Ensuring negative coolant-void reactivity in CANDU Generation III+

It was established that the CANDU-NG model for Generation III+ had overall negative coolant-void reactivity in uniform voiding of all coolant channels. Reactivity is positive however, in the case of checkerboard voiding (when every second channel voids). Checkerboard voiding May be eliminated if channels from each geometric quadrant of the core are grouped to the same pair of inlet and outlet headers. Negative coolant-void reactivity and wide marketability remain thus ensured. Refuelling, structures, axial flux and exit burnup are not negatively affected. (authors)