New attempts in search for superheavy elements in nature

~ ) Pergamon

Radiation Measurements, Vol. 25, Nos I--4, pp. 287-288, 1995 Copyright © 1995 Elsevier Science Lid Printed in Great Britain. All rights reserved 1350-4487/95 $9.50 + .00

13~4487(95)00094-1

N E W A T T E M P T S IN S E A R C H F O R S U P E R H E A V Y E L E M E N T S IN N A T U R E

E. J. LANGROCK,P. VATER,R. BRANDTand D. MOLZAHN Kernchemie,FB 14, Philipps-Universit/it,D-35032Marburg,Germany

ABSTRACT A new procedure in search for superheavy elements (SHE) in nature is suggested. SSNTD and crown-ethers will be employed in this work.

KEYWORDS Superheavy elements; SSNTD; uranium determination; crown-ethers; search in nature

The synthesis of a relatively long living (10-30 s) isotope of the element 106 (Lazarev et al., 1995) gives new hope in search for superheavy elements in nature. In this contribution we call SHE only elements around the double magic nucleus with Z = 114 and N = 184. Bearing in mind the very expensive chemical enrichment variants and the extremely expensive nfission- and a-emission- detection systems used in various attempts in the past (Flerov et al., 1981, Flerov et al., 1982, Flerov et al., 1983, Herrmann, 1979, Kratz, 1983) up to pilot plant scale (Flerov et al., 1979), there is obviously a need in applying cheaper techniques. The SSNTD technique has already been used in the search for SHE in nature (Lund et al., 1985) and in the search for SHE in the reaction 23SU + 2°spb (Lund et al., 1981). However, we are completely aware of the fact, that no theoretical estimation of SHE half-lives allows to be optimistic about the chances to find SHE in nature. But we know, how time-variant such theoretical estimations have been in the past. If we assume (Tolstov, 1979) a relative concentration of 10"2°g SHE per g sample material, we must use industrial plants for the first preeoncentration step. This is only possible by choosing a by-product fraction from a commercial industrial plant (e.g. metallurgical processes) based on special assumptions for the predicted chemical and physical properties. These fractions will be exposed to fission fragment-sensitive and a-sensitive SSNTD for a long time in a sandwich arrangement. Only in case of positive results we will determine the uranium content by activation analysis. If a remarkable positive residual amount of spontaneous fission activity remains, these hopeful samples will be dissolved and a crown-ether extraction for SHE enrichment will be carried out. 287

288

E.J. LANGROCK

et al.

Crown-ether separation was developed (Langroek et al., 1982) because the predicted ionic radii for SHE differ only in a narrow interval from 0.132 nm to 0.148 nm. All ions with ionic radii in this region can be captured by reagents with 18-crown-6 structures regardless of their chemical properties (nearly the same results for Ba, Sr, TI and Pb). The extraction with 18-crown-6 ether gives also good separation factors for elements with the mentioned radii from uranium. This is the main reason for using the crown-ether variant. After a total separation from uranium and other disturbing actinides one can use highest sensitive (and also very expensive) electronic detection arrangements. So we intent the following steps for this search: - foil exposition to SSNTD - uranium determination - crown-ether separation - high sensitive electronic detection After each step we can stop the process for a given sample. Thus, we try to minimize the costs for search for SHE. Obviously, the first steps can be carried out at many places with low costs. In this connection one should remember the fact that I. and W. Noddack ,1930, have worked for the discovery of the element rhenium and in the search for the element 43 in the nature. They investigated altogether 1600 terrestrial and extraterrestrial samples. In case of the search for SHE in nature this quantity is not nearly achieved and we conclude that it appears to us as necessary to continue this search.

REFERENCES Flerov, G.N., Yu.S. Korotkin, G.M. Ter-Akopyan, I. Zvara, Yu.Ts. Oganessian, A.G. Popeko, Yu.T. Chuburkov, L.P. Chelnokov, O.D. Maslov, V.I. Smirnov and R. Gerstenberger (1979). Results of the searches for superheavy nuclei in the Cheleken Penninsula geothermal waters. Z. Physik A - Atoms and Nuclei, 292, 43-48 Flerov, G.N. and G.M. Ter-Akopyan (1981). J. Pure andAppZ Chent, 53, 909 Flerov, G.N. et al. (1982). Radiokhim~a, 24, 782 Flerov, G.N. and G.M. Ter-Akopyan (1983). Rep. Prog. Phys., 46 Herrmann, G. (1979). Nature, 280, 543-579 Kratz, J.V. (1983). The search for superheavy elements. Radiochimica Acta, 32, 25 Langroek, E.J., T.V. Bazarkina and W. Czosnowska (1982). Procedure for selective solvent extraction of superheavy elements 113 ÷ and 1142÷ by use of crown-ethers. Radiochimica Acta, 3 0 , 229-231 Lazarev, Yu.A., et al. (1995). This volume Lund, T., D. Hirdes, H. Jungclas, R. Brandt, D. Molzahn, G. Tress, P. Vater, P. Lemmertz, R. Fall, H. Wollnik and H. G/iggeler (1981). Search for production of superheavy elements via "fusion after instantaneous fission" in the reaction 23SU + 2°spb. Z. Physik A - Atoms and Nuclei, 303, 115-121 Lund, T., G. Tress, E.U. Khan, D. Molzahn, P. Vater and R. Brandt (1985). Further attempts to isolate superheavy elements in the meteorite AUende. J. Radioanal.NucLChem., 93, 363-370 Noddaek, I. and W. Noddack (1930). Die H~iufigkeit der chemischen Elemente. Naturwissenschaften, Jahrg. 18, 757-764