Extract from the updated ICRP document (ICRP-146, 2010)

There is an updated latest ICRP document entitled Radiological Protection of people and the environment in the event of a large nuclear accident published by the ICRP as the Publication No. 146 (2020). The document is the updated versions of ICRP – 109 and ICRP- 111, which cover emergency exposure situations. This new document provides a much needed framework for protection of people and the environment in Chernobyl and Fukushima line reactor disasters. 

The early and intermediate phases of accidents are considered as Emergency exposure situations and the long-term phase is considered as existing exposure situations (ICRP-103). Mitigating the radiological consequences on the humans and the environment are achieved by the justification and optimization principles as discussed in the ICRP. A set of reference levels are recommended for protection of general population, and for the protection of all concerned in the mitigation process. The concerned authorities at national and local level are responsible for implementing radiation monitoring and surveillance programs. The authorities also are responsible to involve all the stakeholders in the emergency preparedness process and management of the successive phases of the accident.  

Non-Cancer effects of radiation exposure

 

International Commission on Radiological Protection (ICRP) revised its 1990 Recommendations (1991) in the form of “2007 Recommendations of the ICRP” (2007).

 

The fundamental principles of radiological protection in the revised System of Radiological Protection are: Justification, optimization and application of dose limits are apply to all exposures to ionizing radiation from any source. The total harm to health experienced by the exposed group of persons and its descendants as a result of the doses received is termed as detriment. The detriment takes into account the stochastic quantities.

 

However, the research over the years also indicates stroke and heart disease may well be caused by chronic or acute radiation exposure at doses of the order of 0.5 Gy or less.

 

Now the acceptance of this non-cancer detriment in the risk assessment by the ICRP may change the protection strategies in the future?  

Nuclear desalination of sea water

India, particularly during summer months always face acute water shortage. Now with large scale usage of water for the management of Corona Virus, it is likely that the shortage can be more acute, and we may not get enough water for the cleaning. Most parts of India depend entirely on the rains for the supply of water for all purposes. Let us hope that the rains come early this time and save the situation. Let us wish Corona goes away before the rainy season starts.

We, in India, have over 7500 km of coastline and hence plenty of seawater. Desalination is the answer to deal with this situation. Technology is available for the desalination of seawater. Nuclear desalination can be the answer to augment freshwater supply. We must work out the costs.

Nuclear forensics - An important tool

Illicit trafficking of radioactive or nuclear material is of great concern internationally due to its potential application by terrorist groups. Nuclear forensics examination is the analysis of nuclear and other radioactive materials to identify the sources and support national or international legal issues related to nuclear security.

In general, national or international laws prohibit unauthorized or illegal movement or transport of nuclear or radioactive materials across national borders. The smuggled radioactive material and which is out of the regulatory control can be misused in nuclear crimes.

The materials seized in such situations need to be examined by dedicated laboratories to support the law enforcement authorities for prosecution of a breach in the security of such materials. Sensitive measurement techniques will be necessary to analyze small to very small amounts of the sample. The radioactive material may be in the form of loose contamination. Techniques such as gamma spectrometry, clinical forensic medicine to detect radiation exposure specific injuries, etc.

It is also important to identify the material using validated procedures, identify the origin of the material and the potential hazard of its use in the public domain or in any other illegal activities. The results provide evidence which is necessary for successful prosecution.

National regulatory authorities and international bodies such as IAEA are much concerned about this illegal trafficking of the material. The IAEA Nuclear and Security Series bring together details, including technical characterization of the seized material samples using technical tools and the procedures adopted in nuclear forensics.

IAEA, Advances in nuclear forensics countering the evolving threat of nuclear and other radioactive the material out of regulatory control, STI/PUB/1706 [ISBN:978-92-0-104815-8], 2015.

RADIOLOGICAL PROTECTION OF THE ENVIRONMENT

In addition to the natural radiation and radioactive materials, radiation, and radioactive materials are present in the environment from the past practices of testing of nuclear weapons, large scale releases from accidents in nuclear and radiological facilities and the authorized releases from the nuclear fuel cycle facilities, including radioactive waste management facilities. Releases from the regulated facilities are well controlled to protect the environment. However, accidental releases or releases from unregulated practices are likely to harm the environment – flora and fauna. In such situations, one cannot assume that the environmental impact from the releases is negligible.

