Radioactive decay and nuclear radiation

To control insect populations, sterilised male insects can be released into the wild.

They mate with females, who then produce no offspring, reducing the future population.

Sterilisation can be carried out using ionising radiation. The insects are placed in a canister about 10 cm across and then deliberately exposed to a known dose of ionising radiation.

Suggest why exposing an insect to ionising radiation may cause it to become infertile.

Both gamma rays and X-rays can be used to sterilise the insects.

Suggest why alpha radiation is not suitable for irradiating large numbers of insects.

Explain what is meant by a tracer.

A technetium‑99m tracer with an activity of 900 MBq is injected into a body. The half‑life of technetium‑99m is 6.01 hours.

Calculate the number of technetium‑99m nuclei initially present in the tracer.

Calculate the time in hours taken for the activity of the tracer to have fallen to 3.0% of its initial activity.

Deuterium is an isotope of hydrogen. A nucleus of deuterium has a proton and a neutron.

Describe the nature and range of the two forces acting between these two hadrons.

In beta-plus decay, a proton decays into three other particles.

Write a nuclear equation for this process.

A radiation detector is placed in front of a beta-emitting source. The count-rate is measured and recorded every 10 minutes. The results are shown below.

311 s^–1 309 s^–1 299 s^–1 307 s^–1 321 s^–1

What term can be used to describe the data shown?

A exponential

B linear

C random

D spontaneous

Your answer

A researcher is doing an experiment on a radioactive solution in a thin glass tube. The solution has two radioactive materials X and Y. The table below shows some data on these two materials.

The solution has the same number of nuclei of X and Y at the start.

State and explain which material has the greatest activity at the start.

State why it is dangerous for the researcher to handle the test tube with bare hands.

Carbon-14 (¹⁴₆C) is produced in the upper atmosphere of the Earth by collisions between nitrogen nuclei and fast-moving neutrons. The nuclear transformation equation below shows the formation of a single carbon-14 nucleus.

State the proton number of particle X.

Use the data below to determine the binding energy per nucleon of the¹⁴₆C nucleus. Write your answer to 3 significant figures.

• mass of neutron = 1.675 × 10^–27 kg

• mass of proton = 1.673 × 10^–27 kg

• mass of¹⁴₆C nucleus = 14.000 u

• 1 u = 1.66 × 10^–27 kg

binding energy per nucleon =........ J per nucleon

Fig. 20 illustrates a device used to determine the relative abundance of charged rubidium ions.

A uniform magnetic field is applied to an evacuated chamber. The direction of the magnetic field is perpendicular to the plane of the paper.

A beam of positive rubidium ions enters the chamber through a hole at H. The ions travel in a semi-circular path in the magnetic field. The ions are detected at point D.

The chemical composition of ancient rocks found on the Earth can be used to estimate the age of the Earth. Nuclei of rubidium-87 (⁸⁷₃₇Rb) decay spontaneously into nuclei of strontium-87 (⁸⁷₃₈Sr). The half-life of rubidium-87 is 49 billion years.

Name the two leptons emitted in the decay of a rubidium-87 nucleus.

The percentage of rubidium left in a sample of an ancient rock is 95%.

Estimate the age of the Earth in billion years.

age =........ billion years

The key on Fig. 21 shows whether a nucleus is stable, emits a beta-plus particle or emits a beta-minus particle to become stable.

For Z = 7, suggest in terms of N why an isotope may emit

a beta-minus particle

a beta-plus particle.

Inside a nuclear reactor, fission reactions are controlled and chain reactions are prevented. A typical fission reaction of the uranium-235 nucleus (²³⁵₉₂U) is illustrated below.

The neutron triggering the fission reaction moves slowly. The neutrons produced in the fission reaction move fast.

Describe what is meant by chain reaction.

Explain how chain reactions are prevented inside a nuclear reactor.

The energy released in each fission reaction is equivalent to a decrease in mass of 0.19 u. A fuel rod in a nuclear reactor contains 3.0% of uranium-235 by mass.

Estimate the total energy produced from 1.0 kg of fuel rod.

molar mass of uranium-235 = 0.235 kg mol^–1 1 u = 1.66 × 10^–27 kg

Complete the nuclear equations for these two processes.

Students want to carry out an investigation into gamma photon absorption using a source of

An isotope of polonium-213 (²¹³₈₄Po) first decays into an isotope of lead-209 (²⁰⁹₈₂Pb) and this lead isotope then decays into the stable isotope of bismuth (Bi).

Fig. 24 shows two arrows on a neutron number N against proton number Z chart to illustrate these two decays.

Complete the nuclear decay equations for

the polonium isotope

the lead isotope.

A pure sample of polonium-213 is being produced in a research laboratory. The half-life of²¹³₈₄Po is very small compared with the half-life of²⁰⁹₈₂Pb.

After a very short time, the ionising radiation detected from the sample is mainly from the beta-minus decay of the lead-209 nuclei.

Briefly describe and explain an experiment that can be carried out to confirm the beta-minus radiation emitted from the lead nuclei.

The activity of the sample of²⁰⁹₈₂Pb after 7.0 hours is 12 kBq. The half-life of²⁰⁹₈₂Pb is 3.3 hours.

Calculate the initial number of lead-209 nuclei in this sample.