P6.2

Question 1

What is irradiation

Answer 1

Irradiation happens when there is a radioactive material outside your body, but the radiation could travel into your body.

Question 2

What is contamination

Answer 2

Contamination happens when you take radioactive material into your body or if it is on your skin.

Question 3

How is gamma radiation used to detect cancer

Answer 3

• Radioactive materials are used as tracers for detecting cancer.
• Tracers are bind onto proteins that specific human organs absorb and get injected into the patient’s body.
• Using a Gamma camera we can detect where the tracer has concentrated.
• Therefore, gamma rays are emitted from outside the body focused on that area (Gamma Knife).

Question 4

Hazards of radioactive tracers

Answer 4

The shorter the tracer’s half life the less ionisation takes place in our body.
The smaller the amount of the tracer used the faster it will exit our body.

Question 5

Apart from choosing an appropriate half-life, suggest one other action a radiographer could take to reduce the risk of the patient contracting cancer

Answer 5

• could take into consideration the AMOUNT of the tracer needed ti be injected

Question 6

Why do doctors choose tracers that emit gamma and not alpha or beta

Answer 6

Gamma is the least ionising

Question 7

Explain why the risk of cancer is usually higher when you are contaminated than when you are irritated

Answer 7

When we are contaminated the radioactive source is inside our body therefore ionisation takes place.

α - radiation cannot penetrate our skin but when ingested it is dangerous as it is the most ionising / damaging the DNA.

Question 8

Compare the use of tracers and gamma knives

Answer 8

• Both use isotopes that emit gamma rays.
• The gamma rays travel through the body.
• With a tracer the material is inside the body, but with a gamma knife it is outside.
• The aim of a tracer is not to damage cells, but the aim of a gamma knife is to destroy them.

Question 9

Why are some nuclei unstable

Answer 9

They have an imbalance between the number of protons to neutrons resulting in too much energyv

Question 10

Define nuclear fission

Answer 10

The splitting of a nucleus into 2 smaller nuclei, with the release of energy and neutrons

Question 11

How is fission induced in a nuclear reactor

Answer 11

when a Uranium-235 nucleus is hit with a neutron.

Question 12

What does the splitting of a Nucleus produce

Answer 12

The two smaller nuclei (daughter nuclei) which are themselves unstable, and become stable by undergoing radioactive decay

Question 13

Properties of nuclear waste

Answer 13

Very dangerous
Very long half-life
Must be buried and guarded

Question 14

Define a chain reaction

Answer 14

Process in which neutrons released during a fission event, go on to produce further fission events.

Question 15

What is a controlled fission event

Answer 15

Only one neutron from each fission event is able to produce another fission event.Control rods in power plants absorb surplus neutrons and energy is generated at a steady rate.

Question 16

How are controlled chain reactions controlled

Answer 16

WITH CONTROL RODS

Control rods in power plants absorb surplus neutrons and energy is generated at a steady rate.

Question 17

What is an uncontrolled fission reaction

Answer 17

Every neutron from each fission event goes on to produce further fission events.Energy released at an exponential rate.

Question 18

What is a fissionable isotope

Answer 18

are those that can be made unstable.(BUT THEY THEMSELVES ARE STABLE)

Question 19

Example of a fissionable element

Answer 19

U-235 = fissionable (∵ U-236 is unstable)

Question 20

Name a fissionable material and describe what happens when it undergoes fission

Answer 20

U-235 is a fissionable isotope of Uranium

A neutron is absorbed by a nucleus of U-235, transforming it into U-236, which is unstable and breaks apart into two smaller daughter nuclei.

Question 21

Explain why there must be a material that absorbs neutrons un a nuclear reactions

Answer 21

Without a material to absorb neutrons, an uncontrolled chain reaction occurs.

Energy is released at an increasing, exponential rate.

This is dangerous and will lead to an explosion.

Question 22

Define nuclear fusion

Answer 22

The joining of two small nuclei to form a larger nucleus, releasing energy

Question 23

Where does nuclear fusion occur

Answer 23

Occurs in stars when 2 very light nuclei (isotopes of Hydrogen) are forced together at high speeds, to form heavier Helium nucleus.

Question 24

Advantages of nuclear fusion

Answer 24

• No radioactive waste produced.(unlike fission… very long half-life radioactive waste)
• The fuel required for fusion is readily available in water.(unlike fission… Uranium is non-renewable)
• Nuclear fusion produces a lot more energy than fission.(four times as much than fission)

Question 25

Nuclear fusion disadvantages

Answer 25

Building fusion reactors is very difficult/not viable.

Currently, much more heat energy is required to make nuclei overcome their repulsive forces and fusethan the energy actually released from fusion - not worth it

Question 26

Why are Starts able to carry out fusion

Answer 26

as they have very high temperatures and very high pressures.

Question 27

What’s the weird thing about fusion in starts

Answer 27

The helium nucleus (the one we end with) has less mass than the sum of the masses of the hydrogen nuclei ( the ones we start with)

Question 28

Why does The helium nucleus have less mass than the sum of the masses of the hydrogen nuclei.
Ie. Where does the missing mass go?

Answer 28

The “missing mass” is transformed into energy,by Einstein’s mass-energy equivalence equation.

Question 29

The tiny difference in mass results in a …

Answer 29

Large release of energy

Question 30

Einstein’s Mass-Energy Equivalence Equation

Answer 30