The Association for Science Education

K4.6 Radioactivity

Abstract

Radioactivity is not usually introduced into the curriculum before KS4 although pupils may well experience the idea in some form much earlier from their parents of the media. The topic has a huge potential for misconception and fear and these are explored from the perspectives of pupils and science teachers. Important ideas covered include radiation; nuclear transitions; strong nuclear force; half-life and background-radiation. Useful resources are suggested for exposing learners to appropriate models and explanations. Safety issues regarding the use of practical work in this topic are stressed.

This is one of 17 articles whose main aim is to support the processes of teaching/learning between the science education tutor and the trainee science teachers with a focus on “teachers’ knowledge and understanding”. During a primary or secondary BEd, PGCE or GTP we hope that those learning to become science teachers will be able to challenge their own understanding of science and scientific concepts. Unit K0 specifically explores general issues relating to all the knowledge units - to the learning of science.

Standards: This unit specifically addresses Q14 but, appropriately used can contribute to and provide evidence of competence for many others of the standards especially Q4,6,7,8,18, 22 and 25.

Keywords: Radioactivity, Radiation, Nuclear transitions, Half-life, Background-radiation.

Contents

1.0 Introduction
2.0 Conceptual Barriers to understanding ideas about radioactivity
3.0 Progression in children's ideas
4.0 Giving Practical experiences
5.0 Resources

1.0 Introduction

Radioactivity encompasses ideas about powerful (and natural) processes which can be hazardous in various ways. The energy comes from the direct transfer of some of the nuclear mass of atoms into energy. It is radioactivity (fission) that keeps the interior of the Earth hotter than we would otherwise expect - and (fusion) which generates the energy we receive from the sun.

1.1 Understanding Radioactivity
Radioactivity is a topic with a huge potential for misconceptions and fears, so it is perhaps a good thing that it does not appear before key stage 4 of the National Curriculum. It is included in the new specifications for GCSE from 2006. This short unit identifies some of the obstacles science tutors will need to be aware of as they support the next generation of secondary school science teachers.

  • There can be confusion between 'radiation' (eg alpha & beta particles and gamma radiation, emitted from radioactive sources), 'radioactivity' (the phenomenon) and 'radioactive substances' (the actual materials that emit radiation). Note
  • A very serious confusion between 'irradiation' (the act of having radiation impact on a substance, where it may be reflected, pass through, or be (partially) absorbed) and 'contamination' (where the actual material that is radioactive contaminates another material)
  • There is also considerable confusion of the various units used to quantify 'activity' and 'dose'.
  • Finally few people seem to be aware of the relatively high background radiation we are all exposed to all our lives, and the relatively small contribution human-induced radiation usually makes to this background dose. This should be a reassuring thought with nuclear power coming back in favour.

The resource Science Issues CD is a multimedia resource developed to give trainee teachers an understanding of the key ideas. It is written for adults, but is pitched at about GCSE standard, so will be of use for both the teachers in training and their KS4 pupils. 

1.2 Radioactivity and the National Curriculum
According to the 1999 KS4 National Curriculum Programme of Study Radioactivity (Science 4 para 6) students should be taught:

  • that radioactivity arises from the breakdown of an unstable nucleus
  • about some sources of the ionising radiation found in all environmentsthe characteristics of alpha and beta particles and of gamma radiation
  • the meaning of the term 'half-life'
  • the beneficial and harmful effects of ionising radiation on matter and living organisms
  • some uses of radioactivity, including radioactive dating of rocks.

And in the new specifications for GCSE from 2006, the QCA requires: (para 3.7) All specifications with the title GCSE Science should set the skills, knowledge and understanding, outlined in paragraph 3.6, entirely in the context of:

3.7 (iii) energy, electricity and radiations
c) radiations, including ionising radiations, can transfer energy

And: 
At least half of each specification with the title GCSE Additional Science should set the skills, knowledge and understanding, … in the context of the following content.
(iii) Physics 
b) Nuclear changes Nuclear changes within unstable atoms cause random emissions of particles. Nuclear changes also cause the emission of energy in the form of useful and dangerous radiation.

Clearly radioactivity has and will play an important part in the KS4 science curriculum, yet many science teachers will have had little exposure to the ideas in their undergraduate years (though they will have had background exposure to the real stuff, of course!). In this short section we will focus on the barriers faced not only by our pupils in school, but also by many of our science teachers in training. Even if they are do not teach the radioactivity topic in their teaching careers they all should have a clear understanding of the concepts above to enable them to avoid the confusions of paragraph 1.1.

