LAGER – Laser Ablation of Gadolinium Evolution Radial

The aim of the LAGER project is to obtain detailed data on the Gd distribution at selected axial positions and to make the data available for code validation. In addition, source term data will be determined and the modelling of burn-up calculations will be further developed. The experimentally determined data are needed to further develop accurate models for Gd burn-up and to enable prediction of reactivity and energy distribution within the fuel assemblies. This data is of great value to BGZ, as the rod under analysis covers a further part of the inventory. In the course of the German nuclear moratorium in 2011 and the subsequent amendment of the Atomic Energy Act, BWR fuel assemblies with very low burn-up were also placed in dry interim storage in Germany.

The fuel rod investigated in LAGER is an intact BWR rod from a 10×10 fuel assembly with 3.66 weight per cent 235U enrichment and 4 per cent initial Gd content. The average rod burn-up is approximately 9 GWd/tHM with axial values between 6 and 11 GWd/tHM. The irradiation history is typical of BWR irradiation for fresh fuel without a history of a control rod, but with a neighbouring part-length fuel rod. The latter leads to an axial power divergence of 5 to 15 per cent. The operator Vattenfall will provide the detailed operating history for the project.

The LAGER project will be carried out in Studsvik’s hot cell facilities, using both industry-standard post-irradiation methods and unique analytical techniques to quantify local pellet properties. Axial positions for local measurements are selected on the basis of modelling and nondestructive tests. The LAGER project partners are actively involved in the selection of the axial samples and the type of experimental implementation and decisions are made by consensus.