International Topical Meeting on Nuclear Research Applications and Utilization of Accelerators

4-8 May 2009, Vienna

Reactivity Monitoring of a Subcritical Assembly Using Beam-Trips and Current-Mode Fission Chambers: The YALINA–Booster Program

M. Fernández-Ordóñez¹, D. Villamarín¹, V. Bécares¹, E.M. González-Romero¹, C. Berglöf², V. Bournos³, I. Serafimovich³, S. Mazanik³, and H. Kiyavitskaya³

¹CIEMAT, Madrid, Spain
²Reactor Physics Department, Royal Institute of Technology, Stockholm, Sweden
³Joint Institute for Power and Nuclear Research, National Academy of Sciences, Minsk, Belarus

Corresponding Author: m.ordonez@ciemat.es

Transmutation of spent nuclear fuel in Accelerator-Driven Systems (ADS) is considered as a key technology for achieving sustainable nuclear energy. In the design of future ADS facilities, the reactivity monitoring system is of highest importance. An extensive experimental program devoted to reactivity monitoring of ADS has been carried out at the subcritical facility YALINA–Booster in the framework of IP–EUROTRANS. The main objective, besides the qualification of the reactivity monitoring techniques, has been to develop electronic chains that can be used in a full power ADS. For this purpose, YALINA–Booster couples a D–T neutron generator to a flexible zeropower subcritical assembly with a coupled fast-thermal neutron spectrum. The high intensity of the accelerator and the possibility to work in continuous or pulsed mode allowed the study of the current-to-flux relationship, beam-trip experiments and dedicated experiments for loading and start-up procedures. In addition, the experimental facility provided the opportunity to test electronic chains in current mode, which correspond to the most probable condition in a full power ADS. The experimental program has mainly been focused on the current-to-flux and beam-trip methodologies using detectors operating either in current or pulsed mode. However, in order to achieve the reference reactivity values of the different loading configurations, an extensive set of measurements based on pulsed neutron source techniques has been carried out. In addition, neutron noise measurements have also been performed. These studies are presented in separated papers within this conference. At present, the experimental campaign has been finished and, for the first time, the reactivity of a subcritical system has been measured within a single instantaneous beam trip ( ~20 ms) using fission chambers operating in current mode. The necessary electronic chains to operate the fission chambers in this mode have been developed at CIEMAT. The preliminary results of our analysis show that the reactivity values obtained applying the Sjöstrand method and the slope-fit method using data from current-mode detectors are compatible with those obtained when using standard pulsed-mode detectors (presented also in this conference). The validity of the reactivity determination methods using fission chambers operating in current mode has been stated.

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