| (7) The licensee shall reduce the dose that an individual
may be allowed to receive in the current year by the amount of occupational
dose received while employed by any other person. See subsection (j)(4)
of this section.
(g) Compliance with requirements for summation of external
and internal doses.
(1) If the licensee is required to monitor in accordance
with both subsection (q)(1) and (3) of this section, the licensee
shall demonstrate compliance with the dose limits by summing external
and internal doses. If the licensee is required to monitor only in
accordance with subsection (q)(1) of this section or only in accordance
with subsection (q)(3) of this section, then summation is not required
to demonstrate compliance with the dose limits. The licensee may demonstrate
compliance with the requirements for summation of external and internal
doses in accordance with paragraphs (2) - (4) of this subsection.
The dose equivalents for the lens of the eye, the skin, and the extremities
are not included in the summation, but are subject to separate limits.
(2) If the only intake of radionuclides is by inhalation,
the total effective dose equivalent limit is not exceeded if the sum
of the deep dose equivalent divided by the total effective dose equivalent
limit, and one of the following, does not exceed unity:
(A) the sum of the fractions of the inhalation ALI
for each radionuclide; or
(B) the total number of derived air concentration-hours
(DAC-hours) for all radionuclides divided by 2,000; or
(C) the sum of the calculated committed effective dose
equivalents to all significantly irradiated organs or tissues (T)
calculated from bioassay data using appropriate biological models
and expressed as a fraction of the annual limit. For purposes of this
requirement, an organ or tissue is deemed to be significantly irradiated
if, for that organ or tissue, the product of the weighting factors,
wT , and the committed dose equivalent,
HT,50 , per unit intake is greater than
10% of the maximum weighted value of HT,50 ,
that is, wT HT,50 ,
per unit intake for any organ or tissue.
(3) If the occupationally exposed individual receives
an intake of radionuclides by oral ingestion greater than 10% of the
applicable oral ALI, the licensee shall account for this intake and
include it in demonstrating compliance with the limits.
(4) The licensee shall evaluate and, to the extent
practical, account for intakes through wounds or skin absorption.
The intake through intact skin has been included in the calculation
of DAC for hydrogen-3 and does not need to be evaluated or accounted
for in accordance with this paragraph.
(h) Determination of external dose from airborne radioactive
material.
(1) Licensees shall, when determining the dose from
airborne radioactive material, include the contribution to the deep
dose equivalent, eye dose equivalent, and shallow dose equivalent
from external exposure to the radioactive cloud. See footnotes 1 and
2 of subsection (ggg)(2) of this section.
(2) Airborne radioactivity measurements and DAC values
shall not be used as the primary means to assess the deep dose equivalent
when the airborne radioactive material includes radionuclides other
than noble gases or if the cloud of airborne radioactive material
is not relatively uniform. The determination of the deep dose equivalent
to an individual shall be based upon measurements using instruments
or individual monitoring devices.
(i) Determination of internal exposure.
(1) For purposes of assessing dose used to determine
compliance with occupational dose equivalent limits, the licensee
shall, when required in accordance with subsection (q) of this section,
take suitable and timely measurements of:
(A) concentrations of radioactive materials in air
in work areas;
(B) quantities of radionuclides in the body;
(C) quantities of radionuclides excreted from the body;
or
(D) combinations of these measurements.
(2) Unless respiratory protective equipment is used,
as provided in subsection (x) of this section, 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;
(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 subsection (ggg)(2) of this
section.
(4) If the licensee chooses to assess intakes of Class
Y material using the measurements given in paragraph (1)(A) or (B)
of this subsection, the licensee may delay the recording and reporting
of the assessments for periods up to seven months, unless otherwise
required by subsections (xx) or (yy) of this section. 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 subsection (ggg)(2)
of this section 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 subsection (f)
of this section and in complying with the monitoring requirements
in subsection (q)(3) of this section;
(B) the concentration of any radionuclide disregarded
is less than 10% of its DAC; and
(C) the sum of these percentages for all of the radionuclides
disregarded in the mixture does not exceed 30%.
(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 may assume that the inhalation of 1 ALI,
or an exposure of 2,000 DAC-hours, results in a committed effective
dose equivalent of 5 rems (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 rems (0.5 Sv), the intake
of radionuclides that would result in a committed effective dose equivalent
of 5 rems (0.05 Sv), that is, the stochastic ALI, is listed in parentheses
in Table I of subsection (ggg)(2) of this section. 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 subsection
(f)(1)(A)(ii) of this section is met.
(j) Determination of occupational dose for the current
year.
(1) For each individual who is likely to receive, in
a year, an occupational dose requiring monitoring in accordance with
subsection (q) of this section, the licensee shall determine the occupational
radiation dose received during the current year.
(2) In complying with the requirements of paragraph
(1) of this subsection, a licensee may:
(A) accept, as a record of the occupational dose that
the individual received during the current year, RC Form 202-2 from
prior or other current employers, or other clear and legible record,
of all information required on that form and indicating any periods
of time for which data are not available; or
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