So i want to know more about nuclear weapon tests, mostly because the whole topic of nuclear weapons fascinates me.
Wasn't building nuclear explosive devices really expensive? If so, why were so many tests carried out? Who had the authority to:
propose those tests
approve them
carry out those tests
How did the process look like from start -planning the test - to finish - cleanup etc. -
Where the bombs used in those test specifically designed/ordered to built or did they sometimes just pick one that was in their arsenal?
Regarding to the question before: I've read that in the USA e.g. missle Silos had not only the task of delivering the retaliation strike, storage of weapons and so on but ofcourse also to make sure the weapons weren't manipulated. How was it made sure that nuclear weapons weren't manipulated in production? How would the military know that brand new nuclear weapons delivered to them would really well explode? Did they sometimest just pick one weapon from their arsenal to test if they were working?
It changed a bit over time in the USA, but the general procedure for most of the Cold War it was the job of the Atomic Energy Commission or its successor agencies (ERDA, Department of Energy) to propose and carry out these tests. For some test series they received help from the military (notably those that required them to be somewhere other than the Nevada Test Site, but even there they had logistics help on some of them). The President gave the final approval of the test series, in part because the President had to approve the expenditure of fissile material (the nuclear fuel in the weapons). In the early days the President might actually veto a proposal (Eisenhower would sometimes question them) but it eventually became very routine (especially after the testing went underground).
In the earlier days it took a lot more logistics work; the whole thing wasn't yet routine. So at Operation Crossroads (1946) there were literally thousands of people involved in testing two bombs. The creation of the Nevada Test Site reduced the overhead a lot, because it didn't require moving people around all those islands. When the testing went underground (post-1962) it became very routine — dig a hole, plant the bomb and the diagnostic instruments, set it off.
Most of the tests did not require extensive cleanup and remediation. There were some that did — the Marshall Islands required a lot of remediation, for example (scraping off top-soil and burying it in a pit). The grunt work was done by the US Army though I believe the planning was done by the AEC.
Usually the tests were specifically done to either test new design ideas, to answer physical questions, or to determine useful information about the effects of the weapons. Sometimes stockpile weapons were chosen more or less at random as a form of quality control (making sure they actually work as they were expected to — there were a few models that were discovered to in fact be "duds" this way).