Overview of Containment Issues and Major Experimental ... · ERMSAR-2005 Session 3: CONTAINMENT TOPICS Overview of Containment Issues and Major Experimental Activities L. Meyer, H

ERMSAR-2005 Session 3: CONTAINMENT TOPICS

Overview of Containment Issues and Major Experimental Activities

L. Meyer, H. Wilkening, H. Jacobs, H. Paillere

The first European Review Meeting on Severe Accident Research (ERMSAR-2005)

Aix-en-Provence, France, 14-16 November 2005

2ERMSAR-2005 Session 3: CONTAINMENT TOPICS

Organization of the CONTAINMENT group(18 partner organisations)

WP12: Hydrogen Behaviour in Containment (HBC)WP 12-1: Hydrogen Combustion (HC)

WP 12-2: Containment Atmosphere Mixing (CAM)

WP13: Fast Interaction with Corium (FIC)WP 13-1: Fuel Coolant Interaction (FCI)

WP 13-2: Direct Containment Heating (DCH)


Organization of the CONTAINMENT group

WP12: Hydrogen Behaviour in Containment (HBC)WP 12-1: Hydrogen Combustion (HC)

PARTNER (7) FACILITY CODEIRSN (France) ENACCEF TONUSFZJ (Germany) REKO-3 REKO-DIREKTFZK (Germany) COM-3DGRS (Germany) COCOSYS-DECORJRC (EU) REACFLOWTUS (Bulgaria) ASTECVEIKI (Hungary) GASFLOW

*CFD-codes*Lumped parameter codes


Hydrogen Combustion

Topics of the EURSAFE PIRT addressed in WP 12-1: Hydrogen Combustion (HC)

Experimental Facility addressing the issue

Physical effect involved

REKO-3The use of recombiners might limit the explosion loads but could also cause ignition.

Hydrogen removal / mitigation

RUTScaling effects in hydrogen Combustion

Pressure loads

ENACCEFFlame Acceleration in non-uniform hydrogen/air/steam mixtures

Flame Propagation


Hydrogen Combustion

The ENACCEF test facility (Enceinte d’ACCElération de Flamme)

The upper dome part with a total volume of 0.66 m3

The lower driver tube with a length of 3.2 m and a diameter of 0.154 m


Hydrogen Combustion

ENACCEF test facility – experimental details

The ENACCEF test facility can be filled with any type of hydrogen-air-steam mixtures.

Within the acceleration tube obstacles can be installed to increase turbulent flame propagation/acceleration.

The facility is equipped with pressure transducers and photomultipliers.

The driver tube has also optical access to allow LDV and PIV measurements.


Hydrogen Combustion / Removal

From the recombiner via the experiment to the model

outlet

catalystsheetsinlet

Box-type recombiner REKO-3 REKO-DIREKT



REKO-3 test facility

inlet

recombinerunit

catalyst sheets

outletgas analysis


Hydrogen Combustion/Removal

REKO-3 - Measurements

INLET• flow rate• gas temperature• gas composition

OUTLET• gas temperature• gas composition CATALYST PLATE

• catalyst temperatureat 10 different locations

REACTION ZONE• gas compositionat 14 different locations

INLET PARAMETERS OF EXPERIMENTS- flow rate (0.25..0.80 m/s)- inlet temperature (ambient..150°C)- inlet hydrogen concentration

(0..5 vol.%, limited by safety concerns)- inlet steam concentration

(0..60 vol.%, depending on flow rate)- inlet oxygen concentration



REKO-3 experiments: transient measurements

0

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0 200 400 600T / °C

x/m

m

30 min

1 min 2 min 3 min 4 min

8 min

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143 x 143 mm²(1,5 mm sheets)

T = 25 °Cv = 0.5 m/s

yH2 = 4 vol.%

H2 + air



REKO-3 experiments: stationary behavior140

0 2 4 6

yH2,E/ Vol.-%2.0 4.0

T' = 25 °Cv' = 0.80 m/s

x/

mm

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20

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yH2,E/ Vol.-% 2.0 4.0

T' = 25 °Cv' = 0.80 m/s

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mm 80

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yH2 / vol.% T / °C


Hydrogen Combustion

Hydrogen explosion modeling with the CFD-code REACFLOW Advances in Grid Adaptation by Multiple Adaptation Variables

adaptation on the flame front(H2O concentration)

adaptation on the pressure wave ahead of the flame front


Hydrogen Combustion

Case 1: single point ignition

Case 2: symmetric double point ignition

Studying different ignition scenarios for hydrogen combustion in a reactor using CFX and REACFLOW

With two ignition points the overall burning rate might be larger but flame speeds (overpressure) can be reduced due to shorter flame acceleration distances/time.

