Multiobjective genetic algorithm strategies for electricity production from generation IV nuclear technology

Development of a technico-economic optimization strategy of cogeneration systems of electricity/hydrogen, consists in finding an optimal efficiency of the generating cycle and heat delivery system, maximizing the energy production and minimizing the production costs. The first part of the paper is related to the development of a multiobjective optimization library (MULTIGEN) to tackle all types of problems arising from cogeneration. After a literature review for identifying the most efficient methods, the MULTIGEN library is described, and the innovative points are listed. A new stopping criterion, based on the stagnation of the Pareto front, may lead to significant decrease of computational times, particularly in the case of problems involving only integer variables. Two practical examples are presented in the last section. The former is devoted to a bicriteria optimization of both exergy destruction and total cost of the plant, for a generating cycle coupled with a Very High Temperature Reactor (VHTR). The second example consists in designing the heat exchanger of the generating turbomachine. Three criteria are optimized: the exchange surface, the exergy destruction and the number of exchange modules

Optimization of electricity / hydrogen cogeneration from generation IV nuclear energy systems

One of the great motivations of studying and developing Generation IV (Gen IV) reactors of VHTR (Very High Temperature Reactor) design concept is their capacity to efficiently produce both electricity and H2 (hydrogen). This study aims at developing an optimization methodology for cogeneration systems of H2 and electricity, from Gen IV nuclear reactors, with respect to energy constraints, economics and conjuncture in term of demand. It lies within a scope of a collaboration between the Laboratoire de Génie Chimique (Toulouse, France) and the Commissariat à l’Energie Atomique (CEA, Cadarache, France) in order to compare various cogeneration systems from both energy and economics viewpoint. This paper presents the results of an optimization study based on the “minimal destruction of exergy” or “exergy loss” concept. This criterion, used within the framework of a mono-objective genetic algorithm optimizer, was applied successfully to electric and heat production from Gen IV systems

Exergy analysis for Generation IV nuclear plant optimization

This article deals to the application of exergy concept to the energy production system involving a VHTR (Very High Temperature Reactor) coupled with an innovative electricity-generating cycle. The objective is to propose a general formulation to quantify the exergy destruction of the involved process components embedded in a thermodynamic simulator CYCLOP (Haubensack, 2004). The exergy destruction is thus identified as a major criterion to minimize. For this purpose, a genetic algorithm embedded in the so-called MULTIGEN environment is used. Finally, the optimization criterion, based on exergy destruction minimization, is applied to electrical production by a Brayton-Rankine combined cycle connected to a nuclear reactor. Some typical results are presented. The perspectives of this work including the cogeneration of hydrogen and electricity are highlighte

Radial viscous fingering in miscible Hele-Shaw flows: A numerical study

A modified version of the usual viscous fingering problem in a radial Hele-Shaw cell with immiscible fluids is studied by intensive numerical simulations. We consider the situation in which the fluids involved are miscible, so that the diffusing interface separating them can be driven unstable through the injection or suction of the inner fluid. The system is allowed to rotate in such a way that centrifugal and Coriolis forces come into play, imposing important changes on the morphology of the arising patterns. In order to bridge from miscible to immiscible pattern forming structures, we add the surface tensionlike effects due to Korteweg stresses. Our numerical experiments reveal a variety of interesting fingering behaviors, which depend on the interplay between injection (or suction), diffusive, rotational, and Korteweg stress effects. Whenever possible the features of the simulated miscible fronts are contrasted to existing experiments and other theoretical or numerical studies, usually resulting in close agreements. A number of additional complex morphologies, whose experimental realization is still not available, are predicted and discussed. © 2008 The American Physical Society

Conceptual design of ASTRID fuel sub-assemblies

International audienceThe French 600 MWe Advanced Sodium Technological Reactor for Industrial Demonstration (ASTRID) project has reached the end of its Conceptual Design phase. The core design studies are being conducted by the CEA with support from AREVA and EDF. Innovative design choices for the core have been made to comply with the GEN IV reactor objectives, marking a break with the former Phénix and SuperPhénix Sodium Fast Reactors. The main objective to improve safety compared with current GEN II or III reactors led to a core design that demonstrates intrinsically safe behaviour. A negative sodium void worth is achieved thanks to a new fuel sub-assembly design including (U,Pu)O$_2$ and UO$_2$ axially heterogeneous fuel pins, a large cladding/small spacer wire bundle, a sodium plenum above the fuel pins, and upper neutron shielding with both enriched and natural boron carbide (B$_4$C) which also maintain a low secondary sodium activity level. As these Na-bonded B$_4$C pins can lead to the retention of unacceptable amounts of sodium, the whole upper neutron shielding has been made removable on-line through the sub-assembly head just before the washing operations. Finite elements calculations have been performed to increase the stiffness of the stamped spacer pads in order to analyse its effect on the core mechanical behaviour during hypothetical radial core flowering and compaction events. More generally, all design choices for ASTRID have been made with the permanent objective of minimising the sub-assembly height to decrease the overall costs of the boiler reactor and the fuel cycle. This paper describes the fuel sub-assembly design for the ASTRID CFV v4 core at the end of the Conceptual Design phase (AVP2). Focus is placed on innovations and specificities in the design compared with former French SFRs