Multi-Phase Modelling Capabilities of the RELAP5 Thermal ... · • Essentially 1D thermal-hydraulics, but 2D or 3D is used in specific components (crossflow) • 1D or 2D heat conduction

József Bánáti

Chalmers University of TechnologyDepartment of Nuclear Engineering

E-mail: [email protected]

Multi-Phase Modelling Capabilities of the

RELAP5 Thermal-Hydraulic System Code

J. Bánáti, SIAMUF Seminar 2005-10-21

Background• RELAP5: Reactor Excursion and Leakage Analysis Program• Originally developed by the US Nuclear Regulatory Commission• Started in the late ‘70s as a domestic project at INEL• Currently applied world-wide

• Users:• Regulatory bodies, safety authorities• Scientific and educational institutions• Power industry, plant and facility designers

• Fields of application:• Licensing audit calculations• Safety evaluation of NPPs• Simulation of transients or accidental scenarios• Design of small or large-scale experimental facilities


Features of RELAP5

• Use of nonhomogeneous, nonequlibrium, 6 equation, 2-fluid model• Effects of noncondesable gases and boron taken into account• Liquid: H2O, D2O, Gas: vapour + {air, N2, O2, H2, ...}• Essentially 1D thermal-hydraulics, but 2D or 3D is used in specific

components (crossflow)• 1D or 2D heat conduction in system structures• Convective & radiative heat transfer between fluid and structure• Specific flow models (default or user-selectable):

• Critical flow, abrupt area change, CCFL, thermal stratification, ...• Variety of pre-defined components:

• Pipe, branch, junction, valve, separator, pump, turbine, accumulator, con-trol system, ...


Spatial Discretisation


The Finite-Difference EquationsContinuity:

Momentum:

VL αg L,n ρg L,

n 1+ ρg L,n–( ) αf L,

n ρf L,n 1+ ρf L,

n–( ) ρg L,n ρf L,

n–( ) αg L,n 1+ αg L,

n–( )+ +[ ]

α· g j 1+,n ρ· g j 1+,

nvg j 1+,

n 1+ Aj 1+ α· g j,n ρ· g j,

nvg j,

n 1+ Aj–( )+ Δt

α· f j 1+,n ρ· f j 1+,

nvf j 1+,

n 1+ Aj 1+ α· f j,n ρ· f j,

nvf j,

n 1+ Aj–( )Δt+ 0=

αgρg( )jn vg

n 1+ vgn–( )jΔxj αfρf( )j

n vfn 1+ vf

n–( )jΔxj12--- α· gρ· g( )j

nvg

2( )Ln

vg2( )K

n–[ ]Δt+ +

12--- α· fρ· f( )j

nvf

2( )Ln

vf2( )K

n–[ ]Δt

12--- α· gρ· g( )j

nVISGj

n α· fρ· f( )jnVISFj

n+[ ]Δt–+

PL PK–( )n 1+ Δt– ρm( )jn[ Bx αgρg( )j

nFWGjn vg( )j

n 1+– αfρf( )jnFWFj

n vf( )jn 1+–+=

Γg( )jn vg vf–( )j

n 1+ ]ΔxjΔt– α· gρ· g( )jnHLOSSGj

nvg j,n 1+ α· fρ· f( )j

nHLOSSFj

nvf j,n 1++[ ]Δt–


Energy:

For closure relations, a large number of correlations are built into the code. These are based on well qualified experimental datasets.

The actual flow pattern is determined by using flow regime maps.

VL ρf L,n Uf L,

n PLn+( )– αg L,

n 1+ αg L,n–( ) αf L,

n Uf L,n ρf L,

n 1+ ρf L,n–( ) αf L,

n ρf L,n Uf L,

n 1+Uf L,

n–( )+ +[ ]

α· f j 1+,n ρ· f j 1+,

nU· f j 1+,

nPL

n+( )vf j 1+,n 1+ Aj 1+ α· f j,

n ρ· f j,n

U· f j,n

PLn+( )vf j,

n 1+ Aj–[ ]Δt+

hf*

hg* hf

*–----------------

⎝ ⎠⎜ ⎟⎛ ⎞

⎩⎨⎧

L

nPs L,

n

PLn

---------Hig L,n TL

s n 1+,Tg L,

n 1+–( )

hg*

hg* hf

*–----------------

⎝ ⎠⎜ ⎟⎛ ⎞

L

n

Hif L,n TL

s n 1+,Tf L,

n 1+–( )+=

PLn Ps L,

n–

PLn

---------------------⎝ ⎠⎜ ⎟⎛ ⎞

+ Hgf L,n Tg L,

n 1+Tf L,

n 1+–( ) 1 ε+

2------------⎝ ⎠

⎛ ⎞ hg L,′ n, 1 ε–

2-----------⎝ ⎠

⎛ ⎞ hf L,′ n,+– Γw L,

n Qwf L,n DISSf L,

n }VLΔt+ +


Flow Regime MapsHorizontal:

Vertical:

Horizontally stratified (HST)

Increasing void fraction αg

BBY-HST

SLG-HST

SLG/ANM-HST

ANM- MPR-HST

Mist(MPR)

Annularmist

(ANM)SLG/ANM

Slug(SLG)

