Title 10 Part 835 Appendix A Code of Federal Regulations (2024)

Appendix A to Part 835 - Derived Air Concentrations (DAC) for Controlling Radiation Exposure to Workers at DOE Facilities

10:4.0.2.5.28.14.74.5.21 : Appendix A

Appendix A to Part 835 - Derived Air Concentrations (DAC) forControlling Radiation Exposure to Workers at DOE Facilities

The data presented in appendix A are to be used for controllingindividual internal doses in accordance with § 835.209, identifyingthe need for air monitoring in accordance with § 835.403, andidentifying and posting airborne radioactivity areas in accordancewith § 835.603(d).

The DAC values are given for individual radionuclides. For knownmixtures of radionuclides, determine the sum of the ratio of theobserved concentration of a particular radionuclide and itscorresponding DAC for all radionuclides in the mixture. If this sumexceeds unity (1), then the DAC has been exceeded. For unknownradionuclides, the most restrictive DAC (lowest value) for thoseisotopes not known to be absent shall be used. For any singleradionuclide not listed in appendix A with decay mode other thanalpha emission or spontaneous fission and with radioactivehalf-life greater than two hours, the DAC value shall be 4 E-11µCi/mL (1 Bq/m 3). For any single radionuclide not listed inappendix A that decays by alpha emission or spontaneous fission theDAC value shall be 2 E-13 µCi/mL (8 E-03 Bq/m 3).

The DACs for limiting radiation exposures through inhalation ofradionuclides by workers are listed in this appendix. The valuesare based on either a stochastic (committed effective dose) doselimit of 5 rems (0.05 Sv) or a deterministic (organ or tissue) doselimit of 50 rems (0.5 Sv) per year, whichever is more limiting.

Note:

The 15 rems (0.15 Sv) dose limit for the lens of the eye doesnot appear as a critical organ dose limit.

The columns in this appendix contain the following information:(1) Radionuclide; (2) inhaled air DAC for type F (fast), type M(moderate), and type S (slow) materials in units of µCi/mL; (3)inhaled air DAC for type F (fast), type M (moderate), and type S(slow) materials in units of Bq/m 3; (4) an indication of whetheror not the DAC for each class is controlled by the stochastic(effective dose) or deterministic (organ or tissue) dose. Theabsorption types (F, M, and S) have been established to describethe absorption type of the materials from the respiratory tractinto the blood. The range of half-times for the absorption typescorrespond to: Type F, 100% at 10 minutes; Type M, 10% at 10minutes and 90% at 140 days; and Type S 0.1% at 10 minutes and99.9% at 7000 days. The DACs are listed by radionuclide, in orderof increasing atomic mass, and are based on the assumption that theparticle size distribution of 5 micrometers AMAD is used. Forsituations where the particle size distribution is known to differsignificantly from 5 micrometers AMAD, appropriate corrections maybe made to both the estimated dose to workers and the DACs.

Footnotes for Appendix A

1 A determination of whether the DACs are controlled bystochastic (St) or deterministic (organ or tissue) dose, or if theyboth give the same result (E), for each absorption type, is givenin this column. The key to the organ notation for deterministicdose is: BS = Bone surface, ET = Extrathoracic, K = Kidney, L =Liver, and T = Thyroid. A blank indicates that no calculations wereperformed for the absorption type shown.

2 The ICRP identifies these materials as soluble or reactivegases and vapors or highly soluble or reactive gases and vapors.For tritiated water, the inhalation DAC values allow for anadditional 50% absorption through the skin, as described in ICRPPublication No. 68, Dose Coefficients for Intakes of Radionuclidesby Workers. For elemental tritium, the DAC values include a factorthat irradiation from gas within the lungs might increase the doseby 20%.

3 A dash indicates no values given for this data category.

4 DAC values derived using hafnium tritide particle and arebased on “observed activity” (i.e, only radiation emitted from theparticle is considered). DAC values derived using methodology foundin Radiological Control Programs for Special Tritium Compounds,DOE-HDBK-1184-2004.

5 These values are appropriate for protection from radoncombined with its short-lived decay products and are based oninformation given in ICRP Publication 65: Protection AgainstRadon-222 at Home and at Work and in DOE-STD-1121-98: InternalDosimetry. The values given are for 100% equilibrium concentrationconditions of the short-lived radon decay products with the parent.To allow for an actual measured equilibrium concentration or ademonstrated equilibrium concentration, the values given in thistable should be multiplied by the ratio (100%/actual %) or(100%/demonstrated %), respectively. Alternatively, the DAC valuesfor Rn-220 and Rn-222 may be replaced by 2.5 working level (WL) and0.83 WL, respectively, for appropriate limiting of decay productconcentrations. A WL is any combination of short-lived radon decayproducts, in one liter of air without regard to the degree ofequilibrium, that will result in the ultimate emission of 1.3 E +05 MeV of alpha energy.

[72 FR 31927, June 8, 2007]