Evaluation of PBR Spent Fuel Criticality and Dose Rate Compliance for Storage and Transportation.
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| Title: | Evaluation of PBR Spent Fuel Criticality and Dose Rate Compliance for Storage and Transportation. |
|---|---|
| Authors: | Wing, Jonathan1 (AUTHOR) jwing1@vols.utk.edu, Petersen, Gordon M.2 (AUTHOR), Joseph, Robert A.2 (AUTHOR), Maldonado, Guillermo Ivan1 (AUTHOR) |
| Source: | Nuclear Science & Engineering. Aug2026, Vol. 200 Issue 8, p1934-1950. 17p. |
| Subjects: | Pebble bed reactors, Spent reactor fuels, Storage, Nuclear energy safety measures, Exposure dose, Transportation industry, Nuclear reactor reactivity |
| Abstract: | Spent tri-structural isotropic (TRISO)–based fuels have a strong track record in storage and transportation without documented incidents. This work seeks to reduce uncertainty to aid in more informed spent fuel management of TRISO-based fuels by modeling both fresh and spent pebble bed reactor (PBR) fuel and comparing the results to the regulatory standards from 10 CFR 71. SCALE was used for all modeling due to it having fast and accurate methods for handling PBR fuel modeling, as well as having an efficient method for shielding calculations in monaco with automated variance reduction using importance calculations (MAVRIC), which utilizes the consistent adjoint-driven importance sampling (CADIS) and the forward-weighted consistent adjoint-driven importance sampling (FW-CADIS) methods. KENO-VI was used for all criticality calculations, TSUNAMI was used for uncertainty quantification on k-effective, TRITON and the Oak Ridge isotope generation code (ORIGEN) were both used for depletion of the fuel, and MAVRIC was used for shielding calculations. For criticality assessments, this study focused on the requirement that the value of the neutron multiplication factor, k-effective (k-eff), would not exceed a peak value of 0.95, including uncertainty, with 95% confidence. Criticality was initially examined by modeling fresh fuel from three different designs—HTR-10 fuel, PBMR-400 fuel, and demonstration fuel representative of a TRISO-fueled modern high-temperature gas reactor (HTGR) design, henceforth referred to as Demo HTGR—and placing them into various sized containers with conditions described in 10 CFR 71 to quantify the peak k-eff state. When the peak value of 0.95 k-eff was exceeded, mitigation methods were examined in those scenarios. Burnup credit, pebble displacement in areas of strong neutron multiplication, and random pebble replacement using pebbles of various compositions and replacement fractions were examined. In summary, the criticality of PBR fuels can be well accounted for by restricting container size, taking credit for burnup, or by displacing/replacing pebbles. Uncertainty of the k-eff due to nuclear data uncertainties was recorded at ~0.6644%Δk/k, or roughly 664% mil (pcm). The nuclear data–induced uncertainty was relatively small and should not require significant modification in the design to be accounted for. Revisions to the evaluated nuclear data file values have been shown to have a larger impact than nuclear data–induced uncertainty. For dose rate aspects, U.S. Nuclear Regulatory Commission regulations require a maximum dose rate of 10 millirem per hour (mrem/h) at 2 meters. In examining the dose rate behavior of spent PBR fuel, the representative Demo HTGR fuel was modeled exclusively due to it possessing the highest target burnup of the examined fuels. Equilibrium cycle modeling methods were used to produce a higher-fidelity discharge isotopic composition than simple assumptions, such as reflected pebbles. The discharge composition was used as a source term in the fixed-source transport shielding calculations, and dose rates were calculated at 2 m for the shortest possible cooling time. The low concentration of fuel material led to dose rates that were in line with regulatory limits, despite the high burnup when compared to traditional light water reactor fuels. The methods employed in this study would require more work to further verify and validate and are limited to the criticality and dose rate analyses performed. [ABSTRACT FROM AUTHOR] |
| Copyright of Nuclear Science & Engineering is the property of Taylor & Francis Ltd and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.) | |
| Database: | Engineering Source |
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| Header | DbId: egs DbLabel: Engineering Source An: 194842684 AccessLevel: 6 PubType: Academic Journal PubTypeId: academicJournal PreciseRelevancyScore: 0 |
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| Items | – Name: Title Label: Title Group: Ti Data: Evaluation of PBR Spent Fuel Criticality and Dose Rate Compliance for Storage and Transportation. – Name: Author Label: Authors Group: Au Data: <searchLink fieldCode="AR" term="%22Wing%2C+Jonathan%22">Wing, Jonathan</searchLink><relatesTo>1</relatesTo> (AUTHOR)<i> jwing1@vols.utk.edu</i><br /><searchLink fieldCode="AR" term="%22Petersen%2C+Gordon+M%2E%22">Petersen, Gordon M.</searchLink><relatesTo>2</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Joseph%2C+Robert+A%2E%22">Joseph, Robert A.</searchLink><relatesTo>2</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Maldonado%2C+Guillermo+Ivan%22">Maldonado, Guillermo Ivan</searchLink><relatesTo>1</relatesTo> (AUTHOR) – Name: TitleSource Label: Source Group: Src Data: <searchLink fieldCode="JN" term="%22Nuclear+Science+%26+Engineering%22">Nuclear Science & Engineering</searchLink>. Aug2026, Vol. 200 Issue 8, p1934-1950. 