DETERMINATION OF NB-93M AND NB-94M IN MEDIUM AND LOW-LEVEL RADIOACTIVE-WASTES

Nb-93m and Nb-94 are long-lived beta-gamma emitters which are produced mainly by neutron activation of the natural isotope Nb-93, that is pr esent in different quantities in the structural components of nuclear reactor vessels, specially those constructed of Inconel. Due to the lo ng half-life of these radionuclides and specially the extremely long h alf-life of Nb-94 (t(1/2) = 2.0 x 10(4) y), their presence in the deco ntamination 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 (93)mNb and N b-94 from the other beta-gamma emitters present in radioactive waste s treams, based on the selective precipitation of this element. The achi eved detection limits, in Bq, with 4 h of counting time are 8 times lo wer for Nb-94 and 5 times lower for Nb-93m than those obtained by dire ct gamma-ray spectrometry without radiochemical separation. (C) 1998 E lsevier Science Ltd; All rights reserved.