ML16256A174
| ML16256A174 | |
| Person / Time | |
|---|---|
| Site: | Waterford  |
| Issue date: | 08/25/2016 |
| From: | Entergy Operations |
| To: | Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML16256A115 | List:
|
| References | |
| W3F1-2016-0053 | |
| Download: ML16256A174 (7) | |
Text
WSES-FSAR-UNIT-33.3-1Revision 11 (05/01)3.3WIND AND TORNADO LOADINGSStructures, systems or components whose failure due to design wind loading could prevent safe shutdownof the reactor, or result in significant uncontrolled release of radioactivity from the unit, are protected from such failure by one of the following methods:a)the structure or component is designed to withstand design wind, orb)the system or components are housed within a structure which is designed to withstand thedesign wind.Structures, systems or components whose failure could prevent safe shutdown of the reactor, or result insignificant uncontrolled release of radioactivity from the unit, are protected from such failure due to design tornado wind loading or missiles by one of the following methods:a)the structure or component is designed to withstand tornado wind and/or tornado missile loads(refer to Subsection 3.5.1.4 for tornado missile criteria), or(DRN 00-1172)b)the system or components are housed within a structure and/or protected by a barrier which isdesigned to withstand the tornado wind and/or missile loads, orc)system or component failure is not credible because tornado induced failure modes areconsidered improbable as mentioned in section 3.5.1.4.1(DRN 00-1172)Table 3.2-1 lists all safety related structures, systems and components and the method of wind/tornadoprotection where applicable. The a or b designation in the table refers to item a or b above.3.3.1WIND LOADINGS 3.3.1.1Design Wind VelocityThe plant structures defined as seismic Category I structures are designed for a maximum wind of 200mph at 30 feet above plant grade.3.3.1.2Basis for Wind Velocity SelectionThe basis for the selection of the above wind velocity for design is presented in Section 2.3. The 100 yearrecurrence interval indicates a maximum wind velocity of approximately 100 mph. However, to assure the integrity of these structures under extreme wind conditions, a 200 mph wind is selected to providesufficient conservatism in design.3.3.1.3Determination of Applied ForcesThe wind loads which are applied to structures as static forces are derived from, the recommendations ofASCE paper No. 3269, "Wind Forces on StructuresThe dynamic wind pressure (q) in pounds per square foot is calculated from the wind speed using theformula:(1)q = 0.002558 V 2where V is the wind speed in miles per hour.
WSES-FSAR-UNIT-33.3-2Revision 11 (05/01)The local pressure at any point on the surface of a building is equal to:
P L = C peq(2)where C pe represents the local pressure coefficient which depends upon the geometricform of the building and the relative location of the point in question with respect to the direction of the wind. Values of C pe for several different shapes, of buildings are presented in ASCE Paper No. 3269 andASCE Paper No. 4933 (2). Values of C pe for the containment dome as shown in Figures 3.3-1 and 3.3-2are slightly simplified from those of Reference 2. The values of C pe are assumed constant across thewidth of the dome instead of using more than one value of C pe for each strip as suggested in the ASCE-paper.In general, C pe is positive for windward parts of buildings and negative for leeward parts of buildings.The values given in equation (2) represent the dynamic wind pressure on the surface of the building onlyin the case in which the building is airtight. If there are openings on the surface of a building, then aninternal pressure (P i) will be increased or decreased depending on whether the openings are mainly onthe windward or leeward surfaces as given in the following:
P i = C pi q(3)where C pi is the internal pressure coefficient. Detailed test values of C pi for certain buildings are listed inReference 1.In the design of walls and roofs, the pressure coefficient includes the summation of the external and theinternal pressures. Considering equation (2) and equation (3), the total dynamic pressure (P t): P t = P L + P iorP t = q(C pe + C pi)(4)The total directional wind pressure for the building, in the direction of the wind is given by:
P t= C D q(5)where C D.is the average drag or shape coefficient for the building and q is the dynamic wind pressure at the given height. C D includes the effects of positive pressure on the windward wall and negative pressureon the leeward wall.
