Summary

The 11 buildings and infrastructure of the former Explosives Storage Area of the Atomic Weapons Research Establishment, Foulness Island, Essex, established in 1947.

Source: Historic England

Details

The Explosives Storage Area lies towards the northern end of the AWRE site in an enclosed compound to the north of a major drain. The scheduled area comprises the infrastructure servicing 11 explosives storage and security buildings constructed between 1947 and February 1953. The buildings are built of yellow stock brick, with flat reinforced concrete walls, and arranged mostly around the southern half of the oval of 1947. The entrance to the track is located at the south-west, flanked by two buildings: X25, a store room of two building phases which may also have been used as a search room; and XPP2, a police lodge. All the explosives related buildings in the area are protected by two single or a pair of lightning conductors, a method of protecting explosives buildings which became standard practice from the 1940s but was used from the outset at Foulness.

The key building in the group is the Explosives Preparation Laboratory X6 (23), where the explosives components of the devices for the Hurricane trials were assembled. Located approximately half-way up on the west side of the oval, X6 is a split level, flat-roofed rectangular building divided into two sections; a taller (6.04m) assembly bay to the north and a lower (3.19m) metrology and changing room bay to the south. The south elevation has three, 12-light, metal Crittall windows with concrete lintels and brick sills, all protected by metal shutters and there are two similar windows in the west elevation lighting the metrology room. A single, copper-clad door and one, 21-light window is at the north elevation of the assembly room. The assembly bay was entered from the west though tall sliding doors, replaced in the later C20. The southern bay is entered through a copper sheet-clad door at the southern end. Internally, the assembly room has an RSJ with a 6-ton pulley block, capable of lifting a device comparable in scale to the Fat Man bomb. Personnel entered the building through a single copper-clad door at its southern end. This led into a changing area typical of any building associated with handling explosives. On entering is a ‘dirty area’ where outdoor shoes were placed in the shoe boxes and if necessary, clothing changed. The personnel then stepped over the toe board, separating the dirty from the ‘clean area’ and put on the regulation magazine shoes. At the eastern end of this room were wash basins and an office, and to the north were doors into Laboratories 1 and 2. The relatively wide central door opening measuring 6ft (1.83m) between the main assembly room, Laboratory 1, and Laboratory 2 may suggest that some assembly work was done in this room. Laboratory 3 was used in later years as the metrology room, used for the precise measuring of components prior to assembly, and there is a large and heavy steel table at its centre. It is known that Mr Hessen was in charge of the metrology in 1952 and it is presumed that Laboratory 3 had this function at that date.

X6 played an important role in the development of the explosive lenses. Technically the manufacture of the lenses was extremely challenging, each of the lenses comprised alternate layers of cast high and low explosives. These had to be produced to very fine tolerances and free from any internal cracking that might develop during cooling. The explosive element of each lens was held in an outer aluminium shell, these were then joined together to form the bomb. The precision of this assembly work was absolutely critical to the operation of the bomb, as any misalignment of the lenses might result in the misdirection of the explosive shock wave on the fissile core. The basic principles were known from the wartime Manhattan Project. It was, however, an entirely new process to the British team tasked with the production of lenses. To approve this novel design and to gain experience, work at first concentrated on assembling a few lenses for test firing on the ranges, but tested further in the inert device, Alfred (see history above). It is likely that all three live devices were assembled in X6, but were unlikely to all have been kept there and may have been stored in X20 on the north-east side of the oval (see below).

To the west of X6 is the Non Explosives Components Store X5 (23a), its function is self-explanatory and supported the activities in X6. It is a single-storey, yellow stock brick building with flat concrete roof surmounted by lightning conductors, and lit by small, metal Crittall windows with concrete lintels and brick sills, all originally protected by metal shutters. The building is entered through a narrow door at the east elevation. When the lenses for the bomb were delivered from Woolwich they might either be taken directly to X6 or held in store. Buildings that may have been used to store the lenses include the Bare Charge store X21 (19); a contemporary footpath leading directly to X6 suggests a functional relationship between these buildings. X21 is a single-storey rectangular building with a flat roof, protected by copper strapping and lightning conductor poles In the east elevation is a projecting entrance porch with a metal door and a block opening in its south elevation. There are blocked elevations in the south and north elevations and a brick electrical isolation switch locker to the north. To the north of X21 is X20 (17), a high explosive store, a 5 bay rectangular, single-storey building in yellow stock brick with a thick, flat concrete roof supported on RSJ's. Full-height sliding metal doors lie at the east elevation and the south elevation has 18-light metal Crittall windows with hoods, five at the north and south elevations. The building is protected by copper strapping and lightning conductors. Internally, the overhead lifting beam and formerly open interior appear to be of sufficient size to have handled and accommodated at least two devices.

