health and safety laboratory - Digital Collections

I
1 I
f
I
1 I
I
t I
I
1
These data were reported by Eisenbud and Harley
(8)
covering fallout
through June 1957, The model was applied only to the results obtained after
May 1956.
Unfortunately, later calculations have cast doubt on the validity of
the effective burst date concept and actual errors of computation have been
uncovered. The present model was designed to overcome some of the objections
to the previous one. All of the data since the beginning of 1954 have been
recomputed according to this third model.
It would have been technically possible to introduce a number of ex
perimentally determined refinements into the model, but the cost of compu
tation for some 375,000 pieces of data would have been prohibitive. .There
fore, the relatively simple model described had to be accepted.
The Computation Model
The present model was designed to take into account new data on Sr
Qn
7U
yield, -stratospheric and tropospheric residence times and the decay of Sr^.
The model will first be outlined and then its defects will be discussed.
1. An estimate of the fission yield is obtained for each weapon test.
2. The value of 133 megacuries of beta activity per nominal bomV
(9)
is used to obtain total megacuries of fission products at one day.
1^ QA
3* The value of 0.00105 percent of Sr^u is used to obtain total
megacuries of Sr at one day
4- The megacuries of mixed fission products produced in each test
are decayed by the T"^*2 law for each subsequent day and the resuits
for all tests .summed.
I
5. The megacuries of Sr^ produced in each test are decayed with a
half-life of 27.7 years for each subsequent day and the results
for all tests summed.
1
6. Both the mixed fission products and Sr are also corrected for
tropospheric ( < 3/4 MF) and stratospheric ( > 3/4 MT) deposition
using half-residence times of 20 days and 4 years respectively.