The evaluation and use of a portable TEPC system for measuring in-flight exposure to cosmic radiation.

A recent EC directive has called for all member states to introduce legislation covering the assessment and restriction of air crew exposure to cosmic radiation. In the UK the Civil Aviation Authority, in conjunction with the Department of the Environment. Transport and the Regions issued guidelines suggesting the use of a predictive code such as CARI for this purpose. In order to validate the use of calculated route doses, an extensive programme of measurements is being carried out on long haul routes in conjunction with Virgin Atlantic Airways, using a prototype HAWK TEPC developed by Far West Technology. This programme began in January 2000 and by the end of February 2001 had resulted in the accumulation of data from 74 flights. In this paper the instrument design is discussed, together with the calibration programme. An overview of the in-flight results is also presented, including comparisons between measurements and calculations, which indicates that CARI under-predicts the route doses by approximately 20%.

Potential doses to passengers and crew of supersonic transports.

Data from a tissue equivalent proportional counter that was flown at altitudes ranging from 60,000 feet to 70,000 feet were used to estimate radiation quality factors at different latitudes. For high LET radiation, Q values of 11 to 14 were calculated for latitude 18 degrees north to 59 degrees north. Dose equivalent rates ranging from 5.2 microSv hr(-1) to 27 microSv hr(-1) were measured. These dose equivalent rates are about twice that computed using a computer code called CARI-4Q. The dose equivalent received during a flight from Los Angeles to Tokyo was computed using CARI-4Q and the result doubled, based on the TEPC to CARI-4Q ratio. Members of the general public, including frequent flyers, would not exceed dose limits recommended by the ICRP. Air crew would not exceed the limits for occupationally exposed persons. However, pregnant air crew, based on a 2 mSv limit to concepti, would exceed the limit after 150 hours flying time.