The city of York in the United Kingdom is a small city – population 140,000 – with an old past. Founded by the Romans in AD71, by the Middle Ages it had become a major wool trading centre. Fast forward to the 19th century, and it was the hub of the railway network. You can still see evidence of that past – the defensive wall around the city, and the fantastic railway museum.
But what the potted histories often don’t mention is that York was also home to one of a string of underground bunkers built in the 1950s across Britain. The bunkers were designed to monitor the nuclear attack that may have emanated from the hostile Soviet Union, located just a (relative) hop and a skip away. These are places from which it was fully expected that observation and monitoring would be made of a dying country – one enveloped in poisonous and spreading radiation, killing all those in its path.
So let’s go inside the York Nuclear Bunker, a place redolent of circumstance almost beyond imagination.
“Coming to the party on the weekend? Oh, OK. You’ll find us right at the end of the street, just past the nuclear bunker…”
Despite it now being in the midst of houses, when the bunker was built, it was on the site of a former orchard of a mansion, in a hollow hidden from a nearby busy road.
The bunker – one of a type officially called a “semi-sunken Group Headquarters” – used a ‘cut and cover’ construction technique. This involved digging a pit, building the concrete structure and then covering most of it with earth. At least 3 feet of earth was placed over the concrete – this was designed to increase protection against bomb blast and heat, and to provide some defence against radiation.
The entrance block is the only visible part of the three-level structure. It was originally painted white in order to reflect the heat from nuclear flashes. The door, designed to withstand blasts, opens to a passageway divided by an air lock. The air lock used two rubber-sealed, gas-proof doors designed to prevent nuclear radiation particles from entering. At right of the entrance is a telescopic radio antenna that could be raised when signals needed to be sent and received. The antenna is surrounded by an earthed cage to protect against electromagnetic impulse damage. At the opposite end of the entrance block was an emergency escape hatch that used a counter-weighted steel manhole cover. The hatch was designed to withstand a compressive force of 30 tonnes.
The bunker used extensive air-conditioning and ventilation equipment. Ventilation could be configured in four modes: ‘normal’ (fresh air mixed, cooled and circulated); ‘modified normal’ (air-cooling system turned off to save water); ‘recirculation’ (internal air re-used); ‘filtration’ (air drawn in through particulate filters to remove dust and radioactive particles). Air conditioning was important as the outside atmosphere may have been heated by the nuclear blasts. Power came from a diesel generator - the tank had enough fuel for 40 days of continuous use. Air compressors were used to power the waste ejection system: because the bunker was located below the level of the sewer, waste needed to be periodically blasted upwards from holding tanks.
During its life (it was opened in 1961 and closed in 1992) the York bunker was staffed by three permanent staff and, during times of emergency, 50 – 60 Royal Observer Corps volunteers, scientists and telecommunications engineers. These worked in three shifts – duty, standby and rest. Little sleeping accommodation was provided: this dormitory comprised six bunks while another had provision for four people, necessitating ‘hot bedding’ - people used whichever bed was available. During training, the bunker was expected to operate in a ‘nuclear environment’ for at least two weeks. A small kitchen and canteen were also provided.
The bunker had three main functions: plotting where atomic bomb bursts had occurred; assessing their magnitude; and then plotting the extent and movement of a radioactive fallout cloud. These charts were used to plot the location and size of the bomb bursts.
This Bomb Power Indicator comprised a simple pressure gauge. On the surface, the indicator used a pair of circular steel plates attached to a galvanised steel pipe that ran to the indicator. The indicator, reading up to 5 psi, using expanding metal bellows to drive the needle. The needle remained at its maximum until reset – a process that would normally occur after 10 seconds in order to record further explosions.
This Ground Zero Indicator was also located on the surface. It comprised a cylindrical pinhole camera using four 5mm holes, with one hole each facing north, south, east and west. Inside the cylinder the space was divided into four semi-circular quadrants, each equipped with a piece of low sensitivity photographic paper. The paper was mounted within a plastic sleeve on which was marked a grid indicating bearings and elevation. If a nuclear explosion occurred, a spot would be burnt in the paper. By the use of several of these devices located at different reporting posts, the Group Headquarters could determine the location of the bomb. Note that following a bomb blast, the photographic paper had to be physically retrieved from the device: this would have exposed the retriever to potentially lethal radiation. Only rudimentary decontamination facilities were provided at the bunker.
The extraordinarily primitive detectors were later supplemented by an electronic detector. The ‘Atomic Weapon Detection Recognition and Estimation of Yield’ (AWDREY) device was designed to detect both the optical and electromagnetic signatures of a nuclear explosion and set off automatic alarms, including transmitting data about the explosion to other group and sector headquarters. Twelve units provided coverage of the whole of the UK. From 1974, a further electronic detection system gave enhanced direction capability.
This is the main operations room. At the map desk sat the duty controller and senior warning officers. Behind the desk are two large maps printed on transparent plastic. Display A showed the current situation; Display B showed the cumulative situation, plotted at two-hour intervals. Both maps were for the local area. In addition, there were maps for Europe and the United Kingdom. The clear plastic maps were updated from behind, using chinagraph pencils.
The information was relayed to the plotters and warning officers by post display operators receiving information from outlying underground monitoring posts. (The underground monitoring posts were three-person units equipped with pressure and photographic paper indicators. Hundreds of these underground posts were built across the UK.) The details were written by operators on the white boards; the boards were rotated every five minutes so that they could be read by those working within the ‘well’ of the room.
A sound-proof communication room was located adjacent to the ‘well’ (the ladder is a recent addition for emergency evacuation of visitors). Equipped with machines such as teleprinters, the equipment was designed to have redundancy – coping with the failure of certain communication channels. Information was transmitted to other Group Headquarters and the Midland Sector Control. In the late 1908s, the telecommunications equipment was upgraded and the manual display boards replaced by desk-top computers and monitors.
This whiteboard gives a good feel for the operational situations likely to be met. It includes sections to indicate the status of standby power, ventilation and mains water; whether the shelter is being subjected to nuclear fallout; the remaining number of ration packs; and stocks of fresh water and diesel.
The York Nuclear Bunker is an extraordinary indicator of the temperature at which the Cold War operated. One of 29 such facilities constructed across the UK, the York bunker was part of observation and monitoring system that in itself, was just part of a broader military and civil defence response to the Soviet threat.