496 TRANSURANIC ELEMENTS IN THE ENVIRONMENT 



dyLMf _ 



dl ^ 



t'i) ^hYPh ~ ''^AYLMf 



(57) 



YLM - YLMi + YLMf 



(58) 



where r, X, y, Hm, f, and A^ are as defined in llie ICRP II model and the subscripts, 

 where different, refer to the compartments and the pathways listed in Fig. 4 and Table 9; 



TBf,^ 



IS 



the residence time of material following pathways f and g in the 



tracheobroncliial region (days); and D3, D4, and D5 are the fractions of inhaled material 

 that are deposited in the nasopharyngeal, tracheobronchial, and pulmonary regions, 

 respectively, of the respiratory tract (see Fig. 4 and Table 9). 



Values of most of the parameters in the above equations are given in Table 9 (U. S. 

 Nuclear Regulatory Commission, 1976). TjBf is assumed to be 1 hr, or %4 day 

 (Snyder, 1967; Kotrappa, 1968; 1969), and f j ts identical to fciTB (0.003%) in the 



TABLE 9 Task Group Lung Model Parameter Values 



Fraction of Inhaled Particles Deposited in the Respiratory 

 System vs. Particle Diameter* 



Fraction of inhaled quantity retained 



Clearance Parameter Valuesf 



Translocation class 



*Estimaled trom data of Morrow et al. ( 1 966). 



tAs amended by ICRP Publication 19 |lntcrnational Com- 

 mission on Radiolopical Protection (1972)]. 



^k is clearance pathway (see l"ig. 4); T^ is biological half-time 

 (days) for pathway k; f;^ is fraction cleared by pathway k. 



