Xray emission from the rectifier happens only during electron bombardment of the plate, which occurs only during the positive-going half cycle, and the max voltage is half the PIV value. The only real concern over Xrays was in color sets where 25KV on the pic tube anode was typical, and that hype was hugely overblown (IMHO). Heck, if Xrays were any danger i oughta have been thoroughly cooked many years ago.
