Hybrid reactors: Nuclear breeding or energy production?

Abstract

Keywords:Hybrid nuclear reactors Neutron multiplication Reactivity Tritium breeding Coolant selection After reviewing the long-standing tradition on hybrid research, an assessment model is presented in order to characterize the hybrid performance under different objectives. In hybrids, neutron multiplication in the subcritical blanket plays a major role, not only for energy production and nuclear breeding, but also for tritium breeding, which is fundamental requirement in fusion-fission hybrids. All three objectives are better achieved with high values of the neutron multiplication factor (/c-eff) with the obvious and fundamental limitation that it cannot reach criticality under any event, particularly, in the case of a loss of coolant accident. This limitation will be very important in the selection of the coolant. Some general considerations will be proposed, as guidelines for assessing the hybrid potential in a given scenario. Those guidelines point out that hybrids can be of great interest for the future of nuclear energy in a framework of Sustainable Development, because they can contribute to the efficient exploitation of nuclear fuels, with very high safety features. Additionally, a proposal is presented on a blanket specially suited for fusion-fission hybrids, although this reactor concept is still under review, and new work is needed for identifying the most suitable blanket composition, which can vary depending on the main objective of the hybrid.

The calculation of neutron flux using Monte Carlo method

“…The neutron flux increases with an increase in the heavy metals content for the selected fluids due to the fission reaction of plutonium isotopes, inelastic scattering of 7 Li and the exothermic 6 Li(n,α)T reaction of 6 Li in the Li 20 Sn 80 molten salt, (n,2n) reaction of beryllium, elastic and other nuclear reactions of atoms in the fuel zone. Therefore, in the calculation was observed that the radial neutron flux distribution decreases nearly exponentially with distance from the plasma for selected the fluids in the inboard and outboard of the reactor system.…”

“…In this study, Li 20 Sn 80 molten salt was used, which has low melting temperatures and low vapor pressure, to acquire sufficient tritium breeding. Beryllium (Be) is used as a neutron multiplier [7]. In this study, a Be zone with a thickness of 3 cm was used between the liquid first-wall and the blanket.…”

Neutronic study of an innovative natural uranium–thorium based fusion–fission hybrid energy system

“…However, for the FFHR fueled with only natural thorium, the energy gain M is relatively small (less than 2.0) in the initial operating stage, which would be challenging on the fusion capability requirement for energy generation (Piera et al, 2010;Lafuente and Piera, 2011). ITER is an experimental fusion reactor which has been investigated extensively for years.…”

Radiation Damage Investigation on Certain Alternative Fluids in a Hybrid System by Using MCNPX Monte Carlo Radiation Transport Code

“…Beryllium (Be) is used as a neutron multiplier. The Be(n,2n) reaction has an effective threshold of 2.5 MeV, above which the cross-section value is 0.5 barns [6]. In this study, a Be zone with a * e-mail: mehtap.gunay@inonu.edu.tr thickness of 3 cm was used between the liquid first-wall and the blanket.…”