 A 2006 paper reports the levels of long lived radioisotopes in the trinitite.152Eu and 154Eu was mainly formed by the neutron activation of the europium in the soil, and the level of radioactivity for these isotopes is highest where the neutron dose to the soil was larger.Some of the 60Co was generated by activation of the cobalt in the soil, but some was also generated by the activation of the cobalt in the steel (100 foot) tower on which the bomb stood.