Salimy et al. / Malaysian Journal of Fundamental and Applied Sciences Vol. 16, No. 2 (2020) 135-138 135 The assessment of nuclear hydrogen cogeneration system (NHCS) for CO 2 conversion to urea fertilizer Djati Hoesen Salimy * , Sriyono, Elfrida Saragi, Abdul Hafid Center for Technology and Safety of Nuclear Reactor, BATAN, Kawasan Puspiptek Gd.80, Serpong, Tangerang Selatan 15310, Indonesia. Corresponding author: djatihs@batan.go.id Article history Received 31 December 2018 Revised 12 March 2019 Accepted 9 July 2019 Published Online 15 April 2020 Abstract This paper reviews the application of a nuclear hydrogen cogeneration system (NHCS) for conversion of carbon dioxide (CO 2 ) to urea fertilizer. The NHCS is powered by high temperature gas cooled reactor (HTGR)with 2x600 MWt which is sufficient to produce hydrogen and heat energy to convert CO 2 from coal-fired power plants with a power of 90 MWe to urea fertilizer of 1725 tons per day. As a source CO 2 , a coal-fired power plant is built near NHCS. Compared to conventional fertilizer plant, the NHCS application can save natural gas by 21.25x10 6 MMBTU/year, with a potential reduction in CO 2 emission rate of 1.66x10 6 tons/year. Besides, there is still nuclear heat remaining at about 425.65 MWt which is equivalent to 140.46 MWe of electricity, and 90 MWe of electricity from coal-fired power plants that can be connected to electric grid. The paper also discusses the significance of the combination of NHCS and the technology of CO 2 conversion which is expected to play an important role in the industry in the future as an environmentally friendly approach. Keywords: NHCS, CO 2 conversion, urea fertilizer, nuclear heat © 2020 Penerbit UTM Press. All rights reserved INTRODUCTION One way to reduce CO2 emissions is to turn it into a product that has added value. In addition, CO2 can be used as an abundant and renewable raw material for various petrochemical and synthetic fuels. CO2 has advantages over other C1 toxic materials such as carbon monoxide and phosphagen [1]. A study indicates that the production of chemicals from CO2 can significantly influence mitigation of global CO2 emissions because the amount of CO2 used is quite large [2]. To produce chemical products from CO2, large amounts of hydrogen are needed. Water splitting by utilizing high-temperature gas cooled reactors (HTGR) is an interesting technology to supply hydrogen for CO2 conversion [3, 4]. HTGR is a reactor that operate at high temperature (~1000 O C). This reactor is dedicated not only for electricity generation, but also to utilize high temperature heat energy for industries. Water splitting by utilizing HTGR is the process of thermochemical decomposition of water to produce hydrogen and oxygen which occurs at high temperatures [5]. Heat energy coming out from HTGR can serve as heat energy source to run the process. Among the nuclear thermochemical process, a process with iodine-sulfur cycle is the most advanced. The process was originally developed by General Atomics in America in the 1970s, later adopted and developed by several countries such as Japan, Germany, China, France, and South Korea. Nuclear hydrogen cogeneration system (NHCS) is a system that has capability to supply hydrogen and high temperature thermal energy. NHCS can then play an important role in the application of nuclear energy to industrial processes. From the environmental side, expanding the use of nuclear energy not only for electricity but also for industry, aims to reduce CO2 emissions in the atmosphere. If NHCS can be combined with CO2 conversion technology, it is hoped that significant CO2 emissions savings will be obtained. One of the important uses of NHCS for CO2 conversion is the production of urea fertilizer. Urea production is a process that takes place at high temperatures which consume large amounts of natural gas, both as raw materials, as well as source for process heat, and utilities. The study of NHCS applications and CO2 conversion can save large amounts of natural gas which has a significant effect on reducing CO2 emissions. This paper reviews previous studies related to the application of the NHCS for the conversion of CO2 to urea. The future limitation of natural gas can be a threat to the sustainability of the urea fertilizer plant if it only relies on conventional processes made from natural gas. For this reason, it is necessary to study various alternative processes for producing urea fertilizer with raw materials other than natural gas. Studies in America indicate that urea fertilizer can be made with coal or water [11]. In principle, the key technology for urea fertilizer plants is the production of hydrogen in the ammonia plant unit. Because hydrogen can be produced from coal (through coal gasification processes), or with water raw materials (thermochemical processes), it means that natural gas as a raw material for fertilizer plants can also be replaced with other materials that can produce hydrogen. This review provides important input to the stakeholders in formulating policies of nuclear energy development in Indonesia, particularly the development of the use of high-temperature nuclear reactor in the future. NHCS FOR CO2 CONVERSION Nuclear hydrogen cogeneration Cogeneration is a way to use a single source of energy efficiently to produce power and useful thermal energy [7]. This system is a very efficient, clean, and reliable approach to generate power and thermal energy from a single fuel source [8]. Typically, cogeneration plants recover “waste heat” that is otherwise discarded from conventional RESEARCH ARTICLE