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Title: Utility of Monte Carlo Modelling for Holdup Measurements.

Abstract

Non-destructive assay (NDA) measurements performed to locate and quantify holdup in the Oak Ridge K25 enrichment cascade used neutron totals counting and low-resolution gamma-ray spectroscopy. This facility housed the gaseous diffusion process for enrichment of uranium, in the form of UF{sub 6} gas, from {approx} 20% to 93%. Inventory of {sup 235}U inventory in K-25 is all holdup. These buildings have been slated for decontaminatino and decommissioning. The NDA measurements establish the inventory quantities and will be used to assure criticality safety and meet criteria for waste analysis and transportation. The tendency to err on the side of conservatism for the sake of criticality safety in specifying total NDA uncertainty argues, in the interests of safety and costs, for obtaining the best possible value of uncertainty at the conservative confidence level for each item of process equipment. Variable deposit distribution is a complex systematic effect (i.e., determined by multiple independent variables) on the portable NDA results for very large and bulk converters that contributes greatly to total uncertainty for holdup in converters measured by gamma or neutron NDA methods. Because the magnitudes of complex systematic effects are difficult to estimate, computational tools are important for evaluating those that are large.more » Motivated by very large discrepancies between gamma and neutron measurements of high-mass converters with gamma results tending to dominate, the Monte Carlo code MCNP has been used to determine the systematic effects of deposit distribution on gamma and neutron results for {sup 235}U holdup mass in converters. This paper details the numerical methodology used to evaluate large systematic effects unique to each measurement type, validates the methodology by comparison with measurements, and discusses how modeling tools can supplement the calibration of instruments used for holdup measurements by providing realistic values at well-defined confidence levels for dominating systematic effects.« less

Authors:
;  [1]
  1. Phyllis A.
Publication Date:
Research Org.:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
977994
Report Number(s):
LA-UR-05-5102
TRN: US1004178
Resource Type:
Conference
Resource Relation:
Conference: Institute of Nuclear Materials Management 46th Annual Meeting, July 10-14, 2005, Phoenix, Arizona
Country of Publication:
United States
Language:
English
Subject:
11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS; CALIBRATION; CRITICALITY; DECOMMISSIONING; DISTRIBUTION; GASEOUS DIFFUSION PROCESS; NEUTRONS; NUCLEAR MATERIALS MANAGEMENT; SAFETY; SIMULATION; SPECTROSCOPY; URANIUM; WASTES

Citation Formats

Belian, Anthony P, Russo, P A, and Weier, Dennis R. Utility of Monte Carlo Modelling for Holdup Measurements.. United States: N. p., 2005. Web.
Belian, Anthony P, Russo, P A, & Weier, Dennis R. Utility of Monte Carlo Modelling for Holdup Measurements.. United States.
Belian, Anthony P, Russo, P A, and Weier, Dennis R. Sat . "Utility of Monte Carlo Modelling for Holdup Measurements.". United States. https://www.osti.gov/servlets/purl/977994.
@article{osti_977994,
title = {Utility of Monte Carlo Modelling for Holdup Measurements.},
author = {Belian, Anthony P and Russo, P A and Weier, Dennis R.},
abstractNote = {Non-destructive assay (NDA) measurements performed to locate and quantify holdup in the Oak Ridge K25 enrichment cascade used neutron totals counting and low-resolution gamma-ray spectroscopy. This facility housed the gaseous diffusion process for enrichment of uranium, in the form of UF{sub 6} gas, from {approx} 20% to 93%. Inventory of {sup 235}U inventory in K-25 is all holdup. These buildings have been slated for decontaminatino and decommissioning. The NDA measurements establish the inventory quantities and will be used to assure criticality safety and meet criteria for waste analysis and transportation. The tendency to err on the side of conservatism for the sake of criticality safety in specifying total NDA uncertainty argues, in the interests of safety and costs, for obtaining the best possible value of uncertainty at the conservative confidence level for each item of process equipment. Variable deposit distribution is a complex systematic effect (i.e., determined by multiple independent variables) on the portable NDA results for very large and bulk converters that contributes greatly to total uncertainty for holdup in converters measured by gamma or neutron NDA methods. Because the magnitudes of complex systematic effects are difficult to estimate, computational tools are important for evaluating those that are large. Motivated by very large discrepancies between gamma and neutron measurements of high-mass converters with gamma results tending to dominate, the Monte Carlo code MCNP has been used to determine the systematic effects of deposit distribution on gamma and neutron results for {sup 235}U holdup mass in converters. This paper details the numerical methodology used to evaluate large systematic effects unique to each measurement type, validates the methodology by comparison with measurements, and discusses how modeling tools can supplement the calibration of instruments used for holdup measurements by providing realistic values at well-defined confidence levels for dominating systematic effects.},
doi = {},
url = {https://www.osti.gov/biblio/977994}, journal = {},
number = ,
volume = ,
place = {United States},
year = {2005},
month = {1}
}

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