Rapid Dissolution for Destructive Assay of Nuclear Melt Glass

This study evaluates four methods for dissolving complex glassy debris resulting from nuclear detonations. The samples of interest simulate the glassy debris generated from a nuclear detonation’s fireball coming in contact with solid masses. Each method attempts to achieve dissolution through different approaches involving either acid digestion, alkaline digestion, or molten salt fusion. Two of the four methods were modified to retain all elements of the debris or surrogate debris. This retention is critical to the proportional relationships used in identifying fuel types and designs of nuclear weapons. Analysis is conducted with an inductively coupled time of flight mass spectrometer (ICP-TOF-MS) to provide exact elemental composition and yield for each dissolution method. The samples analyzed were trinitite (trin), surrogate trinitite formulation (STF), urban surrogate melt glass (NYC), and MAPEP MaS 32 (MAPEP). All samples have well known elemental compositions except for trinitite, however there are published compositional norms that are predicted for the trinitite. The four methods used were a Lithium Fusion (Larivière Method), a Sodium Hydroxide Fusion (Maxwell Method), an Acidic Digestion (Eppich Method), and a Modified Rapid Acidic Digestion (Auxier Method). Outcomes for the Lithium and the Maxwell Method failed to produce meaningful results due to the mass difference in fusion material compared to the isotopes of interest in the sample material mass. At the maximum concentration limit of 25-35 parts per thousand the mass spectrometer could not meaningfully detect the barium or uranium in any of the samples. The acidic digestion, and the Auxier Method both showed success with detecting appropriate levels of uranium, barium, and other lighter elements. The Auxier Method shows the best results when compared to ideal 100% yield from each sample. For Auxier’s Method, uranium averages a yield of 5%±.02% of ideal. This is 614% above the acidic digestion and over 1200% above the other methods. For barium, the Auxier Method averages a yield of 9% of ideal. This is 595% above the acidic digestion and 4300% above the other methods. The Auxier Method demonstrates repeatability across three runs of each sample and sample independence as percent yields were similar across sample types

Novel Fission Track Detection for Identification and Characterization of Special Nuclear Materials

Fission track detection and analysis is used primarily in nuclear safeguards to identify special nuclear material. Identification of isotopic ratios is a crucial step in understanding the intended use of nuclear material and the nature of the materials production cycle. Unfortunately, this methodology uses etchable track detectors that require significant expertise and intensive labor to process. This study developed a novel method using lithium fluoride (LiF) as a fluorescing nuclear track detector to conduct fission track analysis for isotopic prediction of uranium enrichment. Individual latent tracks produced by fission products were observed in LiF for the first time. These tracks were identified using fluorescence microscopy with a confocal laser scanning microscope. Specifically, lithium fluoride’s F₂ and F₃⁺ defects were excited and observed for fluorescing emission. These observations required the use of highly sensitive detectors that could maintain at least a one to ten signal to noise ratio while detecting single photon signal. Fission tracks were verified with concurrent ²⁵²Cf alpha tracks and agreement with variations in exposure times. Experiments with uranium fuel glued to LiF detectors were used to predict enrichment. These samples were exposed to 10¹⁴ neutrons in a custom irradiator and then particles were characterized based on the number of tracks observed by the confocal laser scanning microscope. Predictions of uranium isotopes required calculation of particle mass contributing significantly to error. Seven of ten particles fell with error of prediction, two of which were depleted uranium samples and had predicted track counts of less than one per fuel grain. This work proves the viability for a new method of identifying particles with fission track analysis. It reduces the work hours required to analyze an environmental sample for fissionable material by removing the need to etch traditional solid state nuclear track detectors

Joint or Shared Accountability: Issues and Options

Responsible and responsive government depends on effective accountability – at all levels within the state. To this end, democratic governments have typically established strong vertical or hierarchical accountability relationships. New Zealand has been no exception. Indeed, the state sector reforms introduced in the late 1980s emphasised formal, vertical, straight-line accountability. Yet some of the work of government involves collaboration or joint working across multiple agencies. This implies the need for shared and horizontal accountability. It also casts doubt on the wisdom of relying too heavily on vertical accountability, not least because this may undermine joint working. How, then, should accountabilities be managed in the context of shared or joint working across agencies and what principles and considerations should guide policy makers when designing such accountability arrangements? With these issues in mind, this paper begins with an exploration of certain key concepts – vertical and horizontal accountability, responsibility, answerability and blame – and considers the limitations of vertical models of accountability within a Westminster-type parliamentary democracy. It then explores the nature and problems associated with joint working in the state sector where accountability for particular activities or outcomes is shared between two or more organisations. The paper argues that there are certain ‘hard’ factor and ‘soft factors’ that must be addressed to enable joint working. It is also argued that four key issues need to be considered when designing the institutional and associated accountability arrangements for joint working: depth, co-ordination and alignment, complexity, and separability. The paper concludes by exploring the ‘levers’ available to accommodate new ways of working across public agencies