—
Another report* indicates a beta to gamma ratio of 150 to 1 based
on theoretical computations.
A third report** suggests a radically
lower ratio: however, there may be some doubt as to its conclusions
since the ionization chamber used to measure gammas only, had a wall
thickness 2£ 1 mm cf bakelite which "...excluded a small part of the
total gamma dose present, as well as a lerge, but unknown, fraction of
the beta."
(The range of 0.35 Mev betas is about 100 mp/em” or approx-
imately 1 mm of bakelite.)
For our discussion here, we will assume a
Surface beta to gamma ratio of 150 to 1.
In estimating the beta dose to the basal layer of the epidermis,
one may refer to the work of Henriques***,
He exposed the skin of
Chester White pigs to plaques containing different radioisotopes.
Pertinent dats are abstracted as follows:
Asoione
Yttrium?+
Strontium’20
Yttrium?
Energy
-
Surface Dose Required To Produce
Recognizable Transepidermal
Injury (Roentgen-equivalent=
eta)
1.53
0.61
2.20)
Estimated Amount of
Radiation That Pens—
trated Skin To A Depth
. of 0,09 mm, (red)
2,500
1,200
1,500
1,400
The average maximum energy of the beta particles from fallout mater-
jal varies with time but will be assumed to be roughly comparable, in
5
respect to depth dose, to Yttrium’ or Sr?0-y%,
Since the gamma dose
at a depth of 7 me/om” would not be significantly different from the
surface gamma dose, the ratio of 130 to 1 for beta-gamma will be assumed
at the basel layer of the epidermis,
*"An Estimste of the Relative Eazard of Beta and Gamma Radiation from
Fission Products".
Sullivan, Williem H., NRDL.
April 1949.
CONFIDENTIAL.
**UKP=37. Project 4.7. "Gamma-beta Ratio in the Post-shot Contaminated
Area". June 1953. CONFIDENTIAL-RESTRICTED DATA.
ee¥UEffect of Beta Rays on the Skin As A Function of the Energy, Intensity,
and Durationof Radiation".
war A
Henriques, F.W.
Laboratory Investigation.
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