Sulphur hexafluoride or SF6 is a synthetic gas consisting of six fluorine atoms gathered around one sulphur atom. The chemical bond between fluorine and sulphur is very strong: this gives the molecule a very high chemical and thermal stability. It is classified as a “greenhouse” gas, as it belongs to the F-Gas family.
Sulphur hexafluoride (SF6) has three main uses in the electrotechnical sector:
-electrical insulation, due to its high dielectric strength, which is about 2.5 times that of air at normal use pressure;
-electric arc extinction, thanks to the electronegativity of the molecules, the excellent cooling capacity of the arc and the high speed of molecular recomposition following the action of the arc;
Sulphur hexafluoride (SF6) is NOT toxic; moreover, it is not carcinogenic, it is not mutagenic, it is not harmful to the environment, it does not contribute to the destruction of the ozone layer. However, it does strongly impact the greenhouse effect.
The Kyoto Protocol is an international environmental treaty concerning global warming. It was signed in the Japanese city of Kyoto on 11 December 1997 by more than 160 countries at the COP3 Conference of the United Nations Framework Convention on Climate Change (UNFCC). The treaty entered into force on February 16, 2005, after ratification also by Russia.
Global warming indicates the anthropogenic contribution as decisive in the warming phase of the Earth’s climate in the last hundred years.
Sulphur hexafluoride (SF6) has a high Global Warming Potential (GWP) of 22,800 times that of carbon dioxide (CO2). This makes it very impactful on the greenhouse effect.
To give a practical example, the emission of 1 kg of SF6 corresponds to the emissions of an average car with a traditional engine that travels about 120,000 km.
Regeneration is a process of treating a recovered fluorinated greenhouse gas to bring it back to a certain quality standard. Referring to sulphur hexafluoride (SF6), a higher technical quality is achieved than that defined by technical standard CEI 60376.
Sulphur hexafluoride (SF6), once used, does not need to be disposed of by thermal destruction, but can be recovered.
-If the quality of the gas complies with the specifications of technical standard CEI 60480, the gas can be reused.
-If the gas quality does not meet the specifications of technical standard CEI 60480, the gas must be regenerated. The regeneration process allows the gas to be brought back to a quality level equivalent to new gas.
Environmentally, it is better to regenerate SF6 gas rather than dispose of it, as it avoids having to create new gas that will have to be disposed of in the future. Both the production and destruction of gas results in the release of SF6 into the atmosphere.
The F-Gas Database is a portal managed by the Ministry of Environment that allows to monitor the emissions of fluorinated greenhouse gases. It is divided into four sections:
-Sales of F-Gas.
-Communication of sales, intended for sellers of fluorinated greenhouse gases and equipment not hermetically sealed containing such gases, after registration in the National Electronic Register of Certified Persons and Companies (FGAS Register).
-Communication of installation, leakage control, maintenance, repair and dismantling work carried out on fixed refrigeration, air conditioning, heat pump and cold storage equipment of trucks and refrigerated trailers, fixed fire protection equipment and electrical switches.
-Operators, to download a certificate containing all the information related to their equipment.
The European F-Gas License is a certification required by the EU517/2014 and EU2015/2066 regulations. It is mandatory for all operators who carry out:
-installation, servicing, maintenance, repair or dismantling of equipment containing fluorinated gases;
-leak checks in equipment containing fluorinated gases;
-recovery of fluorinated greenhouse gases.
Regarding the certification of personnel performing activities on SF6 gas (Regulation 2066/2015), the certificate of competence is issued by a certification body accredited by ACCREDIA. The assessment of personnel for their certification can be carried out by the certification body or by another body qualified by the certification body.
The National Electricity System is the result of three operational phases: production, transmission and distribution of electricity.
Electricity is essential for every kind of activity of our society. Electricity production in Italy is largely carried out by exploiting non-renewable energy sources (oil, coal and natural gas), but also geothermal, hydroelectric, solar or wind energy.
