Wireless sensor networks (WSNs) are appealing options for the health monitoring of nuclear power plants due to their low cost and flexibility. Before they can be used in highly regulated nuclear environments, their reliability in the nuclear environment and compatibility with existing devices have to be assessed. In situ electromagnetic interference tests, wireless signal propagation tests, and nuclear radiation hardness tests conducted on candidate WSN systems at AECL Chalk River Labs are presented. The results are favourable to WSN in nuclear applications.

A boron-loaded liquid scintillator (LS) has been optimized for neutron detection application in a high gamma field environment. It is composed of the solvent linear alkylbenzene (LAB), a boroncontaining material, o-carborane (C2B10H12); a fluor, 2,5-diphenyloxazole (PPO); and a wavelength shifter, 1,4-bis[2-methylstyryl] benzene (bis-MSB). Preparation of the liquid scintillator and optimization of its chemical composition are described. The boronloaded LS has been tested with a neutron beam at the National Research Universal (NRU) reactor. A peak at an equivalent energy of 60 keV is observed in the energy spectrum and is attributed to neutrons. The results confirm the possibility of using B-10 loaded scintillator as a sensitive medium for neutron detection in a relatively large background of gamma rays.

A radiation imaging system has been developed using the concept of inverse collimation, where a narrow shielding pencil is used instead of a classical collimator. This imaging detector is smaller, lighter and less expensive than a traditionally collimated detector, and can produce a spherical raster image of radiation sources in its surroundings. A prototype was developed at Atomic Energy of Canada Limited – Chalk River Laboratories, and the concept has been successfully proven in experiments using a point source as well as real sources in a high ambient field area. Such a radiation imaging system is effective in locating radiation sources in areas where accessibility is low and risk of radiological contamination is high, with applications in decontamination and decommissioning activities, nuclear material processing labs, etc.

SLOWPOKE-2 (LEU core) is a pool-type nuclear reactor with a maximum nominal thermal power of 20 kW. It uses a pelletized uranium oxide fuel (19.9% enrichment) and provides a useful high neutron flux in the order of 1012 n.cm2s-1. The key safety features built into the reactor design are the strictly limited amount of excess reactivity and the negative reactivity feedback characteristics, which provide a demonstrably safe self-limiting power excursion response to large reactivity insertions. However, the limited amount of excess reactivity also limits continuous prolonged reactor operation at full power. With a 4 mk excess reactivity, the reactor can operate for about one day at full power, 20 kW, before criticality is lost due to temperature effects and xenon poisoning. A new safety concept is proposed in this paper that enables the continuous operation to a few months by increasing the excess reactivity from 4 mk to 8 mk. A Matlab/simulink model of SLOWPOKE-2 has demonstrated that core operation life can be extended to several months without adding a beryllium shim.