LORELEILight water One-Rod Equipment

f L E i t l I ti tifor Loca Experimental Investigations

Preliminary Thermo-hydraulic Design

Francesco Saverio Nitti

with support of: Serge Bourdon Christian Gonnier Patrick Roux

Roma 10 November 2011

with support of: Serge Bourdon, Christian Gonnier, Patrick Roux 

LORELEI : Light water One-Rod Equipmentfor Loca Experimental Investigationsfor Loca Experimental Investigations

The test device is developed for LOCAt i t t di i l f l dtransient studies on single fuel rod.

The studies are focused on the evaluation of thermomechanicalaspects and radiological consequences.

The device will be installed on a“displacement system”,in the core reflector ensuring :in the core reflector, ensuring :

Easy power control.Easy power control.Even during the operating cycleof the core

Safety. By a quick displacement in a safe“back position”back position .

LORELEI : Objective

The device offers representative conditions for:

Thermal-mechanical behaviour of a LWR rod

Ballooning and burst of the claddingCorrosion phase at high temperature (oxidation and hydration)p g p ( y )Quenching of the claddingPost-quench behaviour of the fuel rod

Radiological consequencesFission Prod ct releaseFission Product release

Source: IRSN

LORELEI : Experimentation

1 R i di i1 - Re-irradiation- Natural circulation- Pressure: 130 bars, Tsat (130 bars)

Three steps experiment

- Representative thermal condition- No representative water flow- Linear power < 400W/cm

experiment

Linear power 400W/cm- Fission product inventory

2 - Dry out and high temp. transient y g p- Gas injection to dry out- Low pressure: 2-5 bars- Linear power 10-20 W/cm

3 - Quenching- Water injection- Linear power 10-20 W/cm

- Temperature increase 10-20°C/s- Azimuthal temperature homogeneity

W t t diti

Water injection - Low temperature, pressure - Fission gas release

- Water steam conditions

LORELEI : Thermo-hydraulic design activity

Main steps of the preliminary thermo-hydraulic design activity:Main steps of the preliminary thermo-hydraulic design activity:

Definition of a 3D geometry of the test device

Definition of a numerical model to investigate the thermo-hydraulicbehaviour using the CATHARE code

Development of numerical tests at different powers and geometries

l i f l ddi l i d i hEvaluation of cladding temperature evolution during the LOCA

LORELEI : Device geometry

Starting from a 2D geometry utilized in a former thermomechanicalStarting from a 2D geometry utilized in a former thermomechanicalcalculation a 3D starting geometry was defined

Helium

Hafnium

Porous Zirconia

D

Low

Incon 718

Zirconia

Zi ll

evi

wer p

Upp

by P. Roux

Zircalloy

Fuel

ce

part

per p

Inox 316Waterpartt

LORELEI : Numerical Model/1

Objective

Verify the capacity of the device to operate under natural circulation, moving the thermal

b th d d b fi i i th f lpower, both produced by fission in the fuel rod and generated by gamma irradiation in the structures from the device to a cold well ofstructures, from the device to a cold well of water, surrounding the system.

Fluid temperature below the saturation value

Required Operating Conditions

Fluid temperature below the saturation valueCladding temperature above the saturationvalue, to guarantee nucleation conditionsat the wallSufficient margin for the Critical Heat Flux(CHF)(CHF).

LORELEI : Numerical Model/2

Numerical Code

The numerical calculations were performed with CATHARE 2 V2.5_2, a two-phase thermo-hydraulic code with a 2-fluids and 6-equations model.

Calculation parameters

model.

Input data required

Boundary conditions:- Pressure 13 Mpa

GeometriesMaterial physical properties

- External wall temperature 50 °CNumber of meshes: from 474 to 768Mesh size: from 1 to 10 mm

Local pressure drop coefficientsPower source on fuel

d t t Mesh size: from 1 to 10 mmand structuresBoundary conditions.

Different geometries of the device with different number and length of meshes were studied

LORELEI : Numerical Model/3

Calculation Flow Chart

Numerical calculations with Starting Geometry G0Fuel Power: Up to 400 W/cm

Maximum power processed300 W/cmLarge amount of steam

Variation of geometryis requiredParametric calculationsFuel Power: Up to 400 W/cm

Gamma Power: ZeroLarge amount of steamaccumulated

Parametric calculationsare required

Numerical calculations toAnalytical  Approach to evaluate the  geometrical parameters to be changed 

Numerical calculations to verify the analytical approach 

Numerical calculations to analyze  the variation of  steam with the variation of  geometry.Fuel Power:  300 W/cm

Definition of Geometry G4 with Analytical ApproachF l P 400 W/

Gamma Power: Zero

Fuel Power: 400 W/cmGamma Power: Zero Numerical calculation to verify 

the Geometry G4

Definition of Geometry G5 with Analytical ApproachFuel Power: 400 W/cm

Numerical calculations to analyze  the evolution of Fuel Power: 400 W/cm

Gamma Power: Yes Numerical calculation to verify the Geometry G5

cladding temperature.Fuel Power:  4 to 16 W/cmGamma Power: Zero

LORELEI : Total Heat Exchange. Analytical Approach.

