IGCAR work may allow doctors to ‘see’ a fever

IGCAR - Ferrofluid-Optimized

Zaibudeen (left) and John Philip have developed a thermally tunable ferrofluid grating to measure body temperature.

Visual, non-invasive monitoring of body temperature of patients in hospitals without using a thermometer may become a reality thanks to the work carried out by a team of scientists led by Dr. John Philip, Head of the SMART section at the Indira Gandhi Centre for Atomic Research (IGCAR), Kalpakkam near Chennai. The concept is based on ferrofluid emulsion contained in a thin film that changes colour with rise in temperature within a narrow range — 30-40 degree C. The results were published in the journal Optical Materials.

The emulsion has iron oxide nanoparticles-containing oil droplets dispersed in water. The stimuli-responsive materials change in their properties to stimulus such as stress, temperature, moisture, or magnetism. “Till now ferrofluid was used as a magnetic stimuli-responsive material and we have come up with several applications such as hermetic seal, optical filters and defect detection. We now found that in the presence of a temperature-sensitive polymer — poly(N-isopropylacrylamide or PNIPAM) — the ferrofluid emulsion can be used as a thermally tunable grating to produce different colours,” says Dr. Philip.

“Recently, we were looking at the interaction forces between droplets covered with thermoresponsive polymers. To our surprise, we found that the adsorbed polymer swells and collapse upon changing the temperature between 32 and 36 degree C. This change was clearly manifested as colour change. From this observation came the novel idea of using PNIPAM-stabilized emulsions as a multistimulii grating. This is a first-of-its-kind approach where the grating spacing can be tuned either by changing the temperature or by changing the magnetic field strength,” says Dr. Philip.

IMG_0501

When the temperature rises, the monomers come closer together, changing the colour from orange to yellow.

Up to about 34 degree C, the polymer is highly hydrated and swollen due to repulsive interaction between individual monomer segments. But when the temperature crosses 34 degree C, the polymer becomes dehydrated leading to a collapsed state (due to inter and intra attractive forces between monomers). The polymer can once again become hydrated and swollen when the temperature falls below 34 degree C. “By using certain additives, we can tune the collapse of the polymer to higher temperature to reflect fever conditions,” clarifies A.W. Zaibudeen, senior research fellow and the first author of the paper.

Using magnetic field, the scientists first achieved a particular ordering (spacing between the arrays of emulsion droplets) of emulsion and got a specific colour. When the polymer is added as a stabiliser and the temperature is increased the grating spacing of the polymer changes and gives rise to a different colour or spacing.

“The colour given off at normal temperature can be fixed by changing the emulsion property and magnetic field strength,” Dr. Philip says. If yellow is chosen to represent normal temperature, it will change to green when the temperature increases. Colour with higher wavelength is produced at lower temperature and colour of lower wavelength at higher temperature.

The researchers see numerous applications for their gratings — visual manifestation of environmental conditions (temperature and humidity) and selection of a particular colour from white light. In addition, there other potential specialised applications such as calorimetric sensors, photonic materials, optical devices and drug delivery systems. “I believe that once the proof of concept is demonstrated, the scientific community would come up with many more new ideas for practical applications,” Dr. Philip says.

Published in The Hindu on April 11, 2017

IGCAR: Hydrogen sensor for greater safety

Hydrogen sensor - IGCAR

The use of liquid sodium as a coolant in fast breeder reactors has been made safer, thanks to a sensor — electrochemical hydrogen meter — developed by scientists at the Indira Gandhi Centre for Atomic Research (IGCAR), Kalpakkam, off Chennai. The sensor has been thoroughly tested at IGCAR; it was also tested at the Phenix fast breeder reactor in France.

“It was first tested in Phenix in 2009 for one year,” said T. Gnanasekaran, Raja Ramanna Fellow at the Chemistry Group, IGCAR. “Now another sensor has been installed a few days ago in one of the experimental sodium loops in Cadarache, France.”

Liquid sodium metal, not water, is used for extracting heat from the extremely hot core (where nuclear fission takes place) of a breeder reactor. Aside from other properties, liquid sodium has excellent heat transfer properties compared with water.

The liquid metal at about 550 degree C transfers the heat to water in the secondary circuit to generate steam; the steam eventually runs the turbine. Any large-scale mixing of sodium and steam should be prevented as it can lead to explosive events.

