[ RadSafe ] pyrophoric uranium considered nonessential

[Mercado, Don]

So from your source:

"Uranium is a dense, lustrous metal that resembles iron. It is also 
ductile and malleable. In air it tarnishes quickly, and a freshly 
exposed surface becomes coated with a layer of dark oxide. When finely 
divided, the metal burns spontaneously in air (it is pyrophoric)."

And from Alan's MSDS:

"Metal powders, while generally regarded as non-combustible, may burn
when 
metal is finely divided and energy input is high."

So apparently the properties are not that well known as you state. My
bet is that the MSDS is more current than your text, and since my U
powder and DU doesn't burst into flames, I'd trust the MSDS first.