Thermal neutron distribution measurement at core of the LVR-15 reactor - 169

The LVR-15 reactor is a light water research type which is situated in Rez near Prague. The maximum thermal power is 10 MW. The LVR-15 reactor is used mostly for irradiation of material specimens for a given period with appropriate neutron fluence rate. It is important for such experiments to know neutron fluence and energy spectrum in the sample. The paper describes measurement of thermal neutron distribution in four vertical channels in core of the LVR-15 reactor. The activation method with Cu foils was used for the measurement. The mean power during the irradiation was 0.1 MW. The gamma activities were measured with spectrometric assembly including the HPGe detector. Nearly all the data were loaded automatically without any manual typing which guarantees the high reliability of final results. The results of the measurement have been compared with data calculated with three computer codes - with a diffusion nodal program NODER in a four group approximation, with the general purpose Monte Carlo radiation transport code MCNP-4B and the DLC-189 library, and with the two-dimensional transport code DORT. The measurement and calculation was applied for reactor core configuration which was specially designed for boron neutron capture therapy experiments in June of 1999. (author)