NUCLEAR REACTORS

Author: LLOPIS ALVAREZ JOSE CARLOS.
Year: 2006.
University: POLITÉCNICA DE CATALUÑA [www.upc.edu].
Place of defense: AULA C-3 PAVELLÓ C.ETSEIB.
Place of preparation: ETSEIB, Edifici H PLANTA 11 SD.

Summary: This Doctoral Thesis presents the incorporation of realistic models of control systems, protections, permissive circuits, automatic signals and manual actions in a thermalhydraulic model based in RELAP. In order to develop this models has been used the internal components of RELAP, this is a new practice in the ambit of use thermalhydraulic codes best estimate. The thesis also supposes the imbricación of two initiatives that arose after the accident. Te Thesis also supposes the imbrications of two ways that they were impelled after the accident of Three Miles Island, unit 2: the development of Emergency Procedures Operation and the impulse of the codes best estimate. Is possible to use realistic models for the verification of these procedures. A methodology of work has been established, in the first place in standardizing the models of control components that assures a behaviour near the reality makes sure and in addition reduces the user effect. The control models of the NPP Vandellòs II and Ascó I & II have been developed from de design logic planes and a functional verification of such has been made. For the model of the NPP Ascó I & II the extension of the validation has been two transitory and for the NPP Vandellòs II has been five transitory. It is exposed how with these models design improvements can be proposed, fundamentally of control, and other applications in areas of formation and operation and its use for validation of simulators of training of operators, preparation of emergency manoeuvres and verification of design criteria. The examples of design improvement that appear they have its origin in the analysis of transitory with undesired reactor trips or some variable of plant approaches the trip set point. With the reduction of the probability of reactor trip an improvement in the availability of the plants can be obtained and also to contribute to the security. Also one is the process of confluence of the models the NPP Vandellòs II and Ascí I & II has been made and that has supposed an improvement of the existing ones previously. The obtained models have demonstrated to be useful to allow to propose new applications in the scope of engineering: to support modifications of design and to provide a support to formation and operation that allow to improve it availability and the security of the plants. In the thesis the following ones are like example: ⢠Proposal of improvement of design to avoid the turbine and reactor trip in a transitory of load of loss in the NPP Ascó by the protection of overtemperature. ⢠Proposal of improvement of design to avoid the turbine and reactor trip in a transitory of shutdown of a main water turbopump of main water system in the NPP Ascó. ⢠Proposal of improvement of design for a greater stability in the control of level of the pressurizer in the NPP Ascó I & II. ⢠Proposal of improvement of design to avoid the turbine and reactor by high level in a steam generator in a transitory of turbine trip below P-8 for the NPP Vandellós II. ⢠Proposal of optimization of the program of level of the pressurizer for the NPP Vandellòs II ⢠Proposal of improvement of procedure of operation to low loads for the NPP Vandellòs II For that reason, with the obtained models, modifications of design can be proposed new applications in the scope of engineering and be supported that allow to improve the availability and the security of the plants as well as in other areas like formation and support to operation. The possible applications of a best estimate model of a NPP in the engineering areas and formation constitute an additional tool that can contribute to: ⢠To avoid undesired reactor and turbine trips ⢠To improve operation procedures ⢠To contribute to the formation ⢠To contribute to verify and to improve the training simulators

Author: AREVALO MORA CRISTINA M..
Year: 2006.
University: POLITÉCNICA DE MADRID [www.upm.es].
Place of defense: E.T.S. ING. INDUSTRIALES.
Place of preparation: E.T.S. ING. INDUSTRIALES.

Summary: The dafio radiation in compact hexagonal metals (hcp) is very different from the damage centered metals in the body (bcc) or focused on the faces (fcc). The pilot study of the cluster of defects in these metals is dominated by the consideration of the geometry of its network and the ratio between its two network parameters (c / a). Because of this anisotropy crystallographic. It is expected diffusion anisótropa from defects in the crystal (jump distance and frequency of defects jump depend on the direction in which it occurs). The main aim of this thesis has been the creation of a new and original model for the understanding of the microscopic evolution (diffusion of defects) hexagonal metal compact, specifically a-Zirconio, using the technique of simulation Monte CarIo (MC) Cinético , which allows us to understand the evolution of the accumulation of dafio for times of the order of hours. Specifically it has been used as a base code BIGMAC developed by Lawrence Livermore National Laboratory (LLNL) has been modified over this thesis. In order to understand the behavior and stability of the different types of defects and agglomerates defects has studied the evolution of the various types of waterfalls in time (aging cascade displacement) getting defects fleeing as recombination a fraction of those in the cascade, and thus the number and type of defects that interaccionarían with microstructure. In order to understand the dafio by neutron irradiation on the material, has been the target of the thesis study the evolution of the microstructure under the conditions of a fission reactor current. It has introduced several changes to the physical mechanisms incorporated in the code, creating a new code of MF considering the hexagonal network. He has also been a goal of this thesis a study of the damage by electron irradiation in Zirconio to compare with experimental results and results obtained using a different technique simulation (Technical Field medium). The idea of introducing a field of tension in the system is very important level study of irradiated materials and can have multiple applications if this option is included in a code of kinetic MC. On the one hand, the macroscopic level, the structural materials of nuclear reactors are subject to external tensions on the other hand, dislocations and precipitation occurring in the material due to dafio radiation have a field of tension around them capable of attract or repel bugs. This modification of the code has been done in this thesis.