The number of nuclear reactor units operating globally is at a 30 year low, while new plants struggle for investment, an industry report said on Thursday.

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.

Some 408 nuclear reactors were in operation in 31 countries as of July 2020, a decline of 9 units from mid-2019 and 30 fewer than the 2002 peak of 438, the annual World Nuclear Industry Status Report (WNISR) showed.

The slow pace of new projects coming on stream also increased the overall age of the global fleet to around 31 years old.

Of the 52 new plants being built globally at least 33 are behind schedule, while not a single new project came online in the first half of 2020, the report said.

New projects were struggling to secure finance amid competition from renewables with reported investment decisions for the construction of new nuclear plants at around $31 billion in 2019, around 1 tenth that of wind and solar, the report said.

This year nuclear plant operators have also been dealt a blow by the coronavirus pandemic with lockdowns on households and business cutting electricity demand and reducing power prices in many countries.

Electricity consumption in some regions is not likely to reach pre-pandemic levels for many months, if not years the report said, impacting operators' finances.

Low power prices are also likely to reduce the imperative to invest in new plants, "therefore the extent to which new power plants are built may to a large degree depend on government stimulus packages," the report said.