Thermal and epithermal neutron fluence rates in the irradiation facilities of the TRIGA IPR-R1 nuclear reactor

The TRIGA IPR-R1 nuclear reactor at the Centro de Desenvolvimento da Tecnologia Nuclear CDTN/CNEN, Belo Horizonte, Brazil, has three irradiation facilities: a rotary specimen rack outside the reactor core with 40 irradiation channels which provide large scale isotope irradiation; the central tube placed at the center of the reactor core which permits sample irradiation with maximum neutron flux, as well as neutron beam extraction; a pneumatic transfer tube which makes possible the analysis of short half-life radioisotopes. The aim of this work is to evaluate the thermal and epithermal neutron fluence rates in the three irradiation facilities of the IPR-R1. Al-0.1%Au reference materials were irradiated bare and Cd-covered, at 100 kW thermal power, and gamma spectrometry was applied with an HPGe detector. For the rotary specimen rack, the values obtained for thermal and epithermal neutron fluence rates are (8.2 ± 0.2) × 10(11)n.cm-2.s-1 and (3.5 ± 0.1) × 10(10)n.cm-2.s-1, respectively. For the pneumatic transfer tube and the central tube, epithermal neutron fluence rate values are respectively (3.3 ± 0.2) ×10(9)n.cm-2.s-1 and (2.6 ± 0.1) x 10(11)n.cm-2.s-1. For these facilities, thermal neutron fluence rate values are (2.5 ± 0.2) × 10(11)n.cm-2.s-1 and (2.8 ± 0.1) × 10(12)n.cm-2.s-1, respectively. Knowledge of these parameters will be fundamental in the planning of sample irradiation for analysis or radioisotope production in a more accurate way.