Tension metastable fluid detector for real-time detection of actinides and extension to monitoring of UREX+3 process streams
Abstract
Tension metastable fluid states offer unique potential for radical transformation in radiation detection capabilities. States of tension metastability may be obtained in tailored resonant acoustic systems such as the acoustic tension metastable fluid detector (ATMFD) system or via centrifugal force based systems such as the centrifugal tension metastable fluid detector (CTMFD) system; both under development at Purdue University. Tension metastable fluid detector (TMFD) systems take advantage of the weakened intermolecular bonds of liquids in sub-vacuum states. Nuclear particles incident onto sufficiently tensioned fluids can nucleate critical size vapor bubbles which grow from nanoscales and are then possible to see, hear, and record with unprecedented efficiency and capability. Past work has shown the ability of TMFD systems to detect neutrons with energies spanning eight orders of magnitude with 95%+ intrinsic efficiency while remaining insensitive to gamma photons and also giving directional information on the source of the radiation. This dissertation describes research results with acetone-based CTMFD systems for use in the detection of key actinide isotopes constituting special nuclear material (SNM) via their alpha decay signatures and neutron emission. The ability of CTMFD systems to conduct alpha spectroscopy over the range of ∼4-6 MeV which spans the alpha decay energies from the actinides of interest in spent nuclear fuel (SNF) reprocessing was demonstrated. Along with demonstrated spectroscopic capabilities, tests in CTMFD systems developed and used for this work have demonstrated the ability to detect, differentiate,and accurately determine alpha-decay activity (at ∼100% efficiency) of Pu-238 and Pu-239 at concentrations of ∼0.05 ppt and ∼15 ppt respectively (which is unprecedented and x10 to x100 more sensitive than from our state-of-the-art Beckman LS6500 liquid scintillation spectrometer). An inherent capability of TMFD systems concerns on demand tailoring of fluid tension levels allowing for energy discrimination and spectroscopy. This appears especially useful to detect the key isotopes of U as well as isotopes of the transuranic elements Pu, Np, Am, and Cm that are at different stages of SNF reprocessing (i.e., UREX+). The work of this dissertation has also demonstrated the capability of the TMFD technology for differentiating the alpha emission signature of Pu-238 from Am-241; this is transformational since most alpha particle detectors can not differentiate between the 5.49 MeV and 5.485 MeV alpha decay energies of these two isotopes which, unfortunately, build up together. A detailed set of ORIGEN-S code based modeling simulations were conducted and successfully benchmarked against post-irradiation-examination data of SNFs. Simulations were conducted for deriving estimates and trends of isotopic buildup in SNF as a function of power history, burnup, enrichment, and cooling times. Key figures of merit for trends were derived to use together with TMFD technology for successful real-time detection of actinides at various stages of reprocessing, including at the crucial front-end. An algorithm for general application in SNF reprocessing plants has been developed along with a framework for field implementation. This framework combines the use of TMFD technology (for active interrogation of actinide bearing streams for their alpha activity, together with passive neutron interrogation) with continually refined analytic assessments using the ORIGEN-S code in real-time to determine the various quantities of isotopes of Am, Cm, and Pu.
Degree
Ph.D.
Advisors
Taleyarkhan, Purdue University.
Subject Area
Nuclear engineering
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