Science & Technology - Nuclear Technology

Science & Technology - Nuclear Technology

Nuclear Energy + Robotics + Nano Science

• Nuclear technology is “the technology that involves the reactions of atomic nuclei”. It has found applications from smoke detectors to nuclear reactors and from gun sights to nuclear weapons.
• Currently, approximately 17% of electricity worldwide is produced by nuclear power plants, but in some countries, like France, over 75% of their electricity is produced by nuclear power. The United States, on the other hand, only produces about 15% of the electricity from nuclear power.
• Nuclear fusion refers to the “union of atomic nuclei to form heavier nuclei resulting in the release of enormous amounts of energy”.
• Fusion takes place when two low-mass isotopes, typically isotopes of hydrogen, unite under conditions of extreme pressure and temperature. Fusion is what powers the sun. Atoms of Tritium and Deuterium (isotopes of hydrogen, Hydrogen-3 and Hydrogen-2, respectively) unite under extreme pressure and temperature to produce a neutron and a helium isotope. Along with this, an enormous amount of energy is released, which is several times the amount produced from fussion.
• Scientists continue to work on controlling nuclear fusion in an effort to make a fusion reactor to produce electricity. Some scientists believe there are opportunities with such a power source since fusion creates less radioactive material than fussion and has a nearly unlimited fuel supply. However, progress is slow due to challenges with understanding how to control the reaction in a contained space.
• The word fission means “a splitting or breaking up into parts”. Nuclear fussion releases heat energy by splitting atoms. The surprising discovery that it was possible to make a nucleus divide was based on Albert Einstein’s prediction that mass could be changed into energy. In 1939, scientist began experiments, and one year later Enrico Fermi built the first nuclear reactor.
• Nuclear power plants use pellets to fuel the plants. A pellet contains approximately 3% U-235 that is encased in a ceramic matrix.

                             

Working:

• Nuclear fission produces heat, and this heat is used to heat water and make steam. The steam powers turbines which turn generators.
• The generators produce electricity. Nuclear power generates electricity much like coal- or diesel-powered plants. What is different from the other two, is that nuclear doesn’t produce greenhouse gases like the burning of fossil fuels. It does produce spent nuclear fuel that is radioactive, and this has disposal problems.
• The two main types of reactors in use today are the pressurized water reactor (PWR) and boiling water reactor (BWR). In the pressurized water reactor the water is heated by the nuclear reactions, but because the water is pressurized, it doesn’t boil. The water in the reactor heats the water in the steam generator side, but it is on a different loop so they do not mix. In the boiling water reactor, the water comes to a boil due to the heat produced by nuclear fission. The water from the reactor powers the turbine. In both systems, the water is reused.

There are several components common to all types of reactors:

• • Fuel: Usually pellets of uranium oxide (UO2) arranged in tubes to form fuel rods. The rods are arranged into fuel assemblies in the reactor core.
  • Moderator: This is material which slows down the neutrons released from fission so that they cause more fission. It is usually water, but may be heavy water or graphite.
  • Control rods: These are made with neutron-absorbing material such as cadmium, hafnium or boron, and are inserted or withdrawn from the core to control the rate of reaction, or to halt it. (Secondary shutdown systems involve adding other neutron absorbers, usually as a fluid, to the system.)
  • Coolant: A liquid or gas circulating through the core so as to transfer the heat from it. In light water reactors the moderator functions also as coolant.
  • Pressure vessel or pressure tubes: Usually a robust steel vessel containing the reactor core and moderator/coolant, but it may be a series of tubes holding the fuel and conveying the coolant through the moderator.
  • Steam generator: Part of the cooling system where the heat from the reactor is used to make steam for the turbine.
  • Containment system: The structure around the reactor core which is designed to protect it from outside intrusion and to protect those outside from the effects of radiation in case of any malfunction inside. It is typically a meter-thick concrete and steel structure.

