Development and optimization of nuclear heating measurement techniques in Zero Power experimental reactors

The objective of this study is to develop nuclear heating measurement methods in Zero Power experimental reactors. This paper presents the analysis of Thermo-Luminescent Detectors (TLDs) and Optically Stimulated Luminescent Detectors (OSLDs) experiments in the MINERVE research reactors at the French Atomic Energy and Alternative Energies Commission center in Cadarache. The experimental sources of uncertainties on the dose have been reduced by using the optimum conditions of charged particle equilibrium (CPE) of the calibration step and reactor measurement for each detector types; by improving the process of the TLDs/OSLDs reading and calibration processes. The interpretation of these measurements needs to take into account several correction factors related to both the environment of calibration step and the type of detectors used. Similarly, the correction due to the neutrons contributions to the total dose integrated by the detectors is evaluated with Monte Carlo calculation methods. These calculations are based on MCNP simulations of neutron-gamma and gamma-electron transport coupled particles using ENDF/B-VI nuclear data library. TLDs and OSLDs are positioned inside aluminum or hafnium pillboxes. Comparisons between calculated and measured integral gamma-ray absorbed doses by TLDs in these new experiments are carried out in the MINERVE reactor in the surrounding aluminum material. They show that calculations slightly overestimate the measurements by about 8%. By using OSLDs, the calculation slightly overestimates the measurement by about 6%.