ANALYSIS OF AXIAL NEUTRON FLUX MEASUREMENT USING 197AU SAMPLE ACTIVATION AT THE TRIGA 2000 BANDUNG REACTOR IRRADIATION FACILITY

• Main Author: Roswita, Fahma
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/86883
• Institution: Institut Teknologi Bandung

Neutrons play a crucial role in nuclear reactors, particularly in research reactors, as they are used in various studies and radioisotope production. One of the research reactors in Indonesia is the TRIGA 2000 Reactor in Bandung. This research reactor has the potential to be developed into an isotope production reactor (IPR) and is a priority for the revitalization of nuclear facilities. However, the operating license for the TRIGA 2000 reactor will expire in 2027, necessitating supporting data for the license renewal application. Neutron flux distribution data within the reactor core is essential as supporting data for both operational licensing documents and initial research data to enhance the utilization and potential of the TRIGA 2000 reactor. Therefore, neutron flux measurement is a critical aspect of nuclear reactor management, particularly to determine the axial neutron flux distribution based on the current core configuration. This data can be used for further study and evaluation. Neutron flux measurement is commonly performed using the neutron activation method. The 197Au sample is used because it has a high neutron absorption cross-section and only one energy peak, making it easy to analyze. The Cd sample is used to encapsulate the 197Au sample to absorb neutrons in the thermal energy spectrum. Thus, the neutron flux interacting with 197Au is in the epithermal or higher energy spectrum. The thermal neutron flux value in the measurement is obtained from the cadmium ratio. The new samples used in this study have been tested and compared with old samples, proving to be more optimal in absorbing neutrons. The experimental measurement method was first tested at the Kartini reactor, which has the same type as the TRIGA 2000 reactor. The test results showed good agreement at the half-axial position downward when compared with the MCNP simulation. The simulation data was obtained from the Directorate of Nuclear Facility Management (DPFK) – BRIN. The tested method was then applied to neutron flux measurements in the central thimble, pneumatic transfer system, and lazy susan of the TRIGA 2000 reactor. These three irradiation facilities have dry pipe conditions. Specifically, for the central thimble channel, the samples were arranged in five sleeves connected to obtain complete full axial core data. In the pneumatic transfer system and lazy susan, only one sleeve was inserted. The samples were irradiated for five minutes at an operating power of 100 kW. The axial neutron flux distribution in the active core of the TRIGA 2000 reactor irradiation facilities showed that the middle axial position tends to have high neutron flux values for total, epithermal, and thermal neutron categories. The highest total neutron flux value was 1.49E+11 n/cm² s at the pneumatic system position. The highest epithermal neutron flux value was 3.21E+10 n/cm² s at the central thimble position. Meanwhile, the highest thermal neutron flux value was at the pneumatic system position with a value of 1.27E+11 n/cm² s. The simulation data used as a comparison for the experimental results showed that the simulation values were always higher than the experimental values. Although there is a data gap, the pattern and trend of the data distribution tend to be the same. These measurement results are expected to be important supporting data in the preparation of licensing documents and policy justification related to the continued operation and utilization of the TRIGA 2000 Bandung reactor in the future.