Development of Technologies and Safety Systems for Pressurized Heavy Water Reactors in India

Abstract

The technology of pressurized heavy water reactors (PHWRs) which was developed with prime objectives of using natural uranium fuel, implementing on power fuelling, utilizing mined uranium most effectively, and achieving excellent neutron economy has demonstrated impressive performance in terms of high capacity factors and an impeccable safety record. The safety features and several technology advancements evolved over the years in which Indian contributions that are considerable are briefly discussed in the first part of the paper. Unique features of PHWR such as flexibility of fuel management, distribution of pressure boundaries in multiple pressure tubes (PTs), and a large inventory of coolant-moderator heat sink in close proximity of the core provide inherent safety and fuelling options to these reactors. PHWRs, in India have demonstrated to have the advantage of lower capital cost per megawatt even in small size reactors. Low burn up associated with natural uranium fuel, higher level of tritium in the heavy water coolant, and a slightly positive coolant void coefficient in present generation PHWRs have all been addressed in the design of advanced heavy water reactor (AHWR). The merit of adopting closed fuel cycle with partitioning of minor actinides in reducing the burden of radio-toxicity of nuclear waste and of deploying light water reactors (LWRs) in tandem with PHWRs in the evolving nuclear fuel cycle in India are also discussed.