An analytical approach was performed to define the new geometries

With some simplified hypothesis the Global Heat Transfer Coefficient (GHTC)with the surrounding was defined, as function of geometric parameters.

( )eihhrLr 412π

CATHARE calculations were performed to validate the analytical approach

( )ei

cbaeiei

ei TT

rr

krr

krr

khhrrhrhr

hhrLrQ −

⎥⎦

⎤⎢⎣

⎡++++

=

3

4

2

3

1

24141

41

ln1ln1ln12π

LORELEI : Geometries G4 –G5

Main geometries analyzed modifying the three parameters: r1, L, t2

r1 [mm] L [mm] t2 [mm]Max Power on

Fuel Rod [W/cm]

Gamma-Power [W]

DNBRmin

G0 30.54 700 2 300 - 1.30G1 50 54 700 2 300 1 97G1 50.54 700 2 300 - 1.97G2 30.54 1200 2 300 - 1.99G3 30.54 700 1.24 300 - 1.97G4 50.54 1200 1.24 400 - 2.67G5 50.04 1200 0.5 400 3.98*104 2.73

Temperature and Void Fraction behavior at 400 W/cm

LORELEI : Further Investigations

Variation of the mass of steam with the variation of geometrical parameters, at constant power 300 W/cm Reference geometry G0

The variation is function of two opposite effects:

300 W/cm. Reference geometry G0

Heat exchange with the surroundingInterfacial heat exchange

LORELEI : Cladding Temperature Evaluation. G5 geometry

1800

Range of powers: from 1% to 4% of the maxim power, 4oo w/cm.

1200

1400

1600 The calculation of LOCA was not performed.

The calculations were performed: ith h li li fl id

600

800

1000

erat

ure

[°C

]

1f2f

- with helium as cooling fluid- without radiative heat transfer- without gamma-heating in the structures

Different power conditions were performed:

200

400

600

Tem

p 3f4f

Different power conditions were performed:- with power only on the fuel rod- with power only on the electric heater

- with power on the fuel rod and on the 0

0 2000 4000 6000 8000 10000

Time [s]

1516171819

LOCA conditionsPower: 10-20 W/cm

pelectric heater

fuel

89

101112131415

[°C

/s]

1f2f3f

Power: 10 20 W/cmTemperature range: 600 – 800 °CTemperature gradient : 10 – 20 °C /s

fuel

2345678

dT/d

t

4fThese preliminary calculations showed the incapacity of the device to reproduce the LOCA conditions.

012

0 500 1000 1500 2000Temperature [°C]

A further variation of the geometries is need.

electric heater

LORELEI : Conclusion

Conclusions

• The system selected is able to work in natural circulation up to a power• The system selected is able to work in natural circulation, up to a power of 400 W/cm on the fuel rod and gamma-power on the structures

• The liquid bulk temperature is under the saturated value• The liquid bulk temperature is under the saturated value

• The temperature of the cladding is at saturated value : nucleation

• Low heat flux between the hot and cold channels, in radial direction :quasi-adiabatic system

• The system is not able to reproduce a LOCA, with this configuration.

LORELEI : Next Steps

Further calculations should be performedCalculations with gas:

• To take into account, the radiative heat transfer and the gamma-heating in the structures

• To adapt the heat losses (changing the insulating shell), in order to stabilize the temperature at about 300 °C, with the test device in a back position

• To check that an increase of power on the fuel rod up to 20 - 40 W/cm will lead to the required heat-up rate (10 to 20 W/cm)

• To identify the power history in order to stabilise the temperature on the cladding up°to 1200 °C

• To take into account the steam-Zircaloy reaction and to analyse the experimental di i d (h i i i l id l h l )conditions and parameters (heat-up rate ; initial oxide layer ; heat losses ; …),

allowing the stabilization at 1200°C and preventing any escalation of the temperature evolution due to the chemical power

• To simulate the emptying of the device, with gas injection

Calculations with water

• To simulate the quenching of the device, with water

LORELEI

THANKS FOR THE ATTENTION

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