Complex sentence: For deeper penetration a source like 226 Radium is used that penetrate up to 328 yards (300 meters) can help find underground caves or just locations with lower density that would make tunnel construction hazardous.
Split into simpler sentences: For deeper penetration a source like 226 Radium is used that penetrates up to 328 yards (300 meters). Such instruments can help find underground caves or identify locations with lower density that would make tunnel construction hazardous.