Nuclear Energy

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About Nuclear Energy

Introduction
The peaceful use of nuclear energy is growing in various walks of life, including industrial, medical, agricultural and other fields. The generation of electricity from nuclear energy is one of the most important uses by generating clean and economically competitive energy. It is also a sustainable technology that guarantees the right of future generations to fossil resources as a result of the availability of their fuel for decades.

Nuclear energy now provides about 10% of the world’s electricity from about 440 power reactors distributed in more than 30 countries. Currently there are about 50 reactors under construction, and many countries have announced plans to develop nuclear power generation programs and consider them as a strategic energy option.

Since its inception, the technology of nuclear power reactors has undergone several developments from the first generation to the so-called advanced Nuclear Power Reactors  generation ( III +) . The designs of this advanced generation are characterized by the adoption of standard and stereotypical techniques, which has reflected positively on the safety and cost factors of these reactors.

The Egyptian Nuclear Program (Key Events)

1955
Establishment of Atomic Energy Commission.
1957
Establishment of Atomic Energy Institution.
1961
Operating the first research reactor at Inshas.
1963
Establishment of the Nuclear Engineering Dept at Alexandria University.
1964
Invitation for an international tender to construct a nuclear power plant for electricity generation and sea water desalination at Sidi-krer.
1966
Issuance of a Letter of Intent to the first company in the tender.
1967
War of June 1967,the project came to a halt.
1974
Invitation for a restricted tender among American companies to implement the project of constructing a nuclear power plant at Sidi-Krir.
1976
Establishment the Nuclear Power Plants Authority (NPPA).
1976
Establishment of the Supreme Council of Energy.
1977
Establishment of the Nuclear Materials Authority.
1979
The project stopped as a result of Three Mile Island (TMI) accident in the United States.
1980
Selection of El-Dabaa site for the construction of the Egyptian nuclear power plant.
1981
Issurance of the presidential decree to allocate El-Dabaa site to establish the nuclear power project.
1981
Approval of the Supreme Council of Energy for the Egyptian nuclear program.
1981
Establishing a fund to support alternative energy projects.
1982
Invitation for an international tender for the construction of a nuclear power plant at El-Dabaa site.
1986
The project was interrupted as a result of Chernobyl accident in the former Soviet Union.
1998
Installation and operation of the second Egyptian experimental reactor at Inshas.
2006
Starting a national dialogue to study the use of nuclear power in electricity generation.
2006
Re-formation of the Supreme Council of Energy chaired by the Prime Minister.
2007
Declaration of Egypt`s strategic decision to build a number of reactors for electricity generation.
2007
Formation of the Supreme Council for the Peaceful use of nuclear energy headed by the President of the Republic.
2008
Invitation for an international tender to select a consultancy firm for the construction of the nuclear power plant.
2011
Upgrading and finalizing the specifications of the first nuclear power plant in cooperation with the experts of the IAEA in the wake of Fukushima accident.
2013
Issuance of the decision of the Council of Ministers in its session held 10/10/2013 approving to NPPA to resume the consultant`s work to implement the phases with regard to the nuclear power plant project.
2014
Contracting with the Engineering Authority of the Armed Forces for the rehabilitation of El-Dabaa site with the basic facilities, protecting and securing it, Completion of environmental monitoring system at the site.
2015
Signing of an Inter-governmental agreement between Egypt and Russia on cooperation in the field of building and operating the first nuclear power plant in Egypt with the Russian technology.
2016-2017
Negotiations with the Russian party to build, operate, fuel supplying, storage of spent fuel for a nuclear power plant consisting of 4 units with VVER type reactors, 1200 MW each.
2019
Site Approval Permit (SAP) for El Dabaa site was issued by the Egyptian Nuclear Regulation and Radiological Authority (ENRRA).

Nuclear Safety

Safety principles in nuclear plants

 Nuclear safety is the protection of individuals, the environment and society against the harmful effects of ionizing radiation, including the safety of nuclear facilities and activities.  A series of strict technical and administrative measures according to international standards designed to prevent, control and, if so, mitigate of accident consequences, which is called Principle of (defense in depth). Preventing the incident is the primary and ultimate objective of all those concerned with nuclear energy. Achieving nuclear safety is the responsibility of the operating organization.

