So as I'm interested in nuclear physics , I and a few other friends that work in the tech field we went to a now shutdown and in the process of decommissioning NPP. For various reasons I won't mention the stations name or location but those of you who know much about reactor types etc will probably have a clue where it was. So we walked through all the main parts , the reactor hall , controls room , support facilities , feedwater pumps, and the turbine generator or simply machine hall.Long story short , when at site I was amazed at the vast scale and monstrous size of everything starting from corridors and support buildings to the machine hall which was so big I had problems seeing the other end of it even from the middle of that hall. the reactor is the RBMK channel type. So here's the questions. 1) In the active zone I spent about 1 hour and that gave me about 2 uSv of dosage , if my calculations are correct that's not much overall although I would like to hear some feedback on this because it doesn't seem alot in terms of average annual dosage for a person but the time scale in which I got that is also very short so how does that add up? 2) The RBMK and the CANDU (according to wikipedia) are the only two reactors in the world that can refuel while in operation , I saw the huge and tall crane which is at the rector hall which does the refueling, while it's done nobody stays in the reactor hall but instead the operator of the crane watches through a very thick glass window in a room that is sealed off to prevent radiation exposure.the question is what is the most prevelent type of radiation near the fuel cassette when it's taken out of the core and how far it reaches from the source also it's penetrating power , because I got some contradictory opinions about that yesterday. 3) Question about dust. the reactor hall had a floor entirely out of stainless steel all corridors up to the hall had the same , is that done because such a floor is easier to clean (decontaminate) in case some radiation source dust have settled on it , like for example when refueling? 4) Radiation being part of the EM field needs a source , say for example that dust particles from a radioactive metal like uranium have scattered across a given territory like in Chernobyl , is it true that the radiation intensity is dependent on the size of the particle/s and their overall quantity in that given area ? so a larger single piece of radioactive material would have a larger amount of radiation emitted than a smaller piece of that same material. 5) the RBMK is said to have been a "good design" for the soviets because it gave them the chance of both producing civilian electricity and creating weapons grade plutonium at the same time hence the refueling while in operation. I read in "world-nuclear.org" that the only naturally fissile metal is uranium which is in the form of uranium ore which consists mostly of fertile U238 which cannot undergo a chain reaction itself.So the U235 does the chain reaction and the neutrons from that reaction hit the U238 which turns into the Pu239 which can then be used for weapons. Does it become weapons grade in the reactor or does it need to undergo more "purifying" elsewhere, like the uranium that is enriched ? and the last one for now , when they dig out the uranium if most of it's mass consists of the non fissile U238 using a gas centrifuge I read that they can separate the U238 from U235 simply because the U238 is heavier and in high rpm of the gas is located more to the outside , so they have to make the uranium in gaseous form before they can enrich it using this process ?