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IN-VEssel COrium Retention (INVECOR) in accident of water reactor


Experimental Study of the Processes at the Corium Melt Retention in the Reactor Pressure Vessel

Tech Area / Field

  • FIR-EXP/Experiments/Fission Reactors
  • FIR-NSS/Nuclear Safety and Safeguarding/Fission Reactors

8 Project completed

Registration date

Completion date

Senior Project Manager
Tocheny L V

Leading Institute
National Nuclear Center of the Republic of Kazakstan / Institute of Atomic Energy (2), Kazakstan, Kurchatov


  • IRSN - Institut de Radioprotection et de Sûreté Nucléaire, France, Fontenay aux Roses\nForschungszentrum Karlsruhe GmbH, Germany, Karlsruhe\nForschungszentrum Rossendorf, Germany, Rossendorf\nDIMNP - Pisa University, Italy, Pisa\nCEA / DEN, France, Gif-sur-Yvette Cedex

Project summary

Overall project objective – Improvement of the safety assessment of LWR corium in-vessel retention (IVR) under severe accident conditions.

Specific objective of the project is the experimental modeling of the thermal and physicochemical processes at the retention of the prototypical corium molten pool on the water-cooled lower head of the reactor pressure vessel (RPV).

The researches actuality is caused by necessity of confirmation of the concept of corium in-vessel retention in the projects series of nuclear power plants (NPP) with LWR in many countries, in particular VVER-440 (Loviisa NPP, Finland), VVER-640 (Russia), AP-600, AP-1000 (Westinghouse), BWR-1000 (Framatom), PWR-1400 (KEPÑO), NP300 (Technicatome).

Thermalhydraulic processes are rather completely investigated using melt simulators in R&D practice for IVR. Physicochemical processes in molten pool are investigated in RASPLAV and MASCA programs in small-scale experiments and in some large-scale experiences. Physicochemical processes of corium interaction with RPV steel are investigated in small-scale experiments only under ISTC METCOR project.

Complex of thermal and physicochemical processes at corium melt retention in large-scale RPV lower head model (LHM) is investigated in the Project.

LAVA-B facility of IAE NNC RK is used for the tests performance. This facility is equipped with the induction furnace for melt production (EMF) of the prototypical corium and with the discharged melt receiver (MR), which contained the water-cooled LHM, system of decay heat modeling in corium and the set of gauges for temperature, pressure and deformation measurement. Supporting experiments will be performed using the small-scale VCG-135 stand for preparation of large-scale tests and optimization of engineering and technological finding.

Performers of the Project have wide experience of the reactor severe accident processes with core melting experimental researches. Experiments on interaction of prototypic LWR corium with coolant (FCI) concrete (MCCI) and RPV steel (LHI and IVR-AM) were performed using the mentioned experimental facilities in cooperation with Japanese company NUPEC.

Involved inpidual experts from Aleksandrov's institute (NITI, Russia, Sosnovy bor) have wide experience on experimental MCCI and IVR research, processes at water supply on the corium melt surface and metals, on release of fission products from corium melt, on phase diagrams of corium.

The main results of the Project will be new experimental data on the corium pool final structure with natural convection at the decay heat modeling and RPV lower head ablation at various melt composition and thermal loadings on the RPV wall in 2-D configuration with real RPV lower head curvature.

The received results will be used for the models development, which are describing behavior of the melt at in-vessel phase of accident, verification of computer codes for the IVR concept validation for present and future NPP designs. The technological concepts used at experiments performance can be used by researchers for the similar problems solution.

It is provided in the Project performance of 4 tasks:

  1. Modernization of existing facilities and optimization of corium melting technology and modeling of decay heat in corium;
  2. Calculation support of the experiments, including pre-test calculations of EMF operating modes and operating modes of device for decay heat modeling and the post-test calculations using of computer codes of the NITI (Sosnovy bor, Russia) and ÑÅÀ (Cadarache, France);
  3. Large-scale experiments (3 tests);
  4. Post-test analysis of the experimental results, which includes investigation of corium – steel interaction, research of interaction products, INVECOR database formation.

The following forms of co-operation with foreign collaborators are realized in the Project:
  • Discussion and specification of the experiments matrix;
  • Participation of collaborators in pre-test and the post-test calculations, and also in processing of measurement results of the chemical composition of interaction products and formation of INVECOR database;
  • On-line exchange with obtained information during Project realization;
  • Reporting discussion;
  • Meetings and seminars organization;
  • Preparation of joint reports and articles.


The International Science and Technology Center (ISTC) is an intergovernmental organization connecting scientists from Kazakhstan, Armenia, Tajikistan, Kyrgyzstan, and Georgia with their peers and research organizations in the EU, Japan, Republic of Korea, Norway and the United States.


ISTC facilitates international science projects and assists the global scientific and business community to source and engage with CIS and Georgian institutes that develop or possess an excellence of scientific know-how.

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