Trying to assassinate non-existing nuclear scientists? Yeah that's hard to imagine. Israel already has access to pretty advanced nuclear technology it is not actively trying to develop one like Iran is.
Israel seems to be trying to buy time before the inevitable happens. Not sure if it's good strategy to keep assassinating scientists when you're going to need every ounce of International support you can muster when the Iranians rain down on you with their nukes.
None because Israel is not actively attempting to advance its nuclear technology capabilities. Because it already has access to advanced nuclear technology.