Analysis of the TRIGA 2000 core reshuffling scenario based on fuel burn-up and fuel density has been done. One of the requirements of Bandung TRIGA 2000 Reactor reliability is the implementation of maintenance and surveillance activities with predetermined Operation and Limits Conditions (OLC) so that the safety parameters will be met. Core management is one of the maintenance activities carried out. Safety parameters that are required to be fulfilled in the core management include the shutdown margin and the power peaking factors. The scenario carried out in the core management in this analysis that was doing the core compaction by sorting the fuel position on the core based on the fuel burnup and the fuel density. Each core management method was carried out in 4 scenarios. The purpose of this analysis is of course to compare both methods and also to get the optimal scenario to be applied to the core of the existing Bandung TRIGA 2000 Reactor. From the eight proposed scenarios, obtained two scenarios that meet the requirements of shutdown margin and power peaking factor from the OLC, namely scenario 2 with the k-eff value obtained 1.01243, and scenario D with the k-eff value obtained 1.02031. Therefore, scenarios 2 and D will then be proposed as the existing Bandung TRIGA 2000 Reactor core configuration scenario.

Currently, Indonesia through BATAN is operating three research reactors, namely the RSG-GAS reactor with the power of 30 MWt at Puspiptek south Tangerang (the first criticality in 1987), the TRIGA 2000 reactor with the power of 2 MW in Bandung which the first criticality in 1965 with the power of 250 kW, was increased to 1 MW in 1971, and further upgraded to 2 MW in 2000. Beside that, there is Kartini reactor with a power of 100 kW located in Yogyakarta (first criticality in 1979). These reactors are quite old, and in accordance with Bapeten regulations, have carried out the first periodic safety review, to obtain a reactor license for the next 10 years of operation. In line with this, one of BATAN's current national research programs is to increase the production of radioisotopes and radiopharmaceuticals, where reactors play a very important role in the production of certain isotopes. In tracing the data obtained from operational reports related to irradiation requests from reactor users, namely PTRR, PSTNT, and PT INUKI for radioisotope production, which has been carried out in the last 5 years, May 2015 until 25 August 2020, show that the irradiation request at RSG-GAS is still not optimal. In term of the utilization of RSG-GAS, it can still be optimized, which in this case needs to be balanced with post-irradiation processing capabilities. Meanwhile, from the results of tracing and data collection, it can be shown that at this time the reactors are still operating. The utilization activities of the reactors complement each other according to their age and facilities.

CALCULATION OF NEUTRON FLUX DISTRIBUTION AT PIERCING BEAM PORTS OF PLATE TYPE RESEARCH REACTOR BANDUNG. Based on a strategic plan of TRIGA 2000 Bandung's future operation, BATAN has already decided to implement an option to convert the fuel elements core of TRIGA 2000 from using the cylindrical type of elements produced by General Atomic to MTR plate type of fuel elements produced by local fuel element manufacture. The core design calculation has proved that the core configurations of 5 x 5 matrix using local plate type fuel elements met the requirement of core neutronics design. In addition to the current core configuration, further study must be added to consider the use of beam ports as utilization facilities in the design. The neutron flux distribution at piercing beam port has been calculated based monte carlo algorithm using TRIGA MCNP and MCNP software. The calculation result showed that at piercing beam port surface neutron flux distribution is not quite symmetric. The highest neutron flux at piercing beam port is 9.4 × 10 8 (2. ⁄), where as the flux of neutron thermal energy group is 3.54 × 10 8 (2. ⁄). These results are considerably appropriate for such core configuration and as a result, they can be used as a basic data for designing Plate Type Research Reactor Bandung, especially for neutron diffraction experiment

The reactivity value of the Bandung TRIGA 2000 reactor core has decreased over time, so the power generated by the reactor is also getting smaller, despite the control rod position is fully withdrawn. Therefore, it is necessary to reshuffle and refuel the fuel element to increase the excess reactivity by considering the safety parameters, such as axial and radial power peaking factors, DNBR, dTsat, and temperature on the cladding and in the center of the fuel element. The analyzed reactor safety parameters are the number of fuel elements, which varied at 105, 110, and 115 elements, as well as power peaking factor, which varied at 1.55, 1.65, 1.75, 1.85, and 1.95. The calculations were done using MCNP and COOLOD-N2 programs. If DNBR ≈ 1.3 is determined as the safety limit for the operation of the Bandung TRIGA 2000 reactor, at PPF 1.95 (105, 110, and 115 fuel elements), it can be considered to operate the reactor at the power of 600-700 kW. However, at PPF of 1.75 (105, 110, and 115 fuel elements), the reactor can be operated at the power of 700-800 kW, and at PPF of 1.55 (105, 110, and 115 fuel elements), the reactor can be considered for operation at the power of 800-900 kW. The results of these calculations can be used for consideration in determining the operating limits of the Bandung TRIGA 2000 reactor.Keywords: TRIGA 2000, fuel element, power peaking factor, DNBR, boiling