• Today, nuclear science is responsible for many technological advances that we enjoy as part of daily life. Nuclear science and technology promote sustainable development by improving health and the quality of life. This is done through varied applications such as nuclear medicine, food preservation and safety, industrial materials and processes, basic scientific research, environmental studies, and the generation of electrical power with minimal environmental impact.
  • Health and Medicine: An estimated 16 million nuclear medicine imaging and therapeutic procedures are performed each year in the India. Nuclear technology also helps treat cancer, test drugs and to sterilize surgical instruments and medical supplies.
  • Agriculture and Food Safety: One-third to one-half of the food produced in the world is lost due to spoilage and infestation. Nuclear technologies can prevent much of this loss by delaying spoilage. Food irradiation technology kills illness-causing microorganisms, such as Salmonella, ampylobacter, and E. Coli, which frequently contaminate fresh meat and poultry.
  • Consumer Products: Nuclear technology is essential to many products that contribute to every-day health and safety, such as smoke-alarms, radial tires and fail-safe lighting sources that require no energy supply. Every day products such as cosmetics, hair products and contact lens solutions are sterilized with radiation.
  • Scientific Research: Entire areas of research and development in chemistry, metallurgy, genetics, biotechnology, hydrology and many other fields of science and engineering exist because of nuclear technologies. Radioisotopes are essential to biomedical research on AIDS, cancers and Alzheimer’s disease. Deep space exploration would be impossible without small nuclear powered generators. Radionuclides are essential tools for genetic research and determining the structure of DNA. Radio isotopic measurement techniques are the only way for accurately dating many historical and archeological artifacts and geologic formations.
  • Environmental Protection: Nuclear technology is not limited to research; it is also used to solve problems while eliminating harmful environmental impacts. Radioisotope techniques are essential to climatological investigations related to climate change. Radionuclides are helpful in determining plant and sea assimilation of greenhouse gases, and measuring carbon dioxide releases from industrial areas. Radioisotope techniques are used to study the chronology of contaminated river and lake sediments. Rather than using toxic chemicals, solid wastes and sewage can be treated with radiation techniques.

India’s Three-Stage Nuclear Power Programme

• India’s three-stage nuclear power programme was formulated by Homi Bhabha in the 1950s to secure the country’s long term energy independence, through the use of uranium and thorium reserves found in the monazite sands of coastal regions of South India.
• The ultimate focus of the programme is on enabling the thorium reserves of India to be utilized in meeting the country’s energy requirements.
• Thorium is particularly attractive for India, as it has only around 1–2% of the global uranium reserves, but one of the largest shares of global thorium reserves.
• However, at present thorium is not economically viable because global uranium prices are much lower.
• The recent Indo-US Nuclear Deal and the NSG waiver, which ended more than three decades of international isolation of the Indian civil nuclear programme, have created many hitherto unexplored alternatives for the success of the three-stage nuclear power programme.
• Thorium itself is not a fissile material, and thus cannot undergo fission to produce energy.
• Instead, it must be transmuted to uranium-233 in a reactor fueled by other fissile materials [plutonium239 or uranium-235].
• The first two stages, natural uranium-fueled heavy water reactors and plutonium-fueled fast breeder reactors, are intended to generate sufficient fissile material from India’s limited uranium resources, so that all its vast thorium reserves can be fully utilized in the third stage of thermal breeder reactors.

Stage I – Pressurized Heavy Water Reactor (PHWR)

• In the first stage of the programme, natural uranium fuelled pressurized heavy water reactors (PHWR) produce electricity while generating plutonium-239 as by-product.
• PHWRs was a natural choice for implementing the first stage because it had the most efficient reactor design [uranium enrichment not required] in terms of uranium utilization.
• India correctly calculated that it would be easier to create heavy water production facilities (required for PHWRs) than uranium enrichment facilities (required for LWRs).
• Almost the entire existing base of Indian nuclear power (4780 MW) is composed of first stage PHWRs, with the exception of the two Boiling Water Reactor (BWR) units at Tarapur Atomic Power Station.

