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 ship, HMS Plym (K271), moored in 40 feet depth 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 This nuclear test information is not superseded by abstract theoretical computer models, because nuclear explosion phenomenology is complex for such burst situations.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 time-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 the fireball and thus 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 Tewa 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 generally 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."
Figures below are from Shelton's paper Physical Aspects of Fallout; the first shows fallout build up 14 miles cross-wind from 5 Mt Tewa ground zero, and the second shows the dose rate build up downwind on the deck of a WWII Liberty ship in the fallout. We also include Shelton's comparison of dose rate versus fallout areas graphs scaled to 1 megaton fission from tests of vastly different yield (1.2 kiloton - 5 megatons) and different fission yield tests, and also his graph of local fallout percentage versus scaled height of burst. A key point to emphasise is, the activity versus particle size distribution in surface bursts is not massively dependent on the preshot soil particle size distribution (Small Boy on fine silt at the dried lake bed of Frenchman Flats Nevada in 1962 proved that very small particles silt particles are fused together into much larger fallout particles). Also, the maximum radiation dose rates from fallout are higher for lower yields, where the fallout reaches close-in targets within a couple of minutes, as compared to longer fallout arrival times from higher clouds, e.g. hours for most of the large fallout areas from megaton bursts. Glasstone's decision to give only "theoretical" dose rates for 1 hour regardless of yield (when for high yields, most of the fallout is still airborne and has not even arrived with 1 hour) is entirely misleading. The fallout hazards are severely misunderstood in oversimplified computer models employing the unfused soil particle size distribution. Glasstone obfuscates again by suggesting that fallout arrival time is horizontal distance divided by wind speed; this is approximately correct at very large distances downwind where the doses are low due to decay during the large arrival time, but for the key threat at shorter distances it is false, omitting the time taken for fallout to descend from the higher clouds of higher yield detonations, exaggerating fallout hazards close to those detonations. The Effects of Nuclear Weapons is severely misleading and obstructs understanding.
Now let's move on to the recently declassified UK Atomic Weapons Establishment AWRE paper at the September 1957 Tripartite Conference on weapons effects, J. D. Macdougall, "On the Prediction and Interpretation of Fall-Out Patterns", showing fallout prediction methods for ground and tower bursts at Operation Buffalo, Maralinga, 1956:
"The surface burst was of yield about 1 kiloton [Buffalo-2, 1.4 kt yield Mark I uranium-235 pit], and the best information on the cloud model was obtained from this round mainly because of the large angular shear in the mean wind. The observed fall-out pattern is shown in Figure 1. Figure 2 shows the calculated positions and times of arrival at the ground of particles falling at various speeds from various heights in the cloud. The most striking feature abcut the fall-out pattern is its two lobed nature. ... The fall-out from the main cloud forms the lobe to the NE of the firing site. A thorough analysis of this pattern has been made in order to determine the distribution of activity with height throughout the cloud, and also the distribution of activity with falling velocity at various levels in the cloud." [See Figs 1 and 2, below. Winds below 6,000 feet carried the mushroom cloud's stem towards the north, while the main head of the mushroom cloud was carried towards the east, so from a wind analysis of the detailed fallout pattern, it was possible to analyse precisely how much radioactivity was contained by the stem and how much was in the head of the cloud.]
That Dacdougall paper at the 1957 Tripartite Conference is clearly based on the longer more detailed UK Atomic Weapons Establishment report AWRE-T25/58, analyzing Operation Buffalo fallout data (linked here). See also the full British fallout patterns from Operation Buffalo: J. J. Rae, AWRE-T49/57, Operation Buffalo Radiation Survey of Ground Deposited Radioactivity, which we uploaded to internet archive, linked HERE (which gives more detailed close-in fallout contours for the surface burst Buffalo-2, and related data on the neutron induced activity versus fission product contributions to the dose rates than the Tripartite paper etc). It should be noted that a large percentage of the fallout gamma dose rate at 24 hours after Buffalo-2 came not from fission products, but instead from neptunium-239, a soft gamma emitter. Operation Buffalo report AWRE-T50/57, linked here, in section 6.2 on page 11 states that there were about 1.6 atoms of Np-239 formed per fission in the Buffalo-2 weapon, i.e. a capture/fission ratio of 1.6, caused by the neutron capture in the thick U238 neutron reflector around the pit in the weapon, forming U-239 which decays quickly with 23.5 minutes half life into Np-239 with 56.5 hours half life.
