ON THE USE OF THORIUM IN LIGHT WATER REACTORS

The advantages and disadvantages of the use of thorium bearing fuel in light water reactors have been examined several times from the beginning of the nuclear energy era until the late seventies. The recent motivation for re-examining the use of thorium in light water reactors' once-through fuel cycle is enhancing the cycle proliferationresistance due to reduced plutonium production. Additionally, economic benefits from reducing the initial enrichment needs of high burnup fuels may be obtained. Similarly, it may be possible to rely on the higher melting point and higher thermal conductivity of ThO2 to enhance the safety margin of the core. Thorium dioxide is the highest stable oxide form of thorium, which may further improve the spent fuel repository performance. The information obtained in previous studies is reviewed to assess its suitability for application to the current fuel cycle conditions. It is concluded that the thorium fuel experience of the past is insufficient to make a judgement on the feasibility and performance of the thorium bearing fuels in the reactors operating under current conditions. The needs for new research and development efforts in the areas of neutronics, fuel behavior, safety and waste performance are outlined.