Assessment of the potential for criticality in the far field of a used nuclear fuel repository

Atz, Milos; Salazar, Alex; Hirano, Fumio; Fratoni, Massimiliano; Ahn, Joonhang

doi:10.1016/j.anucene.2018.09.028

Title: Assessment of the potential for criticality in the far field of a used nuclear fuel repository

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Abstract

This study aims to assess the likelihood for criticality in the far field of a repository for direct disposal of commercial light water reactor used nuclear fuel. Two models are used in combination: (1) a neutronics model to estimate the minimum critical masses of spherical, water-saturated depositions of fissile material; (2) a transport model to simulate the dissolution of waste packages arranged in an array and the subsequent transport of fissile solutes through fractured bedrock to a single accumulation location. The neutronics model shows that heavy metals from different types of used fuel present the same minimum critical mass behavior in the parameter space of initial enrichment and burnup, dictated largely by the fissile content. However, the magnitude of the minimum critical mass varies significantly within that parameter space, and secondary effects like the presence of absorbing nuclides play a minor role. Here, the transport model employs various subsurface transport scenarios, and for each scenario the mass of each isotope and the overall fissile content of the accumulation is reported from the time of canister failure up to one hundred million years at various distances from the repository edge. Taking the results of the two models in concert, it ismore »« less

Authors:

Atz, Milos ^[1]; Salazar, Alex ^[1]; Hirano, Fumio ^[2]; Fratoni, Massimiliano ^[1]; Ahn, Joonhang ^[1]

Univ. of California, Berkeley, CA (United States)
Japan Atomic Energy Agency, Ibaraki (Japan)

Publication Date:: Mon Oct 01 00:00:00 EDT 2018

Research Org.:: Univ. of California, Berkeley, CA (United States). Nuclear Science and Security Consortium

Sponsoring Org.:: USDOE National Nuclear Security Administration (NNSA), Office of Defense Nuclear Nonproliferation

OSTI Identifier:: 1545538

Grant/Contract Number:: NA0003180

Resource Type:: Accepted Manuscript

Journal Name:: Annals of Nuclear Energy (Oxford)

Additional Journal Information:: Journal Name: Annals of Nuclear Energy (Oxford); Journal Volume: 124; Journal Issue: C; Journal ID: ISSN 0306-4549

Publisher:: Elsevier

Country of Publication:: United States

Language:: English

Subject:: 11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS; Nuclear waste disposal; Criticality safety assessment; Geologic repository; Radionuclide transport

Citation Formats


                    Atz, Milos, Salazar, Alex, Hirano, Fumio, Fratoni, Massimiliano, and Ahn, Joonhang. Assessment of the potential for criticality in the far field of a used nuclear fuel repository.  United States: N. p., 2018. 
Web.  doi:10.1016/j.anucene.2018.09.028.

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                    Atz, Milos, Salazar, Alex, Hirano, Fumio, Fratoni, Massimiliano, & Ahn, Joonhang. Assessment of the potential for criticality in the far field of a used nuclear fuel repository.  United States.  https://doi.org/10.1016/j.anucene.2018.09.028

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                    Atz, Milos, Salazar, Alex, Hirano, Fumio, Fratoni, Massimiliano, and Ahn, Joonhang. Mon .  
"Assessment of the potential for criticality in the far field of a used nuclear fuel repository".  United States.  https://doi.org/10.1016/j.anucene.2018.09.028.  https://www.osti.gov/servlets/purl/1545538.

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@article{osti_1545538,

  title        = {Assessment of the potential for criticality in the far field of a used nuclear fuel repository},

  author       = {Atz, Milos and Salazar, Alex and Hirano, Fumio and Fratoni, Massimiliano and Ahn, Joonhang},

  abstractNote = {This study aims to assess the likelihood for criticality in the far field of a repository for direct disposal of commercial light water reactor used nuclear fuel. Two models are used in combination: (1) a neutronics model to estimate the minimum critical masses of spherical, water-saturated depositions of fissile material; (2) a transport model to simulate the dissolution of waste packages arranged in an array and the subsequent transport of fissile solutes through fractured bedrock to a single accumulation location. The neutronics model shows that heavy metals from different types of used fuel present the same minimum critical mass behavior in the parameter space of initial enrichment and burnup, dictated largely by the fissile content. However, the magnitude of the minimum critical mass varies significantly within that parameter space, and secondary effects like the presence of absorbing nuclides play a minor role. Here, the transport model employs various subsurface transport scenarios, and for each scenario the mass of each isotope and the overall fissile content of the accumulation is reported from the time of canister failure up to one hundred million years at various distances from the repository edge. Taking the results of the two models in concert, it is shown that even if the accumulation of a critical mass is possible under conservative conditions, these conditions are unlikely to be present in the vicinity of a carefully engineered repository. Based on the results of each model, recommendations for risk mitigation in terms of waste characteristics and repository design are given.},

  doi          = {10.1016/j.anucene.2018.09.028},

  journal      = {Annals of Nuclear Energy (Oxford)},

  number       = C,

  volume       = 124,

  place        = {United States},

  year         = {Mon Oct 01 00:00:00 EDT 2018},

  month        = {Mon Oct 01 00:00:00 EDT 2018}

}

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