Studies of high linear energy transfer dosimetry by ¹⁰B(n,α)⁷Li reactions in aqueous and organic solvents

Abstract

Advanced chemical treatment processes such as aqueous separation techniques can be used to separate the reusable materials from used nuclear fuel, reducing the radiotoxicity and storage time of the remaining waste. The degradation of chemicals in these processes has been studied utilizing gamma radiation. However, radiolytic degradation by internal alpha emitters has not been as widely investigated due to the difficulty of finding appropriate internal sources. This work presents results using a method to produce alpha particles in situ in aqueous and organic solvents representative of liquid–liquid extraction systems. The method is based on the widely studied ¹⁰B(n,α)⁷Li reaction which has previously been studied in aqueous solutions. Neutrons were supplied from the UCI TRIGA^® nuclear reactor. Comparisons were also made to gamma radiation from a ¹³⁷Cs source. We report that the method is useful for inducing high linear energy transfer (LET) doses in aqueous and organic solutions. We used the classic iron sulfate-based Fricke dosimeter for dosimetry in aqueous solutions and methyl red (2-[(4-dimethylaminophenyl)diazenyl]benzoic acid) dissolved in n-dodecane for organic solvents. High LET doses in both aqueous and organic solvents are well described and a simple linear relationship was found based on the neutron flux and total boron concentration. We have established, using spectroscopic determination, that methyl red degrades in a linear fashion with absorbed dose up to 80 kGy and G-values for the methyl red degradation in n-dodecane were found to be 4.66 × 10⁻⁴ μmol/J for external ¹³⁷Cs gamma radiation and 3.0 × 10⁻⁵ μmol/J for ¹⁰B(n,α)⁷Li induced high LET radiation.