Evaluation for ammonium bifluoride dissolution for application to post-detonation nuclear forensics and rare Earth element extraction

Abstract

[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT REQUEST OF AUTHOR.] If a nuclear device were to be used in an act of terrorism, prompt nuclear forensic analysis of the post-detonation debris is crucial in order to provide the origin of the device so that an appropriate response may be developed. Conventional dissolution chemistries can be employed to assist with such an effort, however they often require hazardous chemicals, specialized facilities, and long processing times. In this research, methodologies using ammonium bifluoride (NH4HF2 or ABF) were developed to improve the dissolution of samples for nuclear forensic analysis by eliminating or reducing hazardous chemicals and reducing the time of analysis. Fusion, sonication, mechanical, and microwave assisted methods were evaluated on their ability to fully recover elements from a wide range of sample matrices. These included geologic reference materials, urban canyon matrix, NIST Surrogate Post-detonation Urban Debris (SPUD), and trinitite, the debris produced after the test of the first atomic bomb. It is shown that ammonium bifluoride dissolution methods are able to successfully digest a wide range of sample matrices and provide high recoveries for a wide range of elements. Additionally, ammonium bifluoride was evaluated for the ability to extract rare-earth elements from coal fly ash. These elements are critical to many applications such as defense, energy, and electronics. The United States currently has limited domestic production of rare-earth elements, and coal fly ash may provide an alternative source to mining. Current rare-earth extraction techniques require harsh conditions and chemicals and so an ammonium bifluoride and nitric acid leaching procedure was developed as an alternative to these methods. Quantitative recoveries of rare-earth elements were obtained from reference material coal fly ash. This work demonstrates the applicability of ABF methodologies to two crucial areas of research.