Extension and preliminary validation of the Polaris lattice physics code for CANDU analysis

Polaris is a 2D lattice physics code available for the study of light water reactors (LWRs). It includes a method of characteristics (MoC) transport solver and the embedded self-shielding method (ESSM). Its advantages include a simplified user input structure, quick performance, and integration into the SCALE package, utilizing its nuclear data libraries, along with other codes such as the ORIGEN depletion code and the Sampler stochastic uncertainty analysis sequence. This work extends the Polaris code to support CANDU lattice transport calculations and performs some preliminary verification and validation, comparing the code to NEWT and KENO, along with to benchmark experimental data. Heavy-water specific self-shielding factors were also compared to those distributed with SCALE. In general, some differences are observed, but these are generally comparable to other code-to-code differences and smaller than nuclear data uncertainties. The generation of self-shielding factors has a noticeable effect, particularly on the benchmark coolant void reactivity calculation. Heavy-water specific self-shielding factors, while not required, can potentially improve the accuracy of ESSM-based calculations, but the choice of parameters can significantly affect the results. Overall, the Polaris transport and self-shielding calculations should be suitable for CANDU analysis.