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This document is aimed at comparing the fatigue analysis methods based on the RCC-M code and on the harmonized standard EN 13445-3 with a view to quantifying the associated deviations and uncertainties, at each step of the calculation, by taking into account every aspect of each code such as calculation thickness of the FE model, physical properties, combination method and fatigue curve. This comparison study consists in analyzing the 4 Test Cases (TC) described below: • TC1: Study of the cylindrical-edge transition cone with its upper shell/shell type full-penetration butt weld. • TC2: Study of the feedwater nozzle (FWN) with its full-penetration weld on the nozzle support ring. • TC3: Study of the misalignment effect of neutral axes at shell/shell type full-penetration butt weld level. • TC4: Study of the out-of-roundness effect at shell/shell type full-penetration butt weld level. The welds considered in this study are full-penetration butt welds whose RCC-M quality is Level 1, whose welding procedure has been qualified, which are dressed, made flush with base metal by grinding and which have been fully (100%) inspected by NDE.

Confronted with the problem of how to conduct a complete fatigue analysis of the Tube Plate (TP) of Tubular and Shell Heat Exchangers and particularly of the Steam Generators equipping nuclear power plants of the Pressurized Water Reactor type (PWR), analysts have developed a method to analyse stress in perforated flat and thick Tube Plates with square penetration (crate) patterns, and in particular to analyse several specific zones such as the Interface Zones and various Effects, such as the Secondary (or Shell) Thermal Gradient Effect (STG Effect), the Thermal Gradient in the No-Tube Lane Effect (TGL Effect) and their interactions. The benefit of the approach is that it enables to analyze mechanical and thermal stress calculated using a full 3D Finite Element model incorporating an equivalent solid and the different Interface Zones, and allowing simulating the specific Thermo-Mechanical Effects. The Interface Zones (IZs) are those between the perforated and non-perforated area, the STG Effect is due to the strong gradient near the Secondary (or Shell) Side surface, the TGL Effect is produced by a temperature gradient across the No-Tube Lane. The method used for the fatigue analysis is based on a “Partitioning Stress Method” by means of which the stress induced by the various load types — mechanical loads, global thermal loads, local thermal effects (STG and TGL Effects), and local geometrical effects (IZs) — are first treated separately and then recombined with their appropriate Stress Multiplier Functions.