The photo is sourced from news.mit.edu
This dynamics is to a great extent associated with re-launch of nuclear power units, which were shut down after the accident at Fukushima-1 NPP in 2011. According to IAEA, by 2013 regular electricity generation was suspended at all 48 reactors operating in Japan by the moment of the accident. This resulted in the radical changes in the power generation mix. In 2010 NPPs accounted for 25.3% of total electricity generation in Japan, and in 2014 their share shrank down to zero, while as the share of gas-fired CHPPs grew from 28.2% up to 42.4% respectively. Consequently, the LNG imports during the same period grew by 26% (from 192 thou tons per day in 2010 up to 242 thou tons per day in 2014).
However, in 2015, Japan commenced its program of re-launching nuclear reactors. As of today, 12 reactors of 11 GW net capacity resumed regular generation of electricity including the first and the second power units at Takahama NPP relaunched in August and September 2023 respectively. All twelve relaunched reactors belong to PWR category, where regular water is used both as coolant and as neutron moderator. In such reactors, the core heats the water, which then exchanges heat with the lower pressure system turning the water into steam. Then the steam activates the turbine.
Light boiling water reactors were subject to complete decommissioning including the reactors of Fukushima-1 NPP. Different from PWR, in the reactors of such type the steam is generated in the core (by heating water until it reaches boiling state) and then is channeled to the turbine for electricity generation. Japanese regulatory authorities decided to completely decommission 2 reactors of 10.1 GW total net capacity including 6 reactors of Fukushima-1 NPP, 4 reactors of Fukushima-2 NPP and 2 reactors of Hamaoka NPP.
The process of re-launching nuclear reactors in Japan is not finished yet: as of today, 5 reactors have received the permit for such re-launch, and 10 reactors are awaiting the final decision. In 2023, the Japanese Cabinet in one of its strategic documents announced the need for building new-generation reactors to substitute for the capacities subject to decommissioning.