254. SN Mivace ~.. 7s aca K Kameda Vol Vo No. 3~4 hydroxide solution .o4 38 cutefu... ‘’opoed in with a pipet until a faint pink After two mirutes iling tne precipitate is settled on standing colour appeare for a ccuple f aeurs at room temperatue Uae precipitate = Sltered ander suction on. guund oR filter paper o.4 . em faving wbeve * © glass filter ‘Fig 3° Tne precipitate “evudined on 4 filter paper.s dried in an air bath: 1 a jesiccator holding on a -1rall brass case Fig 20 ' 0 avoid tne folding ft ‘he surface Vieasurerents of radioactivitV are done by puttiig tre pre pitate kept in a brass case under ao ond sirduw of G-M counter The GM counter used aboard WoT Lo? ’ 1 the © Shunkortotsu-maru" 1s Radiation « ounter, Model 32 Institute manufactured hy Ltd. Tokyo. science __ oetween ale € } materials fell abuard the fishingry hye beat the Pherefore, the actual ‘ : Fusxu- ay = the mica window and the surface ‘f the precip- ryu-maru _ kKesearch itate as 15 -m After the measurement ‘as been dene. tre precipitate 1s covered os a poly. ethylene filr: tu protect the surface “t was confirmed thar at least *O~-sv if toe total . .in sea : . it,be transfered anet activity water could to ‘ ‘he precipitate by preliminary tests using the fss un ) ‘ i =F “TT = i ——— The tnickness of mca window :3 3.° mgcm? and the distance . wy! I ' Fig 1. _ y fo a * | .\ a LEoe The apparatus for filtration. activities might be 25~40 higher than opserved .alues. To obtain the « ounting efficiency the aqueous solution containing Ce 144 of «hich activity had been referred to the - Sag O § Dia Jam ° o 9 9 ®5 “ 9 : Precipitate SEP 4gmn o NY . Fig. 2. . me —- jG MM-— | LAP A smail brass case tu avoid tne folding of the surface of a filter paper. rN standard RaE was treated chemically as ‘nentioned above, and its radioactivity was measured under the same geometrical conditions. Thus, the efficiency of the measurement was found to be 7 7%, that is, 1000 counts per minute is equivalent to about 59m ,d’. The maximum activity in sea water obtained aboard by thie method was 7025cpm/ which Bikini Atoll on 21st June. was found at the depth of 75m, at 450km west of The second was 6050 cpm./ found at the depth of 20m at 150km west of the atoll on 12th June. were dispersed in It was confirmed that most parts of the radioactive materials water as tme solutions, ionic or eucolloidal, since more than aa 2¥