Abstract
A series of fission rate profile measurements with miniature fission chambers, developed by the Commisariat á l’énergie atomique et auxénergies alternatives, were performed at the Jožef Stefan Institute’s TRIGA research reactor. Two types of fission chambers with different fissionable coating (235U and 238U) were used to perform axial fission rate profile measurements at various radial positions and several control rod configurations. The experimental campaign was supported by an extensive set of computations, based on a validated Monte Carlo computational model of the TRIGA reactor. The computing effort included neutron transport calculations to support the planning and design of the experiments as well as calculations to aid the evaluation of experimental and computational uncertainties and major biases. The evaluation of uncertainties was performed by employing various types of sensitivity analyses such as experimental parameter perturbation and core reaction rate gradient calculations. It has been found that the experimental uncertainty of the measurements is sufficiently low, i.e. the total relative fission rate uncertainty being approximately 5 %, in order for the experiments to serve as benchmark experiments for validation of fission rate profiles. The effect of the neutron flux redistribution due to the control rod movement was studied by performing measurements and calculations of fission rates and fission chamber responses in different axial and radial positions at different control rod configurations. It was confirmed that the control rod movement affects the position of the maximum in the axial fission rate distribution, as well as the height of the local maxima. The optimal detector position, in which the redistributions would have minimum effect on its signal, was determined.
Highlights
The use of advanced Monte Carlo computational codes for reactor core calculations has increased significantly in the last decade, generating the need for experimental verification through the use of benchmark experiments
At the Jozef Stefan Institute (JSI) Reactor Physics Department a Monte Carlo model of the TRIGA Mark II reactor has been created in Monte Carlo N-Particle TransportCode (MCNP) - Monte Carlo N-Particle Transport
Fission rate distributions in the core of the TRIGA reactor were measured in the experiment, the type of the detector was chosen on the basis of several operational constraints and expected neutron flux
Summary
The use of advanced Monte Carlo computational codes for reactor core calculations has increased significantly in the last decade, generating the need for experimental verification through the use of benchmark experiments. The model was mainly used for criticality calculations, but was later upgraded and used for calculation of other physical parameters of the core [2], [3], [4], such as the beta-effective and power distribution It has been thoroughly used for the computational support of experimental campaigns and for safety assessments of reactor experiments and modifications. A Monte Carlo computational model of the reactor and the experiment configuration was constructed, which was used to calculate the reaction rate distribution inside the core of the reactor and to evaluate the experimental and computational uncertainties together with major benchmark biases. The evaluation results can serve the purpose of testing and verifying the innovative design of the absolutely calibrated miniature fission chambers, as well as help validate the values of basic reactor parameters These are needed for the normalization of Monte Carlo neutron transport calculation results [9]. The high value of the absolute reaction rate benchmark was recognized with the inclusion of the experiment into the International Reactor Physics Experiment Evaluation Project Handbook (IRPhEP) [10]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
