Proposed design for the PGAA facility at the TRIGA IPR-R1 research reactor

Abstract

BackgroundThis work presents an initial proposed design of a Prompt Gamma Activation Analysis (PGAA) facility to be installed at the TRIGA IPR-R1, a 60 years old research reactor of the Centre of Development of Nuclear Technology (CDTN) in Brazil. The basic characteristics of the facility and the results of the neutron flux are presented and discussed.FindingsThe proposed design is based on a quasi vertical tube as a neutron guide from the reactor core, inside the reactor pool, 6 m below the room’s level where shall be located the rack containing the set sample/detector/shielding. The evaluation of the thermal and epithermal neutron flux in the sample position was done considering the experimental data obtained from a vertical neutron guide, already existent in the reactor, and the simulated model for the facility.MethodsThe experimental determination of the neutron flux was obtained through the standard procedure of using Au monitors in different positions of the vertical tube. In order to validate both, this experiment and calculations of the simulated model, the flux was also determined in different positions in the core used for sample irradiation. The model of the system was developed using the Monte Carlo code MCNP5.ConclusionThe preliminary results suggest the possibility of obtaining a beam with minimum thermal flux of magnitude 106 cm-2 s-1, which confirm the technical feasibility of the installation of PGAA at the TRIGA IPR-R1 reactor. This beam would open new possibilities for enhancing the applications using the reactor.

Monte Carlo Simulations for a Preliminary Design of TRIGA IPR-R1 PGAA Facility

“…To set up a preliminary model of the PGAA method at the IPR-R1 reactor and estimate the calculations at PGAA facility, in this work was used the models of previous studies [12,[15][16][17] that were validated through the MCNP5 code.…”

“…The laboratories around the world that apply the PGAA method using a nuclear reactor as a neutron source, in general have a structural design that allows the extraction of the neutron flux horizontally [12]. As the IPR-R1 reactor is located inside a pool, the extraction of the neutron flux cannot be performed in the same manner (horizontally).…”

“…1. Moreover, this cylinder should be inclined in a way that it would reach the heavy structure of the rack containing the shielding, the sample and the detector located directly over the reactor's pool, for security reasons [12][13][14]. This is the main difficulty to extract a neutron beam from the TRIGA IPR-R1 reactor.…”

“…The model developed in this paper is based on these already validated models and on a MCNP5 model validated by this research in a previous study of the neutron flux in the vertical extractor [12]. Thus, the neutron flux behavior along the angled extractor was calculated as well as the neutron flux; capture reaction rate and detection limits along the samples of the selected isotopes.…”