Any source for this significant claim?

The German ministry for Safety of nuclear energy (BASE) published an official statement that nuclear energy is not only unsafe, but also way too expensive:

https://www.base.bund.de/shareddocs/faktencheck/base/de/atomstrom-alternative-energiequellen-kosten.html

There are studies by the Deutsches Insitut für Wirtschaftsforschung (DIW, German Institute of Economic Research) that show significant higher costs per kWh than other power sources:

https://www.diw.de/de/diw_01.c.867887.de/publikationen/wochenberichte/2023_10_1/ausbau_von_kernkraftwerken_entbehrt_technischer_und_oekonomischer_grundlagen.html

https://www.diw.de/de/diw_01.c.670481.de/publikationen/wochenberichte/2019_30_1/zu_teuer_und_gefaehrlich__atomkraft_ist_keine_option_fuer_eine_klimafreundliche_energieversorgung.html

At my company, we work together with the Gesellschaft für Endlagerung (BGE). These guys are responsible to find safe long time storage for nuclear waste. Spoiler: as of now, there is no such thing as safe long time storage.

The German energy provider Enbw claims costs per kWh to be as high as 0.49€ for nuclear energy, which is ridiculous high. And they did not even factor in the high costs of safe long time storage!