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WP1: ADS on-line reactivity monitoring methodologies

Building on the former activities accomplished in the previous FPs, namely GUINEVERE in FP6 IP-EUROTRANS, investigations on the subcritical VENUS-F (Lead/Uranium) core coupled with GENEPI-3C accelerator are proposed to be extended.

The purpose of this work package is to extend and finalise the investigations of the subcritical configurations for validation of the methodologies for on-line reactivity monitoring of ADS systems.

First, besides the SC1 core with keff=0.97, investigated in FP-6 GUINEVERE project, two additional SC2 & SC3 configurations for the nominal operation mode of ADS will be investigated in the FREYA project with keff=0.95 and keff ≥ 0.99. These two variants of the reference configuration will be obtained by changing the core loading in the peripheral region without other modifications in the reflector or source characteristics. The same kind of experiments as in SC1 will be carried out in the SC2 & SC3 cores (MSM, PNS, current-to flux...) to obtain a full set of data points for the validation of the reactivity monitoring methodology. Reference to the critical configuration (CR0 in FP-6) will be checked between the SC2 and SC3 cores. A study of the alpha-modes theory for the analysis of experiments will be performed to enlarge the possibilities of measurement interpretation. Application of neutron noise methods is also under consideration and a detailed evaluation of such measurements by Monte Carlo simulations is planed.

Following this, based on the reference configuration, specific configurations with deep subcriticality keff-values in the range of 0.85-0.95 will be determined. In these configurations, especially the performance of the PNS Area method and the current-to-flux technique will be investigated. These situations are needed to be studied for establishing the accuracy and methodology of core loading procedures.

Next here, in the framework of FP-5 MUSE, the reflector effect has shown to be of significant influence on specific reactivity monitoring techniques. In order to investigate the robustness of measurement techniques with regard to the reflector effect, it is foreseen in the FREYA project to perform experiments with different reflector materials such as steel, concrete. Certain man-efforts will be spent here on the VENUS-F reflector reloading. To complete the validation of the methodology for subcriticality monitoring, it would be of significant added value if the robustness of the reactivity indicators with regard to a change in vertical position of the neutron source could be investigated in view of possible variations of the height of the spallation source in an ADS.

Last, but not least an analysis and review of the results of the ADS reactivity monitoring methods at WP1 FREYA and also of previous related 5th and 6th Framework Programmes (MUSE, YALINA and GUINEVERE) will be carried out and a methodology for on-line reactivity monitoring in ADS with accuracy levels will be obtained. This work package is divided in four separate tasks. The first is devoted to the subcritical configurations investigations with keff=0.95 and keff ≥ 0.99. The second task is dedicated to the core studies with keff-values in the region 0.85-0.95. The third task is related to the reflector effect and vertical position of the spallation source investigations. At the end of this work package, a description of a validated ADS on-line reactivity monitoring methodology will be given.