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Atomic Weapon Diagram Publicized

Guest Soulskill

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Guest Soulskill

Wikileaks has released a diagram of the first atomic weapon, as used in the Trinity test and subsequently exploded over the Japanese city of Nagasaki, together with an extremely interesting scientific analysis. Wikileaks has not been able to fault the document or find reference to it elsewhere. Given the high quality of other Wikileaks submissions, the document may be what it purports to be, or it may be a sophisticated intelligence agency fraud, designed to mislead the atomic weapons development programs of countries like Iran. The neutron initiator is particularly novel. 'When polonium is crushed onto beryllium by explosion, reaction occurs between polonium alpha emissions and beryllium leading to Carbon-12 & 1 neutron. This, in practice, would lead to a predictable neutron flux, sufficient to set off device.'


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Host name: wikileaks.org is from Sweden(SE) in region Europe


Censored early drawing of an atomic weapon based on the famous U.S Los Alamos "Fat Man" device which was dropped on Nagasaki and detonated in the Trinity test. The diagram is from a report completed by William G. Penney on 1 July 1947


The Penney Report, outlining the features of an atomic bomb based on the U.S. Fat Man pattern, and the tasks required to develop one for Britain, was declassified and made available to the the public under the Public Records Act (now amended by the Freedom of Information Act which came into force in January 2005).


However the UK Public Record Office File AVIA 65/1163, "Implosion" (covering the years 1947-1953) was then withdrawn from public access during 2002 and this will not be reconsidered until 2014.


The actual legal status of this file remains as a public record. Its access condition has been changed to "Retained by Department under Section 3.4" (of the PRA) which means that the file has been returned to the custody of the originating department (Ministry of Supply) or its successor. This limitation of access does not constitute reimposition of a secret security marking, and no attempt appears to have been made by the UK government to contact people who had previously obtained copies of this file.


It should be observed that Penney's description and discussion of development are no more revealing than descriptions of the United States' first implosion bomb that have been publicly available for many years, and in fact are less precise than other descriptions that are now available, and are in any case are the oldest material in the file, written before any actual bomb development work had been undertaken in the UK.


Penney's description is by all accounts far less technical and detailed than "Tuck's Bible", detailed notes written around this same time by James Tuck, another member of the British Mission to Los Alamos who, unlike Penney ,was deeply involved in the actual design and development of the implosion bomb. Tuck's Bible has never been made public.


Penney and the Start of the Post-War British Atomic Bomb Program


William G. Penney, the British "Oppenheimer", spent most of 1944 and 1945 as part of the British Mission at Los Alamos. This was an elite team of British scientists, and emigres to Britain, who contributed to the development, testing and use of the atomic bombs during the Second World War. Sent as a specialist on ocean waves, his gifts were readily apparent at Los Alamos and he soon was made one of the five members of the Los Alamos "brain trust" that made key decisions in the direction of the program, putting him in the company of Robert Oppenheimer, John Von Neumann, "Deke" Parsons and Norman Ramsey. On 27 April 1945 Penney became one of only two representatives from Los Alamos (and the only Briton) to be part of the ten man Target Committee that drew up the list of targets for the atomic bombing of Japan. Penney travelled to Tinian Island in the Pacific to be on hand for planning and briefing the atomic bombing missions. Penney actually witnessed the bombing of Nagasaki, flying in an observation plane accompanying the attack. Afterward he conducted damage surveys there on the ground.


Penney returned to Imperial College immediately after the war, but accepted an appointment to head the Armament Research Department (ARD) on 1 January 1946. On 8 January 1947 the secret GEN.163 Cabinet committee of six Ministers (headed by PM Attlee) decided to proceed with development and acquisition of atomic weapons. Penney did not receive word of this decision until May 1947 when he was finally asked by Lord Portal to lead Britain's own nuclear weapon program. The decision was not disclosed publicly in any respect until 12 May 1948, when an oblique reference was made to atomic weapon development in parliamentary discussions.


In June 1947 Penney began assembling a team to work on the bomb. One of his first steps was to prepare a document describing the features of the U.S. implosion bomb, breaking down the development tasks required to replicate it, and identifying outstanding questions that required further research. This report was completed on 1 July, was entitled Plutonium Weapon - General Description (UK Public Record Office File AVIA 65/1163, "Implosion") and gave the British atomic weapons program a preliminary design description roughly equivalent in terms of detail to the description provided the Soviets by Klaus Fuchs.