C D and the pressure distribution around the cylindrical Reactor Building are determined by usingReferences 1 and 2.Table 3.3-1 and Figures 3.3-1 and 3.3-3 list the applied force magnitude gust factor used, and pressuredistribution calculated for each plant safety related structure.
WSES-FSAR-UNIT-33.3-3Revision 11 (05/01)3.3.2TORNADO3.3.2.1Applicable Design ParametersParameters applicable to the design basis tornado for seismic Category I structure design are inaccordance with the following criteria:a)external wind forces resulting from a tornado funnel with a horizontal rotation velocity of 300 mphand a horizontal translational velocity of 60 mph. The tornado rotational (tangential) velocity and translational velocity are summed algebraically, and applied on the entire building structure,b)a decrease in atmospheric pressure of three psi at a rate of one psi/sec,(DRN 00-1172)c)the effect on (a) and (b) are considered to act simultaneously, and/or in accordance with StandardReview Plan Section 3.3.2(DRN 00-1172)d)the external tornado generated missiles considered, as described in Subsection 3.5.1.4.e)Category I structures are designed without venting (eg. blow-out panels) provisions.
In the design of steel structures, an increase in code allowable stresses was permitted for tornadic loadingin combination with other loadings. Stresses less than or equal to 90 percent of yield for flexure and less than or equal to 58 percent of yield for shear were allowed.The design basis tornado for Waterford 3 is based upon the tornado wind and pressure characteristicsconsidered appropriate by the nuclear industry and the AEC at the time the plant was designed prior to the issuance of Regulatory Guide 1.76 in April 1974. Both the total wind speed and the maximum negative pressure are the same for the Waterford design basis tornado as those specified in Regulatory Guide 1.76. In addition, the effect of 2 psi/sec pressure drop as specified in Regulatory Guide 1.76 has been evaluated. The natural period of the structure systems is 0.02 to 0.30 sec. Utilizing the method to determine the maximum dynamic load factor, (DLF) maximum of one-degree elastic systems, undamped and subjected to constant force with finite rise time as given in "Introduction to Structural Dynamics" by John M. Briggs, (DLF) maximum is determined to be approximately equal to 1.00 and 1.02 for the pressure drop rate of 1 and 2 psi/sec respectively. The increase of two percent in (DLF) maximum is acceptable within the conservatism used in calculating the equivalent static pressure loads. Therefore, the design of the seismic Category I structure meets the intent of Regulatory Guide 1.76.3.3.2.2Determination of Forces on StructuresTornado wind speed is converted into equivalent dynamic pressure loadings and the computations forwind pressure, their distribution on surface area of buildings, shape factors and drag coefficients are based on the procedures outlined in ASCE Paper No. 3269. Because of the unique characteristics WSES-FSAR-UNIT-33.3-4Revision 13 (04/04) of tornados, gust factor and velocity variation with height are not considered. With respect to the pressure distribution around the Reactor Building, wind force data reported in ASCE Papers 3269 and 4933 are used
in the design.The effect of (a), (b), and (c) given in Subsection 3.3.2.1 are considered.The dynamic pressure corresponding to the 360 (i.e., 300 mph + 60 mph) mph wind velocity calculated in the standard form is:
q = 0.002558 V 2 q = 0.002558 (360) 2 = 332 psfFor large structures or parts of structures whose horizontal dimensions perpendicular to the wind force are comparable to the radius of the tornado vortex at which the maximum tangential wind speed occurs, a more
realistic, average tornado wind speed of 300 mph can be used in equation(1) to calculate the dynamic wind pressure for the structure as a whole (1) . Local dynamic wind pressure is still based on 360 mph for equations (2), (3), and (4).(DRN 00-1172, R11)The pressure differential (p) noted in Subsection 3.3.2.1 (b) is considered in calculating tornado pressure loading for closed buildings. The maximum pressure drop of three psi occurs at the center of the vortex and diminishes with distance from the vortex center. Theoretically, this pressure drop ranged from 1.5 psi at the
