I would advise Basic first of all. Its quick and dirty and the easiest to learn. It should be sufficient for your studies. Alternatively, Pascal is what many professional first learn, as it is very clean and you do not pcik up any nasty habbits from it.
However, you must remember that Basic...
Not a good idea. Any plastic components will degrade if placed in the high rad field. You also have problems of replacing it. However, you presumably have a vent plant attached so you could mount it in the downstream ducting, away from the radiation. Another trick is to draw a sample of air from...