Design and optimization of radioisotope sources for betavoltaic batteries

Abstract

A Monte Carlo source model using PENELOPE was developed to investigate different tritiated metals in order to design a better radioisotope source for betavoltaic batteries. The source model takes into account the self-absorption of beta particles in the source which is a major factor for an efficient source design. The average beta energy, beta flux, source power output, and source efficiency were estimated for various source thicknesses. The simulated results for titanium tritide with 0°and 90°angular distributions of beta particles were validated with experimental results. The importance of the backscattering effect due to isotropic particle emission was analyzed. The results showed that the normalized average beta energy increases with the source thickness, and it reaches peak energy depending on the density and the specific activity of the source. The beta flux and power output also increase with increasing source thickness. However, the incremental increase in beta flux and power output becomes minimal for higher thicknesses, as the source efficiency decreases significantly at higher thicknesses due to the self-absorption effect. Thus, a saturation threshold is reached. A low-density source material such as beryllium tritide provided a higher power output with higher efficiency. A maximum power output of approximately 4 mW/cm 3 was obtained for beryllium tritide with SiC. A form factor approach was used to estimate the optimum source thickness. The optimum source thickness was found near the thickness where the peak beta particle average energy occurs.

Planar and textured surface optimization for a tritium‐based betavoltaic nuclear battery

“…The standard approach to minimize nuclear‐battery volume and contain tritium is metal tritides. The theoretical specific activity ( A m in Ci/g) range of the metal tritides is 605.39 Ci/g (Sc 3 H) to 3860.8 Ci/g (Be 3 H 2 ) . The most experimentally proven metal tritide is titanium tritide (Ti 3 H x ), with a theoretical A m of 1076 Ci/g to 1077.63 Ci/g based on Ti 3 H 2 .…”

“…Research efforts to increase the energy transfer between the radioisotope and transducer fall into three categories: 1) planar and 3‐D coupling configuration optimization, 2) equal or similar transducer and radioisotope source volume, and 3) increase A m and η β . 1) the optimization of planar coupling configuration using analytical and numerical methods was attempted with metal tritides and SiC (transducer), promethium‐147 ( 147 Pm) and SiC (transducer), and nickel‐63 ( 63 Ni) and 147 Pm with various semiconductor converters . Rahmani et al, Kim et al, and Wu et al used a combination of closed form equations and Monte Carlo simulations to maximize nuclear and electrical power output based on a defined domain (i.e., radioisotope source layer thicknesses and dopant concentrations of the semiconductor junctions).…”

“…Rahmani et al, Kim et al, and Wu et al used a combination of closed form equations and Monte Carlo simulations to maximize nuclear and electrical power output based on a defined domain (i.e., radioisotope source layer thicknesses and dopant concentrations of the semiconductor junctions). However, η was never maximized nor prioritized in these publications …”

Investigation of nickel‐63 radioisotope‐powered GaN betavoltaic nuclear battery

“…Two more parameters should be included in order to estimate the total system efficiency: backscattering from GaN surface 56 and absorption in air between source and semiconductor.…”

Enhanced novel dual effect isotope batteries: Optimization of material and structure

“…In the study of RV effect isotope batteries, the radioactive sources of these batteries are mostly beta (β) sources, such as Ni‐63, Pm‐147, and S‐35. The types of conversion units that match those sources include inorganic semiconductors (GaAs, Si, GaN, and SiC), organic semiconductors (P3HT), and nano‐semiconductor materials. The use of low‐energy β sources can effectively avoid the problem of rapid decline of battery performance, but it also results in a low output performance.…”