Bubbly(BBY)vcrit

1/2vcrit

Increasingrelativevelocity|vg- vf |

αBS αSA αAM

HST

αDE

and massflux Gm

and 2500kg/m2-s

and 3000kg/m2-s

0.0 1.0

Vertically

stratified (VST)

Transition

Unstratified

Bubbly(BBY)

SLG/ANM

Annularmist (ANM)

Slug(SLG)

Mist(MST)

Invertedslug (ISL)

IAN/ISL

BBY-IAN

Invertedannular

IAN/ISL-

SLG

ISL-SLG/

ANM

Post-dryout

Transition

Pre-CHF

vTb

αBS αSA αAMvm

αBS αSA

(MPR

)

(MPO

)

Increasing

Increasing αg

αDE

(IAN)

αCD

ANM/MSTSLG/ISL

αAM0.0 1.0

0.0 1.0

Incr

easi

ngT g

- Ts

1 vTb2


The SNAP Graphical User Interface for RELAP5


Animation Mask for a Typical PWR


Application of RELAP5 at Chalmers: Power Uprate of the Ringhals-3 Nuclear Power Plant

• Increase of power from 100% to 113.5% in 2 stages:• Steam generator replacement• High burnup fuel + hardware changes

• Project granted by SKI (Swedish Nuclear Inspectorate)• Acting as a TSO (Technical Support Organisation)• Methodology to perform independent safety analysis with TH coupled to

neutron kinetics:• Development of a steady-state model• Analysis of the consequences of higher power• Selected limiting transients:

• Steam line break• Unintentional control rod withdrawal, • Feedwater disturbances• LOCA


Nodalization of the Ringhals-3 NPP

11 12 13

440

205 206 207

5

3

15

20 21

25

30

35

6162

65 60 41 40

5068

6770

71

72

75

330

326 331

320 340

305

383390 385386 381

906 928 495

497

498

441

350

380

496

905

461

463

462

460

945

941

942

940

918

916

915

910

943

932

930

931

933

405

435

220 240

226

226

431

231

231

230

283

290

285

286

281 280

904

925 493 250947

924

903

120 140

130

105

450

948

927

316346

216

246

116146

150491922902

180185 181183186190

492

901

946

921

451

494

911

66

RELAP5 Nodalization of the

Primary Side of Ringhals-3

Loop 3

Loop 2

Loop 1

SG 3

SG 2

SG 1

Pre

ssu

rize

r

Accu 3

Accu 2

Accu 1

Bo

ron

Tan

k

Ch

arg

ing

Lin

e

Do

wn

co

mer

Co

re

RHR 2

RHR 1

Normal Letdown

Safety Valve

ECCMixECCMix

ECCMix

ECCMixECCMix

ECCMix

PORV

4


Steady-State Results

0 50 100 150 200Time (s)

4400

4500

4600

4700

4800Fl

ow R

ate

(kg/

s)

mflowj-105010000mflowj-205010000mflowj-305010000

Primary Side Mass Flowrates



0 50 100 150 200Time (s)

500

520

540

560

580

600Fl

ow R

ate

(kg/

s)

mflowj-561000000mflowj-661000000mflowj-761000000

Steam Mass Flowrate



0 50 100 150 200Time (s)

550

560

570

580

590

600V

olum

e L

iqui

d T

empe

ratu

re (

K)

tempf-120010000tempf-220010000tempf-320010000tempf-190010000tempf-290010000tempf-390010000

Hot and Cold-Leg Temperatures


Benchmark Case: IAEA SPE-4

• Standard Problem Exercise No. 4 (SPE-4)• Supervised by the International Atomic Energy Agency (IAEA)• Transient: 7.4% Small-Break Loss of Coolant Accident (LOCA) in VVER-

440 type reactor simulated in a 1:2000 scaled-down model• Test facility: PMK-2 (Budapest, Hungary)• Focusing on prediction of the dry-out phenomenon• RELAP5 performed very well: good simulation of the rod temperatures and

system pressure


Results of IAEA SPE-4

420

440

460

480

500

520

540

560

580

600

620

640

0 200 400 600 800 1000 1200 1400 1600 1800

TE

MP

ER

AT

UR

E [K

]

TIME [s]

Rod surface temperature (h=2.954 m)

RELAP5TE12


Results of IAEA SPE-4

0

2

4

6

8

10

12

14

0 200 400 600 800 1000 1200 1400 1600 1800

PR

ES

SU

RE

[MP

a]

TIME [s]

Pressure in upper plenum (h=3.754 m)

RELAP5PR21


Concluding Remarks

• RELAP5 is an excellent tool for analysis of complex TH processes• The code is applicable in many fields beyond nuclear (e.g. chemical,

pressurised tank blowdown, 2-phase flow analysis in pipelines, etc.)• Continuous improvement is provided by the CAMP agreement• User feedback is taken into account in new versions• Coupling to CDF and neutron kinetic applications is established

Thank you for your attention!


Documents

Multi-Phase Modelling Capabilities of the RELAP5 Thermal ... · • Essentially 1D thermal-hydraulics, but 2D or 3D is used in specific components (crossflow) • 1D or 2D heat conduction