Determination of 93mNb and 94mNb in medium and low level radioactive wastes

93mNb and 94Nb are long-lived β–γ emitters which are produced mainly by neutron activation of the natural isotope 93Nb, that is present in different quantities in the structural components of nuclear reactor vessels, specially those constructed of Inconel. Due to the long half-life of these radionuclides and specially the extremely long half-life of 94Nb (t1/2=2.0×104 y), their presence in the decontamination and dismantling wastes can affect their classification as low-level and short-lived radioactive waste material. The aim of this paper is to propose a radiochemical separation method of 93mNb and 94Nb from the other β–γ emitters present in radioactive waste streams, based on the selective precipitation of this element. The achieved detection limits, in Bq, with 4 h of counting time are 8 times lower for 94Nb and 5 times lower for 93mNb than those obtained by direct γ-ray spectrometry without radiochemical separation.