The pressure on the sodium side is low (1 bar) as the liquid sodium is at an operating temperature of 550 degree C, well below the 883 degree C boiling point. However, at about 160 bar, the pressure on the steam side is very high. But all that separates sodium and steam is a thin (4-5 mm) ferretic steel tube through which steam flows.

There is a possibility, even if remote, of tube failure. Steam, which is at a higher pressure than sodium, tends to leak into the coolant when the tube develops a leak. On reaction with sodium, hydrogen and sodium hydroxide are formed. Sodium hydroxide, which is a caustic material, further aggravates the problem. Due to its low melting point, sodium hydroxide turns into a molten material at the site of the crack causing further corrosion of the tube.

“Continuous monitoring for any steam leak even at its inception is therefore extremely important,” he pointed out. Since the operating temperature of sodium is high, hydrogen and other reaction products get dissolved in it. Hence the presence of dissolved hydrogen in sodium is continuously monitored to detect the initiation of a leak. “If undetected at the micro and small leak stages, steam leaks can develop into a large leak and lead to explosive events,” Dr. Gnanasekaran pointed out.

“Hydrogen level in sodium will shoot up even if a small amount of steam leaks into the coolant. Our sensor can measure dissolved hydrogen down to 70 parts per billion (ppb) in sodium,” he said.

The sensor is able to detect dissolved hydrogen at extremely low levels as it uses a high temperature hydride ion-conducting solid electrolyte. “Solid electrolytes conduct by ions,” he said. Only a few solid electrolytes are known. “But a hydride ion-conducting solid electrolyte is needed for measuring dissolved hydrogen concentration in sodium at elevated temperatures,” Dr. Gnanasekaran explained. “Such an electrolyte was not available.”

This forced the IGCAR scientists to develop a hydride ion-conducting solid electrolyte. They used a reference electrode and the solid electrolyte to construct the sensor — electrochemical galvanic cell. “The cell [sensor] gives an electrical output depending on the dissolved hydrogen concentration in sodium,” Dr. Gnanasekaran explained. “The critical component is the solid electrolyte.”

The sensor kept at the outlet of the steam generator is a lot more robust and inexpensive than the sensor used earlier. Several sensors can be introduced at different locations of the steam generator to increase the sensitivity.

Published in The Hindu on April 25, 2013

Hybrid desalination plant at Kalpakkam

Published in The Hindu on December 6, 2012

Desalination - R. Prasad

Water continues to flash evaporate even at 40 degrees C in the case of the Multi-Stage Flash (MSF) desalination technology.— Photo: R. Prasad

“The Nuclear Desalination Demonstration Plant (NDDP) located at Kalpakkam [off Chennai], Tamil Nadu, is the world’s largest hybrid seawater desalination plant coupled to an existing nuclear power plant,” says Dr. P.K Tewari, Head, Desalination Division, BARC, Mumbai.

Coupled to MAPS

This desalination facility is coupled to the Madras Atomic Power Station (MAPS), and deploys both multi-stage flash (MSF) evaporation and reverse osmosis (RO) membrane separation technologies. The total capacity of NDDP is 6.3 million litres per day (MLD).

Multi-Stage Flash (MSF) evaporation plant produces 4.5 million litres per day of distilled quality water and Reverse Osmosis (RO) plant produces 1.8 million litres per day of potable-quality water. The desalination plant meets the entire pure water requirement of Madras Atomic Power Station (MAPS).

“The multi-stage flash technology works on the principle of flash evaporation wherein the temperature of water is increased under pressure and then flash evaporated by reducing the pressure gradually in multiple stages,” said Shri. M.M. Rajput, Plant Superintendent, NDDP, BARC Facilities, Kalpakkam.

In steps

In MSF plant, by increasing the pressure of water by 2 bar, the boiling point temperature of water is raised up to 121 degree C. The superheated water is then allowed to cool in steps of 2 degree C at each of 39 stages, and the water is allowed to flash evaporate and condense as pure water by reducing the pressure.

Small part of the low pressure steam (at 130 degree C) that goes from MAPS’ high pressure turbine to low pressure turbine is used for heating the sea water. “The pressure drop across the flashing stages will be more at the initial stages and reduces gradually with decreasing temperature,” said Shri. C. Balasubramaniyan, Deputy Plant Superintendent, NDDP, BARC Facilities, Kalpakkam. “Temperature drop from 119 degree C to 117 degree C is achieved by reducing the pressure by 1,300 mm water column. But at the lowest temperatures, say 42 degree C to 40 degree C, the pressure drop will be only 100 mm water column.”