Subsequently, IAEA’s work programme on the development of safety standards on the protection of the environment from the effects of ionizing radiation culminated in the development of regulatory frame work, based on the IAEA’s policy on the radiological protection of the environment.  

ICRP in its publication 103 [2007] acknowledge the importance of protecting the environment in addition to the safety of members of the public by way of authorized discharges in planned exposure situations. To establish a framework for environmental protection in all exposure situations, like for humans. It is proposed to use Reference Animals and Plants for radiation dose assessment. However, no dose limits are not recommended. Thus, protection of the environment is identified as the issue necessitating an assessment of the impacts on the environment from a particular source(s).

 

Ref: IAEA, Radiation protection of the public and the environment, IAEA Safety Standards, General Safety Guide, GSG-8, IAEA, Vienna, 2018. 

Disposal of high level radioactive waste

High level wastes are generated in all operations involved in processing of spent nuclear fuel. At every public forum people connected with atomic energy are asked this question: How the department of atomic energy is going to manage this waste? Do we have any clear-cut answers? 

According to experts – NO is the answer.  

High level wastes are only stored under-ground.  The disposal option of burial in deep geological formations is yet to be realised in India. Why the delay is not yet answered. Any other mode of disposal is prone to be extremely unsafe in view of the possibility of occurrence of natural calamities such as tsunami, earthquake, and high floods, and attack by missiles.

Member of the public is of the opinion that the agencies concerned should give a most feasible reply of disposal of the waste in deep geological formations, and start doing it!

Rise in sea level went up since 1990s

This is the title of the news item in TOI dated June 28, 2017. What next?

The previously assumed leader of climate change deal, US President withdraws from the Paris Climate deal agreed, by over 200 nations, in December 2015. Now, the movement is without any strong leader to spearhead the compliance of the agreement by the nations.

As per the news item, the annual rate of sea level rise increased to 3.3 mm in 2014 from 2.2 mm in 1993. If it continues at the current rate it will rise to 33 mm in a century! Low lying coasts around the world will be under water.

In-spite of the melting of ice on land and the huge icebergs (floating mass of ice detached from a glacier and carried out to sea) in large quantities, the levels have arisen significantly for the simple reason that the volume created by the melting of ice is more than the volume of the water resulted from the melting of the ice. The space can easily accommodate the water without causing any rise in the sea level.

However, it is necessary that a popular and powerful leader should take up the responsibility to carry on this all important climate agreement so that the rise is contained to avoid flooding of sensitive industrial and nuclear installations which are located on the sea shores.

  

End of nuclear power? It is only the beginning!

There was a report in TOI dated 21^st may 2017 indicating that solar power is replacing nuclear power world-wide. Apparently, it may look like that, since widest possible negative publicity is given in the media for nuclear-related incidents and accidents highlighting trivial risk to the population by these occurrences. The risks are only on paper and there are hardly any fatalities related directly to the nuclear incidents/accidents, in real time.

Countries are spending disproportionately large amount of money on safety systems because mathematically some deaths can be predicted that too after two or three decades of exposures to radiation. This makes nuclear power a little more expensive than other modes of electricity generation. But things are changing fast! It is being proved that there are no observable health effects which can be directly attributed to exposure to low level radiation dose.

India should go for indigenous standardized nuclear power plants. Buy uranium from friendly countries. Reprocess spent uranium fuel to get fissile plutonium, a better nuclear fuel than uranium. Separate Cs-137 radionuclide which is the major part of the nuclear waste. Use this Cs-137 as radiation source for industrial applications, such as food irradiation or blood irradiator. The radiation safety scenario is creditable.  

Nuclear power is far less polluting than burning coal or oil in thermal power plants.

Uranium from sea water?

There was a news item in TOI dated 22 Feb. 2017 on “Harnessing N-Power from Oceans”.  Presence of naturally occurring radioactive materials like uranium and thorium in water, soil and rocks is known. However, the concentration of these materials in very low, in parts per million (ppm) or parts per billion (ppb). Recovering the elements at such low levels from such complex matrices is very difficult and not cost effective. Japanese and Indian researchers have done good amount of work in the extraction of uranium from sea water.

