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Monday, January 22, 2018

The January 1955 secret Fallout symposium of the AFSWP, the first analysis of the detailed data on fallout from Operation Castle, is now available on the internet archive, thanks to the Nuclear Testing Archive

Thank you to Martha DeMarre of the Nuclear Testing Archive, Mission Support and Test Services (MSTS), Contractor for the Nevada National Security Site of the Uncle Sam, for today emailing me a scan in two parts of the terrific (formerly) secret January 1955 AFSWP Fall-Out Symposium, U.S. Armed Forces Special Weapons project report AFSWP-895, which I've put on internet archive (link is here).  This is the first major analysis (566 pages in its declassified form) of data from Operation Castle on fallout, the first major fallout hazard experience to be documented in great detail in 1954! The report was listed but a PDF was not previously available on the U.S. Department of Energy Opennet site (which currently highlights Edward Teller's dismissal of secrecy delusions in the PDF linked here).  Secrecy is damaging, as mentioned in the previous post on this blog, because it keeps the public uninformed of the key technical arguments that underpin scientific controversies, allowing abusive propaganda from bigoted, ranting communist lunatics to become "mainstream dogma", accepted by deluded, elitist pseudo-socialists as occurred after Darwin's cousin Sir Francis Galton used "authority" to push eugenics pseudo-science with a pipe dream camouflage of utopia.

AFSWP895 1955 Fallout Symposium secret, front cover.

AFSWP 895 fallout dose rates at 1 hour after the 14.8 megatons surface burst Castle Bravo across Bikini Atoll, 1 March 1954.  BEWARE OF THE MAP SCALE LABELLED "NAUTICAL MILES": this map and others in the series, reproduced in the 1956 weapon test report WT-915 and then in the fallout patterns compendium DASA-1251, exaggerates the size of Bikini Atoll considerably and needs correction (as we have pointed out in previous posts concerning DASA-1251 and WT-915).

AFSWP 895 fallout outdoor unshielded dose rates and doses after 14.8 megaton Castle Bravo across Bikini Atoll (ground zero is the reef to the immediate West of "Charlie" Island).  Upper number is dose rate, lower is accumulated dose from fallout arrival time to infinity, outdoors and without any shielding such as buildings or other shelter.


AFSWP 895 fractionation of Sr89 and Ce144 as function of fallout particle diameter in Operation Castle shot Bravo.

The report also contains new photos of the fireball and cloud from the 13.5 megaton Yankee shot of Operation Castle, taken from an RB-36, including the times of each photo (which is very useful, because it shows you the evolution of the fireball into the mushroom), at pages 91-110.  On pages 110-121 there is an excellent summary of the fallout study results of the Nevada 1.2 kiloton surface burst and shallow subsurface (earth penetrator warhead simulation) bursts Sugar and Uncle, respectively, from 1951, including photos of the differences in the nature of the fallout, comparing this data to photos of fallout from the 1952 Ivy-Mike surface burst of 10.4 megatons at Eniwetok Atoll.

On pages 123-138 there is a nice paper by Dr Carl F. Miller, called "Physical and Chemical Nature of the Contaminant: Interpretation of Castle Observations", giving the fallout deposited mass per unit area for specific time radiation dose rates, the averaged gamma ray energy, graphs of decay rates, and detailed tables of fallout solubility (ionic fraction of radioactivity when the fallout is mixed with water), comparing land and surface tests of Operation Castle.

On pages 139-153 there is an interesting paper by Dr Chris S. Cook, called "Radiological Nature of the Contaminant: Source Gamma Energy Spectra", giving data on the fallout gamma ray spectra determined using a sodium iodide scintillation crystal and a photomultiplier tube (the scintillation or flash brightness is proportional to the energy of the gamma ray, so with a pulse height discriminator circuit you can determine the spectrum).  This is vital because the penetrating power of the gamma rays from fallout determines the protective factor of a fallout shelter, and the production of low energy gamma emitters in fallout, particularly neptunium-239 and uranium-237 (produced by the capture of a high energy neutron, above about 1 MeV, by U-238, followed by the ejection of two neutrons, i.e. a so-called n,2n reaction) reduces the danger in the fallout sheltering period of 1-14 days after a dirty bomb (with a uranium jacket on the fusion stage).  Cook reports on page 139:

"Prior to 10 days following the detonation, a large fraction of the radiations are concentrated in the vicinity of 100 kev [0.1 Mev]".

This approximately 0.1 Mev radiation is the neutron activated U-237 and Np-239 (the time of peak percentage contribution of a nuclide to T^{1.2} fallout decay is equal to the half life multiplied by 1.2/ln 2 which is a multiplication factor of 1.44).  The best data available from Castle on this was from Union, shot 4, a water surface burst.  (However, excellent gamma spectrum data was obtained from land surface burst Zuni in 1956, reported in WT-1317 and related papers.)

AFSWP 895 fractionation of Sr89 Ba140 and Mo99 as function of fallout particle diameter in Operation Castle.  Note that Mo-99 is normally unfractionated since it is refractory (has a high melting point), whereas the gaseous precursors in the decay chains of strontium and barium make them effectively volatile, so they don't condense very effectively on fast-falling particles of early fallout.  This graph gives data from samples collected at 18.5 statute miles from ground zero (97,730 feet).