In short, when the pressure drops, the boiling point of seawater also drops. The excess heat, in turn, causes seawater to flash evaporate into pure water vapour. The water vapour is then condensed to produce distilled water.

The challenge

But the challenge in MSF plant comes from making the water flash in 39 stages through a small and controlled temperature drop of just 2 degrees per stage. So much so, that water continues to flash even when the temperature reaches as low as 40 degrees C at 39th stage — the last and final stage!

But how does water continue to flash evaporate even when the temperature is as low as 40 degree C? If initially, increasing the pressure helped in increasing the boiling temperature, reducing the pressure at later stages helps in reducing the boiling temperature. “From the 10th stage onwards, flashing is achieved under progressively increasing vacuum,” explained Shri. Balasubramaniyan. “By reducing the pressure, the water continues to flash evaporate at lower temperature.” Hence at the last stage, vacuum is in the order of -0.95 bar(g), and this helps in evaporating the seawater at 40 degree C.

“If the entire quantity of superheated water is allowed to flash and produce steam at one instant, the amount of water produced will be several times less than multi-stage flashing,” Shri. Rajput explained.

In the MSF plant, the scientists have achieved production of more than 9 kg of water from every kilogram of steam produced.

This has become possible as the system is designed to recover most of the heat internally. As the superheated seawater continues to lose temperature at every stage of flashing, the incoming sea water used for condensing the steam, in turn, gains heat. “The sea water used for condensing the steam gets heated to 113 degree C by the time it leaves the heat recovery stages,” said Shri. Rajput. “The temperature of the seawater has to be raised by a mere 8 degree C (from 113 degree C to 121 degree C) before it is flashed multi times to produce distilled water.”

“The cost of producing distilled water using MSF technology is 10 paisa per litre, and 6 paisa per litre in the case of reverse osmosis,” noted Shri Amitava Roy Facility Director, BARC Facilities at Kalpakkam. This is after factoring in the cost of power, steam, chemicals, maintenance and depreciation.

“We can set-up a similar plant in three to four years,” said Dr. Tewari. “and whatever be the temperature of steam the plant can be designed to produce distilled water.”

‘Our policy is to reprocess all the fuel put into a nuclear reactor’

Published in The Hindu on October 28, 2012 SEKHAR BASU - R. Prasad

‘India is one of the countries doing a lot of work on a scientific solution to waste management,’ says Dr. Sekhar Basu, Director of the Bhabha Atomic Research Centre. = Photo: R. Prasad

Post the Fukushima disaster, one of the key issues protesters raise is nuclear waste generated by a nuclear plant and its final disposal. Sekhar Basu, Director, Bhabha Atomic Research Centre (BARC) speaks to R. Prasad about nuclear waste generation, reprocessing and final disposal.

Post the Fukushima disaster, one of the key issues protesters raise is nuclear waste generated by a nuclear plant and its final disposal. Sekhar Basu, Director, Bhabha Atomic Research Centre (BARC), Mumbai, has worked extensively on several aspects of nuclear reprocessing and waste management. As Chief Executive of the Nuclear Recycle Board, he is responsible for the design, development, construction and operation of nuclear recycle plants involving reprocessing and waste management. He has designed and built reprocessing plants, fuel storage facilities and nuclear waste treatment facilities at Trombay, Tarapur and Kalpakkam. He has taken up the design of the first Integrated Nuclear Recycle Plant which will take the nuclear recycle programme to maturity. He spoke to R. Prasad about nuclear waste generation, reprocessing and final disposal. Excerpts.

What is the amount of nuclear waste generated compared with coal power plants?

The nuclear energy programme will move in parallel paths. One is to produce power. Since we generate power there will be some waste. And this waste is only two to three per cent of the total fuel we put into the reactor. Entire spent fuel is not waste; plutonium and uranium are recycled which contribute to about 97-98 per cent of the spent fuel. So only the remaining two to three per cent of spent fuel is waste. This is unlike our coal power stations where whatever coal you put into the plant turns into waste (like ash) and other emissions.

The second part is the amount of coal that has to go into a power station for the same capacity. If we compare it with nuclear power plants, uranium requirement is about 30,000 times less. So the amount of coal we carry to make a power station of some capacity is much more. All I am saying is that in terms of waste volume there is no comparison between coal and nuclear power stations.

But will not nuclear waste remain radioactive for a long time?

