Fallout Measurements by Aircraft and Rocket Sampling (Hardtack Operation, Project 2.8, Draft) (Deleted)

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FALIQUT ]tiASU~151JTS BY AIRCR~ AND ROCKET SMIPLIIG San Francisco 24$ California CLASSIFICATION CA NC ELLED

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The primary objective of the project was to estimate the partition of range nuclear detonations over land and v’ater surfaces. A secondary objective WZLS to determine the spatial distribution of radioactivity particles) ~ the ~uclear clouds a few minutes after stabilization. planned to achieve these objectives bY ra~ochemical analyses and size measurements on the following t~-pes of samples: 1. Samples of the particles and radioact~ve gases present in the upper portions of the clouds to be collected by high flying aircraft. 2. Samples of the particulate matter in the clouds to be collected along nearly vertical flight paths , ~.t several different distances from the cloud axis, by rocket-propelled sampling devices. 3. Samples of the fallout to be collected at an altitude of 1, 000 feet by lov.’-flying airc raft. The project participated in a megaton shot (Koa) fired over = coral shot (Oak) fired over a coral reef in SE, ZI1OWwater. The aircraft sampling program was generally successfd, and fairly complete sets of both cloud and fallout samples were collected on each shot. The rocket program was unsuccessful due to a variety of eotip,ment malfunctions.

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gas samples were analyzed for radioactive ~tmn and the cloud and information on fractionation. Fall rate and size distribution rneas~e- - ments were ~de” on the particle smple9 from the land surface shot. me cmbinod the local and long-range fallout. There are no resdts to k repor~d on the spatial distribution of radioactivity in the clouds since this put of the project wa5 dependent, on the rocket total clouds that indicate~if the layers sampled were representative of the” responding figures for a dispersed over distances greater than 4,000 miles. COP coral land surface are or=–fifth for Sr ad one-half for tion varied froa layer to l~er, in t,he lad surface shot. ‘l’he 10d fmout was depleted in both Sr 90 and C~37 and the up~r portions of the clouds were enriched. Fractionation -.-a.s much less fGr the water shot. It is recc:-.~ended that a siuu31ar project, with a more detziled analysis of rafionuclide distributions k incluckd as part of the prog:am if future i::aFIons

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In the formulation of this project, three distinct parts were established: rocket fallout sampling, aircraft fallout sampling and sample analysis, data interpretation and report preparation. Responsibility for the conduct of rocket sampling was assigned to the University of California Radiation Laboratory (U CR L); responsibility for the conduct of the aircraft sampling sponsibility for the conduct of sample analysis, report writing, etc. , was assigned to the U.S. Naval Radiological Defense Laboratory (NRDL). The as technical advisor to the project officer, was responsible for the conduct LASL portion, E. H. Fleming acted in a similar capacity for the portion and N. E. Ballou and T. Triffet are responsible for the

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The authors wish to acknowledge the vital contributions made to the Project, in both the field and the laboratory, by members of the LOS Alamos Scientific Laboratory, the university of California-Radiation Laboratory, and the U.S. Naval Radiological Defense Laboratory. and H, P]ank from the LOS Alamos Scientific Laboratory; R. Batzelt Stevenson, and K. Street from the University of California Lawrence Radiological Defense Laboratory.

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TABLE OF CONTENTS Formation and h’ature of Procedures for the Determination of Fallout Partition - 1. 3.3 -Aircraft Sampling of Clouds . 2. 1 Shot Partici Pzti G.q ........

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Discussion of Some Errors in Sampling . Description of Field Operations .......

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RADIOCHEMICAL DATA TABLES ........... PARTICLE DATA AND CHARACTERISTICS, SHOT KOA . METEOROLOGICAL DATA TABLES ......... Intake and Filter Section, B-57 Gas Sampler .....l.l Pumps and Gas Bottles, B-57 Gas Samplers ....l.wl Plan View I$rind Velocity Hodograph, Shot Koa .......l Plan View 1}’ind Velocity Hodogiaph, Shot Walnut ....... Particle-Gas Fission Ratios as a Function of Time for Samples Fraction of Total Sr9° Formed I’,fiich Remains Aloft at Various Fraction of Total Cs Formed Which Remains Aloft at Var\ous Diagram to Illustrate Rocket Programming ......... Particle Fall Rate Distribution Curves for Height Line Samples, Particle FalI Rate Distribution and Specific Activity Curves for Particle Fall Rate Distribution and Specific Activity Cuives for