In addition to work on the development of the bomb another priority during the late 1940s was the understanding of blast effect on buildings to assist in civil defence planning. During the Second World War considerable knowledge on the effects of blast had been built up by studying bomb damage on different British building types and, immediately after the war, by visits to Germany and Japan. By 1947, some consideration was being given by the Fort Halstead team to the use of balls of high explosives to simulate the effects of an atomic air burst. To support this work specially shaped charges of high explosives were required to simulate the blast waves produced by larger explosions, the results of which could be mathematically scaled up to model the effect of an atomic weapon. It was probably to support this work that the Explosives Casting and Pressing Laboratories X23 (29) were also specified in late 1947. This building is entered from the south through double copper-clad doors into a lobby area, which also gives access to the Motor and Boiler House. Personnel entering the building were required to change into magazine shoes and clothing before passing over a barrier into the ‘clean area’. Explosives, presumably in sealed containers, were also brought into the building through the main doors suspended from the L-shaped RSJ lifting beam, rated at 1 ton. Once in the Explosive Preparation Room they were presumably unpacked before being taken to the Casting Room or one of the press rooms. Along the northern side of the building are three press rooms and a Compressor Room, where the hydraulic pressure for the adjacent rooms was produced. Due to the hazardous nature of the activities the main spine wall separating the press rooms from the central corridor is formed of 14 inch (0.36m) thick reinforced concrete. The fly press and 200 ton press specified in December 1947 remain in place, along with a compressor and 1 ton lifting beam. At a later date, to improve the building’s operational safety a number of doors were inserted in its outer walls. An early modification to the building appears to be a set of tall, copper-clad doors giving access to the 200 ton press room and linking it directly by a cleanway to the Powder Store X23A (18), to the north, a small rectangular building aired by metal ventilation grilles. A cleanway was also constructed around the western and northern sides of the buildings, and three doors inserted into its west wall. On the northern side a door was inserted to give access to the compressor room and the internal access to this room blocked. The south elevation of the small, rectangular Building X3 (22) to the west, described as a ‘Store for munitions which may not be stored in other explosives stores’ and was also referred to as a Special Store, may also have been used for this function. To the west of X23 are the Detonator Store X24 (20) and Magazine X4 (21), both small rectangular buildings with copper-clad doors, external electrical isolation boxes and flat, reinforced concrete roofs.

The scheduled area includes the concrete road and paths laid out in accordance with the plan of 1947, the buildings itemised above and lamp posts constructed between 1947 and February 1953. It excludes the buildings, structures, fences, fence posts and infrastructure which post-date this period and the central area of the oval track, including the pond to the north of the footpath that links buildings X6 and X21.

Source: Historic England

Reasons for Scheduling

The 1947 Explosives Storage Area on Foulness Island is scheduled for the following principal reasons.
* Historic importance: the site is nationally and internationally important through its association with key historical figures and events connected to the development of Britain’s first nuclear bomb;
* Rarity: the earliest 9 buildings in the Explosives Storage Area demonstrate innovative technologies and are unique nationally and internationally;
* Diversity: the site has a high diversity of component buildings and structures including the distinctive oval infrastructure which practically and functionally linked the buildings, and therefore the processes which took place within them;
* Survival: the buildings and structures survive well, the alterations reflecting the evolution of the site;
* Documentation: the site is well documented and researched, underpinning the assessment of national importance.

Source: Historic England

Sources

Other
The Atomic Weapons Establishment, Foulness, Essex: Cold War Research and Development Site, Survey Report.
English Heritage: Cocroft, W D and Newsome, S. 2009,

Source: Historic England