ETD

Archivio digitale delle tesi discusse presso l'Università di Pisa

Tesi etd-11072013-050254


Tipo di tesi
Tesi di laurea specialistica
Autore
GIANFELICI, SIMONE
URN
etd-11072013-050254
Titolo
SIMMER Code Improvements and Applications in Safety Analysis of MYRRHA Reactor
Dipartimento
INGEGNERIA CIVILE E INDUSTRIALE
Corso di studi
INGEGNERIA NUCLEARE E DELLA SICUREZZA INDUSTRIALE
Relatori
relatore Prof. Ambrosini, Walter
relatore Dott. Forgione, Nicola
Parole chiave
  • SIMMER
  • MYRRHA
Data inizio appello
25/11/2013
Consultabilità
Completa
Riassunto
As a part of collaboration between the Dipartimento di Ingegneria Civile ed Industriale (DICI) of the University of Pisa and the Institut für Kern- und Energietechnik (IKET) of the Karlsruher Institut für Technologie, a FORTRAN program, for the restarting of calculations for SIMMER III code was developed. The “SIMMER-to-SIMMER coupling program” gives great flexibility in comparison with the default RESTART capability of the code and allows modifying any option in the input file.
The first part of this thesis work describes the SIMMER-III code and the ADS reactors, in particular the MYRRHA-FASTEF reactor.
In the fourth chapter a description of the coupling program and the 2D domain adopted in the description of the MYRRHA reactor is presented. The results of a 500 s steady-state calculation are compared with those of a standard RESTART and of a restart carried out with the coupling program, both from 200 s of simulation. For both restarts, pressure and velocities are in good agreement with the steady-state analysis, while the temperatures show small differences during the two transients.
The coupling program was used to start transients of fuel release, equivalent to the mass of fuel present in a single pin, in natural and forced circulation. The results are then compared to those already obtained by DICI, started with velocity and temperature fields chosen by the user and with radius of fuel particles equal to 1 mm. Due to the different velocity and temperature fields at the beginning of the transients, a higher amount of fuel particles was calculated in proximity of the baffle in forced circulation conditions. Furthermore, for natural circulation calculations, the fuel particles released tend to concentrate more in proximity of the free level of the hot pool. According to the results of the SEARCH meetings, the radius was then set to 75 micrometers and a comparison with the previous simulation is reported. The smaller fuel particles tend to float and accumulate more, in particular in the regions where the coolant has low velocities.
Finally, to check the coherence of the geometry approximations of the 2D mesh, the results of the last analysis are compared with those of the analyses of fuel pin release performed with the 3D model of MYRRHA developed by DICI and ENEA. Differently from the 2D one, the 3D domain shows high concentration of fuel particles between the diaphragm and the vessel, and a lower amount in the pumps and the cold pool A certain amount of fuel near the baffle is anyhow predicted.
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