Helium generation and its effect on BWR fuel rods

It was reported that a significant amount of helium is produced in the fuel pellets by ternary fission and alpha decay of transuranic elements. Some of the generated helium atoms are released from the fuel pellets to the gap and plenum region. The released helium atoms will improve the gap conductance and thus reduce fission gas release of the fuel rods. This phenomenon is especially prominent in high burnup BWR fuel rods. The purpose of this paper is to (1) present the helium release data from high burnup BWR rods, (2) predict the amount of helium generation by a lattice physics code and correlate the helium release with the generation amount, (3) evaluate the accuracy of the predicted helium generation by comparing with experimentally measured values, (4) evaluate the effect of helium release on fuel performance by using the formulae described in this paper. (author)