Equilibrium core design methods for molten salt breeder reactor based on two-cell model

Abstract

Two unit-cell-based core design methods are presented for a molten salt breeder reactor (MSBR) equilibrium core with online reprocessing and refueling: a single-cell method and a two-cell method. The single-cell method adopts a representative single unit cell which has the same fuel-to-moderator volume ratio as the average value of an MSBR core which actually consists of two zones with different ratios. The two-cell method uses two representative unit cells, one for each zone, with each zone having the appropriate fuel-tomoderator ratio. It is demonstrated that the two-cell-based method is able to catch the neutron physics of spectral interaction of the two zones with different neutron energy spectra, whereas the single-cell method cannot accurately predict the breeding ratio nor the resonance escape probability of the MSBR core. A new code system was established using MCNP6/PYTHON script language for modeling of the online reprocessing of molten fuel, and the depletion and online refueling of the MSBR core.

Online Reprocessing Simulation for Thorium-Fueled Molten Salt Breeder Reactor

“…MCNP) or deterministic (i.e. SCALE) methods for depletion and supplement these with custom Python scripts to capture the impacts of reprocessing [5,9]. Serpent 2 is the first commonly used Monte Carlo software to support continuous material reprocessing.…”

“…This suggested method takes into account fuel salt composition changes due to online reprocessing and refueling based on the deterministic computer code NEWT in SCALE [4]. This approach was later used by Jeong et al to find an equilibrium fuel composition for the MSBR and was validated with a Monte Carlo N-Particle code (MCNP)/CINDER90 model [5]. 1 Examples include both liquid-fueled molten salt designs from Transatomic, Terrapower, Terrestrial, and Thorcon.…”

A Systems Processing Model for Molten Salt Reactors

“…Including [2,3], the early analyses of the MSR system focus on the equilibrium state of the reactor where fission products accumulates in the fuel salt as the fuel salt undergoes irradiation [4][5][6][7][8]. With the advancement of powerful simulation tools, recent analysis focus has shifted to the isotopic composition variation of the fuel salt from the startup to the equilibrium condition of the MSR system by modifying neutron transport and depletion codes to account for the continuous feeds and removals in the MSR systems [9][10][11][12][13][14][15][16][17][18][19][20][21].…”

Molten salt reactor neutronics and fuel cycle modeling and simulation with SCALE

“…(5) MCODE (Xu et al, 2002), which uses MCNP neutron transport with ORIGEN2 (Ludwig and Renier, 1989) depletion in applications (Ahmad et al, 2015) to the denatured molten salt reactor (DMSR), (Engel et al, 1980), and (6) MCNP6 neutron transport with CINDER90 (MCNP6) depletion in applications to whole core (Park et al, 2015) and multi-zone (Jeong et al, 2016) MSR modeling and simulations.…”

“…For cores with large variations in spectra (e.g., those with thermal and fast zones), adding zones to the multi-zone models more accurately describes the core spectrum, reducing the effect from these spectral differences. For thermal systems like the MSBR (with moderated and low-moderated zones), simple two-zone models have been shown to sufficiently capture the core depletion (Jeong et al, 2016). Note that for a whole-core ChemTriton model, the appropriate power sharing and flux spectrum are already determined by the SCALE/TRITON calculation.…”