IB Physics SL E.4 Fission Questions

SLSL HLHL

Practise IB Physics SL E.4 by balancing fission equations, interpreting binding energy and evaluating chain-reaction evidence.

21 questions in this syllabus scope, with question parts counted together.

Exam points & syllabus

Exam points

Balance nucleon number in a supplied neutron-induced fission equation, including the absorbed neutron before counting the emitted neutrons.
Find total fission energy by converting the release per nucleus to joules and multiplying by the number of fuel nuclei in the stated mass.
Calculate released fission energy from total product binding energies minus total reactant binding energies, weighting each per-nucleon value by its own A.
Keep energy per reaction distinct from specific energy per kilogram, converting both reaction energy and the consumed fuel mass consistently.
Use efficiency to convert useful output to required nuclear energy, then divide the operating energy by specific energy to find fuel consumption.
For a steady chain in the supplied reactor model, subtract absorption and leakage so that one neutron per fission remains to induce the next fission.
In the assumed enrichment-dependent thermal model, link low natural U-235 abundance, greater fissility and increasing its fraction to sustaining the chain.
Explain moderation through neutron collisions that transfer energy to moderator atoms, reducing neutron speed or kinetic energy.
In a thermal reactor, connect neutron slowing to a greater probability of subsequent U-235 capture or fission.
Explain control rods through neutron absorption and consequent regulation of the fission rate, distinguishing them from the moderator.
For component comparisons, give the requested neutron-based similarities and differences, including collision or interaction explicitly where required.
Describe the heat exchanger as transferring thermal energy from the reactor coolant to water or steam.
Select water as a suitable moderator and interpret removal of moderation only within the assumed thermal-reactor model.
In the stated fusion–fission comparison, identify more straightforward waste disposal as the advantage without claiming zero radioactive waste.

Covered syllabus points

E.4.1—Fission energy release E.4.2—Chain reactions E.4.3—Nuclear power plant roles E.4.4—Fission products and waste

Exam points

Convert energy per fission from MeV to joules, find the number of fuel nuclei in the sample, then multiply to obtain maximum total energy.
For the supplied fission reaction, multiply each binding energy per nucleon by its own A and subtract total reactant binding energy from products.
Calculate specific fission energy by dividing the energy released per reaction in joules by the fuel mass per reaction in kilograms.
Convert useful output to required nuclear energy using efficiency, multiply by operating time and divide by specific energy to find consumed fuel mass.

[Maximum number: 3]

This question is in two parts. Part 1 is about energy resources. Part 2 is about thermal physics.
Part 1 Energy resources
Electricity can be generated using nuclear fission, by burning fossil fuels or using pump storage hydroelectric schemes.

Fission of one uranium-235 nucleus releases 203 MeV .

Determine the maximum amount of energy, in joule, released by 1.0 g of uranium-235 as a result of fission.

( 203 MeV is equivalent to) $3.25 \times 10^{-11} \mathrm{~J}$ ;
$6.02 \times 10^{23}$ nuclei have a mass of $235 \mathrm{~g} /$ evaluates number of nuclei;
( $2.56 \times 10^{21}$ nuclei produce) $8.32 \times 10^{10} \mathrm{~J} /$ multiplies two previous answers;

Exam points

For a steady chain reaction in the supplied model, leave one neutron per fission to induce the next fission after absorption and leakage.
Subtract control-rod absorption and wall losses from emitted neutrons; distinguish steady operation from a growing or extinguished chain.
In the assumed thermal reactor, link low natural U-235 abundance, greater fissility and an increased U-235 fraction to sustaining the chain.

[Maximum number: 3]

This question is about nuclear power production.

Outline the reason why fuel enrichment is necessary for the fuel used in a commercial nuclear reactor.

Exam points

State that the moderator slows neutrons or reduces their kinetic energy; distinguish this from absorbing neutrons or enriching fuel.
Explain moderation through collisions that transfer neutron energy to moderator atoms or molecules.
In a thermal reactor, link lower neutron energy to a greater probability of further fission or U-235 neutron capture.
Explain that control rods absorb neutrons and thereby regulate the fission rate; distinguish this from the moderator’s slowing action.
In a component comparison, supply the requested similarities and differences and refer explicitly to neutron interactions where required.
Describe a heat exchanger as transferring thermal energy from the reactor coolant to water or steam; naming heat alone does not explain its role.
Identify moderators and control rods together as the components maintaining the controlled chain reaction in the stated plant model.
Recognize water as a suitable moderator among the supplied material choices.
For the assumed thermal reactor, explain reduced energy production without moderation through the lower fission probability of fast neutrons.

[Maximum number: 3]

This question is about energy sources.

A small island is situated in the Arctic. The islanders require an electricity supply but have no fossil fuels on the island. It is suggested that wind generators should be used in combination with power stations using either oil or nuclear fuel.

A nuclear reactor requires both control rods and a moderator to operate. Outline, with reference to neutrons, one similarity and two differences in the function of each of these components.

[Maximum number: 1]

In nuclear power production, what is one advantage of a nuclear fusion reactor over a nuclear fission reactor?

The operating temperature of the fusion reactor is lower.

The nuclear reactants are more easily confined within the core of the fusion reactor.

The disposal of the nuclear waste products from the fusion reactor is more straightforward.

The nuclear fusion reaction is more easily sustained for long periods of time.

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