Plutonium Recycle Test Reactor

Plutonium Recycle Test Reactor was an experimental nuclear reactor constructed at the Hanford Site in Washington state. Operated for the United States Atomic Energy Commission by General Electric, its primary mission was to investigate the practical use of plutonium as a fuel in civilian light-water reactors. The facility provided critical data on fuel performance, reactor physics, and the economic potential of recycling plutonium from spent nuclear fuel.

History and purpose

The reactor was conceived during the mid-1950s amid growing interest in the civilian nuclear power industry and the potential fuel cycles for future reactors. Following the Atoms for Peace initiative, the United States Atomic Energy Commission sought to demonstrate the viability of using plutonium, a byproduct of weapons production and uranium fission, in commercial power reactors. The project was authorized and construction began in 1958 at the Hanford Site, a location with extensive infrastructure from the Manhattan Project. The reactor achieved criticality in 1960 under the management of the prime contractor, General Electric. Its operation was part of a broader national strategy to develop advanced reactor technologies and assess the long-term fuel supply for a growing nuclear economy, complementing other experimental programs like those at the Argonne National Laboratory.

Design and operation

The reactor was a unique, dual-cycle boiling water reactor designed for maximum experimental flexibility. It featured a compact core housed within a thick stainless steel pressure vessel and utilized light water as both coolant and moderator. A key design innovation was its ability to operate in either a direct-cycle mode, where steam produced in the core drove a turbine, or an indirect-cycle mode for experimental testing. The core itself was relatively small, allowing for high neutron flux to accelerate materials testing. Primary operational control was achieved through the use of boron-stainless steel control rods, and the entire system was contained within a robust containment building designed to stringent safety standards of the era. The thermal power rating was approximately 70 MW_th.

Fuel cycle and plutonium use

The central experimental focus was on mixed-oxide fuel, where plutonium dioxide was blended with uranium dioxide to fabricate reactor fuel elements. This directly supported the concept of a "closed" nuclear fuel cycle, where plutonium recovered from spent fuel via reprocessing plants like the adjacent Hanford Purex plant could be reintroduced into reactors. The program tested various fuel rod designs and plutonium isotopic compositions, including material from both production reactors and newer sources. Investigations covered the entire fuel cycle, from fabrication and irradiation behavior to post-irradiation examination, providing essential data on neutron economy, fission product behavior, and the long-term stability of MOX fuel under typical light-water reactor operating conditions.

Experimental programs and findings

The experimental portfolio was extensive, encompassing reactor physics, fuel development, and safety studies. Key programs included precise measurements of plutonium's nuclear characteristics, such as its neutron cross section and fission yield, within a thermal spectrum. Numerous fuel assemblies were irradiated to high burnup to study swelling, gas release, and cladding interaction. The reactor also hosted loop experiments that simulated different coolant chemistries and accident scenarios. Findings confirmed the technical feasibility of using plutonium-based fuels in conventional reactors but also identified significant challenges, including more complex reactor control due to plutonium's different neutronic properties and higher rates of fission gas production compared to standard uranium fuel.

Decommissioning and legacy

Operations ceased in 1972, driven by shifting national priorities away from plutonium recycle due to nuclear proliferation concerns, economic factors, and the decision by the United States to indefinitely defer commercial reprocessing. The reactor was defueled and placed in a long-term safe storage configuration. Major decommissioning activities, including the removal of the reactor vessel and internal components, were carried out in subsequent decades as part of the larger Hanford Site cleanup managed by the United States Department of Energy. The legacy of the reactor endures in the extensive dataset it produced, which informed international MOX fuel programs in countries like France, Japan, and the United Kingdom. Its history remains a key case study in the technological and policy complexities of nuclear fuel cycle development.

Category:Experimental nuclear reactors Category:Hanford Site Category:Nuclear technology in the United States Category:General Electric