|(a) As used in the rules in this chapter, the International
System of Units (SI) unit of exposure is the coulomb/kilogram (C/kg)
of air. The special unit of exposure is the roentgen. One roentgen
equals 2.58 x 10-4 coulomb/kilogram of
(b) As used in the rules in this chapter, the units
of radiation dose are as follows:
(1) Rad is the special unit of absorbed dose. One rad
is equal to an absorbed dose of 100 ergs/gram or 0.01 joule/kilogram
(2) Gray (Gy) is the SI unit of absorbed dose. One
gray is equal to an absorbed dose of 1 joule/kilogram (100 rads).
(3) Rem is the special unit of any of the quantities
expressed as dose equivalent. The dose equivalent in rem is equal
to the absorbed dose in rad multiplied by the quality factor (1 rem
= 0.01 sievert).
(4) Sievert (Sv) is the SI unit of any of the quantities
expressed as dose equivalent. The dose equivalent in sievert is equal
to the absorbed dose in gray multiplied by the quality factor (1 sievert
= 100 rems).
(c) As used in the rules in this chapter, the quality
factors for converting absorbed dose to dose equivalent are shown
in Table I.
(d) If it is more convenient to measure the neutron
fluence rate than to determine the neutron dose equivalent rate in
rem/hour or sievert/hour, as provided in subsection (c) of this section,
1 rem (0.01 sievert) of neutron radiation of unknown energies may,
for purposes of the rules in this chapter, be assumed to result from
a total fluence of 25 million neutrons/square centimeter incident
upon the body. If sufficient information exists to estimate the approximate
energy distribution of the neutrons, the licensee may use the fluence
rate per unit dose equivalent or the appropriate Q value from Table
II to convert a measured tissue dose in rad (gray) to dose equivalent
in rem (sievert).