Determination of Mo-93 inventory in irradiated BWR tie plate using triple quadrupole ICP-MS

The inventory of radionuclides is a crucial input parameter for the safety assessment of irradiated metal waste. Among the radionuclides, Mo-93 is remarkable radionuclide owing to its long half-life (4,000 years) and poor sorptive property (anionic species). A method for determining Mo-93 by measuring characteristic X-rays was proposed previously; however, this method requires complex sequential and/or chromatographic separation of Mo-93. In the present study, triple quadrupole inductively coupled plasma mass spectrometry (ICP-MS/MS)—a leading-edge method—was used to determine the inventory of Mo-93 in an irradiated boiling water reactor (BWR) tie plate (stainless steel) for the first time. Furthermore, an activation calculation for Mo-93 was conducted using ORIGEN2. The results indicated that the inventory of Mo-93 in the BWR tie plate was 690 ± 83 Bq/g. This study demonstrates that triple quadrupole ICP-MS allows the simple quantitative analysis of Mo-93 in irradiated stainless steel without complex chemical separation.