The paper studies the effect of the distribution of the fissile material in a nuclear system on its multiplication properties. Some general results and specific examples on the dependence of the value of the effective multiplication constant on the fuel distribution are presented. The approach to the problem is established on a rather general mathematical ground, referring to a variational approach which leaves room to add constraints, when needed. Examples in one-and two-group diffusion are illustrated. It is well known that the effective multiplication factor of a homogeneous system can be increased by the addition of a reflector but it is not obvious that it is possible to obtain an effective multiplication factor larger than the value of the infinite medium multiplication factor of the material constituting the core region. This can never happen in a one group model, as can be easily demonstrated, for instance, in diffusion theory. However, when taking into account spectral effects related to slowing down phenomena, it is shown in this work that such a situation can be realized by a proper choice of the reflector material. Some analyses are carried out in the frame of two-group diffusion theory and comparisons are performed with Monte Carlo evaluations.

Neutron multiplication and fissile material distribution in a nuclear reactor / Saracco, P.; Chentre, N.; Abrate, N.; Dulla, S.; Ravetto, P.. - In: ANNALS OF NUCLEAR ENERGY. - ISSN 0306-4549. - 133:(2019), pp. 696-706. [10.1016/j.anucene.2019.06.044]

Neutron multiplication and fissile material distribution in a nuclear reactor

N. Abrate;S. Dulla;P. Ravetto
2019

Abstract

The paper studies the effect of the distribution of the fissile material in a nuclear system on its multiplication properties. Some general results and specific examples on the dependence of the value of the effective multiplication constant on the fuel distribution are presented. The approach to the problem is established on a rather general mathematical ground, referring to a variational approach which leaves room to add constraints, when needed. Examples in one-and two-group diffusion are illustrated. It is well known that the effective multiplication factor of a homogeneous system can be increased by the addition of a reflector but it is not obvious that it is possible to obtain an effective multiplication factor larger than the value of the infinite medium multiplication factor of the material constituting the core region. This can never happen in a one group model, as can be easily demonstrated, for instance, in diffusion theory. However, when taking into account spectral effects related to slowing down phenomena, it is shown in this work that such a situation can be realized by a proper choice of the reflector material. Some analyses are carried out in the frame of two-group diffusion theory and comparisons are performed with Monte Carlo evaluations.
File in questo prodotto:
File Dimensione Formato  
1-s2.0-S0306454919303627-main.pdf

non disponibili

Tipologia: 2a Post-print versione editoriale / Version of Record
Licenza: Non Pubblico - Accesso privato/ristretto
Dimensione 2.23 MB
Formato Adobe PDF
2.23 MB Adobe PDF   Visualizza/Apri   Richiedi una copia
Pubblicazioni consigliate

I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.

Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11583/2742694
 Attenzione

Attenzione! I dati visualizzati non sono stati sottoposti a validazione da parte dell'ateneo