Static Modal Analysis of the Current-to-Flux Subcriticality Monitor for Accelerator-Driven Systems
Résumé
With Accelerator-Driven Systems (ADS), the incineration of large quantities of minor actinides is envisaged by coupling a particle
accelerator to a subcritical core. Despite the subcritical operation of the core, a monitoring tool is indispensable in an ADS for both safety
and operational purposes. Several experimental techniques are under investigation today within the European FP7 project FREYA (Fast
Reactor Experiments for hYbrid Applications) at the VENUS facility at SCK-CEN, where the lead fast zero-power VENUS-F core is coupled
to the GENEPI-3C deuteron accelerator. The proposed monitoring concept combines an initial reactivity determination, e.g. by the pulsed
neutron source technique, a long-term relative reactivity monitor, by the current-to-flux (CTF) technique, and an interim cross-checking,
by the source jerk technique. In this paper the CTF technique is presented as a candidate for continuous reactivity monitoring. Static
modal analysis is applied to evaluate the point kinetics relationship between accelerator source neutrons and the neutron flux. As a first
test case, the zero-power VENUS-F SC1 core is considered. Spatial correction on the CTF monitor is evaluated by measurement results for
the control rods worth at different detector positions. Good agreement between the modal and experimental spatial correction factor (SCF) is
found with 9 modes. Limited SCF are found in the VENUS-F reflector, far away from the perturbation. Modal analysis is envisaged for the
monitoring of burn-up in demonstrator ADS like MYRRHA.