The investigations in the field of NPP sever accidents have becme more relevant after the Chernobyl NPP accident of 1986 with reactor destruction, core meltdown and corium release beyond the safety barriers. To prevent that kind of accidents, a large amount of work on severe accidents research was performed in FSUE «Alexandrov NITI» with due account for defense-in-depth principle. Within the shortest time period the unique RASPLAV experimental platform was created to carry out experimental research using the prototype core-melt under simulated severe accident conditions. The operation of the RASPLAV experimental platform is based on induction melting and long-time retention of chemically aggressive high-temperature melts (similar to corium) in a cold crucible.
The main line of research activities include:
- experimental research and numerical calculation of corium interaction with structural and functional materials of nuclear power installations and NPPs;
- development and investigation of materials and technologies for NPP safety enhancement;
- preparation of prototype specimens from high-temperature materials (including prototype corium) by induction melting in a cold crucible for customers.
The RASPLAV experimental platform is used to carry out the works that consider substantially all aspects of severe accidents and contribute to discovering of new phenomena and to deep understanding of severe accident processes. Proprietary computer models and codes are used for verification of obtained experimental results.
Research and development works are performed jointly with well-known research and educational establishments, such as ETU «LETI», SPSIT, I.V. Grebenshchikov Institute of Silicate Chemistry, Ioffe Institute, V.G. Khlopin Radium Institute, JSC Atomproekt, and IBRAE to the order of national and international organizations.
| Parameters | |
| Melt retention method | Induction melting in a cold crucible |
| Installations | RASPLAV-2, RASPLAV-2s, RASPLAV-3, RASPLAV-4, RASPLAV-5 |
| Installed power, kW | 25 to 260 |
| Heating current frequency, MHz | 0.01 to 5.28 |
| Weight of melt in a crucible | 0.1 to 10 |
| Melt temperature, °С | up to 3000 |
| The atmosphere above the melt | Ar, N2, He, Ar/H2, air, steam and their mixtures |
| Melt composition | oxide (including high-resistivity melts), metal, carbide, nitride and mixed systems including U containing prototype melts with corium properties |
| Possible ways of melt treatment | Quenching, cooling at a specified rate, vertical movement of a crucible relative to inductor, melt discharge |
The obtained data are widely accepted in and outside of Russia and used by world’s research centers for safety justification of existing NPPs and those under design.
The core catcher design developed and justified by NITI was approved by national and international supervisory authorities. The world’s first core catcher was installed at Tianwan NPP with VVER-1000 reactors. Nowadays the core catcher at NPP is one of the key factors in assessment of NPP design competitiveness.
«Corium crystallization in UO2-SiO2 system»
«Corium discharge onto steel basement»
«Water supply onto oxide corium surface»
«Interaction of sacrificial material with corium»
Thirty-year experience in experimental study of high-temperature processes allows FSUE “Alexandrov NITI” to complete the following tasks:
- study of high-temperature processes and materials resistance at extreme high temperature and thermal gradients;
- development of new materials meeting the advanced nuclear requirements;
- development of new technologies for NPP safety enhancement.