Chapter 8 - The TRANSURANUS fuel performance code

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TRANSURANUS is a computer program for the thermal and mechanical analysis of fuel rods irradiated in nuclear reactors. It was originally developed at the Institute for Transuranium Elements (ITU), now Joint Research Centre (JRC) Karlsruhe, and is currently used worldwide by universities, research centers, technical safety organizations, safety authorities and industrial partners. The TRANSURANUS code consists of a clearly defined mechanical–mathematical framework into which physical models can easily be incorporated. The code is able to deal with a wide range of different irradiation situations, i.e., normal, off-normal and accidental conditions (e.g., design basis accidents, such as reactivity-initiated accidents or loss of coolant accidents), in thermal as well as fast spectrum reactors. The code covers both wide time and spatial scales (from milliseconds to years of irradiation, from the fuel grain to the fuel pin) that are necessary to accurately simulate various inter-connected intra-granular phenomena which are of high relevance at the engineering scale of the integral fuel pin. The code relies on a comprehensive built-in material data bank for oxide, mixed oxide, carbide and nitride fuels, zircaloy and steel claddings, and several different coolants (light water, liquid sodium, liquid potassium, helium, liquid lead and lead–bismuth). It can be applied in two different modes—in a deterministic orstatistical mode—allowing for assessing the impact of experimental and model uncertainties via incorporation of a Monte Carlo technique. The mathematical methods and solvers implemented in the code support its modification and extension, while providing excellent numerical stability. After details about the structure of the code and embedded models, the present Chapter provides examples of validation of TRANSURANUS against irradiation experiments and application to reactor safety analyses, showing the applicability of the code for simulating various kind of irradiations of fuel pins in both thermal water-cooled and fast liquid metal-cooled reactors. While confirming the code capabilities in predicting the fuel pin behaviour in water reactor conditions, which has been the main application of TRANSURANUS over the last three decades, the presented results are a good basis for the extension and validation of the code for MOX fuels in a fast reactor environment, becoming more and more important in the framework of Generation IV reactors development.