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Data Library and Four-Parameter Empirical Formula for the Response Functions for Gamma-Ray Skyshine Dose

Hideo Hirayama, Yoshiko Harima, Yukio Sakamoto, Naohiro Kurosawa, Makoto Nemoto

Nuclear Technology / Volume 168 / Number 3 / December 2009 / Pages 901-905

Dose/Dose Rate / Special Issue on the 11th International Conference on Radiation Shielding and the 15th Topical Meeting of the Radiation Protection and Shielding Division (PART 3) / Radiation Protection /

Line-beam response function (LBRF) and conical-beam response function (CBRF) data for gamma-ray skyshine are generated using the EGS4 code in an arbitrary geometry for energies ranging from 0.1 to 10 MeV at all the emitted angles up to a distance of 2000 m from the source. The skyshine dose is calculated for the air kerma, exposure, ambient dose equivalent H*(10), and effective dose E with anterior-posterior and isotropic irradiation geometries.

A response function with a four-parameter empirical formula,

R(E,,x) = [fraktur R]E(/0)2 exp(a + cx/0)xb+dx/0,

can be used to approximate the LBRF and CBRF with good accuracy. The values of the four parameters a, b, c, and d are determined for a given beam energy and direction by fitting the four-parameter function such that the maximum fractional deviation of the LBRF and CBRF values is minimized for a set of discrete source-to-detector distances. The parameter set is selected to realize the interpolation of LBRF and CBRF in relation to the energy and direction by the interpolation of these parameters. Consequently, discrete LBRF and CBRF data are converted to continuous data with regard to both energy and direction.

The evaluation of gamma-ray skyshine dose analyses can be accomplished easily and quickly by using the four-parameter formula.

These data can be downloaded in Excel format from as "Data Library of Line- and Conical-Beam Response Functions and Four-Parameter Empirical Formula in Approximating Response Functions for Gamma-Ray Skyshine Dose Analyses."

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