Stage II – Fast Breeder Reactor

• In the second stage, fast breeder reactors (FBRs) [moderators not required] would use plutonium-239, recovered by reprocessing spent fuel from the first stage, and natural uranium.
• In FBRs, plutonium-239 undergoes fission to produce energy, while the uranium-238 present in the fuel transmutes to additional plutonium-239.

Why should Uranium-238 be transmuted to Plutonium-239fi

• Uranium-235 and Plutonium-239 can sustain a chain reaction. But Uranium-238 cannot sustain a chain So it is transmuted to Plutonium-239.

Why U-238 and not U-235fi

• Natural uranium contains only 0.7% of the fissile isotope uranium-235. Most of the remaining 99.3% is uranium-238.
• Thus, the Stage II FBRs are designed to “breed” more fuel than they consume.
• Once the inventory of plutonium-239 is built up thorium can be introduced as a blanket material in the reactor and transmuted to uranium-233 for use in the third stage.
• The surplus plutonium bred in each fast reactor can be used to set up more such reactors, and might thus grow the Indian civil nuclear power capacity till the point where the third stage reactors using thorium as fuel can be brought online.

Stage III – Thorium Based Reactors

• A Stage III reactor or an advanced nuclear power system involves a self-sustaining series of thorium-232uranium-233 fuelled reactors.
• This would be a thermal breeder reactor, which in principle can be refueled – after its initial fuel charge – using only naturally occurring thorium.

Prototype Fast Breeder Reactor at Kalpakkam

• The Prototype Fast Breeder Reactor (PFBR) is a 500 MWe fast breeder nuclear reactor established at the Madras Atomic Power Station in Kalpakkam, India.
• The Indira Gandhi Centre for Atomic Research (IGCAR) is responsible for the design of this reactor
• The Kalpakkam PFBR is using uranium-238 not thorium, to breed new fissile material, in a sodium cooled fast reactor design.
• The surplus plutonium or uranium-233 for thorium reactors [U-238 transmutes into plutonium] from each fast reactor can be used to set up more such reactors and grow the nuclear capacity in tune with India’s needs for power.
• The fact that PFBR will be cooled by liquid sodium creates additional safety requirements to isolate the coolant from the environment, since sodium explodes if it comes into contact with water and burns when in contact with air.

What Hinders Deployment of Thorium-Fuelled Reactors In Indiafi

• Most people would assume that it is a limitation of technology. But instead, it is due to shortage of uranium fuel that is needed to convert fertile fuel [thorium] into fissile [fuel that can undergo sustained chain reaction].
• Scientists at the Bhabha Atomic Research Centre have successfully tested all relevant thorium-related technologies in the laboratory.
• In fact, if pressed, India could probably begin full-scale deployment of thorium reactors in ten years.
• The single greatest hurdle, to answer the original question, is the critical shortage of fissile material.

What is a fissile materialfi

• A fissile material is one that can sustain a chain reaction upon bombardment by neutrons.
• Thorium is by itself fertile, meaning that it can transmute into a fissile radioisotope [U-233] but cannot itself keep a chain reaction going.
• In a thorium reactor, a fissile material like uranium or plutonium is blanketed by thorium.
• The fissile material, also called a driver in this case, drives the chain reaction to produce energy while simultaneously transmuting the fertile material into fissile material.
• India has very modest deposits of uranium and some of the world’s largest sources of thorium. It was keeping this in mind that in 1954, Homi Bhabha envisioned India’s nuclear power programme in three stages to suit the country’s resource profile.
• In the first stage, heavy water reactors fuelled by natural uranium would produce plutonium [U-238 will be transmuted to Plutonium 239 in PHWR];
• The second stage would initially be fuelled by a mix of the plutonium from the first stage and natural uranium. This uranium would transmute into more plutonium and once sufficient stocks have been built up, thorium would be introduced into the fuel cycle to convert it into uranium 233 for the third stage [thorium will be transmuted to U-233 with the help plutonium 239].
• In the final stage, a mix of thorium and uranium fuels the reactors. The thorium transmutes to U-233 which powers the reactor. Fresh thorium can replace the depleted thorium [can be totally done away with uranium which is very scares in India] in the reactor core, making it essentially a thorium-fuelled reactor [thorium keeps transmuting into U-233. It is U-233 that generates the energy].

