Thermofluid Dynamic Analysis for THAI Tests with … 2017 Warsaw, Poland 8TH CONFERENCE ON SEVERE...

May16-18, 2017

Warsaw, Poland

8TH CONFERENCE

ON SEVERE ACCIDENT

RESEARCH

ERMSAR 2017

Thermofluid Dynamic Analysis for THAI

Tests with Passive Hydrogen Recombiner

Masatoshi Sato, Toshinori Matsumoto,

Tomoyuki Sugiyama and Yu Maruyama

Japan Atomic Energy Agency

ERMSAR 2017, Warsaw, May 16-18, 2017

Background and Objectives

• Hydrogen production by the steam-zirconium chemical reaction is a significant concern in a severe accident.

• The passive autocatalytic recombiner (PAR) is one of the countermeasures to prevent the occurrence of

hydrogen deflagration/detonation in the containment vessel or reactor building.

• JAEA has developed the evaluation technique of severe accident countermeasures. In order to develop PAR

evaluation technique, thermofluid dynamic analyses were performed on the HR tests conducted in the

OECD/NEA THAI project.

• In the previous study, we carried out a simulation on the test HR5 as a first step to develop PAR evaluation

techniques. In this study, we performed simulations on the HR3 and HR12 to evaluate the validity of models

for extended conditions in terms of temperature, pressure, and steam concentration.

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HR Tests

3

Height : 9.2m

Inner diameter : 3.2m

Volume : 60m3

THAI test vessel (OEDE/NEA, 2010)

PAR

Ring feed line for hydrogen

Initial conditions

HR3

Air

Pressure : 1.485 bar

Temperature : 29.9°C

HR12

Air + 61% steam


Temperature : 115.0°C

HR5

Air


Temperature : 32.0℃


Hydrogen Injection and Experimental Results

4

HR5

• In the all cases, the hydrogen was

injected twice with interval time.

• Recombination rate and pressure

increase during the hydrogen

injection.


Simulation Code and Computational Grid

5

PAR

Ring feed line

Thermal fluid dynamic code

Computational Grid

[J/kg]101.2OHO2

1H 8

222

Total number of cells : 1,052,789

Model of the PAR

OpenFOAM 3.0.1

Modified ‘reactingFoam’ solver to simulate PAR functions

H2 recombination rate

• AREVA correlation

• Function of

- H2 concentration

- O2 concentration

- Total pressure

Cata

lyst

Inlet channel

Outlet

channel


Conditions for Simulation

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Initial Conditions H2 Injection History

HR3 HR12 HR5 (reference)

Pressure (bar) 1.485 2.924 2.934

Temperature (°C) 29.9 115.0 32.0

O2 (vol%) 21.0 8.2 21.0

H2 (vol%) 0.0 0.0 0.0

H2O (vol%) 0.0 61.1 0.0

N2 (vol%) 79.0 30.7 79.0

Turbulent model

・SST k-omega

Boundary Conditions Thermal Constant wall temperature Momentum No slip Turbulence Wall function


Simulation Result (HR12)

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H2 Volume Fraction

Vertical Cross

Section

20min 60min 130min

(A) 20min (B) 60min (C) 130min

(A) 20min (B) 60min (C) 130min

Time : 0.0 – 32.0, 112.0 - 170.0 min.

• With H2 injection

• Increasing temperature by heat

generation in the PAR

Time : 32.0 - 112.0 min.

• No H2 injection

• Decreasing H2 volume fraction by

recombination

Temperature

PAR H2 ring

feed line

A B C

0.0

XH2 (%) 3.6

26.9

T (℃) 226.9

1.8

2.7

0.9

176.9

126.9

76.9


Flow Velocity

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HR12 at 40 minutes

Upward flow is developed in the PAR due to the

natural convection driven by the reaction heat in

the hydrogen recombination.

The gas flow rises along the wall to the vessel roof

and turns into the downward flow at the wall in

the opposite side.

Significant difference was not observed in the flow

velocity field in the all tests. Upward flow

1.5

1.0

0.5

0.0

Velocity (m/s) 2.0


Hydrogen Recombination Rate

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All cases In the phase of the first hydrogen injection and the following recombination, the simulation results were in good

agreement with the experiments.

HR12, HR5 The difference from the experiment became larger late phase.

HR3 HR12 HR5


Pressure in the Vessel

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HR3 • The simulation was relatively in good agreement with the experiment. In particular, HR3 got a good result.

All cases • The simulation results, especially in the HR12 and HR5 tend to be higher than the experimental results.

• Possible reason

-> The absence of the steam condensation ?

HR3 HR12 HR5


Steam Concentration in the Test HR12

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Point B

Point A

Measuring points Steam Concentration

The difference between the experiment and simulation became larger as increasing time.

The difference is small in the early phase, at which deviation in the recombination rate started.


Possibility of Steam Condensation in the Experiments

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50 100 150

0

1

2

Average gas temperature (°C)

Estim

ate

d s

team

part

ial

pre

ssure

(bar)

HR3

HR12

HR5

Steamsaturationpressure

The estimated steam partial pressure exceeded the

saturation pressure only in the test HR5.

• Significant steam condensation did not occur in

the tests HR3 and HR12.

->The absence of the steam condensation was

not the primary reason of the

disagreements of the hydrogen

recombination rate in the late phase of the

test HR12.

Relationship Between steam partial pressure and saturation pressure during tests


Hydrogen Concentration at PAR

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All the simulation results generally agree with the experimental results in the phase of the first hydrogen injection and

the following recombination.

HR3 HR12 HR5 PAR outlet

PAR inlet


Conclusions

• Thermofluid dynamic simulations were carried out on the hydrogen recombination tests HR3, HR12 and

HR5 of the OECD/NEA THAI project with modified reactingFoam solver to simulate PAR functions.

• Results of the simulations agreed well with the experimental results. Therefore, the analysis showed the

effectiveness of the present simulation technique.

• Further improvement of the simulation technique are needed to achieve high accuracy and reliability of the

PAR performance simulation in the containment vessel and reactor building.

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Thermofluid Dynamic Analysis for THAI Tests with … 2017 Warsaw, Poland 8TH CONFERENCE ON SEVERE...

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