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The woman who split the atom
\"As a female Jewish physicist in Berlin during the early 20th century, Lise Meitner had to fight for an education, a job, and equal treatment in her field, like having her name listed on her own research papers. Meitner made groundbreaking strides in the study of radiation, but when Hitler came to power in Germany, she suddenly had to face not only sexism, but also life-threatening anti-Semitism as well. Nevertheless, she persevered and one day made a discovery that rocked the world: the splitting of the atom. While her male lab partner was awarded a Nobel Prize for the achievement, the committee refused to give her any credit. Suddenly, the race to build the atomic bomb was on-although Meitner was horrified to be associated with such a weapon. \"A physicist who never lost her humanity,\" Meitner wanted only to figure out how the world works, and advocated for pacifism while others called for war. The book includes an afterword, author's note, timeline, select terms of physics, glossary of scientists mentioned, endnotes, select bibliography, index, and Marissa Moss' celebrated drawings throughout. The Woman Who Split the Atom is a fascinating look at Meitner's fierce passion, integrity, and her life-long struggle to have her contributions to physics recognized\"-- Provided by publisher.
CHILDBOOK
Concept of an Accelerator-Driven Advanced Nuclear Energy System
The utilization of clean energy is a matter of primary importance for sustainable development as well as a vital approach for solving worldwide energy-related issues. If the low utilization rate of nuclear fuel, nuclear proliferation, and insufficient nuclear safety can be solved, nuclear fission energy could be used as a sustainable and low-carbon clean energy form for thousands of years, providing steady and base-load electrical resources. To address these challenges, we propose an accelerator-driven advanced nuclear energy system (ADANES), consisting of a burner system and a fuel recycle system. In ADANES, the ideal utilization rate of nuclear fuel will be >95%, and the final disposal of nuclear waste will be minimized. The design of a high-temperature ceramic reactor makes the burner system safer. Part of fission products (FPs) are removed during the simple reprocessing in the fuel recycle system, significantly reducing the risks of nuclear proliferation of nuclear technology and materials. The ADANES concept integrates nuclear waste transmutation, nuclear fuel breeding, and safety power production, with an ideal closed loop operation of nuclear fission energy, constituting a major innovation of great potential interest for future energy applications.
Journal Article
Nuclear Fission–Nuclear Fusion algorithm for global optimization: a modified Big Bang–Big Crunch algorithm
This study introduces a derivative of the well-known optimization algorithm, Big Bang–Big Crunch (BB–BC), named Nuclear Fission–Nuclear Fusion-based BB–BC, simply referred to as N2F. Broadly preferred in the engineering optimization community, BB–BC provides accurate solutions with reasonably fast convergence rates for many engineering problems. Regardless, the algorithm often suffers from stagnation issues. More specifically, for some problems, BB–BC either converges prematurely or exploits the promising regions inefficiently, both of which prevent obtaining the optimal solution. To overcome such problems, N2F algorithm is proposed, inspired by two major phenomena of nuclear physics: fission and fusion reactions. In N2F, two concepts named “Nuclear Fission” and “Nuclear Fusion” are introduced, replacing the “Big Bang” and “Big Crunch” phases of BB–BC, respectively. With the “Nuclear Fission” phase represented through a parameter named amplification factor, premature convergence issues are eliminated to a great extent. Meanwhile, convergence rate and exploitation capability of the algorithm are enhanced largely through a precision control parameter named magnification factor, in the “Nuclear Fusion” phase. The performance of N2F algorithm is investigated through unconstrained test functions and compared with the conventional BB–BC and other metaheuristics including genetic algorithm, Particle Swarm Optimization (PSO), Artificial Bee Colony Optimization (ABC), Drone Squadron Optimization (DSO) and Salp Swarm Algorithm (SSA). Then, further analyses are performed with constrained design benchmarks, validating the applicability of N2F to engineering problems. With superior statistical performance compared to BB–BC, GA, PSO, ABC, DSO and SSA in unconstrained problems and improved results with respect to the literature studies, N2F is proven to be an efficient and robust optimization algorithm.
