[en] The ''Instituto de Asuntos Nucleares'' of Colombia is responsible for IAN-R1 reactor operation, a 20 Kw. nuclear power machine, which became critical the first time on January 20th, 1965. The introduction of nuclear energy in Colombia has allowed to carry out many peaceful applications, where the reactor has played a significant role in support of these programmes. At this time, the main activities are: Educational and training activities; nuclear research; neutron activation analysis; delayed neutron analysis and radioisotopes production for using in agriculture, industry, hydrology and engineering. A description is made of the reactor aspects that have contributed to scientific and technological improvements

[en] From the thermal-hydraulics point of view, the nuclear reactor IAN-R1 was analyzed, with special attention to its power upgrade capabilities. In a first calorimetric evaluation, the nominal power was also calibrated as a consequence of a theoretical and experimental matching results

[en] The Reactor Group used the code WIMS reduced to five groups of energy, together with the code CITATION, and evaluated four configurations for a core, according to the grid actually installed. The four configurations were taken from the two proposals presented to the Instituto de Ciencias Nucleares y Energias Alternativas by General Atomics Company. In this paper, the Authors selected the best configuration according to the performance of flux distribution and excess reactivity, for a TRIGA core to be installed in the Nuclear Reactor IAN-R1

[en] The present work describes the procedure carried out for the preliminary determination of neutron flux parameters for the nuclear research reactor IAN-R1 (RNI IAN-R1) through the not covered triple monitor method in the nucleus peripheral irradiation position. Using this method, the thermal flux value (φ_th), the epithermal neutron flux symmetry factor (α) and the ratio between thermal neutron fluxes with respect to the epithermal neutron flux (f) were estimated. Those parameters were obtained by irradiating zirconium (Zr) monitors and a gold-aluminum alloy monitors (Au-Al 0.1% Au), which were irradiated at the G3 and G4 irradiation positions of the RNI IAN-R1. The following values were found for the parameters estimated at an operating power of 30 kW, φ_th= 2,1 * 10¹¹ cm² s^-1 (variance CV 4%), α = 0,02 (CV 83 %), and f =67 (CV 8 %). The high variance in α could be explained if we consider that the method only uses 3 capture reactions to describe the epithermal neutron spectrum. The variance could be improved by application of multimonitor methods for neutron flux characterization.

[en] A distribution was obtained for the thermal neutron flux in the MTR-type fuel elements of the IAN-R1 research nuclear reactor. The flux mapping was carried out with the detector activation technique with the use of Au-197 leaves. The power generated by each fuel element and by the nucleus was determined. Similarly, using the same procedure, the thermal neutron flux was found in the location of the neutron detectors for the control and safety instrumentation used for the operation of the nuclear reactor. This measurement allowed us to diagnose the operating performance of this equipment

[en] The program to modernize IAN-R1 research reactor control and safety instrumentation has been carried out considering two main aspects: updating safety philosophy requirements and acquiring the newest reactor control instrumentation controlled by computer, following the present criteria internationally recognized, for safety and reliable reactor operations and the latest developments of nuclear electronic technology. The new IAN-R1 reactor instrumentation consist of two wide range neutron monitoring channels, commanded by microprocessor a data acquisition system and reactor control, (controlled by computers). The reactor control desk is providing through two displays; all safety and control signals to the reactor operators; furthermore some signals like reactor power, safety and period signals are also showed on digital bar graphics, which are hard wired directly from the neutron monitoring channels

[en] This document presents a historical description of the nuclear research reactor IAN-R1. A contextualization is made about the origin of the reactor within the framework of the Atoms for Peace program, including the technical characteristics and the initial configuration of the core, which was replaced by nuclear fuel MTR technology (90 %) to a new fuel type TRIGA (20 %) (acronyms of material testing reactor and training, research, isotopes, general atomics respectively). In the same way, the characteristics of the two modernization that have been made to the instrumentation and control are presented, the first oriented to the installation of three nuclear channels two of wide range and one power channel, renovation of the control console and the installation of the data acquisition system (DAC) cabinet. The second modernization, which corresponds to the new instrumentation and control of the reactor, is oriented to the change of the control console which supports the control and supervision servers, a nuclear channel NP-1000, printer, four screens of the human interface machine HMI, keyboard of the bar handling system and two keyboards for each of the servers. In addition, the DAC was replaced by the instrumentation cabinet, which includes the reactor protection systems, the redundant control system and the supervision system. The instrumentation and control is characterized by the use of the Ethernet standard to achieve inter-connectivity of the systems, programming of the human machine interface (HMI) using open source code Java, and multi platform, logical separation of functions plying concepts of distributed control and modularity, redundancy, unique failure criteria and independence. The use of the reactor is shown, referring to the irradiation facilities available for irradiation of materials to be studied using the neutron activation analysis (NAA) technique. Likewise, irradiation is planned to support the use of the fission fingerprint dating technique, research and support to educational institutions through technical conferences and a visit to the nuclear facility.

[en] Infinite multiplication factor (Kinfinity) is calculated for research Reactors with MTR fuel type. Linear approximation for neutron flux in the cladding is utilized. The behavior of some typical parameters for IAN-R1 Reactor are shown when fuel enrichment varies. (author)

[en] In this paper, the parameters thermal to epithermal neutron flux ratio (f) and thermal neutron flux (θ_th) are estimated (assuming α = 0) for the periphery irradiation positions (G3-G4) available at Nuclear Research Reactor IAN-R1 that belongs to the Colombian Geological Survey. This estimation was performed by measuring the induced activity, from neutron capture reactions (n, y) in two reference soils, which were irradiated (n = 4) together with Al-Au monitors. Four reference capture reactions were considered in soils, which involve isotopes of elements with certified mass fraction and 1/v behavior for cross section variation in the range of thermal neutron energy. An average value of 33 (CV = 9%) for f was found, considering 8 positions in the irradiation container; this value is comparable with measurements reported for periphery irradiation channels of TRIGA type reactors. The average thermal neutron flux determined for the 8 position of the container resulted in 1,5 *10¹¹ ncm^-2 s^-1 (CV = 4 %).

[en] Using the Monte Carlo Method a computer program has been developed to simulate the neutron radiation transport and determine the basic parameters in shielding calculations. The program has been tested comparing dose conversion factors with kerma factors issued by the international commission on radiation units and measurements (ICRU) on its report (No 26 of 1987) giving errors less than ten percent showing the goodness of the method. The program computer transmitted backscattered and absorbed flux on energy less on each collision. when neutrons are produced by region source with knowing energy; results are given like conversion factors and reliability of this program allows a wide application on radiological and medical physics