DNA 1240H-2
In the theoretical method developed at NEDL, it was found possible
to express the results of Goldstein and Wilkins©* for the dose buildup
factor, B, of Equation 17-13 for any given medium and quantum energy,
expression of the form given in Equation 17-19 of 17.5.5:
B -| 1+ a(pux} + b(we)?]er(ux)
by an
(17-19)
The constants a, b, and c can be related to quantum energy E and
evaluated for various media.
Further,
since the expression for the
buildup factor is analytic, it ie possible to integrate Eq. 17-13 over
& source region.
The integrated expreesion for dose rate due to sources
distributed over the top of a circular slab of radius Ry is given in
Ref.55.
For simplicity and abbreviation of notation, the integral form
wili be employed in this discussion.
The ship-shielding factor for deposit radiation is evaluated by using
three dose-rate ratios similar to those used to calculate the shielding
factor for transit radiation:
dhR
Shoe
dn
43R
SF agp" }do * Theol * do
(17-30)
where dip = exposure dose rate (at a given below-decke location)
Gue to activity deposited on the weather-deck of the
ship.
Q3R = exposure dose rate at 3 ft above the weather-deck,
over the below-decks location.
Gnoo = exposure dose rate at a location considered to be a
given distance below an infinite slab of shielding,
with radioactive sources distributed uniformly over
the top surface of the slab.
a," 8 symbolic dose-rate measure of source strength.
For the plane source case, @, has the units r/hr.
It is e quantity
equivalent to that given by Eq.17-14 or Eq.17-17 of Section 17.5.5, but with
ann whose units are photons/cm@ - sec.
See Note after Eq. 17-17, and
footnote after Equation 17-24 of Section 17.6.4.
Since the individual dose rates on the right hand eide of Eq.17- 30
are initially unknown, it was found possible to obtain the desired
shielding factor by substituting equivalent ratios into the calculations.
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17-82