Footnotes for radionuclide tables in 10 CFR Part 20 Appendix B
^{1} "Submersion" means that values given are for submersion in a hemispherical semiinfinite cloud of airborne material.
^{2} These radionuclides have radiological halflives of less than 2 hours. The total effective dose equivalent received during operations with these radionuclides might include a significant contribution from external exposure. The DAC values for all radionuclides, other than those designated Class "Submersion," are based upon the committed effective dose equivalent due to the intake of the radionuclide into the body and do not include potentially significant contributions to dose equivalent from external exposures. The licensee may substitute 1E7 µCi/ml for the listed DAC to account for the submersion dose prospectively, but should use individual monitoring devices or other radiation measuring instruments that measure external exposure to demonstrate compliance with the limits. (See § 20.1203.)
^{3} For soluble mixtures of U238, U234, and U235 in air, chemical toxicity may be the limiting factor (see § 20.1201(e)). If the percent by weight (enrichment) of U235 is not greater than 5, the concentration value for a 40hour workweek is 0.2 milligrams uranium per cubic meter of air average. For any enrichment, the product of the average concentration and time of exposure during a 40hour workweek shall not exceed 8E3 (SA) µCihr/ml, where SA is the specific activity of the uranium inhaled. The specific activity for natural uranium is 6.77E7 curies per gram U. The specific activity for other mixtures of U238, U235, and U234, if not known, shall be:
SA = 3.6E7 curies/gram U for  Udepleted 
SA = [0.4 + 0.38 (enrichment) + 0.0034 (enrichment)^{2}] E6 , enrichment > 0.72 
where enrichment is the percentage by weight of U235, expressed as percent.
NOTE:
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.
 If the identity of each radionuclide in the mixture is not known, but it is known that certain radionuclides specified in this appendix are not present in the mixture, the inhalation ALI, DAC, and effluent and sewage concentrations for the mixture are the lowest values specified in this appendix for any radionuclide that is not known to be absent from the mixture; or
Radionuclide  Table 1 Occupational Values 
Table 2 Effluent Concentrations 
Table 3 Releases to Sewers 


Col. 1  Col. 2  Col. 3  Col. 1  Col. 2  Monthly Average Concentration (µCi/ml) 

Oral Ingestion ALI (µCi) 
Inhalation  Air (µCi/ml) 
Water (µCi/ml) 

ALI (µCi) 
DAC (µCi/ml) 

If it is known that Ac227D and Cm250W are not present  –  7E4  3E13  –  –  – 
If, in addition, it is known that Ac227W,Y, Th229W,Y, Th230W, Th232W,Y, Pa231W,Y, Np237W, Pu239W, Pu240W, Pu242W, Am241W, Am242mW, Am243W, Cm245W, Cm246W, Cm247W, Cm248W, Bk247W, Cf249W, and Cf251W are not present  –  7E3  3E12  –  –  – 
If, in addition, it is known that Sm146W, Sm147W, Gd148D,W, Gd152D,W, Th228W,Y, Th230Y, U232Y, U233Y, U234Y, U235Y, U236Y, U238Y, Np236W, Pu236W,Y, Pu238W,Y, Pu239Y, Pu240Y, Pu242Y, Pu244W,Y, Cm243W, Cm244W, Cf248W, Cf249Y, Cf250W,Y, Cf251Y, Cf252W,Y, and Cf254W,Y are not present  –  7E2  3E11  –  –  – 
If, in addition, it is known that Pb210D, Bi210mW, Po210D,W, Ra223W, Ra225W, Ra226W, Ac225D,W,Y, Th227W,Y, U230D,W,Y, U232D,W, Pu241W, Cm240W, Cm242W, Cf248Y, Es254W, Fm257W, and Md258W are not present  –  7E1  3E10  –  –  – 
If, in addition, it is known that Si32Y, Ti44Y, Fe60D, Sr90Y, Zr93D, Cd113mD, Cd113D, In115D,W, La138D, Lu176W, Hf178mD,W, Hf182D,W, Bi210mD, Ra224W, Ra228W, Ac226D,W,Y, Pa230W,Y, U233D,W, U234D,W, U235D,W, U236D,W, U238D,W, Pu241Y, Bk249W, Cf253W,Y, and Es253W are not present  –  7E+0  3E9  –  –  – 
If it is known that Ac227D,W,Y, Th229W,Y, Th 232W,Y, Pa231W,Y, Cm248W, and Cm250W are not present  –  –  –  1E14  –  – 
If, in addition, it is known that Sm146W, Gd148D,W, Gd152D, Th228W,Y, Th230W,Y,U232Y, U233Y, U235Y, u236Y, U238Y, UNatY, Mp236W, Mp237W, Pu236W,Y, Pu238W,Y, Pu239W,Y, Pu240W,Y, Pu242W,Y, Pu244W,Y, Am241W, Am242mW, Am243W, Cm243W, Cm244W, Cm245W, Cm246W, Cm247W, Bk247W, Cf249W,Y, Cf250W,Y, Cf251W,Y, Cf252W,Y, and Cf254W,Y are not present  –  –  –  1E13  –  – 
If, in addition, it is known that Sm147W, Gd152W, Pb210D, Bi210mW, Po210D,W, Ra223W, Ra225W, Ra226W, Ac225D,W,Y, Th227W,Y, U230D,W,Y, U232D,W, UNatW, Pu241W, Cm240W, Cm242W, Cf248W,Y, Es254W, Fm257W, and Md258W are not present  –  –  –  1E12  –  – 
If, in addition it is known that Fe60, Sr90, Cd113m, Cd113, In115, I129, Cs134, Sm145, Sm147, Gd148, Gd152, Hg194 (organic), Bi210m, Ra223, Ra224, Ra225, Ac225, Th228, Th230, U233, U234, U235, U236, U238, UNat, Cm242, Cf248, Es254, Fm257, and Md258 are not present  –  –  –  –  1E6  1E5 
If a mixture of radionuclides consists of uranium and its daughters in ore dust (10 µm AMAD particle distribution assumed) prior to chemical separation of the uranium from the ore, the following values may beused for the DAC of the mixture: 6E11 µCi of gross alpha activity from uranium238, uranium234, thorium230, and radium226 per milliliter of air; 3E11 µCi of natural uranium per milliliter of air; or 45 micrograms of natural uranium per cubic meter of air.
If the identity and concentration of each radionuclide in a mixture are known, the limiting values should be derived as follows: determine, for each radionuclide in the mixture, the ratio between the concentration present in the mixture and the concentration otherwise established in Appendix B for the specific radionuclide when not in a mixture. The sum of such ratios for all of the radionuclides in the mixture may not exceed "1" (i.e., "unity").
Example: If radionuclides "A," "B," and "C" are present in concentrations C_{A}, C_{B}, and C_{C}, and if the applicable DACs are DAC_{A}, DAC_{B}, and DAC_{C}, respectively, then the concentrations shall be limited so that the following relationship exists:
C_{A}  +  C_{B}  +  C_{C}  < 1 
DAC_{A}  DAC_{B}  DAC_{C} 