4 (a) Radioactive tracers can be used when scanning a person's kidneys - Edexcel - GCSE Physics - Question 4 - 2022 - Paper 1

An isotope with a half-life of about 6 minutes is not suitable because it decays too quickly to provide a stable reading over the required 30-minute scan duration.

An isotope with a half-life of about 6 days is not suitable as it may remain in the body for too long, potentially causing harm to the kidneys or other organs due to prolonged radiation exposure.

1. Wear PPE (Personal Protective Equipment): This includes lead aprons, gloves, and goggles to protect against radiation exposure.
2. Distance Limiting Exposure: Increasing the distance from the radiation source when taking readings can significantly reduce the technician's exposure to radiation.

Pushing the control rods further into the reactor increases their absorption of neutrons. Control rods are made of materials that absorb neutrons, which reduces the number of neutrons available to propagate further fission reactions, effectively slowing down the nuclear chain reaction.

The average speed of the fast neutrons is given as $3.0 \times 10^7 \: m/s$ and the average speed of the slow neutrons is $4.0 \times 10^7 \: m/s$. To calculate the average speed of the slow neutrons as a percentage of the fast neutrons, we use the following formula:

$\text{Percentage} = \left( \frac{\text{speed of slow neutrons}}{\text{speed of fast neutrons}} \right) \times 100$

Substituting the values:

$\text{Percentage} = \left( \frac{4.0 \times 10^7}{3.0 \times 10^7} \right) \times 100 = \left( \frac{4}{3} \right) \times 100 \approx 133.33 \%$

The energy produced from the nuclear reaction is primarily in the form of heat. This heat is transferred to water in the reactor, turning it into steam. The steam is then used to drive turbines, which convert the thermal energy into mechanical energy, subsequently used to generate electricity.