10 CFR Appendix C to Part 835, Derived Air Concentration (DAC) for Workers From External Exposure During Immersion in a Cloud of Airborne Radioactive Material

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Appendix C to Part 835 - Derived Air Concentration (DAC) for Workers From External Exposure During Immersion in a Cloud of Airborne Radioactive Material

a. The data presented in appendix C are to be used for controlling occupational exposures in accordance with § 835.209, identifying the need for air monitoring in accordance with § 835.403 and identifying the need for posting of airborne radioactivity areas in accordance with § 835.603(d).

b. The air immersion DAC values shown in this appendix are based on a stochastic dose limit of 5 rems (0.05 Sv) per year. Four columns of information are presented: (1) Radionuclide; (2) half-life in units of seconds (s), minutes (min), hours (h), days (d), or years (yr); (3) air immersion DAC in units of µCi/mL; and (4) air immersion DAC in units of Bq/m3. The data are listed by radionuclide in order of increasing atomic mass. The air immersion DACs were calculated for a continuous, nonshielded exposure via immersion in a semi-infinite cloud of airborne radioactive material. The DACs listed in this appendix may be modified to allow for submersion in a cloud of finite dimensions.

c. The DAC values are given for individual radionuclides. For known mixtures of radionuclides, determine the sum of the ratio of the observed concentration of a particular radionuclide and its corresponding DAC for all radionuclides in the mixture. If this sum exceeds unity (1), then the DAC has been exceeded. For unknown radionuclides, the most restrictive DAC (lowest value) for those isotopes not known to be absent shall be used.

Air Immersion DAC

Radionuclide Half-life (µCi/mL) (Bq/m 3)
Ar-37 35.02 d 3E 00 1E 11
Ar-39 269 yr 1E-03 5E 07
Ar-41 1.827 h 3E-06 1E 05
Kr-74 11.5 min 3E-06 1E 05
Kr-76 14.8 h 1E-05 3E 05
Kr-77 74.7 min 4E-06 1E 05
Kr-79 35.04 h 1E-05 6E 05
Kr-81 2.1E 05 yr 7E-04 2E 07
Kr-83m 1.83 h 7E-02 2E 09
Kr-85 10.72 yr 7E-04 2E 07
Kr-85m 4.48 h 2E-05 1E 06
Kr-87 76.3 min 4E-06 1E 05
Kr-88 2.84 h 1E-06 7E 04
Xe-120 40.0 min 1E-05 4E 05
Xe-121 40.1 min 2E-06 8E 04
Xe-122 20.1 h 8E-05 3E 06
Xe-123 2.14 h 6E-06 2E 05
Xe-125 16.8 h 1E-05 6E 05
Xe-127 36.406 d 1E-05 6E 05
Xe-129m 8.89 d 2E-04 7E 06
Xe-131m 11.84 d 5E-04 1E 07
Xe-133 5.245 d 1E-04 5E 06
Xe-133m 2.19 d 1E-04 5E 06
Xe-135 9.11 h 1E-05 6E 05
Xe-135m 15.36 min 1E-05 3E 05
Xe-138 14.13 min 3E-06 1E 05

For any single radionuclide not listed above with decay mode other than alpha emission or spontaneous fission and with radioactive half-life less than two hours, the DAC value shall be 6 E-06 µCi/mL (2 E 04 Bq/m 3).

[ 72 FR 31940, June 8, 2007, as amended at 76 FR 20489, Apr. 13, 2011]

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