RMI Nuclear Justice Documents

/
!/
L“

IMP CONVERSION FACTOR DERIVATION
410161

Detector

Air
Soi1

z’
4

i

Source
Element

x

Unscattered flux at height h given by

/

[lJ/p

s“

exp -

w

,/

)
a

Par

a+v/ps
)

P~

r~j’

21TX dx dz

1
(1)

where
s“

=

activity per unit volume

r

=

ra

+

‘/p)a, ‘/P);

rs
=

air and soil mass attenuation coefficients
cm2
(—
!3)

Pa9

Ps

=

air and soil density (g/cm3)

Assume an exponential source distribution
sv = s~e
-.

‘az

(2)

where
s: = activity per unit volume at the sudface (~)

a = reciprocal of the relaxation depth (cm-’)
Rewrite Eq.1 in terms of ~and
integrate over z.

Leads to

z, combine with Eq.2 and