TEMPERATURE at 0.5 s 0.68 s 0.98 s


Hydrogen Combustion

Investigating different venting scenarios using CFX and REACFLOW for a simplified nuclear reactor geometry

Modified venting could reduce quite drastically the pressure between neighboring rooms. Such different pressures could cause the collapse of the wall and trigger a sequence of events within the containment with potentially devastating effects.


Hydrogen Combustion

ASTECTwo combustion options are already available : COVI, COMB in CPA

PROCO module is being implemented into CPA:

• All combustion modes from laminar deflagration to stable detonation are

covered

• Two criteria to decide about Deflagration-to-Detonation Transition:

- Mach number of precursor shock > 1.5 (composition dependent)

- Characteristic length of compartment > 7 times the detonation cell size λ (geometry and composition dependent)



WP12: Hydrogen Behaviour in Containment (HBC)WP 12-2: Containment Atmosphere Mixing (CAM)

PARTNER (12) FACILITY CODEIRSN (France) TOSQAN TONUS, ASTECCEA (France) MISTRA TONUSDIMNP (Italy) CONAN FLUENT, FUMO, MELCORFZK (Germany) GASFLOWGRS (Germany) COCOSYSJSI (Slovenia) CFX-4, CONTAIN, MELCORKTH (Sweden) CFX-4/5LEI (Lithuania) COCOSYS, ASTEC, CONTAINNRG (Netherlands) CFX-4/5, STAR-CD, SPECTRA, MAAPRUB-LEE(Germany) COCOSYSUPM (Spain) CFX-4, MELCORVEIKI (Hungary) GASFLOW, COCOSYS


Containment Atmosphere Mixing

On-going R&D topics are related to identified gaps related to the formation of combustible gas mixtures in the containment, as identified in the EURSAFE PIRT or in recent benchmark exercises such as ISP-47:

Condensation modelling in CFD codes(UNIPI task leader)

- concerning diffusive models (wall function) or correlations (heat & mass transfer)

• review or in-depth analysis of past experiments (TOSQAN and MISTRA tests made available to SARNET)

• deficiencies, identification of validation needs

• recommendations on choice of models & best practice guidelines

• recommendations for new experiments (CONAN, MISTRA)

CONAN (UNIPI)

MISTRA (CEA)

Injection region (Zone 1) acceleration/decceleration and gas entrainment by the plume/jetInjection pipe

Non condensing wall

Condensing wall

Thermal free convection zone (Zone 4)thermally induced flow

Recirculation zone (Zone 2) recirculated flow induced by the jet

TOSQAN (IRSN)



TOSQAN (IRSN)


Spray modelling (IRSN task leader)

• Organisation of a benchmark Experiments performed by IRSN (TOSQAN) and CEA (MISTRA) are being provided as basis for benchmarking of LP and CFD codes – possibility to look at scaling effect: TOSQAN (7m3) MISTRA (100m3)

Effect of spray mitigation system on H2 distribution (risk):

- homogenization?- local H2 enrichment by steam condensation?

MISTRA (CEA)




Interaction PAR – atmosphere (CEA task leader)

• Organisation of a (numerical) benchmark on

interaction of Passive Autocatalytic Recombiners with containment atmosphere- issues of modelling (CFD) of thermal plume (burned gases)

- natural convection effects

- effect of positioning of recombiners in a room on global efficiency



WP13: Fast Interaction with Corium (FIC)WP 13-1: Fuel Coolant Interaction (FCI)

PARTNER (7) FACILITY CODEIRSN (France) TREPAM MC3DCEA (France) KROTOS MC3DFZK (Germany) ECO MATTINAIKE (Germany) DROPS IKEMIX, IDEMOJSI (Slovenia) ESE-2KTH (Sweden) MISTEE COMETA-KTHTUS (Bulgaria)

*CFD-codes


Fuel-Coolant Interaction (FCI)

WP 13-1: Fuel-Coolant Interaction (FCI)

EURSAFE selected: FCI including steam explosion,in-vessel and ex-vessel.

Aim: - Increase knowledge about steam explosion energetics.- Develop tools to determine the risk of vessel or containment failure.

