Chemical effects of nuclear reactions

Chemical effects of nuclear reactions were first observed by Szilard and Chalmers in 1934 when irradiating ethyl iodide with neutrons. They found several chemical species containing 1 that are produced by the chemical effects of the nuclear reaction l(n, y) 2 1. In the following years, chemical effects of radioactive decay were observed in gaseous compounds, liquids and solids. 

Chemical effects of nuclear reactions in gases are preferably investigated by use of mass spectrometry, for example ... 

The chemical effects of nuclear reactions in liquids have been investigated in great detail with alkyl halides. The first example was studied by Szilard and Chalmers in 1934. They irradiated ethyl iodide with neutrons and were able to extract about half of the 1 produced by the nuclear reaction I(n, into an aqueous phase. Similar results are obtained in the case of (d, p), (n, 2n) and (y, n) reactions and of other alkyl or aryl halides appreciable amounts of the radioisotopes of iodine or other halogens obtained by these reaction can be extracted into aqueous solutions. 

For the investigation of hot -atom induced reactions the teehnique of scavenging is often applied. In this method, small amounts of reactive eompounds (scavengers) are added which react preferentially with atoms or radicals produced by the chemical effects of nuclear reactions. Whereas hot reactions are not influenced by the presence of scavengers, scavengers are highly selective in the range of thermal reae-tions. 

Chemical effects of nuclear reactions do not only cause rupture of chemical bonds, they also lead to formation of new chemical bonds, a result that may be used for preparation of labelled compounds. Recoil labelling and self-labelling both involve radiation-induced reactions and also belong to the field of radiation chemistry. 

In the preceding chapter chemical effects of nuclear reactions have been discussed. On the other hand, the electronic structure, in particular chemical bonds, may affect nuclear properties. However, because the binding energies of the electrons are smaller by a factor of the order of 10 to 10 than the binding energies of the nucleons, the influence of chemical bonding on nuclear properties is, in general, relatively small. 

Mossbauer spectrometry has already been mentioned in discussing the chemical effects of nuclear reactions in solids (section 9.5). 

Research in nuclear and radiochemistry comprises Study of radioactive matter in nature, investigation of radioactive transmutations and of nuclear reactions by chemical methods, hot atom chemistry (chemical effects of nuclear reactions) and influence of chemical bonding on nuclear properties, production of radionuclides and labelled compounds, and the chemistry of radioelements - which represent more than a quarter of all chemical elements. 

Nuclear reactions may lead to stable or unstable (radioactive) products. In general, (n, y), (n, p), and (d, p) reactions give radionuclides on the right-hand side of the line of p stability that exhibit decay, whereas (p, n), (d,2n), (n, 2n), (y, n), (d, n) and (p, y) reactions lead to radionuclides on the left-hand side of the line of p stability that exhibit p decay or electron capture (e). (n, y), (d, p), (n, 2n) and (y, n) reactions give isotopic nuclides, and these cannot be separated from the target nuclides by chemical methods, except for the application of the chemical effects of nuclear transformations which will be discussed in chapter 9. 

Hot-atom chemistry Chemical effects of nuclear transfonnations (radioactive decay or nuclear reactions)... 

Wetherill GW (1975) diometiic chronology of the early solar system. Ann Rev Nud Sci 25 283 Wilczynski J, Volkov W, Decowski P (1967) Some features of the mechanism of many-neutron-transfer reactions. Sov J Nud Phys 5 672 Yad Fiz 5 942 Wilkins BD, Steinberg EP, Chasman RR (1976) Scission-point model of nuclear fission based on deformed-shell effects. Phys Rev G 14 1832 Wilkinson DH, Wapstra AH, Ulehla I et al (1993) Discovery of the transfermium dements, Report of the Transfermium Working Group of lUPAC and lUPAP II, Introduction to discovery profiles. III, Discovery profiles of the transfermium elements. Pure Appl Chem 65 1757, 1764 Willard JE (1953) Chemical effects of nuclear transformations. Ann Rev Nud Sci 3 193... 

Following the above mechanical use of nuclear recoil, purely chemical effects of nuclear recoil were observed by Szilard and Chalmers (1934a, b) in 1934. They used (n,y) reaction of iodine in ethyl iodide. The product of neutron capture, I, could be chemically extracted into an aqueous phase after mixing ethyl iodide with water. 

The Flerov Laboratory of Nuclear Reactions (FLNR) in Dubna, Russia, has recently announced the observation of relatively long-lived isotopes of elements 108, 110, 112, 114, and 116 [63-66] confirming the over 30 years old theoretical prediction of an island of stability of spherical superheavy elements. Due to the half-lives of the observed isotopes in the range of seconds to minutes, chemical investigations of these heaviest elements in the Periodic Table appear now to be feasible. The chemistry of these elements should be extremely interesting due to the predicted dramatic influence of relativistic effects [67], In addition, the chemical identification of the newly discovered superheavy elements is highly desirable as the observed decay chains [63-66] cannot be linked to known nuclides which has been heavily criticized [68,69],... 

None of the reactions or processes stndied in previous chapters affected the nucleus of an atom. No atom changed from one element to another. This chapter considers the effects of nuclear change. In most cases, such changes cause a transformation from one element to another. They include the natural radioactivity of certain isotopes (Section 3.3), as well as the artificial nuclear reactions discovered during the twentieth century. Nuclear reactions differ from ordinary chemical reactions in the following ways ... 

The chemical effects of mononuclear and binuclear reactions can be divided into primary effects taking place in the atom involved in the nuclear reaction, secondary effects in the molecules or other associations of atoms, and subsequent reactions. Primary and secondary effects are observed within about 10 s after the nuclear reaction. 

The chemical effects of the nuclear reaction I(n, are explained as follows In the first stage (primary effect) the chemical bond between and C is broken by the recoiling hot atom which loses its energy in a sequence of collisions with other molecules ( hot reactions ). By these reactions various fragments of the molecules are produced, which are difficult to detect because their concentration is... 

The chemical effects observed after neutron irradiation of ethyl iodide have found great practical interest, because they allow general application to various compounds and chemical separation of isotopic products of nuclear reactions. Above all, isotopic nuclides of high specific activity can be obtained by Szilard-Chalmers... 

An important consideration is the chemical effects of the nuclear reactions preceding the occurrence of a Mossbauer event. If, for example, the source preparation involves a long neutron irradiation of the intended source matrix... 

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