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

DOE-STD-1121-98

= the concentration of 212Pb;

CPb-212

= the concentration of 212Bi; and

CBi-212

= the concentration of 220Rn (thoron).

CRn-220

To assess radon progeny exposure from a time-integrated measurement using a nuclear track

detector, one must understand the measurement itself4. The fundamental result of a measurement with a

nuclear track detector is an observed number of tracks per unit area. Nuclear track detectors typically

have an area of 10 to 20 mm2. The number of tracks per mm2 is empirically related to a number of

radioactive transitions (of radon) per unit volume of air that occurred during exposure, that is, a time-

integrated radon concentration. One commonly reported unit is picocurie-days per liter (pCi-d/L), where

(33)

The average concentration and average equilibrium equivalent concentration, ' and EE', during the

where the numerical conversion factors are given to five significant figures to prevent round-off error.

exposure, uncorrected for background, can be calculated by knowing the exposure time, tE (d), the

(34)

number of transitions per unit volume, NV, and the equilibrium factor using

However, PAEE is directly proportional to NV without the need for the intermediate step of

calculating an average concentration:

(35)

Committed effective dose equivalent is assessed directly from PAEE using

The commercial nuclear track detectors for radon are insensitive to thoron.