ANALYSIS OF FISSION PRODUCTS RELEASE FOR PELUIT-40 UNDER NORMAL OPERATING CONDITION AND DLOFC CONDITION

• Main Author: Purwaningsih, Anik
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/83840
• Institution: Institut Teknologi Bandung

Pembangkit Listrik dan uap untuk Industri (PeLUIt) is a cogeneration reactor based on a high-temperature gas-cooled reactor (HTGR) that has been designed by the National Nuclear Energy Agency (now the Nuclear Energy Research Organization, BRIN). The safety feature of HTGR lies in the tri-structural isotropic (TRISO) fuel particles, which are designed to maintain structural integrity and fission products under all reactor operating conditions. Prediction of fission product release is required for design safety analysis. The ability of the fuel to withstand fission products under both normal operating conditions and accidents is important to analyze as a requirement for fulfilling the design license. PeLUIt40 is a HTGR-based reactor design with a thermal power of 40 MW and a geometric design that adopts HTR-10. To obtain approval for the design, analysis of fission product release under normal operating conditions and accident conditions is required. This study conducted a simulation to predict the release of fission products of PeLUIt-40 under normal operating conditions and accident conditions with the Depressurized Loss of Forced Cooling (DLOFC) scenario. The simulation was carried out using the stand-alone version of the Source Term Analysis Code System (STACY) software. STACY requires burnup data (% fissions per initial heavy metal atom, FIMA), fast neutron fluence, and inventory. The calculation for these three input parameters was carried out using OpenMC. The analysis of fission product release on PeLUIt-40 was simulated for two fuel cycle schemes, namely the Once-Through-Then-Out (OTTO) cycle and the 5-pass cycle. Under normal operating conditions, the fuel temperature was simulated at 977 oC. The results of the OpenMC calculation for the burnup value in the OTTO cycle were 74.07 MWd/KgHM and in the 5-pass cycle were 78.43 MWd/KgHM. Fission product release analysis was carried out on radionuclides that have significant radiological effects, namely Ag110m, Cs137, I131, and Sr90. The simulation results using STACY showed that the largest release fraction was Ag110m. The Ag110m fission product release fraction in both the OTTO cycle and the 5-pass cycle was two orders of magnitude lower than the safety requirement limit of 1.6x10-4. In addition, the simulation results also showed that no particles were damaged during the irradiation process for both fuel schemes. This confirms that the PeLUIT-40 fuel performs well for normal operations. Meanwhile, the analysis of fission product release under accident conditions with the DLOFC scenario was simulated with a heating time of 100 hours. The highest release fraction was Ag110m due to its high diffusivity. The Ag110m release fraction in the OTTO cycle was two orders of magnitude smaller than the Ag110m release fraction in the 5-pass cycle. Except for Ag110m, the fission product release fraction at DLOFC conditions for both cycles is still below the safety limit for HTR-module 6.6x10-4. To determine the fuel performance, the fuel temperature was simulated at 1600 oC and 1700 oC constant for 100 hours. The simulation results at a constant temperature of 1700 oC showed that the release fraction exceeded 6.6x10-4 and there was a failure of coated particles. In the simulation with a constant temperature of 1600 oC, although the release fraction was still below 6.6x10-4, there was a failure of coated particles caused by the release of Cs137. However, this failure fraction of coated particles was not significant and was still within the acceptable limit of 2.24x10-5. Based on the simulation results, it is concluded that the PeLUIt-40 design studied in this thesis provides a fission product release value below the safety limit.