Technical note Piping specific analysis of stresses due to thermal stratification

Within the framework of the ʹComponent Specific Analysis of Mechanical Behaviourʹ, the nuclear codes and standards, e.g. KTA Standard KTA 3201.2 on Components of the Reactor Coolant Pressure Boundary of Light Water Reactors (Design and Analysis) allow a simplified stress and fatigue analysis for piping by applying the stress index method. The equations supplementary to present K.TA Standard given in this context can be used for the consideration of the thermal loads arising from piston flow but not of those from thermal stratification. Thermal stratification occurs e.g. in the surge line of pressurised water reactors during start-up and shut-down processes. This phenomenon is explained and its effects are described. The equations supplementary to the present KLTA Standard are derived which enable the consideration of the load case ʹthermal stratificationʹ in the simplified stress and fatigue analysis. Their applicability is demonstrated by a numeric example. © 1999 Elsevier Science S.A. All rights reserved.