advanced methods for bwr transient and stability …...transient subchannel thermal hydraulics 3d...

Advanced Methods forBWR Transient and Stability Analysis

F. Wehle, S. Opel, R. VeltenFramatome ANP GmbH

P.O. BOX 322091050 Erlangen Germany

Advanced Methods for BWR Transient and Stability Analysis, F.Wehle, Framatome ANP2

KTG-Fachtagung „Reaktorbetrieb und Kernüberwachung“, 13.-14. Febr. 2003, FZ-Rossendorf

Advanced Methods for BWRTransient and Stability Analysis

> Background and Overview of Framatome ANP’s

BWR Methodology

> Application of the Advanced Transient Analysis

> OECD/NRC Boiling Water Reactor Turbine TripBenchmark

> KATHY-Loop Stability Measurements



Challenges for Design and Operation ofModern BWR Fuel Assemblies and Cores

> Framatome ANP � Advanced fuel design� Modern core loading concepts� High operational flexibility

> Design Tools � Comprehensive physical modelling� Qualified single codes and code

systems

>Customer Optimal fuel utilization for safe, reliableand highly flexible reactor operation



Overview of Framatome ANP’s BWRMethodology

Fuel Assembly

Plant Transients

Core Transients

CASMO-4Neutronics Lattice

THRP2-Phase Thermal

Hydraulics

CAROThermo-

Mechanical

MCNPMonte-Carlo

RINGSSubchannel

Analysis

MICROBURN-B2Core Simulator

POWERPLEX/FNR-KOnline Core Monitoring

PRIMO-BLoading Pattern

Optimization

STAIFStability in Frequency

Domain

RAMONA-33D-Space-Time

Kinetics

VERENA(RELCOS)/COSBWR/FRANCESCAPlant Analysis

COBRA-TFTransient Subchannel

Thermal Hydraulics

3D Core Steady State



Overview of Framatome ANP’s BWRMethodology

Fuel Assembly

Plant Transients

Core Transients

CASMO-4Neutronics Lattice

THRP2-Phase Thermal

Hydraulics

CAROThermo-

Mechanical

MCNPMonte-Carlo

RINGSSubchannel

Analysis

MICROBURN-B2Core Simulator

POWERPLEX/FNR-KOnline Core Monitoring

PRIMO-BLoading Pattern

Optimization

STAIFStability in Frequency

Domain

RAMONA-53D-Space-Time

Kinetics

S-RELAP/RAMONA-5Best Estimate Plant Analysis, 3D Core Representation

COBRA-TFTransient Subchannel

Thermal Hydraulics

3D Core Steady State



3D Transient Code RAMONA 3

- Neutronics: 11/2-Group Diffusion Model

- Thermal Hydraulics: 4-Equation Drift Flux Model

- BWR System Components: Pumps, Separators, Steam Line,Reactor Protection System

Validation:- Peach Bottom Turbine Trip- Spert Reactivity Insertion Experiments- Ringhals Stability Benchmark- Validation against Plant Stability Measurements and Operational Transients- GUN C Cycle 12 and 13 (global and regional instabilities)



RAMONA – Hydraulic Model Components

Lower Plenum 1

Steam Separator

Stand Pipes

Upper Plenum

Byp

ass

Lower Plenum 2

Steam Dome

Downcomer 1

Downcomer 2

Parallel Channels

Core

Feedwater

S/R-Valves

MSIV

Bypass

Turbine-Valve



BOC - Core Averaged Axial Power



BOC – Radial Power Factors



EOC - Core Averaged Axial Power



Comparison of the Fission Powers



Limiting Case – Radial Factor of Hot & Cold Channel



Limiting Case – MCPR of the Hot Channel



BWR Turbine Trip Benchmark

> Exercise 1

� Power vs. Time plant system simulation with fixed axial power profile

table is given => thermal-hydraulic system response

> Exercise 2

� Coupled 3D and/or 1D kinetics/core thermal-hydraulic BC model

� Hot zero power.

� Hot full power and transient using the provided core BC.

