An example of burn up calculations in three dimensions for a CANDU core

Calculations with SYNTRONVOID have been made to simulate the operation of a 600 MWe CANDU reactor in some 2\ years. The results look reasonable as regards obtainable bum up and reactivity changes, whereas the power distribution is badly represented due to v the quarter core symmetry used,2) the lack of control system representation.

It is demonstrated that minor refuelling errors, i.e. untimely refuelling of a few scattered channels, do not lead to unacceptable power distributions. It is also demonstrated that care has to be taken in planning the refuelling strategy in order to avoid accumulation of fresh and almost fresh channels.

An island of 10 fresh channels, as occurred in the calculations knocked down the power to about 2/3. If it is felt that detailed 3D-calculations are desireable for guiding the operation it can be concluded that such calculations must be done on the full core.