Uses & Hazards of Radiation (OCR GCSE Physics A (Gateway)): Flashcards

Isotopes with short half-lives decay quickly, so they lose their radioactivity rapidly after the procedure, reducing long-term harm to the patient.

Radioactive waste with a long half-life is buried underground to prevent it from being released into the environment.

They remain radioactive for a very long time, so any contaminated material continues to emit radiation and requires careful shielding and storage for extended periods.

True.

A large amount means the total activity is very high, so a person could be exposed to a lot of radiation in a very short period of time.

A source with a short half-life has a higher activity, so it emits radiation faster and poses a greater short-term irradiation hazard than a source with a long half-life.

Francium-218 has a half-life of only 1 millisecond, while uranium-235 has a half-life of about 700 million years.

A medical tracer is a radioactive isotope used to track the movement of substances (such as blood) around the body, allowing an internal image of the body to be created.

Gamma rays are highly penetrating, so they can pass through the body and be detected outside the body. They are also less ionising than alpha or beta radiation, minimising harm to the patient.

False.

Tracers should have a short half-life (around a few hours) — long enough to complete the procedure but short enough to avoid long-term radiation exposure to the patient.

During external radiotherapy, beams of gamma rays are directed at the cancerous tumour, while surrounding healthy tissue is shielded.

Gamma radiation is the most penetrating type of radiation, so it can irradiate all sides of the instruments and pass through the packaging without the equipment needing to be unwrapped.

True.

Radiation can damage DNA and cause cancer, but it can also be used in radiotherapy to kill cancerous cells and treat tumours.

In internal radiotherapy, small pellets of radioactive material are inserted directly into the tumour, exposing it to radiation from inside — whereas in external radiotherapy, beams are directed at the tumour from outside the body.

The use of radiation in medicine carries risk, but the benefits can outweigh the risks if the condition would be more dangerous without treatment.

The isotope must be a gamma emitter so radiation can pass through the body, and it must have a short half-life (around a few hours) to reduce long-term radiation exposure to the patient.

Nuclear fission is the splitting of a large, unstable nucleus into two smaller daughter nuclei, releasing energy and two or three neutrons.

A neutron is absorbed by the uranium-235 nucleus, making uranium-236, which is very unstable and splits almost immediately, releasing energy and two or three neutrons.

False.

Energy transfers from nuclear potential energy to kinetic energy. The fission products (daughter nuclei and neutrons) move away at high speed.

In nuclear fission, the neutrons released by each fission reaction can trigger further fissions in a process called a chain reaction.

Control rods absorb excess neutrons inside the reactor, keeping the number of free neutrons constant so the chain reaction runs at a steady, controlled rate.

True.

Both uranium and plutonium undergo fission and are used as fuels in nuclear power stations.

In an uncontrolled chain reaction, the number of neutrons and fission reactions increases rapidly, releasing a huge amount of energy in a very short time — this is the principle behind a nuclear weapon.

During nuclear fission, the nucleus splits into two daughter nuclei and releases two or three neutrons, along with gamma rays.

Spontaneous fission is rare and releases energy very slowly, so it would not produce enough power at a useful rate. Reactors use induced fission with a chain reaction to generate a steady output of energy.

Nuclear fusion is the process in which two light nuclei join together to form a heavier nucleus, releasing energy.

Hydrogen nuclei both have positive charges and repel each other. Very high temperatures give the nuclei enough energy to overcome this repulsive force and fuse together.

True.

The energy from 1 kg of hydrogen undergoing fusion is equivalent to burning about 10 million kg of coal. Fusion releases far more energy per kilogram.

In most stars, hydrogen atoms are fused together to form helium, releasing large amounts of energy.

Fusion requires extremely high temperatures to give nuclei enough energy to overcome the repulsive force between them. Maintaining these conditions and producing more energy than the reactor uses has proven very difficult.

True.

The energy released during nuclear fusion comes from a very small amount of the particles' mass being converted into energy, as described by Einstein's equation E = m × c².

Deuterium and tritium, which are heavy isotopes of hydrogen, are used because they fuse more readily under the extreme conditions inside a fusion reactor.

ITER in France is currently the best performing fusion power station, almost giving out as much energy as it requires to power it.

During nuclear fusion, a small amount of the fusing particles' mass is converted directly into energy, as described by Einstein's equation E = m × c², where c is the speed of light.