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ISSN Online: 2688-7231

ISBN Flash Drive: 978-1-56700-497-7

ISBN Online: 978-1-56700-496-0

Proceedings of the 25th National and 3rd International ISHMT-ASTFE Heat and Mass Transfer Conference (IHMTC-2019)
December, 28-31, 2019, IIT Roorkee, Roorkee, India

Modelling and Verifications of Fast Reactor Fuel Melting and Multi-phase Flow Code MITRA

Get access (open in a dialog) DOI: 10.1615/IHMTC-2019.1000
pages 593-598

摘要

Fast reactor fuel is generally designed in the form of cylindrical pellets of solid or annular variety. The annular variety provides advantages in terms of higher achievable energy extraction and lower fuel-clad mechanical interaction. Another advantage of this variety is the hydrodynamic flow of molten fuel inside the pellet during a severe accident. Classified as in-pin fuel motion, this flow can disperse the melt away from the core axial centre, thus mitigating the accident. This is of greatest significance during an unprotected transient overpower accident (hereafter UTOPA), wherein melting begins at the inner surface of the annular fuel pellets. The physics of the flow, however, is highly involved. Before accepting this phenomenon as a reliable safety feature, intricate theoretical modelling and sound experimental verifications are necessary. To predict precisely the molten fuel behaviour, a Multi-phase In-pin Thermal hydraulic Relocation Algorithm (MITRA) was developed. In this article, an outline of MITRA code and the results of verifications with experiments are presented. Results show that in-pin fuel motion does not change significantly with fuel burnup. Molten fuel continually occupies the core axial centre and does not disperse away. This is due to the lower gas retention in the inner regions of the fuel pellet. The resultant neutronic impact is negligible in fresh fuel and small in burnt fuel, if melt thermal expansion is neglected.