Chapter 5

The off gas from a boiling water nuclear power reactor contains a whole variety of radioactive trash, one of the most troublesome being Xe-133 (half life \(=5.2\) days). This off gas flows continuously through a large holdup tank in which its mean residence time is 30 days, and where we can assume that the contents are well mixed. Find the fraction of activity removed in the tank.

A specific enzyme acts as catalyst in the fermentation of reactant A. At a given enzyme concentration in the aqueous feed stream ( 25 liter/min) find the volume of plug flow reactor needed for \(95 \%\) conversion of reactant \(\mathrm{A}\left(C_{\mathrm{A} 0}=2 \mathrm{mol} / \text { liter }\right) .\) The kinetics of the fermentation at this enzyme concentration is given by $$\mathrm{A} \stackrel{\text { enzme }}{\longrightarrow} \mathrm{R}, \quad- r_{\mathrm{A}}=\frac{0.1 \mathrm{C}_{\mathrm{A}}}{1+0.5 \mathrm{C}_{\mathrm{A}}} \frac{\mathrm{mol}}{\text { liter } \cdot \mathrm{min}}$$

An aqueous feed containing \(\mathrm{A}(1 \text { mol/liter) enters a } 2\) -liter plug flow reactor and reacts away \(\left(2 \mathrm{A} \rightarrow \mathrm{R},-r_{\mathrm{A}}=0.05 \mathrm{C}_{\mathrm{A}}^{2} \text { mol/liter } \cdot \mathrm{s}\right) .\) Find the outlet concentration of \(A\) for a feed rate of 0.5 liter/min.