It's now seven decades since the heyday of British atmospheric nuclear weapons tests (Operation Buffalo, which included a land surface burst at Maralinga, was in 1956), and finally all of the key UK top secret classified nuclear weapon test reports, the Atomic Weapons Research Establishment "AWRE-T" series reports, have been declassified and scanned into PDF form of high quality (I've uploaded them as PDF files to Internet Archive here - there are currently 3,916 downloadable PDF files there, including all key UK and USA nuclear test reports, so they can't simply disappear again under whims of "secrecy" for another 70 odd years, if deemed politically inexpedient by those who hate the deterrence of war and civil defense to mitigate against the failure of deterrence or "demonstration attacks").
These reports are absolutely essential to understand problems with Glasstone's book The Effects of Nuclear Weapons. I will discuss the key information now released in these formerly classified reports in this blog post (some data was extracted from certain reports in the previous post).
Among the large number of newly-released UK Top Secret weapon test reports is a high quality scan of Top Secret radiation dose rate histories for a set of remote radiation monitors in different positions around the 1952 Operation Hurricane nuclear test (25 kt weapon centre 9 feet below water line, aboard ship anchored in water 40 feet deep, Monte Bello):
ABOVE: some of the Top Secret classified sets of initial and fallout gamma dose rate time histories for Operation Hurricane, a bomb burst with its centre 9 feet below the waterline, inside a 1,450 ship, moored in 40 feet of water, 400 yards off Trimouille Island in the Monte Bello group, Western Australia. As shown, the automatic radiation detector station TH47, 1 km directly downwind and on a land station at Trimouille Island, recorded a peak fallout gamma intensity just over 1,000,000 R/hour at 2 minutes after detonation, which decayed to 12,000 R/hour at 1 hour after burst, and to just 330 R/hr at 10 hours. This proves the very short duration of very intense radiation hazards from fallout in such detonations. This nuclear test information is not superseded by abstract theoretical computer models, because nuclear explosion phenomenology is complex for such burst situations. AWRE has now made available a high quality scan of the AWRE-T1/54 report of 1954 which summarizes the physical phenomena (while omitting the Top Secret radiation intensity-time graphs) of Operation Hurricane which shows the times evolution of the complex physical phenomena, particularly the way that the inverted cone of water and debris (i.e., bottom mud and ship's iron oxide) erupts through the early fireball, rapidly cooling it at limiting the observed thermal yield partition to under 2% (we had received a lower quality scan of a declassified photocopy decades ago - I first wrote to AWE Library for this information in the early 1990s, and later uploaded it to internet archive; but the latest higher quality scan photos were finally clear enough to indicate the time-dependent fireball and water cone phenomena):
For comparison of Operation Hurricane's intense early time dose rates to a 5 megaton hydrogen bomb test, Redwing-Tewa in 1956, AWRE has usefully declassified and scanned in its copy of Dr Frank H. Shelton's paper Physical Aspects of Fallout, which was presented at the September 1957 Tripartite Conference (USA-UK-Canada) on Nuclear Weapons Effects, summarizing key results from Operation Redwing fallout studies in 1956. (Note that Shelton was solely responsible for getting the fallout data from the 87% fission dirty 5 megaton Redwing-Tewa test, by pushing - as Technical Director of the U.S. Armed Forces Special Weapons Project, for it to be fired in very shallow water, since others had wanted to detonate it in deep water which alters the close-in fallout distribution. Shelton discusses this briefly in his 1988 and 1992 revised book Reflections of a Nuclear Weaponeer, and there is also extensive declassified documentation of this change in Redwing planning which facilitated a massive increase in fallout documentation in 1956.) Shelton's Physical Aspects of Fallout concisely analyzes and summarizes the implications of all of the preliminary Redwing radiation and fallout reports, stating:
"Salvos of rockets were fired at H + 7 minutes and H + 15 minutes on a number of the Operation REDWING shots. The rockets telemetered to a ground receiving station the gamma radiation dose rate as a function of time along the trajectory. From trajectory information the ionization rate can be correlated with position in space. ... At H + 7 minutes the contours of a given activity per unit volume were concentric toroids, the more intense being in about the lower 1/3 of the cloud and about 1/3 of the distance from the axis to the edge of the visible cloud. The activity per unit volume varied by a factor of about 30 from the most concentrated area to the edge of the cloud and negligible activity was found when rockets traversed the visible stem. At H+ 15 minutes the activity was spread over a larger region and, in particular, activity was general in the region below the bottom of the visible cloud. Of course this is activity being carried on the larger particles under the influence of gravity. By integrating the activity over space, the total activity accounted for was usually very close to the total fission activity of the bomb at H + 7 minutes and confirmed again that essentially only several percent of the activity is in the stem at early times. ...
"... Throughout the shot atoll various islands were instrumented for fallout. ... Fallout from a detonation of the order of a megaton will begin to arrive on the ground over an area the order of the size of the visible cloud, almost like a blanket at about 15-20 minutes for a large yleld surface burst on an island or presumably on land. Fallout from a shot of the order of a megaton on a barge in water will begin to arrive at the surface at about 30-40 minutes. These times of arrival of the first fallout are of course related to the large particle sizes. ... The radiation rate will build up on the ground under the cloud and reach a peak in about 100 minutes for a detonation of the order of a megaton. The magnitude of the peak will be a function of the fission yield." [Figure below from Shelton's paper shows fallout build up 14 miles cross-wind from 5 Mt Tewa GZ.]
(17 September 2026: This blog post is incomplete and will be updated and expanded later.)
