1,720,983 research outputs found
Experimental Accelerator Driven System (xADS) Neutronic Steady State Characterisation at the EoL. G. Glinatsis
No full textThis document describes neutron characteristics and performances at the End of Life of the PDS-xADS core, fuelled by MOX fuel at two different enrichments at the Beginning of Life and cooled by LBE, characterised by an average Bum-Up rate of 22.3 MWd/Kg-HM for a fuel cycle length of 930 days at 100% of the nominal power. Observing that choices and design constraints condition the neutron performances of the reactor, using two differentiated enrichments, while it improves some neutron performances it does not turn out to be sufficient to obtain also good performances in terms of Burn-Up rate. Moreover power redistribution, temperature effect 'good answers', negative value of the void effect reactivity coefficient of the whole core are confirmed, and also small Burn-Up rates causes an appreciable 'degradation' of the void effect reactivity worth. Finally, the coolant void effect influences the neutron spectrum characteristics of the core in a considerable way
Minor Actinides Fuel Neutron Performances
No full textIn this document are pointed out the principal results of a neutronic study, focused to the 'better use' of some Minor Actinides (MA) fuel solutions at the 'maximization' purpose of 'incineration' rate. The incineration rate is intended as burning and/or transmutation rate of the MA themselves into other isotopes of reduced radio-toxicity. It is a preliminary physics study, starting from MA fuel compositions coming from pyrometallurgic (electrochemical) process and oriented to the use of a sub critical reactor, of the liquid metal ADS family, as reference reactor in the frame of the prevalent idea to assure high neutron fluxes. However the obtained results show a realization's difficulty of such a reactor concept owing to a not negligible worsening of the safety aspects and performances. Besides this, the increase of the reactivity during the life, transforming the sub critical reactor in a (over) critical reactor, requires the introduction of control systems (like control rods) extraneous to the sub critical reactor concept
Assessment of the Safety Neutron Performances of an Inert Matrix Pb-Cooled xADS Transmuter Care.
No full textThe possibility, and the consequences of the xADS reactor MOX fuel substitutation by 'Uranium Free' fuel in an inert matrix of MgO, was investigated without any modification of the core and/or plant. Firstly, the design of the xADS reactor, so as planned and characterized, isn't suitable for lodging 'Uranium Free' fuel without substantial modifications, with the purpose of mitigating/improving the impact on the core reactivities feedback. The developed investigation highlighted some aspects and problems, of the neutron design of a xADTransmuter core, which must be taken into consideration. These same preliminary results suggest a 'meditation' about safety criteria and/or design constraints concerning a sub-critical Transmuter core, as well as the minor actinides available nuclear data need a 'critical review'
Decay Heat Investigation on the U-Free Transmuter Cores Dedicated Fuels.
No full textPerformances and consequences of the Uranium Free' fuel use, instead MOX fuel for Transmuter Cores: e.g. EFIT-MgO/Pb-Cooled, was investigated in terms of decay heat production and possible relapses on the core and reactor plant designs. The developed investigation highlighted some aspects of the Minor Actinides (MA) impact, related to their nuclear properties, that involve 'to reconsider' the concept of the reliability of the reactor plant components, dedicated to the decay heat removal, mainly in terms of length in the time. Sono state investigate prestazioni e conseguenze dell'uso di combustibile 'Uranium Free' , in sostituzione del combustibile MOX per nocciolo trasmutatore: ad es. EFIT-MgO/Pb-Cooled, in termini di potenza di decadimento ed eventuali ricadute sul progetto di nocciolo e di impianto. L'indagine svolta ha evidenziato alcuni aspetti dell'impatto degli attinidi minori, legato alle loro proprietà nucleari, che implicano una 'rivisitazione' del concetto di affidabilità di componenti d'impianto, dedicati alla rimozione del calore di decadimento, soprattutto in termini di durata nel tempo
Safety Aspects of the EFIT / MgO - Pb Core
No full textAbstracts Performances and consequences, from safety point of view, of the EFIT-Pb cooled care fuelled by 'Uranium Free' distribution. The developed investigation highlighted some aspects and problems, of the neutron design of the EFIT-MgO/Pb coaled care, which must be taken inta cansideratian. These same preliminary results suggest a 'meditation' about safety criteria and/or design constraints concerning a sub-critical Transmuter care, as well as the minor actinides available nuclear data need a 'critical review'. Sommario Sono state investigate prestazioni e conseguenze, principalmente dal punta di vista sulla sicurezza, del nocciolo EFIT-Pb alimentata a combustibile 'U-free' in matrice inerte MgO, facendo usa di barrette di combustibile forate allo scopa di appiattire la distribuzione delle potenze. L'indagine svolta ha evidenziato alcuni aspetti e problematiche, del progetto neutronico del nocciolo EFIT-MgO/Pb, che devono essere comunque prese in considerazione. Questi stessi risultati preliminari, suggeriscono un 'ripensamento' dei criteri di sicurezza e/a vincoli di progetto e di alcuni concetti legati ai sistemi sottocritici, così come necessitano una 'revisione' critica i dati nucleari di base disponibili per gli attinidi minori, e non solo per essi
Coolant Void Effect Optimization of an Inert Matrix Pb-Cooled xADS Transmuter Core
No full textThis analysis arises from the necessity to 'improve' the reactivity coefficients of a xADTransmuter core fuelled by 'Uranium Free' fuel in MgO inert matrix. In fact, it was already highlighted that there is necessity of a 'second thoughts' of the safety criterions and/or design constrains as well as some concepts related to the suberitical systems, that is to 'trace back' the reactor safety reactivity coefficients to values consistent with the Subcritical System Concept. This appears possible without 'penalizations' of the core geometry assuring. in such a way, the possibility of using the 'natural convection' for the removal of the residual power. It is clear that, such solution need to be verified for each core configuration different from the analysed one, and verified in terms of Minor Actinides, loaded in the core, efficiency of the transmutation/burning process
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