MODEL FOR ESTIMATING Pu TRANSPORT AND DOSE 501 

 dVALNR 



dt 



^alal^alYalnm - /^aYalnr (76) 



— 3J^=fBLrB -(^A + ^L)yiiver (77) 



dVK 



dt 



dybone 

 dt 



dyTB 



= fBKrB-(^A + XK)yK (78) 



= fBBNrB -(?^A + ^B)ybone (79) 



dt 



- fBTB^B - (^A + ^TBJYTB (80) 



where r, X, y, f, D, Am, and H^ are as defined in the ICRP II, Task Group, and SDB 

 models. The subscript URDL refers to transfer from URT to DL, BDL is from blood to 

 DL, DLTL is from DL to TLNM, BTL is from blood to TLNM, DLTR is from DL to 

 TLNR, DLAL is from DL to ALNM, and BAL is from blood to ALNM. 



Parameters for the above equations can be obtained from Fig. 7. Most of these values 

 are identical to those of the SDB model (Stuart, Dionne, and Bair, 1971). Our 

 modifications are designed to make the model more applicable to chronic inhalation and 

 to include ingestion and transfer of plutonium from blood to DL and from blood to the 

 lymph nodes. The value for the transfer from GIT to blood is identical to the ICRP II 

 value. The values for the other parameters are based on data reported by Ballou, Park, 

 and Morrow (1972) for the translocation of a soluble form of plutonium (plutonium 

 citrate) in dogs. Stuart, Dionne, and Bair (1971) recommended a variable half-time for 

 part of the transfer rate from the lungs to blood, but it was felt that a constant 3-yr 

 half-time for the entire lung was an adequate representation of their dog data. It was also 

 much easier to use the constant half-time for the mathematical description of chronic 

 inhalation. 



Like the SDB model, we assumed that 30% of the material initially deposited in URT 

 is rapidly transferred to DL. Since the short-term form of the SDB model transfers 99.7% 

 of the material in URT to GIT in a short time (8 min), the effective transfer from URT to 

 GIT is 69.79% (0.997 x 0.70). The corresponding transfer from URT to blood is 0.21% 

 (0.003 X 0.70). 



Model Comparisons 



The preceding models were compared by computing organ burdens and radiation doses 

 resulting from unit intakes by ingestion or inlialation. The units were either 1 /jCi as a 

 single intake or 1 juCi/day continuous intake, and the calculations were carried to 50 yr. 

 The resulting organ burdens and doses after 50 yr are given in Tables 10 and 1 1. 



Stuart, Dionne, and Bair (1971) (SDB) applied their model to single inhalations, and 

 the variable half-time in the pulmonary lung did not present any difficulty. However, 

 there is some doubt as to the interpretation of the variable half-time for the chronic case. 

 A strict interpretation would imply that a significant fraction (15%) of material 

 continuously deposited in the pulmonary lung is eliminated with a half-time that exceeds 