OECD Research program SERENA:- Aim: Evaluate capabilities of available codes with respect to

reactor applications.- Participants from SARNET: IRSN, CEA, FZK, IKE


Experiment ECO (FZK):Measurement of Energy Conversion(mechanical energy release)Closed system of piston and cylinder15…18 kg of Al2O3 (in 4 tests)External trigger applied

• With full water mass, no explosion. • With restricted water mass (tube),

3 strong explosions.• Pressures well beyond 100 MPa.• Still quite low (and varying) energy

conversion: 2.4, 0.8 and 0.6 %.• Possible reasons for low conversion:

- high water subcooling (-> factor 2) - overstrong confinement

(piston mass = 2700 kg)• Facility mothballed




Experiment KROTOS-Cadarache (CEA):

Study the effect of material properties on steam explosions.

Up to 5 kg corium of variable composition or 4 kg of SS (or 1.5 kg Al2O3).

External trigger applied.

Improvements with respect toKROTOS-Ispra:- reproducible melt release with slide valve;

- high-speed X-ray radioscopyto observe premixture.

To go in operation end of 2005.



WP13: Fast Interaction with Corium (FIC)WP 13-2: Direct Containment Heating (DCH)

PARTNER (7) FACILITY CODEIRSN (France) MC3D, RUPUICUV (ASTEC)EDF (France) MAAP-4FZK (Germany) DISCO-H/C AFDM, SIMMERGRS (Germany) CONTAIN, COCOSYSRUB-LEE (Germany)TUS (Bulgaria) ASTECFRA ANP (Germany)

*CFD-codes*Lumped parameter codes


Direct Containment Heating (DCH)

HEAT TRANSFER CORIUM – STEAM / GAS

CONTAINMENT PRESSURIZATION

relocated corium

dispersed corium

steam blowdown

corium jet impact / fragmentation

+

breach in the lower head

H2 - COMBUSTION

metal oxidation and hydrogen production

trapped corium

corium film formation and entrainment

Phenomena occurring during DCH



PAST RESEARCH PROGRAMS (-1998)

Achievements • Large database on US reactor type plants.• Several analytical models were developed.• Simple models were integrated into codes

(MAAP, CONTAIN, MELCOR).

Main conclusions • Up to 70% dispersion out of pit• Containment integrity maintained• No scaling effect for pressure• Strong effect of geometry

Issue was closed for US plants



EURSAFE PIRT selected phenomena as most important:• corium entrainment out of reactor vessel with lateral breaches• corium oxidation coupled with hydrogen production• generating and trapping of particles• particle heat exchange• hydrogen combustion

Ø5092mm

4200 mm

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4400 mm

800 mm

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GA 301

German KONVOI (similar to EPR) French 1300 MWe VVER-1000


Nozzle

Annular gapRPV support

1620

mm

RPV+RCS Volume

Filter

Gas Line

Steam Generator

Room

Pump Room

Rupture DiskMelt Simulant

Cavity

Test Facility DISCO-C (FZK)(EPR scale 1:18, P’4 scale 1:16)

Cold tests for fluid dynamic investigations

Simulant Melt: Water and liquid metal alloys Driving gas: Nitrogen and HeliumFailures Modes: Central and lateral breachesBurst pressure: 0.3 – 1.6 MPa

Central holes: Strong influence of initial gas pressure and hole size:

- The maximum dispersion (75%) is reached at pressures below 2 MPa

- Pressure < 0.5 MPa limits dispersion to <10% Lateral breaches and total circumferential breakaway of lower head lead to less dispersion than central holes



Test Facility DISCO-HH (FZK)(EPR scale 1:18, P’4 scale 1:16)

Hot tests including all processes, close to prototypical conditions:

Simulant Melt: Iron-alumina melt (2400 K)Driving gas: Steam or NitrogenFailures Modes: central breaches (3 sizes)Pressure at failure: 0.7 – 2.2 MPA

Containment atmosphere: Air + steam + H2 or N2

With or w/t direct flow path from pit to containment

Data available to SARNET partners from:6 Tests in EPR geometry1 Test in P’4 geometry (LACOMERA-1)1 Test in VVER-1000 geometry (LACOMERA-2)



Test Facility DISCO-HH (FZK)(EPR scale 1:18, P’4 scale 1:16)

• Without hydrogen combustion pressure rise in containment is low.

• Pre-existing hydrogen content in containment can be important for pressure rise.

• Without direct flow path from pit to containment less hydrogen is burned and pressure rise is low.

• With small breaches the mixing and combustion of produced hydrogen with the containment atmosphere is too slow to contribute to peak pressure.

Investigations are necessary for each specific reactor design.



Thank you for your attention

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Overview of Containment Issues and Major Experimental ... · ERMSAR-2005 Session 3: CONTAINMENT TOPICS Overview of Containment Issues and Major Experimental Activities L. Meyer, H