Subject: Basic Sciences

Plastic from used personal protective equipment (PPE) can be transformed into renewable liquid fuels using chemical a process called pyrolysis, says a new study.

Try this PYQ:

Q.In the context of which one of the following are the terms ‘pyrolysis and plasma gasification’ mentioned? (CSP 2019)

(a) Extraction of rare earth elements

(b) Natural gas extraction technologies

(c) Hydrogen fuel-based automobiles

(d) Waste-to-energy technologies

What is Pyrolysis?

• Pyrolysis is the thermal decomposition of materials at elevated temperatures in an inert atmosphere.
• It involves a change in chemical composition. The word is coined from the Greek-derived elements pyro “fire” and lysis “separating”.
• It is most commonly used in the treatment of organic materials. It is one of the processes involved in charring wood.
• It is considered as the first step in the processes of gasification or combustion.

How does it work?

• In general, pyrolysis of organic substances produces volatile products and leaves a solid residue enriched in carbon, char.
• Extreme pyrolysis, which leaves mostly carbon as the residue, is called carbonization.
• The process is used heavily in the chemical industry, for example, to produce ethylene, many forms of carbon, and other chemicals from petroleum, coal, and even wood, to produce coke from coal.

Applications

• Aspirational applications of pyrolysis would convert biomass into syngas and biochar, waste plastics back into usable oil, or waste into safely disposable substances.

Limitations and Concerns

• The technology requires drying of soil prior to treatment.
• Limited performance data are available for systems treating hazardous wastes containing polychlorinated biphenyls (PCBs), dioxins, and other organics.
• There is concern that systems that destroy chlorinated organic molecules by heat have the potential to create products of incomplete combustion, including dioxins and furans.
• These compounds are extremely toxic in the parts per trillion range.
• The molten salt is usually recycled in the reactor chamber. However, depending on the waste treated (especially inorganics) and the amount of ash, spent molten salt may be hazardous and require special care in disposal.
• Pyrolysis is not effective in either destroying or physically separating inorganics from the contaminated medium.
• Volatile metals may be removed as a result of the higher temperatures associated with the process, but they are not destroyed.
• When the off-gases are cooled, liquids condense, producing an oil/tar residue and contaminated water.
• These oils and tars may be hazardous wastes, requiring proper treatment, storage, and disposal.

Ahead of the laying of the foundation stone for a temple, claims and denials have emerged about plans to put in a time capsule, or ‘Kaal Patra’.

Do you know?

A rubidium standard or rubidium atomic clock is the most inexpensive, compact, and widely produced atomic clock, used to control the frequency of television stations, cell phone base stations, in test equipment, and global navigation satellite systems like GPS.

What is a Time Capsule?

• It is a container of any size or shape, which accommodates documents, photos and artefacts typical of the current era and is buried underground, for future generations to unearth.
• The time capsule requires special engineering so that the contents don’t decay, even if pulled out after a century.
• Material such as aluminium and stainless steel are used for the encasing, and documents are often reproduced on acid-free paper.
• While the term “time capsule” was coined in the 20th century, among the earliest examples of one dates back to 1777, found by historians inside the statue of Jesus Christ in Spain during its restoration.

There’s a global society:

International Time Capsule Society

• The International Time Capsule Society (ITCS), based in the US and formed in 1990, is now defunct but continues estimating the number of time capsules in the world.
• As per its database, there are “10,000-15,000 times capsules worldwide”.

Are there any time capsules in India?

• There have been a number of prominent examples.
• One time capsule, outside the Red Fort and placed underground in 1972 by then PM Indira Gandhi, was dug out by the subsequent government.
• Other time capsules are at a school in Mumbai, IIT-Kanpur, LPU in Jalandhar, and Mahatma Mandir in Gandhinagar.
• The Red Fort time capsule was supposed to be dug out after 1,000 years.

