Development of a transfer model for the design and the operation of sodium purification systems for fast breeder reactors

Abstract

Operating a Sodium Fast Reactor (SFR) in reliable and safe conditions requires mastering the quality of the sodium fluid coolant, regarding oxygen and hydrogen impurities contents. A cold trap is a purification unit in SFR, designed to maintain oxygen and hydrogen contents within acceptable limits. The purification of these impurities is based on crystallization of sodium hydride on cold walls and sodium oxide or hydride on wire mesh packing. Indeed, as oxygen and hydrogen solubilities are nearly nil at temperatures close to the sodium melting point, i.e., 97.8 °C, on line sodium purification can be performed by cooling down liquid sodium flows and promoting crystallization of sodium oxide and hydride. However, the management of cold trap performances is necessary to prevent from unforeseen maintenance operations, which could induce shut‐down of the reactor. It is thus essential to understand how a cold trap fills up with impurities crystallization in order to optimize the design of this system and to overcome any problems during nominal operation. This paper deals with the mathematical modelling of crystallization process in a cold trap and predicts the location and the amount of the impurities deposit, on cold walls for sodium hydride and on wire mesh packing for sodium oxide. A model of the front propagation by “diffuse deposit interface method” was developed and sensitivity to various parameters was evaluated. These results will enable to understand the consequences of the impurities deposited on the hydrodynamics and heat transfer in a cold trap.

Nucleation and growth of lead oxide particles in liquid lead-bismuth eutectic

“…For PbO nucleation in LBE one can assume that the formed nuclei are only consisting of pure PbO, removing the summation from the formula above. Lehmann et al 18 give an overview of different approaches to approximate G. The temperature T (directly and, via the oxygen diffusion coefficient in LBE, indirectly), oxygen concentration C O and the critical radius r c (eqn (10)) all have an influence on the value of G. The Zeldovich factor Z is a measure for the number of oxide monomers needed to change the energy of a critical nucleus by more than k B T, with k B the Boltzmann constant. It also accounts for the possible decay of critical nuclei to smaller sizes.…”

“…Sodium fast reactors rely on cold trap purification systems for reliable operation. 10 Cold trap filtration can be applied to LBE cooled reactors to prevent the formation of PbO in the primary circuit. However, such purification systems cannot be designed for LBE cooled systems without knowledge on the PbO nucleation and growth kinetics.…”

Analysis for effects of electrolyte level on energy consumption in magnesium electrolysis by finite element method

“…Many factors affecting the cell voltage, such as current intensity or cell structure variation with different electrolyte depth, were investigated to see their effects on reducing the cell voltage. A finite element software COMSOL which is good at dealing with industrial‐scale setups was used to solve the problem . Through analyzing the energy consumption in the anode, cathode, and each part of electrolyte, the suitable electrolyte depth can be obtained.…”

“…A finite element software COMSOL which is good at dealing with industrial-scale setups was used to solve the problem. [29][30][31] Through analyzing the energy consumption in the anode, cathode, and each part of electrolyte, the suitable electrolyte depth can be obtained. The results of the study will be useful for magnesium electrolysis production because the suitable electrolyte depth can lead to less energy and electrolyte consumption.…”