Sorry, but when you deplete uranium of the fissionable U-235 isotope, to enrich other mixes of isotopes of the metal, what is left is still DU -- either the initial metal refining or reprocessing of fuel rods. It is a considerably purer sample of U-238 than what you start with.
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The byproduct of enrichment, called depleted uranium or DU, contains less than one third as much U-235 and U-234 as natural uranium.
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Natural uranium metal contains about 0.71 percent U-235, 99.28 percent U-238, and about 0.0054 percent U-234. In order to produce enriched uranium, the process of isotope separation removes a substantial portion of the U-235 for use in nuclear power, weapons, or other uses. The remainder, depleted uranium, contains only 0.2 percent to 0.4 percent U-235. Because natural uranium begins with such a low percentage of U-235, enrichment produces large quantities of depleted uranium. For example, producing 1 kg of five percent enriched uranium requires 11.8 kg of natural uranium, and leaves about 10.8 kg of depleted uranium with only 0.3 percent U-235 remaining.
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And that was just Wikipedia, FWIW. Wanna dig deeper? Sundry links
this page.