It is an extremist environmental website.
The article says that a 7.62mm mini-gun fires depleted uranium bullets, and the map shows the weapon has an effective range of approximately 1.5 miles /2.5 km. Simply put, the author of the articles does not seem to know the difference between 7.62mm and 20mm weapons.
The reference to a 'huge cache of radioactive plutonium' at LLNL is actually quite small. LLNL does not build weapons, their job was to conduct experiments to determine the properties and behaviors of plutonium and plutonium alloys. Plutonium has 7 different crystalline structures depending on temperature and pressure, and many alloys have even more complicated behaviors. The quantities required for this work are quite modest.
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