VERA Development and Release Plans

FY19-FY20CASL Industry Council Meeting

Raleigh, NC

April 23, 2019

Scott PalmtagCASL Chief Technologist

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Topics

• Current CASL Development Priorities• Upcoming VERA releases• NQA and Documentation• Post-CASL VERA

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Development Priorities

• In FY19, the CASL development strategy is to “finish strong”

• Intense focus on key challenge problems prioritized by the Industry Council– CIPS/CILC– Vessel fluence

• Complete other challenge problems and demonstrate VERA capabilities– RIA, DNB, etc.

CRUD and ex-core transport are key capabilities for long-term success of VERA

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Validation and NQA Qualification

• In FY19 CASL will complete an extensive set of validation cases including hundreds of commercial reactor fuel cycles

• VERA software and documentation will be upgraded to NQA-1 readiness for preparation for post-CASL deployment

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VERA NQA-1 Documentation

• VERA QA Program Plan (QAPP)• VERA Quality Assurance Plan• Implementing Procedures (currently up to 8 procedures)• Code documentation for each “team” –

MPACT, CTF, Bison, and VERA-IO1. Software Management Plan (SMP)2. Users Manual (UM)3. Theory Manual (TM) 4. Programmers Manual (PM)5. Software Requirements Description (SRD)6. Software Test Plan (SMP)7. Software Test Report (STR)8. Validation and Verification (VV)

NQA-1 Certification Audit tentatively scheduled for

August 2019

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Establish User Base and Support Network

• CASL is actively working with nuclear industry to develop value demonstrations and support non-CASL applications

• 1st VERA Users Group meeting held in February, 2019 provided information, training, and two-way dialogue between industry users and VERA developers

Several non-CASL industry organizations have begun to use VERA on their own

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Upcoming VERA Releases

• CASL continues on a six month release cycle– VERA 4.0 release candidate used for VUG training in Feb 2019– VERA 4.0.1 release planned in May 2019 for minor updates

• Will contain all major MPACT, CTF, and MAMBA features• Will be workhorse for AMA validation in FY19

– VERA 4.1 planned for end of CASL: October, 2019• Updates and features for Shift• Improvements to CTFFuel• Updated MAMBA defaults

VERA will continue to be patched and released as necessary as part of new

ModSimX program

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VERA 4.1 – Post-CASL Capabilities

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VERA 4.1 – MPACT• Advanced 3D Neutronics

– Method-of-Characteristics– 51 energy groups– Intra-pin power and depletion

• On par with best industry lattice physics methods

• 3D accuracy close to continuous-energy Monte Carlo methods

• Ability to solve 2D lattices, 2D cores, and 3D cores with same methods

• Steady-state and Transient capable• Pin-wise power and depletions• Integrated explicit isotopic depletion and

decay with ORIGEN• Core shuffling and control rod movement• In-core detector responses• Validated against critical experiments

and hundreds of fuel cycles• Requires 500-1000 cores per quarter-

core simulation

MPACT provides state-of-the-art whole core neutronics and

core simulation functions

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VERA 4.1 – CTF• Whole-Core Two-Phase Subchannel

Thermal-Hydraulics– Two-fluid, three-field representation of the

two-phase flow– Continuous vapor (mass, momentum and energy)– Continuous liquid (mass, momentum and energy)– Entrained liquid drops (mass and momentum)– Non-condensable gas mixture (mass)

• Cross flow between channels• Solution extends outside of active fuel• Spacer grid pressure loses and

blockages• Intra-grid form losses• CFD-informed TKE and HTC• User input inlet flow distributions• Transient analyses (SLB, RIA)• Built-in material properties• Parallel Solution = ~5 secs per solve• Requires 50-200 cores per quarter-core

simulation

CTF provides the best available sub-channel

methods to the scale of an entire reactor core

Sub-Channel Discretization for

the entire core

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VERA 4.1 – CTFFuel• New internal fuel rod model within CTF

– Burnup-dependent thermal conductivity, clad creep, relocation, and pellet swelling

• Provides fast intra-pin burnup and temperature coupling

• Functional for steady-state and transient conditions• Provides consistent temperature feedback for multiple

fuel types• Benchmarked against Bison• Implemented as an extendable interface

CTFFuel provides a fast, robust fuel temperature capability to VERA for

whole core depletion and transients

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VERA 4.1 – Bison Interoperability

