Misc: What type of accident happened at Chernobyl in the USSR in 1986?

Questions

Located in northern Arizona, established as a national monument in 1908 & as a national park in 1919?

Longest reigning empress of Russia?

Longest river of Asia, in China, about 5526 km (about 3434 mi) in length?

Lunar revolutionary who hated the handle `Why not'?

Machine that decreases the volume & increases the pressure of a quantity of air by mechanical means?