Search Results

You are looking at 1 - 6 of 6 items for

  • Author or Editor: T. Johnson x
  • Refine by Access: All Content x
Clear All Modify Search

Abstract  

In the United States today, legally defensible data is needed for environmental assessments, waste characterization, and dose assessments. A closer look at the raw data and interpretation of the results can reveal other problems that affect the data usability based on the project data quality objectives. The common problems include the following: incomplete sample dissolution, loss of volatile radionuclides during sample preparation, difficulties in aliquot subsampling during sample preparation, lack of a sample-specific chemical recovery mechanisms, use of an inappropriate sample-specific chemical recovery mechanism, not using enough of the sample-specific chemical recovery mechanism to obtain sufficient counting statistics for the recovery result, gamma-spectrometry misidentification, use of incorrect abundances or intensities, and incomplete separation of isotopes prior to alpha-spectroscopy analysis. These problems can result in the estimation or rejection of the results. Although most of these problems can be avoided, no improvement in their frequency has been noticed over time. This paper is written in an attempt to call attention to the typical problems in hopes that the contract laboratories as well as the government laboratories will review their practices to avoid these problems.

Restricted access

Abstract  

There is often a need to calculate isotopic uranium activities from total uranium mass or gamma spectrometry measurement data. This calculation is based on a model of the relationship of the234U activity to that of235U since both are enriched together in the normal gaseous diffusion enrichment process. This paper presents equations for calculating these activities that have been developed from several sources of data. These equations have been used for several characterization studies and have produced very good results when compared to results from actual isotopic uranium analyses. However, because the variability in the model causes significant uncertainty in the calculated results, alpha-spectrometry is recommended for critical applications.

Restricted access

Abstract  

An abbreviated NAA procedure has been developed to fingerprint obsidian artifacts in the Mesoamerican region. Despite the large number of available sources, an NAA procedure, which relies on producing short-lived isotopes, has been applied with a success rate greater than 90 percent. The abbreviated NAA procedure is rapid and cost competitive with the XRF technique more often applied in obsidian sourcing. Results from the analysis of over 1,200 obsidian artifacts from throughout Mesoamerica are presented.

Restricted access

Abstract  

Neutron activation analysis data quality must be validated to serve evidentiary purposes for environmental restoration and health protection projects. This paper gives a basis for determining the technical validity of neutron activation analysis data.

Restricted access

Abstract

Evolutionary theory based research has examined how sexual access and emotional access affect mate selection. However, evolutionary theory based research has not examined how deficits in sexual access and emotional access affect relationship termination decisions. The present research sought to fill this void with two studies examining the questions of whether or not: a lack of sexual access is more likely to lead men to end a relationship, and whether or not a lack of emotional access is more likely to lead women to end a relationship. Based on prior research investigating divorce, sexual infidelity, and male and female mate selection preferences, men were expected to be more likely to end a relationship due to a lack of sexual access while women were expected to be more likely to end a relationship due to a lack of emotional access. The results were consistent with the hypothesis for women. Both men and women were more likely to terminate their relationships due to lack of emotional access. These results are discussed in terms of parental investment concerns, commitment loss, and prior research.

Restricted access
Journal of Radioanalytical and Nuclear Chemistry
Authors: L. Tandon, E. Hastings, J. Banar, J. Barnes, D. Beddingfield, D. Decker, J. Dyke, D. Farr, J. FitzPatrick, D. Gallimore, S. Garner, R. Gritzo, T. Hahn, G. Havrilla, B. Johnson, K. Kuhn, S. LaMont, D. Langner, C. Lewis, V. Majidi, P. Martinez, R. McCabe, S. Mecklenburg, D. Mercer, S. Meyers, V. Montoya, B. Patterson, R. Pereyra, D. Porterfield, J. Poths, D. Rademacher, C. Ruggiero, D. Schwartz, M. Scott, K. Spencer, R. Steiner, R. Villarreal, H. Volz, L. Walker, A. Wong, and C. Worley

Abstract  

The goal of nuclear forensics is to establish an unambiguous link between illicitly trafficked nuclear material and its origin. The Los Alamos National Laboratory (LANL) Nuclear Materials Signatures Program has implemented a graded “conduct of operations” type analysis flow path approach for determining the key nuclear, chemical, and physical signatures needed to identify the manufacturing process, intended use, and origin of interdicted nuclear material. This analysis flow path includes both destructive and non-destructive characterization techniques and has been exercized against different nuclear materials from LANL’s special nuclear materials archive. Results obtained from the case study will be presented to highlight analytical techniques that offer the critical attribution information.

Restricted access