Research and Development of Lead Block Cutting Technique for Decommissioning Nuclear Power Plants

Abstract

Nuclear power plants and research facilities that use radioactive materials employ lead to shield against radiation. Lead must be cut to an appropriate size before being removed from the facility as waste. Because lead is soft, it is difficult to cut using mechanical cutting methods such as reciprocating saws. In this study, we attempted to make lead into a low-melting-point alloy of bismuth and tin (eutectic point 95 °C) and devised a new cutting method that combines mechanical cutting and low-melting-point alloying. For the cutting experiment, we used a Bi-Sn alloy (eutectic point 139 °C) that we prepared and a lead block (50 mm thick). To react the Bi-Sn alloy with the lead block, it was necessary to heat the lead block to 139 °C or higher. Therefore, we conducted a temperature increase experiment on the lead block using a heating wire with thermal conduction and an infrared heater with radiation. The results showed that heating with an infrared heater was superior. The molten Bi-Sn alloy was brought into contact with the heated lead block to make a low-melting-point alloy. Here, a reciprocating saw was used to successfully cut the lead block and remove the low-melting-point alloy that had formed.