Electricity transmission is the intermediate step between production and distribution to users. It takes place via the high-voltage, long-distance electricity transmission grid, an infrastructure operated and developed nationwide by the respective transmission system operator.
Electricity distribution represents the conclusion of the energy process. Electricity is delivered to the end user through a complex network infrastructure consisting mostly of medium and low voltage power lines.
Electrical substations are the nodes of the electricity transmission grid and are located near a production plant, at the point of delivery to the end user and at the points of interconnection between lines. There are four types of substations, depending on the function they perform:
-Interconnect several high-voltage power lines together at the same voltage level, creating a network node (via bars);
-interconnect several high voltage power lines at different voltage levels (through transformers);
-rephasing the apparent power of the network (through batteries of capacitors or inductors of power factor correction, also called “reactors” because they absorb reactive power);
-convert the voltage from alternating to direct and vice versa (conversion substations).
Nuclear fusion is a nuclear reaction process in which two or more atoms are compressed until strong interaction prevails over magnetic repulsion. The atoms fuse together (hence ‘fusion’) creating a new nucleus of greater mass. Nuclear fusion is currently considered one of the useful options for securing a large-scale, safe, environmentally friendly, and virtually inexhaustible source of energy.
The main advantages of nuclear fusion are:
-Abundance of fuel.
-Exiguous amount needed to produce a large amount of electricity from a single fusion.
-No pollutants or greenhouse gases are emitted into the atmosphere.
-No radioactive waste is produced.
-No risk of catastrophic events because the power is produced in a controlled manner.
-The disadvantages of nuclear fusion are:
-Complex technology, requiring long lead times and significant economic investment.
-Use of tritium, which requires a lot of attention in handling because it is radioactive.
-Production of neutrons, which can make the internal components of the reactor radioactive.
Nuclear Fusion and Nuclear Fission are two opposite reactions, which however are subject to the same physical principle and both are used to produce nuclear energy.
Nuclear fusion is the process by which light nuclei of two or more atoms melt to create a heavier nucleus, with a simultaneous release of energy. The reaction less difficult to realize foresees the use of Deuterium and Tritium with trigger temperature of the order of 100 million degrees centigrade.
Nuclear fission, instead, is a process in which the atomic nucleus of a heavy chemical element (for example Uranium-235 or Plutonium-239) decays in smaller fragments, that is in nuclei of atoms with lower atomic number, with emission of a great quantity of energy and radioactivity.
Fusion is more difficult to realize than fission, because it is necessary to reach very high temperatures, but the amount of energy emitted is much greater.
The fission reaction foresees a series of chain reactions that risk going out of control, generating catastrophic events; fusion, instead, does not foresee chain reactions, so the process remains under control.
The fission reaction involves the use of Uranium that generates highly radioactive products with an average life of thousands of years. The fusion reaction, however, uses Deuterium and Tritium that generate more stable products: these cause the problem of radioactive waste.
The RFX Consortium was founded in 1996 in Padua. It’s a scientific organization promoted by CNR, ENEA, University of Padova, INFNand Acciaierie Venete to support cooperation among research centres, companies and industries in the development of technological solutions in the field of scientific research for controlled thermonuclear fusion.
ITER (acronym for International Thermonuclear Experimental Reactor) is an international project that aims to build an experimental nuclear fusion reactor, able to produce a fusion plasma with more power than the power required to heat the plasma itself. Specifically, ITER is a deuterium-tritium reactor in which the confinement of the plasma is achieved in a magnetic field within a machine called Tokamak.
MITICA, which stands for “Megavolt ITER Injector and Concept Advancement”, is the full-scale prototype of the neutral particle injector for the ITER International Experimental Fusion Reactor, obtained by the acceleration of high-energy negative ions.
SPIDER is the acronym of “Source for the Production of Ions of Deuterium Extracted from a Radio frequency plasma” and is the prototype of the ion source to be used for the injector. It has the same dimensions of those that will be used for the injector of ITER and will be able to operate at maximum power for 3600s generating a beam of 6 MW.