ApDeacix 3 Symbols, . : constants and equations used to calculate 90 Sr- 30 Y bone marrow dose equivalent during the uptake interval and the committed dose equivalent The following definition, symbols, constants and equations describe the mathematical model used to calculate dose equivalent during and post the uptake interval. Intermediate steps can be used to determine body burdens or daily ac- tivity ingestion rates. The equations were developed with the assumption that the measured quantity from a bioassay program would be the urine activity concen. tration. . Constant continuous uptake of 3 0 was assumed for the entire residence period. equals the residency period. . . sr- Oy through the ingestion pathway For 905,, the uptake interval As indicated previously 905, disintegrations are divided equally between cortical and trabecular bone. Mathematical Model ’ Symbols, Definitions and Units of Physical Quantities Ne = the number of atoms of species of concern present at time zero in compartment i, atoms, N; = the instantaneous number of atoms of species of concern present at time t in compartment i, atoms, Ps = atom intake rate into compartment i from blood, atoms day |, KR. = the instantaneous fraction of atoms removed from compartment i per unit time by physiological mechanisms, day |, r = the instantaneous fraction of atoms removed from compartment i per unit time by radiological mechanisms, day |, q; = the instantaneous activity in compartment i at time t, Becquerels, Ey = the instantaneous activity excretion rate from compartment i at time ct Becquerels day/, 25