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Application of coupled 3D neutron kinetic / therma hydraulic tools and methods to the safety analysis of PWRs

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CHAPTER 1. STATE-OF-THE-ART BE COUPLED TECHNIQUES 3 (see chapter 6) and Control Rod Ejection (CRE) accidents. In this latter case considerable deformation of the radial and axial power dis- tributions occur in the core. if there are possibilities for re-criticality in the later phase of the transient during the cool down phase. This is particularly emphasized for high values of moderator temperature coefficient, for increased high burn-up fuel (see appendix 8.2.1), or for extended use of MOX fuel. the local boron dilution accident in PWR and VVER. The boron concentration is often non uniformly transported into and through the reactor core causing a reactivity transient that could be severe (see chapter 8). all Anticipated Transients Without Scram (ATWS) and other Be- yond Design Basis Accidents (BDBA) need more sophisticated calcula- tions to eliminate any uncertainty due to spatial effects. In fact, using fewer dimensions in the core modeling did in some cases change the whole accident scenario. • the BWR stability issues in plant conditions and beyond the stability threshold • nuclear power improvement programs which generate the demand for reducing uncertainties. 1.2 SOA Codes Three main typologies of complex codes are required for the application of 3D coupled techniques: • code for deriving suitable neutron kinetics cross-sections (CSC = cross section code), such as CASMO-3, CASMO-4, PHOENIX, HELIOS, CPM-3, APOLLO2 and TRASLAT; • thermal-hydraulic system code (THSC), such as ATHLET, RELAP5- 3D, CATHARE-2, TRAC-PF1, TRAC-M (TRACE), TRAC-BF1 and POLCA-T; • neutron kinetics code (NKC), such as DYN3D, QUABOX, NESTLE, PARCS and NEM. CSC can be used out of the line while THSC and NKC must be coupled and interact at each time step. In the frame of this thesis, cross-sections have been generated with CASMO-4 and transients have been simulated with RELAP5-3D, which constitutes a serial integration between RELAP5 THSC and NESTLE NKC (see fig. 1.1).

Anteprima della Tesi di Angelo Lo Nigro

Anteprima della tesi: Application of coupled 3D neutron kinetic / therma hydraulic tools and methods to the safety analysis of PWRs, Pagina 5

Tesi di Dottorato

Dipartimento: Dip. Ing. Meccanica Nucleare e della Produzione

Autore: Angelo Lo Nigro Contatta »

Composta da 165 pagine.

 

Questa tesi ha raggiunto 822 click dal 03/10/2005.

 

Consultata integralmente 3 volte.

Disponibile in PDF, la consultazione è esclusivamente in formato digitale.