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C.4 Particle Fall Rate Distribution and for Cloud Samples, Shot Koa: Sample C.5 Particle Fall Rate Distribution and for Cloud Samples, Shot Koa: s~ple c.6 Particle Fall Rate Distribution and for Cloud Samples, Shot Koa: Sample C.7 Particle Fall Rate Distribution and for Cloud Samples, Shot Koa: Sample C.8 Particle Fall Rate Distribution and for Cloud Samples, Shot Koa: Sample for Cloud Samples, Shot Koa: Sample C.1O Particle Size Distribution Curves for Height Ltie S&apless— C.1.l Particle Size Distribution Curves for Cloud samples, Shot Koa: Samples 502, Coarse, andS02, Fine ............. C.12 Particle Size Distribution Curves for Cloud Samples, Shot C.13 Particle Size Distribution Curves for Cloud Samples, Shot Koa: Sa-mples 977, Coarse, and 9779 Fine ............. Particle4as Fission Ratios and R-Values for Samples from Percent of Nuclides Left in Cloud after One Day ........l Comparison of Airborne and Deposited Fractions. ........l Radiotungsten Analyses on Koa Cloud Samples. .......... Raciiochemical Data, Koa Farticulate Samples ........... Raciiochemical Data, Koa Gas Sariples ..............l Eadiochemical Data, Oak Particulate Samples ..........l

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Winds Aloft Dzta, Shot walnut ..............l 130 Atmospheric Temperature Data, Shot Koa .......clo 132 Atmospheric Temperature Data, Shot Walnut ......lll 133 Atmospheric Temperature Data, Shot @.k .......lll 134

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The general objective of the project was to estimate, from analytical data on cloud sarr.pies, the relative distribution of certain radionuclides tions on land and water surfaces, wiih pa-rtimkr enp~.asis on the distribution of Specific objectives were to: (1) ob~in airborne particle and gas samples by rocket and aircraft ~amp~ing tec~ques; (2) determ~e the distribution Of radionuclides between two groups of particles which differed from one another in their fauing rates ,> <r and which could be considered representative of the cloud at ~-zrious times fo?lowhg the shots. Data ori the geographical distribution of fallout are pzrticwlarly needed to assess the global kaz~rds a~soziated with the testing of nuc~ear weapons,

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but they are also used in warfare. important for an appraisal of the effects of nuclear weapons It has been recognized since the earliest weapons tests that a substantial portion of the radionuclidcs formed ti a nuclear detonation are deposited throughout the v~orld, thereby becoming available for general biological assimilation. The total fallout is usually considered as being divided into ISVO classes$ designated as 10CZ1 and world+vide fallout. b a general ways local fallout is thought of as consisting of relatively large particles, which reach the carth~s surface in a few hours, whereas world wide fall Gut is composed of fine~y-divided m~terizl which may remain .SU5pcn~ed in the atmosphere for months or years and be deposited at long distances from the source. A more precise differ cntiztion is nccdcd for “ specific situations , one of the most import=t considerations being the loca - tion of the detonation site in relation to world centers of population. cxp~osions at the Pacific Proving Grounds, the boundary between the classes has been chosen at a particle falling velocity of 3 rn~.teri~l settling out more slowly than this is likely to be the ocean arezs and deposited in inh~bitcd regions~ Li it The ratio of local to world-wide fallout is/governed by ill: kighz at~-~ed b t,y,i=Jnuclear cloud and the size ciistribuiion /of the p~rticles in the nuclear cloud which act as collectors for the radioactive fissio=product atoms. If many Iargc particles with fast falling

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rates arc present, as is the case for surface or underground shots where the fireball contacts the ground, tbe local fallout will be large. Local fallout can - be expected to decrease as the detonation height increa8es and become a negligible quantity for an air burst high above the ground. Numerous estimates of local fallout have been prepared at previous Operations, main Iy from analyses of radiation intensity data obtained in aerial and surface monitoring surveys. However, the uncertainties in converting from dose rate measurements to fi5sion products deposited per unit area are so great that the results cannot be regarded with a great deal of confidence. More reIiable valucs are cvidcntiy needed and in planning for operation HARDTACK, the AEC =Xamin=d possible WaYs of obtaining such information (Reference I). After consideration of the difficulties inherent in additional refinement of surface measurement techniques, this approach was abandoned. An alternative program based on further development of existing cloud sampling procedures was formulated {Reference 2) and this culminated in Project 2.8. A knowledge of fallout partition and how it is influenced by shot environment may contribute to reduction in world-wide fallout at future tests and to a better understanding of the military implications of local fallout. It wiI1 aIso assist in extrapolation to previously untried shot conditions and yields.

