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Date May 2011 Marks available 3 Reference code 11M.2.SL.TZ1.4
Level Standard level Paper Paper 2 Time zone Time zone 1
Command term Explain Question number 4 Adapted from N/A

Question

This question is in two parts. Part 1 is about a nuclear reactor. Part 2 is about simple harmonic
oscillations.

Part 1 Nuclear reactor

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.

[4]
b.

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

[3]
c.

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.

 

[3]
d.

Markscheme

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

b.

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;

c.

(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;

d.

Examiners report

[N/A]
b.
[N/A]
c.
[N/A]
d.

Syllabus sections

Core » Topic 8: Energy production » 8.1 – Energy sources
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