Analysis of calibration data for the uranium active neutron coincidence counting collar with attention to errors in the measured neutron coincidence rate

Croft, Stephen; Burr, Thomas Lee; Favalli, Andrea; Nicholson, Andrew

doi:10.1016/j.nima.2015.11.154

Title: Analysis of calibration data for the uranium active neutron coincidence counting collar with attention to errors in the measured neutron coincidence rate

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Abstract

The declared linear density of ²³⁸U and ²³⁵U in fresh low enriched uranium light water reactor fuel assemblies can be verified for nuclear safeguards purposes using a neutron coincidence counter collar in passive and active mode, respectively. The active mode calibration of the Uranium Neutron Collar - Light water reactor fuel (UNCL) instrument is normally performed using a non-linear fitting technique. The fitting technique relates the measured neutron coincidence rate (the predictor) to the linear density of ²³⁵U (the response) in order to estimate model parameters of the nonlinear Parte equation, which traditionally is used to model the calibration data. Alternatively, following a simple data transformation, the fitting can also be performed using standard linear fitting methods. This article compares performance of the nonlinear technique to the linear technique, using a range of possible error variance magnitudes in the measured neutron coincidence rate. We develop the required formalism and then apply the traditional (nonlinear) and alternative approaches (linear) to the same experimental and corresponding simulated representative datasets. Here, we find that, in this context, because of the magnitude of the errors in the predictor, it is preferable not to transform to a linear model, and it is preferable notmore »« less

Authors:

Croft, Stephen ^[1];

^[2];

^[3]; Nicholson, Andrew ^[1]

Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
International Atomic Energy Agency (IAEA), Vienna (Austria)
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

Publication Date:: Thu Dec 10 00:00:00 EST 2015

Research Org.:: Los Alamos National Laboratory (LANL), Los Alamos, NM (United States); Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)

Sponsoring Org.:: USDOE

OSTI Identifier:: 1457267

Alternate Identifier(s):: OSTI ID: 1348316; OSTI ID: 1359628

Report Number(s):: LA-UR-15-27447
Journal ID: ISSN 0168-9002; TRN: US1901340

Grant/Contract Number:: AC52-06NA25396; AC05-00OR22725

Resource Type:: Accepted Manuscript

Journal Name:: Nuclear Instruments and Methods in Physics Research. Section A, Accelerators, Spectrometers, Detectors and Associated Equipment

Additional Journal Information:: Journal Volume: 811; Journal Issue: C; Journal ID: ISSN 0168-9002

Publisher:: Elsevier

Country of Publication:: United States

Language:: English

Subject:: 11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS; 46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY; Neutron Collar; Fresh LWR Fuel Assay; Linear Regression; Errors in Predictor; Neutron collar; Fresh LWR fuel assay; Linear regression; Errors in predictor

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                    Croft, Stephen, Burr, Thomas Lee, Favalli, Andrea, and Nicholson, Andrew. Analysis of calibration data for the uranium active neutron coincidence counting collar with attention to errors in the measured neutron coincidence rate.  United States: N. p., 2015. 
Web.  doi:10.1016/j.nima.2015.11.154.

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                    Croft, Stephen, Burr, Thomas Lee, Favalli, Andrea, & Nicholson, Andrew. Analysis of calibration data for the uranium active neutron coincidence counting collar with attention to errors in the measured neutron coincidence rate.  United States.  https://doi.org/10.1016/j.nima.2015.11.154

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                    Croft, Stephen, Burr, Thomas Lee, Favalli, Andrea, and Nicholson, Andrew. Thu .  
"Analysis of calibration data for the uranium active neutron coincidence counting collar with attention to errors in the measured neutron coincidence rate".  United States.  https://doi.org/10.1016/j.nima.2015.11.154.  https://www.osti.gov/servlets/purl/1457267.

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@article{osti_1457267,

  title        = {Analysis of calibration data for the uranium active neutron coincidence counting collar with attention to errors in the measured neutron coincidence rate},

  author       = {Croft, Stephen and Burr, Thomas Lee and Favalli, Andrea and Nicholson, Andrew},

  abstractNote = {The declared linear density of 238U and 235 U in fresh low enriched uranium light water reactor fuel assemblies can be verified for nuclear safeguards purposes using a neutron coincidence counter collar in passive and active mode, respectively. The active mode calibration of the Uranium Neutron Collar - Light water reactor fuel (UNCL) instrument is normally performed using a non-linear fitting technique. The fitting technique relates the measured neutron coincidence rate (the predictor) to the linear density of 235U (the response) in order to estimate model parameters of the nonlinear Parte equation, which traditionally is used to model the calibration data. Alternatively, following a simple data transformation, the fitting can also be performed using standard linear fitting methods. This article compares performance of the nonlinear technique to the linear technique, using a range of possible error variance magnitudes in the measured neutron coincidence rate. We develop the required formalism and then apply the traditional (nonlinear) and alternative approaches (linear) to the same experimental and corresponding simulated representative datasets. Here, we find that, in this context, because of the magnitude of the errors in the predictor, it is preferable not to transform to a linear model, and it is preferable not to adjust for the errors in the predictor when inferring the model parameters.},

  doi          = {10.1016/j.nima.2015.11.154},

  journal      = {Nuclear Instruments and Methods in Physics Research. Section A, Accelerators, Spectrometers, Detectors and Associated Equipment},

  number       = C,

  volume       = 811,

  place        = {United States},

  year         = {Thu Dec 10 00:00:00 EST 2015},

  month        = {Thu Dec 10 00:00:00 EST 2015}

}

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