Significance of time capsules

• Historians often criticize the idea of being motivated.
• This exercise is inevitably a subjective exercise, geared towards glorification not to construct the real picture.
• All historians look at this time capsule exercise with suspicion.
• It’s not a valid historical method — who decides what matter, what artefacts, written documents are going into it?

Ahead of the 75th anniversary of Hiroshima, a Japanese court has recognised 84 survivors of the post-nuclear explosion “black rain” as the atomic bomb survivors. This would enable them to avail free medical benefits.

Try this question from CSP 2011:

Q.Acid rain is caused by the pollution of the environment by:

(a) Carbon dioxide and nitrogen

(b) Carbon monoxide and carbon dioxide

(c) Ozone and carbon dioxide

(d) Nitrous oxide and Sulphur dioxide

What is Black Rain?

• An estimated 69 per cent of the buildings in Hiroshima were destroyed by the atomic bomb.
• The debris and soot from this, mixed with the radioactive fallout from the bomb, raised high into the atmosphere in the form of a mushroom cloud.
• This material combined with the vapour in the atmosphere and came down as dark drops of liquid that have been called black rain.
• Survivors of the black rain described it as consisting of large, greasy drops that are much heavier than normal raindrops.
• It is full of highly radioactive material, and studies have shown that exposure to it can result in serious illnesses.

What was its effect?

• A study conducted in the year 1945 itself showed that black rain had come down as far as 29 km away from ground zero.
• The rain contaminated everything it came in contact with, and dead fish were reported floating in water bodies and severely ill cattle were seen lying in the fields.
• It has caused acute radiation symptoms (ARS) in many who were exposed to it, with reports of people suffering from nausea and diarrhoea for weeks.
• Other ARS include fever, sore throat and loss of hair. Over time, many people who were exposed to black rain have developed cancer.

The famous British scientist and virologist Rosalind Franklin is remembered across the world on her birth centenary who worked to construct the double-helix structure of DNA.

Try this PYQ from CSP 2019:

DNA/RNA has been an all-time favourite of UPSC!

Q.‘RNA interference (RNAi)’ technology has gained popularity in the last few years. Why?

1. It is used in developing gene-silencing therapies.
2. It can be used in developing therapies for the treatment of cancer.
3. It can be used to develop hormone replacement therapies.
4. It can be used to produce crop plants that are resistant to viral pathogens.

Select the correct answer using the code given below:

(a) 1, 2 and 4

(b) 2 and 3

(c) 1 and 3

(d) 1 and 4 only

Rosalind Franklin (1920-1958)

• She was an English chemist and X-ray crystallographer whose work was central to the understanding of the molecular structures of DNA (deoxyribonucleic acid), RNA (ribonucleic acid), viruses, coal, and graphite.
• Although her works on coal and viruses were appreciated in her lifetime, her contributions to the discovery of the structure of DNA were largely recognised posthumously.

DNA breakthrough

• In 1952, Raymond Gosling, a graduate student at King’s College London, took a historic X-ray photograph under Franklin’s supervision.
• Photo 51, as it is called, demonstrates the now-familiar, double-helix structure of DNA.

Why is she remembered now?

• The world is currently gripped in a pandemic, and her pioneering research in virology provided a crucial early step in the search for cures, vaccinations and tests.
• During the Second World War, Franklin carried out research into coal and graphite that proved important for gas-masks, the PPE of that time.
• It is because of Franklin, her collaborators and successors, that today’s researchers are able to use tools such as DNA sequencing and X-ray crystallography to investigate viruses such as COVID-10.

Back2Basics: DNA/RNA 

• Deoxyribonucleic acid (DNA) and Ribonucleic acid (RNA) are perhaps the most important molecules in cell biology, responsible for the storage and reading of genetic information that underpins all life.
• They are both linear polymers, consisting of sugars, phosphates and bases, but there are some key differences which separate the two.
• These distinctions enable the two molecules to work together and fulfil their essential roles.
• DNA encodes all genetic information and is the blueprint from which all biological life is created. And that’s only in the short-term.
• In the long-term, DNA is a storage device, a biological flash drive that allows the blueprint of life to be passed between generations.
• RNA functions as the reader that decodes this flash drive. This reading process is multi-step and there are specialized RNAs for each of these steps.