point of max imum tornado tangential wind speed to three psi at the center of the tornado where the tangential speed is zero. However, the plant design conservatively used the maximum pressure drop of three psi throughout for structural analysis. For these buildings, the local pressure loading, equation (2), is
combined with the pressure differential (p) to give:P = qC + p(6)
P = qC pe +0.5 p (for Special Doors and Maintenance Hatch Shield Door Only and RAB Roof Hatch HC-31 Covers)The total directional wind pressure on the entire building in the direction of the maximum wind speed will remain the same as given by equation (5). The equivalent static pressure loading for the various structures are given on Table 3.3-2 and Figures 3.3-2 and 3.3-4.(DRN 00-1172, R11)(DRN00-1032, R11-A)
The total structural response due to the design basis tornado is determined by combining the static analysis results that account for the tornado pressure loading as given by equation (6) and the equivalent static loads as obtained from the missile impactive analysis discussed in Subsection 3.5-3.(DRN00-1032, R11-A) 3.3.2.3 Effect of Failure of Structures or Components not Designed for Tornado Loads(DRN00-1032, R11-A;02-86, R11-A; 03-1823, R13)
Non-seismic structures such as the Intake superstructure framing, Intake structure crane, and Turbine Building (but not the Turbine Gantry crane) have been designed for tornadic wind on the exposed steel surfaces, but have not been designed to resist tornado generated m issiles.The failure of any structural member or component in either of these non-seismic structures, that would be caused by being hit by a tornado generated missile, would be local in nature causing no damage to seismic Category I structures or
components and would not prevent the safe shutdown of the reactor or result in uncontrolled release of radioactivity to the environment.(DRN00-1032, R11-A;02-86, R11-A; 03-1823, R13)
WSES-FSAR-UNIT-3 3.3-5 Revision 11-A (02/02)(DRN 00-1032; 02-86)(DRN 00-1032; 02-86)
The Turbine Building has been evaluated for tornado loadings to the following extent:(DRN 00-1172)a)Siding in Place - The building is designed to resist a wind load of 200 mph (assume pressure drop to be zero).(DRN 00-1172)b)Siding Failure - Siding fails for winds above 200 mph. The siding is designed to fail but remain balanced and restrained by the central portion of the panel against the girts. The exposed steel framing is designed to withstand a tornado load of 360 mph.c)Tornado-born missiles are not considered in the design.
SECTION 3.3:
REFERENCES(1)ASCE 3269, "Wind Forces on Structures," American Society of Civil Engineers, Transactions,Vol 126, Part II, 1961(2)"Wind Loads on Dome-Cylinder and Dome-Cone Shapes, "F J Maher, Journal of the StructuralDivision, ASCE Vol 92, No. S T 5 Proc Paper 4933, October 1966 WSES-FSAR-UNIT-3TABLE 3.3-1WIND SPEEDS AND RESULTING STATIC PRESSURE LOADINGSWind SpeedPressure ExternalStructure (mph) CoefficientPressure (psf)Reactor BuildingRefer to Figures 3.3-1 and 3.3-3Reactor Auxiliary200 0.9 (1) 92Building -0.5 (2) 0.7 (3) 0.8 (4) -82Fuel Handling200 0.9 (1) 92Building -0.5 (2) 0.7 (3) 0.8 (4) -82(1) Windward(2) Leeward'-' indicates suction
(3) Roof(4) Sidewalls WSES-FSAR-UNIT-3TABLE 3.3-2TORNADO WIND SPEEDS ANDRESULTING STATIC PRESSURE LOADINGS External TornadoExternalExternalLoading WithWind SpeedPressureLoading PressureStructure (mph) Coefficient (psf) Diff (psf) Reactor BuildingRefer to Figures 3.3-2 and 3.3-4Reactor Auxiliary360 0.9 299 (1) -133Building -0.5-166 (2) -598 -0.5-166 (3) -598 -0.8-266 (4) -698Fuel Handling360 0.9 299 (1) -133Building -0.5-166 (2) -598 -0.5-166 (3) -598
-0.8-266 (4) -698 suction indicates'-'Sidewalls (4)Roof (3)Leeward (2) Windward)1 (