which generate together 2000 MW. Angra 3, the third plant of the nuclear station, is under construction and will supply 1405 MW to the electrical grid. The nuclear fuel assemblies, after a work cycle, are removed from the reactor and stored in the respective storage pool. Each one of the NPPs is provided with a spent fuel pool, which has a limited storage capacity, and do not suffice for the whole lifetime of the plants. Thus, a complementary storage facility must be provided for the nuclear station for the NPPs to keep operation. Facilities for storage of spent fuel assemblies (SFAs) which are not "attached" to the reactor building are referred to as "away from reactor" storage facilities. There are two main types of SFA storage in away from reactor facilities: dry storage and wet storage. In both cases, the installation must be provided with a solution to the remove residual heat generated by the spent fuel.Eletronuclear, the company responsible for construction and operation of NPPs in Brazil, has designed a wet SFA storage facility to fulfill the demand for space. According to the design, this storage facility would be provided with a fully passive cooling system for removal of the residual heat. Worldwide, there is only one installation with a similar solution, which is operating in Gösgen, Switzerland. This decision follows the global trend to increase participation of passive systems in nuclear installations, especially after the events of March 11, 2011, in Fukushima. In that occasion three of the six units of Fukushima Daiichi nuclear station suffered a core meltdown caused by a lossof-coolant accident. The unavailability of external energy supply and emergency diesel generators was the cause for the loss of cooling capacity.Passive cooling systems (PCSs) are engineering solutions to perform the function of heat transfer using the temperature difference between hot and cold sources to generate the driving force for the flow. Their advantages

The penetrations in the early Pressurized Water Reactors Vessels are characterized by Alloy 600 tubes, welded by Alloy 182/82. The Alloy 600 tubes have been shown to be susceptible to PWSCC (Primary Water Stress Corrosion Cracking) which may lead to crack forming. The cracking mechanism is driven mainly by the welding residual stress and, in a second place, by the operational stress in the weld region. It is therefore of big interest to quantify the weld residual stress field correctly. In this paper the weld residual stress field is calculated by finite elements, using a common approach well known in nuclear domain. It includes a transient thermal analysis simulating the heating during the multipass welding, followed by a transient thermo-mechanical analysis for the determination of the stresses involved with it. The welding consists of a sequence of weld beads, each of which is deposited in its entirety, at once, instead of gradually. Central as well as eccentric sidehill nozzles on the vessel head are analyzed in the paper. For the former a 2-dimensional axisymmetrical finite element model is used, whereas for the latter a 3-dimensional model is set up. Different positions on the vessel head are compared and the influence of the sidehill effect is illustrated. In the framework of a common project for Angra 1, Tractebel Engineering (Belgium) and Eletronuclear (Nuclear Utility, Brazil) had the opportunity to compare their analysis method, which they applied to the Belgian and the Brazilian nuclear reactors, respectively. The global approach in both cases is very similar but is applied to different configurations, specific for each NPP. In the article the results of both cases are compared.