Nuker can be very resource intensive if not used correctly, or if used on lower end machines.
Firstly, I would ensure that the lag spikes aren't caused by RAM. If able, allocate more RAM to Aristois and see if the problem is fixed.
Besides this, to use nuker efficiently you either need to be in creative or have good tools (diamond eff 4 or higher) in survival. To prevent crashes, toggle the mod on and off frequently (couple seconds at a time), lower the range, or disable "nuke all blocks" and only add certain blocks at a time, so it won't try nuking everything at once. To prevent lag, I would only do small areas at a time. It's normal to experience slight FPS drop when nuking several blocks all around the player, especially on lower end machines.