The Development of Lithium Tetraborate Compounds for Thermal Neutron Detection

Due to the shortage of 3He [helium-3], the goal of this project was to develop replacement materials for slow neutron detection in mixed radiation fields. The U.S. Department of Homeland Security (DHS) indicated that replacement materials should have an absolute neutron efficiency of 2.5 cps/ng of 252Cf (Californium-252) and a neutron/gamma discrimination intrinsic efficiency of 1 x 10-6 [one gamma-ray response in a million counts]. In this work, the use of amorphous lithium tetraborate (Li2B4O7:Ce) is analyzed as a thermal neutron detector. Also discussed is the synthesis of the lithium tetraborate, using 6Li [lithium-6], to form a crystalline powder that is heated simultaneously with cerium oxide (CeO2) and excess boric acid to produce an optically clear glass. In this study, the structure of glass was probed, the abnormal reduction of Ce4+ [tetravalent cerium] to Ce3+ [trivalent cerium] observed in the fluorescence peak at 360 nm, and irradiation studies with alpha particles, beta particles, gamma-rays, and neutrons were performed. The resulting material was shown to have a light yield of 550 photons/neutron, which is 8% the light output of GS-20, a lithiated glass

Contribution of natural terrestrial sources to the total radiation dose to man

Ph.D.Geoffrey G. Eichhol

Laser-Induced Plasma Analysis for Surrogate Nuclear Debris

This work identifies analytical lines in laser-induced plasma for chemical analyses of major elements found in surrogate nuclear debris. These lines are evaluated for interferences and signal strength to insure they would be useful to measure relative concentrations. Compact, portable instruments are employed and can be included as part of a mobile nuclear forensics laboratory for field screening of nuclear debris and contamination. The average plasma temperature is measured using the well-established Boltzmann plot technique, and plasma\u27s average electron density is determined using empirical formulae based on Stark broadening of the H-alpha line. These measurements suggest existence of partial local thermal equilibrium

Modern Advancements in Post-Detonation Nuclear Forensic Analysis

Deterring nuclear terrorism is a critical national asset to support the preclusion of non-state actors from initiating a nuclear attack on the United States. Successful attribution of a detonated nuclear weapon allows for timely responsive measures that prove essential in the period following a nuclear event. In conjunction with intelligence and law enforcement evidence, the technical nuclear forensics (TNF) post-detonation community supports this mission through the development and advancement of expertise to characterize weapon debris through a rapid, accurate, and detailed approach. Though the TNF field is young, numerous strides have been made in recent years toward a more robust characterization capability. This work presents modern advancements in post-detonation expertise over the last ten years and demonstrates the need for continued extensive research in this field

Exploring Rapid Radiochemical Separations at the University of Tennessee Radiochemistry Center of Excellence

The University of Tennessee formed its Radiochemistry Center of Excellence (RCoE) in 2013 with support from the U.S. National Nuclear Security Administration. One of the major thrusts of the RCoE is to develop deeper understanding of rapid methods for radiochemical separations that are relevant to both general radiochemical analyses as well as post-detonation nuclear forensics. Early work has included the development and demonstration of rapid separations of lanthanide elements in the gas phase, development of a gas-phase separation front-end for ICP-TOF-MS analysis, and the development of realistic analytical surrogates for post-detonation debris to support methods development