Assessment of Intake, Exposure, and Dose from Radon, Thoron, and Their Progeny

DOE-STD-1121-98

where

denotes the concentration of 218Po in pCi/L;

CPo-218

denotes the concentration of 214Pb in pCi/L; and

CPb-214

denotes the concentration of 214Bi in pCi/L.

CBi-214

PAEC can be computed from concentration measurements of the short-lived thoron progeny in air

(UNSCEAR 1993):

(29)

where

denotes the concentration of 212Po in pCi/L; and

CPb-212

denotes the concentration of 212Bi in pCi/L.

CBi-212

Another acceptable method for workplace monitoring of exposure to radon progeny is to measure

222

the Rn itself, and convert it to PAEC using known equilibrium factors. DOE's 10 CFR 835 permits

calculating equilibrium equivalent concentration, EEC, from radon concentration measurements, C,

based on knowledge or assumption of an equilibrium factor, F:

(30)

If F has not been measured, it is acceptable under some circumstances to assume a default indoor value of

FRn = 0.4 (UNSCEAR 1988, 1993; ICRP 1993a). If C is in units of :Ci/mL, then EEC will also be in

units of :Ci/mL (note: 1 pCi/L = 10!9 :Ci/mL).

For 222Rn, FRn is defined as

(31)

where

= the concentration of 218Po;

CPo-218

= the concentration of 214Pb;

CPb-214

= the concentration of 214Bi; and

CBi-214

= the concentration of 222Rn.

CRn-222

For 220Rn, FTn is defined as

(32)

where