Search

The radiation tolerance testing of materials or opto-electronic components in a nuclear reactor requires a careful determination of the different components of the mixed gamma-neutron field. While the characterization of the neutron field can be performed using, for example, activation foils and validated by Monte-Carlo computation codes, the experimental measurement of the in-reactor gamma dose rate requires the use of costly ionization chambers. In this paper, we evaluate the possibility of using Red Perspex from Hanvell Technologies for routine gamma dosimetry in mixed gamma neutron field. Self-powered gamma detectors and ionization chambers were used as reference dosimeters. We show that the accuracy of the Red 4034 dosimeter's is better than 10% in mixed gamma-neutron fields. [ABSTRACT FROM AUTHOR]

Abstract: Gamma radiation-induced optical absorption in 75SiO2–22Na2O–3CaO (wt.%) multi-component glass and in the same glass additionally doped with 0.05wt.% CeO2 has been studied, with irradiations performed at 70, 200, and 350°C, 25kGy/h up to a dose of 0.6MGy. For the undoped glass irradiation at 70°C produces strong optical absorption from 700nm down to the UV. Irradiation at 200°C gives a lower level of optical absorption with a similar band composition. No induced optical absorption has been detected after irradiation at 350°C. Annealing at 200°C for 24h completely suppresses the induced optical absorption. Introduction of cerium increases the level of induced absorption in the UV range for irradiation at 70°C, and also creates bands stable up to 350°C. The results show that silica and sapphire, which are considered as main candidate materials for ITER diagnostic windows and other optical components, can potentially be complemented with multi-component silicate glasses. These materials may allow one to control the radioluminescence, and in addition provide a range of refractive indices required for achromatic lenses. [Copyright &y& Elsevier]

In-core temperature measurements are crucial to assess the condition of nuclear reactor components. The sensors that measure temperature must respond adequately in order, for example, to actuate safety systems that will mitigate the consequences of an undesired temperature excursion and to prevent component failure. This issue is exacerbated in new reactor designs that use liquid metals, such as for example a molten lead-bismuth eutectic, as coolant. Unlike water cooled reactors that need to operate at high pressure to raise the boiling point of water, liquid metal cooled reactors can operate at high temperatures whilst keeping the pressure at lower levels. In this paper we demonstrate the use of optical fibre sensors to measure the temperature distribution in a lead-bismuth eutectic cooled installation and we derive functional input e.g. the temperature control system or other systems that rely on accurate temperature actuation. This first-of-a-kind experiment demonstrates the potential of optical fibre based instrumentation in these environments. We focus on measuring the surface temperature of the individual fuel rods in the fuel assembly, but the technique can also be applied to other components or sections of the installation. We show that these surface temperatures can be experimentally measured with limited intervention on the fuel pin owing to the small geometry and fundamental properties of the optical fibres. The unique properties of the fibre sensors allowed acquiring the surface temperatures with a resolution of 30 mK. With these sensors, we assess the condition of the test section containing the fuel assembly during different steps of the operation of the facility, including the heating and verification of the vacuum of the loop as well as the filling and draining of the LBE loop. We also identify a simulated electrical shut-down and heating circuit failure in the primed installation. [ABSTRACT FROM AUTHOR]

Abstract: Radiation hardness assurance for ITER is based on extensive radiation testing. To be representative, these tests must involve an in situ follow-up of the radiation induced changes. SCK·CEN—the Belgian Nuclear Research Center is operating different irradiation facilities with broad possibilities of environmental control and on-line instrumentation. We describe those facilities and outline several recently completed and on-going experiments to illustrate capabilities for testing under conditions relevant for ITER. [Copyright &y& Elsevier]

This paper addresses the particular need to develop suitable fabrication techniques of glasses to improve the radiation-resistance and extend the lifetime of optical fibres in high radiation background. Two radiation hardening techniques based on hydrogen and fluorine doping of glass have been applied on step index pure silica core optical fibres. The radiation-induced optical absorption and luminescence have been measured in gamma and fission reactor irradiation conditions at SCKCEN, Mol Belgium. The experimental results show that the lowest optical absorption is achieved in the hydrogen-treated fibre sample. However, the luminescence effect remains significant in any type of fibre and cannot be reduced by the investigated radiation hardening techniques. [Copyright &y& Elsevier]