54 5.1
A d d i t i o n a l Assumptions
Many of t h e b a s i c inc-remental p a r a m e t e r s used i n A I R D O S - I I
indi-
v i d u a l and p o p u l a t i o n d o s e estimates a r e c o n s e r v a t i v e ; t h a t i s , v a l u e s
a r e chosen t o maximize h y p o t h e s i z e d i n t a k e by man.
Many f a c t o r s t h a t
would r e d u c e t h e r a d i a t i o n d o s e , s u c h as s h i e l d i n g provided by d w e l l i n g s and t i m e s p e n t away from t h e r e f e r e n c e l o c a t i o n , a r e n o t c o n s i d e r e d . It i s assumed t h a t p e r s o n s remain unshi-elded a t t h e r e f e r e n c e l o c a t i o n
100% of t h e t i m e .
Moreover, i n e s t i m a t i n g t h e d o s e s t o maximally
exposed i n d i v i d u a l s v i a t h e i n g e s t i o n O E v e g e t a b l e s , b e e f , and mi.lk, a l l t h e food consumed by t h i s i n d i v i d u a l i s assurned t o b e produced a t
the reference location specified.
Thus t h e d o s e e s t i m a t e d f o r the
maximally exposed indivi.dua1 i n t h i s and o t h e r s t u d i e s u s i n g AIRDOS-I1 i s l i k e l y t o b e h i g h e r t h a n d o s e s t h a t would
OCCUK
i n a real-world
situation. A s p e c i a l case e x i s t s i n t h e methodology f o r t h e c a l c u l a t i o n of
d o s e from 220Rn which d e s e r v e s f u r t h e r e l a b o r a t i o n .
F o r p u r p o s e s of
t h i s r e p o r t , 220Rn g a s i s r e l e a s e d from f o u r l o c a t i o n s w i t h i n t h e mine-mill. complex:
the m i h e p r o p e r , t h e o r e s t o r a g e p i l e , the m i l l -
r e f i n e r y , and t h e t a i l i n g s beach.
I t w a s f u r t h e r assumed t h a t t h e
n e a r e s t r e s i d e n c e i s l o c a t e d no c l o s e r t h a n 1 m i l e from t h e s e f a c i l i t i e s , i n t h e d i r e c t i o n of t h e p r e v a i l i n g wind.
Given t h e s h o r t ha1.E-life
of
220Rn (55.6 s e c ) , w e c o n s e r v a t i v e l y assumed i n t h i s s t u d y t h a t a1.l
220Rn d e c a y s t o a i r b o r n e 212Pb p a r t i c u l a t e s p r i o r t o c r o s s i n g t h e 1 - m i l e f a c i l . i t y boundary. r'220Rn
+
D"
Doses l i s t e d i n t h e r e s u l t s as due t o
(220Rn + d a u g h t e r s ) a r e t h e r e f o r e a c t u a l l y t h e r e s u l t of
i n g e s t i o n and i n h a l a t i o n of 212Pb, f o r b o t h t h e maximally exposed i n d i v i d u a l s and t h e g e n e r a l p o p u l a t i o n s .
A s c o n f i r m a t i o n of t h e accu-
r a c y of t h i s approximation, d o s e s were i n d e p e n d e n t l y c a l c u l a t e d b o t h f o r 220Rn g a s a l o n e and f o r 212Pb suspended as d u s t ( r a t h e r t h a n c r e a t e d by decay of a i r b o r n e 220Rn) from the f o u r s i t e o p e r a t i o n s .
Doses c a l c u -
l a t e d f o r these cases were i n s i g n i f i c a n t i n comparison t o ' l a P b d o s e s g e n e r a t e d from a i r b o r n e 220Rn and w e r e excluded from t h e t a b u l a t e d results
.
A d d i t i o n a l l y , d o s e commitment t o t h e l u n g , as computed f o r t h i s r e p o r t v i a the I N R E X - I 1
code7, i s calcul.ated a s d o s e t o t h e e n t i r e