> Exercise 3

� Best-estimate coupled 3D core/thermal-hydraulic system modeling



Plant Code S-RELAP5

> S-RELAP5 is based on RELAP5/MOD2 and incorporateselements of RELAP5/MOD3 and RELAP5-3D

> Special Features:

- 2-dimensional component model

- improved formulations for energy and momentum equations

- modified heat transfer and hydrodynamic constitutive models

- special fuel modeling

- suited for best-estimate licensing methods



Exercise 3: Fission Rate



Exercise 3: Dome Pressure



Advanced Transient Methodology - Summary

> Advanced method reduces OLMCPR by app. 0.07compared to the conservative 1D methodology

> The method allows more operational flexibility.

> The advanced transient method has already beenapproved by TÜV NORD.

> Based on the OECD/NRC BWR Turbine TripBenchmark the transient applicability of the codesystem S-RELAP5/RAMONA5 has been provensuccessfully.



Heat Flux

Rod Temperature

Thermal Power

Neutron Flux

Reactivity

Void ReactivityCoefficient

Void Fractionδαδαδαδα

δαδαδαδα

δ∆δ∆δ∆δ∆pI

δ∆δ∆δ∆δ∆ pII

Inlet Flow Rate

Exit Flow Rate

Thermal Hydraulics

(Core and External Loop)

Neutronics Feedback

δ∆δ∆δ∆δ∆ pII

= - δ∆δ∆δ∆δ∆pI

Feedback Mechanisms of BWR Stability



Most Sensitive Stability Parameters

Fuel Assembly Parameters Effect on StabilityFlow Area +Hydraulic Diameter +Loss Coefficient LTP +Loss Coefficient UTP -Loss Coefficient Spacer -Fuel Time Constant +Void Coefficient +

Operating ParametersAxial Peaking Factor -Radial Peaking Factor -Reactor Power -Reactor Mass Flow +Inlet Subcooling -



Multifunction Thermal Hydraulic Test LoopKATHY

Direct contactcondenser

P≤ 9,5MW

el.

Pressurizer

Natural CirculationLoop

Controlvalve

Controlvalve

Void FractionMeasurementDevice

P ≤ 15 MWel.

Downcomer

Water steamseperator

Circulationpump

PWRTest Vessel

10 MW

5MWHigh pressurecoolers

p ≤ 185 bar

p ≤ 110 bar

BWRTest Vessel

Feedwater

Tocon-enser



KATHY Stability Test Loop

ζζζζinlet

ζζζζexit

ζζζζspacer

ζζζζspacer

ζζζζspacer

ζζζζspacer

ζζζζspacer

ζζζζspacer

ζζζζspacer

Axial Power Profile

Downcomer

Steam Separator + Expansion Chamber

TestSection

1.0 1.60.

Riser



Steady State Flow Rate

Bundle Power (MW)

Flow Rate

ζζζζexit= 7.5

Inlet Subcooling: 124 kJ/kg

Inlet Subcooling: 144 kJ/kg

CPR = 1

CPR = 1

DR = 1

DR = 1

(kg/s)

ζζζζexit= 1.5



KATHY Stability Test Data

DR: 0.77



Transient Dryout During Instability



Comparison of STAIF Results with KarlsteinStability Tests



Transient Dryout Tests SimulatingTypical Limiting Transients

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

Time

Sta

nd

ard

ized

valu

es

PowerSystem pressureMassflow

250

260

270

280

290

300

310

320

330

340

350

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

Time

Tem

per

atu

re

System data during turbine trip

Rod temperature response duringturbine trip



Conclusions

> Safe, reliable, and flexible BWR operation requires fuelassembly and core designs optimized for all reactor operatingconditions.

> The comprehensive methodology of Framatome ANP meets thechallenges to analyze and predict steady-state and transientBWR operation.

- The methodology is based on state-of-the-artphysical modeling.

- It has been thoroughly qualified, using a largedatabase including recent, sophisticated, and highlyaccurate measurements.

- The code system is further developed and qualifiedcontinuously.

advanced methods for bwr transient and stability …...transient subchannel thermal hydraulics 3d...

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