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Title: Thermal Safety Analyses for the Production of Plutonium-238 at the High Flux Isotope Reactor

Abstract

There has been a considerable effort over the previous few years to demonstrate and optimize the production of plutonium-238 ( 238Pu) at the High Flux Isotope Reactor (HFIR). This effort has involved resources from multiple divisions and facilities at the Oak Ridge National Laboratory (ORNL) to demonstrate the fabrication, irradiation, and chemical processing of targets containing neptunium-237 ( 237Np) dioxide (NpO 2)/aluminum (Al) cermet pellets. A critical preliminary step to irradiation at the HFIR is to demonstrate the safety of the target under irradiation via documented experiment safety analyses. The steady-state thermal safety analyses of the target are simulated in a finite element model with the COMSOL Multiphysics code that determines, among other crucial parameters, the limiting maximum temperature in the target. Safety analysis efforts for this model discussed in the present report include: (1) initial modeling of single and reduced-length pellet capsules in order to generate an experimental knowledge base that incorporate initial non-linear contact heat transfer and fission gas equations, (2) modeling efforts for prototypical designs of partially loaded and fully loaded targets using limited available knowledge of fabrication and irradiation characteristics, and (3) the most recent and comprehensive modeling effort of a fully coupled thermo-mechanical approach overmore » the entire fully loaded target domain incorporating burn-up dependent irradiation behavior and measured target and pellet properties, hereafter referred to as the production model. These models are used to conservatively determine several important steady-state parameters including target stresses and temperatures, the limiting condition of which is the maximum temperature with respect to the melting point. The single pellet model results provide a basis for the safety of the irradiations, followed by parametric analyses in the initial prototypical designs that were necessary due to the limiting fabrication and irradiation data available. The calculated parameters in the final production target model are the most accurate and comprehensive, while still conservative. Over 210 permutations in irradiation time and position were evaluated, and are supported by the most recent inputs and highest fidelity methodology. The results of these analyses show that the models presented in this report provide a robust and reliable basis for previous, current and future experiment safety analyses. In addition, they reveal an evolving knowledge of the steady-state behavior of the NpO 2/Al pellets under irradiation for a variety of target encapsulations and potential conditions.« less

Authors:
 [1];  [1];  [1];  [1];  [1]
  1. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). High Flux Isotope Reactor (HFIR)
Sponsoring Org.:
USDOE
OSTI Identifier:
1342667
Report Number(s):
ORNL/TM-2016/234
TRN: US1701887
DOE Contract Number:  
AC05-00OR22725
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
22 GENERAL STUDIES OF NUCLEAR REACTORS; PLUTONIUM 238; NEPTUNIUM 237; SAFETY ANALYSIS; HFIR REACTOR; PLUTONIUM; NEPTUNIUM OXIDES; IRRADIATION; PELLETS; SIMULATION; STEADY-STATE CONDITIONS; KNOWLEDGE BASE; PARAMETRIC ANALYSIS; Pu-238; HFIR; COMSOL

Citation Formats

Hurt, Christopher J., Freels, James D., Hobbs, Randy W., Jain, Prashant K., and Maldonado, G. Ivan. Thermal Safety Analyses for the Production of Plutonium-238 at the High Flux Isotope Reactor. United States: N. p., 2016. Web. doi:10.2172/1342667.
Hurt, Christopher J., Freels, James D., Hobbs, Randy W., Jain, Prashant K., & Maldonado, G. Ivan. Thermal Safety Analyses for the Production of Plutonium-238 at the High Flux Isotope Reactor. United States. doi:10.2172/1342667.
Hurt, Christopher J., Freels, James D., Hobbs, Randy W., Jain, Prashant K., and Maldonado, G. Ivan. Mon . "Thermal Safety Analyses for the Production of Plutonium-238 at the High Flux Isotope Reactor". United States. doi:10.2172/1342667. https://www.osti.gov/servlets/purl/1342667.
@article{osti_1342667,
title = {Thermal Safety Analyses for the Production of Plutonium-238 at the High Flux Isotope Reactor},
author = {Hurt, Christopher J. and Freels, James D. and Hobbs, Randy W. and Jain, Prashant K. and Maldonado, G. Ivan},
abstractNote = {There has been a considerable effort over the previous few years to demonstrate and optimize the production of plutonium-238 (238Pu) at the High Flux Isotope Reactor (HFIR). This effort has involved resources from multiple divisions and facilities at the Oak Ridge National Laboratory (ORNL) to demonstrate the fabrication, irradiation, and chemical processing of targets containing neptunium-237 (237Np) dioxide (NpO2)/aluminum (Al) cermet pellets. A critical preliminary step to irradiation at the HFIR is to demonstrate the safety of the target under irradiation via documented experiment safety analyses. The steady-state thermal safety analyses of the target are simulated in a finite element model with the COMSOL Multiphysics code that determines, among other crucial parameters, the limiting maximum temperature in the target. Safety analysis efforts for this model discussed in the present report include: (1) initial modeling of single and reduced-length pellet capsules in order to generate an experimental knowledge base that incorporate initial non-linear contact heat transfer and fission gas equations, (2) modeling efforts for prototypical designs of partially loaded and fully loaded targets using limited available knowledge of fabrication and irradiation characteristics, and (3) the most recent and comprehensive modeling effort of a fully coupled thermo-mechanical approach over the entire fully loaded target domain incorporating burn-up dependent irradiation behavior and measured target and pellet properties, hereafter referred to as the production model. These models are used to conservatively determine several important steady-state parameters including target stresses and temperatures, the limiting condition of which is the maximum temperature with respect to the melting point. The single pellet model results provide a basis for the safety of the irradiations, followed by parametric analyses in the initial prototypical designs that were necessary due to the limiting fabrication and irradiation data available. The calculated parameters in the final production target model are the most accurate and comprehensive, while still conservative. Over 210 permutations in irradiation time and position were evaluated, and are supported by the most recent inputs and highest fidelity methodology. The results of these analyses show that the models presented in this report provide a robust and reliable basis for previous, current and future experiment safety analyses. In addition, they reveal an evolving knowledge of the steady-state behavior of the NpO2/Al pellets under irradiation for a variety of target encapsulations and potential conditions.},
doi = {10.2172/1342667},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Mon Aug 01 00:00:00 EDT 2016},
month = {Mon Aug 01 00:00:00 EDT 2016}
}

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