Jurnal Pengembangan Energi Nuklir Vol. 22, No. 2, (2020) 129-136 129 Jurnal Pengembangan Energi Nuklir Laman Jurnal: jurnal.batan.go.id/index.php/jpen Criticality Analysis of HTR-10 using an Open Source Monte Carlo code OpenMC Ikhsan Mahfudin* 1 , Topan Setiadipura 2 1 Polytechnic Institute of Nuclear Technology, Jl. Babarsari, Kotak Pos 6101 YKBB Yogyakarta, Indonesia 2 Center for Nuclear Reactor Technology and Safety, Gedung No.80, Kawasan Puspiptek Tangerang Selatan, Indonesia ARTICLE INFORMATION ABSTRACT Article History: Submitted: 20 November 2020 Received in revised: 23 December 2020 Approved: 25 December 2020 Criticality Analysis of HTR-10 using an Open Source Monte Carlo Code OpenMC. As one of the advanced nuclear reactor designs, the capability to model and analyze the pebble bed reactor is essential. The availability and capability of an accurate open source and open access software for pebble bed reactor analysis are strategic. It can broaden the involvement of more institutions, including universities, which finally may improve the research and development in this field. The current study aims to develop the pebble bed core model and perform a criticality study of the HTR-10 core design. This study exploits OpenMC software's capability to model a double heterogeneity geometry using a TRISO Pack Model Building based on random sequential packing and closed random packing. Physical parametric surveys of the developed model show expected results in which the model can reflect the negative reactivity feedback of the HTR-10 design. The critical height of the HTR-10 model with Helium from the current model, VSOP, and MCNP are 125.881 cm, 125.804 cm, 126.116 cm, respectively. A code-to-code criticality analysis comparing the current model with VSOP and MCNP code reported by INET shows a good comparison. It suggests that the present method can be used for further pebble bed analysis. ABSTRAK Analisis kritikalitas HTR-10 Menggunakan Software Monte Carlo Open Source OpenMC. Sebagai salah satu desain reaktor nuklir maju, kemampuan untuk melakukan pemodelan dan analisis terhadap reaktor pebble bed adalah hal yang penting. Ketersediaan dan kemampuan dari sebuah software yang akurat, open source dan open access untuk analisis reaktor pebble bed sangatlah strategis. Hal ini dapat memperluas keterlibatan institusi, termasuk universitas, yang pada akhirnya akan meningkatkan penelitian dan pengembangan di bidang ini. Tujuan dari studi ini adalah untuk mengembangkan model teras pebble bed dan melakukan analisi kritikalitas desain HTR-10. Studi ini memanfaatkan kemampuan dalam software OpenMC untuk memodelkan geometri heterogenitas ganda menggunakan modul TRISO Pack Model Buiding berbasis random sequential packing dan closed random packing. Survey parameter fisis terhadap model yang dikembangkan dalam studi ini menunjukkan hasil yang diinginkan dimana model tersebut dapat menunjukkan fitur umpan balik negative dari reaktivitas terhadap termperatur yang merupakan fitur HTR-10. Ketinggian kritis dari model HTR-10 dengan helium dari model openMC, VSOP, dan MCNP adalah 125.881 cm, 125.804 cm, dan 126.116 cm, secara berurutan. Perbandingan antar software untuk analisis kritikalitas ini menunjukkan hasil yang baik dan bahwa model openMC yang dikembangkan dalam studi ini dapat digunakan untuk analisis pebble bed selanjutnya. Kata kunci: Heterogenitas Ganda, Reaktor Pebble Bed, Analisis Kritikalitas, Metode Monte Carlo, OpenMC, HTR-10 Keywords: Double heterogeneity Pebble bed reactor Criticality analysis Monte Carlo openMC © 2020 Jurnal Pengembangan Energi Nuklir. All rights reserved 1. INTRODUCTION As one of the advanced nuclear reactor designs, with a unique random geometrical composition, the capability to model and analyze pebble-bed high-temperature reactor core is important. In addition, as a moving fuel core, detailed modeling, and method to accommodate fuel movement in the core will be needed in further equilibrium and safety analysis. Currently, there are fourteen high- temperature gas-cooled reactors (HTGR) designs as reported by IAEA, in which half of it is pebble bed reactor (PBR) type, being developed in the world [1]. PBR design is usually chosen due to its strong passive safety feature, its cogeneration potential, and its capability to be optimized as a small modular reactor [2]. For that reason, as part of the national development program [3], a PBR design development called Reaktor Daya * Penulis korespondensi. E-mail: ikhsanmahfudin@gmail.com