On the Employment of a Chloride or Fluoride Salt Fuel System in Advanced Molten Salt Reactors, Part 1: Thermophysical Properties and Core Criticality

Abstract

Molten salt reactors (MSRs), as one of the six main technologies of Gen IV, can meet the broad area of sustainability, economics, safety and reliability, proliferation resistance and physical protection goals. One of the main and first challenges in designing molten salt fast reactors (MSFRs) is the selection of an appropriate molten salt fuel system based on the envisaged applications and objectives. In this study’s series, a full-scope evaluation has been conducted about employing either chloride or fluoride salt fuels as the main competitors’ candidates for fuel salt in MSFR designs. Two distinguished projects, EVOL (CNRS, Grenoble-France), based on fluoride salt, and iMAGINE (The University of Liverpool, UK), based on chloride salts, were considered in order to achieve this goal as case studies. The first part of this series (part 1—this article) deals with the investigation of the thermophysical properties of the salt fuel system, criticality search and neutron-flux energy spectrum. An identical typical design of the MSFR core has been considered for a neutronic simulation by using MCNPX V2.7 based on the chemical composition of the fuel salt mentioned in both projects. The thermophysical evaluation has been conducted through literature research and theoretical methods based on the experimental values for the salt component properties. The results of the study are presented for thermophysical properties, including the melting point, vapour pressure/boiling point, specific heat capacity, thermal conductivity and density, in addition to neutronic simulation for the core critical dimension and neutron-flux spectrum of both the chloride- and fluoride-based salt fuel systems. In the discussion of the results, it is concluded that both the chloride and fluoride salt fuel systems have benefits that are seen on different comparative parameters. The delivered data will provide future decision makers with evidence for the salt choice for balancing their design objectives with the opportunities and expectations. Thus, a final selection of the most appropriate salt fuel system to be used in MSFRs will be postponed for more investigation in the final part of this article series, combining the data with different potential user profiles.

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

“…In this section, the output of the iMAGINE-3BIC package will be presented and concluded in three different sections: (i) iMAGINE-3BIC package sample outputs, (ii) B&B comparison of chloride-and fluoride-based MSFRs, and, finally, (iii) salt clean-up operations. Following the first part of this article series [41], iMAGINE-Eutetic (chloride-based) and EVOL (fluoride-based) MSR designs were selected as case studies. The complete design and operational parameters of these reactor types employed to obtain the following results can be found in [39,43].…”

“…During the development of the iMAGINE-3BIC package, the complete burnup/core inventory output parameters (from CINDER90-based on ENDF/B-VII.1) of iMAGINE Eutectic/HMR [41] and EVOL [45] cores were accumulated in the database at 50 time steps over 100 years of reactor lifetime (this procedure can be easily repeated for other design or reactor types), and as mentioned earlier, this database is accessible to other package modules. This procedure helps the MLR and salt clean-up module to extract the required parameters from the database and process it on the user-requested timestep without repeating the burnup calculation for that certain time.…”

“…The main goal of this article series starting from the first part (Part 1: Thermophysical Properties and Core Criticality [41]) followed by this manuscript is to compare the pros and cons of using chloride-and fluoride-based salt fuels for MSFRs. In this section, iM-AGINE and EVOL cores, which represent the chloride and fluoride-based salt fuels, respectively, are compared with regard to burnup/core inventory employing the iMAGINE-3BIC package (Table 5 lists their initial (fresh) salt fuel composition [41]). Figure 13 and Table 6 depict the actinides inventory of iMAGINE and EVOL cores during their reactor lifetime (100 years).…”

“…However, it is worth considering that the fuel in a self-sustained breeder MSFR core (like iMAGINE) is just U 238 in the longer-term operation, which makes distinguished benefits for the design. The main reason for this phenomenon is the harder neutron flux-energy spectrum of the iMAGINE reactor core as compared to the EVOL core(which has been explained in detail in Figures 9 and 10 in [41]) and, moreover, the composition of the salt fuel system. It also originated from one of the main design philosophies of the iMAGINE design that achieves self-sustained breeding in a homogeneous core.…”

“…Following the first part of this work [41], in this study, a new code package entitled "iMAGINE-3BIC" has been developed for an entire evaluation of burnup and core inventory during the MSR/MSFRs' lifetime. The iMAGINE-3BIC package includes its dedicated burnup and core inventory database resulting from using the CINDER90 module of MCNPX-based on iMAGINE and EVOL (as chloride-and fluoride-based MSFRs).…”