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AOQLEP
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UNIVERSITY OF WASHINGTON
APPLIED FISHERIES LABORATORY
FISHERIES CENTER
SEATTLE 5, WASHINGTON
January 11, 1957
Ale? ¢
NS
Dr. Allyn H. Seymour
Marine Biologist, Biology Department
Division of Biology and Medicine
U.S. Atomic Energy Commission
1901 Constitution Avenue N.W.
Washington 25, D.C.
Dear Al:
During a conversation while Ed and I were in Washington
last month, you mentioned that the activity levels in the
water at Rongelap were higher in July 1956 than the levels
reported in UWFL-43 obtained at earlier visits.
Ed has
looked up the data and summarized it.
The best evidence seems to indicate that the increase
noted in the July 1956 samples is due to the recontamination
of Rongelap from the 1956 series of weapons tests.
The decay
of the newly added radioactivity is such that it will soon
be insignificant when compared with that from the 1954 series.
The decay of activity of the particulate matter and the
filtrate of a cistern water and a lagoon water sample col-
lected at Rongelap Island in July 1956 was followed.
Although
the counting error is too large to permit a precise evaluation
of the decay rate, it is clear that the half life immediately
after August 22 (first counting date) was between 20 and 40
days,
indicating the presence of short half-life radionuclides.
The count of January 1957 resulted in values which compare to
those found in October 1956 and reported in UWFL-43, Table 13,
as follows (values in d/m/liter):
Collection Date
Oct. '55
July '56
July '56
Counting Date
Oct.
Aug.
Jan.
Cistern water
particulate matter
+
75-17
Cistern water
'55
390117
+
filtrate
+
310-190
110-73
910+t100
Lagoon water
+
particulate matter
Lagoon water
9002155
filtrate
fo
bo
LRD:gb
‘
'56
140-12
+
.
60-120
a
‘
+
2ho00te10
2000200
+
91-10
+
64-80
+
24-9
Lauren Rn
naldson
QO175
240t165
Sincerel 1Sassteh Brratden/
Director
'57