492 TRANSURANIC ELEMENTS IN THE ENVIRONMENT 



INHALATIOixi 



EXHALED 25% -^ 



INGESTION 



GASTROINTESTINAL 

 TRACT (18-hr TRANSIT) 



LIVER 

 (30.000 days) 



KIDNEY 

 (32,000 days) 



BONE 

 (73,000 days) 



12.5% (INSOLUBLE 

 COMPOUNDS) 



12.5% 



(INSOLUBLE 



COMPOUNDS) 



1 00% 



1 00% 



FAST 



(1-day 

 transit) 



1 



SLOW 



(365 

 days) 



DEEP LUNG 



Fig. 3 International Commission on Radiological Protection Committee II model for 

 plutonium. Fraction from blood to total body is 100%. Biological half-time in total body 

 is 65 ,000 days. 



None of the soluble compound resides in the lung for any significant length of time 

 and therefore does not contribute a radiation dose to the lung. For insoluble compounds, 

 in the absence of other data, it is assumed that 25% is exhaled, 50% is swallowed and 

 reaches the GIT immediately, and 25% is immediately transferred directly to tissues deep 

 in the lung. Of the amount transferred to the deep lung, half ( 12.5% of that inhaled) is 

 coughed up within 24 hr and is swallowed (reaches the GIT). The remainder (12.5% of 

 that inhaled) resides in the deep lung with a half-time of 365 days and is then transferred 

 to the blood. To avoid underestimating radiation doses, we use the insoluble parameters 

 for calculating the transfer to the lung and GIT but use the soluble parameters for the 

 transfer to all other organs. 



On the basis of Fig. 3 and 'he above discussion, the equations for the ICRP II model 

 are 



•"GIT - fuRG Am + fuRDLI A,n + H 



111 



{33} 



•"B - *URB Am + fGlTB 'GIT 



YGIT - 'GIT TgIT 



(34) 

 (35) 



dypLS 

 dt 



- 'liRDLS Am - (Aa + Adls) VDLS 



(36) 