Now the problem with nuclear power waste is that it will remain radioactive for a few hundreds of years and even more. Now again you see, this waste can be divided into two parts — one where within 300 years, 99 per cent of the waste becomes non-radioactive and the rest is going to remain radioactive for a longer time.

So we are working towards the development of a process where we can separate waste that becomes non-radioactive within 300 years.

At what stage of development is the technology to separate waste which is radioactive for about 300 years and that beyond 300 years?

A pilot plant will become operational [to separate the two types of waste] next year. Process development in the lab was completed some time back. The pilot plant will be followed by a demonstration plant, and then by commercial plants.

Where is the pilot plant coming up?

Tarapur, Mumbai.

When will the demonstration plant come up?

In our case, after the pilot plant is fully operational, we will come up with a demonstration-scale plant at Tarapur. It is at a design stage and will be integrated to the nuclear recycle plant at Tarapur. This will be a large-sized plant. The plant will be designed for reprocessing 600 tonnes of spent fuel.

How do you take care of the waste that will become non-radioactive within 300 years?

Taking care of the waste that remains radioactive for about 300 years is not of much concern. Properly designed buildings and structures can stand for 300 years.

The waste is first vitrified in the vitrification plant operational in India. It will be put in steel canisters, which in turn will be put in steel over-packs. Over-packs will again be put in another steel casing. So there will be three to four layers of steel casing in addition to vitrification. It will finally be kept in concrete structures/buildings. Concrete buildings are used for structural, shielding and ventilation purposes.

Whereas when it is beyond 300 years some other methods are necessary. That is why we talk of putting them in repositories.

So the waste that becomes non-radioactive within 300 years will not go into repositories?

No, that is not essential if we are able to separate it from the long-lived ones.

There is waste; there is long-lived radioactive waste. But it is a very small quantity. So taking care of that should not be much of a problem.

Have you identified a location for repositories for waste that will be radioactive beyond 300 years?

If you see the Indian map, we have granite rock formation spread all over the country. So it can come up anywhere wherever the rock formation is suitable.

We need to identify a site and people should be convinced that there is no real problem. Then this will be possible. Today somehow the atmosphere is different. We can only continue our research for identification of a location.

So anywhere you have granite rocks of proper quality, they will be studied. During the studies, you look for some evidence for lack of migration. So you take a rock sample and see for water or other elements that have stayed over there for a very long time.

Is there another way of handling long-lived radioactive waste?

We can bombard the waste with high-energy neutrons to kill or burn radioactive elements. This is called transmutation. Transmutation is the way of handling actinides that have long half-lives. It can be done either in faster spectrum reactors where neutrons of higher energy are used or accelerator-driven system (ADS).

What do you mean by burning?

Burning means you bombard radioactive elements having longer half-lives with high-energy neutrons and convert them into some other elements that will have much shorter half-lives thereby mitigating the concerns of long-lived radiotoxicity. So if you have a large reactor programme, you can have a reactor specifically for burning the waste. It can be done either in fast spectrum reactors or an ADS. This is the scientific solution to waste management. India is one of the countries doing a lot of work on this.

How close are we to reaching this goal?

We already have fast reactors, so we will be only extending the technology. The ADS programme is being taken up in a big way in the 12th Plan. We have started pursuing it and Visakhapatnam is the place for the ADS programme. It will take 15 to 20 years to come up because multiple technologies are involved.

When will the Integrated Nuclear Recycle Plant come up?

Right now it is at a sanction stage; a proposal is with the government for sanction. Somewhere in 2020 the project should come up.

Our policy is to reprocess all the fuel that we put into a reactor. Reprocessing and waste management will follow the main reactor programme. There will be a gap of up to 10 years because the fuel has to take some time to cool. So far, the reprocessing programme was smaller, but we will expand it as the reactor programme is expanding.

Are you expanding the reprocessing plant capacity?

We are almost doubling the [reprocessing plant] capacity at Kalpakkam [near Chennai]. The Kalpakkam plant will reprocess fuel from [reactors based in] South [India] and is likely to be operational by 2014.

IGCAR develops sensors to inspect defects in materials

Detecting and imaging structural defects like cracks, holes etc, present in components made of ferromagnetic materials like pipelines, railway tracks and tubes has now become easy with optical sensors. These sensors were developed by Dr. John Philip and his team at the Indira Gandhi Centre for Atomic Research (IGCAR), Kalpakkam near Chennai. The results of their work were published recently in the journal Applied Physics Letters.

The work provides a “methodology for extracting defect feature information from optical images,” notes the paper.

