Breed-and-burn fuel cycle in molten salt reactors

Abstract

The operation of a reactor on an open but self-sustainable cycle without actinide separation is known as breed-and-burn. It has mostly been envisioned for use in solid-fueled fast-spectrum reactors such as sodium-cooled fast reactors. In this paper the applicability of breed-and-burn to molten salt reactors is investigated first on a cell level using a modified neutron excess method. Several candidate fuel salts are selected and their performance in a conceptual three-dimensional reactor is investigated. Chloride-fueled single-fluid breed-and-burn molten salt reactors using enriched chlorine are shown to be feasible from a neutronics and fuel cycle point of view at the cost of large fuel inventories.

Comparative Study on the Neutronic Performance of Thermal and Fast Molten Salt Reactors under Once-Through Fuel Cycle

“…The BNB fuel cycle differs from the once-through fuel cycle of fluorine salt. The BNB can realize the long-term selfsustaining burn of the fuel without using online chemical reprocessing and supply of enriched fuel [29]. Therefore, since a long-term self-sustaining burn can be achieved by adding only 238 U for chlorine salt reactors when the neutron loss ratio is low, the natural uranium burnup difference is orders of magnitude higher than that of the fluorine reactor or the chlorine reactor with a high neutron loss ratio, so it is not shown in Figure 5.…”

“…In addition, BNB fuel cycle mode is not possible for fluorine salts in both thermal and fast spectra. It is worth noting that in solid fuel fast reactors, the fuels at different burnup moments can be combined and split arbitrarily, so it is theoretically possible to establish the neutron generation and absorption equilibrium at any moment, but in molten salt reactors it is difficult to split the molten salt once it is combined, so it is difficult to separate the fuels under deep burnup, which makes the neutron equilibrium too ideal and the actually obtained burnup will be much lower than the theoretical analysis, as studied in more detail by Hombourger et al [29].…”

“…The active zone of a molten salt fast reactor core does not contain moderators, but similar to molten salt thermal reactors, there are structures such as reflectors, shields, and metal containers at the periphery of the core, with the usual reflector structures being graphite, carbonized materials, and alloys. Moderators and structural materials around the core have limited lifetimes due to neutron irradiation, high temperature, and corrosion [29,38]. The neutron irradiation lifetime of both the graphite moderator and the reflector is correlated with the fast neutron flux.…”

On the Employment of a Chloride or Floride Salt Fuel System in Advanced Molten Salt Reactors, Part 2; Core Inventory, Fuel Burnup, and Salt Clean-Up System

“…A wide range of codes and methods are usually employed for this purpose; ORIGEN [5], SCALE [1,3,18], SERPENT [20,21], perturbation theory [13], and linear chain method [35,36] are more popular, among others. The neutron spectrum of the reactor has different effects on the core inventory of MSRs and needs to be evaluated individually [5,14]. For small-scale molten salt reactors, the difference in fuel utilization under thermal and fast spectra (both iMAGINE and EVOL) is small.…”

Electroanalytical Measurements of UCl3 and CeCl3 in Molten NaCl-CaCl2

“…The effect of high actinide concentration is of particular concern, as electrorefiners typically operate at about 5-10 wt% UCl 3 , 25 while MSRs may have up to about 40 mol% (80 wt%) UCl 3 . 26 There has been a progression of pushing the composition limits for study of U and Pu in electrorefiner salts over the last 20 years. Notably, Iizuka et al first reported U and Pu concentration measurement via online electrochemical methods (SWV and NPV) in LiCl-KCl.…”