Radon, radioactive

CAS RN: 10043-92-2

Radiation Limits / Potential

Radon-222 has a half-life of 3.82 days and decays by alpha-particle emission to polonium-218), which by further decay through isotopes of lead, bismuth, polonium and thallium ends the uranium-238 decay chain with stable lead-206.
Radium-226 decays to a noble gas, radon-222. Radon-226 has a 1,600 year half-life while radon-222 has a 3.8 day half-life. The latter decays to produce four short-lived decay products also known as progeny or daughters. These short-lived daughters are polonium-218, lead-214, bismuth-214, and polonium-214. Their effective half-life is approximately 30 minutes. Polonium-214 decays to produce the long-lived lead-210 (ca. 20 year half-life) which then decays to bismuth-210 and polonium-210.
Radon-222 (half life of 3.82 days) is an intermediate in the Uranium-238 Series; Radon-220 (half life 55 sec) is an intemediate in the Thorium-232 Series; Radon-219 (half life 4.0 sec) is an intermediate in the Uranium-235 series.
DECAY PRODUCTS (PROGENY) OF RADON-222 GAS. Radon-222 through Polonium-214 are short-lived progeny (principal hazard to uranium workers); Lead-210 through Polonium-210 are long-lived radon progeny (principal hazard from fallout).
RADON PROGENY HALF LIFE EMISSION
Radon-222 3.8 days alpha
Polonium-218 3 minutes alpha
Lead-214 27 minutes beta
Bismuth-214 20 minutes beta
Polonium-214 180 microseconds beta
Lead-210 22 years beta
Bismuth-210 5 days beta
Polonium-210 138 days alpha
Lead-206 stable -
Half-life = 3.96 seconds /Radon-219/
Half-life = 55.6 seconds /Radon-220/
Half-life = 3.823 days /Radon-222/
Specific activity (Ci/g): Radon-222 3.6x10+4; Radon-220 9.3x10+8; Radon-219 1.3x10+10.
ALI values have been established for individual radionuclides and are presented in Table 1 in Appendix B to PART 20.1001-20.2401. The ALI values for inhalation, presented in Column 2 in Table 1, correspond to a committed effective dose equivalent of 5 rems (0.05 Sv) or a committed dose equivalent of 50 rems (0.5 Sv) to any individual organ or tissue, whichever is more limiting. If the ALI value presented in Table 1 is limited by the 50-rem committed dose equivalent, the controlling organ is listed directly below the ALI value, and the stochastic ALI value based on the 5-rem committed effective dose equivalent is listed in parentheses directly below the organ name. If a stochastic ALI is listed in parentheses, that value should be used to calculate the committed effective dose equivalent.
OCCUPATIONAL VALUES FOR RADON-220
CLASS ORAL Ingestion ALI (uCi) INHALATION ALI (uCi) INHALATION DAC (uCi/mL)
With daughters removed - 2E+4 7E-6
With daughters present - 2E+1 (or 12 working level months) 9E-9 (or 1.0 working level)
OCCUPATIONAL VALUES FOR RADON-222
CLASS ORAL Ingestion ALI (uCi) INHALATION ALI (uCi) INHALATION DAC (uCi/mL)
With daughters removed - 1E+4 4E-6
With daughters present - 1E+2 (or 4 working level months) 3E-8 (or 0.33 working level)
EFFLUENT CONCENTRATIONS ESTABLISHED BY THE NRC FOR RADON COMPOUNDS
RADIONUCLIDE CLASS AIR (uCi/mL) WATER (uCi/mL)
Radon-220 With daughters removed 2E-8 -
With daughters present 3E-11 -
Radon-222 With daughters removed 1E-8 -
With daughters present 1E-10 -
QUANTITIES OF NRC LICENSED MATERIAL REQUIRING LABELING
RADIONUCLIDE QUANTITY (uCi)
Uranium-230 0.01
Uranium-232 0.001
Uranium-233 0.001
Uranium-234 0.001
Uranium-235 0.001
Uranium-236 0.001
Uranium-237 100
Uranium-238 100
Uranium-239 1,000
Uranium-240 100
Uranium-natural 100
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