ERMSAR 2012, Cologne March 21 – 23, 2012 CONDUCT AND ANALYTICAL SUPPORT TO AIR INGRESS EXPERIMENT QUENCH-16 J. BIRCHLEY 1, L. FERNANDEZ MOGUEL 1, C. BALS

ERMSAR 2012, Cologne March 21 – 23, 2012 1

CONDUCT AND ANALYTICAL SUPPORT TO AIR INGRESS EXPERIMENT QUENCH-16

J. BIRCHLEY1, L. FERNANDEZ MOGUEL1, C. BALS2, E. BEUZET3, Z. HOZER4, J. STUCKERT5

1) PSI, Villigen (CH) 2) GRS, Garching (DE) 3) EDF, Clamart (FR) 4) AEKI, Budapest

(HU) 5) KIT, Karlsruhe (DE)


Background and objectives

Planning analysis

Experiment conduct and outcome

Conclusions and outlook

Outline


Air ingress issues have come into prominence in recent years– post RPV failure, spent fuel

– several recent and ongoing programmes

separate effect and integral tests

model development

– QUENCH-16 extends database of air ingress bundle data

performed in frame of EU-supposed LACOMECO

proposed and defined by AEKI, Hungary

Objectives: examine reaction with air following mild pre-oxidation in steam and investigate reaction with both O2 and N2

– pre-oxidised layer 200 μm maximum

– long period of steam starvation

Stringent test objectives meant careful planning analyses needed

Background, objectives


QUENCH containment and test section QUENCH bundle cross section

QUENCH facility


Planning support performed by

– GRS (ATHLET-CD)

– EDF (MAAP4.07/EDF)

– PSI (SCDAPSim/MOD3.5 and MELCOR 1.8.6)

Strategy

– define a pre-oxidation transient at T = ca. 1500 K to give pre-oxidised layer 150-200 μm

– investigate different power levels and Ar, air flow rates to seek complete O2 consumption long before nominal limit temperature of 1823 K

Converged on a nominal test protocol supported by all simulations

– power: 10 kW for 5000 s then 4 kW to end

– flow rate (pre-ox): 3 g/s steam + 3 g/s Ar

– flow rate(air): 0.2 g/s air + 1 g/s Ar

– reflood: 50 g/s water when T,max = 1823 K

Planning analyses


All the codes used are lumped-parameter, system or sub-system level codes for transient analysis of nuclear plant accident sequences

– two-phase transient thermal hydraulics

– non-condensable species

– metallic oxidation and core degradation

All the codes have recently been (are being) improved – oxidation in steam and air using established correlations as baseline

– modifications to represent breakaway oxidation

– Zr + N2 reaction (ATHLET-CD)

Different levels of detail in treatment of thermal-hydraulics and other processes

Different levels of detail in noding

Key code features


GRS

Fuel rod temperatures showing effect of onset of O2 oxidation and local starvation

Progression of local complete O2 consumption; starvation period 920 s

starvation

starvation phase


EDF

Fuel rod temperatures at 250, 650, 950 and 1250 mm for 3 g/s (solid) and 1 g/s (dashed) Ar flow

Progression of local complete O2 consumption (1 g/s Ar); starvation period 1150 s

starvation phase


PSI SCDAPSim

Effect of air and Ar flow on oxygen consumption and period of starvation

Fuel rod temperatures showing effect of onset of O2 oxidation and local starvation starvation period1540 s

starvation phase


Comparison - 1

PartnerCode

PSI SCDAPSIM

PSI MELCOR1.8.6

GRS ATHLET-CD

EDF MAAP 4.07

Experiment

Heat-upPre-oxidationPowerAr + steamTmax (5000 s)

0-5000 s

10 kW3 g/s + 3 g/s

1440 K

0-5000 s

10 kW3 g/s + 3 g/s

1422 K

0-5000 s

10 kW3 g/s + 3 g/s

1440 K

0-5000 s

10 kW3 g/s + 3 g/s

1480 K

0 – 6300 s

10 – 11.5 kW3 + 3.3 g/s

1489 K

CooldownPowerAr + steamTmax (6000 s)

