KATANA Experiment

KATANA JSI Water Activation Loop

The KATANA water activation facility is located in the hall of the TRIGA Mark II nuclear reactor of the “Jožef Stefan” Institute (JSI). It was designed and built for research into water activation under fusion-relevant conditions. The TRIGA reactor at JSI can be operated in both steady-state and pulsed mode. This enables continuous measurements on the KATANA device over several hours and the possibility to simulate the operating regime of fusion reactors. KATANA will provide detailed insights and the possibility to validate calculation methods for the water activation process under fusion-relevant conditions and much more, which is directly relevant for the preparations for the operation of the large fusion research reactor ITER.
The basic concept of the water activation loop system consists of a pipe loop partially inserted into the Radial Piercing Port (RPP). The three main components are: the "inner activation part", which is located inside the radial piercing port in close proximity to the reactor core and where most of the water activation process takes place, narrow "transport tubes" that lead the activated water outside of the RPP towards the "outer observation part" of the loop, around which various gamma and neutron detectors are arranged. All the necessary equipment, e.g. pump, flow meters, temperature/pressure sensors, water filling system, etc., is located outside the RPP.
The main objective of the design optimisation was to create a flexible and compact experimental setup that will enable benchmark quality experiments on the water activation process. For this reason two loops, primary and secondary, were considered. The primary loop should be as short as possible to achieve a high total activity of N-16 and N-17 within the outer observation part, which leads to a lower experimental uncertainty, e.g. for performing shielding experiments using ITER relevant materials. Furthermore, by using a 3-way valve, the water can be fully or partially distributed between the primary and secondary loop, i.e. to mimic leakage between the loops. Such a so-called decay or delay loop allows a longer travel time of the activated water, resulting in a N-16/O-19 isotope ratio in favour of O-19. The use of these two distinct loop components, each optimised for its specific function, enhances the overall performance and accuracy of the system. To ensure personnel safety, the experimental area is surrounded by thick concrete blocks arranged in maze-like configuration to provide a low radiation background in the reactor hall.