Specific Definitions

DOE-STD-1121-98

bioassay: Another word for radiobioassay.

biokinetic model: A series of often empirically determined mathematical relationships formulated to

describe the intake, deposition in respiratory tract (if applicable), uptakes by the transfer compartment

from intake compartment(s), uptakes by tissues or organs from the transfer compartment, translocation,

retention, and elimination of a radionuclide from the body.

censored data: Data that have been recorded as "less than" values rather than the observed numerical

values (whether positive, zero, or negative).

committed dose equivalent (HT,50): The dose equivalent calculated to be received by a tissue or organ

over a 50-year period after the intake of a radionuclide into the body. It does not include contributions

from radiation sources external to the body. Committed dose equivalent is expressed in units of rems (or

sieverts). (10 CFR 835)

Note: For exposures to the short-lived radioactive progeny of 222Rn and 220Rn, see the definition

of committed effective dose equivalent (below).

committed effective dose equivalent (HE,50): The sum of the committed dose equivalents to various

tissues or organs in the body (HT,50), each multiplied by the appropriate tissue weighting factor (wT): that

is, HE,50 = EwTHT,50. Committed effective dose equivalent (CEDE) is expressed in units of rems (or

sieverts). (10 CFR 835)

Note: For exposures to the short-lived radioactive progeny of 222Rn, committed effective dose

equivalent is calculated directly from workplace measurements of potential alpha energy

exposure using a dose conversion factor of 1.25 rem (0.0125 Sv) per working level month

(WLM). For exposures to the short-lived radioactive progeny of 220Rn, committed effective dose

equivalent is calculated directly from workplace measurements of potential alpha energy

exposure using a dose conversion factor of 5/12 rem (5/1200 Sv) per WLM. Since the lung is

the only tissue significantly irradiated by radon and thoron, the committed dose equivalent to

lung due to exposures to radon and thoron is calculated by dividing the committed effective

dose equivalent from radon and thoron by the tissue weighting factor for lung (wT = 0.12).

compartment: The smallest element in a biokinetic model for which a mathematical representation of a

retained quantity is given. Compartments may be organs (e.g., lung, liver), tissues (e.g., bone marrow), or

systemic (e.g., the transfer compartment).

critical level: Same as decision level.

compartment: The smallest element in a biokinetic model for which a mathematical representation of a

retained quantity is given. Compartments may be organs (e.g., lung, liver), tissues (e.g., bone marrow), or

systemic (e.g., the transfer compartment).

derived air concentration (DAC): For the radionuclides listed in Appendix A of 10 CFR 835, the

airborne concentration that equals the ALI divided by the volume of air breathed by an average worker for

a working year of 2000 hours (assuming a breathing volume of 2400 m3).

Note: The footnotes to Appendix A of 10 CFR 835 give some important information about the DACs

listed. In particular, the right-hand column identifies the origin of each DACwhether it was

derived from the stochastic dose limit or the non-stochastic dose limit for a particular organ. Only