Journal Article
Titanium-Water Heat Pipe Radiators for Space Fission Power System Thermal Management
For future space transportation and planetary exploration mission power applications, NASA Glenn Research Center (GRC) is currently developing a small-scale nuclear fission system (i.e. Kilopower system), which has an operable range of 1 to 10 kWe and a design life of 8 to 15 years. The thermal management system of Kilopower system involves two types of heat pipes: high temperature alkali metal heat pipes that are used to transport thermal energy from the nuclear reactor to the Stirling convertors hot end and titanium water heat pipes that are used to remove the waste heat from the convertors cold end and transport it to the radiators for ultimate rejection. This paper presents the development of the titanium water heat pipes, which are featured with a special wick structure design: it has bi-porous screened evaporator and screen-groove hybrid wick in the adiabatic and condenser sections. This will allow the heat pipe to (1) operate in space with zero gravity (2) operate on planetary surface with gravity-aided orientation (3) be tested on ground with slight adverse gravity orientation and (4) to startup smoothly after being frozen. Under a research and development program, several freeze/thaw tolerant heat pipes were designed, fabricated and experimentally validated. Later, various heat pipe radiators were developed and tested in a thermal vacuum chamber (TVC). Test results successfully demonstrated that the titanium heat pipes with radiator attached are able to transfer the required power at the working temperature of 400 K under space-like testing conditions with a thermal resistance of 0.019 °C/W while the total heat pipe radiator weight is less than 0.73 kg.
Journal Article
TALYS: modeling of nuclear reactions
TALYS is a software package for the simulation of nuclear reactions below 200 MeV. It is used worldwide for the analysis and prediction of nuclear reactions and is based on state-of-art nuclear structure and nuclear reaction models. A general overview of the implemented physics and capabilities of TALYS is given. The general nuclear reaction mechanisms described are the optical model, direct reactions, compound nucleus model, pre-equilibrium reactions and fission. The most important nuclear structure models are those for masses, discrete levels, level densities, photon strength functions and fission barriers. A wide variety of nuclear reactions simulated with TALYS will be demonstrated, ranging from low-energy neutron cross sections, astrophysics, high-energy charged particle reactions and other reactions. TALYS is a nuclear reaction software which aims to give a complete description of nuclear reaction observables, and to be an important link between fundamental nuclear physics and applications.
Journal Article
High-Entropy Alloys for Advanced Nuclear Applications
The expanded compositional freedom afforded by high-entropy alloys (HEAs) represents a unique opportunity for the design of alloys for advanced nuclear applications, in particular for applications where current engineering alloys fall short. This review assesses the work done to date in the field of HEAs for nuclear applications, provides critical insight into the conclusions drawn, and highlights possibilities and challenges for future study. It is found that our understanding of the irradiation responses of HEAs remains in its infancy, and much work is needed in order for our knowledge of any single HEA system to match our understanding of conventional alloys such as austenitic steels. A number of studies have suggested that HEAs possess ‘special’ irradiation damage resistance, although some of the proposed mechanisms, such as those based on sluggish diffusion and lattice distortion, remain somewhat unconvincing (certainly in terms of being universally applicable to all HEAs). Nevertheless, there may be some mechanisms and effects that are uniquely different in HEAs when compared to more conventional alloys, such as the effect that their poor thermal conductivities have on the displacement cascade. Furthermore, the opportunity to tune the compositions of HEAs over a large range to optimise particular irradiation responses could be very powerful, even if the design process remains challenging.
