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BackgroundNuclear reactors have become the main energy supply for future manned Mars exploration missions due to their high energy density, high power-mass ratio and small size. Heat pipe molten salt reactor is an innovative concept combining molten salt reactor and high temperature heat pipe technology.PurposeThis study aims to carry out preliminary neutronics design of a martian surface molten salt reactor (MS)2R core with 1 MWth and a lifetime longer than 5 a.MethodsFirst of all, the core model of (MS)2R was estabished according to the requirements. It mainly included active zone (including fuel salt and heat pipe), active zone wall, reflector, reactor vessel, etc. Then, the MCNP (Monte Carlo N particle Transport Code) and MOBAT were used to optimize the core size and reactivity control of (MS)2R.ResultsThe physical design parameters of the core are obtained: the height and diameter of the core are 90.94 cm and 88.94 cm, respectively, the uranium inventory is 146.08 kg, and the core mass is 2.09×103 kg. Reactivity control is achieved by a control drum system, in which the B4C (10B enrichment is 90%) with a thickness of 1.8 cm and a wrap angle of 120° is used as the neutron absorber.ConclusionsThe control drum arrangement can meet the critical safety requirements during the lifecycle of (MS)2R under full power (1 MWth) operation for five years, and the number of heat pipes can meet the heat transfer safety limit. This study provides a basic theoretical reference for the design of planet surface molten salt reactor.

BackgroundThe research focus of accident tolerant enhanced thermal conductivity nuclear fuel mainly lies in the optimization of the preparation process and the improvement of the thermal conductivity whilst the control of microstructure is one of the main means to improve the thermal conductivity. So far the fault tolerant fuel in the world is mainly adding high thermal conductivity particles into the matrix particles to improve the thermal conductivity of fault tolerant fuel.PurposeThis study aims to evaluate the influence of fault-tolerant fuel structure on thermal conductivity.MethodsFirst of all, a three-dimensional finite element model of fault-tolerant fuel was established. Then, based on Ansys Workbench and this model, thermal conductivities of different fault-tolerant fuel were calculated by simulation. Effects of the shape and space of the beryllium oxide particles added to uranium dioxide matrix on thermal conductivity were analyzed.Results & ConclusionsThe variations of thermal conductivity with the shape, spatial orientation and allocation of beryllium oxide particles are obtained. It provides a reference for the selection of fault tolerant fuel.

In order to improve the security and increase the discharge burnup of the reactor, nuclear materials UN and U3Si2 have been considered for their higher densities and breeding ratios compared with uranium dioxide. A specific modeling of Tristructural isotropic particles with UN and U3Si2 as nuclear fuels was developed, and its failure probability was evaluated under irradiation conditions typical of a Molten Salt Reactor. The dimensional changes of the fuel particle kernel and layers were given. The stresses in the pyrolytic carbon and silicon carbide layers caused by the kernel gas pressure under normal operating conditions are calculated alone with the failure probability of the coated particle. The finding of this study will facilitate the development of new coated particulate fuels as well as support fuel parameters for design and construction of nuclear reactors. [ABSTRACT FROM AUTHOR]

Let G be an r-uniform hypergraph of order n. For each p ≥ 1 , the p-spectral radius λ (p) (G) is defined as λ (p) (G) := max | x 1 | p + ⋯ + | x n | p = 1 r ∑ { i 1 , ... , i r } ∈ E (G) x i 1 ⋯ x i r . The p-spectral radius was introduced by Keevash-Lenz-Mubayi, and subsequently studied by Nikiforov in 2014. The most extensively studied case is when p = r, and λ (r) (G) is called the spectral radius of G. The α-normal labelling method, which was introduced by Lu and Man in 2014, is effective method for computing the spectral radii of uniform hypergraphs. It labels each corner of an edge by a positive number so that the sum of the corner labels at any vertex is 1 while the product of all corner labels at any edge is α. Since then, this method has been used by many researchers in studying λ (r) (G). In this paper, we extend Lu and Man's α-normal labelling method to the p-spectral radii of uniform hypergraphs for p ≠ r ; and find some applications. [ABSTRACT FROM AUTHOR]