art.inl.gov

• Advanced Reactor Technologies• Idaho National Laboratory

Gas-Cooled ReactorFuels and Methods Program Review

June 18-19, 2019

Status of the IAEA CRP on HTGR UAM and OECD/NEA MHTGR-350

Benchmarks

Gerhard Strydom ART-GCR: National Technical Director

Program Goals and Objectives

• Pre-2012: development of tools; support NGNP for DOE and NRC (PEBBED, PEBBLES, CYNOD, THETRIS, COMBINE7, HEXPEDITE)

• 2012-2018: mature tools with minor developmental work (PEBBED, PHISICS/RELAP5-3D, XS generation with DRAGON, HELIOS, SERPENT and SCALE), support private HTGR efforts (X-Energy, Kairos Power, Framatome)

• 2019+: all code development now under NEAMS; ART limited to V&V with NEAMS-tools and maintaining a low/high option to vendors and DOE.

• Methods activity is split between Experimental Validation (Jim Wolf – HTTF, NEUPs) and Simulation

• The two tasks active under the FY-19 GCR Methods Simulation activity are both code-to-code verification benchmarks:§ OECD/NEA MHTGR-350: best-estimate core neutronics & thermal fluids; lattice

physics§ IAEA CRP on HTGR Uncertainties in Modeling (UAM): uncertainty and sensitivity

assessment of cross section & material input uncertainties on lattice; core stand-alone and coupled steady state and transients.

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IAEA CRP on HTGR Reactor Physics, Thermal-Hydraulics and Depletion Uncertainty Analysis

• The IAEA use Coordinated Research Projects to establish international co-operative research programs (more than 1,600 institutions were involved in ~100 CRPs in 2018).

• Typically 3-6 years project duration. The current IAEA Coordinated Research Project (CRP) on HTGR UAM was started in 2012 and ends June 2019.

• The objective of the CRP is § To contribute new knowledge towards improving the fidelity of calculation

models § in the design and safety analysis of high temperature gas-cooled reactors§ by fully accounting for all sources of uncertainties in calculations.

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Participation• China – INET

• China – Harbin Engineering University

• Germany – GRS

• Korea – KAERI

• Poland – AGH University of Science and Technology

• Russian Federation – Kurchatov Institute

• South Africa – North West University

• USA – North Carolina State University

• USA – Idaho National Laboratory

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IAEA CRP on HTGR UAM – Phases and ExercisesExercise I-1 and I-2: Cell neutronics

Exercise I-3 and I-4: Cell thermal fluids

Phase I (Local)

Exercise II-1: Core depletion

Exercise II-2: Stand-alone core neutronics

Phase II(Global)

Exercise III-1: Coupled core neutronics + thermal fluids steady-state

Phase III(Design)

Exercise III-3: Stand-alone core kinetics

Exercise IV-1: Coupled core transient (CRW)Phase IV(Safety)

Exercise III-4: Stand-alone core thermal fluids

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Reference Designs

250 MW Pebble Bed Prismatic MHTGR-3506

HTR-10 Fuel Pebble Model Options (Harbin Univ. & INET)

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HTR-10: Single Fuel Pebble

Module type kinf ± σRelative

uncertainty (%Δk/k)

Relative difference (%)

TRISO stochastic model 1.70534 ± 0.00013 0.4757 ± 0.00021 --Lattice random model 1.70609 ± 0.00014 0.4798 ± 0.00022 0.86Lattice jiggled model 1.70539 ± 0.00013 0.4776 ± 0.00021 0.40Zone jiggled model 1.70450 ± 0.00015 0.4768 ± 0.00021 0.23

TRISOS stochastic model with TC algorithm

1.70585 ± 0.00017 0.4751 ± 0.00021 -0.13

Regular lattice model 1.70468 ± 0.00015 0.4774 ± 0.00021 0.36RPT model 1.70481 ± 0.00013 0.4764 ± 0.00020 0.15

Homogenized model 1.59431 ±0.00016 0.4909 ± 0.00025 3.2Total homogenized model 1.57253 ± 0.00017 0.4940 ± 0.00025 3.8

• Uncertainty propagated from nuclear cross-sections

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INET (China) recent activities related to IAEA CRP on HTGR UAM• Work related to PBR-250 benchmark exercises§ NCSU: UQ&SA results for PBR-250 Ex. I-1 (pebble model), I-2 (assembly

model) and PBR-250 (full-core explicit model) at cold zero power state with SCALE/TSUNAMI-3D

§ INL MOOSE: Exercise I-3 (single pebble T/H benchmark)

• Code development for HTGR uncertainty analysis based on VSOP99 code§ Stochastic sampling method based

§ Nuclear cross section uncertainty analysis

§ Fission yield uncertainty analysis

§ UQ&SA for HTGR depletion calculation

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PBR-250 Fully Explicit core model

n CE TSUNAMI-3D (CLUTCH)• HTR-PM at cold initial critical state

n Criticality calculation verified• 3D CE KENO-VI vs. Serpent-2

n Uncertainty: 0.68221±0.00081%

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Phase II Lattice Building Blocks: Single Block and Super Cell

Cross sections are generated for the central fuel block in a 7-block “super” cell. This method accounts for the spectral environment changes caused by the surrounding depleted fuel and graphite blocks.

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Phase II Ex. II-2 Definitions

Ex. II-2a: model option 1Fuel region loaded with single fresh block XS library.

Ex. II-2a: model option 2Fuel center ring loaded with fresh fuel XS library. Core periphery constructed using XS derived from cell L.

Ex. II-2b: model option 1Fuel region loaded with single fresh and depleted blocks

Ex. II-2b: model option 2Fuel region loaded with fresh and depleted blocks, and cell L on periphery.