Journal Article
Feasibility of producing molybdenum-99 on a small scale using fission of low enriched uranium or neutron activation of natural molybdenum
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Angular momentum generation in nuclear fission
When a heavy atomic nucleus splits (fission), the resulting fragments are observed to emerge spinning
1
; this phenomenon has been a mystery in nuclear physics for over 40 years
2
,
3
. The internal generation of typically six or seven units of angular momentum in each fragment is particularly puzzling for systems that start with zero, or almost zero, spin. There are currently no experimental observations that enable decisive discrimination between the many competing theories for the mechanism that generates the angular momentum
4
–
12
. Nevertheless, the consensus is that excitation of collective vibrational modes generates the intrinsic spin before the nucleus splits (pre-scission). Here we show that there is no significant correlation between the spins of the fragment partners, which leads us to conclude that angular momentum in fission is actually generated after the nucleus splits (post-scission). We present comprehensive data showing that the average spin is strongly mass-dependent, varying in saw-tooth distributions. We observe no notable dependence of fragment spin on the mass or charge of the partner nucleus, confirming the uncorrelated post-scission nature of the spin mechanism. To explain these observations, we propose that the collective motion of nucleons in the ruptured neck of the fissioning system generates two independent torques, analogous to the snapping of an elastic band. A parameterization based on occupation of angular momentum states according to statistical theory describes the full range of experimental data well. This insight into the role of spin in nuclear fission is not only important for the fundamental understanding and theoretical description of fission, but also has consequences for the γ-ray heating problem in nuclear reactors
13
,
14
, for the study of the structure of neutron-rich isotopes
15
,
16
, and for the synthesis and stability of super-heavy elements
17
,
18
.
γ-ray spectroscopy experiments on the origin of spin in the products of nuclear fission of spin-zero nuclei suggest that the fission fragments acquire their spin after scission, rather than before.
Journal Article
Nuclear Fuel in a Reactor Accident
Nuclear accidents that lead to melting of a reactor core create heterogeneous materials containing hundreds of radionuclides, many with short half-lives. The long-lived fission products and transuranium elements within damaged fuel remain a concern for millennia. Currently, accurate fundamental models for the prediction of release rates of radionuclides from fuel, especially in contact with water, after an accident remain limited. Relatively little is known about fuel corrosion and radionuclide release under the extreme chemical, radiation, and thermal conditions during and subsequent to a nuclear accident. We review the current understanding of nuclear fuel interactions with the environment, including studies over the relatively narrow range of geochemical, hydrological, and radiation environments relevant to geological repository performance, and discuss priorities for research needed to develop future predictive models.
Journal Article
Impact of pear-shaped fission fragments on mass-asymmetric fission in actinides
Nuclear fission of heavy (actinide) nuclei results predominantly in asymmetric mass splits
1
. Without quantum shell effects, which can give extra binding energy to their mass-asymmetric shapes, these nuclei would fission symmetrically. The strongest shell effects appear in spherical nuclei, such as the spherical ‘doubly magic’ (that is, both its atomic and neutron numbers are ‘magic’ numbers) nucleus
132
Sn, which contains 50 protons and 82 neutrons. However, a systematic study of fission
2
has shown that heavy fission fragments have atomic numbers distributed around
Z
= 52 to
Z
= 56, indicating that the strong shell effects in
132
Sn are not the only factor affecting actinide fission. Reconciling the strong spherical shell effects at
Z
= 50 with the different
Z
values of fission fragments observed in nature has been a longstanding puzzle
3
. Here we show that the final mass asymmetry of the fragments is also determined by the extra stability provided by octupole (pear-shaped) deformations, which have been recently confirmed experimentally around
144
Ba (
Z
= 56)
4
,
5
, one of very few nuclei with shell-stabilized octupole deformation
6
. Using a quantum many-body model of superfluid fission dynamics
7
, we find that heavy fission fragments are produced predominantly with 52 to 56 protons, which is associated with substantial octupole deformation acquired on the way to fission. These octupole shapes, which favour asymmetric fission, are induced by deformed shells at
Z
= 52 and
Z
= 56. By contrast, spherical magic nuclei are very resistant to octupole deformation, which hinders their production as fission fragments. These findings may explain surprising observations of asymmetric fission in nuclei lighter than lead
8
.
Quantum many-body calculations of superfluid fission dynamics reveal that heavy fragments from asymmetric fission of actinides are associated with considerable octupole (pear-shaped) deformation acquired on the way to fission.
Journal Article