 Overall , europium is overshadowed by caesium @-@ 137 and strontium @-@ 90 as a radiation hazard , and by samarium and others as a neutron poison . 
 Overall , europium is overshadowed by caesium @-@ 137 and strontium @-@ 90 as a radiation hazard , and by samarium and others as a neutron poison . 
Overall , europium is overshadowed by caesium @-@ 137 and strontium @-@ 90 as a radiation hazard , and by samarium and others as a neutron poison .