CONDUCT AND ANALYTICAL SUPPORT TO AIR INGRESS EXPERIMENT QUENCH-16

Transcription

1 CONDUCT AND ANALYTICAL SUPPORT TO AIR INGRESS EXPERIMENT QUENCH-16 J. BIRCHLEY 1, L. FERNANDEZ MOGUEL 1, C. BALS 2, E. BEUZET 3, Z. HOZER 4, J. STUCKERT 5 1) PSI, Villigen (CH) 2) GRS, Garching (DE) 3) EDF, Clamart (FR) 4) AEKI, Budapest (HU) 5) KIT, Karlsruhe (DE)

2 Outline Background and objectives Planning analysis Experiment conduct and outcome Conclusions and outlook

3 Background, objectives 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 O 2 and N 2 pre-oxidised layer 200 μm maximum long period of steam starvation Stringent test objectives meant careful planning analyses needed

4 QUENCH facility QUENCH containment and test section QUENCH bundle cross section

5 Planning analyses 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 K to give pre-oxidised layer μm investigate different power levels and Ar, air flow rates to seek complete O 2 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

6 Key code features 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 + N 2 reaction (ATHLET-CD) Different levels of detail in treatment of thermal-hydraulics and other processes Different levels of detail in noding

7 GRS starvation starvation phase Fuel rod temperatures showing effect of onset of O 2 oxidation and local starvation Progression of local complete O 2 consumption; starvation period 920 s

8 EDF 4.50E E- 0 5 O2 f l ow r a t e s ( k g/ s) 3.50E E E E E E E- 0 6 Ti me ( s) E mm mm mm mm mm mm 950 mm 1250 mm starvation phase 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 O 2 consumption (1 g/s Ar); starvation period 1150 s

9 PSI SCDAPSim starvation phase Effect of air and Ar flow on oxygen consumption and period of starvation Fuel rod temperatures showing effect of onset of O 2 oxidation and local starvation starvation period1540 s

10 Comparison - 1 Partner Code PSI SCDAPSIM PSI MELCOR1.8.6 GRS ATHLET-CD EDF MAAP 4.07 Experiment Heat-up Pre-oxidation Power Ar + steam Tmax (5000 s) s 10 kw 3 g/s + 3 g/s 1440 K s 10 kw 3 g/s + 3 g/s 1422 K s 10 kw 3 g/s + 3 g/s 1440 K s 10 kw 3 g/s + 3 g/s 1480 K s kw g/s 1489 K Cooldown Power Ar + steam Tmax (6000 s) s 3 g/s + 3 g/s 1061 K s 3 g/s + 3 g/s 1098 K s 3 g/s + 3 g/s 1090 K s 3 g/s + 3 g/s 1100 K s 3 g/s g/s 1067 K Air phase Power Ar + air s 1 g/s g/s s 1 g/s g/s s 1 g/s g/s s 1 g/s g/s s 1 g/s g/s

11 Summary Comparison of results - 2 Partner Code PSI SCDAPSIM PSI MELCOR1.8.6 GRS ATHLET-CD EDF MAAP 4.07 Experiment Quench(temp) Fast refill + 50 g/s water Power H2 mass, Max. oxide after preox Duration air phase starvation H2 mass (reflood) Remarks 9260 s (1823 K) 4 kw 13 g 186 µm 3260 s 1540 s 8350 s (1823 K) 4 kw 15 g 190 µm 2350 s 1660 s 9420 s (1823 K) 0 kw 11 g 190 µm 3420 s 920 s 8750 s (1823 K) 0 kw 19 g 242 µm 2750 s 1150 s s (1883 K) 4 kw 14 g 133 µm 4035 s 835 s 2g 16 g 1 g 1 g 128 g no influence of 0/4 kw during quench ZrN model would increase starvation time

12 QUENCH-16 conduct release of H 2 and N 2 during reflood N2 consumption O2 starvation Test conduct showing electric power input and selected temperatures Off-gas mass composition showing O 2, N 2 consumption and H 2, N 2 release

13 Bundle examination - 1 shroud rod #5 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

14 Bundle examination - 2 oxide metallic Bundle cross section at 430 mm: frozen melt relocated from upper elevations Bundle cross section at 830 mm: minor melting of some cladding segments

15 Bundle examination - 3 porous ZrO 2, probably containing reoxidised ZrN dense ZrO 2 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

16 Conclusions, outlook QUENCH-16 adds significantly to knowledge on air ingress transient behaviour complements previous experiments minor pre-oxidation and long O 2 starvation period maximised influence of N 2 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

17 Acknowledgements 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