237 Np analytical method using 239 Np tracers and application to a contaminated nuclear disposal facility

• Published in: Journal of environmental radioactivity 2017-06, Vol.172 (C), p.89-95
• Main Authors: Snow, Mathew S, Morrison, Samuel S, Clark, Sue B, Olson, John E, Watrous, Matthew G
• Format: Article
• Language: English
• Subjects: Idaho; MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE WASTES FROM NUCLEAR FACILITIES; Neptunium - analysis; Radiation Monitoring - methods; Radioactive Waste - analysis; Soil Pollutants, Radioactive - analysis
• ISSN: 0265-931X; 1879-1700
• DOI: 10.1016/j.jenvrad.2017.02.018

Environmental Np analyses are challenged by low Np concentrations and lack of an available yield tracer; we report a rapid, inexpensive Np analytical approach employing the short lived Np (t  = 2.3 days) as a chemical yield tracer followed by Np quantification using inductively coupled plasma-mass spectrometry. Np tracer is obtained via separation from a Am stock solution and standardized using gamma spectrometry immediately prior to sample processing. Rapid digestions using a commercial, 900 W "Walmart" microwave and Parr microwave vessels result in 99.8 ± 0.1% digestion yields, while chromatographic separations enable Np/U separation factors on the order of 10 and total Np yields of 95 ± 4% (2σ). Application of this method to legacy soil samples surrounding a radioactive disposal facility (the Subsurface Disposal Area at Idaho National Laboratory) reveal the presence of low level Np contamination within 600 m of this site, with maximum Np concentrations on the order of 10 times greater than nuclear weapons testing fallout levels.