Laser-spectroscopic techniques for monitoring releases from nuclear fuel cycle objects

Abstract

This is a study of the feasibility of and equipment layout for reliable, accurate, and high-speed detection of releases of dangerous substances from nuclear fuel cycle objects by various local and remote laser diagnostic techniques.One of the most dangerous components of accidental releases from objects in the nuclear fuel cycle is volatile uranium hexafluoride, the most chemically active of the known fluorine-containing compounds of uranium. Uranium hexafluoride releases are accompanied by a rapid increase in the atmospheric concentration of hydrogen fluoride and the formation of uranyl fluoride, UO 2 F 2 . In addition, the surfaces of equipment get contaminated by uranium or other characteristic materials, as does waste water. In practice, IAEA inspectors analyze releases, waste water, and water used for washing equipment to discover hidden efforts to enrich uranium or other nuclear technologies.Recently, special attention has been devoted to studies of atmospheric chemistry in a search for the vapor of heavy water, which is a basic constituent of liquid and gaseous releases from most nuclear power stations and chemical plants for the enrichment and reprocessing of nuclear fuel. The presence of superheavy water vapor in the atmosphere may be evidence of plutonium production. Thus, monitoring the atmosphere for heavy and superheavy water vapor is of great interest as it can be used both to establish the degree of contamination of the environment and to detect unsanctioned nuclear weapons production activity.These things have all stimulated a search for new techniques and the development of data and measurement systems for high-speed monitoring of the state of the air basins of large industrial centers, the waters in and surrounding lakes, rivers, seas, and oceans, large stands of plant growth, etc. In creating such systems, laser diagnostic techniques have come to be of ever greater interest, since they can operate at a distance (up to several km), with high sensitivity (ppb) and obtain information about the environment under study in real-time (fractions of a second) [1].In this paper, we describe some techniques and the associated apparatus for reliable, accurate, and high-speed detection of trace releases of dangerous substances at nuclear fuel cycle objects, in both local and remote probe variants employing laser diagnostic techniques.Uranium Hexafluoride. During an accidental release, it interacts actively with the atmospheric humidity to form UO 2 F 2 , which decomposes into uranyl fluoride UOF 4 . The hydrolysis of uranium hexafluoride is usually described by the equations

Excited States and Luminescent Properties of UO2F2 and Its Solvated Complexes in Aqueous Solution

“…It is well-known that the reaction of atmospheric water with leaked UF 6 produces a series of uranyl fluoride complexes, among which UO 2 F 2 is the primary uranium species . The study of luminescence of UO 2 F 2 is fascinating, because the luminescence of UO 2 F 2 is exploited to detect UF 6 leaking with high sensitivity and rapidity . In addition, the enhancement of uranyl luminescence in aqueous solution via fluoride complexation has been explored for a long time, and the uranyl fluoride species (i.e., UO 2 F 2 , UO 2 F 3 – , and UO 2 F 4 2– ) were proposed to account for the uranyl luminescence properties (e.g., lifetime) .…”

Effects of ligands on excitation energies of [UO2X4]2− and UO2X2 (X = F, Cl) with the equation‐of‐motion coupled‐cluster theory

“…The cc‐pwCVTZ‐PP basis set for U [89], and the aug‐cc‐pVTZ basis set for O, Cl, and F are adopted in our calculations [90,91]. In calculating vertical EEs, experimental geometries for [UO 2 X 4 ] [2–9,22]and those optimized with CCSD(T) for UO 2 X 2 [69,70] listed in Table 2 are adopted. To investigate effects of ligands on EEs of these molecules, EEs of bare uranyl and uranyl embedded in point‐charges are also calculated.…”

“…Among uranyl compounds, uranyl halides are useful starting materials for the synthesis of a wide range of compounds, and they have been the subject of numerous experimental and theoretical investigations [1,2]. In addition, luminescent properties of uranyl halides have many practical applications, such as enhancing the luminescent intensity of uranyl in aqueous solution [3–8], and detecting the leaking of UF 6 with high sensitivity and rapidity through UO 2 F 2 [9]. Studying excitation energies (EEs), electronic structures and coordination structures of uranyl and uranyl halides are particularly useful in investigating spectroscopic and luminescence properties and photochemical reactions of the involved species, as well as probing uranyl compounds.…”

Ultrafast Laser Filament-induced Fluorescence Spectroscopy of Uranyl Fluoride

“…Detection of UF 6 , along with the other byproducts of enrichment, namely UO 2 F 2 and HF, has been proposed via several techniques, including remote LIDAR 3 , air sampling methods that use particle filtration 2 , 4 , and air sampling with laser ablation-laser absorbance ratio spectrometry (LAARS) 5 , 6 , laser-induced breakdown spectroscopy (LIBS) 7 , and laser-induced fluorescence (LIF) spectroscopy 6 , 8 – 11 . UO 2 F 2 proves the most promising tracer due to its chemical stability.…”