Ionising radiations: precautions for industrial users.

  • Great Britain. Department of Employment and Productivity.
Date:
1969
Catalogue details

Licence: Public Domain Mark

Credit: Ionising radiations: precautions for industrial users. Source: Wellcome Collection.

    47/76 (page 45)
    properly equipped for the purpose of surveying and decontamin- ating any affected areas (e.g. Radiological Protection Service) 4 All practicable steps should be taken to prevent the dispersal of the radioactive material to the environment, for example, by covering with a damp cloth or by damping down the affected area with water, taking care to avoid any dispersal into drains 5 Acareful survey should be carried out to check that all surfaces which may have become contaminated are properly cleansed. APPARATUS PRODUCING IONISING RADIATIONS ADVENTITIOUSLY Apparatus in which electrons are accelerated and strike a target may often emit X-radiation. They are not designed to produce a useful beam of radiation, the electron stream is there just to produce a conducting current. The quantity of radiation emitted is determined by such factors as the operating voltage, the electron current and the thickness and nature of the wall material of the device. Examples of such apparatus are cathode-ray tubes, electronic valves—particu- larly high-voltage rectifying valves, e.g. those used in colour television equipment—and klystrons and magnetrons used in radar equipment. The Ionising Radiations (Sealed Sources) Regulations apply to such apparatus if the operating voltage exceeds 5 kV except in the case of television sets when the operating voltage must exceed 20 kV. The operating voltages of this type of apparatus are comparatively low and therefore the energy of the emitted X-radiation is such that thin metal covers over the areas concerned can provide the necessary shielding. Most apparatus of this type when in use is installed inside a cabinet which provides the necessary shielding and it is, therefore, only during manufacture, maintenance and repair that a hazard may exist. Where practicable, therefore, the components should be tested inside cabinets or enclosures fitted with interlocked access doors or panels. Often the amount of shielding necessary can be provided by a sheet of lead glass and this will ensure visibility. When components have to be provided with shielding, the shielding should be labelled to the effect that it must be kept in place when the component is energised. Because such apparatus may be associated with RF generators, the method of measuring the dose rate must be chosen with care because the RF can interfere with the monitor, which may then give a false reading. Fortunately monitors are available which are comparatively immune to RF interference. Although more time consuming, photographic film of the type used in personal dosemeters can be used for this purpose. This type of apparatus employs high voltages and the risk of electrical shock may well be the greatest hazard.