Present State of India’s Three-Stage Nuclear Power Programme

• After decades of operating pressurized heavy-water reactors (PHWR), India is finally ready to start the second stage.
• A 500 MW Prototype Fast Breeder Reactor (PFBR) at Kalpakkam is set to achieve criticality any day now and four more fast breeder reactors have been sanctioned, two at the same site and two elsewhere.
• However, experts estimate that it would take India many more FBRs and at least another four decades before it has built up a sufficient fissile material inventory to launch the third stage.

Solution to India’s Fissile Shortage Problem – Procuring Fissile Material Plutonium

The obvious solution to India’s shortage of fissile material is to procure it from the international market

Favourable Conditions for Plutonium Trade

• As yet, there exists no commerce in plutonium though there is no law that expressly forbids it.
• In fact, most nuclear treaties such as the Convention on the Physical Protection of Nuclear Material address only U-235 and U-233.
• This is because Plutonium has so far not been considered a material suited for peaceful purposes.
• The Non-Proliferation Treaty (NPT) merely mandates that special fissionable material — which includes plutonium — if transferred, be done so under safeguards.
• Thus, the legal rubric for safeguarded sale of plutonium and safety procedures for moving radioactive spent fuel and plutonium already exists but it is not too complicated as in case Uranium.
• Japan and the U.K. who are looking to reduce their stockpile of plutonium will certainly be happy to sell it to India.

NANOTECHNOLOGY AND ITS APPLICATIONS

• Nanotechnology is the study of matter at a miniature level called the nano scale. A nano meter is equal to one billionth of a meter. What makes study at atomic scale is that the properties of atoms and molecules are found to greatly differ on a nano scale, i.e., at 100 nm or below compared to what they are in bulk matter.
• Exploiting this feature of matter, nanotechnology manipulates single atoms to discover new properties and then uses these to create improved materials, devices and systems.
• Nanotechnology is not a new discipline. It is rather the merging of multiple scientific disciplines (biology, physics, chemistry, medicine and engineering) and the combination of knowledge to tailor materials at the nanoscale.
• From agriculture to aerospace research, nanotechnology’s impact is being felt. Research in nanotechnology spans across an array of fields such as health, environment, agriculture, food and beverages, product development, space technology, power generation, genetics, biotechnology, forensic science, electronics and communications.

Application of Nanotechnology

Nano Medicine               

The size of nano materials is similar to that of most biological molecules and structures; therefore, nano-materials can be useful for both in-vivo (inside the body) and in-vitro (outside body) biomedical research and applications. It led to the development of diagnostic devices, contrast agents, analytical tools, physical therapy applications, and drug delivery vehicles.

 Drug Delivery:  Nanotechnology has provided the possibility of delivering drugs to specific cells using nanoparticles (increases effectiveness, less side effects).

Tissue Engineering: Tissue engineering is the new emerging field of science which makes use of nanotechnology to repair the damaged tissues. The cells can be artificially reproduced by using suitable nanomaterials scaffolds and other growth factors.

Diagnostic: The use of nanomaterials to diagnose different diseases is the most important achievement of medical field. Nanoparticles are attached to the antibody or they can be attached to the molecules to label or to see the structures of proteins in any organism.

Sensing: Lab-on-chip technology, where magnetic nano particles bound to a suitable antibody, are used to label specific molecules, structures or microorganisms. Gold nanoparticles tagged with short segments of DNA can be used for detection of genetic sequence in a sample.

