London - The share of nuclear power in global gross electricity generation fell below 10% last year to the lowest in around four decades, an industry report showed on Wednesday.

Nuclear energy generated 2,653 terawatt hours of electricity last year, accounting for 9.8% of global generation - the lowest since the 1980s, the annual World Nuclear Industry Status Report (WNISR) showed.

Proponents of nuclear say as a low-carbon power source it could be vital in helping countries meet climate targets, but several plants around the world are coming to the end of their life expectancies and many new ones have faced delays.

The most nuclear power in the world is generated in the United States, followed by China.

As of mid-2022, 411 reactors were operating in 33 countries, four less than a year earlier and 27 below a 2002 peak of 438.

The slow pace of new projects coming on stream has meant the average age of reactors is around 31 years old.

Out of 53 reactors under construction currently, at least half of the projects are delayed. Five new units became operational in the first half of this year, while eight closed last year.

Global investment in new nuclear construction projects last year was around $24 billion, accounting for 6.5% of total investment of $366 billion in non-hydro renewables projects.

Nuclear power is also losing ground to renewables in terms of cost as reactors are increasingly seen as less economical and slower to build.

The levelised cost of energy - which compares the total lifetime cost of building and running a plant to lifetime output - fell to $36 per megawatt hour (MWh) last year for solar photovoltaic from $359/MWh in 2009, while the cost for wind fell to $38/MWh from $135/MWh, the report showed.

However, nuclear power costs rose by 36% last year to $167/MWh from $123/MWh in 2009.

(Reporting by Nina Chestney Editing by Mark Potter)