Degree of depletion

Naturally occurring uranium consists of about 0.7% of the lighter isotope with the mass number 235 ( ²³⁵ U) and 99.3% of the heavier isotope with the mass number 238 ( ²³⁸ U). In order to be able to use uranium as a nuclear fuel in reactors, most reactor types must first be enriched .

The two isotopes are partially separated from each other in an enrichment facility. The result is a product with an increased share of ²³⁵ U compared to the initial value of 0.7% . For reasons of mass conservation , a uranium fraction (also called tails ) is inevitably produced in which the ²³⁵ U is present in a lower concentration than in the initial state. This concentration value is called the degree of depletion . It is determined by the current price for natural uranium on the world market and is mostly 0.2 to 0.3% today. An even greater reduction in the ²³⁵ U content, which would be technically easily possible, is currently not worthwhile for economic reasons.