Hazards & Uses of Radioactive Emissions & of Background Radiation Practice Questions

Background radiation is present around us all of the time. Some sources of background radiation are natural and some are man-made.

A doctor wants to find out whether a patient's kidneys are removing waste from the blood correctly.

A liquid containing a radioactive isotope that emits gamma radiation is injected into the patient's blood.

Workers at a hospital wear badges that measure the radiation dose they receive.

In one year:

• worker A received a dose of $0.0045$ Sv
• worker B received a dose of $3.6$ mSv

The radiation dose a person receives from background radiation depends on where they live and on the job they do.

Table 1 gives the average annual radiation dose received by three people.

Person	Average annual radiation dose in mSv
Office worker living in London	2.2
Person living in a granite area of Cornwall	7.8
Long-haul airline pilot	4.6

A radiographer lives and works in an area of Cornwall where the average annual dose from background radiation is $6.9$ mSv.

The radiographer works for $225$ days each year. On each working day she receives an additional dose of $0.0080$ mSv from the X-ray equipment she uses.

Table 1 gives the half-life of four radioactive isotopes found in the waste from a nuclear power station.

Isotope	Half-life in years
Krypton-85	$1.1 \times 10^{1}$
Caesium-137	$3.0 \times 10^{1}$
Plutonium-239	$2.4 \times 10^{4}$
Iodine-129	$1.6 \times 10^{7}$

All four isotopes emit the same type of nuclear radiation.

A sample of krypton-85 and a sample of iodine-129 each contain the same number of radioactive atoms.

Nuclear radiation can be used in hospitals to control or destroy unwanted tissue, such as a cancerous tumour.

A 55-year-old patient has symptoms that may be caused by a tumour in one lung.

Table 1 gives data about three different medical procedures the patient could have.

Procedure	Radiation dose in mSv	Extra lifetime risk of developing a fatal cancer	Chance of correctly locating a small tumour
Chest X-ray	0.020	1 in 1 000 000	25%
CT scan of the chest	7.0	1 in 3000	75%
PET-CT scan	25	1 in 800	95%

The average annual dose from background radiation in the UK is $2.7$ mSv.

If a lung tumour is found early, the patient's chance of surviving for five years rises from $15\%$ to $60\%$.