SOFTWARE FOR DETERMINATION OF THE THERMAL NEUTRON FLUX IN A NUCLEAR REACTOR

In this study thermal neutron flux distribution was performed using the activity of the irradiated activation detectors: Au and In foils. The neutron flux in the IEA-R1 nuclear reactor at IPEN/SP in the pneumatic station was then house software and the results were compared. The data permits a discussion about the performed of this software. An analytical measurement is usually performed aiming to quantify elements (i.e., the composition) of a given species in a defined mass or volume. The (n, γ) nuclear reaction produced in a nuclear reactor is very used for analytical works. The neutron activation procedure combined with computerized high-resolution gamma-ray spectrometry offers nondestructive and multi-element routine analysis needed in such areas (environmental monitoring, geochemistry, medicine, etc) and technological processes. Nuclear reactors, mainly thermal neutron reactors, are very useful for this kind of analyses because a lot of elements could be quantified (about 75 elements less than 0.01 μg can be determined). To performed theses measurements the Instrumental or Parametric procedure of neutron activation can be applied [1]. The Instrumental technique is performing using standard while in the Parametric procedure the thermal neutron flux must be obtained. In this study thermal neutron flux distribution was performed using the parametric procedure. For this purpose the activity of the irradiated activation detectors (Au and In foils detectors) are obtained using inhouse software which correlated the measured parameters with the constants physics involved. The results for Au and In detectors were compared. 2. NEUTRON FLUX DISTRIBUTION IN THE IEA-R1 NUCLEAR REACTOR In a nuclear reactors fast neutron are first produced in the fission reactions where the energy distribution of the prompt fission neutrons following the Watt’s spectrum. These neutrons are gradually slow down due all the collision with the atoms of the moderator and as result the thermal neutron flux distribution. These thermals neutron are in equilibrium with the atoms of the medium and theirs velocity behavior to the follow the Maxwell- Boltzmann distribution. The epithermal neutron flux distribution is also present and it could be significant in function of the irradiation position, and it also must be also determined.