G.
Dietze, D.T. Bartlett, D.A. Cool, F.A. Cucinotta, X. Jia, I.R. McAulay, M.
Pelliccioni, V. Petrov, G, G. Reitz, T. Sato
Astronauts, during their occupational activities in space, are exposed to ionising radiation from natural radiation sources present in the environment. The exposure assessment and risk-related approach described in this report is clearly restricted to the special situation in space, and should not be applied to the system of radiological protection followed on Earth.
The
report describes the terms and methods used to assess the radiation exposure of
astronauts, and provides data for the assessment of organ doses. Chapter 1
describes the specific situation of astronauts in space, and the differences in
the radiation fields compared with those on Earth. In Chapter 2, the radiation
fields in space are described in detail, including galactic cosmic radiation,
radiation from the Sun and its special solar particle events, and the radiation
belts surrounding the Earth. Chapter 3 deals with the quantities used in
radiological protection, describing the Publication 103 system of dose
quantities, and subsequently presenting the special approach for applications
in space; due to the strong contribution of heavy ions in the radiation field,
radiation weighting is based on the radiation quality factor, Q, instead of the
radiation weighting factor, wR. In Chapter 4, the methods of fluence and dose
measurement in space are described, including instrumentation for fluence
measurements, radiation spectrometry, and area and individual monitoring. The
use of biomarkers for the assessment of mission doses is also described. The
methods of determining quantities describing the radiation fields within a
spacecraft are given in Chapter 5. Radiation transport calculations are the
most important tool. Some physical data used in radiation transport codes are
presented, and the various codes used for calculations in high-energy radiation
fields in space are described. Results of calculations and measurements of
radiation fields in spacecraft are given. Some data for shielding possibilities
are also presented. Chapter 6 addresses methods of determining mean absorbed
doses and dose equivalents in organs and tissues of the human body. Calculated
conversion coefficients of fluence to mean absorbed dose in an organ or tissue
are given for heavy ions up to Z = 28 for energies from 10 MeV/u to 100 GeV/u. Doses
in the body obtained by measurements are compared with results from
calculations, and biodosimetric measurements for the assessment of mission
doses are also presented. In Chapter 7, operational measures are considered for
assessment of the exposure of astronauts during space missions. This includes
pre-flight mission design, area and individual monitoring during flights in
space, and dose recording. The importance of the magnitude of uncertainties in
dose assessment is considered.
Annex
A shows conversion coefficients and mean quality factors for protons, charged
pions, neutrons, alpha particles, and heavy ions (2 < Z ≤ 28), and particle
energies up to 100 GeV/u (Source: www.icrp.org).