The optical sensor has oil droplets (about 200 nanometres in diameter) containing a few nanoparticles of magnetic materials, about 6.5 nanometres in size. The oil droplets are present as an emulsion with water.

Since the sensor contains magnetic particles, it responds to magnetic fields. “The sensor is magnetically polarizable,” said Dr. Philip, Head of SMART Section at IGCAR. He is the senior author of the paper.

The sensor works on the principle that defective regions in a material produce magnetic resistance, and this in turn leads to leakage of magnetic flux (field lines). “The leakage of magnetic flux will be right outside the point where the defect in the material is present,” Dr. Philip explained. “The nanofluid-based optical sensor can detect such leakages.”

The material whose structural integrity is to be evaluated has to be first magnetised. This can be done by using two strong magnets kept on either ends of the material to be tested. The sensor, which is sandwiched between two glass plates, is kept on top of the magnetised material. The sensor is then illuminated with white light.

Magnetic flux passes through the material the moment it is magnetised. The magnetic flux leaks if the material has any structural defects, and the nanofluid inside the optical sensor immediately forms an one dimensional array or chain along the direction of the magnetic field. “When it forms an one dimensional array, the spacing between the droplets satisfies the criterion to diffract one particular colour in white light,” he said.

The colour that is diffracted or reflected depends on the inter-droplet spacing. “When the defect is large, the magnetic flux leakage is more, and the spacing between the droplets is smaller. The reflected colour is violet,” he explained. Alternatively, if the defect is small, the spacing between the droplets is more and the reflected light is red or orange.

While the optical sensor can provide the result immediately, the dimension of the defect can be found using certain modelling. “We can map different shapes (geometry) of the defects,” Dr. Philip said.

“Future perspectives include the fabrication of large flexible films for the inspection of large components and development of suitable pattern recognition software for rapid inspection of components,” the paper notes.

Advantages

The sensor has several advantages over existing techniques. For instance, the optical sensor can be repeatedly used as the one-dimensional array formed in the nanofluid is “perfectly reversible.”

“It takes less time to detect flaws in the material, allows direct visual inspection of the defects, and does not destroy the material being tested,” he explained. “The sensors are very cheap — a one inch by one inch sensor would cost just a few hundred rupees.”

Published in The Hindu on March 22, 2012

Detecting breast cancer using thermal imaging

Published in The Hindu on July 9, 2009

Screening to detect breast cancer early may become a reality if thermography (thermal imaging) that is in the early stages of testing is perfected. The trial is jointly done by the Indira Gandhi Centre for Atomic Research (IGCAR), Kalpakkam and the Chennai based Sri Ramachandra Medical College (SRMC).

Thermography detects infrared radiation emitted by a body, and the wavelength of the infrared radiation is correlated to the temperature.

“Any cancerous/abnormal cells will cause increased blood flow. Increased blood flow results in increased temperature. Thermogrpahy looks for such increase in temperature in any part of the breast,” said Dr. B. Venkatraman, Head, Quality Assurance Division at IGCAR.

However, not all cells that exhibit an increased temperature due to increased blood flow are cancerous. Hence its ability to identify all cancerous cells and only the cancerous cells is crucial.

The performance and ability of thermography to detect breast cancer were first tested on 25 patients who had come to the Department of Atomic Energy Hospital at Kalpakkam with pain/indication of breast cancer.

The clinical standardisation (determining the ambient temperature at which the screening should be done etc) has already been done at SRMC.

Results from thermography were compared with mammography and tissue biopsy in nearly 200 patients. Patients above the age of 40 and who complained of pain in the breast were chosen.

High sensitivity

“The sensitivity is about 98 per cent (ability to detect positive cases) and the specificity (ability to pick up only the positive cases) is 88-90 per cent,” said Dr. P. Surendran, Associate Professor in General Surgery, SRMC. The sensitivity and specificity were derived during the process of clinical standardisation.

According to him, the specificity is as high as 96 per cent in well established breast cancers and about 85 per cent in the case of early lesions (about 1 cm size).

Following the clinical standardisation, thermography has been used on 60 patients at SRMC. The analytical standardisation — to know which cells/areas exhibiting abnormal temperature are actually cancerous — is in progress. Analytical standardisation would help provide accurate information of the sensitivity and specificity.

“What we have done now is to see if thermography can be more sensitive than mammography, so we can pick up cases at a much earlier stage and confirm it with mammography and tissue biopsy,” said Dr. S.P. Thiagarajan, Director of Medical Research at Ramachandra University.

