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Title: A Piecewise Local Partial Least Squares (PLS) Method for the Quantitative Analysis of Plutonium Nitrate Solutions

Here, we have developed a piecewise local (PL) partial least squares (PLS) analysis method for total plutonium measurements by absorption spectroscopy in nitric acid-based nuclear material processing streams. Instead of using a single PLS model that covers all expected solution conditions, the method selects one of several local models based on an assessment of solution absorbance, acidity, and Pu oxidation state distribution. The local models match the global model for accuracy against the calibration set, but were observed in several instances to be more robust to variations associated with measurements in the process. The improvements are attributed to the relative parsimony of the local models. Not all of the sources of spectral variation are uniformly present at each part of the calibration range. Thus, the global model is locally overfitting and susceptible to increased variance when presented with new samples. A second set of models quantifies the relative concentrations of Pu(III), (IV), and (VI). Standards containing a mixture of these species were not at equilibrium due to a disproportionation reaction. Therefore, a separate principal component analysis is used to estimate of the concentrations of the individual oxidation states in these standards in the absence of independent confirmatory analysis. The PLmore » analysis approach is generalizable to other systems where the analysis of chemically complicated systems can be aided by rational division of the overall range of solution conditions into simpler sub-regions.« less
Authors:
ORCiD logo [1] ;  [1] ;  [1]
  1. Savannah River National Lab., Aiken, SC (United States)
Publication Date:
Report Number(s):
SRNL-STI-2016-00697
Journal ID: ISSN 0003-7028
Grant/Contract Number:
AC09-08SR22470
Type:
Accepted Manuscript
Journal Name:
Applied Spectroscopy
Additional Journal Information:
Journal Volume: 71; Journal Issue: 12; Journal ID: ISSN 0003-7028
Publisher:
Society for Applied Spectroscopy
Research Org:
Savannah River Site (SRS), Aiken, SC (United States)
Sponsoring Org:
USDOE
Country of Publication:
United States
Language:
English
Subject:
47 OTHER INSTRUMENTATION; Partial least squares; PLS; process analysis; plutonium; absorbance; classification
OSTI Identifier:
1439429