Graphite Low Energy Experimental Pile

Graphite Low Energy Experimental Pile, commonly known as GLEEP, was the first nuclear reactor to operate in Western Europe. Constructed at the Atomic Energy Research Establishment in Harwell, it was a low-power, graphite-moderated reactor designed for fundamental research and training. Its successful operation in 1947 marked a pivotal moment for the nascent British nuclear program, providing critical data that informed the design of subsequent reactors like the BEPO and the Windscale Piles.

History and context

Following the end of the Second World War and the dissolution of the wartime Tube Alloys project, the United Kingdom was determined to establish an independent nuclear energy and weapons program. The Labour government under Clement Attlee authorized the creation of the Atomic Energy Research Establishment at the former RAF Harwell airfield. The primary initial objective was to build a research reactor to train scientists and study neutron behavior, leading to the approval of GLEEP. Its design was heavily influenced by earlier American reactors, particularly the X-10 Graphite Reactor at Oak Ridge National Laboratory, but was adapted by British scientists and engineers for domestic purposes.

Design and construction

GLEEP was a simple, air-cooled, graphite-moderated pile. Its core was constructed from blocks of high-purity graphite, forming a cube approximately 6.7 meters on each side, within which were channels for fuel and experimental access. The fuel consisted of metallic uranium rods, sourced initially from the Belgian Congo, clad in aluminium. Unlike later power reactors, it had no radiation shielding around its core, relying on its low power and the site's remote location for safety. Construction was overseen by key figures like John Cockcroft, the first director of the Atomic Energy Research Establishment, and involved numerous personnel who had worked on the Manhattan Project.

Operation and experiments

GLEEP first achieved criticality on 15 August 1947, under the supervision of a team led by Kathleen Lonsdale. It operated at a very low thermal power of 100 kW, sufficient for experimental purposes but not for power generation. Its primary role was as a "neutron factory" for a wide range of fundamental physics experiments, including precise measurements of neutron cross-sections for various materials like graphite and beryllium. These experiments were vital for calibrating instruments and validating theoretical models used in the design of Britain's first plutonium production reactors, the Windscale Piles. It also served as an indispensable training tool for the first generation of British nuclear scientists and engineers.

Legacy and decommissioning

GLEEP operated continuously for 15 years, far exceeding its intended lifespan, and was finally shut down in 1962. Its decommissioning was a landmark project, becoming one of the first nuclear reactors in the world to be fully dismantled. The process, completed by 1964, involved removing the fuel and placing the irradiated graphite core into sealed containers for storage. The reactor's legacy is profound; it provided the foundational knowledge and skilled personnel that enabled the success of the British nuclear program, including the subsequent Magnox reactor stations. The reactor hall at Harwell was later repurposed for other research.

Technical specifications

* **Type:** Graphite-moderated, air-cooled thermal reactor. * **Thermal Power:** 100 kW (0.1 MWth). * **Core:** Cube of graphite blocks, ~6.7 m per side. * **Fuel:** Natural uranium metal rods, aluminium-clad. * **Coolant:** Air (natural convection). * **Moderator:** Graphite. * **First Criticality:** 15 August 1947. * **Operational Period:** 1947–1962. * **Location:** Atomic Energy Research Establishment, Harwell, Berkshire.

Category:Nuclear research reactors Category:Harwell, Oxfordshire Category:1947 in science Category:Graphite-moderated reactors