Performance of Accident Tolerant Fuel Using Iron-Based Alloy as Cladding

In the framework of the Coordinated Research Project (CRP) concerning to Accident Tolerant Fuels (ACTOF) from the International Atomic Energy Agency (IAEA), USP/IPEN work-plan addressed the neutronic and fuel performance evaluation of iron-based alloys to replace zirconium-based alloys in PWR under steady-state irradiation and LOCA scenario. The neutronic assessment considered different kinds of iron-based alloys and showed the well-known penalties due to neutron absorption, specifically due to presence of Fe, Cr, and Ni in the studied iron-based alloys. The neutronic evaluation considered also some approaches which can be applied to overcome such penalty at beginning of cycle: increase of uranium enrichment level; change in the moderation ratio (water channel); reduction of the cladding thickness; increase of fuel pellet diameter; and the combination of these parameters. The fuel performance evaluation was carried out using modified versions of the well-known fuel performance codes FRAPCON and FRAPTRAN modified in order to introduce the properties of stainless steel 348 as cladding material. The obtained results under steady state irradiation and LOCA scenario were compared to those of the original code versions for Zircaloy-4 using a data base available in the open literature. A proposed benchmark in the framework of the ACTOF program was also used to compare the fuel performance of stainless steel 348, FeCrAl and Zircaloy-4 under the same fuel rod design and power history. Such parameters as fuel centerline temperature, gap thickness, and fission gas release were evaluated and compared. The results showed that the higher thermal expansion experienced by iron-base alloys under irradiation compared to zirconium-based alloys plays an important role in the global fuel performance. (author)