Beijing is investing heavily in the modernization of Lop Nur, a sprawling military site where it long detonated atom bombs and thermonuclear warheads.

For years, U.S. government reports and independent experts have expressed vague concerns about the old base, Lop Nur. The reports point to possible preparations for year-round operations and a “lack of transparency.”

Now, however, waves of satellite images reveal that the military base has newly drilled boreholes — ideal for bottling up firestorms of deadly radiation from large nuclear blasts — as well as hundreds of other upgrades and expansions.