Isotope production and separation

The PSI accelerator facilities produce a large inventory of radionuclides, which have to be characterized and quantified as a demand from the Swiss nuclear safety authority. In 1997, a group was founded to investigate different components of the PSI accelerator complex to estimate their nuclide inventory. Many valuable and rare isotopes have been identified since then (such as 10Be, 32Si, 44Ti, 53Mn, 60Fe, 172Hf, 207Bi) and a project was started to extract long-lived rare isotopes from different matrix materials [1].

The main task of the Isotope and Target Chemistry group is the quantification, extraction and purification of valuable radionuclides from a broad spectrum of irradiated host materials. The involved chemistry relies on basic knowledge of element separation involving radiochemical techniques such as liquid-liquid extraction, ion chromatography, pyrochemistry or precipitation. Not only materials from the accelerator facilities at PSI itself, but also irradiated samples and materials activated outside PSI are being processed. The following examples should give an insight into our activities:
Based on different distribution coefficients of elements or chemical compounds in various media, the liquid-liquid extraction technique has been applied to extract 60Fe from irradiated Cu samples using HNO3/ethyl ether systems [2]. Similarly, 210Po may be extracted from liquid Pb-Bi alloy using molten NaOH at temperatures exceeding 300 °C (non-aqueous pyrometallurgical liquid-liquid extraction) [3].
The gradual elution of lanthanides for the separation of 171Tm.
Ion chromatography relies on distribution ratios between a solid stationary and a liquid mobile phase. This method is used to extract 7Be from cooling water of the SINQ spallation source, and additionally for purification [4]. The technique has also been used to separate neighbouring lanthanides – 171Tm and 163Ho from reactor irradiated Er or 147Pm from Nd [5] as well as 148Gd,146Sm and 154Dy from proton irradiated Ta/W. Specific resins and extractants must be used to achieve these challenging goals.

Images showing a) a sample of proton irradiated graphite before and b) its residue after burning it in oxygen at 1000 °C. The white residue represents oxidised spallation products originating from carbon irradiation (Li, B and Be)
Significant amounts of 10Be are produced during proton irradiation of the graphite wheel used at the PSI meson facility, [6]. In order to separate this nuclide from the carbon matrix, pyrolysis at 1000 °C in an oxygen stream has been successfully applied to extract ppm quantities (4 mg) of 10Be from 270 g of carbon, see Figure below. This technique also allows trapping significant amounts of 3H.

[1] Schumann, D., Stowasser, T., Dressler, R., Ayranov, M., Possibilities of preparation of exotic radionuclide samples at PSI for scientific investigations, Radiochim. Acta. 101, 501–508 (2013).
[2] Schumann, D., Neuhausen, J., Eikenberg, J., Ruethi, M., Wohlmuther, M., Kubik, P.W., Synal, H.-A., Alfimov, V., Korschinek, G., Rugel, G., et al., Radiochemical analysis of a copper beam dump irradiated with high-energetic protons, Radiochim. Acta. 97 123–131 (2009).
[3] Heinitz, S., Neuhausen, J., Schumann, D., Alkaline extraction of polonium from liquid lead bismuth eutectic, J. Nucl. Mater. 414 221–225 (2011).
[4] Schumann, D., Ayranov, M., Stowasser, T., Radiochemical separation of 7Be from the cooling water of the neutron spallation source SINQ at PSI, Radiochim. Acta 101, 509–514 (2013).
[5] Heinitz, S., Maugeri, E.A., Schumann, D., Dressler, R., Kivel, N., Guerrero, C., Koester, U., Tessler, M., Paul, M., Halfon, S., Production, separation and target preparation of 171Tm and 147Pm for neutron cross section measurements, Radiochimica Acta. (n.d.).
[6] Schumann, D., Neuhausen, J., Horn, S., Kubik, P.W., Günther-Leopold, I., Radiochemical separation and analytical determination of 10Be from proton-irradiated graphite targets, Radiochim. Acta. 96 31–34 (2008).