Particle properties of a nitric solution of cerium nitrate as a substitute of Pu-nitrate

J. AerosolScL,

Vol. 17, No. 3. pp. 592- 596, 1986.

0021 8502186$3.00+0.00 Pergamon Journals Ltd.

Printedin Great Britain.

PARTICLE PROPERTIES OF A NITRIC SOLUTION OF CERIUM NITRATE AS A SUBSTITUTE OF Pu-NITRATE H. D. SEEHARS, D. HOCHRAINERand M. SP1EKERMANN Fraunhofer-lnstitut fiir U m w e l t c h e m i e und C)kotoxikologie, Schmallenberg-Grafschafl, F'R.G.

OBJECTIVE OF THE INVESTIGATIONS In the Federal Republic of Germany nitric solutions of plutonium nitrate are transported on the road. At the worst, accidents may lead to fire, the destruction of the transport container and the release of the contents in the form of aerosols. To estimate the inhalation risk, especially the deposition of inhaled particles in the human lung, it is important to know something about the particle properties such as size, morphology and solubility (soluble Punitrate, insoluble Pu-oxide), which is dependent on the residence time and the temperature near the fire. rJC motor PO..... pp~¥~

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Particle properties of a nitric solution

Fig. 3. Scanning electron micrographs of cerium containing particles (Dae -----3.0 pm). Residence time in the chamber = 300 s. (a) V = 5000; temperature = 110°C; (b) V = 10,000; temperature = 250°C.

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Particle properties of a nitric solution

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EXPERIMENTS Thermogravimetric analysis was applied to obtain some information about the thermal decomposition of the bulk solution. For aerosol studies a nitric solution of cerium nitrate, used as a substitute for Pu, was nebulized in a glass nebulizer, and the droplets were transferred to a heatable aerosol chamber (Fig. 1), where they were exposed to different temperatures up to 250°C during residence times o f 5--15 min. Afterwards the particles were fractionated in an aerosol quartz centrifuge according to their aerodynamic diameter.

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H.D. SEEHARS et al.

RESULTS Thermogravimetric analysis (Fig. 2) indicated that the nitrate was decomposed into the oxide at temperatures between 170 and 225°C, The particles were deposited in the centrifuge, independent of their diameter, mostly as droplets at 110°C and as nearly spherical, solid particles with a very rough surface at 250°C (Fig. 3). LAMMA spectra (Fig. 4) of the particles reveal that the negative ions of all particles, including those exposed to 250°C, contain nitrate and probably oxide, too. Most of the particles show a gradient of the nitrate contents from the particle surface to deeper layers.