TRACE: TRAC/RELAP Advanced Computational EngineNRC Reactor Transient and LOCA Analysis

U. S. Nuclear Regulatory Commission, Washington D.C.

W 412 Standard Plant

nSmall Breaks 2”, 3”, 4”, 6” breaksnTransition breaks SI, SI + 20%, SI – 20% , PSLnEmergency Diesel Generator (EDG) startup delay times of10 seconds and 60 seconds

Conclusions

nIncreasing EDG start up time has small impact on PCT results vResults sensitivity to loop seal clearing is a known phenomena and is independent of delay time.vDEG mitigation not considered.

nIncreasing containment spray setpoint or relying on operator action is feasible for LOCA with break sizes up to SI (cold leg) and PSL (hot leg)vContainment design specific

Vision and Long Term Direction

www.nrc.gov/reactors ...

Modeling Features

Modern ArchitecturenDecouple Computational Engine from Input Processor ‹

nParallelizable Flow Logic and Solution Scheme ‹

nObject-Based Architecture ‹

nXML-Based Automated Generation of Source Code

nEfficient List-Driven Internal Data Transfer Mechanism ‹

Component 1 Component 2 Component 3

Component 1 Component 2 Component 3

Data FlowCalculational Flow

Previous TRACE Calculationaland Data Flow

Component 1 Component 2 Component 3

Component 1 Component 2 Component 3

Data FlowCalculational Flow

Component 1 Component 2 Component 3

Flow Modi�ed forParallel Calculations

alpn

tln

tvn

Heat Structure Data

alpn

tln

tvn

Fluid Data Transfer Table

table(2)%from table(2)%totable(1)%from table(1)%to

table(3)%from table(3)%to

table(1)%to = table(1)%from

Interfacial DragCoe�cient

{component type,void fraction,phase velocities,�uid properties}

TRACE

InterfacialDrag

Module

Slug

Bubble Drag

Bubble Diameter

Pro�le FactorSlug

Fraction

IntFr(provides interface)

FricIF(sets �uid conditions)

HorizontalPipe

VerticalPipe Accumulator Pressurizer

Bubbly Bubbly/Slug Transition

Annular/Mist

(etc.)

Low-Level Object-Based Representation ofPhysical Property Evaluation Scheme

Decouple Computational Enginefrom Input Processor

Solution SchemeParallelizable Flow Logic and

Object-Based Architecture

XML-Based Automated Generation ofSource Code

E�cient List-Driven InternalData Transfer Mechanism

Modern Architecture

SNAP

TRACE InputProcessing

ComputationalEngine

Other SupportApplications

3D NeutronKinetics

SNAP SystemModel Database

RELAP5ASCIIInput

TRAC-PASCIIInput

TRAC-BASCIIInput

Interprocess MessagePassing Service

Platform IndependentBinary File

“To have the capability to perform T/H safety analysis in thefuture that allows for solutions to the full spectrum ofimportant nuclear safety problems in an efficient and effectivemanner, taking complete advantage of state-of-the-artmodeling, hardware, and software capabilities.”

We must be able to resources:

We must be able to reduce and consolidatepersonnel resources needed for solving any givenproblem and for maintaining code capability bydeveloping and/or improving:

Ease-of-useSpeedRobustnessFlexibilityMaintainability/upgradability

We must be able to accommodate the newchallenges and demands for best-estimate T/Hanalysis coupled to other related capabilities:

AccuracyFlexibilityMaintainability/upgradabilitySimplicityExpanded scope of capabilitiesQuality assurance

do more with less

LESS:

MORE:

NRC relied on 4 T/H codes

Over time the di�erences eroded but coding and inputvaried substantially

The suite was developed in the 70’s and 80’s and does nottake advantage of modern technology

Identi�ed modeling de�ciencies for the same phenomena

ameliorate the limitations

PWR

BWR

Old coding language and procedural styleLarge container arrayArchaic memory saving schemes (bit-packing)

NRC would have to expend 4 times the resources tocontinue making improvements to 4 separate tools

Evolve!Always have a running productTakes advantage of current knowledge centers

RELAP5 SBLOCA and transientsTRAC-P LBLOCA

RAMONA 3D Kinetics and stabilityTRAC-B LOCA’s and transients

Architectural and modeling improvements required to

Continue to support old technology or invest in newtechnology?

Evolve from existing code base or “develop fromscratch”?

ModernizationTRAC-P selected as basis for consolidationArchitectural modi�cations to take advantage of F90features

Input deck processingBWR-speci�c topology and modeling features

Recovered with PARCS (coupled to TRACE)

Input deck processingR5-speci�c topology and modeling features

Selection of physical models that provide the simulation�delity of TRAC-B and RELAP5 without degrading that ofTRAC-P for all targeted applications

TRAC-B functionality

RAMONA functionality

RELAP5 functionality

Developmental Assessment

Historical Perspective

Visionand LongTerm Direction

Consolidation Stages

Modeling FeaturesAdditional Component Types

Jet Pump (JETP)

Component (EXTERIOR)

Steam Separator (SEPD)Turbine (TURB)Feedwater Heater (HEATR)Containment (CONTAN)Fuel Channel (CHAN)Co-located Heat Structure (HTSTR)Radiation Enclosure (RADENC)Power (POWER)Fluid Power (FLPOWER)Single Junction (SJC)Exterior Code Coupling