Three types of RNA

• Messenger RNA (mRNA) copies portions of genetic code; a process called transcription and transports these copies to ribosomes, which are the cellular factories that facilitate the production of proteins from this code.
• Transfer RNA (tRNA) is responsible for bringing amino acids, basic protein building blocks, to these protein factories, in response to the coded instructions introduced by the mRNA. This protein-building process is called translation.
• Finally, Ribosomal RNA (rRNA) is a component of the ribosome factory itself without which protein production would not occur.

The indigenously designed 700 MWe reactor at the Kakrapar Atomic Power Project has achieved Criticality.

Try this PYQ from CSP 2013:

Q. The known forces of nature can be divided into four classes, viz, gravity, electromagnetism, weak nuclear force and strong nuclear force. With reference to them, which one of the following statements is not correct?

(a) Gravity is the strongest of the four

(b) Electromagnetism act only on particles with an electric charge

(c) Weak nuclear force causes radioactivity

(d) Strong nuclear force holds protons and neutrons inside the nuclear of an atom.

What is ‘Criticality’ in Atomic/Nuclear Power Plants?

• Reactors are the heart of an atomic power plant, where a controlled nuclear fission reaction takes place that produces heat, which is used to generate steam that then spins a turbine to create electricity.
• Fission is a process in which the nucleus of an atom splits into two or smaller nuclei, and usually some by-product particles.
• When the nucleus splits, the kinetic energy of the fission fragments is transferred to other atoms in the fuel as heat energy, which is eventually used to produce steam to drive the turbines.
• For every fission event, if at least one of the emitted neutrons on average causes fission, a self-sustaining chain reaction will take place.
• A nuclear reactor achieves criticality when each fission event releases a sufficient number of neutrons to sustain an ongoing series of reactions.

Controlling Criticality

• When a reactor is starting up, the number of neutrons is increased slowly in a controlled manner. Neutron-absorbing control rods in the reactor core are used to calibrate neutron production.
• The control rods are made from neutron-absorbing elements such as cadmium, boron, or hafnium.
• The deeper the rods are lowered into the reactor core, the more neutrons the rods absorb and the less fission occurs.
• Technicians pull up or lower down the control rods into the reactor core depending on whether more or less fission, neutron production, and power are desired.
• If a malfunction occurs, technicians can remotely plunge control rods into the reactor core to quickly soak up neutrons and shut down the nuclear reaction.

Why is this achievement significant?

• It is the biggest indigenously developed variant of the Pressurized Heavy Water Reactor (PHWR).
• The PHWRs, which use natural uranium as fuel and heavy water as moderator, is the mainstay of India’s nuclear reactor fleet.
• Until now, the biggest reactor size of the indigenous design was the 540 MWe PHWR, two of which have been deployed in Tarapur, Maharashtra.
• India works to ramp up its existing nuclear power capacity of 6,780 MWe to 22,480 MWe by 2031.
• The 700MWe capacity constitutes the biggest component of the expansion plan.

Back2Basics: India’s PHWR technology

• PHWR technology started in India in the late 1960s with the construction of the first 220 MWe reactor, Rajasthan Atomic Power Station, RAPS-1 under the joint Indo-Canadian nuclear co-operation.
• Canada supplied all the main equipment for this first unit, while India retained responsibility for construction, installation, and commissioning.
• For the second unit (RAPS-2), import content was reduced considerably, and indigenization was undertaken for major equipment.
• Following the withdrawal of Canadian support in 1974 after Pokhran-1, Indian nuclear engineers completed the construction, and the plant was made operational with a majority of components being made in India.