The evaluation of nuclear fuel performance during potential accident scenarios is an integral part of the qualification for its use in present and future reactors. Among these scenarios the unprotected excursion of the reactor power is among the most limiting ones. An experimental test for fast reactor (MYRRHA) fuel will be performed within a European framework, i.e. the MAXSIMA project (EC 2012). In this project the TRIGA reactor at the INR institute at Pitesti, Romania, will be used for a rapid transient experiment by delivering a power pulse of several milliseconds to a dedicated capsule containing a fast reactor UO2 (or MOX) fuel segment.

Description

We propose to extend the existing fuel performance analysis capabilities within the MOOSE framework to the conditions encountered during rapid excursions, in which PCMI is the dominant phenomenon. The objectives, which are connected to three consecutive phases of the PhD work, are as follows:

(i) to extend the integral MOOSE model that already includes general physical phenomena (neutronics, thermal-hydraulics, thermo-mechanics) with material models for fuel modeling on short timescales, i.e. during a burst. This would allow to code to treat the intimate coupling between the neutron transport that initiates the power burst together with its thermal feedback and a detailed thermo-mechanical analysis during the ultrafast (millisecond range) deformation of the fuel and cladding. Here, the strong coupling between the various physical mechanisms can only be properly captured by numerical methods that reflect the same inherent coupling. Our work will be based on the use of Jacobian-Free methods (Knoll and Keyes 2004) that have proven both accurate and efficient for such multi-physics simulations.

(ii) to verify and validate the extended computational model for the normal operating regimes either by comparison with existing fuel performance tools available at SCK•CEN such as MACROS (Lemehov, Sobolev and Verwerft 2011) or TRANSURANUS (Lassmann 1992), or with existing data from past fuel experiments in the BR-2 reactor. For the challenging pulse regime we can verify the model results by using simplified cases and manufactured analytical solutions.

(iii) to employ the extended fuel performance tool for the simulation of the PCMI phenomena during rapid transient experiment that is to be performed in the TRIGA reactor in the MAXSIMA project. Due to the probabilistic nature of the problem, we expect uncertainty analysis to play an important role in valuing/comparing our results to experimental data. We will include such analyses in our research where we will base ourselves on recent work by the Physics of Nuclear Reactors group of TU-Delft (Gilli, et al. 2012) (Perko, et al. 2012). Finally, the analyses will provide in an improved insight in fuel failure mechanisms and failure thresholds during rapid transients which is important for future fuel designs.

Nr of positions available : 1

Research Fields

Engineering

Career Stage

Early stage researcher or 0-4 yrs (Post graduate)

Research Profiles

First Stage Researcher (R1)