The Nuclear Second Law, Part I: Engineering

<ns3:p> This work proposes a paradigm shift in nuclear safety. Fission and fusion phenomena are treated as inertial processes referring to the instant of fission <ns3:sup>1</ns3:sup> n <ns3:sub>0</ns3:sub> capture or union of nuclei. This simple supposition has profound implications when applied to the thermodynamic understanding of a nuclear engine. MeV release from a mass defect is: independent of terrestrial reference; not affected by temperature, kinetic, or physical potential; a single phenomenon describes the macro; and has no enthalpic meaning. The only appropriate descriptive vehicle for nuclear phenomena lies with Second Law exergy analysis, treating its MeV release as a thermodynamic potential. Such potential is termed an ultimate “Free Exergy,” consisting of both recoverable and irreversible portions. In transference to a coolant the recoverable release produces an exergetic increase (ṁΔg), the fluid exergy’s T <ns3:sub>Ref</ns3:sub> being explicitly computed from an Inertial Conversion Factor (Ξ). Importantly, Ξ also transforms recoverable nuclear release to an explicit, and consistent, thermal power (ṁΔh). This approach demands reinterpretation of Einstein’s ΔE = c <ns3:sup>2</ns3:sup> Δm by describing his ΔE, not as an ΔEnergy, but an ultimate ΔFree Exergy. Asserted is that nuclear phenomena traditionally have had no direct computational nexus with thermodynamics. Since N Reactor days, there has been no direct nexus between nuclear power and its resultant energy flow. N Reactor’s neutron flux was not well measured, but was the motive force behind delivering 4000 MWt to the Columbia River. It is well known that neutron flux in a 1270 MWe PWR is approximately 1.0x10 <ns3:sup>13 1</ns3:sup> n <ns3:sub>0</ns3:sub> cm <ns3:sup>−2</ns3:sup> sec <ns3:sup>−1</ns3:sup> . A back-calculated flux based on a thermal rating of 3640 MWt produces twice this flux. From the time of the Manhattan Project, nuclear engineers have treated flux as a relative parameter: hard to measure, a relative value to be normalized, is not uniform in the axial or radial, etc. </ns3:p>