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currents as a fumction of time.
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Such meesurements of. mixed fission
products do not give reliable estimates of Sr-90 in sea water since
the fission products may be fractionatedby solubility, precipitation,
and sedimentation.
Mixed fission products insea water are concentrated by coprecipitation of the majarity of the isotopes with verious carriers
such as iron hydroxide or calcium carbonate.
The activity levels of
interest ere high enough so that conventional counting equipment can be
used for measuren@mt.
Extention of the sensitivity by measurement
with low background couters would prabably not he justified in terms
of the overell accuracy of the determination.
Feiout Collections in Open Pots
Stainless steel pots, with a fece area of about one square foot,
ere finding increasing application in fallout sampling.
Other types
of vessels heve been tried and are currently used insome parts of the
monitoring program in this country and abroed.
The collected precipi-
tation and dust can be analyzed for Sr-90 at intervels, usuelly on ea
monthly besis.
In sharp contrest to the soil samples, the residues
subnitted to analysis are essentielly free of non-radioactive meterial.
The monthly increnent in fallout is readily. determined from these
samples, while it is only feesible to measure annual increments in
soil samples.
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The enelysis of pot collections requires the seperatian of Sr-90
from the smell emounts of inert meterial end from other_isotopes of
mixed fission products.
The deposition of naturally occurring radio-
isotopes during a month is negligible.
The levels currently found ere
such thet low background counting equirment is reauired for satisfactory
enelysis.
DOE ARCHIVES
G&/