CONCEPT DESIGN FOR A SUEZMAX TANKER POWERED BY A 70 MW SMALL MODULAR REACTOR

The authors are to be congratulated on a well- researched and timely technical paper. I am pleased to express my personal opinion on the subject. COSCO was intending to initiate a study in December 2009 on nuclear powered ship design in order to reduce GHG emissions from shipping. However, this plan was aborted three years after, following the catastrophic accident at the Fukushima nuclear power station in Japan during March 2011. This intensified political and public opposition to nuclear power to the extent that Germany has since adopted plans to decommission its entire nuclear infrastructure. However, confidence is beginning to re- emerge - confidence which I share. With increasing attention being given to GHG emissions arising from burning fossil fuels for global aviation and marine transport, together with the excellent safety record of nuclear power in the marine environment and the development of the new generation of SMRs, it is quite conceivable that renewed attention will be given to the application of nuclear power in merchant ship propulsion. In producing this paper, the authors have made a significant contribution in the field of innovative ship design development. They have demonstrated the feasibility of applying the latest generation of nuclear reactor to commercial ship propulsion. Whereas nuclear power has been widely used in vessels of a number of navies and icebreakers, it has yet to be adopted for commercial ships other than a small number of research projects. This paper has provided good rationale for accommodating nuclear power in merchant shipping including speed and range requirements, required specific volume on board, environmental considerations etc. The study has also considered the risks associated with design and the arrangement of nuclear systems including location of the SMR, type of propulsion options and other safety- critical issues, not least the radiological risk to persons on board, involved in maintenance and in port.

Hyperons in Finite and Infinite Nuclear Systems

In this work, we shortly review the role and properties of hyperons in finite and infinite nuclear systems such as hypernuclei and neutron stars. Particularly, we describe different production mechanisms of hypernuclei, discuss some aspects of their γ-ray spectroscopy and their weak decay modes, and give a few strokes on their theoretical description. We reexamine also the role played by hyperons on the properties of neutron and proto-neutron stars with a special emphasis on the well-known “hyperon puzzle”, of which we discuss some of the solutions that have been proposed to tackle this problem. Finally, we review the role of hyperons on the cooling properties of newly born neutron stars and on the so-called r-mode instability.

AI-based design of a nuclear reactor core

The authors developed an artificial intelligence (AI)-based algorithm for the design and optimization of a nuclear reactor core based on a flexible geometry and demonstrated a 3× improvement in the selected performance metric: temperature peaking factor. The rapid development of advanced, and specifically, additive manufacturing (3-D printing) and its introduction into advanced nuclear core design through the Transformational Challenge Reactor program have presented the opportunity to explore the arbitrary geometry design of nuclear-heated structures. The primary challenge is that the arbitrary geometry design space is vast and requires the computational evaluation of many candidate designs, and the multiphysics simulation of nuclear systems is very time-intensive. Therefore, the authors developed a machine learning-based multiphysics emulator and evaluated thousands of candidate geometries on Summit, Oak Ridge National Laboratory’s leadership class supercomputer. The results presented in this work demonstrate temperature distribution smoothing in a nuclear reactor core through the manipulation of the geometry, which is traditionally achieved in light water reactors through variable assembly loading in the axial direction and fuel shuffling during refueling in the radial direction. The conclusions discuss the future implications for nuclear systems design with arbitrary geometry and the potential for AI-based autonomous design algorithms.

Thermochemistry of Polonium Evaporation from LBE

Polonium is formed in relatively large quantities in lead-bismuth eutectic (LBE) cooled nuclear systems. Because of its radiotoxicity and volatility, a good understanding of the chemical equilibria governing polonium release from LBE is required. In this work, a set of thermochemical data is derived for the chemical species involved in the equilibrium between a solution of polonium in LBE and its vapor in inert conditions. The data were obtained by matching thermochemical models with experimental vapor pressure measurements and ab initio results. The dilute-limit activity coefficient of dissolved polonium in LBE is estimated, as well as the solubility of solid lead polonide in LBE. The results indicate that polonium evaporates from LBE according to the experimentally determined Henry’s law, up to dissolved polonium concentrations well above that expected in LBE cooled nuclear systems.

Efimov Physics and Connections to Nuclear Physics

Physical systems characterized by a shallow two-body bound or virtual state are governed at large distances by continuous scale invariance, which is broken into discrete scale invariance when three or more particles come into play. This symmetry induces a universal behavior for different systems that is independent of the details of the underlying interaction and rooted in the smallness of the ratio ℓ[Formula: see text] a B ≪ 1, where the length a B is associated with the binding energy of the two-body system [Formula: see text], and ℓ is the natural length given by the interaction range. Efimov physics refers to this universal behavior, which is often hidden by the onset of system-specific nonuniversal effects. In this review, we identify universal properties by providing an explicit link of physical systems to their unitary limit, in which a B → ∞, and we show that nuclear systems belong to this class of universality. Expected final online publication date for the Annual Review of Nuclear and Particle Science, Volume 71 is September 2021. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.