International Topical Meeting on Nuclear Research Applications and Utilization of Accelerators

4-8 May 2009, Vienna

Pulsed Neutron Source Reference Measurements in the Subcritical Experiment YALINA– Booster

C. Berglöf¹, M. Fernández-Ordóñez², D. Villamarín², V. Bécares², E.M. González-Romero², V. Bournos³, I. Serafimovich³, S. Mazanik³, and H. Kiyavitskaya³

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

Corresponding Author: calle@neutron.kth.se

An extensive experimental program devoted to reactivity monitoring of accelerator-driven systems has been carried out at the zero-power subcritical facility YALINA–Booster. The work is a part of a joint collaboration between several European research institutes through the European research programme for the transmutation of high level nuclear waste in an accelerator driven system (IP– EUROTRANS) in the 6^thEU Framework Programme. Pulsed Neutron Source (PNS) experiments have been carried out to achieve the reference reactivity values for each configuration studied. In total, four different core configurations at three different subcriticality levels have been studied, with effective multiplication factors ranging from about 0.85 to 0.975. Two of the configurations have the same subcriticality level, but different source multiplication, thus making it possible to explore possible source multiplication effects. This was achieved by removing highly enriched fuel located close to the target and compensating by adding low enriched fuel at the core periphery until the same reactivity was reached. For each core configuration, except the most deep subcritical configuration, an additional subconfiguration was obtained by inserting the control rods into the core, meaning that in total seven subcriticality levels were studied. The techniques applied were the Sjöstrand method and the prompt neutron slope fitting technique. Reactivity values have been obtained for detector positions in all three regions of the complex YALINA–Booster core: the fast booster zone, the thermal zone and the reflector. It is shown that the experimental results from the Sj¨ostrand method, without correction factors, carry strong spatial effects. For the first time, possible source multiplication effects on the area ratio technique are shown.

Full text paper