Neutron Radiation Measurements on Several International Flights

Abstract

The earth is continually exposed to cosmic radiation of both solar and galactic origin. High-energy particles interact with the constituents in the atmosphere producing secondary particles that create radiation fields at aircraft altitudes. These secondary particles consist mainly of photons, protons, neutrons, charged and uncharged pions, and muons. The neutron component dominates the hadron cascade at lower altitudes as a result of its longer mean free path. Since air transportation has become more available to a greater number of people, this has led to an increase in the number of persons exposed to ionizing radiation of cosmic origin. This concerns pilots and cabin crews as well as frequent flyers. A neutron component of cosmic radiation was measured using an LR 115/CR-39 track detector associated with a 10B converter foil. The measurement of the neutron dose is a good approximation of the total dose since neutrons carry about 50% of the total ambient dose equivalent at aircraft altitudes. Also, the results of the measurements were compared with the data obtained by EPCARD software simulation. The measured neutron dose rate had a span from 0.36 to 8.83 μSv h(-1) (dose enhancement due to high solar activity in the flight period).

Potential benefit of retrospective use of neutron monitors in improving ionising radiation exposure assessment on international flights: issues raised by neutron passive dosimeter measurements and EPCARD simulations during sudden changes in solar activity

“…Our findings confirm the strong influence of solar activity on both the increase or decrease of the neutron component of ambient dose equivalent we already reported earlier ( 3 ). The EPCARD software (and other similar programs) used by airlines to monitor radiation exposure run the risk of undermining actual doses by averaging solar potential over a month.…”

“…However, considering that the CERF field has a relatively higher thermal neutron component than the atmosphere at aircraft altitudes, Equation 1 may result in an overestimation of k. Another limitation of the dosimeter are large uncertainties in high energy neutron response (11), which may result in underestimation of neutron dose equivalent. Uncertainty of measurements and detector manipulation were determined as described in our earlier study (3).…”

“…Another limitation of the dosimeter are large uncertainties in high energy neutron response ( 11 ), which may result in underestimation of neutron dose equivalent. Uncertainty of measurements and detector manipulation were determined as described in our earlier study ( 3 ).…”

“…The average total dose rate for flights at lower latitudes and for short-haul flights is around 3 μSv/h. Flights at high latitudes result in higher dose than flights in the equatorial region due to the geomagnetic effect (expressed in the terms of magnetic rigidity) ( 3 , 4 ). Therefore, the radiation field at aircraft altitudes can be expressed as a function of three variables: flight altitude, solar modulation strength, and magnetic rigidity cut-off ( 5 , 6 ).…”

“…Our previous study ( 3 ) presented the measurements of neutron dose equivalent on board several international flights during the first half of the solar cycle 24, while the aim of this study was to measure neutron dose equivalent on several international flights in its second half (from maximum to minimum) and to clearly discern the influence of solar activity, flight altitude, and flight route.…”