Conference Proceedings Paper
Analysis of Phenix Core Response to Inlet Sodium Temperature Increase During One of the EOL Tests
NURETH-14 - 2011 September 25-30
Aurelia Chenu (PSI, EPFL)
Konstantin Mikityuk (Paul Scherrer Institut)
Robert Adams (PSI, ETHZ)
Rakesh Chawla (PSI, EPFL)
This work presents the analysis, using the TRACE code, of the Phénix core response to an
inlet sodium temperature increase. The considered experiment was performed in the frame of
the Phénix End-Of-Life (EOL) test program of the CEA, prior to the final shutdown of the
reactor. It corresponds to a transient following a 40°C increase of the core inlet temperature,
which leads to a power decrease of 60%. This work focuses on the first phase of the transient,
prior to the reactor scram and pump trip.
First, the thermal-hydraulic TRACE model of the core developed for the present analysis is
described. The kinetic parameters and feedback coefficients for the point kinetic model were
first derived from a 3D static neutronic ERANOS model developed in a former study. The
calculated kinetic parameters were then optimized, before use, on the basis of the
experimental reactivity in order to minimize the error on the power calculation. The different
reactivity feedbacks taken into account include various expansion mechanisms that have been
specifically implemented in TRACE for analysis of fast-neutron spectrum systems. The point
kinetic model has been used to study the sensitivity of the core response to the different
The comparison of the calculated results with the experimental data reveals the need to
accurately calculate the reactivity feedback coefficients. This is because the reactor response is
very sensitive to small reactivity changes. This study has enabled us to study the sensitivity of
the power change to the different reactivity feedbacks and define the most important
parameters. As such, it furthers the validation of the FAST code system, which is being used
to gain a more in-depth understanding of SFR core behavior during accidental transients.
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