Energy experts say all carbon-based electrical power generation on the planet could be replaced by a few thousand new zero-emission nuclear reactors.

Judge as of April 2020. True: published estimates by energy experts (analysts, academics, agencies) state that replacing global fossil-fuel electricity generation would take on the order of a few thousand (roughly 2,000–5,000) large nuclear reactors, and the arithmetic (global fossil electricity ~16,000–17,000 TWh/yr vs ~8 TWh/yr per 1 GW reactor) supports that. Mostly true: experts' estimates are somewhat outside 'a few thousand' (e.g., up to ~6,000–7,000) or the attribution to experts is loose but the figure is sound. Mixed: estimates vary widely and only some support the figure. Mostly false: the needed number is far larger (e.g., well over 10,000) or no experts make this claim, but the order of magnitude is not wildly off. False: the figure is wrong by an order of magnitude or more.

Set before the research began.

1. E1 The Incredible Shrinking Nuclear Offset to Climate Change Pulitzer Center · 2 February 2017

   “More recently, James Hansen suggested that nuclear energy could replace all fossil fuel electricity by 2050 if the industry built 61 reactors per year. That total—2,135 reactors in 35 years—dwarfs the 667 reactors”

2. E2 Potential for Worldwide Displacement of Fossil-Fuel Electricity by Nuclear Energy in Three Decades Based on Extrapolation of Regional Deployment Data PubMed Central (National Library of Medicine, NIH) · 13 May 2015

   “our modelling estimates that the global share of fossil-fuel-derived electricity could be replaced within 25–34 years.”

3. E3 Potential for Worldwide Displacement of Fossil-Fuel Electricity by Nuclear Energy in Three Decades Based on Extrapolation of Regional Deployment Data PubMed Central (National Library of Medicine, NIH) · 13 May 2015

   “Fossil fuel electricity and all current nuclear electricity (2015 projection) [18] | 1.77 x 1013 kWh/y”

4. E4 [PDF] nuclear power and climate: - why nukes can't save the planet Nuclear Information and Resource Service (NIRS) · June 2014

   “Major studies (from MIT, Commission on Energy Policy, and International Atomic Energy Agency, for example) agree that about 1,500-2,000 large new atomic reactors would have to be built worldwide for nuclear power to make any meaningful dent in greenhouse emissions”

E1 reports James Hansen's estimate that about 2,135 reactors would replace all fossil-fuel electricity, which falls within 'a few thousand'. E3 puts global fossil-plus-nuclear electricity at about 17,700 TWh/yr. At roughly 8 TWh/yr per 1 GW reactor, that comes to about 2,000 reactors, so the arithmetic supports the figure. E4 cites MIT, IAEA and other studies giving 1,500–2,000 reactors, but those figures are for a 'meaningful dent' in emissions, not full replacement. The figure holds up. The evidence gives one reactor-count estimate for full replacement (Hansen's, in E1), and an academic modelling study (E2) finds that full replacement by nuclear is possible but gives a timescale rather than a reactor count, so the attribution to 'energy experts' is somewhat loose.