Should we really spend billions to make a few atoms? A look into superheavy element synthesis3/8/2020 By Ayan Banerjee  Facility at the Flerov laboratory of Nuclear Reactions, Dubna, Russia With so many governments running huge deficits to keep the economy afloat at the moment, now more so than ever we need to be carefully scrutinising all areas in which we allocate resources. The synthesis of superheavy elements is an example of a branch of research that requires significantly large amounts of scientific resources which begs the question: is it a justifiable use of these resources?
Superheavy elements are also known as transactinide’s, therefore, are elements with an atomic number beyond the actinide period range: Z > 103.1. It's also important to note that synthesis is the artificial production of these elements provided that they exist for at least 10-14 seconds. For this investigation, scientific resources will be considered to include the sum of capital, labour, materials, energy and all other expenses used. The synthesis of these elements doesn't have a long history, with the first superheavy element only being synthesised in 1964 (Rutherfordium) and the most recent, Oganesson, discovered in 2002. Therefore, for this relatively young branch of scientific research, we're going to look into whether it's a good use of our scarce resources by evaluating the associated gains and costs. Firstly, to evaluate the costs, we need to detail the various methods of superheavy element synthesis. A major challenge when forming progressively heavier elements is overcoming the increasing electrostatic repulsion within the nucleus. Therefore, different production methods were utilised for different superheavy elements as they possess differing nuclear structures and compositions. For elements 103 < Z < 107, two heavy nuclei – one accelerated in a ‘heavy-ion beam’ using a cyclotron, and the other stationary – are collided, fusing and forming a superheavy compound nucleus. However, the compound nucleus’s excited state (high energy) made it progressively more unstable making nuclei heavier than Z = 106 unfeasible with this method. In the early 1990s at the GSI laboratory, scientists were able to use cold fusion to form nuclei in the range 106 < Z < 113. Since the fusion occurred at a lower temperature, the products were at a less excited state and therefore, more stable. However, as they attempted to produce elements with Z > 112 it became apparent that even cold fusion couldn’t overcome the larger electrostatic repulsion between heavier projectile ions. Furthermore, the projectile ions lacked the sufficient number of neutrons to form stable compound nuclei. Therefore, a new synthesis approach would need to be developed. This new method consisted of using the rare isotope Ca-48 (28 neutrons, 20 protons) as the projectile ion. The resulting compound nucleus has an even lower excitation energy than using the cold fusion method. Additionally, the larger relative mass difference between the projectile nuclei results in a lower coulomb repulsion force which is easier to overcome making fusion feasible. Neutron-enriched isotopes of transuranium such as americium are used as a target material. This method was able to produce the elements 112 < Z < 119, the remaining heaviest elements that we have discovered so far. These various synthesis methods require a significant range of scientific resources which make up the majority of total costs. One of the largest costs is that of the reactors. These take up large amounts of lab space and require expensive specialist components as well as the labour of highly trained engineers and scientists. For example, the Russian Joint Institute for Nuclear Research in Dubna where numerous superheavy elements were discovered had a manufacturing cost of $238M and currently employs 4500 people. However the costs can be even higher such as at the Lawrence Berkeley National Laboratory which cost $2.2B to construct. These accelerators often utilise powerful cyclotrons which consist of expensive magnets and superconductors to achieve ultra-fast beams of ions. Complex detectors purposed with tracking individual particles are additionally very expensive and extremely difficult to construct, often requiring years of design and manufacturing. Additionally, there are high costs associated with running these reactions which can often be ongoing for weeks at a time. Energy usage is extremely high from the advanced components and machinery used to create and contain high-energy particle beams. This power usage can often exceed 100MW in certain reactors, equivalent to that of a small city. The superconductors require cooling to temperatures close to absolute zero, only achievable through the use of expensive liquid helium as a coolant. However, arguably one of the most expensive aspects of this process is the use of Ca-48. This rare isotope makes up roughly only 0.19% of the world’s naturally occurring calcium. Not only does this require a significant amount of time to produce, but also costs roughly $200,000 per gram. Even though accelerators are optimised to use higher intensity beams reducing the rate of Ca-48 usage, the cumulative usage across long-duration experiments builds up a significant cost. Scientists’ time and effort is also another resource that is utilised significantly for the complex synthesis of these superheavy elements. Overall, the synthesis of superheavy elements requires a combination of significant direct construction, labour, materials, reactants and time costs. Furthermore, the use of these required resources also presents an opportunity cost: equivalent to the value lost in the alternative uses of the resources. Similar materials and capital used for superheavy element synthesis are also used in other areas of particle and nuclear sciences. For example, particle accelerators can be used to research areas in theoretical, particle and relativistic nuclear physics. These all could potentially lead to answers to major scientific questions about the fundamental properties of the universe. The exchangeable capital would include the expensive liquid helium coolant, superconductors and magnets use to focus particle beams and additionally powerful and costly cyclotrons. Furthermore, many of the scientists and engineers could be placed on alternative projects, although this would be challenging as they are mainly specialised in highly specific areas. Although there are significant costs, synthesising superheavy elements presents a range of benefits and opportunities, not only to the scientific community but also to the world as a whole. Potentially, some of these benefits may stem from the direct uses of superheavy elements. However, since they have only recently been possible to synthesise, many of their uses and properties are still unknown. This was also the case in the 20th century, when transuranium were first explored, however, continued synthesis and research discovered a range of uses. This includes the use of americium in smoke detectors, curium and californium for neutron radiography and interrogation and also plutonium in nuclear weapons. Therefore, beneficial direct uses may be discovered from the further synthesis and research of superheavy elements. Furthermore, superheavy elements synthesis can present a range of indirect benefits. Most notably, more research through their production could provide sufficient data to prove the theory of ‘the island of stability.’ This refers to a theorised region of superheavy elements on the periodic table that have half-lives significantly longer in magnitude relative to other superheavy elements. These half-lives could be seconds or minutes relative to other elements that last nanoseconds. The ‘island of stability’ region is categorised by containing nuclei that have a spherical shape. Comparably, the exploration and synthesis of transuranium elements provided sufficient understanding to disprove Bohr’s ‘liquid-drop’ model which improved theories in the area of nuclear physics. Discoveries in this area would provide an improved understanding of what keeps nuclei together and how some heavy nuclei are able to resist fission. Furthermore, the skills developed from carrying out these processes can be used to solve problems such as in national security and the management of radioactive sources such as nuclear weapons. Most significantly, scientists believe that the decay of these superheavy elements could provide information on what binds subatomic particles together and therefore, the forces involved in nucleosynthesis. This may address whether there is a final boundary on the periodic table. Overall, the synthesis of superheavy elements presents many indirect uses which could answer major questions improving our overall understanding in the sciences. To determine if superheavy element synthesis is a good use of scientific resources, we need to address whether the direct and indirect gains exceed the associated costs and opportunity costs. It's difficult to determine the direct benefits as most are currently unknown. However, the positive externalities from conducting this research are far-reaching and significant in the areas of theoretical and nuclear sciences. Furthermore, there may be unforeseen indirect benefits such as in newfound applications of the skills and understanding gained from carrying out these processes. More importantly, we need to question the purpose of scientific research. I believe it's to improve our understanding of the world around us and the universe or to invent and discover new technologies to improve lives - something both exciting and incredible useful. In this case, the synthesis of superheavy elements could provide important opportunities in both areas. Since the possible benefits are so significant, especially to the scientific community, I believe that the benefits do outweigh the costs and it is a good use of scientific resource. References:
Do you think the synthesis of superheavy elements is a good use of scientific resources? Please let us know in comments section below.
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