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Corium Interaction with Reactor Vessel

#0833


Investigation of Corium Melt Interaction with NPP Reactor Vessel Steel (Metcor)

Tech Area / Field

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

Status
8 Project completed

Registration date
30.12.1996

Completion date
27.09.2001

Senior Project Manager
Tocheny L V

Leading Institute
Research Institute of Technology, Russia, Leningrad reg., Sosnovy Bor

Collaborators

  • University of California / Department of Chemical and Mechanical and Environmental Engineering, USA, CA, Santa Barbara\nEuropean Commission / Joint Research Center / Institute for Transuranium Elements, Germany, Karlsruhe\nForschungszentrum Karlsruhe Technik und Umwelt / Institut für Neutronenphysik und Reaktortechnik, Germany, Karlsruhe\nIVO Power Engineering Ltd., Finland, Vantaa

Project summary

The major goal of the proposed project is NPP reactor safety upgrading in conditions of a severe accident-causing core melting. Its subject matter is profound investigation of uranium-bearing corium melt and reactor vessel steel interaction with and without external vessel cooling.

Corium - vessel interaction evaluation analyses currently made by a number of organizations and countries consider only thermohydraulic processes in the melt pool. This approach has a disadvantage of neglecting physicochemical processes taking place at the corium melt - vessel steel interaction. Under the above-mentioned conditions physicochemical interaction processes can have a considerable influence due to the high chemical activity of the uranium-bearing corium melt.

The immediate project task is the corium melt - vessel steel interaction quantitative characterization taking into account both hydrodynamic and physicochemical processes.

The experimental tests are to be carried out in the RASPLAV-2 installation, which has been successfully operated for 6 years. At present it is used for the final tests on ISTC project No 064-094 " NPP Reactor Core Catcher Designed on the Basis of ZrO2 Concrete".

To obtain uranium-bearing corium melt an original methodology of induction melting in a crucible (IMC) is used in RASPLAV-2. The presence of solid phase (lining crust) between the melt and the crucible enables to reach a high melt superheating; to conduct tests in both inert atmosphere and in air; to have long duration experiments as well as a number of other advantages.

The project shall result in determining quantitative characteristics of the corium melt - vessel steel interaction depending on:


- corium melt composition and extent of its superheating;
- steel specimen external cooling conditions;
- above melt atmosphere (inert, air);
- steel specimen position in the corium melt: horizontally above, vertically, including formation of three media 'melt-steel- atmosphere' boundary.

To investigate the physicochemical interaction processes after the experiments, the specimen X-ray fluorescence and X-ray analyses are made in the interaction area as well as the material micro- and macrostructure study by the scanning electron microscopy and metallo- and ceramography methodologies.

The additional project tasks are:


1. Determining the composition and quantitative characteristics of interaction gases and aerosols.
2. Identification of post-interaction steel structure and its strength parameters.
3. Verification of computer codes modeling thermohydrodynamic and physicochemical processes in the melt pool during its interaction with the vessel steel.
4. Assessment of WWER-640 vessel temperature and stress-strain state using verified computer code.

The project investigation results will be primarily used for the new generation reactor WWER-640 safety upgrading. With that, the planned experimental results will probably find a broader application, for example for safety feasibility analysis of other Russian and foreign NPPs.

That is why possible project participants and supporters could be the companies designing and operating NPP reactors, like Westinghaus, General Electric, Siemens, Fromatom, IVO International and others. At the prospective partner wish the inventory of investigated steels and corium compositions could be modified.

The proposed project is developed with the participation of research and technical staff involved into defense industry programs, so it can be considered as subject to ISTC support both by its topic and goal. The total amount of work is estimated as 870 person-months in labor input and as 684 000 USD in costs including equipment acquisition.


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