A fusion plant makes 500 MW of heat from the reaction ²H + ³H → ⁴He + n, which releases 17.59 MeV…

Step 1. The rate. One reaction gives $17.59 \times 1.602 \times 10^{-13}\ \text{J} = 2.818 \times 10^{-12}$ J. So the rate is $\dfrac{5.0 \times 10^{8}\ \text{W}}{2.818 \times 10^{-12}\ \text{J}} = 1.77 \times 10^{20}\ \text{s}^{-1}$.

Step 2. In a day. $1.77 \times 10^{20} \times 86\,400 = 1.53 \times 10^{25}$ reactions, which is $\dfrac{1.53 \times 10^{25}}{6.022 \times 10^{23}} = 25.45$ mol of each atom.

Step 3. The masses. Tritium: $25.45\ \text{mol} \times 3.016\ \text{g/mol} = 76.8$ g. Deuterium: $25.45\ \text{mol} \times 2.014\ \text{g/mol} = 51.3$ g.

Step 4. For one kilogram. One mole of reactions uses $5.030$ g of fuel and gives $\dfrac{2.818 \times 10^{-12}\ \text{J} \times 6.022 \times 10^{23}}{5.030 \times 10^{-3}\ \text{kg}} = 3.37 \times 10^{14}$ J for each kilogram.

Compare. One kilogram of uranium-235 gives $8.2 \times 10^{13}$ J, so the D-T mixture gives about $4$ times more. And a fusion plant of this power uses less than $100$ g of tritium in a day.