MODEL FOR ESTIMATING Pu TRANSPORT AND DOSE 507 



Estimation of Acceptable Soil Concentration 



The acceptable soil concentration (ASC) is defined as the average concentration of ^^^Pu 

 in the soil of an area occupied by the hypothetical Standard Man which would result in a 

 dose to the lungs equal to or less than the permissible dose. This value is estimated as 

 follows: 



^3^.(1.5/365) 



(E Yeq/m) 



= 2817pCi2^^Pu/gsoU 



where (1,5/365) = "permissible dose rate" (rem/day) 



E for 23^Pu = 51.2159 X 53 = 2714 (rem/day )/MCi, or 0.0027144 (rem/day )/pCi 

 m = 500 g for lung 

 Yeq = 0.002 Csy 



y = lung burden after 50 yr = 134.34 y£'\ per jLtCi inhaled per day (see 

 Table 1 1 ) 

 0.002 Cs = plutonium inhalation rate (pCi/day), i.e., 20 m^ air/day X 10~^ g 

 soil/m^ air, and Cs is the average soil concentration (pCi/g) 



Comparison of ASC and Soil Inventory Data 



Tables 1 and 2 summarize the mean soil concentrations and the estimated inventories of 

 2 3 9,2 4 0pjj -j^ jj^g surface soils (0- to 5-cm depth) at NTS. In each contaminated study 

 area, soil sampling was stratified according to contour intervals (strata) previously 

 established by field instrument tor the determination of low-energy radiation (FIDLER) 

 surveys. The pertinent results for Area 13 are given in Table 12. 



Only stratum 6 exceeds ASC = 2800 pCi/g, but stratum 5 is close enough to be 

 included in the contaminated region. Complete decontamination of strata 5 and 6(1.1% 



TABLE 1 2 Estimated Inventory of ^ ^ ^ -^ "* ^ Pu in 

 Surface Soil (0- to 5-cm Depth) in Area 13 



*l'rom Gilbert (1977, Table 1). 



fl-rom Gilbert (1977, Table 1). Mean ± standard error. 



jFrom Gilbert et al (1975, p. 393). Mean ± standard error. 



