How is a continuous chain reaction maintained within a moderator if it is not fissile material? Are the fissile materials mixed with the moderator or are they coalesced at the center of the surrounding moderator? If it is the latter, how would the surrounding moderator allow fissile material to absorb slower neutrons if these particles have left the fissile area? Whether the moderator is water, heavy water or liquid sodium can lost neutrons penetrate the moderated area or building material? If so, isn't this hazardous? Also, what degree of electromagnetic radiation does the moderator stop? If not all, is the remaining degree consistently released capable of harming workers or penetrating the building material and harming outsiders?