Mihama is a 826 MW nuclear power station in Fukui, Japan. It is operated by Kansai. Based on its capacity (estimated), it can supply roughly 1.9 million homes (estimated). It ranks #117 of 692 Japan power plants by installed capacity. Commissioned in 1970, it is around 56 years old — an older, legacy facility. As a non-combustion source, it has no direct CO₂ emissions from generation. In context, nuclear supplies about 9.1% of Japan's electricity; the national grid averages 477 gCO₂/kWh (32.7% low-carbon) (2025).
Plant data: WRI Global Power Plant Database (CC BY 4.0), id WRI1000682.
Data status
Known data
Calculated from dataset
Not available
Known, modelled and calculated values are kept separate. Missing fields are shown as unavailable.
Data provenance
Source of the capacity and fuel values:
capacity: GEM · 2026 · L100000500155; fuel: WRI GPPD
In context: how this plant compares
At 826 MW, Mihama is below the median nuclear plant in Japan (2,070 MW). Technically it is described as fast breeder reactor. Nuclear plants split uranium to raise steam with no direct CO₂; they run as steady baseload with very high capacity factors and the longest operating lifetimes of any thermal plant.
Capacity comparison computed from the WRI Global Power Plant Database; fuel-type context is general engineering background.
Key facts
- Share of Japan nuclear capacity
- 1.4% of 58,491 MW across 24 plants in this dataset
- Age among peers
- 2 of 17 dated nuclear plants in Japan are older
Calculated from the capacity and generation records in this dataset (WRI Global Power Plant Database (CC BY 4.0)).
Capacity vs largest nuclear plants in Japan
Installed capacity (MW), WRI Global Power Plant Database (CC BY 4.0).
Owner
Operated by Kansai. All plants by this company →
Local climate & thermal context
This nuclear plant uses heat from nuclear fission to raise steam for a turbine-generator. It sits in a humid subtropical climate (Köppen Cfa) — Northern Hemisphere, latitude 35.7°N — which shapes how much energy it can produce and how its output varies through the year.
Monthly mean temperature
Heating degree-days here run 2% below the median power plant in this dataset — a proxy for how much extra energy heated equipment must replace through its surfaces in winter.
Climate heat-demand index: 49/100 — this site sits in the mid third of the power plants we cover by heating degree-days.
Climate normals: WorldClim 2.1 (1970–2000 monthly normals, 10 arc-min, CC BY 4.0); zone: Köppen-Geiger world climate classification (Kottek et al. 2006, 0.5° grid). Degree-days & heat-demand index computed by PowerAtlas — a modelled heat-demand proxy, not a measured site figure.
Site climate & environmental severity
This site sits in a corrosive environment (estimated ISO 9223 class C4 — High), with humidity / wetness the leading environmental stress.
Indicative estimate via the ISO 9223:2012 informative method (atmospheric corrosivity from temperature, time-of-wetness and airborne salinity), using WorldClim climate normals, the Köppen-Geiger class and coast distance. Indicative, not a measured corrosion rate.
How it compares & nearby plants
The #21 largest nuclear power plant of 24 in Japan by capacity.
Japan has 24 nuclear power plants in this dataset, together about 58,491 MW of capacity.
Nearby power plants
- Tsuruga · Nuclear · 1,160 MW · Fukui
- Tsuruga Green power station · Biomass · 37 MW · Fukui
- Tsuruga power station · Coal · 1,200 MW · Fukui
- Ohi · Nuclear · 4,710 MW · Fukui
- Yokoyama · Hydro · 70 MW · Gifu
- Takahama · Nuclear · 3,392 MW · Kyoto
Location
Coordinates 35.7024, 135.9634 from WRI Global Power Plant Database (CC BY 4.0). View on OpenStreetMap.
Frequently asked questions
What type of power plant is Mihama?
Mihama is a 826 MW nuclear power plant in Fukui, Japan, commissioned in 1970.
Who operates Mihama?
Mihama is operated by Kansai.