Calculating the Bowing-Related Reactivity Worth Using PERSENT

A new bowing worth reactivity capability has been added to PERSENT based on the first-order perturbation theory. To handle the heterogeneous aspects of geometric bowing, a heterogeneous operator was introduced into the first-order perturbation equation in PERSENT. The heterogeneous operator assumes two spatial regions within each mesh consisting of the bypass gap region around the duct and a homogenized region internal to the duct. The methodology retains the spatial polynomial basis of DIF3D-VARIANT and uses Gaussian integration to build new spatial matrices associated with the two-region model. The new PERSENT capability was used to solve manufactured problems compared against MCNP solutions and models of two experiments performed in ZPPR-17A. The PERSENT results were found to be good and as expected in the manufactured problems, and acceptable accuracy was achieved for the ZPPR-17A experiments.