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'NATURE VOL. 241' FEBRUARY 18 1973 ~ - - ~ ~ - ~ - ~ 446 -
<br /> la 2 Average lathudinal Distribut, of Cumulative Pu-239,240 o VOkhok, H. L., IEC Report HASL•127, 1 (1970).
<br /> T~ and Pu-238 Faudui Hardy E., and :y, P. W., Prue. Finbon. Platonium Symp.,
<br /> LA•4736 (1971).
<br /> ~ a 10 Chu, N. Y., Atm/. Chem., 43, 449 (1971).
<br /> mCi r k~ 238 t' Hardy, E. P., Krey, P. W., and Volehok, H. L., USAEC Report
<br /> H°~- lot' HASL-250 (1972).
<br /> sphere band° Pu-239,240 Weapons SNAP•9A Harley, J. H., Proc. Fmiron. P/uronium Symp., LA-0756 (1971).
<br /> plor[hern 80-7U (0.36±0.05) (0.009±0.001) (<0.001)
<br /> 70-60 1.6 ±1.0 0.038±0.025 0.026±0.015
<br /> 60-50 1.3 ±0.2 0.031±0.004 0.013±0.004
<br /> 50-40 2.2 ±0.5 0.053±0.011 0.026±0.011
<br /> 40-30 l.a ±0.6 o.oaz±o.ola o.ozs±o.ols EleCtroII Microscopy of
<br /> 30.20 0.96±0.07 0.0]3±0.002 O.oll±0.004
<br /> zo-lo o.za±o.lo 0.0o6±o.ao2 o.ao3+o.ooz MOIIOlIIO1CCU11I Layers
<br /> Io-o 0.13±0.06 o.ao3±o.001 <o.aol of Thorium Atoms
<br /> 5ou[hern 0.10 0.30±0.20 0.007±0.005 0.010±0.007
<br /> 10.20 0.18±0.05 0.004±0.001 0.036±0.021 LNACFS of heavy atoms in single molecules have recently been
<br /> 20.30 0.39±0.16 O.IXN±0.004 0.070±0.042 obtained with scanning transmission electron microscopes as
<br /> t 30--00 0.40±0.12 0.009±0.003 0.06]±0.020 well as conventional electron microscopes in both bright and
<br /> 40-50 0.35±0.21 0.008±0.003 0.069±0.038 dazk-field o ration[-`. Because of the random orientation
<br /> 50.60 (0.20±0.09) (0.005±0.002) (0.044±0.023) Pe
<br /> 60.10 (0.10±0.04) (0.002±0.001) (0.022±0.012) of isolated molecules on the specimen support, only a few of
<br /> 70-80 (0.03±0.01) (0.001 ±0.001) (0.008±0.005) them show the true interatomic distances in parallel projection.
<br /> 80.90 (0.01±0.004) (<0:0p1) (0.004±0.002) A)so molecules coWd stack ilteroselve during preparation.
<br /> Finally, the limited depth of focus of electron microsco
<br /> Results in parentheses were derived by extrapolation; error terns Ace at
<br /> are standard deviations. 100 kV when viewing atoms' makce it necessary to obtain a Hat
<br /> specunen.
<br /> slight rise in the Southern Hemisphere temperate zone which, To overcome these diflicultie it is aeccesary to prepaze
<br /> at its peak, is about one-fifth of the Northern Hemisphere monomoleculaz films 6-30 A thick. Such monolayers of atoms
<br /> maximum. The SNAP-9A Pu-238 has an entirely different can be formed on ligttid-air interfaces in Langmuir troughs
<br /> distribution pattern. Most of the SNAP debris has deposited and it is possible to obtain different molecular structures with
<br /> in the Southern Hemisphere where the maximum fallout is the molecule tagged with heavy atoms. For electron micro-
<br /> 2.5 times that in the Northern Hemisphere. -
<br /> Tabla3 Inventory of Pu-239,240 and Pu-238 Fallout ~ -
<br /> kCi deposited -
<br /> Pu-238
<br /> Pu-239,240 Weapons SNAP-9A - 1
<br />
<br /> - Northern Hemisphere 256±33 6.1±0.8 3.1±0.6 TE - ~0 Oi0~
<br /> Southern Hcmispbere 69±14 1.6±0.3 10.8±2.1
<br /> Global 325±36 7.7±0.9 13.9±21 ~ O/ 1" O ~
<br /> O O
<br /> ac• Q
<br /> The average and extrapolated activities per sgttare km fot
<br /> each ten degree latitude band were multiplied by the latitude ~i
<br /> band area to calculate the total deposit in kCi. Theo. values M
<br /> - were then surnmed to obtain the inventories in Table 3. The
<br /> errors were propagated by conventional means.
<br /> The total Pu-239 deposit was 326±36 kCi and the weapons
<br /> ' Pu-238, 7.1±0.9 kCi. Ottr estimate of the SNAP-9A Pu-238 " ~ ~ ` ~ ~ ~ '
<br /> deposit, 13.9±2.2 kCi, is in reasonable agrcement with the 10 ZO 30 40 50
<br /> 16 kCi we would expect to have fallen out based on the strato- ~ A2(molecule
<br /> . spheric inventory. Over 75°,0 of the total SNAP Pu-238 deposit
<br /> is in the Southern Hemisphere whereas only about 20% of the FYe• 1 Isotherm of thorium-bexafluoracetylacetonate at 3° C.
<br /> t total weapons Pu-238 fallout occurred in that hemisphere. P•o.c., Point of collapse.
<br /> This accidential release of Pu-238 almost tripled the global
<br /> deposit of this plutonium isotope by 1970. The distributions emtrast trmst'ar
<br /> and inventories of the weapons Pu-238 and Pu-239,240 are in
<br /> reasonable agreement with estimates based on Sr-90 deposition 10096
<br /> and Pu-239,240 to Sr-90 ratio measurements".
<br /> E. P. F txDV
<br /> P. W. Kaev 50%
<br /> H. L. Vo[,cttott
<br /> Health and Safety Laboratory,
<br /> US Atomic Energy Com»ursion, ~ y
<br /> .Vew York, New York 10014 t [
<br /> t t
<br /> Received October 3; revised November 3, 1972. • - - vv 3~G,~ '3f~:~
<br /> Finney, J. W., New York Times, May 24 (1964). v` i
<br /> ' Hazley, J. H., USAEC Report HASL-149, 138 (1964). ~ _
<br /> Korsrnayer, R B., Nuclear Safety,-S, 303 (Summer, 1964). ~%-~`~tv° fmttsler '
<br /> ` Krey, P. W., Science, 158, 169 (1967). IWIehOtt
<br /> a., ' Tekgadas, K., USAEC Report HASL-104, 1 (1969).
<br /> w ° Feely, H. W., Friend, J. P., Seitz, H., Martin, J. D, and Erlcback, Fig. 2 Phase contrast transfu functions for C,=1.32 mm, C.=
<br /> W. E., DASH 2/66-3, March (1971). 1.62 mm, 1L=0.037 A (100 kV) and Maxwellian velocity dis[ri-
<br /> r Kleittman, M. T., USAEC Report HASL-245, 1 p971). button at T=2,900 K.
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