In the design of nuclear power plants, there is combination of a number of consecutive and independent five levels of protection that would have to fail before harmful effects could be caused to people or to the environment. If one level of protection or barrier were to fail, the subsequent level or barrier would be available. This concept in design is called “defence in depth”.The first four levels are oriented towards the protection of barriers and mitigation of releases; the last level relates to off-site emergency measures to protect the public in the event of a significant release.

Radiation Protection

Protection and safety of workers and the public from the effects of exposure to ionizing radiation is a binding requirement in the nuclear industry. The International Commission on Radio-logical Protection (ICRP) has identified three main principles for the achievement of radio-logical protection:

 justification Principle: The process of determining whether a practice is, overall,
beneficial, as required by ICRP’s System of Radiological Protection, i.e. whether the benefits to individuals and to society from introducing or continuing the practice outweigh the harm (including radiation detriment) resulting from the practice.

Optimization Principle: The process of determining what level of protection and safety makes exposures, and the probability and magnitude of potential exposures, “as low as reasonably achievable (ALARA), economic and social factors being taken into account” . It includes (time – distance – shielding – engineering features).

Dose Constraints Principle: The individual dose, other than medical exposure of patients, shall not exceed the limits prescribed by the national regulator.

Nuclear Reactor Types

Introduction

Nuclear power reactors are divided into two main types depending on the interaction type. Fission reactors for power generation and fusion reactors for power generation. Nuclear fission reactors are also divided into two main types based on the velocity of particles (neutrons) that cause nuclear fission: thermal reactors and fast reactors.

Pressurized Water Reactor (PWR)

It is the most widespread in the world, with 310 reactors representing about 66% of the world’s nuclear reactors, 43 of which are under construction. These reactors use enriched uranium between 3-5% of uranium-235 as a fuel, and light water as a coolant and moderator. The fuel is made in the form of small tablets with a height of 2 cm and less than 1 cm in diameter. These tablets are packed into long tubes called fuel rods, each of which is about 4 meters long.

The cladding of fuel rods is usually made of zirconium or stainless steel alloys because of the ability to conduct heat, high resistance to corrosion and rust, and also to their low absorption of neutrons. A number of fuel columns are assembled in a regular engineering arrangement using a metal mesh to be the so-called fuel Assemblies. The reactor’s capacity is linked to the number of fuel assemblies in it.

The fuel Assemblies are assembled into the so-called Reactor pressure vessel , a cylindrical bowl with a Hemispherical head, one of the most important components in the station that determines the lifetime of the reactor.

The cooling water is maintained under high pressure of about 160 bar through the so-called Pressurizer. Accordingly, transforming coolant from liquid to steam is prevented inside the reactor core. Therefore, a secondary circuit is used to transfer the cooling water temperature and then to produce steam and generate electricity. The presence of the secondary circuit increases the safety of these reactors by separating the primary cooling cycle exposed to the radiation from the steam-generating cycle to the turbine.

Boiling Water Reactor (BWR)

Which is the most common of the most prevalent, where there are 63 reactors operating, representing about 16% of the number of nuclear reactors in the world, and there are two reactors under construction. These reactors use enriched uranium between 3-5% of uranium-235 as a fuel, and light water as a coolant and moderator.

The composition of the fuel rods are not different from that used in PWRs, except in the form of fuel assemblies consisting of a number of fuel rods, which are grouped together by a metal mesh and placed together to form the fuel assemblies.

The coolant is maintained under an average pressure of up to 70 bar, allowing it to boil inside the reactor core, forming the steam that goes directly to the turbine, which in turn runs generators.

 


Water Cooled Graphite-Moderated Reactor (RBMK)

The heart of the reactor consists of clusters of graphite blocks interspersed with pipes called pressure tubes containing inside the columns of nuclear fuel passing through it and inside these pipes the cooling water, which turns into steam, which comes out directly to the turbines.

Graphite is used in this type of reactor as a moderator of neutrons, and light water is used as a coolant. It is worth mentioning that the first nuclear power plant in the world of this type was the “Obeninsk” plant, which began operation in July 1954 in the former Soviet Union with a capacity of 5 megawatts electric and it was decommissionnined in 2002. It is noteworthy that the Chernobyl-4 reactor which The nuclear incident occurred on April 26, 1986, resulting in a radiation leak of this type of reactor. There are no reactors of this kind in the world except within what was known as the former Soviet Union. This type of reactor differs from ordinary compressed water reactors and boiling water reactors in the absence of a concrete containment container surrounding it and the components of the cooling cycle to withstand the pressure and temperatures produced in the case of severe accidents, which prevents the leakage of radiation to humans and the environment.

