The Health Protection Agency Radiation Protection Division Passive Survey Instrument

Aircraft crew and frequent flyers are exposed to elevated levels of cosmic radiation of galactic and solar origin and secondary radiation produced in the atmosphere, the aircraft structure and its contents. Following recommendations from the International Commission on Radiological Protection, the European Union (EU) introduced a revised Basic Safety Standards Directive which included exposure to natural sources of ionising radiation, including cosmic radiation, as occupational exposure. The revised Directive has been incorporated into laws and regulations in the EU member states. Where the assessment of the occupational exposure of aircraft crew is necessary, the preferred approach to monitoring is by the recording of staff flying times and calculated route doses. However there is a requirement to validate calculations periodically by measurement. The Radiation Protection Division of the HPA has developed a passive survey instrument to make these measurements. The instrument consists of a box containing 36 etched track detectors and 30 thermoluminescence dosemeters (TLDs), and 2 electronic personal dosemeters (EPDs) to record the time profile of the radiation field. Two boxes are prepared for each measurement, one as a background control. The measurement approach adopted is to determine separately the non-neutron component and the neutron component, which includes neutron-like dose equivalent contribution by high-energy protons. The 15% determination limit (that is the dose which can be determined with a 15% precision) is 100 µSv for the estimation of total ambient dose equivalent. This means that, in general, several return flights are required to make a measurement of acceptable precision.