AFSWP 895 measured percentage of fallout radioactivity deposited within 24 hours as a function of scaled nuclear burst altitude. The scaling procedure is to divide the actual height of burst into the cube-root of the weapon yield (i.e. 10 for 1000 kilotons).

AFSWP 895 radioactive torus or toroidal circulation inside rising fireball from a 30 kiloton nuclear weapon at 1 minute, taken from Dr Kellogg's presentation (he gave an unclassified version, omitting this data on the measured speeds in the vortex, to the unclassified May 1957 congressional hearings on The Nature of Radioactive Fallout and Its Effects on Man).
AFSWP 895 Dr Kellogg's illustration showing why the cloud top heights were inaccurately measured and reported in early tests like Mike.

AFSWP 895 fallout from 1953 Nevada nuclear test Badger of Operation Upshot Knothole showing paths of fallout at different altitudes in the mushroom cloud: because the winds have different speeds and directions at different altitudes, there the cloud separates accordingly and fallout is distributed over a larger area than would be the case without this wind shear.  This diffusion of fallout spreads the same total amount of radioactivity over a greater area, reducing doses and dose rates to lower levels than simplistic predictions (the classic cigar shaped fallout pattern) indicate.
AFSWP 895 fallout distribution in the mushroom head and in the stem of the cloud as used in the US Army Signal Corps fallout prediction method.  Note that 90% is assumed to be in the mushroom head, and that 10% is in the stem (at lower altitudes), but the average size of the particles in the stem are larger than those in the mushroom head.  This type of analysis, based on trying to reconcile theory with observed fallout data, is the source of the statement about the assumed distribution in Glasstone's Effects of Nuclear Weapons.
AFSWP 895 fallout distribution across Rongelap Atoll in the 15 megatons Castle Bravo test on 1 March 1954 based on wind data analysis.  This is controversial and possibly very unreliable due to the inclusion of Eniwetok Atoll data (200 miles to the West of Bikini, i.e. 200 miles upwind!).  However, it shows that efforts were being made to try to determine the whole fallout pattern for the January 1955 Fall-Out Symposium.
AFSWP 895 fallout distribution doses to 48 hours across Rongelap Atoll in the 15 megatons Castle Bravo test on 1 March 1954 based on wind data analysis, combined with radiation measurements made on atoll islands.
AFSWP 895 fallout winds analysis by RAND Corporation for the 15 megatons Castle Bravo test on 1 March 1954 (the USS Curtiss was used as a weather observation ship which sent up balloons, which were tracked by radar to determine the wind pattern as function of altitude over the test site).

AFSWP 895 fallout in mushroom cloud of the 15 megatons Castle Bravo test on 1 March 1954 as determined by a RAND Corporation analysis.
AFSWP 895 IBM701 computer summation fallout prediction method for 15 megatons Castle Bravo test on 1 March 1954 as determined by a RAND Corporation analysis.  This was developed by Stanley Greenfield of RAND Corporation, who states on page 348: "The first problem that was tried on the machine [an IBM 701 computer] was the Castle-Bravo shot", using the shot time winds measured from the USS Curtiss, a ship near Bikini Atoll.  The predicted Bravo fallout pattern is shown below:
AFSWP 895 IBM701 computer prediction of fallout using shot time winds for 15 megatons Castle Bravo test on 1 March 1954 as determined by a RAND Corporation analysis.  Notice that the fallout is predicted to go essentially miss Rongelap Atoll (roughly 100 nautical miles East and slighly south of East, from ground zero).  Hence, there really was a wind shift that contaminated the islanders on the south of Rongelap (and nmearby Americans on Rongerik, to the east of Rongelap).  Even if the IBM 701 had been available to predict the fallout from Bravo on 1 March 1954, it would not have predicted the danger unless supplemented with a modern weather prediction including the changing wind pattern in the 6-7 hours following the detonation!
AFSWP 895 IBM701 computer prediction of fallout over Bikini Atoll using shot time winds for 15 megatons Castle Bravo test on 1 March 1954 as determined by a RAND Corporation analysis, comparison of measurements to predictions!
AFSWP 895 IBM701 computer prediction of fallout doses from a 50 megaton nuclear test as determined by a RAND Corporation analysis.  Note that the 1500 R dose would be reduced to a survivable 37.5 R by a protection factor of 40, the minimal specification for fallout shelters.
AFSWP 895 IBM701 computer prediction of fallout doses from a 1 megaton nuclear test as determined by a RAND Corporation analysis.  This is using the same model which successfully explained Bravo, and shows that with simple fallout shelters, fallout can be survived.
AFSWP 895: example of tabulated outdoor fallout areas for dose rates and accumulated doses from yields of 1 to 50 megatons.  Many different fallout models were compared in AFSWP-895, differences were due to different weighting in the activity distribution in the cloud and as a function of particle size, which affected how much activity came under the influence of winds blowing in different directions at different altitudes.  However, fallout is very predictable with modern data from the 1956 Redwing series as well as modern weather prediction computer programs that include jet stream trajectory forecasts.