Complex sentence: Japan presently receives a large amount of funding for the neutrino activities, such as the T2K experiment, so it is disfavored although 20 huge caverns with access tunnels have already been constructed in Japan for hydroelectric power plants (e.g. the Kannagawa Hydropower Plant).
Split into simpler sentences: Japan presently receives a large amount of funding for the neutrino activities, such as the T2K experiment, so it is disfavored. Although, 20 huge caverns with access tunnels have already been constructed in Japan for hydroelectric power plants (e.g. the Kannagawa Hydropower Plant).