Fission energy is a binding-energy argument, not just a “big nucleus breaks” story. The products sit closer to the binding-energy peak and the mass difference appears as kinetic energy and radiation.

Nuclear fission is the splitting of a heavy nucleus into two smaller daughter nuclei.

Fission may be spontaneous or induced by absorption of a neutron.

In neutron-induced fission of a fissile nucleus such as uranium-235, the compound nucleus becomes unstable and splits.

The products usually include two daughter nuclei, two or three fast neutrons, and gamma radiation.

Energy is released because the products have greater binding energy per nucleon than the original heavy nucleus, so mass is converted to energy.

Put the neutron-induced fission sequence in order.

Order

1

It splits into two daughter nuclei.

2

The compound nucleus becomes unstable.

3

A fissile heavy nucleus absorbs a slow neutron.

4

Two or three fast neutrons and gamma radiation are emitted.

5

Energy is released because products are more tightly bound per nucleon.

Describe how energy is released in spontaneous or neutron-induced fission.

Saying energy is released because the nucleus simply breaks apart.

Describe how energy is released in spontaneous or neutron-induced fission.

Choose

A chain reaction is about neutron economy. Not every neutron causes fission; some escape or are absorbed. Reactor control is about keeping the average continuation rate steady.

Each fission event releases two or three neutrons.

If those neutrons induce further fissions, a chain reaction can develop.

A controlled reactor keeps the average number of neutrons causing further fission close to one per fission.

If too many neutrons cause further fission, the reaction rate increases rapidly.

If too few neutrons cause further fission, the chain reaction dies away.

A critical mass is needed so enough neutrons are retained rather than escaping.

Classify the chain reaction state from neutron continuation.

Decision

Average continuation neutron count is less than one.

Average continuation neutron count is one.

Average continuation neutron count is greater than one.

Explain the role of chain reactions in nuclear fission.

Not distinguishing emitted neutrons from neutrons that actually induce more fissions.

Explain the role of chain reactions in nuclear fission.

Choose

A fission energy calculation is a mass-balance calculation. Include the neutron in the reactant mass for neutron-induced fission, and include all products on the product side.

The energy released in a fission reaction is calculated from the mass difference between reactants and products.

For released energy, Δm = total reactant mass - total product mass.

Use E = Δmc² if masses are in kilograms.

If Δm is in atomic mass units, use about 931.5 MeV per u.

A typical uranium-235 fission releases about 200 MeV.

Power is total energy released per unit time: P = number of fissions per second × energy per fission.

Assemble fission energy and power equations.

Formula

Target formula E = Δmc²

E

energy released per fission

J or MeV

Δm

mass defect: reactants minus products

kg or u

c

speed of light

m s^-1

R

fission rate

s^-1

P

power output

W

1Find mass defect from reactants and products.Δm = m_reactants - m_products

2Convert mass defect to energy.E = Δmc² or E(MeV)=Δm(u)×931.5

3Convert MeV to J if power is required.1 MeV = 1.60×10^-13 J

4Multiply by fission rate.P = R E

Build the formula

Calculate the energy released in a fission reaction and the power for a given fission rate.

Leaving energy in MeV when power requires joules.

Calculate the energy released in a fission reaction and the power for a given fission rate.

Choose

Fission waste questions are about properties and management. Name the property first: radioactive, heat-producing, penetrating radiation risk. Then match the management step: cooling, shielding, containment, long-term storage.

Fission products are often neutron-rich and radioactive.

They may emit alpha, beta, and gamma radiation and continue producing heat after removal from the reactor.

Spent fuel requires short-term cooling, often in cooling ponds.

Radiation shielding protects people and the environment from emitted radiation.

Long-term management may involve vitrification and deep geological storage.

The challenge is that some waste remains hazardous for very long times compared with human management timescales.

Choose the appropriate fission-waste management step.

Decision

Fresh spent fuel is producing decay heat.

Waste has cooled but remains hazardous for long times.

Material emits penetrating gamma radiation.

Describe properties of fission products and how radioactive waste is managed.

Only saying waste is buried without explaining cooling and shielding.

Describe properties of fission products and how radioactive waste is managed.

Choose

This summary card turns E.4 into one energy chain: nuclear binding energy becomes kinetic energy and radiation, then reactor systems control and transfer the energy while managing radiation hazards.

Fission splits a heavy nucleus into two daughter nuclei, releasing neutrons, gamma radiation, and energy.

Energy is released because products have greater binding energy per nucleon; calculations use E=Δmc² or 1 u ≈ 931.5 MeV.

A chain reaction occurs when fission neutrons induce further fissions; controlled reactors keep the rate steady.

Moderators slow fast neutrons, control rods absorb neutrons, coolant transfers thermal energy, heat exchangers produce steam, and shielding absorbs radiation.

Fission products are radioactive and require cooling, shielding, and long-term storage.

Match each E.4 cue to its fission or reactor role.

Match

Reasons

0/8

Summarize the E.4 fission model, including reactor control and waste.

Listing reactor parts without functions.

Summarize the E.4 fission model, including reactor control and waste.

Choose

IB Physics HL E.4 Fission Notes

Trace Fission energy release

Trace Chain reactions

Calculate Fission energy and power

Trace Fission products and waste

Retrieve the E.4 Fission Model