With the exception of Buffalo-1, the 15 kiloton small 71 cm (2 ft 4 inches) diameter Red Beard tactical bomb warhead tested in 1956, British implosion nuclear weapons were bulky 5-feet diameter affairs with heavy U238 reflectors. This changed with Operation Antler in 1957, where much smaller tactical designs were trialled. If you replace U238 with a beryllium reflector, the total mass of pit plus reflector matter for compression is far less, so you need less high explosive to do the compression, so the weapon's mass and diameter is miniaturised. Antler-1 was Britain's first test of a 113 kg very small diameter (less than 50 cm) plutonium implosion system, called Pixie. It was placed inside a hydrogen bomb assembly minus the lithium deuteride fusion charge and secondary fission pusher, but with a cobalt neutron tracer placed there inspead to determine the enhanced neutron release from a compact implosion system (more neutrons escape when a smaller layer of neutron-absorbing high explosives are around the core). The purpose of this was to assess the risk of neutrons from the primary stage heating up and expanding fissionable material in the secondary stage of a hydrogen bomb prior to the compression and fusion ignition of the secondary stage by x-ray induced ablative recoil hydrodynamic pressure, which is a relatively slow material flow process compared to the speed of fast neutrons. By measuring the amount of neutron-induced cobalt-60 the fallout pellets, compared to cobalt-59 (which has not absorbed neutrons), the neutron fluence at the secondary stage could be estimated and thus the amount of boron-10 or beryllium neutron "interstage" shielding necessary to protect the secondary stage from pre-fission could determined. Antler-2 was a 6 kiloton tactical warhead called Indigo Hammer, for a surface-to-air missile, while Antler-3 was Britain's first 25 kt composite-core weapon, a plutonium pit inside a uranium-235 shell.
Despite such nuclear proof tested facts, fake news spreading "historians" and "journalists" such as Duncan Campbell in his fake news type 1983 book War Plan UK falsely deceived readers by outrageously asserting that the Anderson shelters etc were never proof-tested at any UK nuclear tests, when in fact even the very first UK nuclear weapon test was deliberately designed to provide as much information on these shelters and other civil defense as possible, as Penney stated in his radio broadcast at the time, as as official statements and photographs repeatedly showed. The 15 Anderson shelters at Operation Hurricane were exposed by Home Office Scientific Advisory Branch scientists George Stanbury and Frank Pavry, and the data was incorporated into improved civil defence plans, contrary to political propaganda attacks on civil defence protection data as being imaginary. Further nuclear tests exposed further shelters, both for military field defences analysis and civil defence, but the data was kept secret, allowing politically-motivated "pro-disarmament civil defence critics" supported by Moscow's World Peace Council propaganda (an attempt to get the West to disarm out of fear), to falsely claim it never existed! See UK Atomic Weapons Establishment's report AWRE-T17/54, the Operation Hurricane nuclear test report on 15 Anderson shelters by Frank H. Pavry (PDF linked here):
Secrecy issues on British nuclear testing began at the time of the tests. Hedley R. Marston was an Australian scientist at Adelaide University whose paper on the increase in iodine-131 levels due to Britain's 1956 Mosiac and Buffalo nuclear tests in over 230 thyroid samples from 26 areas in northern and north-eastern Australia was delayed or suppressed (depending on your point of view) for 18 months. Sir William G. Penney, the director of those tests, objected to two paragraphs in Marston's draft paper which revealed nuclear weapon design. After these were finally deleted, "The accumulation of radioactive iodine in the thyroids of grazing animals subsequent to nuclear weapon tests" was belatedly published by the Australian Journal of Biological Sciences in August 1958. (In America, Lester Van Middlesworth had published "Radioactivity in Thyroid Glands Following Nuclear Weapons Tests" without censorship in 1956; Science, vol 123, pp. 982-983.) Marston found that the 60 kiloton Mosiac-2 nuclear test at Monte Bello in June 1956 raised iodine-131 levels by over factor of 100 in samples of sheep and cattle thyroid glands (up to 0.83 uCi/g of I-131 for cattle thyroids; up to 0.144 uCi/g for sheep thyroids). These were still very small doses so the consequence was not biological but political: an increase in hostility of Australian public opinion to nuclear testing on their soil. In 1952, a Gallup poll showed 58% of Australians behind the nuclear tests, and only 29% opposed. Five years later, in 1957, anti-nuclear propaganda was rife and the figures were starting to reverse, with a Gallup poll showing 49% of Australians opposed to nuclear testing and only 37% in favour. (See Lorna Arnold, A very special relationship: British atomic weapon trials in Australia, H. M. S. O., London, 1987, page 221.)
If all the useful facts had been immediately published, civil defence, nuclear deterrence credibility, and the prestige of nuclear technology could have been saved. Instead all of this was ironically squandered by being withheld from Joe Public in a dim-witted imitation of the totalitarian states bureaucratic secrecy it had been invented to oppose in the first place. There's never been any effort to publicise facts. Secrecy tricks had been in place from the very beginning, with the secret British Chiefs of Staff January 1946 report on atomic bomb requirements resulting a year later in Clement Attlee's secret January 1947 Cabinet decision to make British nuclear weapons. Even when the decision was finally "declassified and published", the news was deliberately and successfully "buried" by the "trick" of a planted parliamentary question. George Jeger, a Labour Party MP, was asked to ask a "boring" question in the House of Commons which would "technically disclose the fact" that Britain was developing nuclear weapons, without doing so in a way that would inform anybody of anything (the following is from the House of Commons Debates, Volume 450, Column 2117 on 12 May 1948):
"Mr George Jeger asked the Minister of Defence whether he is satisfied that adequate progress is being made in the development of the most modern types of weapons.
"The Minister of Defence (A. V. Alexander): Yes, sir. As was made clear in the Statement Relating to Defence 1948 (Command 7327) [which did not disclose that nuclear weapons were being developed!], research and development continue to receive the highest priority in the defence field, and all types of weapons, including atomic weapons, are being developed."
The attitude of the government was to keep nuclear information secret to prevent fact-based democratic debate, using trickery.
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