Nuclear fuel is very energy dense, so very little of it is...

Nuclear fuel is very energy dense, so very little of it is required to produce immense amounts of electricity – especially when compared to other energy sources. As a result, a correspondingly small amount of waste is produced. On average, the waste from a reactor supplying a person’s electricity needs for a year would be about the size of a brick. Only 5 grams of this is high-level waste – about the same weight as a sheet of paper.

The generation of electricity from a typical 1,000-megawatt nuclear power station, which would supply the needs of more than a million people, produces only three cubic metres of vitrified high-level waste per year, if the used fuel is recycled. In comparison, a 1,000-megawatt coal-fired power station produces approximately 300,000 tonnes of ash and more than 6 million tonnes of carbon dioxide, every year.

https://world-nuclear.org/nuclear-essentials/what-is-nuclear-waste-and-what-do-we-do-with-it