The importance of the proposed study in the context of the existing knowledge
For many centuries, nuclear reactors in the world hav been relying on fuel cycles based on uranium. Nevertheless, the element thorium is a potential source of nuclear energy in certain types of nuclear reactors. In fact, it is clear that the element thorium has a number of advantages when used as a source of energy in nuclear reactors over uranium, which is making it a good alternative for investment in the nuclear energy sector.
Theorite is the most common form of thorium mineral. Studies have demonstrated that theorite is a highly radioactive element with the potential of replacing uranium in nuclear reactors. The element is three times more common than uranium. In addition, the amount of thorium within the earth’s crust has more energy production potential than a combination of the existing uranium and fossil fuels in the crust.
Benefits of thorium
It is estimated that the abundance of thorium in the Earth’s crustis 3 to 4 times compared with uranium. It is also widely distributed, easily exploitable and is met in many parts of the world. The fact that it is not commercially exploited means that the resource can be exploited easily, making it a good complement for uranium to ensure that nuclear power is a long-term source of energy.
Secondly, thorium fuel cycle has low levels of radioactive waste, making it a highly reliable source of energy with little degree of environmental pollution. By incinerating civilian plutonium or WPu (weapons grade thorium), scientists are able to establish a transition of thorium in nuclear reactors.Thorium is almost three times more radioactive than Uranium, which has 238U (239 barns). Therefore, it is evident that a higher conversion of the material to 233U can be obtained with 232Th than when 238U is converted to 239Pu.
Moreover, the number of neutrons released per each absorbed neutron (η) is about 2.0 for the fissile 233U, which is not possible with 235U and 239Pu.The 232U-239Thcycle obtains breeding using only fast neutron spectra. On the other hand, the 232Th-233U fuel cycle operates only with a fast thermal/epithermal spectrum. The rate of releasing fission product is in one order of magnitude less in thorium-based fuels than in the uranium-dioxide fuels.
With higher thermal conductivity and a low co-efficient of thermal expansion than uranium dioxide, thorium dioxide shows evidence of favorable thermo-physical properties than uranium dioxide. Therefore, thorium dioxide-based fuels will have a better in-pile performance when used as energy sources compared to uranium dioxide and uranium dioxide-based mixed oxides, making it a better source than the latter.
Unlike uranium dioxide, thorium dioxide is chemically neutral and does not oxidize easily. The oxidation of uranium dioxide to U3O and UO3 is an easy process, but difficult with thorium dioxide. Therefore, thorium dioxide shows evidence of higher interim storage and permanent disposal when it is used as fuels. This makes both interim storage and permanent disposal simpler and safer than when uranium dioxide-based fuels are used because thorium dioxide does not pose problems associated with easy oxidation.
Studies have further indicated the ease of using (Th,Pu)O2 cycle instead of more difficult (U,Pu)O2cycles because the (Th,Pu)O2 cycle does not breed plutonium. In addition, the 232U formed after the cycle is important in ensuring a strong proliferation resistance.
The 232Th-233U fuel cycle forms far less quantities of plutonium. In addition, long-lived minor actinides (MA: Am, Cm and Np)result from the process. This is in contrast with the 238U-239Pu fuel cycle and implies that the possibility of minimizing the radioactivity of the spent fuel is higher in the 232Th-233U cycle than in the 238U239Pu cycle. Nevertheless, thorium is also likely to result into a number of radionuclides such as 2229Th, 231Pa and 230U, which have shown some evidence of long-term radiological effects.
The thorium fuel cycle has the capacity to achieve a longer burn-up than the uranium fuel cycle. The modern nuclear reactors normally burn fuel in the range of 30,000-60,000 MWd/tU. According to the US department of Energy, thorium fuels have a capacity to burn for about 150,000 MWd/tTh. A fuel material that burns for a long period is fissile, which means that it is possible to create more energy and release transuranic waste after the burning. Noteworthy, thorium fits these characteristics while the standard cladding material cannot withstand the high levels of pressure and heat.
Objectives of the study
To study the properties of Thorium
Thorium takes position number 90 in the periodic table. Thorium is a naturally occurring metal that is slightly radioactive in its natural form. In nature, thorium-232 is the most common form of the element found in nature, although more than 33 different isotopes of the element have been found.
