A. Rene Raffray

Thermo-Physical Properties and Equilibrium Vapor-Composition of Lithium Fluoride-Beryllium Fluoride (2LiF/BeF2) Molten Salt

Abstract An assessment of Flibe thermo-physical properties relevant to the prompt x-rays ablation of the liquid wall is presented with emphasis given to the equilibrium vapor composition and vapor pressure. The available data sets for Flibe thermo-physical properties, which cover a very narrow range of temperature have been extended and adjusted to cover the whole range of the liquid phase and to assure consistency with the estimated critical constants. Investigation of the equilibrium vapor composition showed a contradiction with previously published results regarding the stability of the mixed dimmer LiBeF3. New results for the vapor composition and total vapor pressure of Flibe also have been presented, compared to previous results, and used to calculate the temperature-dependent latent heat of vaporization.

IFE Liquid Wall Response to the Prompt X-Ray Energy Deposition: Investigation of Physical Processes and Assessment of Ablated Material

Abstract This paper considers the physical processes and material removal mechanisms associated with the energy deposition in an inertial fusion energy liquid wall from the prompt X-ray spectrum of an indirect-drive inertial fusion target. These are important as the ablated material could generate aerosol in the chamber, which without adequate chamber clearing could result in a chamber environment unsuitable for driver propagation and/or target injection. Simple computations were used to identify and characterize the important material removal mechanisms relevant to the energy deposition regime under consideration. Explosive boiling was found to be the most relevant thermal response mechanism due to the high heating rate from the X-ray photon energy deposition. Investigation showed that explosive boiling occurs when the material temperature approaches the critical temperature and has a threshold value that can be derived from the material equation of state or the rate of homogeneous nucleation. Another important mechanism is mechanical spall that can result when shock wave-induced local tensile stresses exceed the spall strength of the material. Both explosive boiling and mechanical spall occur upon crossing the thermodynamic stability border (spinodal curve) either through rapid heating or through overexpansion of the material. Relevant material properties of the candidate liquid wall materials needed to perform the present assessment are compiled, derived, and presented. A simple energy deposition volumetric analysis is used to estimate both thermally ablated and mechanically spalled regions of the liquid wall material. The choice of liquid/wall combination is found to play an important role in reducing or eliminating the occurrence of spall in the liquid wall.

Optimization of compact stellarator configuration as fusion devices

Optimization of the stellarator configuration requires tradeoffs among a large number of physics parameters and engineering constraints. An integrated study of compact stellarator power plants, ARIES-CS, aims at examining these tradeoffs and defining key R&D areas. Configurations with a plasma aspect ratio of A⩽6 and excellent quasiaxisymmetry (QA) in both two and three field period versions were developed while reducing α-particle losses to <10%. Stability to linear ideal MHD modes was attained, but at the expense of reduced QA (and increased α-particle losses) and increased complexity of the plasma shape. Recent experimental results indicate, however, that linear MHD stability limits may not be applicable to stellarators. By utilizing a highly efficient shield-only region in strategic areas, the minimum standoff was reduced by ∼30%. This allows a comparable reduction in the machine size. The device configuration, assembly, and maintenance procedures appear to impose severe constraints: three distinct ap...