Lead Test Assemblies (LTA) Program Containing New Zirconium - Niobium Alloys Developed in Japan

摘要

The new century starts pushing an important challenge to all energetic sources. Nuclear energy is revealed as the most promising energy source in meeting the more than even severe social requirements as reducing CO_2 emissions, an effective utilization of natural resources the improvements of safety or the reduction of wastes. To achieve this goal, different action lines have been established to improve the efficiency of the light water reactors that are translated into operating practices that require the development of high performance fuels. Being aware of that situation, the Japanese PWR utilities, fuel vendors, cladding tube vendors, and academic intellects have joined its know-how and experience to develop a high performance family of alloys for fuel rod cladding application named J - Alloy?. This paper will present the different stages followed in the process of development and validation of the J - Alloy?. It will start from the selection of three Zr - Nb candidates to the current status, where the alloys are irradiated as a part of a Lead Test Assembly program in a Spanish NPP thanks to the well proved collaboration between the Japanese concerned companies and the Spanish Electric companies through ENUSA, who manages the Lead Test Assembly program. The paper would also describe the exhaustive out-of-pile testing. Based on the test results, safety-related criteria and also every single property required to assess its in - pile behavior, including subrogates of high - burnup conditions, were well confirmed. The irradiation strategy and the onsite characterization program carefully designed to minimize any impact in the normal operation of the NPP, to ensure a safe operation of the rods containing the new alloys and to provide information from the very beginning of the program; will be presented in the paper. Finally, the future plans to continue irradiation to high burn-up and the hot cell inspection plans to characterize the irradiated J - Alloy? cladding material will be presented.