Current through Register Vol. 47, No. 6, September 18, 2024
(1)
For purposes of assessing dose used to determine compliance with occupational
dose equivalent limits, the licensee shall, when required pursuant to
40.37(136C), take suitable and timely measurements of:
a. Concentrations of radioactive materials in
air in work areas; or
b. Quantities
of radionuclides in the body; or
c.
Quantities of radionuclides excreted from the body; or
d. Combinations of these
measurements.
(2) Unless
respiratory protective equipment is used, as provided in 40.50(136C), or the
assessment of intake is based on bioassays, the licensee shall assume that an
individual inhales radioactive material at the airborne concentration in which
the individual is present.
(3) When
specific information on the physical and biochemical properties of the
radionuclides taken into the body or the behavior of the material in an
individual is known, the licensee may:
a. Use
that information to calculate the committed effective dose equivalent, and, if
used, the licensee shall document that information in the individual's record;
and
b. Upon prior approval of the
agency, adjust the DAC or ALI values to reflect the actual physical and
chemical characteristics of airborne radioactive material, for example, aerosol
size distribution or density; and
c. Separately assess the contribution of
fractional intakes of Class D, W, or Y compounds of a given radionuclide to the
committed effective dose equivalent. See Appendix B.
(4) If the licensee chooses to assess intakes
of Class Y material using the measurements given in 40.8(1)"b"
or 40.8(1)"c," the licensee may delay the recording and
reporting of the assessments for periods up to seven months, unless otherwise
required by 40.96(136C) or 40.97(136C). This delay permits the licensee to make
additional measurements basic to the assessments.
(5) If the identity and concentration of each
radionuclide in a mixture are known, the fraction of the DAC applicable to the
mixture for use in calculating DAC-hours shall be either:
a. The sum of the ratios of the concentration
to the appropriate DAC value, that is, D, W, or Y, from Appendix B for each
radionuclide in the mixture; or
b.
The ratio of the total concentration for all radionuclides in the mixture to
the most restrictive DAC value for any radionuclide in the mixture.
(6) If the identity of each
radionuclide in a mixture is known, but the concentration of one or more of the
radionuclides in the mixture is not known, the DAC for the mixture shall be the
most restrictive DAC of any radionuclide in the mixture.
(7) When a mixture of radionuclides in air
exists, a licensee may disregard certain radionuclides in the mixture if:
a. The licensee uses the total activity of
the mixture in demonstrating compliance with the dose limits in 40.15(136C) and
in complying with the monitoring requirements in 40.37(136C), and
b. The concentration of any radionuclide
disregarded is less than 10 percent of its DAC, and
c. The sum of these percentages for all of
the radionuclides disregarded in the mixture does not exceed 30
percent.
(8) When
determining the committed effective dose equivalent, the following information
may be considered:
a. In order to calculate
the committed effective dose equivalent, the licensee or registrant may assume
that the inhalation of one ALI, or an exposure of 2,000 DAC-hours, results in a
committed effective dose equivalent of 5 rem (0.05 Sv) for radionuclides that
have their ALIs or DACs based on the committed effective dose
equivalent.
b. For an ALI and the
associated DAC determined by the nonstochastic organ dose limit of 50 rem (0.5
Sv), the intake of radionuclides that would result in a committed effective
dose equivalent of 5 rem (0.05 Sv), that is, the stochastic ALI, is listed in
parentheses in Table I of Appendix B. The licensee or registrant may, as a
simplifying assumption, use the stochastic ALI to determine committed effective
dose equivalent. However, if the licensee or registrant uses the stochastic
ALI, the licensee or registrant shall also demonstrate that the limit in
40.15(1)"a"(2) is met.
