ETD

Archivio digitale delle tesi discusse presso l'Università di Pisa

Tesi etd-09172014-141743


Tipo di tesi
Tesi di laurea magistrale
Autore
SCALETTI, LUCA
URN
etd-09172014-141743
Titolo
Thermal hydraulic investigation of a prototype double wall bayonet tube heat exchanger installed in CIRCE facility
Dipartimento
INGEGNERIA CIVILE E INDUSTRIALE
Corso di studi
INGEGNERIA NUCLEARE
Relatori
relatore Prof. Ambrosini, Walter
relatore Dott. Forgione, Nicola
relatore Dott. Del Nevo, Alessandro
relatore Dott. Tarantino, Mariano
relatore Dott. Rozzia, Davide
Parole chiave
  • HERO
  • instability
  • CIRCE
Data inizio appello
06/10/2014
Consultabilità
Completa
Riassunto
The present master thesis is devoted to the support of the experimental campaigns to be conducted in the HERO (Heavy mEtal pRessurized water cOoled tube) facility that represent the steam generator of ALFRED reactor (LFR). A focus is carried out on the assessment of thermal hydraulic nominal operating conditions of the HX and on the analysis of the 2ϕ flow instabilities by means of RELAP5/3.3. The thesis has been carried out in collaboration with the ENEA Brasimone Research Center (Italy).
The actual configuration of LFR deals with the compact pool type reactor in which the steam generators (SG) are located inside the reactor tank. In this scenario, the steam generator design plays an important role because one of the most impacting incidents is the Steam Generator Tube Rupture (SGTR) that may propagate to the near-bough tubes. In the framework of the LEADER project, an innovative configuration of SG has been proposed: the super-heated steam double wall once through bayonet type.
Two-phase flow instabilities are complex phenomena that deeply impact on the safety and design of NPP (mechanical vibrations, surface burn out, system control problems etc…) therefore it’s necessary to study them in detail. To analyze their behavior, a RELAP5/3.3 analysis has been carried out and considering the configuration of HERO; those that may impact on the operation of a bayonet tube bundle are: Ledinegg instability, flow excursion instability, parallel channel instability, DWOs (Density Wave Oscillations). This work focuses on Ledinegg (static instability) and parallel channel instability(dynamic instability): for the first one was developed a specific model by means of RELAP5/3.3 which considers the bundle as one detailed tube instead for the dynamic instability was considered a RELAP5/3.3 model of the bundle with seven detailed tubes. In both categories of instability was conducted a sensitivity analysis on the parameters that most affect their occurrence (e.g. mass flow rate, form loss coefficient) and was not observed the occurrence of instability.
The last part of the thesis deals with the analysis of the HERO-CIRCE (CIRColazione Eutettico) integral behavior through the development of a specific model by RELAP5/3.3 which considers the bundle as one tube coupled with the model of CIRCE.
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