refer to cpm recorded by the scintillation counter while the probe was
exposed in air,
C.
JAPANESE DECONTAMINATION PROCEDURES and Radiation Readings
A review of the data given to us by the ship‘’s Captain shows that
the TAKUYO ran through a rain squall) between 2000 and 2300 hours, Japanese
Standard Time, 14 July 1958 (position 153945! E and 12923' N), Starting
at 1200 hours JST, the background (using their figure of 2400 cpm)
gradually began to rise.
At 2200 hours, following the rain squall, a
reading of 37,468 cpm, using the scintillation counter probe, was obtained.
However, the probe itself was found to be contaminated, and,
after being decontaminated by washing with a detergent (ethylene diamine
tetra acetate (E.D.T.A.), their "neutrality cleanser") and rinsing with
fresh water, the maximum count was 26,235.
37,468 cpm is equivalent to
0.31 mr/hr (using their figures of 500 cpm = 0.7 mr/week).
All Japanese
readings were taken with the scintillation probe close to the surface of
the deck,
Between 0100 and 0400 hours, JST, 15 July, the radiation level re-
mained at about 23,000 cpm.
On advice from Tokyo, decontamination pro-
cedures were commenced at about 0530 hours, 15 July.
Decks and equipment
were washed with "neutrality cleanser" and flushed with either fresh or
sea water.
Generally, the level was reduced to about 10,000 cpm by this
procedure,
The bridge and bridge deck remained "high", however, and decon-
tamination. of this area was repeated at 1400 hours.
This reduced the
reading on the bridge to 17,470 cpm.
On the morning of 16 July,
cleaning and washing of the inner parts
of the ship was accomplished and measurements made daily, thereafter.
2h yey
Pees See
CGRFIBENTIAY
DOE ARCHIVES
24