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Ex. II-2a: K-eff Mean and Uncertainty (INL)

• The core keff mean values vary significantly (more than 4%) between the depleted (2b-r) and fresh cores (2a-r).

• In contrast to these large keff differences, the standard deviations only vary between 0.44%-0.51%.

• This is a relatively tight uncertainty band for cores containing different fuel loading patterns, rodded and unrodded reflector blocks, and a peripheral super cell cross-section libraries.

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Ex.II-2b – Core Stand-alone (KAERI)

Problem 3D CoreSuper Cell

for Fresh FuelSuper Cell

for Burnt Fuel

Code DeCART/MUSAD/CAPP DeCART/MUSAD

Parameter keff Axial Offset (%) CRW(pcm) kinf kinf

Value 1.04104 -0.108 81 1.05621 1.04503

Uncert.(%) 0.69 1.53 1.19 0.78 0.58

• No. XS sets: 600

• Multi-Group XS: 190 group based on ENDF/B-VII.1

• Covar. data: 190 group from ENDF/B-VII.1

• Few-Group XS: 10 group

Rel.Power 1.001Std.Dev(%)

0.8190.384

1.3530.327

0.974

0.3300.764

0.271

1.2900.339

0.930

0.3090.833

0.292

1.1010.327

1.105

1.2920.272

0.8570.343

1.3550.311

0.8360.320

1.0110.332

0.7680.313

1.057

0.2760.823

0.3390.997

0.395

0.8250.342

0.9310.266

0.3161.080

0.292

0.342

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Experimental Data• HTGR operational and experimental data base is very limited.

• Older facilities typically did not include well-characterized uncertainty data.

IEU-COMP-THERM-008(ASTRA)

VHTRC-GCR-EXP-001/CRIT-COEF

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VHTRC – Impact of Manufacturing Uncertainties (NCSU)

VHTRC manufacturing uncertainties: experiment vs RAVEN/PHISICS (both ~300-380 pcm)

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CRP on HTGR UAM – Summary• The CRP has been extended from May 2018 to June 2019 to allow

uncertainty propagation to the coupled transient phase.

• IAEA TECDOC will be drafted in 2020; possibly issued in 2021-2050.

• The CRP has already produced more than 16 conference and journal publications since 2016.

• 2 MSc and 3 PhDs completed or nearing completion

• Several codes further developed to be able to do this work (e.g.):§ PHISICS + RELAP5-3D + RAVEN @ INL § MUSAD + DeCart/McCard (KAERI)§ TSUNAMI-MG-DH (GRS)§ VSOP99 Uncertainty module (INET)§ Double Heterogeneity treatment in SCALE improved (ORNL)

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OECD/NEA MHTGR-350 Benchmark• FY-19 status and FY-20 outlook§ Phase I Ex. 1 (core neutronics) and Phase III (lattice) reports finalized by

participants (see 2018 presentation by J. Ortensi). Currently being prepared for publication by OECD/NEA.§ Phase I Ex. 2 (core thermal fluids):

• First draft comparison report in Dec. 2017 showed significant differences in certain reflector regions for case without bypass flows. INL RELAP5-3D results updated in Dec. 2018 based on model refinements.

• U-Michigan (AGREE) and KAERI (GAMMA+) launched independent verification of their models until convergence with CFD code CFX was reached on a series of simpler exercises (Annals of Nuclear Energy publication to follow).

• Updated results will be compared by Dec. 2019.§ Phase I Ex. 3 (coupled neutronics/thermal fluids):

• Temperature differences carried over into coupled models.• INL (PHISICS/R5) results updated in 2018.• Unknown if UNIST (MCS/GAMMA+) plans to update their results.• Updated U-Michigan (PARCS/AGREE) results expected by end 2019.

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FY-2019 Level 2 and 3 Milestone Status• L3 on IAEA CRP results for Phases II-IV (due Sept. 15th, 2019)

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Path Forward • Since 2012, the HTGR Methods & Simulation activity has been under

increasing funding pressure.

• In FY-19, DOE formalized the mandate of HTGR Methods: § Focus only on V&V of existing and new codes that are/will be used to support

vendor & NRC HTGR development and licensing§ No new code development in ART – all code development must be under

NEAMS§ Only minimal code maintenance + documentation of existing tools

(PHISICS/R5, PEBBED); justified by ad hoc interest (e.g. TCF with Framatome). § The final reports for the two international benchmarks will be completed in FY-

20 (only $50k in new funding requested). § DOE deliverable: L3 report on IAEA CRP results for Phases II-IV (due Sept.

15th, 2019)

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Path Forward • For FY-20, the focus shifts to V&V of HTGRs using the latest

NEAMS/NRC supported tools (MAMMOTH, PRONGHORN, etc.).§ Pebble shuffling/depletion capability for pebble bed HTGRs (on MOOSE)§ Fast nodal solver for prismatic HTGRs (on MOOSE)

• These activities will be supported through NEAMS funding under Reactor Product Line (RPL). This effort remains small (<$500k in FY-20).

• Development of any new tools is funded through separate NEAMS+NRC funding lines outside ART. The focus is different for developers and users, so we see this division of roles as a positive development going forward.

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References

• IAEA CRP on HTGR UAM:§ INL reports § PBR-250 data from Fu Li (INET)§ MHTGR-350 data from Tae-Young Lee (KAERI), Pascal Rouxelin (NCSU)

• OECD/NEA MHTGR-350: § INL reports § Status updates from Volkan Seker (U-Mich), Javier Ortensi (INL)

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ART-GCR NTDgerhard.strydom@.inl.gov(208) 526-1216ART.INL.GOV

Gerhard Strydom

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