Pressurized Heavy Water Reactor (PHWR)

49 Of these reactors are operating reactors, representing 10% of the world’s nuclear reactors. Two of the reactors are under construction and are of medium electric capacity and have been developed mainly in Canada. Natural uranium (which contains 0.7% of the uranium-235) is used as fuel and heavy water (where deuterium replaces hydrogen in water) for cooling and moderating purposes. Heavy water is characterized by low neutron absorption, which helps to increase the number of neutrons available to cause fission, thus allowing the use of natural uranium directly and without the need for enrichment.The coolant water of the reactor is kept under pressure and inside tubes containing fuel assemblies and a secondary circuit is used to generate steam. The reactor can be refueled online during operation.

Advanced Gas Cooled Reactor (AGCR)

The gas-cooled nuclear reactors were the first reactors to control serial nuclear fission processes. The first nuclear reactor was built and operated in 1942, known as the “Fermi” reactor. The actual use of these reactors began in the generation of electric power since the mid-1950s. Where many countries, led by Britain, began building the first generations of these reactors. The most important known types of gas cooled reactors are:

– Magnox reactors

– Advanced gas cooled reactors

– High temperature gas cooled reactors

1 – MAGNOX reactors
The Magnox reactors use nuclear fuel in the form of metal uranium, the uranium-235 equivalent of about 0.7%, which is the ratio found in natural uranium. The use of natural uranium metal as fuel to maintain operational conditions in the  reactor core to avoid damage to fuel and packaged at temperatures or high combustion rates and therefore designed to operate at temperatures up to 350 °C.

The core of the reactor contains a number of graphite blocks with vertical channels of fuel. The fuel rods are made of natural uranium metal coated with a thin layer of Magnox (Magnesium – Aluminum – Brillium – Copper). These reactors are therefore called Magnox.

Carbon dioxide is used as a refrigerant under pressure of up to 13 Atmospheric pressure. The heat of the reactor passes through the coolant to six steam generators on both sides of the reactor’s core, where the steam is generated, which in turn turns to the turbine generating the electricity and the coolant returns to the core of the reactor. Graphite is used as a moderator, and in the form of blocks with channels through which fuel columns and control shafts enter.

2 – Advanced gas cooled reactors AGR
Despite the safe operation of the Magenox reactors, the desire to improve operating parameters led to some development of modern generations of gas cooled reactors, known as advanced gas cooled reactors.

Uranium dioxide is slightly used (2 – 3 % of uranium – 235) as fuel. The fuel is made in the form of short, hollow capsules of income. These tablets are assembled in stainless steel casing with a ratio of chromium and niobium made up of fuel columns.

Carbon dioxide is used under pressure of up to 39 atmospheric pressure as a refrigerant. The heat of the reactor’s heart is transferred by the radiator to the steam generators where the steam is generated, which in turn turns to the turbine generating electricity, and the coolant returns to the reactor core. Graphite is used as a sedative where the heart of the reactor contains a number of graphite blocks that have channels containing fuel aggregates.

3 – HTGR gas heating reactors
This type of reactor uses uranium with a high proportion of uranium-235 mixed with the thorium-232 as fuel. The use of the thorium-232 in the fuel industry is due to the fact that it turns into a uranium-233 equivalent when absorbed into neutrons. Because the uranium-233 is fissionable, it is considered an addition to the original fuel. The fuel is made in the form of short capsules of “Uranium carbide and thorium” encased in graphite and placed in the cavities of graphite blocks used as a sedative.

Helium gas is used as a coolant and is characterized as an inert gas that does not interact with graphite, which is used as a moderator, no matter how high it is, and it does not absorb neutrons and therefore does not turn into radioactive gas.

Nuclear Fuel

Nuclear fuel is a fissionable nuclear material in the form of fabricated elements that are used in nuclear power reactors, or research and test reactors. Nuclear fuel is traditionally obtained by extracting uranium from solid ores mined from uranium deposits or from rather uranium rich rocks. After extraction, concentration and specific solid fuel preparation, the fuel is ‘burnt’ in reactors for the production of heat and electricity.