2.0 Conceptual Barriers to understanding ideas about radioactivity

This section is summarized from a paper by Edward Prather (2005), which began by summarising previous research into students’ misunderstandings about radioactivity. Much of this work has been done by Millar, often in collaboration: 

As suggested in the introduction, this research showed that one of the common difficulties that students experience when trying to learn about radiation and radioactivity was an inability to differentiate properly between the concepts of irradiation and contamination. (p.345)

These students often stated that objects exposed to radiation would either become sources of radiation or have radioactive properties. Some of these students describe ionizing radiation as having the same properties as radioactive materials.(p.345)

Prather’s own research was undertaken on graduate students of geology who were trying to understand how radio-dating worked, and he targeted students' understanding of the role the atom plays in the radioactive decay process. (p.346)

Many of his students explained radioactive instability and decay in terms of electrostatic charge imbalance, and he devised this multiple-choice (plus reason) question to follow their ideas up in a larger sample (p.250):

Circle the statement(s) which characterize(s) what happens during radioactive decay.

  1. A valence electron is emitted from an atom.
  2. Some combination of protons and neutrons are emitted from the nucleus.
  3. An electron is emitted from the nucleus.
  4. A valence electron drops to a lower energy level, releasing energy (emits a photon).
  5. A proton or neutron drops to a lower energy level, releasing energy (emits a photon).

Other (specify):

Explain your reasoning for each statement you circled.

Only a quarter of his sample gave responses which only involved the nucleus (B, C and E). Even with these students they often thought that only coulombic forces were involved, and were unaware of the ‘strong’ nuclear force.

Note

In a further set of interviews and questions Prather found that his students thought that either the mass and/or volume of a radioactive material would decrease by half in the period of a half-life. Using such terms as radioactive ‘decay’ seemed to suggest that the atoms disappeared so even for those students who did have an understanding of radioactivity that involves the atom, they often also predict that half of the radioactive object will disappear after a half-life. (p.353)

Ref: http://www.nagt.org/nagt/jge/abstracts/sep05.html

3.0 Progression in children's ideas

It is likely that pupils will be taught radioactivity in one go as part of their GCSE course, so the idea of progression is not so significant here. However, it is important that students are familiar with concepts such as electrons; nucleus (protons and neutrons); (relative) atomic mass; atomic number and the Periodic Table. Children are likely to come to their GCSE session with some (popular) ideas about the dangers of radioactivity, and they will have some knowledge of the electronic structure of the atom. It is these two bits of prior knowledge that are likely to predispose the pupils to build up the misconceptions described above: 

  • a confusion of nuclear processes with the electrostatic events associated with the chemistry of the atom, 
  • a lack of appreciation of the background levels of radiation which surround us all
  • a fear of radiation and the thought that irradiated objects will become radioactive (the irradiation/contamination confusion) – although irradiated objects are often damaged and may become chemically changed.

4. Giving Practical experiences

Schools do keep radioactive sources for teachers to demonstrate to their pupils. There are strict regulations relating to the storage and use of these materials, and tutors and trainees should read the advice from CLEAPSS carefully. These are the relevant guides and latest date of revision:

R92 The Measurement of Radioactivity. 02/2001
L93 Managing Ionising Radiations and Radioactive Substances. (Explains the requirements of the latest Ionising Radiations Regulations. The important process of regular monitoring (now a legal requirement for every radioactive source) is explained in detail. Model local rules and risk assessments for the most commonly used radioactive sources are included.) 09/2008
PS46A Radiation Protection in School Science: Guidance for Employers - Information for LEAs. 09/2008
PS46B Radiation Protection in School Science: Guidance for Employers - Information for independent schools & colleges (including foundation & voluntary-aided schools). 09/2008

Student teachers should not attempt to handle radioactive sources in school with children unless under the guidance and tuition of the school’s radiation officer [Radiation Protection Adviser (RPA)], but if they can be trained to use sources safely during their ITE so much the better.

5. Resources

References:

  • Prather E. (2005) Students' Beliefs About the Role of Atoms in Radioactive Decay and Half-life Journal of Geoscience Education, v. 53, n. 4, September, 2005, p. 345-354.
  • Eijkelhof H. M. C, and Millar R., 1988, Reading about Chernobyl: the public understanding of radiation and radioactivity, School Science Review, v. 70, p. 35-41.
  • Millar R., Klaassen K. and Eijkelhof H., 1990, Teaching about radioactivity and ionizing radiation: an alternative.
  • Millar R., 1994, School students' understanding of key ideas radioactivity and ionizing radiation, Public Understanding of Science, v. 3, p. 53-30.

Web Resource:

Radioactivity teaching order: Don't worry about atoms to begin with

A common approach to teaching radioactivity is to start with the idea of the nucleus, then talk about alpha, beta and gamma, then move on to half-life and finish with a few words about uses and dangers.

This resource takes a different approach based on Radiation and Radioactivity, a scheme developed by Professor Robin Millar at the University of York.
 
Section Developed by:
Keith Ross, University of Gloucestershire with additional material from Alan Goodwin. January 2006

Published: 23 Jan 2006, Last Updated: 23 Sep 2008