Current through Register Vol. 48, No. 38, September 20, 2024
a) For purposes of assessing dose used to
determine compliance with occupational dose equivalent limits, the licensee
shall, when required pursuant to Section
340.520,
take measurements of:
1) Concentrations of
radioactive materials in air in work areas during conditions of operations;
or
2) Quantities of radionuclides
in the body after exposure to materials that could result in an intake;
or
3) Quantities of radionuclides
excreted from the body after exposure to materials that could result in an
intake; or
4) Combinations of these
measurements.
b) Unless
respiratory protective equipment is used, as provided in Section
340.730,
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.
c) 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:
1) 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
2) Upon prior approval of the Agency, adjust
the DAC or ALI values to reflect the actual physical and chemical
characteristics of airborne radioactive material (e.g., aerosol size
distribution or density); and
3)
Separately assess the contribution of fractional intakes of Class D, W or Y
compounds of a given radionuclide (see appendix B to 10 CFR 20, published at 72
Fed. Reg. 55922, October 1, 2007, exclusive of subsequent amendments or
editions) to the committed effective dose equivalent.
d) If the licensee chooses to assess intakes
of Class Y material using the measurements specified in subsections (a)(2) or
(3), the licensee may delay the recording and reporting of the assessments for
periods up to 7 months, unless otherwise required by Sections
340.1220
or
340.1230.
AGENCY NOTE: This delay permits the licensee to make
additional measurements basic to the assessments.
e) 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:
1) The sum of the ratios of the concentration
to the appropriate DAC value (e.g., D, W or Y) from appendix B to 10 CFR 20,
published at 72 Fed. Reg. 55922, October 1, 2007, exclusive of subsequent
amendments or editions, for each radionuclide in the mixture; or
2) The ratio of the total concentration for
all radionuclides in the mixture to the most restrictive DAC value for any
radionuclide in the mixture.
f) 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.
g) When a mixture of radionuclides in air
exists, a licensee may disregard certain radionuclides in the mixture if:
1) The licensee uses the total activity of
the mixture in demonstrating compliance with the dose limits in Section
340.210
and in complying with the monitoring requirements in Section
340.520(b);
2) The concentration of any radionuclide
disregarded is less than 10 percent of its DAC; and
3) The sum of these percentages for all of
the radionuclides disregarded in the mixture does not exceed 30
percent.
h) When
determining the committed effective dose equivalent, the following information
may be considered:
1) In order to calculate
the committed effective dose equivalent, the licensee may assume that the
inhalation of one ALI, or an exposure of 2,000 DAC-hours, results in a
committed effective dose equivalent of 0.05 Sv (5 rem) for radionuclides that
have their ALIs or DACs based on the committed effective dose
equivalent.
2) For an ALI (and the
associated DAC) determined by the nonstochastic organ dose limit of 0.5 Sv (50
rem), the intake of radionuclides that would result in a committed effective
dose equivalent of 0.05 Sv (5 rem) (the stochastic ALI) is listed in
parentheses in table 1 of appendix B to 10 CFR 20, published at 72 Fed. Reg.
55922, October 1, 2007, exclusive of subsequent amendments or editions. The
licensee may, as a simplifying assumption, use the stochastic ALI to determine
committed effective dose equivalent. However, if the licensee uses the
stochastic ALI, the licensee shall also demonstrate that the limit in Section
340.210(a)(1)(B)
is met.
