Memory Palace!

It should be known that the Uranium Element and Uranium-235 were not the same thing.

As a chemical element, uranium belonged to the actinide series on the Periodic Table of Elements. Its chemical symbol was U, and its atomic number was 92. Because uranium was slightly radioactive, all its isotopes were unstable, causing it to exist in nature in three forms: Uranium-238, Uranium-235, and Uranium-234.

Of these three forms, only Uranium-235 could undergo spontaneous fission. In other words, only Uranium-235 could truly serve as raw material for nuclear weapons.

And how much Uranium-235 was there? Compared with Uranium-238's 99.2739% to 99.2752% abundance, Uranium-235 accounted for only around 0.7198% to 0.7202%.

In other words, less than 0.1%, less than one-thousandth.

This was also the greatest difficulty in nuclear weapon research and manufacturing plans—how could Uranium-235 be separated from Uranium-238 and extracted on its own? Only now did purification truly mean purification: actually handling the nuclear raw material Uranium-235, rather than its brother, Uranium-238.

Uranium-235 and Uranium-238 were isotopes, after all. Their physical and chemical properties were nearly identical. The only difference was perhaps that one nucleus contained 143 neutrons, while the other had 146.

How to use that difference, one that existed only in the microscopic world, to separate and purify Uranium-235 was the true obstacle to be addressed in the fourth stage of the nuclear weapon research and manufacturing plan.

So, what should he do? Richard stood in the Uranium Element purification sector, thinking. His brows gradually furrowed, as if he were struggling to recall memories stored in his brain.

After trying to remember for a long while, his brows slowly relaxed again. Somewhat relieved, he said, "Hmm, looks like I forgot."

Yes, he had forgotten.

At the most critical stage of the plan, he had forgotten what to do.