Partial length fuel rodsSquare, cross, and round water rod geometriesRay-traced radiation view factors

Additional valve and pump typesActive pressure boundary conditionAdditional heat structure boundary conditionsSpherical heat structure geometryNew signal variable, control block, and triptypes

Command line argument supportExtended TRAC-B-style outputImproved code robustnessPlatform-independent graphics and dump �les

Automatic sorting of control blocks, signalvariables and tripsEnhanced input checking

Advanced BWR Channel Features

Extended Component Features

Usability Enhancements

RELAP5, TRAC-P, and TRAC-B Input DeckConversion

Additional Working Fluids (H O, D O, Air, N ,He, Na, PbBi)

Generalized Support for Coarse-GrainedParallel and Coupled-Code Computations

SETS & Semi-Implicit Numerical Schemes

User-De�ned Matrix Solvers

1D & 3D Kinetics (through PARCS coupling)

Advanced 1D & 3D Level Tracking

Trace Species Tracking

ASME Steam Tables

New Re�ood Model

Improved Choked Flow Model

Enhanced User-De�ned Material Tables

2 2 2

TRACE Tall.pdf 1/19/06 4:21:49 PM

TRACE Support for 50.46 Break Size Redefinition

nModern BWR Channel FeaturesvPartial length fuel rodsvSquare, cross, and round water rod geometriesvRay-traced radiation view factorsnExtended Component FeaturesvAdditional valve and pump typesvActive pressure boundary conditionvSpherical heat structure geometryvNew signal variable, control block, and trip types

nUsability EnhancementsvCommand line argument supportvExtended TRAC-B-style outputvImproved code robustnessvPlatform-independent graphics and dump files

vAutomatic sorting of control blocks, signal variables and tripsvEnhanced input checkingnRELAP5, TRAC-P, and TRAC-BInput Deck ConversionnAdditional Working Fluids (H2O, D2O, Air, N2, He, Na, PbBi)nGeneralized Support for Coarse-Grained Parallel and Coupled-Code ComputationsnSETS & Semi-Implicit Numerical SchemesnUser-Defined Matrix Solversn1D&3D Kinetics (through PARCS coupling)nAdvanced 1D & 3D Level TrackingnASME Steam TablesnNew Reflood ModelnImproved Choked Flow ModelnEnhanced User-Defined Material Tables

ESBWR Passive Safety Systems

nThe ESBWR passive safety systems have strong coupling between the reactor and the containment. nECCS SystemvRelies on depressurization like operating BWRsvGravity driven cooling system (GDCS) to refill reactor system after blowdown.nDecay Heat Removal SystemvLarge passive tube condensers (PCCS) to remove decay heat in long term cooling.

ESBWR Accident Phases

New TRACE Physical Models

Film condensation models appropriate for modeling tubes and containment walls havebeen added to TRACE.

TRACE Assessment for ESBWR

nSeparate Effects Test AssessmentvVoid fraction and level swellvTube condensationvFlat plate condensation

nIntegral Test AssessmentvFIST BWR full pressure blowdownvPUMA late GDCS to long term coolingvPANDA long term cooling

Current Status

nNew film condensation models have been added and are being assessed.nIntegral test assessments are in progress.nPlant calculations are in progress.

“To have the capability to perform T/H safety analysis in the future that allows for solutions to the full spectrum of important nuclear safety problems in an efficient and effective manner, taking complete advantage of state-of-the-art modeling, hardware, and software capabilities.”

TRACE Project Goals

We must be able to reduce and consolidate personnel resources needed for solving any given problem and for maintaining code capability by developing and/or improving:vEase-of-usevSpeedvRobustnessvFlexibilityvMaintainability/upgradeability

We must be able to accommodate the new challenges and demands for best-estimate T/H analysis coupled to other related capabilities:vAccuracyvFlexibilityvMaintainability/upgradeabilityvSimplicityvExpanded scope of capabilitiesvQuality assurance

nNRC relied on 4 T/HcodesvPWRwRELAP5 ‹ SBLOCA and transientswTRAC-P ‹LBLOCAvBWRwRAMONA ‹3D Kinetics and stabilitywTRAC-B ‹LOCA’s and transients

nOver time the differences eroded but coding and input varied substantially

nThe suite was developed in the 70’s and 80’s and does not take advantage of modern technologyvOld coding language and procedural stylevLarge container arrayvArchaic memory saving schemes (bit-packing)nIdentified modeling deficiencies for the same phenomena

nArchitectural and modeling improvements required to ameliorate the limitationsvNRC would have to expend 4 times the resources to continue making improvements to 4 separate tools

nContinue to support old technology or invest in new technology?

nEvolve from existing code base or “develop from scratch”?vEvolve!wAlways have a running productwTakes advantage of current knowledge centers

Historical Perspective

TRACE AssessmentnThe TRACE code is under development, but significant assessment has been performed with recent code versions.nApplicable integral assessment cases include:vROSA SBLOCA IETs (6 tests)vBETHSY ISP-27

ROSA SB-CL-18 (ISP 26) Assessment

Bethsy Test 9.1B (ISP-27) TRACE Simulation

TRACE Support for ESBWR Design Certification

Able to Model All Reactor Designs

Modern Architecture

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