[en] The present paper illustrates some models and methods for the kinetic evaluation of neutron multiplying systems. After introducing the general physical features of time-dependent neutronics, the simple point kinetics model is analyzed, giving details on the physical meaning and mathematical structure of the equations. The spatial characterization of the neutronic transient is then investigated, with special regards to source-driven systems. It is evidenced that in a source-dominated structures, the space transients are less important than in systems departing from near criticality. The factorization technique used for quasi-static analysis is then presented and extended to source-driven systems and some considerations on the problem concerning the choice of the weighting function are made. The paper is concluded by a discussion of the physics of fluid-fuel systems, a consistent model is described and the factorization procedure is applied. (author)

[en] The objective of this workshop was to familiarize the students with the status of the R and D activities in the areas of: General Concept and System Studies, Accelerator, Target, Sub-Critical Core, Fuel Development, Fuel Cycle Studies. Participants were given a review of ADS designs presently under consideration. Participants studied the theoretical foundation of ADS design work, identified the most problematic areas as well as the limitations of the simulation methods. Based on the discussion of the impact of the present uncertainties on the performance of the ADS, the needs for data and methods development and validation work were identified. Eighteen participants from 13 different countries namely (Argentina, Brazil, Bulgaria, Belarus, Croatia, India, Indonesia, Iran, Kazakhstan, Russian Federation, Sudan, Slovakia and Turkey) took part in the Workshop

[en] This lecture describes the basic process of Accelerator-Driven Systems (ADS) is Nuclear Transmutation. One way to obtain intense neutron sources is to use a hybrid sub-critical reactor-accelerator system called just Accelerator-Driven System. The idea of producing neutrons by spallation with an accelerator has been around for a long time, since 1950. In November 1993, Carlo Rubbia proposed, in an exploratory phase, a first Thermal neutron Energy Amplifier system based on the thorium cycle, with a view to energy production. The Existing ADS Concepts are reviewed. The spallation process is explained in detail including: Spallation Neutron Yield, Spallation Neutron Spectrum, Spallation Product Distribution, Energy Deposition, Models and Codes for High-Energy Nuclear Reactions. Physics of Sub-Critical Systems is explained including: Multiplication Factor, Source Importance, Spatial flux Distribution, Source Amplification. A Review of Sub-Critical Core Experiments is presented. The second part of this paper deals Nuclear Data, and Methods for ADS Design. It includes description of the EA-MC Monte Carlo code package (Structure of the program, Neutron transport and time evolution, Nuclear Data, Geometry Modelling, Validation); Limitations in the high energy particle transport (Neutron Yield, spallation product distribution, spallation source distribution, energy deposition); Limitations in the low energy neutron transport (Methodology, Modeling of the spallation source, nuclear data below 20 MeV, statistics in the case of Monte Carlo codes); Experimental validation of neutron transport and nuclear data

[en] Growing world population with increasing energy needs, especially in the developing countries, Threat of global warming due to CO₂ emissions demands non-fossil electricity production. Nuclear will have to be part of a sustainable mix of energy production options Figures show that 350 GWe worldwide capacity is 'nuclear'. Present worldwide spent fuel (containing high Pu inventory) and HLW would need large repositories. In view of the previous facts this lecture deals Partitioning and transmutation as radioactive waste management option. Partitioning and transmutation (P and T) is a complex technology i.e. advanced reprocessing, and demand transuranics fuel fabrication plants, as well as innovative and/or dedicated transmutation reactors. In addition to U, Pu, and 129 I, 'partitioning' extracts from the liquid high level waste the minor actinides (MA) and the long-lived fission products (LLFP) 99-Tc, 93-Zr, 135-Cs, 107-Pd, and 79-Se). 'Transmutation' requires fully new fuel fabrication plants and reactor technologies to be developed and implemented on industrial scale. Present LWRs are not suited for MA and LLFP transmutation (safety consideration, plant operation, poor incineration capability). Only specially licensed LWRs can cope with MOX fuel; for increased Pu loadings (up to 100%), special reactor designs (e.g., ABB80+) are required; a combination of these reactor types could allow Pu inventory stabilization. Long-term waste radiotoxicity can be effectively reduced only if transuranics are 'incinerated' through fission with very hard neutron spectra. New reactor concepts (dedicated fast reactors, Accelerator Driven Systems (ADS), fusion/fission hybrid reactors) have been proposed as transmuters/incinerators. Significant Pu+MAs incineration rates can be achieved in symbiotic scenarios: LWR-MOX and dedicated fast reactors; fast neutron spectrum ADS mainly for MA incineration; very high thermal flux ADS concepts could also provide a significant transuranics destruction (coupled with Th fuel cycle). Reduction of long-term hazard of spent fuel or HLW by transforming long-lived radionuclides into short-lived or inactive elements is one of the main P and T objectives. Hazard reduction (P and T objective) requires very different and much more fundamental measures as compared to risk reduction. Nuclear Fuel Cycle Options are discussed: Conventional, once through fuel cycle with direct disposal of spent fuel, aqueous reprocessing fuel cycle with vitrification of high-level liquid waste (RFC) and advanced fuel cycle with partitioning of actinides