The diagram is an overview of a plutonium-239 based weapon. The synthesis of plutonium requires a plutonium breeder nuclear reactor which in turn requires a supply of enriched uranium or significant quantities of natural uranium and a large core. In general, the plutonium-production route to weapons development, which involves reprocessing of spent reactor-fuel to extract plutonium, is easier to detect than small-scale clandestine uranium enrichment.


The censored diagram has also been made available from the nuclearweapons.org archive who also provided much of the above text. The text to the report can be found here: http://www.nuclearweaponarchive.org/Librar...eyPuWeapon.html


Quick analysis of purported “Atomic Bomb Diagram”


1. Neutron Initiator


Theoretically workable. Polonium is a well known alpha radiation emitter. Alpha radiation is He atoms stripped of electrons and accelerated towards c. When polonium crushed onto beryllium by explosion, reaction occurs between polonium alpha emissions and beryllium leading to Carbon-12 & 1 neutron. This, in practice, would lead to a predictable neutron flux, sufficient to set off device. Widely known that once critical mass is obtained, in order for bomb to explode, requires fission initiation by neutron generation; this will do the trick. Polonium 210 specifically well known alpha emitter. Gold/nickel foil layer around beryllium is sufficient to prevent pre-reaction prior to explosive compression due to low penetrability of alpha radiation (can’t pass through paper). This allows for long-term storage of initiator.


The Boron-10 shielding is to keep stray (eg cosmic ray generated) neutrons from pre-initiating the chain reaction.


The polonium in the initiator has a short, half-year halflife.


The inner layer of the Be sphere is etched with grooves, these will create Be jets when imploded (shaped charge effect) which mixes the Be and Po very quickly.


2. Diagram


Roughly to scale. No easy feat in days prior to computerized drafting tools. Measurements located on table in top left roughly match drawing scale. Note archaic units (lbs): physicists after ‘50s probably would have used SI units, regardless of country. Also note quality of arcs (Fast HE/Slow HE) indicates is drawn by professional draftsman.


3. High Explosives & Miznay/Schardin effect (e.g. shaped charge)


Miznay/Schardin effect will work in this design, in all likelihood, though the additional layer of HE after the first layer of lenses is a surprise. Are the lenses strong enough to compress the second layer of HE? In any event, there’s enough explosive in there to cause the Miznay/Schardin effect, and enough aluminum to convincingly crush the core.


The outer layer of slow + fast explosives is used to create a number of converging planar shock wavefronts. The inner layer of solid HE is not compressed, but is initiated fairly uniformly by the many planar wavefronts hitting it. The uniformity of initiation is important to the compression of the core.


Also note the squiggly lines indicating compression.


Note also the “possibilities table” in the bottom left. This indicates several possibilities as to how much explosive is necessary, indicating that this may be an incomplete design, perhaps a pre-Trinity design.


4. Weaponization.


The weapon has a removable core, or at least a serviceable one, as evidenced by felt layers. This is necessary to allow the bomb to be disassembled.


5. Assessment.


This diagram is not really a secret to foreign intelligence services; nobody is going to be surprised by this design, just by the fact that it’s appeared in public. Open sources have speculated on these matters for a long time (see nuclear weapons design article in Wikipedia), and this just confirms that they were right. (The structure of the neutron initiator is elegant, and interesting, however.)


This is a crude, but effective, plutonium based design. Devices that are orders of magnitude more efficient are possible. A disclosure of, for example, the plans of the W-88 or a Russian equivalent, would be far more threatening, as there are actually real secrets involved there not known to all the NWS (the Big-5 + India, Pakistan, Israel, North Korea) or Virtual NWS (Germany, Japan, Sweden, South Korea, Canada, Ukraine, Taiwan, Italy, Spain…to name a few) intelligence agencies. After 1949 or so, disclosure of this would not have been a real threat to U.S. national security.


The real problem about building one of these designs is the rarity (at least outside of NWS nuclear facilities) of plutonium and polonium, as well as the ability to fabricate sophisticated high explosives to exacting specifications. We’re not talking about IEDs here. To build a nuclear weapon requires a state.


United States

Military or intelligence (ruling)

US Department of Defense

Wikileaks release date


Tuesday March 11, 2008

Primary language



File size in bytes



File type information


JPEG image data, JFIF standard 1.01

Cryptographic identity


SHA256 7f1faeaadf7abedad8d6de2ffe1a507ab956c506aa1840bb1b51db7ea87e1f27



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