What is ionising radiation?
Ionising radiation is a term collectively used to refer to types of energy in the electromagnetic spectrum, which can alter the electrical charge of an atom. The charge of an atom can be changed by the transfer of energy from the particles of radiation to the atoms, or alternatively, the direct displacement of electrons from the orbits of atoms.
A number of sources of radiation exist, both natural and artificial. Naturally occurring radionuclides can exist in the form of radioactive elements like uranium or polonium but can also be created artificially in reactors, particle accelerators, and X-ray tubes. Commonly encountered forms of ionising radiation include: alpha, beta, X-ray, gamma radiation and neutrons, in order from weakest to strongest in terms of ionising.
Alpha particles are composed of two protons and neutrons (helium atoms) stripped of their electrons, thus have a charge of 2+. As a result of their size, they readily react with matter and lose their charge. Thus, it is the weakest form of ionising radiation amongst the group, as they can be stopped by human skin.
Beta particles are fast-moving, medium energy electrons, ejected from nuclei of atoms. They can be positively or negatively charged but can travel 1-2cm in water or human flesh. They can be stopped by thin sheets of aluminium.
Gamma rays have no mass. They are an electromagnetic wave of high energy, much like the light we experience from the sun, expelled from the nucleus of an atom. They typically can travel large distances in air and require substantial mass in the form of concrete, lead or water to be stopped.
X-rays are similar in their properties to gamma radiation but where gamma rays are naturally occurring, X-rays are artificially created by accelerating electrons towards a target material, such as tungsten, gold, silver or rhodium. The impact of the electrons with the target material liberates X-rays from the which can be directed to perform specific measurements.
Neutrons are created as part of fission reactions (natural or artificial) and do not ionise substrates directly but instead through the transfer of energy to charged particles which themselves ionise substrates. The most effective way to stop these particles is to shield them with thick layers of concrete and water in substantial quantities.
What is ionising radiation used for?
For the purposes of this article, X-Ray radiation and its control will be explored as it is readily used in Industry. Other forms of radiation do have their uses, for example, cancer treatment or smoke detectors (α), cancer treatment, positron emission tomography (PET) scans and illumination devices (β) and sterilisation, gamma-knife surgery and nuclear medicine (γ).
Other than being used in medicine (to image bones) or airport security, X-ray instruments are used in Industry to measure coating thicknesses and perform elemental analysis of elements from Aluminium (13) to uranium (92). Examples include the electronics industry (PCB manufacture) with applications such as electroless nickel immersion gold (ENIG) or electroless nickel electroless palladium immersion gold (ENEPIG), general metal finishing with applications such as chrome, zinc, tin or many other versatile metallic compounds or automotive and aerospace industries measuring nanometre thick titanium zirconium coatings. Due to the ionising radiation generated by these instruments, strict controls have been placed on companies and individuals who use or wish to use such equipment.
Dangers of ionising radiation
Alpha (α) radiation is the weakest radiation source, but it can still be harmful to people if ingested. Beta (β) particles, gamma (γ) rays, and X-rays generally have enough energy to pass through cells and, therefore, not be absorbed like α particles are. In smaller doses, all types of radiation can lead to radiation poisoning with symptoms such as nausea and vomiting being some of the first signs exhibited. Beta, gamma, and X-rays can transfer substantial amounts of energy to cells as they pass through. In large radiation exposures, they can damage deoxyribonucleic acids (DNA) inside the cells. This leads to issues like abnormal cell growth (cancer) and burns to the skin or the underlying tissues. If the DNA damage occurs in the reproductive organs, there is a chance that the mutation is passed to the offspring, therefore the cancer is generational (not isolated to one individual). Pregnant mothers should also be highly vigilant as foetuses can absorb radiation through the mother, which can lead to developmental malformations and a reduction in IQ. The effects of the exposure are dependent on the type of radiation, the exposure duration, age, whether it is internal or external exposure and the dose received.
Control of ionising radiation and instruments that utilise it
Modern XRF analysers utilise a number of safety features (built into the instruments) to prevent exposure to ionising radiation, which include safety interlocks on doors, password protecting programs necessary to run the equipment, physical keys required to operate the instrument etc. These safety features ensure the instruments are used in accordance with the requirements of the Ionising Radiations Regulations 2017 (IRR17) in the UK, which is regulated (other than on nuclear sites) by the Health & Safety Executive (HSE). For the Republic of Ireland, the regulations are outlined in the Ionising Radiations Regulations 2019 (IRR19) document and is regulated by the Environmental Protection Agency (EPA). For Employers who utilise or who plan to utilise XRF Analysers, the key requirements can be summarised as:
- Appoint and seek advice from a suitable Radiation Protection Adviser (RPA), a specialist to help Employers with compliance to IRR17, providing advice on the safe use of XRF Analysers (IRR17 Regulation 14) including training in radiation protection (IRR17 Regulation 15).
- Obtain from HSE a Registration Certificate for the practice of using an X-Ray Generator (IRR17 Regulation 6).
- Develop a suitable Radiation Risk Assessment (IRR17 Regulation 8) for the use of XRF Analysers taking into account the installed control measures (IRR17 Regulation 9), which may include shielding, beam limitation/collimation, warning lights, interlocks, backscatter detectors and two-handed operation (for Handheld XRF Analysers) together with a suitable System of Work (which can include use of radiation protection training, procedures and for Handheld XRF Analysers only use of radiation monitoring instruments and operators wearing extremity personal dosimetry.
- When using Handheld XRF Analysers there will be a need to create a Designated Area (IRR17 Regulation 17) in the immediate area where the analyser is being used unless it is contained in a suitable interlocked enclosure.
- Where appropriate, develop Local Rules, which are the main working instructions intended to restrict any exposure in Designated Areas, together with the appointment of Radiation Protection Supervisors (RPS) to help the Employer ensure compliance to the Local Rules (IRR17 Regulation 18).
- Ensure that the XRF Analysers are subject to routine test, examination, and maintenance (IRR17 Regulation 11).
Helmut Fischer GmbH design all instruments with operators and public safety in mind. As such, all Helmut Fischer GmbH XRF instruments, both desktop and hand-held are manufactured following the rules and regulations set out in IRR17. Helmut Fischer GmbH is not an RPA but works closely with RPAs to ensure the correct information and the safe operating practices are given to all customers. For more details on how we can help, please contact us.