International Topical Meeting on Nuclear Research Applications and Utilization of Accelerators

4-8 May 2009, Vienna

Reactivity Monitoring with Imposed Beam Trips and Pulsed Mode Detectors in the
Subcritical Experiment YALINA–Booster

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

¹Nuclear Innovation Group, CIEMAT, 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: vicente.becares@ciemat.es

Reactivity monitoring is one of the urgent problems that require a solution in order to achieve a license for a future full-scale ADS. As a part of the EUROTRANS experiments at the YALINA– Booster facility, presented in this conference, a set of measurements with imposed beam-trips has been performed. Traditionally, the source jerk method has been used in subcritical systems to obtain the reactivity by comparing the total neutron flux before the neutron source removal to the semi-stable delayed neutron flux after the source removal. The deuterium-tritium neutron source of the YALINA–Booster facility can, in addition to pulsed mode operation, operate with continuous beam with short imposed millisecond-scale interruptions, thus providing the possibility to monitor the reactivity at each beam trip in the source jerk manner. In order to test the validity of the beam-trip reactivity values determined by using detectors operating in currentmode (also presented in this conference), the reactivity values of the YALINA–Booster assembly obtained through the beam-trip technique using pulsed-mode detectors is presented in this work. In these experiments a beam-trip frequency of 1 Hz and an interruption time of ~ 20 ms have been chosen and two different subcriticality levels (with effective multiplication factor around 0.975 and 0.95, respectively) have been investigated. Moreover, the flexible core layout has allowed for two different loadings with close to equal subcriticality but different source multiplication characteristics, thus making it possible to explore the effect of the different source multiplications. In addition, the response of the imposed beam-trip reactivity monitoring technique to reactivity insertions and removals has been studied through control rod movements. Experimental data from fission chambers have been acquired from all three zones of the core: the fast booster zone, the thermal zone and the reflector.

The authors have assigned to the International Atomic Energy Agency a non-exclusive, royalty-free licence to publish this paper.

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