New Experimental Instrumentation for Study of Reactor Dynamics at Zero Power Reactor VR-1

The paper presents new experimental device developed for a study of the reactor dynamics at zero power reactor VR-1 and the first experiences of its utilisation. VR-1 reactor has been operating by Czech Technical University (CTU). It is a pool-type light water reactor based on enriched uranium with maximum thermal power 1kW and for short time period up to 5kW. The reactor has been utilised very efficiently particularly for education and training of university students and NPP's specialists more than 20 years. The improvement of the reactor equipment and experimental instrumentation is necessary background for keeping the reactor attractive for students. The example of such way is the installation of the device for dynamics study in the VR-1 reactor which was developed in a close cooperation between CTU and SKODA JS Company. The device is based on a pneumatic drive which allows carrying out fast movement of absorbing or fissionable specimens. In this way the fast reactivity changes are caused in the reactor core. The specimen is located in a dry aluminium channel (with outer diameter 14 mm). Channel dimension allows its placing into various core positions. A user can select one of the three predefined modes for specimen movements: step, pulse or cycle. The step mode represents the specimen transfer from the start position to the upper/lower position and stay there within predefined time. The pulse mode allows the specimen transfer either from the start position to the upper/lower position and its prompt return to the start position. The cycle mode represents a periodical movement of sample around the start position. One cycle is defined as the specimen movement from the start position to the upper/lower position and then to the lower/upper position and back to the start position. Therefore it is possible to study the reactor response to wide range of reactivity perturbations and observe its dynamics behaviour, e.g. pulse or transient characteristic. Furthermore the device can be used also as an experimental tool, e.g. for determination of βeff. The new experimental instrumentation for study of reactor dynamics has been included into the education at the reactor at the end 2009. The first experiences of its utilisation show that it brings new potential in the educational process and improve quality of training at the reactor VR-1. (author)