Tenn. Comp. R. & Regs. 0400-20-05-.53 - DETERMINATION OF INTERNAL EXPOSURE

(1) To assess the dose used to determine compliance with occupational dose equivalent limits, and when required by Rule 0400-20-05-.71, the licensee shall 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) The licensee shall assume that the concentration of airborne radioactive material inhaled by an individual is equal to the concentration in the individual's ambient air unless:

(a) Respiratory protective equipment is used, as provided in Rule 0400-20-05-.92; or

(b) The assessment of intake is based on bioassays.

(3) When specific information is known about the physical and biochemical properties of the radionuclides taken into the body or the behavior of the material in an individual, 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 Division 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

(c) Separately assess the contribution of fractional intakes of Class D, W or Y compounds of a given radionuclide (see Schedule RHS 8-30) to the committed effective dose equivalent.

(4) If the licensee uses the measurements in subparagraph (1)(b) or (c) of this rule to assess intakes of Class Y material, the licensee may delay recording and reporting the assessments for up to 7 months. This delay is allowed only if:

(a) It is necessary to make additional measurements basic to the assessments;

(b) Recording and reporting are not otherwise required by Rule 0400-20-05-.141 or 0400-20-05-.143.

(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 must be either:

(a) The sum of the ratios of the concentration to the appropriate DAC value (e.g., D, W, Y) from Schedule RHS 8-30 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 the mixture is known, but the concentration of one or more of the radionuclides in the mixture is not known, the DAC for the mixture must be the most restrictive DAC of any radionuclide in the mixture.

(7) When a mixture of radionuclides in air exists, licensees 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 Rule 0400-20-05-.50 and in complying with the monitoring requirements in subparagraph (1)(b) of Rule 0400-20-05-.71;

(b) The concentration of any radionuclide disregarded is less than 10 percent of its DAC; and

(c) The sum of the percentages for all disregarded radionuclides does not exceed 30 percent.

(8) 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 rems (0.05 Sv). This assumption may only be made for radionuclides that have their ALIs or DACs based on the committed effective dose equivalent.

(9) When the ALI (and the associated DAC) is 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) (the stochastic ALI) is listed in parentheses in Table 1 of Schedule RHS 8-30. 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 must also demonstrate that the limit in subparagraph (1)(a) of Rule 0400-20-05-.50 is met.

Notes

Tenn. Comp. R. & Regs. 0400-20-05-.53

Original rule filed February 22, 2012; effective May 22, 2012.

Authority: T.C.A. §§ 68-202-201 et seq., and 4-5-201 et seq.