Exothermic reactions nuclear processes

Nuclear fission is the process in which a heavier nucleus (usually less stable) splits into smaller nuclei and neutrons. The process releases a large amount of energy and neutrons that can set up a chain reaction (or self-sustaining nuclear fission reactions) with more and more uncontrollable releases of energy (highly exothermic reactions) and neutrons. Examples of fission include the following ... 

Gibson, S.B., 1976. The design of new chemical plant using hazard analysis. Process Industry Hazards, Symposium Series No. 47. 135 (IChemE. Rugby. UK). HSE, 1992, Tolerability of Risk from Nuclear Power Stations, revised edition. Pantony, M.F.. Scilly. N.F. and Barton. J.A.. 1989. Safety of exothermic reactions a UK strategy, Int Symp on Runaway Reactions. 504—524 (CCPS, AIChE. USA). Kauffman, D. and Chen, H-J.. 1990, Fault-dynamic modelling of a phthalic anhydride reactor, J Loss Prev Process hid. 3 386-394. 

Eigure 22-2 illustrates this process schematically for fluorine 9p + 10iH F Because any stable nucleus is more stable than its separated nucleons, nuclear formation reactions of all stable nuclides are exothermic. 

The induction periods for the reaction of sodium nitrate—bitumen mixtures (43 57 wt) heated at 195, 234 or 260°C are 44, 2 and 0.5 h, respectively. Further study of sodium nitrate/bitumenised waste systems held at these temperatures showed an initial weak exotherm around 260°C and a larger exotherm (0.96—1.21 kJ/g) accompanied by 50% wt loss around 430°C [1]. Following an actual accident while encapsulating nuclear waste the system has been re-examined. With small nitrate crystal size, the mixing process can potentially give runaway from little above 160°C, by initial surface reaction slowly warming until the salt melts, whereupon exother-micity sharply increases [2]. 

The theory for this intermolecular electron transfer reaction can be approached on a microscopic quantum mechanical level, as suggested above, based on a molecular orbital (filled and virtual) approach for both donor (solute) and acceptor (solvent) molecules. If the two sets of molecular orbitals can be in resonance and can physically overlap for a given cluster geometry, then the electron transfer is relatively efficient. In the cases discussed above, a barrier to electron transfer clearly exists, but the overall reaction in certainly exothermic. The barrier must be coupled to a nuclear motion and, thus, Franck-Condon factors for the electron transfer process must be small. This interaction should be modeled by Marcus inverted region electron transfer theory and is well described in the literature (Closs and Miller 1988 Kang et al. 1990 Kim and Hynes 1990a,b Marcus and Sutin 1985 McLendon 1988 Minaga et al. 1991 Sutin 1986). 

The fact that the system has lost mass indicates that the process is exothermic. All spontaneous nuclear reactions are exothermic. 

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