ASN Report 2018

1 —  Industrial, research and veterinary uses of ionising radiation 1.1  ̶  Uses of sealed radioactive sources Sealed radioactive sources are defined as sources whose structure or packaging, in normal use, prevents any dispersion of radioactive substances into the surrounding environment. Their main uses are presented below. 1.1.1  –  Verification of physical parameters The operating principle of these physical parameter verification devices is the attenuation of the signal emitted: the difference between the emitted signal and the received signal can be used to assess the desired information. The most commonly used radionuclides are carbon-14, cobalt-60, krypton-85, caesium-137, prometheum-147 and americium-241. The source activity ranges from a few kilobecquerels (kBq) to a few gigabecquerels (GBq). These sources are used for the following purposes: ∙ ∙ Atmospheric dust measurement: the air is permanently filtered through a tape placed between the source and detector, running at a controlled speed. The intensity of radiation received by the detector depends on the amount of dust on the filter, which enables this amount to be determined. The most frequently used sources are carbon-14 (with an activity of 3.5 megabecquerels - MBq) or prometheum-147 (with an activity of 9 MBq). These measurements are used for air quality monitoring by verifying the dust content of discharges from plants. ∙ ∙ Paper weight measurement: a beam of beta radiation passes through the paper and hits a detector situated opposite. The signal attenuation on this detector indicates the density of the paper, and therefore its weight per unit area. The sources used are generally krypton-85 or prometheum-147, with activities of 3 GBq at the most. ∙ ∙ Liquid level measurement: a gamma radiation beam passes through the container holding the liquid. It is received by a detector positioned opposite. The signal attenuation measured on this detector indicates the filling level of the container and automatically triggers certain operations (stop/ continue filling, alarm, etc.). The radionuclides used depend on the characteristics of the container and the content. The sources generally used are americium-241 (with an activity of 1.7 GBq) or caesium-137 – baryum-137m (with an activity of 37 MBq). ∙ ∙ Density measurement and weighing: the principle is the same as for the above two measurements. The sources used are generally americium-241 (with an activity of 2 GBq), caesium-137 – baryum-137m (with an activity of 100 MBq) or cobalt-60 (with an activity of 30 GBq); ∙ ∙ Soil density and humidity measurement (gammadensimetry), particularly in agriculture and public works. These devices function with a source of caesium-137 and a pair of americium‑beryllium sources. CHAPTER 08 I ndustrial and research sectors have been using sources of ionising radiation in a wide range of applications and locations for many years now. The purpose of the radiation protection regulations is to ensure that the safety of workers, the public and the environment is achieved. This protection involves more specifically ensuring proper management of the sources, which are often portable and used on worksites, and monitoring the conditions of their possession, use and disposal, from fabrication through to end-of-life. It also involves monitoring the main stakeholders, that is to say the source manufacturers and suppliers, and enhancing their accountability. The ongoing updating of the regulatory framework for nuclear activities established by the Public Health Code and the Labour Code is leading to a tightening of the principle of justification, consideration of natural radionuclides, the implementation of a more graded approach in the administrative systems and measures to protect the sources against malicious acts. These developments will start to bring substantial changes in the oversight of industrial, research and veterinary activities as of January 2019, which will continue over the years to come. The radiation sources used are either radionuclides - essentially artificial - in sealed or unsealed sources, or electrical devices generating ionising radiation. The practices/applications presented in this chapter concern the manufacture and distribution of all sources, the industrial, research and veterinary uses (medical activities are presented in chapter 7) and activities not regulated under the Basic Nuclear Installations (BNI) System (these are presented in chapters 10, 11 and 12). Sources of ionising radiation and their industrial, veterinary and research applications 232  ASN report on the state of nuclear safety and radiation protection in France in 2018