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Study on Bundle Degradation and Molten Pool Formation in the PHEBUS FP Experiments

Funded under: FP6-JRC


The new model for simultaneous melt oxidation and fuel dissolution under non-equilibrium conditions characterised by temperature difference between solid and liquid phases [1] is further developed: the applicability range of the new model is extended to higher temperatures (exceeding 2530 K), and a new, more adequate consideration of the representative fuel rod surrounded by a molten pool is introduced.
A qualitative analysis of the post-test appearance and chemical composition of the molten pool in the Phebus FPT0 and FPT1 tests is performed, and a close analogy with the recent QUENCH-09 test observations is revealed. This analysis confirms the main qualitative conclusion of the new model that the observed ceramic corium was formed at temperatures essentially lower than the melting point of the ceramic material, in the course of metallic melt relocation, oxidation and chemical interactions.
The new model is implemented in the SVECHA/QUENCH code and applied to analysis of the molten pool evolution in the late stage of the Phebus FPT0 and FPT1 tests, using temperature scenarios of these tests from available experimental data. It is shown that the observed homogeneous corium microstructure can be explained by precipitation of mixed ceramic (U,Zr)O2-x phase which accompanies the enhanced dissolution of fuel rods by (over)saturated melt and growth of the peripheral oxide crust with a similar to central corium composition.

Additional information

Authors: VESHCHUNOV M S, Russian Academy of Sciences, Nuclear Safety Institute, Moscow (RU);BOLDYREV A V, Russian Academy of Sciences, Nuclear Safety Institute, Moscow (RU);MÜLLER K, Russian Academy of Sciences, Nuclear Safety Institute, Moscow (RU)
Bibliographic Reference: EUR 21499 EN (2005), 69 pp. Free of charge
Availability: Available from European Commission, JRC Knowledge Management Unit, Ispra (IT) Tel: +39 033278 9893 Fax: +39 033278 5409 E-mail: or Bruxelles (BE) Tel: +32 2 295 76 24 Fax: +32 2 299 63 22
Record Number: 200718958 / Last updated on: 2007-03-16
Original language: en
Available languages: en
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