Containment thermal-hydraulics of current and future LWRs for severe
accident management
EU 7.FWP ERCOSAM and ROSATOM Project SAMARA
The presence of a stratification in a NPP containment is
a source of concern, as pockets of hydrogen in high concentration could lead to
a deflagration or detonation risk, which might challenge several equipment
necessary for safety functions and even the containment structural integrity.
The objectives of the project are two folds: one is to establish whether in a
test sequence representative of a severe accident in a LWR, well chosen from
existing plant calculations, a hydrogen (helium) stratification can be
established during part of the transient starting from the initiation of the
loss of coolant accident (LOCA) blowdown until the end of bulk hydrogen release
from the reactor vessel into the containment, and the second is how this
stratification can be broken down by the operation of Severe Accident Management
systems (SAMs); sprays, coolers and Passive Auto-catalytic Recombiners (PARs).
Experiments will be performed at “small scale” TOSQAN (IRSN, Saclay),
"medium scale" in the MISTRA (CEA, Saclay) and PANDA (PSI, Villigen)
facilities and at "nearly prototypical scale" in the KMS (NITI,
Tests without mitigation systems (spray, containment
cooler or heat source simulating the behaviour of a hydrogen recombiner) and
with those systems active will be performed, to assess their efficiency in
breaking up the stratification and promoting homogenization of the atmosphere.
Although
to be coupled at the technical and administrative levels, the research will be
conducted by two consortiums in two parallel running projects; ERCOSAM, which
is to be partially funded by Euratom and SAMARA which is to be funded by
ROSATOM. One consortium is composed of Paul Scherrer Institut (PSI)
(Switzerland), Institute for Radiological
Protection and Nuclear Safety (IRSN) and Commissariat à l’Energie Atomique et aux
Energies Alternatives (CEA) (France),
Karlsruhe Institute of Technology (KIT), former Forschungszentrum Karlsruhe GmbH (FzK)
(Germany), Nuclear Research & Consultancy Group v.o.f. (NRG) (The
Netherlands) from countries in the West Europe and Atomic Energy Canada Limited
(AECL) (Canada) and the second by the Russian organizations: Nuclear Safety Institute of the Russian Academy of
Sciences (IBRAE RAN) and State Research Center of Russian Federation
– Institute for Physics and Power Engineering (SSC RF-IPPE). These two strongly interlinked and coordinated research
projects, ERCOSAM and SAMARA, will foster cooperation and provide means to
reach a common safety goal.
Both
individual projects will be technically coupled under a project name
ERCOSAM-SAMARA and in short ‘ERCO-SAMA’.
|
Participant
no. |
Participant
organisation full and short names |
Country |
|
1. (coordinator) |
Paul Scherrer
Institut, PSI |
|
|
2. |
Institute for Radiological Protection
and Nuclear Safety, IRSN |
|
|
3. |
Commissariat à
l’Energie Atomique et aux Energies Alternatives, CEA |
|
|
4. |
Karlsruhe Institute of Technology, KIT |
|
|
5. |
Nuclear
Research & Consultancy Group v.o.f., NRG |
The |
|
6. |
Atomic
Energy Canada Limited, AECL |
|
|
7. |
Nuclear Safety Institute of the |
The |
|
8. |
|
The |
|
New comers in 2011 |
||
|
9. |
|
|
|
10. |
Afrikantov OKBM |
The |
This research project as a whole will
establish integrated research and the aim is to reduce the remaining
uncertainties in the area of containment thermal-hydraulics regarding current
and future LWRs for severe accident management in European countries and
The proposed project offers the creation of
high quality database needed for investigating:
Effect of Complexity of the Geometry: Effect of a) different size of test
vessels with one or more inner compartments, b) different interconnecting
geometry between compartments, c) different injection locations, and d)
different location of Spray nozzles, coolers and PAR models, and e) differences
in the type of coolers on the steam and non-condensable gases distribution in
the containment compartments;.
Complex Thermal-Hydraulic Phenomena: a) bulk and wall condensation, b) natural
and forced convective flows due to the low and high momentum vertical jets, c)
convective flows generated by spray droplets, d) buoyancy driven mixing of
light gas, and e) inter-compartmental gas transport.
The proposed project will serve:
Generation of High Quality Database Prototypical to Accident
Evolution: The
relative importance of individual phenomena on the natural evolution of the
steam and noncondensable gas distribution during idealized four phases of an
accident transient: a) the blowdown phase of a LOCA when only steam will be
injected into air filled containment; b) the injection of two-components
mixture (helium and steam) into existing two component (air-steam) atmosphere
during the core degrading phase of the severe accident; c) redistribution of
hydrogen by buoyancy driven mixing of accumulated hydrogen (if occurs) until
the time when severe accident management (SAM) devices start operating, and d)
the last phase during which convective flows created by the SAM devices (spray,
cooler and PAR[1] operation) interact with
hydrogen.
Demonstration of the Effectiveness of Mitigation Systems: Effects of convective flows
created by the active and passive mitigation systems, such as cooler, spray
system and recombiners on promoting destabilization of hydrogen pockets;
interactions of such hydrogen pockets with two convective flows created by
simultaneous operation of several similar or different mitigation systems such
as two recombiner units. Determination of time durations for the optimal
operation of sprays and coolers during which these systems might be promoting
the destabilization, beyond which adverse effects become more important due to
the efficient steam condensation and increase in the relative hydrogen
concentration.
Demonstration of Further Possibilities for Severe Accident
Management (SAM) Measures for Mitigating Hydrogen Risk: PARs, igniters, inertization and
containment venting are the established measures generally in use in a large
number of current LWRs. Use of PARs as the main SAM is generally foreseen in
the advanced reactors under construction. Many large dry containment designs
are equipped with containment sprays. Mainly all the containment designs are
equipped with fan coolers. The use of sprays and coolers (without the fan
operation) could potentially expand the SAM possibilities using the existing
hardware, however, the effectiveness and operational limits should be known.
The latter constitutes the two thirds of the proposed area of investigations.
Demonstration
of Predictive Capability of State of Art Analytical Tools: Lumped Parameter (LP) codes, in-house and
commercial Computational Fluid Dynamic (CFD) codes of the organizations in EU,
Switzerland and Canada and the Russian Federation will be used for the pre- and
post-test calculations and scenario analyses with the aim of validating the
containment codes as reliable predictive tools, able to be applied to reactor
cases. A synthesis report to be produced will integrate the outcome of test
results from the facilities as well as the code analysis and point out to
strengths and deficiencies in the predictive capabilities of the tools.
Generation of best practice: The proposed integrated research program
will facilitate a common shared platform to develop best practice at the European
level (scaling parameters, test procedure, documentation, instrumentation
accuracy, test repeatability, etc.) for performing experiments.
Optimized use of International resources: The proposed project further
offers fostering optimized use of the resource in Europe,
[1] Since the tests will use helium as the hydrogen simulant, the ‘Recombiner’ unit will be a simulator of a real recombiner by creating a plume at specified temperature and flow rate.