Bomb Power Indicator
used by the Royal Observer Corps during the Cold War to detect nuclear explosions
Bomb Power Indicator, also known by the acronym BPI, was an instrument built to detect nuclear explosions and measure the peak overpressure of their blast waves. It was used at the twenty five British Royal Observer Corps (ROC) controls and nearly 1,500 ROC underground monitoring posts, across the United Kingdom during the Cold War.
Overview
The instruments, operated by volunteers, measured the level of peak-overpressure at the instrument's location. Once readings had been combined with information provided by the Ground Zero Indicators it would be possible to estimate the size of the nuclear explosion in megatons. Detailed BPI information was backed up by the automatic AWDREY readings.
The BPI was designed and built by the Atomic Weapons Establishment at Aldermaston. The design was tested for performance and accuracy using real nuclear explosions at the 1957 nuclear weapons tests at Kiritimati (or Christmas Island), after being mounted on board a ship. A number of BPIs were also tested in Australia during the Operation Buffalo series of nuclear tests, with units located at various distances from ground zero.
Operations
Above ground, a pair of circular plated baffles would be affected by the passing of the blast wave. The detector was connected by a steel pipe to the indicator dial below ground in the protected monitoring post.
“Bomb Power Indicator” enters the record as used by the Royal Observer Corps during the Cold War to detect nuclear explosions. Crown Archives preserves that source wording while asking what Bomb, Power and Indicator can confirm, complicate or overturn.
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The record creator and administrative purpose are central evidence, because official documentation reflects both action and institutional priorities. The source revision retrieved here is dated Dec 10, 2025. The linked authority identifier is Q4940421. None of the 0 selected statements returned an explicit reference. The first chronological checks are 1957.
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This entry incorporates text from “Bomb Power Indicator” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.