Show — 4 marks
A hospital radiology department uses CT scanners to diagnose patient conditions. The annual background radiation dose received by staff working in the department is 3.5 mSv, compared to the UK average of 2.7 mSv. The department manager is concerned about the increased risk to staff and is considering additional shielding measures.
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(a) Show that the additional annual dose received by the radiology staff, above the UK average background radiation, is 0.8 mSv.
[1 mark]
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(b) Explain why background radiation cannot be completely eliminated for workers in a hospital radiology department, even with additional shielding.
[2 marks]
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(c) The hospital introduces a lead-lined apron that reduces the additional dose by 60%. Evaluate whether this shielding measure alone is sufficient to reduce the radiology staff's dose to the UK average background radiation level. Show your working.
[1 mark]
Show mark scheme
- (a) Subtraction: 3.5 - 2.7 = 0.8 mSv (or clear working shown)
- (b) Background radiation comes from natural sources (cosmic rays/terrestrial sources) that cannot be completely blocked/shielded
- (b) Shielding only protects against occupational radiation exposure from equipment/procedures, not natural background sources
- (c) 0.8 × 0.4 = 0.32 mSv remaining additional dose; 2.7 + 0.32 = 3.02 mSv (still above 2.7 mSv UK average) / No, the dose would still be above average / No, only 60% reduction is insufficient to reach the average background radiation level
Describe — 4 marks
A hospital physicist is reviewing radiation safety protocols for staff working in the radiology department. The department receives regular reports on annual radiation dose exposure, which includes both occupational exposure and background radiation received by all workers.
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(a) Describe what is meant by background radiation.
[1 mark]
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(b) Describe two natural sources of background radiation that contribute to the dose received by the hospital staff.
[2 marks]
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(c) Describe how background radiation poses a risk to human health, even though exposure levels are generally low.
[1 mark]
Show mark scheme
- (a) Ionising radiation from natural/environmental sources (or equivalent such as 'always present in the environment' or 'low-level radiation constantly around us')
- (b) Cosmic rays (or radiation from space/sun)
- (b) Radon gas (or radioactive gas from rocks/soil/ground)
- (c) Continuous/prolonged exposure increases cumulative dose / risk of cell damage / mutations / cancer increases with total dose received over time
Define — 2 marks
A nuclear scientist is working in a laboratory where radioactive materials are stored. During routine maintenance, a small amount of radioactive dust escapes from a sealed container and settles on the scientist's protective clothing. Later, the scientist enters a controlled radiation facility where they are exposed to gamma rays from a medical imaging source. The laboratory manager needs to assess the different types of radiation exposure and contamination risks.
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(a) Define the term irradiation.
[1 mark]
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(b) Define the term contamination in the context of radioactive materials.
[1 mark]
Show mark scheme
- (a) Exposure to radiation (from an external source) / being exposed to ionising radiation
- (b) Radioactive material present on or inside an object/body / presence of unwanted radioactive atoms on a surface or within a material
GCSE Perfect