The reactor produces 24 MW of power. The efficiency of the reactor is 32 %. In the fission of one uranium-235 nucleus 3.2×10⁻¹¹J of energy is released.

Determine the mass of uranium-235 that undergoes fission in one year in this reactor.

Explain what would happen if the moderator of this reactor were to be removed.

During its normal operation, the following set of reactions takes place in the reactor.

${}_0^1{\rm{n}} + {}_{92}^{238}{\rm{U}} \to {}_{92}^{239}{\rm{U}}$           (I)

${}_{92}^{239}{\rm{U}} \to {}_{93}^{239}{\rm{Np}} + {}_{ - 1}^0e + \bar v$           (II)

${}_{93}^{239}{\rm{Np}} \to {}_{94}^{239}{\rm{Pu}} + {}_{ - 1}^0e + \bar v$           (III)

(i) State the name of the process represented by reaction (II).

(ii) Comment on the international implications of the product of these reactions.

power produced $\left( {\frac{{24}}{{0.32}}} \right)$=75MW;
energy produced in a year (75×10⁶×365×24×60×60=)2.37×10¹⁵J;
number of reactions required in one year $\left( {\frac{{2.37 \times {{10}^{15}}}}{{3.2 \times {{10}^{ - 11}}}}} \right) = 7.39 \times {10^{25}}$;
mass used (7.39×10²⁵×235×1.66×10⁻²⁷)≈29kg;

or

mass used $\left( {\frac{{7.39 \times {{10}^{25}}}}{{6.02 \times {{10}^{23}}}} \times 235 \times {{10}^{ - 3}}} \right) = 29{\rm{kg}}$;

the neutrons would not be slowed down;
therefore they would not be/have less chance of being captured/induce fission;
so (much) less/no power would be produced;

(i) beta decay;

(ii) the reactions end up producing plutonium (from uranium 238);
(this isotope of) plutonium may be used to manufacture nuclear weapons / can be used as fuel in other reactors / plutonium is extremely toxic;

or

the products of the reactions are radioactive for long periods of time / OWTTE;
therefore posing storage/safety problems;