Numerical modelling of direct contact condensation

of steam in BWR pressure suppression pool

system

Gitesh Patel, Vesa Tanskanen, Juhani Hyvärinen

LUT School of Energy Systems/Nuclear Engineering, Lappeenranta University of

Technology, Finland

Nuclear Science & Technology Symposium - NST2016 Helsinki, Finland, 2-3 Nov. 2016

Outlines

Motivation

Objective

POOLEX facility

Numerical models and simulations details

Results

Summary

Current work

Gitesh Patel 2NST 2016, 2-3 Nov., Helsinki Nuclear Engineering, LUT, Finland

In a BWR, the suppression pool is

one of the key safety systems

during a loss of coolant accident

(LOCA) or safety valve actuation.

Suppression pool provides a large

pressure and heat sink by

condensing vapor into liquid and

absoring the energy disharge from a

reactor vessel.

Motivation

3Gitesh Patel

Containment(a)

(a) http://www.tvo.fi/uploads/File/nuclear-power-plant-units.pdf

NST 2016, 2-3 Nov., Helsinki Nuclear Engineering, LUT, Finland

Motivation (cont.)

4

The sub-cooling of the pool liquid and the mass flux of injected vapor determine

the character of occuring of direct contact condensation (DCC).

Injected steam interacts with pool water by heat transfer, rapid condensation

and momentum exchange, inducing hydrodynamics loads to the pool

structures.

(a) R. Lahey, and F. Moody, (1993). The Thermal-Hydraulics of a Boiling Water Reactor, 2nd edn. American Nuclear Society.

Gitesh Patel

Schematic of typical regions for condensation modes during SRV or LOCA blowdown in BWR(a)

NST 2016, 2-3 Nov., Helsinki Nuclear Engineering, LUT, Finland

Objective

To implement two-phase solver of OpenFOAM CFD code

To simulate DCC phenomena appearing in BWR suppression pools

Validation of results

5Gitesh PatelNST 2016, 2-3 Nov., Helsinki Nuclear Engineering, LUT, Finland

POOLEX facility

6

The POOLEX (Condensation Pool Experiment) test facility was a scaled down

representation of a suppression pool wetwell.

Gitesh Patel

(a) Laine, J. and Puustinen, M., (2006), Condensation Pool Experiments with Steam using Insulated DN200 Blowdown Pipe,

Research report POOLEX 03/2005, LUT.

NST 2016, 2-3 Nov., Helsinki Nuclear Engineering, LUT, Finland

POOLEX(a)

POOLEX facility: STB-28 test

The STB-28 test was aimed to investigate steam bubble formulation and its

condensation at the blowdown pipe outlet as a function of pool water temperature.

During the blowdown, seven short time intervals in the range of 12 s to 30 s were

recorded with a higher sampling rate. These sub tests were labelled from STB-28-1

to STB-28-7.

7Gitesh PatelNST 2016, 2-3 Nov., Helsinki Nuclear Engineering, LUT, Finland

Numerical models and simulations details

Eulerian-Eulerian two-fluid approach was used in OpenFOAM.

8

Flow turbulence was solved by employing the k-ε turbulence model.

PIMPLE (PISO-SIMPLE) pressure velocity coupling algorithm was applied.

Gitesh Patel

(Energy Eq.)

(Continuity Eq.)

(Momentum Eq.)

NST 2016, 2-3 Nov., Helsinki Nuclear Engineering, LUT, Finland

The interfacial heat fluxes were solved as,

9

,,, iiSi HTTHTCQ

tL

NuHTC

aibi

bSbiaSai

biaiHH

TTHTCTTHTC

,,

,,

,,

Gitesh Patel

Numerical models and simulations details (cont.)

2

1

PrRe2

tNu

b

ttbt

Lv

Re

4

13

tL 4

1

)(tv

(a)

Hughes and Duffey (1991)

(a) Hughes, E.D., Duffey, R.B., (1991). ‘Direct contact condensation and momentum transfer in turbulent separated flows’. Int. J.

Multiphase Flow 17, 599-619

NST 2016, 2-3 Nov., Helsinki Nuclear Engineering, LUT, Finland

2D-axisymetric grid

3D grid

• 2D-axisymmetric grid contains 45626 hexahedral cells.

• Full 3D grid contains 302796 hexahedral cells.

Test conditions (STB28-4):

• steam temperature: 379.1 K;

• water temperature: 340.5 K;

• steam mass flow rate at inlet: 0.238 kg/s;

• water in the pool: hydrostatic pressure;

• steam-water interface at t=0 s: 0.76 m in the pipe.

Gitesh Patel 10NST 2016, 2-3 Nov., Helsinki Nuclear Engineering, LUT, Finland

Numerical models and simulations details (cont.)

Grid Convergence Index (GCI) method was used.

Relative error Extrapolated relative error

Grid Convergence Index (GCI)

Results

Condensation mass flow rate Interfacial area

Gitesh Patel 11NST 2016, 2-3 Nov., Helsinki Nuclear Engineering, LUT, Finland

12

STB-28 experiment

Gitesh Patel

STB-28-4 (OpenFOAM)

NST 2016, 2-3 Nov., Helsinki Nuclear Engineering, LUT, Finland

Results (cont.)

Results (cont.)

NEPTUNE_CFD

(V. Tanskanen, 2012)

OpenFOAM

(incompressible solver)

OpenFOAM

(compressible solver)

2D results

Gitesh Patel 13NST 2016, 2-3 Nov., Helsinki Nuclear Engineering, LUT, Finland

Results (cont.)2D results

• The incompressible is

inadequate for

chugging simulations.

• Visually, the chugging frequency is higher but the amplitude of interface position in

blowdown pipe is lower in the OpenFOAM case than in the NEPTUNE_CFD

simulations.

• The DCC rate in the

OpenFOAM simulations

is relatively high than to

the DCC rate of

NEPTUNE _CFD

simulations.

Gitesh Patel 14NST 2016, 2-3 Nov., Helsinki Nuclear Engineering, LUT, Finland

Results (cont.)Penetration of the initial steam jet

Eruption and collapse of the bubble

after the steam jet penetration

3D results

Gitesh Patel 15NST 2016, 2-3 Nov., Helsinki Nuclear Engineering, LUT, Finland

2D-axisymetric grid

• 72089 hexahedral cells.

16Gitesh Patel

PPOOLEX simulations (DCC-05-4 test)

Current work…

NST 2016, 2-3 Nov., Helsinki Nuclear Engineering, LUT, Finland

Summary

17

The suppression pool is one of the key safety systems of BWR containment.

Two-phase flow solver of OpenFOAM CFD code was implemented.

The HD DCC model based on surface renewal model was employed.

As the reference, the steam blowdown tests of the suppression pool test facilities of

Lappeenranta University of Technology were used.

Previously simulated results of NEPTUNE_CFD code were utilised for the assessment

of OpenFOAM simulations.

The qualitative and quantitate behavior of the steam-water interface agreed well to the

test results in the simulations with the OpenFOAM and NEPTUNE_CFD CFD solvers.

An adequate grid size and compressible solver are crusial for chugging simulations.

Gitesh PatelNST 2016, 2-3 Nov., Helsinki Nuclear Engineering, LUT, Finland

Acknowledgements

The research leading to these results was funded by the Finnish Nuclear Waste

Management Fund (VYR) via SAFIR2014 and SAFIR2018, and Doctoral Programme

for Nuclear Engineering and Radiochemistry (YTERA).

NST 2016, 2-3 Nov., Helsinki Nuclear Engineering, LUT, Finland 18Gitesh Patel

Thank You For Your Attention !