It will be an ideal and a superior tool for screening compared with mammography if the specificity is also high. For instance, unlike mammography, thermography detects breast cancer non-invasively.

Several advantages

There are several other advantages as well. Patients are not subjected to any radiation, it is not expensive, is a painless procedure, and can be done quickly.

But the most important advantage is that thermography can pick up cancerous/abnormal cells immaterial of the age of patient and the type of breast. “Mammography cannot pick up smaller lesions in younger patients [less than 40 years] and when the breast density is high. That is its biggest disadvantage,” said Dr. Surendran. “Mammography is useful in older patients and smaller breasts.”

“Our aim is to perfect it so we can use it as a screening tool in rural settings,” said Dr. Baldev Raj, Director of IGCAR. It is, however, too early to say that thermography can be used as a screening tool. But it will surely turn out to be an invaluable tool if the specificity issue is addressed.

PFBR: novel steel reduces power generation cost

Published in The Hindu on March 12, 2009

The Indira Gandhi Centre for Atomic Research (IGCAR) at Kalpakkam has achieved a major breakthrough that would allow it to generate power at 30 paisa per unit less 4-5 years after the Prototype Fast Breeder Reactor (PFBR), which is under construction, is commissioned.

The PFBR is expected to be commissioned in September 2010, and the cost of a unit of power at the time of commissioning will be Rs.3.22 per unit.

Increased burn-up

“We have developed advanced steel that will allow us to increase the burn-up [the amount of energy extracted from a unit mass of fuel] of the mixed oxide fuel by 100 per cent,” said Dr. Baldev Raj, Director of IGCAR.

The current burn-up target for the mixed oxide fuel that will be used in PFBR is 1,00,000 MWdays/tonne. The new steel would allow the burn-up to be increased up to 2,00,000 MWdays/tonne.

Dr. Raj had told this Correspondent last year (The Hindu, May 1, 2008) that the Centre was working to develop a new kind of steel that would allow it to increase the burn-up.

Unlike in the case of the mixed carbide fuel used in the Fast Breeder Test Reactor (FBTR), the physical and chemical changes that the oxide fuel undergoes during irradiation do not affect the steel that encases it.

So scientists looked at improving the steel so that it does not get damaged by high energy neutron bombardment inside the reactor.

The significance

In essence, it would mean that the new kind of steel (in which the fuel is kept) that the scientists have developed would allow better utilisation of fuel by extracting more energy from a given quantity of fuel.

“The bigger a reactor, the greater would be the leverage of high burn-up, and this would result in more reduction in unit cost of power,” he said.

The IGCAR scientists, along with the Hyderabad based Nuclear Fuel Complex and Advanced Materials Research Centre, Hyderabad, have used nanosized yttria element dispersed in steel to produce this special product.

The special yttria steel does not undergo swelling and creeping even under continuous high energy neutron bombardment at high temperature.

Changing the dynamics

This becomes possible as yttria changes the dynamics of the defects produced by neutron irradiation. Certain physical changes that causes steel to swell are thus prevented. This allows increased extraction of energy from a unit mass of fuel.

The scientists have studied the microstructure and other characteristics of the steel. The actual testing would begin soon. “We would put the steel in the FBTR [for testing] in a few months’ time,” Dr. Raj said.

“Since it would take about 6-7 years to reach 2,00,000 MWdays/tonne burn-up in the FBTR, we will do an accelerated testing in an accelerator.”

Testing in an accelerator is expected to start soon. They would have the results in three months’ time.

The biggest challenge, according to the Director, was to extrude the new steel into a tube without introducing any physical weaknesses such as cracks and porosity.

Now that the scientists have succeeded in developing steel that will allow the burn-up to be doubled, are they working on producing an even better one? Though it may be possible to develop better steel, the challenge lies elsewhere.

The limiting factor

According to Dr. Raj, the limiting factor would come from reprocessing of the spent fuel that has undergone more than 2,00,000 MWdays/tonne burn-up and a shorter cooling period.

Fuel removed from a reactor cannot be reprocessed immediately as it would be hot and would have residual radioactivity. Hence it should be allowed to cool down.

“It is not a challenge to reprocess spent fuel up to 2,00,000 MWdays/tonne burn-up,” he said.

Other advantages

Apart from the better utilisation of fuel and thus reducing the cost of power generation, increasing the burn-up would translate to lesser fuel being used and thus reduced nuclear waste production.