Long-term Behavior of Corium after Accident
Long-term Behavior of Corium after Accident (Using the Data of the Chernobyl NPP Accident)
Tech Area / Field
- FIR-DEC/Decommissioning/Fission Reactors
3 Approved without Funding
Kurchatov Research Center, Russia, Moscow
- Gesellschaft für Anlagen und Reaktorsicherheit mbH, Germany, Köln\nAtomic Energy Canada Limited, Canada, ON, Chalk River\nEuropean Commission / Joint Research Center / Institute for Transuranium Elements, Germany, Karlsruhe
Project summaryAt present RRC “Kurchatov Institute” jointly with the Nuclear Safety Institute of the Russian Academy of Sciences (IBRAE RAS) are implementing the ISTC Project #2916 “CHESS” “Development of the Models for Nuclear Fuel Behavior during Active Phase of Chernobyl Accident”.
The project is aimed at systematizing a huge body of data on lava-like fuel-containing materials collected over 20 years of investigations at the “Shelter”, generating a database on their basis and developing models of the processes of lava generation and spreading during the early post-accident days.
After spreading, 1200 t of “lava” inside the “Shelter” have been during 20 years under the impact of external (humidity, temperature) and internal (its own radioactive emanation) factors and have degraded gradually.
As intended presently, many more decades will pass prior to removal of “lava” out of the new confinement and its ultimate disposal.
Thus at the following phase one should develop and justify models of “lava” behavior and degradation over a protracted period of time (up to its removal 100 years) - this is the content of the present proposal for a new ISTC Project “CHESS – 2”.
Based on the models developed, recommendations on optimum establishment of barriers to prevent nuclear and radiation hazard at the Chernobyl NPP during “lava” storage and removal may be proposed.
The development of such-type models is of interest for the whole category of hypothetical accidents accompanied with corium generation.
Just as in case of Chernobyl, works on corium removal and disposal might begin not immediately after an accident and thus would require a protracted period of time. In such a case the model might be useful for the development of corium retention devices for PWR, BWR and VVER power projects.
The Project “CHESS-2” shall answer a series of specific questions.
After the end of the active accident phase 20 years have elapsed. What processes have occurred with the “lava” during the period indicated? What processes will take place in the future during the time of awaiting removal of “lava” for several more decades under new-confinement conditions?
What physical and chemical processes and what external and internal mechanisms may have effect on “lava” degradation? What is the role of self-irradiation?
Whether or not “lava” will transform into fine fuel dust over the period in question? Whether or not soluble uranium compounds will be generated on its basis; and what will be the radiation hazard in the course of removal?
What countermeasures may be taken in case of hazard, and what safety barriers may be recommended for use under the “Shelter” conditions?
What general recommendations on safe protracted storage of corium may be proposed?
The interfaces between the Projects “CHESS” and “CHESS-2” and their main objectives are demonstrated in the below diagram.
The use of the “CHESS” Project database in “CHESS–2” Project is intended.
In addition, the database will be substantially supplemented with new sections addressing possible radiation and chemical causes of lava degradation.
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