Monitoring Cosmic Radiation Risk: Comparisons between Observations and Predictive Codes for Naval Aviation

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Monitoring Cosmic Radiation Risk: Comparisons between Observations
and Predictive Codes for Naval Aviation

U.S.N.A. --- Trident Scholar project report; no. 377 (2009)

Midshipman 1/c Jacob P. Dobisesky


Utilizing a unique, Far West Technology Tissue Equivalent Proportional Counter
(TEPC)-based system called the HAWK, the atmospheric radiation exposures of commercial air
travelers and naval personnel were compared to the quantity predicted by commercially available radiation codes. The HAWK simulates a two micron-diameter somatic cell, measuring the lineal energy, absorbed dose, and dose equivalent based on the International Commission on
Radiological Protection (ICRP)-60 recommendations. Prior to the flights, the HAWK detector
response was modeled with MCNP5 and GEANT4. Later, the data were analyzed both to
produce a dose rate as well as a total dose for the flight’s duration. Over 40 hours of flight data was obtained on commercial aircraft in addition to several experiments on military and private aircraft. Flights were conducted across the continental United States, from Massachusetts to California. The military flights were conducted on an EA-6B Prowler from the Navy’s VX-23 Squadron in Patuxent River, Maryland. Commercial aircraft altitudes reached a ceiling of approximately 38,000 feet while typical military operations were around 25,000 feet. During the flight, data including dose and dose equivalent rates were collected along with corresponding GPS data such as geodetic latitude, longitude, and altitude.
The GPS data were then utilized as inputs for several commercially available radiation codes for
assessing atmospheric radiation risk. These codes included CARI-6, developed by the US
Federal Aviation Administration (FAA), EPCARD developed by Germany’s GSF – National
Research Center for Environment and Health, and EXPACS, developed by Japan’s Atomic
Energy Agency. Analysis of the code outputs yielded several conclusions. First, EXPACS
predicts radiation doses very close to CARI-6 and could be developed into a more user-friendly
and adaptable code for the Navy given its EXCEL-based platform and multiple input variables.
Second, radiation dose predictions on the EA-6B Prowler and commercial aircraft at altitudes
below 15,000 feet begin to break down and the codes no longer accurately predict radiation. In
addition, pilots, aircrew, and frequent fliers may exceed the one milli-Sievert per year limit for
the general public depending on their destinations and duration at high altitudes. Finally, these
commercial codes provide a conservative, accurate method to predict and estimate the radiation
risk of naval pilots and aircrew.