5000-6000 s4.0 kW

3 g/s + 3 g/s1061 K

5000-6000 s4.0 kW

3 g/s + 3 g/s1098 K

5000-6000 s4.0 kW

3 g/s + 3 g/s1090 K

5000-6000 s4.0 kW

3 g/s + 3 g/s1100 K

6300-7300 s4.0 kW

3 g/s + 3.3 g/s1067 K

Air phasePowerAr + air

6000 - 9260 s4.0 kW

1 g/s + 0.2 g/s

6000 - 8350 s4.0 kW

1 g/s + 0.2 g/s

6000 - 9420 s4.0 kW

1 g/s + 0.2 g/s

6000 - 8750 s4.0 kW

1 g/s + 0.2 g/s

7300 - 11135 s4.0 kW

1 g/s + 0.2 g/s


Summary of results

PartnerCode

PSI SCDAPSIM

PSI MELCOR1.8.6

GRS ATHLET-CD

EDF MAAP 4.07

Experiment

Quench(temp)Fast refill + 50 g/s waterPower

9260 s (1823 K)

4 kW

8350 s (1823 K)

4 kW

9420 s (1823 K)

0 kW

8750 s (1823 K)

0 kW

11335 s (1883 K)

4 kW

H2 mass,Max. oxide after preox

13 g

186 µm

15 g

190 µm

11 g

190 µm

19 g

242 µm

14 g

133 µm

Duration air phasestarvation

3260 s

1540 s

2350 s

1660 s

3420 s

920 s

2750 s

1150 s

4035 s

835 s

H2 mass (reflood)

2g 16 g 1 g 1 g 128 g

Remarks no influence of 0/4 kW during

quench

ZrN model would increase starvation time

Comparison - 2


Test conduct showing electric power input and selected temperatures

Off-gas mass composition showing O2, N2 consumption and H2, N2 release

QUENCH-16 conduct

O2 starvation

N2 consumption

release of H2 and N2 during reflood


Post-test videoscope inspection (front view) at elevation 550 mm, showing spalling of oxide scale

Post-test videoscope inspection (side view) at elevation 790 mm, showing nitride formation and partial spalling

Bundle examination - 1

rod #5

shroud


Bundle cross section at 430 mm: frozen melt relocated from upper elevations

Bundle cross section at 830 mm: minor melting of some cladding segments


oxide

metallic


Bundle elevation 350 mm, cladding of rod #5: nitrides between two oxide layers

Bundle elevation 550 mm, cladding of rod #9: nitrides between inner dense and outer porous oxide layers


porous ZrO2, probably containing reoxidised ZrN

denseZrO2


QUENCH-16 adds significantly to knowledge on air ingress transient behaviour

– complements previous experiments

– minor pre-oxidation and long O2 starvation period maximised influence of N2

– significant ZrN formation and re-oxidation

Coordinated pre-test planning analysis facilitated successful experiment

– pre-reflood quite well predicted but models did not capture the strong reflood excursion which included significant oxidation of both solid and molten material

– starvation, ZrN formation, or the two together might have been influential as a trigger

– code models are not yet able to represent these effects reliably

Post-test analyses are underway at several institutes

– benchmark on QUENCH-air is being performed within WP5.1/JPA3

– answer “do we need to model effects of starvation and ZrN on oxidation during reflood?”

– and we hope will point the way to how to do it

Conclusions, outlook


The LACOMECO programme is performed by KIT with financial support from the HGF Programme NUKLEAR and the European Commission. Technical support is provided by institutes with the European Economic Area

The development and validation of the code ATHLET-CD are sponsored by the German Federal Ministry of Economics and Technology (BMWi). PSI acknowledges financial support of ENSI, the Swiss nuclear regulatory organisation

Thank you for your attention

Acknowledgements

Documents

ERMSAR 2012, Cologne March 21 – 23, 2012 CONDUCT AND ANALYTICAL SUPPORT TO AIR INGRESS EXPERIMENT QUENCH-16 J. BIRCHLEY 1, L. FERNANDEZ MOGUEL 1, C. BALS