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1.2. 1 Formation and Nature of Fallout l%rticles. When a surface burst is deto~ted, great quantifies of the adjacent environment arc swept upxd mixed with the incan~esc~nt air in the fireballq There is s~ficient the immed~zt= v~ctnity, but the fIOSV Cf heat into a massive object, such as a shot tower, shield or coral rockO wi 11 be cornparztively slow even with a high temperature gradiente Conse~&exztIy, the i9.tericr portions of large structures in the ~~;.g~~~rhood my not receive e~cugh heat to evaporate

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fusion and with solid pzrticlcso The radlonuclide atoms present will collide frequently with oxygen or free radionu -

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The isobaric radionuclide chains formed b the explosion arc known to be distributed on a mass scale in a way generaIXy simiIar to the pro235 by thermal neutrons,ducts of asymmetric fission of U but with some important diffe”rcnces. The experimental yield curve for slow neutron fission has a broad minimum for mass numbers approximately one-half that of the original nucleus and maxima on either side at mass numbers in the neighborhood of 95 and 139 (Reference 7)0 Comparing the chain yields for megaton-range detonations with this curve, it is noted that there is a small drop in the peak yields accompanied by an increase in the sW - metric fission probability. The same nuclide ‘distribution might be cxpectcd in the fallout material and this is found to be roughly true under with respect to #one another so that samples of fallout may differ in composition among themselves and also from the distribution curve characteristic for Fractionation is a term which has been applied to this phenomenon and it is used to signify an alteration in nuclicie composition of some portion of the debris which renders it non-representative of the bomb products as a whole. The R-values, which are commonly used for reporting rad.iochcmi - cal data on cloud and fallout samples, are useful indices of fractionation. The R-value for any nuclide is defined as the ratio of the number of atoms

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of this nuclide to the number of atoms of a reference substance (u Eually M099) in the sample divided by the same ratio for the products of thermal neutron fission/ Atoms which do not separate from the reference 9ub - stance have Il.-values appropriate for the type of detonation, while cnrichment or depletion are manifested by positive or negative deviations from the characteristic value. Knowledge of the causes and mechanism of fractionation is still largely incomplete at the present time. One effect that seems to be indicated by the available data may occur ~ the isobaric chains near mass numbers 90 and 140 which contain rare ga5 nu~~ides as prominent chain members. These have half-lives and independent fission yields such that they comprise a considerable fraction of the total chain yield during the period when the environmental material is condensing. H the rare gas atoms which collide with the liqfid drops of cntironmental material are not held by strong forces, as appears probable, t“he particles formed at this stage will be depleted in the nuclide chains in question, A var’iety of types of particIes have been observed in the local fallout at previous test series (References 5,9,10,119 12, 13). For land surface shots in the Pacific they have been mainly of three kinds: irregular grains, spherical solids ~nd fragile agglomerated flakes. The grains were not, in general , uniform throughout, but consiGted of layers or shells of calcium

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oxide,. calcium hydroxide and calcium carbonate formed by the decarbo - nation, hydration and recarbonati~n processes going on in the fireball and subsequently. The majority of them were white or transparent but some were yellow or brown. Many of the flaky aggregates were observed to disintegrate spontaneously into sma~er particles within a few hours In addition to these primary types, a fourth kind was noted consisting of small black spheres of calcium iron oxide (2 CaO* Fe203). These were usually observed adhering to the surfaces of the large grains For detonations over ocean surfaces the fallout collected consisted of droplets of salt slurry 50-300 microns in diameter. These contained about 80~o salt, 187’o water and 2% insoluble solids by volume. The =jor part of the radioactivity WaS found in the insoluble solids portion. The fallout deposited at more distant points has not been as well characterized, but is believed to be composed of minute spheres formed by condensation of the environmental material from the vapor plus a very fines mrused dust swept up into the cloud from the area around the shot The availability of the radioactivity in the fallout for assimilation into the biosphere depends to a large extent on its volubility in aqueous

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or slightly acid media. Determi.n+tion of the soluble fraction is therefore ~ that the solublm fraction Wag strong~ &pen&nt on the &tonat.ion environment, (Reference 15). The volubility in seawater of the fallout placed on top of a glass wool COIWUI ad by centrifuging a from the reef shot leaching of particles suspension of the fallout matirial (Reference 13). The soluble fractions found by these two msthoh ~tiere 0.08 and O. IX, respectively. An ultrafiltration method was used for deterr~~ the solubflity of fallout from the land shot, Zuni. About 25 per cent of the total g~ activity was soluble in rainwatir. Recent hves tigations (Reference 60) have shown that biological avail abfity is an>logous to volubility in 1 N HC1. Bomb debris from large tests is 99 per KU Cloud Ikvelo~ent. During the latei st~es of existence of the fireball, it is t~~sfo~ed into a vor~ ring -,{hose rotationa velocity persists up b the maxirum cloud altitude, at least for the larger shots. The vortex titles are ge~ra~ted. ‘The cloud continues b rise until its buoyancy is reduced ta zero by adiabatic exp2n5ion, entrainment

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of cold alr and loss of energy in overcoming atmospheric drag (References 16, 17, 18). The diameter of the ring increases rapidly during tie ascent - and the cloud spreads out laterally to a large arc~ as its upward velocity decreases. For smaller fields the cloud stops at tbe tropopause or bc - IOW. but for megaton-range weapons the top may penetrate several tiousaD,d feet into the stratosphere. The time to maximum altitude is some - what less than ten stabilized cloud is of the distribution of activity and particles …