressure, 52 psig, these cracks were observed to open to approximately 0.01 in.

i l 4 Stopes & Wassrsse I

TABLE 1 CONTAINMENT MEMBRANE BEHAVIOR IN THE HOOP DIRECTION AT

  • VARIOUS PRESSURES AND LINER TEMPERATURE CHANGES
  • Strain (cIH)** and Stress (6LH)***

Pressure AT < AT AT (psia) 150*F 200*F 325*F O O

  • IN LH "IH LH *IH LH 45 8.20 x 104 -5.1 - 8.86 x 104 -12.8 0.00105 -32.0 50 8.89 x 10~4 -3.1 9.55 x 10~4 -10.8 0.00112 -30.1 60 0.00103 1.0 0.00109 -6.8 0.00126 -26.1 70 0.00117 5.0 0.00123 -2.70 0.00140 -22.1 80 0.00130 9.1 0.00137 1.3 0.00154 -18.0 90 0.00144 13.1 0.00151 5.4 0.00167 -14.0 95 0.00151 15.1 0.00158 7.4 0.00175 -11.7 100 0.00158 16.7 0.00165 8.6 0.00195 -6.0 .

105 0.00165 18.6 0.00172 10.4 0.00229 4.1 110 0.00172 20.1 0.00181 14.7 0.00264 14.2 114 0.00180 23.4 0.00208 22.2 0.00291 22.2 118 0.00203 30.3 0.00236 30.3 0.00319 30.3 119 0.00210 32.0 0.00243 32.0 0.00326 32.0 Radial Deflection at Liner Yield (in.)

AT AT AT 150*F 200*F 325'F 1.59 1.84 2.46 NOTES:

  • Assumes E = 29 xs lo psi and a = 6.67 x 10 s (in./in.)/*F. Neither E or a were adjusted for temperature change.

! **cIH = hoop strain inside hoop reinforcing bars (in./in.)

l

      • 6LH = hoop stress, liner (kips /in.2) l l 1 of I stoms a wamenn

l TABLE 2 CONTAINMENT MEMBRANE BEHAVIOR IN THE MERIDIONAL DIRECTION AT VARIOUS PRESSURES

, AND LINER TEMPERATURE CHANGES

  • Strain (c)** and Stress (6g)***

Pressure AT AT AT (psia) 150*F 200*F 325'F c 6g e og c 6g 45 6.02 x 10~4 -11.6 7.01 x 10~4 -18.4 8.99 x 10~4 -32.0 50 6.52 x 10~4 -10.1 7.51 x 10~4 -16.9

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9.70 x 10 4 -32.0

~

60 7.52 x 10 4 -7.2 8.51 x 10~4 -14.0 0.00110 -31.0

~

70 8.51 x 10 4 -4.3 9.50 x 10~4 -11.1 0.00120 -28.1 80 9.51 x 10"* -1.4 0.00105 -8.2 0.00130 -25.2 90 0.00105 1.4 0.00115 -5.3 0.00140 -22.3 95 0.00110 2.9 0.00120 -3.9 0.00145 -20.8 100 0.00115 4.3 0.00125 *

-2.4 0.00150 -19.4 105 0.00120 5.8 0.00130 1.0 0.00155 -17.9 110 0.00125 7.2 0.00135 0.5 0.00160 -16.5 114 0.00129 8.4 0.00139 1.6 0.00164 -15.3 118 0.00133 9.6 0.00143 2.8 '

0.00168 -14.1 119 0.00134 9.8 0.00144 3.1 0.00169 -13.9 i

NOTES:

  • Assuanes E = 29 x 10s psi and a = 6.67 x 10~8 (in./in.)/*F. Neither E or a were adjusted for tersperature change.
    • c = Meridional strain on all components (in./in.).
      • 6g = Meridional stress, liner (kips /in.2) 1 of 1 STONE & WESSTER

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