Universities Research Reactor, also known as Universities' Research Reactor or University Research Reactor, was a small Argonaut class

nuclear research reactor Research reactors are nuclear fission-based nuclear reactors that serve primarily as a neutron source. They are also called non-power reactors, in contrast to power reactors that are used for electricity production, heat generation, or maritim ...

Risley, Warrington Risley is a district in the northeast corner of Warrington, in the Warrington district, in the ceremonial county of Cheshire, England. Within the boundaries of the historic county of Lancashire, it lies south of Culcheth and is historically pa ...

, England that went critical on 7 July 1964. It was jointly owned and operated by

Manchester Manchester () is a city in Greater Manchester, England. It had a population of 552,000 in 2021. It is bordered by the Cheshire Plain to the south, the Pennines to the north and east, and the neighbouring city of Salford to the west. The t ...

and

Liverpool Liverpool is a city and metropolitan borough in Merseyside, England. With a population of in 2019, it is the 10th largest English district by population and its metropolitan area is the fifth largest in the United Kingdom, with a popul ...

universities and used for performing

neutron activation Neutron activation is the process in which neutron radiation induces radioactivity in materials, and occurs when atomic nuclei capture free neutrons, becoming heavier and entering excited states. The excited nucleus decays immediately by emittin ...

work and training reactor operators.

Design

The reactor used highly

enriched uranium Enriched uranium is a type of uranium in which the percent composition of uranium-235 (written 235U) has been increased through the process of isotope separation. Naturally occurring uranium is composed of three major isotopes: uranium-238 (238 ...

metal fuel clad in aluminium. The fuel elements consisted of bundles of flat plates rather than rods. The core was cooled by light water. The fuel elements were situated within six open-topped aluminium tanks containing water that were separated and surrounded by graphite. This meant that moderation was part by the water within the tanks and part by graphite - with graphite serving as the reflector. Reactivity control was provided by four semaphore signal–type control blades held by magnetic clutches to shafts that could be driven by geared electric motors. The blades were made of cadmium plates riveted to aluminium blades. The insertion of a single blade was sufficient to shut down the fission chain reaction. The simple control system did not use voting logic. Any detected fault resulted in an immediate

scram A scram or SCRAM is an emergency shutdown of a nuclear reactor effected by immediately terminating the fission reaction. It is also the name that is given to the manually operated kill switch that initiates the shutdown. In commercial reactor ...

. Power failure also produced an immediate scram as the magnetic clutches on the control blades would disengage, certain control instrumentation had battery back up support. The heat generated by fission was carried away by the cooling water and disposed of outside the facility by means of a forced-draft cooling radiator. Due to the small size of the core and low burn up of the fuel, the disposal of fission product heating was not an issue. The concrete shielding was penetrated by a number of holes enabling neutron beams to be obtained for the purpose of irradiating samples and several pipes that enabled samples in sample carriers to be inserted into the reactor and subsequently removed to the adjoining radiochemical laboratory for study.

Operations

The construction works started in 1962 and went critical on 7 July 1964. In later years the reactor was rated at 300 kW thermal however originally the output was 100 kW thermal. A study was undertaken (around 1980) to investigate increasing the power to 1 MW thermal; however, this was deemed to be too difficult and the plans were abandoned.

Decommissioning

Decommissioning work began in 1992 and was finished in 2006. The reactor fuel being reprocessed. The nuclear waste produced during the dismantling operations was moved to Sellafield for permanent storage.

References

{{authority control Argonaut class reactor Buildings and structures in Warrington Buildings at the University of Manchester Former nuclear research institutes History of Warrington Nuclear research institutes in the United Kingdom Nuclear research reactors Research institutes in Cheshire University of Liverpool