Development of A Multi-layer Silicon Beta-ray Dosemeter for CANDU Environment

There is a growing demand for precise dose assessment to the lens of eye from beta radiation at CANDU power plants. We present the design of a silicon-based beta-ray dosemeter to meet such needs. The primary objective of the dosemeter is to measure the in situ beta-ray fluence rate spectrum and monitor the dose rates for eye, skin and whole body in real-time. We aim to accomplish the minimum gamma rejection ratio 1000:1 to avoid the beta dose overestimation. To achieve the objective, the beta radiation dosemeter features a telescopic configuration of a stack of three 40 mm diameter planar Si detectors with different thicknesses that can cover a beta energy range of 70 keV to 3000 keV using the ΔE vs. E method. Customized detector housing and front-end electronics including power and preamp module are developed. A microcontroller (MCU)-based data acquisition (DAQ), control system, firmware and software are currently under development. MCNP simulations were performed to optimize the instrument design. In this paper, we report the hardware architecture, MCNP results and preliminary characterization of a prototype system.