Estimating operational releases of 14C and 3H of the GE-Hitachi BWRX-300 & Rolls-Royce SMR using full-core modeling in Serpent 2

The purpose of this project was to find estimates of the operational releases of 14C and 3H from new SMR technology that is being considered in Sweden, namely the Rolls-Royce SMR and the GE-Hitachi BWRX-300. To achieve this goal, models of the reactors of interest were made in the continuous-energy Monte-Carlo neutron and photon transport code Serpent, where the production of 14C and 3H could then be directly calculated. However, due to a lack of publicly available information relating to the Rolls-Royce SMR and the BWRX-300, a method was devised in which models of 2 large conventional reactors, a PWR (AP1000) and BWR (ABWR), were created in Serpent to complement the former models where necessary. The four models were then compared to find estimates of operational releases. The results showed that the operational release rate of 14C normalized to power output from the BWRX-300 was 533.2 GBq·GW(e)-1·a-1, approximately 3% higher than from the conventional BWR.For 3H the corresponding increase was 11% with a normalized release rate of 1045 GBq·GW(e)-1·a-1. For the Rolls-Royce SMR the 14C normalized operational release rate was 263.2 GBq·GW(e)-1·a-1, approximately 1.3% higher in the SMR compared to the large conventional PWR, and the 3H normalized operational release rate was 1031 GBq·GW(e)-1·a-1, at least an order of magnitude lower in the SMR compared to the large conventional PWR. This difference was due to the Rolls-Royce SMR not utilizing boron for reactivity control in contrast to most conventional PWRs. This made the Rolls-Royce SMR more comparable to the BWRs in the case of 3H operational releases, and compared to the large conventional BWR, the Rolls-Royce SMR had an approximately 1.7% higher operational release rate of 3H.