Nuclear fuel burnup ($B=E/M$)

Energy released per initial heavy-metal mass, commonly $\mathrm{MW}\mathrm{d}{\mathrm{t}}^{-1}$. For thermal energy production $E$ and burnup $B$, the corresponding initial fuel mass is $M=E/B$.

The burnup accumulated by a fuel batch when it is removed from its specified irradiation service. Its residence can span more than one operating cycle, so it is not generally the increment of burnup accumulated in a single cycle.