Current through Register 1531, September 27, 2024
(A) For
purposes of assessing dose used to determine compliance with occupational dose
equivalent limits, the licensee shall, when required pursuant to
105
CMR 120.226, take suitable and timely
measurements of:
(1) concentrations of
radioactive materials in air in work areas; or
(2) quantities of radionuclides in the body;
or
(3) quantities of radionuclides
excreted from the body; or
(4)
combinations of these measurements.
(B) Unless respiratory protective equipment
is used, as provided in
105 CMR
120.233, 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;
(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, for example, 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 to the committed effective dose equivalent.
See
105
CMR 120.296: Appendix
B.
(D) If the
licensee chooses to assess intakes of Class Y material using the measurements
given in 105 CMR 120.214(A)(2) or (3), the licensee may delay the recording and
reporting of the assessments for periods up to seven months, unless otherwise
required by
105 CMR
120.282 or
105
CMR 120.283. 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, that is, D, W, or Y, from
105
CMR 120.296: Appendix B 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
105 CMR
120.211 and in complying with the monitoring
requirements in
105
CMR 120.226(B);
(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%.
(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 sievert (5 rems) 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 sievert (50 rems), the
intake of radionuclides that would result in a committed effective dose
equivalent of 0.05 sievert (5 rems), that is, the stochastic ALI, is listed in
parentheses in
105
CMR 120.296: Appendix B,
Table I. 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
105 CMR
120.211(A)(1)(b) is
met.
