TREQ - Fuel Rod Performance Code for Demanding PWR Plants

The search for improvements in nuclear fuel cycle economics results in increasing demands for fuel operation, including higher discharged burnup, and plant manoeuvrability. To achieve these objectives without a reduction of safety margins, new fuel designs and materials that enable enhanced performance capabilities have been developed like the dopped pellets products or the new cladding materials. Besides, fuel rod performance code are incorporating the experience gained in these irradiation conditions. In these regards, the European Fuel Group (EFG) has developed the TREQ code. TREQ is a fuel rod thermal-mechanical code used for the design and safety evaluation of fuel rods for PWR reactors. TREQ benefits from more than 30 year experience coming from the PAD code. The TREQ development was started by Westinghouse, BNFL and ENUSA, the EFG and it is primarily applied to the thermal-mechanical analysis of rods operating at steady-state or slow transient operations as well as to provide fuel inputs, for other codes used in the accident analyses and it has been validated over a wide range of irradiation conditions. Thus, TREQ Fuel Rod Performance Code meets customers' needs taking advantage of the performance of new products. The code comprises physical models which are developed on the basis of both theoretical considerations and experimental or in-pile data. The physical models of the code apply to Zircaloy-4 and ZIRLO cladding rods containing uranium and gadolinia doped pellets, fabricated according to ENUSA/Westinghouse specification. TREQ code has been licensed in Belgium up to a rod average burnup over 70 MWd/kgU for application on fuel rod design far PWR reactors. Besides, the code has been used to support several LOCA analyses in Belgium and other European countries. In Spain, TREQ was used in the licensing process of the high rod burnup programs. At present, EFG participates in several Research and Development (R&D) programs. The data at extended rod burnup, higher power and higher fuel densities, from theses programs will be incorporated to update models or reduce uncertainties. This paper presents the principal characteristics of the code, the main mechanical models and the strategy of development for the future.