Neodymium nuclides

Separation of Actinides from the Samples of Irradiated Nuclear Fuels. For the purpose of chemical measurements of burnup and other parameters such as accumulation of transuranium nuclides in irradiated nuclear fuels, an ion-exchange method has been developed to separate systematically the transuranium elements and some fission products selected for burnup monitors (16) Anion exchange was used in hydrochloric acid media to separate the groups of uranium, of neptunium and plutonium, and of the transplutonium elements. Then, cation and anion exchange are combined and applied to each of those groups for further separation and purification. Uranium, neptunium, plutonium, americium and curium can be separated quantitatively and systematically from a spent fuel specimen, as well as cesium and neodymium fission products. 

As an illustration of the way to disentangle the events that had taken place 2 billion years ago, the measurement of the neodymium isotopes (142-146,148, and 150) wiU be presented. It is important to know that neodymium remained in the rocks without migrating. In addition, it is advantageous that the content of natural neodymium in the minerals is small. This content could be determined since Nd is practically not formed in nuclear fission. As it results from the systematics of fractional fission yields (see Chap. 4 in Vol. 1), the (independent, direct) yield of Nd is very small. An alternative formation by the P decay of more neutron-rich nuclides of the same mass (i.e., isobars) is not possible because the direct precursor Ce is stable. Consequently, the content of the mineral in Nd reflects the amount of natural neodymium not produced by fission. Using the known isotopic composition of natural neodymium, the contributions of natural origin of all neodymium isotopes could be subtracted. This is illustrated in Table 57.1 (Columns 1-3). 

Trace quantities of such nuclides as Zr , Nd, Y , and Ru ° when added to a slurry of Th02 in water at 250°C are rapidly adsorbed on the oxide particles, leaving less than 10 % of the nuclides in solution. The tracer thus adsorbed cannot be eluted with hot dilute nitric or sulfuric acid. The adsorption of macroscopic amounts of uranium or neodymium on Th02 at 250°C is less for oxide fired to 1600°C than for 650°C-fired oxide. 

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