A nuclear instrumentation system for weighting during refueling

Scales to weigh the fuel of a nuclear plant have been developed. The scales are going to be exposed to radiation, so must be built carefully and materials must be adequate for these extreme conditions. The input to the scales comes from a strain gauge which provides a signal ranging from a 0 mV to 5.4 mV. The scales have two modules: the analog and digital modules. The signal amplification and conditioning is carried out in the analog module. The 0-5.4 mV input voltage signal is converted into a 4-20 mA current signal, which is the input to the digital module. The 4-20 mA signal is converted into a 0-10 V voltage signal, which goes to an A/D converter and is shown on a digital display. Moreover, the scales have other outputs: eight relays (220 V, 1.25 A) which are activated depending on the fuel weight. When the values of the fuel weight reach a fixed value a relay is activated. These activation values can be adjusted independently for each relay. Experimental results show high precision and accuracy.