Дисперсность, морфология и элементный состав аэрозольных частиц на производстве смешанного нитридного уран‑плутониевого топлива

Abstract

Purpose: Study of physical and chemical properties of radioactive aerosols formed on the fabrication of mixed nitride uranium-plutonium (MNUP) fuel.
 Material and methods: The following impactors were utilized for activity particle-size distribution analysis: AIP-2, PHRT, IRAM-2-4I (SRC FMBC), Andersen cascade impactor (Copley Scientific, UK), SKC Sioutas (SKC inc., USA). Scanning electron microscope (SEM) Tescan LYRA-3 equipped the X-ray microanalyzer X-max 80 (Oxford Instruments) was used for study of morphological characteristics of aerosol particles. Secondary ion-mass spectrometer Cameca IMS-1280 and track analysis were used for search of particles containing the uranium and plutonium radionuclides. 
 Results: Values of AMAD (Σa) vary from 12 µm till 30 µm, for 239Pu – from 14 till 27 µm. Lowest AMAD values (0.4–2.5 µm for 239Pu) were found in the repair area near the glove box of synthesis and sintering. The samples contain a much larger number of uranium-containing particles, which is likely due to a larger mass fraction of uranium oxide compared with plutonium dioxide in the initial mixture of reagents. Elemental composition of aerosol particles includes U (63–86 %), Pu (5–10 %) and О (9–47 %), Fe – in some samples till 32 %. Other elements like Nа, S, N, Р are contained in rather lowest amounts not exceeding 1–8 %. Only one nitrogen-containing particle was found (3 % of N).
 Conclusion: Coarse fraction of radioactive aerosols makes a major contribution in activity concentration in air of the operator zone which is driven by such operations as pressing and crushing. Aerosol particles are presented as individual particles or dense aggregates by size of 0,2– 2 µm and also as conglomerates by size 0,5–4 µm consisting of oxides (or carbides) of silicon, iron, calcium, etc. containing inclusions (200–400 nm) or individual particles (20–200 nm) of mixed U-Pu oxide or uranium oxide on the surface of conglomerate as well aslocated in the near-surface layers inside.