To look at the reserves and extraction of Thorium
The United States of America, India and Australia are the three nations with the largest reserves of thorium. According to OECD and IAEA, India has the largest deposits of thorium in the world. According to the official estimates of the government of India, the country has about 846,477 tons of natural thorium.
To study the manufacturing and properties of the Thorium fuel cycle
In nature, thorium-232 has been found to be a non-fissile material. However, if provided with a source of neutron, such as the uranium-235, the thorium-232 is jumpstarted into a fission chain reaction by making it absorb a single neutron and change to thorium-233. With a half-life of about 22 minutes, thorium-233 is able to emit an electron at the end of the 22 minutes, which causes it to decay into the proactinum-233. After 27 days, the proactinum-233 obtained from the process releases yet another electron, which makes it change to uranium-233 as follows:
232Th (n,γ) 233Th (β−) 233Pa (β−) 233U (n,2n)
To determine the advantages and disadvantages of using thorium as a source of fuel in reactors
Thorium fuel cycles have been shown to have a number of advantages when compared with uranium fuel cycles. For instance, thorium fuel cycles have greater resistance to the proliferation and production of less actinides. Nevertheless, a number of other issues should be considered, including the separation of Th-233 before it is used in nuclear reactors.
To use thorium in reactors and compare it with the past experiences
It has been shown that thorium cycles are feasible in the existing fast and thermal reactors. For instance, the LWRs, which include WWERs (like WWER-T), HGTFRs, PHWRs, ADS and LMFBRs have shown evidence of feasibility of thorium cycles when used as an energy source. It is possible to include thorium fuel cycle in most of these reactors with little need for modifying the systems. However, before incorporating thorium cycles in the existing reactors, scientists need to carry our comprehensive studies and technological developments.
To reprocess thorium and waste management
Only a few countries have tried to reprocess spent thorium fuel based on the OREX process. In addition, a few cases where the process has taken place are normally laboratory or pilot studies, with little attempt to do it on a large scale or for commercial purposes. Although thorium-based fuel cycles do not release minor actinides, they are associated with the production of a number of other radionucleotides such as 229Th, 231Pa and 230P0U, which have a long-term radiological effect.
To study the economics of using thorium fuel
The prices of uranium, the maturity of uranium cycle and the amount of work needed to develop a thorium cycle define the current energy market conditions. Considering these issues, it is likely that nations such as India and China will not progress technologically.
Demonstration of my abilities to carry out the proposed research
The purpose of applying for admission at the Nuclear Engineering PhD program is to satisfy my passion to develop my career in the nuclear energy sector, especially in the nuclear fuel field. I believe that the nuclear engineering PhD program has potential to help me to achieve my career objectives.
My interest in the nuclear science field is old, dating back to my days in formative schools. To improve my career, I successfully completed my undergraduate program at the University of Baghdad, graduating with a Bachelor of Physics degree.
I was ranked number 15 out of the 104 graduates in the course, which shows evidence of my academic capabilities. During my days at the University of Baghdad, my obsession with physical science became a reality. Although I have a long history of interest in physical sciences, it was at the University of Baghdad that my journey towards understanding nuclear science started. Moreover, it was at the university that I had a chance to visit a nuclear reactor. When visiting the reactor, I made a strong decision to pursue a career in the field to the highest possible level.
During my days at the University Baghdad, I focused mainly on the need to understand the fundamental principles of nuclear physics. However, I enrolled in a Master’s Program at the University of Liverpool, United Kingdom. Here, I had a chance to understand nuclear physics from a deeper and wider perspective than at the undergraduate level. I have been a member of the research teams in nuclear science, from where I have gained first-hand experience in managing nuclear security. In addition, I obtained a chance to work with highly experienced nuclear scientists both in the field and research environments.
My interest in pursuing a PhD program is influenced by personal and professional considerations. Pursuing a career in the nuclear sector is a personal goal while the current market conditions provide evidence of the need to pursue a career in the energy field.
My choice for your school for my PhD program is influenced by my belief that your facilities will provide me with a solution to my desires. The university is a leading institution in nuclear technology. Therefore, it will give me the necessary exposure as I sought to acquire more skills in the field. It will be great honor to become a part of your institution.