Features of methods for monitoring the fuel cladding tightness in lead-cooled fast breeder reactors

To timely detect failed fuel elements, a reactor plant should be equipped with a fuel cladding tightness monitoring system (FCTMS). In reactors using a heavy liquid-metal coolant (HLMC), the most efficient way to monitor the fuel cladding tightness is by detecting gaseous fission products (GFP). The article describes the basic principles of constructing a FCTMS in liquid-metal-cooled reactors based on the detection of fission products and delayed neutrons. It is noted that in a reactor plant using a HLMC the fuel cladding tightness is the most efficiently monitored by detecting GFPs. The authors analyze various aspects of the behavior of fission products in a liquid-metal-cooled reactor, such as the movement of GFPs in dissolved and bubble form along the circuit, the sorption of volatile FPs in the lead coolant (LC) and on the surfaces of structural elements, degassing of the GFPs dissolved in the LC, and filtration of cover gas from aerosol particles of different nature. In addition, a general description is given of the conditions for the transfer of GFPs in a LC environment of the reactor being developed. Finally, a mathematical model is presented that makes it possible to determine the calculated activity of reference radionuclides in each reactor unit at any time after the fuel element tightness failure. Based on this model, methods for monitoring the fuel cladding tightness by the gas activity in the gas volumes of the reactor plant will be proposed.

On Some Differences of the Thermoelectrical Effects in BN-600 and Superphenix

The paper discusses specific electromagnetic effects observed in the large circulating masses of liquid metal inherent in the heat transport systems of the commercial fast breeder reactors. It was explained why the criterion Lu of the magnetic field self-excitation in the liquid metal coolant has limiting conditions, determined by the balance nature of the thermoelectric currents circulating in reactor.

Global nuclear energy: an uncertain future

<abstract> <p>Nuclear energy currently accounts for a declining share of global electricity, but it is possible that rising concerns about global climate change and China's ambitious nuclear program could reverse this trend. This review attempts to assess the global future of nuclear power, showing how the optimistic forecasts in the early days of nuclear power have been replaced by far more modest forecasts. The review first discusses the controversies surrounding nuclear power. It then briefly examines the prospects for three proposed reactors of the future: Small Modular Reactors; Generation IV breeder reactors; fusion reactors. It finally discusses the social and political context for nuclear power, both today and in the future.</p> </abstract>

Microstructure Refinement Effect on EUROFER 97 Steel for Nuclear Fusion Application

In Europe EUROFER 97 has been recognised as reference steel for the nuclear costructions under high radiation density for first wall of a fast breeder reactors as well as in other high stressed primary structures such as the divertors, blanklet and vessels. Following to this a EUROFER 97 detailed knowledge of the microstructure evolution after thermo-mechanical processing is required, because the material mechanical properties are interesting also for innovative solar plants, i.e. NEXTOWER project. A detailed knowledge of process optimisation is mandatory because EUROFER 97 steel mechanical properties and microstruture are heavily influenced and improved (and easily affeted) by thermomechanical treatments. In this paper the effect of thermo-mechanical parameters on the grain refinement of EUROFER 97 has been investigated by cold rolling and heat treatment on pilot scale.

A study of the nuclear natural resources utilization in open and closed fuel cycles: nuclear energy a sustainable and renewable source of energy

In this work, the use of natural resources was analyzed using a simplified methodology and assuming calculation conditions close to the real ones, to assess the sustainability of the nuclear source and the efficiency in the use of these resources. For the analysis of open fuel cycles, four reactors were selected, these being the Pressurized Water Reactor (PWR) and Pressurized Heavy Water Reactor (PHWR), two Generation II reactors commonly used until today, the advanced Generation III reactor AP1000 and the conceptual reactor AP-Th 1000. For closed fuel cycles, the variation of the utilization of the natural resource alongside with the variation of the conversion factor were evaluated, parameterized by the burnup. It was observed that the Generation II reactors use only 1% of the natural resources and, despite technological advances, the Generation III reactor did not show a significant increase in comparison to the former. Although the closed fuel cycle includes recycling the burnt fuel from thermal reactors, it exploits only about 10% of the resources. Major improvements are observed in Fast Breeder Reactors, being able to obtain a use of almost 100% with the increase of the burning and the minimization of losses. Although the feasibility of using thorium as a nuclear fuel has been proven, it would be better used in a closed cycle, as in the self-sustainable Liquid Fluoride Thorium Reactor (LFTR), a Generation IV reactor that can transform the nuclear energy in a sustainable and renewable source of energy.