High-Temperature Gas Reactor (HTGR) is a type of reactor that continues to be developed because of its advantages in terms of economic aspects, proliferation resistance, and safety aspects. One of the safety aspect improvements is due to the use of the Coated Fuel Particle (CFP). A coated fuel particle is a fuel with a diameter smaller than 1 mm and is protected by several carbon layers. In the Pebble Bed Reactor (PBR) type of HTGR design, the CFP is placed in a 6 cm fuel ball. How much CFP is put into the fuel ball will determine the neutronic characteristics of the reactor. In this study, the effect of the amount of CFP in the fuel ball on the 25 MWt PBR design using Thorium fuel and its impact on several important neutronic aspects, such as the effective multiplication factor, the amount of fuel enrichment, the utilization of fissile material, and the density of the fissile material formed. The calculation was performed by the Monte Carlo MVP / MVP-BURN code. This study found that the coated fuel particle fraction of 15% was the optimum value for the studied neutronic parameters.

Coated Fuel Particle (CFP) adalah tipe elemen bakar mikro berdiameter lebih kecil dari 1 mm, yang di dalamnya terdapat material fisil yang dilapisi oleh beberapa lapisan karbon. Pebble Bed Reactor (PBR) menggunakan konsep CFP untuk elemen bakarnya. CFP dimasukan ke dalam bola elemen bakar berukuran 6 cm dan disebar di dalam zona elemen bakar. Tujuan penelitian ini adalah untuk mempelajari pengaruh dari fraksi CFP terhadap beberapa parameter neutronik penting seperti faktor multiplikasi efektif, spektrum energi neutron, perubahan densitas material fisil dan fertil, serta tingkat utilisasi material fisil. Analisa dilakukan untuk pada sistem PBR berdaya 40 MWt dengan menggunakan kode Monte Carlo MVP/MVP-BURN, dengan fraksi CFP yang dianalisa berkisar antara 5-60%. Dari penelitian ini didapatkan bahwa fraksi CFP sebesar 10% memberikan nilai optimal untuk beberapa parameter neutronik terkait dan dapat dijadikan acuan untuk desain Pebble Bed Reactor berdaya 40 MWt dengan elemen bakar uranium.

East Nusa Tenggara (NTT) is an island that has an electrification ratio of 85.84%. Small power nuclear power plant could be applied in such a remote area, and High-Temperature Gas Reactor (HTGR) is one of the potential options. Based on data obtained from the Central Statistics Agency (BPS), an HTGR was designed. The purpose of the present study was to find the optimal excess reactivity for HTGR using the basic model of Japan’s HTTR (High-Temperature Engineering Test Reactor). The calculation was conducted using the Standard Reactor Analysis Code System (SRAC) with the Japanese Evaluated Nuclear Data Library (JENDL) 4.0 as the nuclear data library. Calculations for modified HTTR geometry and fuel configuration was performed and analyzed. As a result, for 1.6 times the HTTR geometry model, (7.00 - 8.75)% fissile enrichment with the addition of 0.065% B4C material is the best configuration to obtain the optimal excess reactivity. Meanwhile, for 1.5, 1.4 and 1.3 times HTTR geometry the best configuration values were (5.00 - 6.75)% fissile enrichment with 0.035% B4C, (6.00 - 7.75)% fissile enrichment with 0.045% B4C and (7.00 - 8.75)% fissile enrichment with 0.050% B4C, respectively.

There are small areas in Indonesia with insufficient electricity. High-Temperature Gas Reactor (HTGR) is a promising nuclear power plant that can be used in such areas as its capability to produce electricity and co-generation applications. A preliminary study on the neutronic aspect of the 150 MWt HTGR design is performed in this research. High Temperature Engineering Test Reactor (HTTR) is used as a basic model. The calculation was performed by Standard Thermal Reactor Analysis Code (SRAC) code, and Japanese Evaluated Nuclear Data Library (JENDL) 4.0 as nuclear data library. As a result, by increasing HTTR fuel assembly geometry to 1.5 times its original and using higher uranium enrichment, the reactor can be operated for five years.

The requirement for electricity increases with the growth of the human population. The existing power plants have not been able to fulfill all electricity requirements, especially in remote areas. The small long-life pressurized water reactor (PWR) is one of the solutions and innovations in nuclear technology that can produce electrical energy for a long time without refueling. This study aimed to analyze the neutronic of small long-life PWR that using Thorium-Uranium dioxide ((Th-U)O2) fuels with enriched Uranium-235 (U-235) and the addition of Gadolinium (Gd2O3) and Protactinium-231 (Pa-231) as the burnable poisons. The SRAC Code with the JENDL-4.0 nuclear data library had been used for the calculation method. In this study, the geometry of the two-dimensional (R-Z) reactor core with different fuel volume fraction was analyzed. Moreover, variations of the Uranium-235, Gadolinium, and Protactinium-231 fractions in the fuels were carried out. The result in this study was a PWR 420 MWt design using 60% Uranium dioxide fuel with enriched Uranium-235 of 10%-11%-12% and the addition of 0,0125% Gadolinium and 1,0% Protactinium-231 as the burnable poisons that could operate for thirteen years without refueling. The small long-life PWR design could produce a power density of 85,1 watts/cc with the reactivity for less than 4,6% dk/k.