ISSN オンライン: 2688-7231
ISBN 印刷: 978-1-56700-497-7 (Flash Drive)
ISBN オンライン: 978-1-56700-496-0
Proceedings of the 25th National and 3rd International ISHMT-ASTFE Heat and Mass Transfer Conference (IHMTC-2019)
Modelling and Verifications of Fast Reactor Fuel Melting and Multi-phase Flow Code MITRA
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.