For purposes of assessing dose used to
determine compliance with occupational dose equivalent limits, the licensee
shall, when required under
take suitable and timely measurements of either:
1. Concentrations of radioactive materials in
air in work areas;
2. Quantities of
radionuclides in the body;
Quantities of radionuclides excreted from the body; or
4. Combinations of these
respiratory protective equipment is used as provided in
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.
When specific information on the physical
and biochemical properties of the radionuclides taken into the body or the
behavior or 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;
2. Upon prior approval from 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
Separately assess the contribution of fractional intakes of Class D, W, or Y
compounds of a given radionuclide (see Appendix B to 10 CFR Part 20
) to the
committed effective dose equivalent.
If the licensee chooses to assess intakes
of Class Y material using the measurements given in subdivision A 2 or A 3 of
this section, the licensee may delay the recording and reporting of the
assessments for periods up to seven months, unless otherwise required by
in order to permit the licensee to make additional measurements basic to the
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:
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 Part
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.
When a mixture of radionuclides in air
exists, licensees may disregard certain radionuclides in the mixture if:
The licensee uses the total activity of
the mixture in demonstrating compliance with the dose limits in
and in complying with the monitoring requirements in
2. The concentration of any
radionuclide disregarded is less than 10% of its DAC, and
3. The sum of these percentages for all of
the radionuclides disregarded in the mixture does not exceed 30%.
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 5 rem (0.05 Sv) for radionuclides that have their ALIs or DACs
based on the committed effective dose equivalent.
When the ALI and the associated DAC is
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) (the stochastic ALI) is listed in parentheses of Appendix B to
10 CFR Part 20
. In this case, the licensee may, as a simplifying assumption,
use the stochastic ALIs to determine committed effective dose equivalent.
However, if the licensee uses the stochastic ALIs, the licensee shall also
demonstrate that the limit in
A 1 (b) is met.
12 Va. Admin. Code § 5-481-670
Virginia Register Volume 22, Issue 25, eff. September 20, 2006; amended,
Virginia Register Volume 24, Issue 18, eff. June 12, 2008; volume 32, Issue 24,
eff. August 25, 2016.
Statutory Authority: §
of the Code of Virginia.