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measurements at a height of three feet.
Past field experience has indicated
that the gamma reading from lonisstion-type survey meters at ground level
{s ebout 50% higher than at three feet,
Therefore if it be assuzed that
@ grount level gama reading of a survey neter is equivalent to a surface
Gone rate, the ratio of beta dose rate at 7 xg/en* to ganna dose rate at
Shree is about 200 to 1.
Aoother approach to estizating the ratio of beta dose rate at 7 xg/ex*
to gamxa dose rate at three fect is as follows,
Assuzing a mifora distri-
bation of 1.0 megacurie per square rile of gamma activity, the dose rate
reeding from an infinite field is about 4.1 roentgens/bour.® Caloulations
given in appendix B indicate that a liks eoncentration of fallout naterial
will produce about 430 reps/hour at 7 mg/cm®, This suggests a beta to
gama ratio of about 100 to 1 which is about a factor of two lover than
the first approach. Added support to this latter method of estinating
beta doses is found in appendix ¢,
Such eonsiderations may be franght with pitfalls.
For exemple, the
above discussion implies « uniforz distribution of falbut material, Obriously,
this is not correct tut how far this deviates from the facts and to what
extent this influences the results is
difficult to assess.
indioate that the production of recognisable beta burns
particle requires a high specifie activity.
Caleulations
fros a single
(See Policy III for discussion.)
It msy/oe,hovever, that the particles of fallout are €lose enough to have
overlapping of radiation fields and thus require significantly lover
specific activity of the particles to produce beta burns.
**Effects of Atomic
Weapons",
This hypothesis
1950
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