17p. – Name: Subject Label: Subjects Group: Su Data: <searchLink fieldCode="DE" term="%22Pebble+bed+reactors%22">Pebble bed reactors</searchLink><br /><searchLink fieldCode="DE" term="%22Spent+reactor+fuels%22">Spent reactor fuels</searchLink><br /><searchLink fieldCode="DE" term="%22Storage%22">Storage</searchLink><br /><searchLink fieldCode="DE" term="%22Nuclear+energy+safety+measures%22">Nuclear energy safety measures</searchLink><br /><searchLink fieldCode="DE" term="%22Exposure+dose%22">Exposure dose</searchLink><br /><searchLink fieldCode="DE" term="%22Transportation+industry%22">Transportation industry</searchLink><br /><searchLink fieldCode="DE" term="%22Nuclear+reactor+reactivity%22">Nuclear reactor reactivity</searchLink> – Name: Abstract Label: Abstract Group: Ab Data: Spent tri-structural isotropic (TRISO)–based fuels have a strong track record in storage and transportation without documented incidents. This work seeks to reduce uncertainty to aid in more informed spent fuel management of TRISO-based fuels by modeling both fresh and spent pebble bed reactor (PBR) fuel and comparing the results to the regulatory standards from 10 CFR 71. SCALE was used for all modeling due to it having fast and accurate methods for handling PBR fuel modeling, as well as having an efficient method for shielding calculations in monaco with automated variance reduction using importance calculations (MAVRIC), which utilizes the consistent adjoint-driven importance sampling (CADIS) and the forward-weighted consistent adjoint-driven importance sampling (FW-CADIS) methods. KENO-VI was used for all criticality calculations, TSUNAMI was used for uncertainty quantification on k-effective, TRITON and the Oak Ridge isotope generation code (ORIGEN) were both used for depletion of the fuel, and MAVRIC was used for shielding calculations. For criticality assessments, this study focused on the requirement that the value of the neutron multiplication factor, k-effective (k-eff), would not exceed a peak value of 0.95, including uncertainty, with 95% confidence. Criticality was initially examined by modeling fresh fuel from three different designs—HTR-10 fuel, PBMR-400 fuel, and demonstration fuel representative of a TRISO-fueled modern high-temperature gas reactor (HTGR) design, henceforth referred to as Demo HTGR—and placing them into various sized containers with conditions described in 10 CFR 71 to quantify the peak k-eff state. When the peak value of 0.95 k-eff was exceeded, mitigation methods were examined in those scenarios. Burnup credit, pebble displacement in areas of strong neutron multiplication, and random pebble replacement using pebbles of various compositions and replacement fractions were examined. In summary, the criticality of PBR fuels can be well accounted for by restricting container size, taking credit for burnup, or by displacing/replacing pebbles. Uncertainty of the k-eff due to nuclear data uncertainties was recorded at ~0.6644%Δk/k, or roughly 664% mil (pcm). The nuclear data–induced uncertainty was relatively small and should not require significant modification in the design to be accounted for. Revisions to the evaluated nuclear data file values have been shown to have a larger impact than nuclear data–induced uncertainty. For dose rate aspects, U.S. Nuclear Regulatory Commission regulations require a maximum dose rate of 10 millirem per hour (mrem/h) at 2 meters. In examining the dose rate behavior of spent PBR fuel, the representative Demo HTGR fuel was modeled exclusively due to it possessing the highest target burnup of the examined fuels. Equilibrium cycle modeling methods were used to produce a higher-fidelity discharge isotopic composition than simple assumptions, such as reflected pebbles. The discharge composition was used as a source term in the fixed-source transport shielding calculations, and dose rates were calculated at 2 m for the shortest possible cooling time. The low concentration of fuel material led to dose rates that were in line with regulatory limits, despite the high burnup when compared to traditional light water reactor fuels. The methods employed in this study would require more work to further verify and validate and are limited to the criticality and dose rate analyses performed. [ABSTRACT FROM AUTHOR] – Name: AbstractSuppliedCopyright Label: Group: Ab Data: <i>Copyright of Nuclear Science & Engineering is the property of Taylor & Francis Ltd and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract.</i> (Copyright applies to all Abstracts.) |
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| RecordInfo | BibRecord: BibEntity: Identifiers: – Type: doi Value: 10.1080/00295639.2025.2547490 Languages: – Code: eng Text: English PhysicalDescription: Pagination: PageCount: 17 StartPage: 1934 Subjects: – SubjectFull: Pebble bed reactors Type: general – SubjectFull: Spent reactor fuels Type: general – SubjectFull: Storage Type: general – SubjectFull: Nuclear energy safety measures Type: general – SubjectFull: Exposure dose Type: general – SubjectFull: Transportation industry Type: general – SubjectFull: Nuclear reactor reactivity Type: general Titles: – TitleFull: Evaluation of PBR Spent Fuel Criticality and Dose Rate Compliance for Storage and Transportation. Type: main BibRelationships: HasContributorRelationships: – PersonEntity: Name: NameFull: Wing, Jonathan – PersonEntity: Name: NameFull: Petersen, Gordon M. – PersonEntity: Name: NameFull: Joseph, Robert A. – PersonEntity: Name: NameFull: Maldonado, Guillermo Ivan IsPartOfRelationships: – BibEntity: Dates: – D: 01 M: 08 Text: Aug2026 Type: published Y: 2026 Identifiers: – Type: issn-print Value: 00295639 Numbering: – Type: volume Value: 200 – Type: issue Value: 8 Titles: – TitleFull: Nuclear Science & Engineering Type: main |
| ResultId | 1 |
