Centrifugally Tensioned Metastable Fluid Detectors for Detection of Alpha, Neutron, and Other Signatures of Special Nuclear Materials in NuclearWaste Reprocessing Facilities

Jeffrey Alexander Webster, Purdue University

Abstract

This dissertation covers advancements made to the technology of Centrifugally Tensioned Metastable Fluid radiation Detectors (CTMFDs) as well as potential application to nuclear waste reprocessing facilities. The CTMFD operates by stretching a fluid below vacuum pressure using centrifugal mechanical tension to destabilize the fluid to the point where radiation interactions in the fluid can cause rapid nucleation and boiling of the fluid. This interaction manifests as the rapid expansion of a vapor cavity within the detector that is visible to the naked eye and audible without amplification. This detection mechanism, while simple to observe, has opened up a wide variety of radiation detection applications. The detection process involves formation of a nanometer scale bubble from radiation interaction, then grown to the macro scale by the properties and tension of the fluid. The bubble growth, and thereby, the detection process is threshold based allowing the CTMFD to be tuned to allow detection of differing types of radiation or energy of particles. Typically the CTMFD is used to detect external neutron sources and internal alpha emitting sources. This work expanded those detection options to include internal fission events, both spontaneous and externally induced. The CTMFD has been previously shown to have effective discrimination of γ photons, and this capability was further demonstrated as part of this work. Also demonstrated for the first time was the ability to completely ignore β radiation inside the CTMFD. This is advantageous for measuring weak α signatures in the intense β/γ environment of spent nuclear fuel. A large portion of the work in this dissertation involved development of the CTMFD and its capabilities to make it more ready for field operation. Included in this effort was the creation of several prototypes of application specific versions of the CTMFD, including a hand held version, a table top portable version, and a stationary multi-detector spectrometer version. After development of the hardware, additional capabilities were demonstrated or explored, including: operation under a wide range of temperatures; impact of extreme radiation dose to detector; rudimentary neutron dose monitoring; application specific fluid selection; and thermal neutron detection. These prototypes and capabilities were developed with the end goal of applying CTMFD technology to the field of special nuclear material safeguards and security, especially within a nuclear waste reprocessing facility. Simulation work was done to first determine the radiation environment at various locations within a reprocessing facility followed by predictions for how a CTMFD might be able to measure actinides within various processing streams. A framework was put together for organizing the current CTMFD capabilities associated with the radiation signatures at various locations in reprocessing facilities. This information was compiled and suggestions made for CTMFD measurements under various conditions. This framework resulted in a variety of potential measurements that are not easily accomplished by conventional methods. Potential measurements include, but are not limited to, neutron measurement of spent fuel while ignoring γ radiation, measurement of fissile material by active interrogation, measurement of several plutonium isotopes by various methods, measurement of curium and curium contamination at several locations in the facility, and measurement of actinide holdup in nuclear material processing facilities. This framework was applied to both the UREX process being developed in the United States and the PUREX process currently being used elsewhere in the world. In addition to the suggested framework for actinide detection, insights are offered for how CTMFD technology may be beneficial to the area of nuclear safeguards in general.

Degree

Ph.D.

Advisors

Taleyarkhan, Purdue University.

Subject Area

Nuclear engineering|Nuclear physics

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