The 2011 earthquake and subsequent accident at the Fukushima Daiichi nuclear power plant compelled the policymakers in Japan to rethink the country’s previously-adopted energy policy which was based on nuclear power as the mainstay of Japan’s energy supply. At the same time, Japan’s commitment to reduce its greenhouse gas (GHG) emissions by 80 per cent below the 1990s levels by 2050 is faced with challenges, since a decreased dependence on nuclear power has already increased Japan’s use of fossil fuels for power generation at least in the short term. Against this backdrop, the choices Japan faces now include, among others, whether to focus more on cutting its energy demand or relying more on decarbonising on the supply side, how to generate electricity, and what types of technologies to use. How Japan addresses these concerns are critical for the country’s social, economic and environmental dimensions of sustainability. There is a growing interest in simplified tools that can provide an easy-to-understand chart to help understand the energy and emission options that are available for Japan. The Japan 2050 Low Carbon Navigator (Low Carbon Navigator) is such a quantitative tool which can support the policymaking process by engaging a wider audience in the energy and emissions debate. It is a user-friendly tool which lets the users to develop their own pathways combinations to achieve emissions reduction and ensure energy security, and see the impact using real scientific data. With uncertainties surrounding the future of Japan’s nuclear sector, a number of complex, unprecedented issues needed to be taken into account for developing the trajectories and making the assumptions within the Low Carbon Navigator model. These assumptions and trajectories under the nuclear sector are very different from the ones in the other energy supply sector. The purpose of this paper is to explain in details how the assumptions and trajectories under the nuclear sector have been developed and incorporated within the whole Low Carbon Navigator model. The paper is divided into several sections. Section 2 provides a review of the evolution of nuclear energy sector in Japan. Along with a brief history of the development of the Japanese nuclear sector, this section also covers the current challenges facing the country, and governmental policy changes that came forth as a consequence of the Fukushima accident. Section 3 focuses on the assumptions and trajectory setting of the nuclear sector in the Japan 2050 Low Carbon Navigator. It discusses the issues that have been taken into consideration in making the assumptions, relevant data sources, and explains the calculation procedures for this sector in the Low Carbon Navigator model. This section also provides several demonstration pathways generated by simulations under the Low Carbon Navigator. These examples demonstrate the impact of the nuclear sector in Japan’s future energy and emissions pathways. Section 4 concludes the paper with some explanation on what the Low Carbon Navigator can do, and what its limitations are.
Japan 2050 Low Carbon Navigator, nuclear energy, energy and emissions