FOOD

• Nanotechnology offers some exciting potential benefits for the quality and safety of our foods. Contamination Sensor:                Flash a light to reveal the presence of E. coli bacteria.
• Antimicrobial Packaging: Edible food films made with cinnamon or oregano oil, or nano particles of zinc, calcium other materials that kill bacteria.
• Improved Food Storage: Nano-enhanced barrier keeps oxygen-sensitive foods fresher. Enhanced
• Nutrient Delivery: Nano-encapsulating improves solubility of vitamins, antioxidants, healthy omega oils and other ‘nutraceuticals’.
• Green Packaging: Nano-fibers made from lobster shells or organic corn are both antimicrobial and biodegradable.
• Pesticide Reduction: A cloth saturated with nano fibers slowly releases pesticides, eliminating need for additional spraying and reducing chemical leakage into the water supply.
• Tracking, Tracing Brand Protection: Nanobarcodes can be created to tag individual products and trace outbreaks.
• Texture: Food spreadability and stability improve with nano-sized crystals and lipids for better lowfat foods.
• Flavor: Trick the tongue with bitter blockers or sweet and salty enhancers.
• Bacteria Identification and Elimination: Nano carbohydrate particles bind with bacteria so they can be detected and eliminated.

Environment 

• Besides lighter cars and machinery that requires less fuel and alternative fuel and energy sources, there are many eco-friendly applications for nanotechnology, such as materials that provide clean water from polluted water sources in both large-scale and portable applications, and ones that detect and clean up environmental contaminants.
• Nanotechnology could help meet the need for affordable clean drinking water through rapid, low- cost detection of impurities in and filtration and purification of water.
• Nanoparticles can be used to clean industrial water pollutants in ground water through chemical reactions that render them harmless at much lower cost than methods that require pumping the water out of the ground for treatment.
• Researchers have developed a nanofabric “paper towel,” woven from tiny wires of potassium manganese oxide that can absorb 20 times its weight in oil for cleanup applications.
• Many Airplane cabin and other types of air filters are nanotechnology-based filters that allow “mechanical filtration,” in which the fiber material creates nanoscale pores that trap particles larger than the size of the pores. They also may contain charcoal layers that remove odors.
• New nanotechnology-enabled sensors and solutions can be able to detect, identify, and filter out and/or neutralize harmful chemical or biological agents in the air and soil with much higher sensitivity than is possible today.

Nano Mission of India

• The Nano Mission is an umbrella programme for capacity building which envisages the overall development of this field of research in the country and to tap some of its applied potential for nation’s development. In brief, the objectives of the Nano-Mission are:
  • Basic Research Promotion – Funding of basic research by individual scientists and/or groups of scientists and creation of centers of excellence for pursuing studies leading to fundamental understanding of matter that enables control and manipulation at the nanoscale.
  • Infrastructure Development for Nano Science & Technology Research – Investigations on the nano scale require expensive equipments like Optical Tweezers, Nano Indenter, Transmission Electron Microscope (TEM), Atomic Force Microscope (AFM), Scanning Tunneling Microscope (STM), Matrix Assisted Laser Desorption Time of Flight Mass Spectrometer (MALDI TOF MS), Microarray Spotter & Scanner etc. For optimal use of expensive and sophisticated facilities, it is proposed to establish a chain of shared facilities across the country.
  • Nano Applications and Technology Development Programmes – To catalyze Applications and Technology Development Programmes leading to products and devices, the Mission proposes to promote application-oriented R&D Projects, establish Nano Applications and Technology Development Centers, Nano-Technology Business Incubators etc. Special effort will be made to involve the industrial sector into nanotechnology R&D directly or through Public Private Partnership (PPP) ventures.
  • Human Resource Development – The Mission shall focus on providing effective education and training to researchers and professionals in diversified fields so that a genuine interdisciplinary culture for nanoscale science, engineering and technology can emerge. It is planned to launch M.Sc./M.Tech. Programmes create national and overseas post-doctoral fellowships, chairs in universities, etc.
  • International Collaborations – Apart from exploratory visits of scientists, organization of joint workshops and conferences and joint research projects, it is also planned to facilitate access to sophisticated research facilities abroad, establish joint centers of excellence and forge academia industry partnerships at the international level wherever required and desirable.