Agzendix C Symbols, constants and equations used to calculate the 13705 - 137m, total body dose equivalent during the uptake interval and the committed dose equivalent The following definitions, symbols, constants and equations deseribe the mathematical model used to calculate the dose equivalent and the committed dose equivalent. Intermediate steps can be used to determine urine activity concen- trations or daily ingestion rates. The equations were developed with the assumption that the body burden as determined from whole body counting, would be the measured quantity from the bioassay program. Three intervals of monotonicaily increasing, but constant and continuous uptake throughout an interval were assumed. Consequently, the equations must be repeated 3 times in orger to obtain the total dose equivalent during the uptake interval. 137. . ts, For . the uptake interval corresponds to the number of days out of the resi- dence period that an individual maintained the proposed daiiy activity ingestion rate. Mathematical Model Symools, Definitions and Units of Physical Quantities Nt = the number of atoms of species of concern present at time zero in compartment i, atoms, Ne = the instantaneous number of atoms of species of concern present at time t in compartment i, atoms, P, R = atom intake rate into compartment i frem blood, atoms day, the instantaneous fraction of atoms removed from compartment i per unit time by physiological mechanisms, day, 31