Heating due to energy deposition of intense ionizing radiation in samples and structural materials of nuclear reactors poses severe limitations in terms of cooling requirements for safe reactor operation, especially in high neutron and gamma flux environments of material testing fission reactors (MTRs) and novel fusion devices. A bilateral CEA-JSI research project was launched in 2018 with the objective to measure the gamma heating rates in standard reactor-related materials (graphite, aluminium, stainless steel and tungsten) as well as fusion-relevant materials (low-activation steel Eurofer-97 and Nb3Sn superconductor) in the JSI TRIGA reactor by means of gamma calorimeters. The calorimeter design will be based on the the CALMOS-2 calorimeter developed at the CEA and used to perform gamma heating measurements in the OSIRIS MTR in Saclay. In order to optimize the detector response inside the JSI TRIGA reactor field and not to perturb the measurement field, a detailed computational analysis was performed in terms of energy deposition assessment and measurement field perturbation using the MCNP v6.1 code, and in terms of heat transfer using the COMSOL Multiphysics code. The abovementioned activities enabled us to finalize the detector design with the experimental campaign planned for the end of year 2019
COBISS.SI-ID: 13473795
Interest on development of computational tools for calculations of radiation field due to decay of radioactive activation and fission products (delayed radiation) has increased in recent years, mainly due to requirements on shutdown dose rate for the future ITER fusion reactor and material testing reactors (MTR), where gamma heating values of several 10 Wg can be reached in reactor structural components during reactor steady state operation and for characterization of research reactor irradiation facilities. Previous experimental work shows a roughly 30% contribution of delayed gamma rays to the total gamma ray flux. An extensive experimental campaign at the JSI TRIGA reactor has been carried out using multiple ionization and fission chamber detectors for gamma and neutron field characterization. A series of reactor power steps was performed with said detectors in different irradiation positions during steady reactor power and after shutdown. The reactor and the used detectors, along with irradiation power steps have been modelled in detail using the JSIR2S code system framework to compare measured and calculated fluxes and dose rates. Simulated results are in good agreement with measurements and with experimentally obtained values of delayed gamma fractions from previous work.
COBISS.SI-ID: 27529731
The JSI TRIGA reactor features several in-core and ex-core irradiation facilities, each having different properties, such as neutron/gamma flux intensity, spectra and irradiation volume. A series of experiments and calculations was performed in order to characterise radiation fields in irradiation channel thus allowing users to perform irradiations in a well characterised environment. Since 2001 the reactor has been heavily used for radiation hardness studies for components used at accelerators such as the Large Hadron Collider (LHC) at CERN. Since 2010 it has been extensively used for testing of new detectors and innovative data acquisition systems and methods developed and used by the CEA. Recently, several campaigns were initiated to characterise the gamma field in the reactor and use the experimental data for improvement of the treatment of delayed gammas in Monte Carlo particle transport codes. In the future it is planned to extend the testing options by employing pulse mode operation, installation of a high energy gamma ray irradiation facility and allow irradiation of larger samples at elevated temperature.
COBISS.SI-ID: 13466115