• VERA can be used to perform detailed fuel rod performance analysis with Bison– Finite element-based engineering scale fuel performance

code– Solves the fully-coupled thermomechanics and species

diffusion equations in 1D symmetric, 1.5D, 2D axisymmetric or generalized plane strain, or 3D

• Fuel rod geometry and power histories used to automatically create Bison inputs for any or all fuel rods in a reactor core

• Bison results are collected into VERAOutformat for whole-core fuel rod performance analysis or screening

• Also used for creating fuel temperature tables and comparison with CTFFuel

Bison provides advanced fuel mechanical evaluation capability for PCI screening analyses

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VERA 4.1 – MAMBA• 3D rod-wise CRUD growth• Surface chemistry modeling of CRUD• Microstructural chemistry and heat transfer• Boron uptake and dissolution in the CRUD

layer for neutronics feedback• High-resolution prediction of threshold

physics• Source-term mass balance• Metal ion pickup throughout primary loop• Calibration based on local plant flux map

measurements• CRUD shuffling• Ultrasonic cleaning by assembly• Neutronic feedback enables simulation of

power shifts and shutdown margin loss

MAMBA provides game-changing capabilities to analyze CIPS/CILC risk and will reduce the fuel

costs of the U.S. commercial fleet

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VERA 4.1 – Shift• Accurate and efficient ex-core neutron

transport– Continuous-energy Monte Carlo neutron transport to

any region outside of the reactor core– State-of-the-art hybrid methods focus particles towards

regions of interest

• General geometry capability for ex-vessel region

• MPACT provides accurate 3D fission source term on a case-by-case basis

• Enables best-estimate vessel fluence analysis and coupon irradiation

• Ex-core detector response calculations and weighting factor generation

• Concrete degradation and core structure embrittlement analyses

• Typically requires 100-400 cores

Shift transforms the analysis realm of ex-core radiation transport by integration with the VERA core simulator for best-estimate

results that will extend the life of existing plants

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VERA 4.1 – VERA Input and Output • Easy-to-use ascii interface provides a single

input file for all physics codes– Open source format– Easy to archive and QA

• Output format is standardized HDF5 format and is consistent (or merged) across all codes

• VERAView visualization tool provides simultaneous multi-physics analyses of the VERA results– Multiple predetermined views– Easy access to data via copy/paste or export to Excel– Multi-platform (Windows, iOS, Linux)– Open source

• VERARun provides an easy-to-use, customizable set of commands for running VERA on any HPC platforms

• VERA is easier to learn and use than most industry methods

• Provides a user seamless access all the physics of VERA without being an expert in any one physics code

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Post-CASL VERA (4.1)

CTFthermal-hydraulics

ORIGENisotopic depletion and decay

CTFFuelfuel rod performance

MPACTneutronics

MAMBACRUD chemistry

Shiftex-core neutron transport

VERA is the most advanced 3D PWR reactor simulator in the world

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VERA-CS vs. Industry Core SimulatorsPhysics Model Industry Practice CASL (VERA-CS)Neutron Transport 3-D diffusion (core)

2 energy groups (core)2-D transport on single assy

3-D transport51 energy groups

Power Distribution nodal average with pin-power reconstruction methods

explicit pin-by-pin

Thermal-Hydraulics 1-D assembly-averaged pin-by-pin subchannel (w/crossflow)

Fuel Temperatures nodal average pin-by-pin 2-D or 3-D

Fuel Performance Empirically-based models for key performance phenomena

Science-based models for key performance phenomena

Xenon/Samarium nodal average w/correction pin-by-pin

Depletion infinite-medium cross sectionsquadratic burnup correctionhistory correctionsspectral correctionsreconstructed pin exposures

pin-by-pin with actual core conditions

Reflector Models 1-D cross section models actual 3-D geometry

Target Platforms workstation (single-core) 1,000 – 100,000 cores

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What is “Success” of CASL?

• Accurate simulations of PWRs (with confidence)• Improved understanding of safety margins• VERA deployed to and applied broadly by the nuclear

industry• Improved economics and cost effectiveness• Established and maintained research and industry

partnerships• Continued education and training• Continued use and growth of VERA in ModSimX

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