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Exposure in DAC-h
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Internal Dosimetry - index
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Assessment of Intake, Exposure, and Dose from Radon, Thoron, and Their Progeny


DOE-STD-1121-98
and for "other" tissues (stomach wall, liver, kidneys), wT = 0.06, an intake of 1 NALI (2000 DACn-hours)
leads to HE,50 of
(27)
In cases where only a nonstochastic DAC is listed in 10 CFR 835, it is acceptable to use the
corresponding stochastic DAC for the radionuclide, particle size, and chemical form, as listed in Federal
Guidance Report 11 (Eckerman et al. 1988) or in the ICRP Publication 30 series.
7.5.3 Assigned Respiratory Protection Factors for Use in Dose Evaluations
The American National Standards Institute has addressed the use of assigned respiratory protection
factors (ANSI 1992) for planning purposes. Older information can be found in the U.S. Nuclear
Regulatory Commission's regulatory guide and a NUREG report on respiratory protection (NRC 1973,
1976). In addition, "protection factors for respirators" are specified in Appendix A to 20.1001-20.2401
of 10 CFR 20 (NRC 1993b). If a DOE site chooses to use assigned protection factors that differ from
those in the ANSI Standard or 10 CFR 20 Appendix A, then the technical basis for this choice must be
documented. Assigned protection factors for respirators used for radon and thoron and their short-lived
progeny are treated in Section 7.5.7.
7.5.4 Assessment of Intake, Exposure, and Dose from Radon, Thoron, and Their
Progeny
The basis for protection from airborne short-lived decay products of radon and thoron is explained in
ICRP Publication 32 (ICRP 1981b). Exposure to airborne short-lived decay products of radon and thoron
is given the special name potential alpha energy exposure (PAEE) for two reasons:
The relevant ionizing energy is delivered to the bronchial epithelium by alpha particles from 218Po
C
and 214Po in the case of 222Rn and from 212Bi and 212Po in the case of 220Rn (thoron).
C
The decay-product aerosol often contains an unknown mixture of the various radon and/or thoron
progeny.
For radon and thoron progeny, PAEE can be expressed as the product of average potential alpha
energy concentration (PAEC) and worker stay time and divided by the assigned respiratory protection
factor, if any. The traditional unit of PAEC is the working level (WL), and traditionally, stay times have
been measured in occupational "Months" of 170 hours. Thus, the traditional unit of PAEE is the working
level month, or WLM.
For routine monitoring of workers who are chronically exposed, weekly average air concentrations
can be used for workers whose stay times are less than 40 hours in a given week.
PAEC can be computed from concentration measurements of the short-lived radon progeny in air
(NCRP 1990):
(28)
80


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