R9-7-105. Quality Factors for Converting Absorbed Dose to Dose Equivalent

A. As used in these rules, the quality factors for converting absorbed dose to dose equivalent are shown in Table I. TABLE I. QUALITY FACTORS AND ABSORBED DOSE EQUIVALENCIES Absorbed Dose Equal to a Unit Dose Equivalenta Quality Factor TYPE OF RADIATION (Q) X, gamma, or beta radiation and high-speed electrons 1 Alpha particles, multiple- charged particles, fission fragments, and heavy particles of unknown charge 20 0.05 Neutrons of unknown energy 10 0.1 High-energy protons 10 0.1 a The absorbed dose in gray is equal to 1 Sv or the absorbed dose in rad is equal to 1 rem. B. If it is more convenient to measure the neutron fluence rate than to determine the neutron dose equivalent rate in sievert per hour or rem per hour, 0.01 Sv (1 rem) of neutron radiation of unknown energies may, for purposes of these rules, be assumed to result from a total fluence of 25 million neutrons per square centimeter incident upon the body. If sufficient information exists to estimate the approximate energy distribution of the neutrons, the licensee or registrant may use the fluence rate per unit dose equivalent or the appropriate Q value from Table II to convert a measured tissue dose in gray or rad to dose equivalent in sievert or rem. TABLE II. MEAN QUALITY FACTORS, Q, AND FLUENCE PER UNIT DOSE EQUIVALENT FOR MONOENERGETIC NEUTRONS Fluence per Unit Dose Equivalentb Fluence per Unit Dose Equivalentb Neutron Energy (meV) Quality Factor (Q) (neutrons cm-2 Sv-1) (thermal) 2.5E-8 2 980E+6 980E+8 1E-7 2 980E+6 980E+8 1E-6 2 810E+6 810E+8 1E-5 2 810E+6 810E+8 1E-4 2 840E+6 840E+8 1E-3 2 980E+6 980E+8 1E-2 2.5 1010E+6 1010E+8 1E-1 7.5 170E+6 170E+8 5E-1 11 39E+6 39E+8 1 11 27E+6 27E+8 2.5 9 29E+6 29E+8 5 8 23E+6 23E+8 7 7 24E+6 24E+8 10 6.5 24E+6 24E+8 14 7.5 17E+6 17E+8 20 8 16E+6 16E+8 (neutrons cm-2 rem-1) 40 7 14E+6 14E+8 60 5.5 16E+6 16E+8 1E+2 4 20E+6 20E+8 2E+2 3.5 19E+6 19E+8 3E+2 3.5 16E+6 16E+8 4E+2 3.5 14E+6 14E+8 a Value of quality factor (Q) at the point where the dose equivalent is maximum in a 30-centimeter diameter cylinder tissue-equivalent phantom. b Monoenergetic neutrons incident normally on a 30-centimeter diameter cylinder tissue-equivalent phantom.