Nuclear fuel cycle is all operations associated with the production of nuclear energy. Most nuclear fuels contain heavy fissile elements that are capable of undergoing and sustaining nuclear fission. The three most relevant fissile isotopes are uranium-233, uranium-235 and plutonium-239.

Uranium-235 is used as a fuel in different concentrations. Some reactors, such as the CANDU reactor, can use natural uranium with uranium-235 concentrations of only 0.7%, while other reactors )mainly the light water reactors( require the uranium to be slightly enriched to levels of 3% to 5%. Plutonium-239 is produced and used in reactors (specifically fast breeder reactors) that contain significant amounts of uranium-238.

Advantages of using nuclear fuel:

  • It is very high energy compared to other types used in generating electricity, and a few Pellets of nuclear fuel can be placed by the individual in the palm of his hand to meet the needs of a whole family for a year.
  • Nuclear reactors need to generate electricity only for a limited amount of nuclear fuel per year, so it is easy to transport and store as a strategic stock and in quantities sufficient to operate the plants for many years.
  • The resulting waste is small in size, and therefore can be stored for long periods in a small space.
  • The contribution of nuclear fuel to electricity production costs is lower than that of other types, so electricity prices remain almost constant in case of fluctuation and price increases.
  • Maintains a clean environment where its use does not result in environmentally destructive gases such as carbon oxides, sulfur and nitrogen.
  • Available in abundant quantities and reliable as fuel for hundreds of years.

Nuclear Waste

Nuclear energy, like all different energy sources, produces waste that is treated to protect humans and the environment from its negative effects. Waste generated from the use of a specific energy source differs in terms of its size, characteristics and disposal methods, so the volume of waste generated by a coal-fired power plant with a capacity of one thousand megawatts needs Every day to 1000 tons of coal, and this process results in the release of 300 tons of sulfur dioxide, and five tons of ash that contains other elements such as: chlorine, cadmium, arsenic, mercury, and lead, in addition to some radioactive elements. For generating the same electrical energy from its nuclear counterpart (500) cubic meters of waste per year.

Sources of radioactive waste

Radioactive waste results from the following activities:

•The burning of nuclear fuel in nuclear power plants to produce what is called spent fuel.

•All processes and phases of the nuclear fuel cycle.

•The use of radioisotopes in scientific research, industry, mining and agriculture.

•Nuclear medicine, including diagnosis, treatment, drug production and radioactive sources.

Classification of radioactive waste

There is no international standard classification for radioactive waste, and the factors involved in the classification of radioactive waste include:

•The type of radioactive elements and their concentration in the waste.

•The half-life of radioactive elements (the time period during which the intensity of the radioactive level of a radioactive element shrinks in half. It is a natural characteristic that varies from one type of element to the other. ”

•The physical state of the waste in terms of liquidity, solidity and gaseousness.

•Waste treatment and disposal methods. Treatment of radioactive waste The most important goals of treating radioactive waste is to get rid of radioactive isotopes and prevent their harm to the environment and humans, and this includes their collection, sorting, reduce their size, change their chemical and physical composition, and finally, condition them to be hardened and packed before storage and disposal.

Radioactive waste management

There are three main stages in treating radioactive waste:

1-pre-treatment stage

It includes sorting and separation to separate radioactive materials from non-radioactive materials. This step is considered necessary to reduce the volume of waste (for example: by cutting or shredding) and facilitate its disposal and accordingly minimizes the cost of disposal.

2-the treatment stage

Generally, treatment processes tend to reduce the volume or radioactive waste by separating out the radioactive component from the bulk waste, often changing the waste’s composition in the process.  A variety of waste treatment processing steps are available for use, depending on the nature of the waste and the waste acceptance requirements of the chosen disposal site. Two common treatment techniques are: incineration of solid waste and evaporation of liquid waste.

3-the conditioning stage

Brings the waste into a safe, stable and manageable form so it can be transported, stored and disposed. Conditioning techniques are designed to prevent the release of radionuclides from the disposed waste package into the environment. To condition waste for disposal, it is often encapsulated or solidified in cement, bitumen or glass containers.

Last Updated on June 2, 2021