Uranium concentration in sea water is about 3 ppm (3 milligram of uranium in one cubic meter of sea water). If one multiplies this by the total volume of sea water, there will be billions of tons of uranium potentially available. As per Japanese study, the cost of uranium may work out to be over 300 USD per kg! May be, it can be the last desperate resort for producing uranium for power generation.

Do we have to resort this when other better options are available? Thorium is more abundant on the surface of the earth (ex. Monazite minerals on sea beaches). The thorium can be effectively utilised for power generation. India is one of the countries which extensively studied thorium fuel cycle for producing U-233 which is fissile material and can be used in nuclear reactors for producing power. Countries should focus on this instead of recovering uranium from sea water on commercial scale, at unimaginable cost.

Then there is unlimited fusion energy which can be harnessed. It is also satisfying to see the solar power being harnessed world-wide for producing electricity.  

Did you know that in Energy Sector:

1. India, home to 18% of the world’s population (1.3 billion), uses only 6% of the world’s primary energy.
2. In India, around 240 million people have no access to electricity.
3. Putting manufacturing at the heart of India’s growth model means a large rise in the energy needed to fuel India’s development.
4. Energy consumption per capita is still only around one-third of the global average.
5. Coal remains the backbone of the Indian power sector, accounting for over 70% of generation.
6. Three-quarters of Indian energy demand is met by fossil fuels, it is rising!
7. India was the world’s third-largest importer of crude oil in 2014, but is also a major exporter of oil products, thanks to a large refining sector.
8. India has 45 GW of hydropower and 23 GW of wind power capacity, but has barely tapped its huge potentials for the renewable energy.
9. The country’s electricity demand in 2013 was 897 terawatt-hours (TWh), up from 376 TWh in 2000, having risen over this period at an average annual rate of 6.9%.
10. Annual residential electricity consumption per capita in India (for those with access) – India average in 2013 was 200 kWh.
11. On the supply side, India has some 290 gigawatts5 (GW) of power generation capacity, of which coal (60%) makes up by far the largest share, followed by hydropower (15%) and natural gas (8%).
12. Primary energy demand in India by fuel is: 44% (Coal); 23% (Oil); 24% (Bio mass); 6% (Natural Gas), (1% nuclear) and 2% other renewables.
13. Oil consumption in 2014 stood at 3.8 million barrels per day (mb/d), 40% of which is used in the transportation sector. Over 90% of energy demand in the transport sector in India is from road transport.
14. India has relatively modest oil resources and most of the proven reserves (around 5.7 billion barrels) are located in the western part of the country, notably in Rajasthan and in offshore areas near Gujarat and Maharashtra.
15. Wind power has made the fastest progress and provides the largest share of modern non-hydro renewable energy in power generation to date. India has the fifth-largest amount of installed wind power capacity in the world.
16. Solar power has played only a limited role in power generation thus far, with installed capacity reaching 3.7 GW in 2014. The target for wind power was dramatically upgraded in 2014 to 100 GW of solar installations by 2022,
17. Nuclear power played a very limited role (1%) in the power sector. India has twenty-one operating nuclear reactors at seven sites, with a total installed capacity close to 6 GW. Another six nuclear power plants are under construction, which will add around 4 GW to the total. The average plant load factor rose to over 80% in 2013 from 40% in 2008.
18. India has 13 of the world’s 20 most-polluted cities and an estimated 660 million people in areas in which the government’s own national air quality standards are not met. (Extracted from International Energy Agency's Special report 2015) 

Non-proliferation Treaty and India-Japan nuclear deal

Non-proliferation treaty (NPT) of nuclear weapons is an international treaty entered into force in 1970. The main objective of the Treaty is to prevent the spread of nuclear weapons and technology, and to promote peaceful uses of nuclear energy. A total of 191 states have joined the Treaty and four stats, viz., India, Pakistan, Israel and South Sudan never joined the Treaty. The Treaty recognizes only 5 states as nuclear-weapon states. They are US, Russia, UK, France and China. 

Japan is the only country which suffered attacks by nuclear weapons and is very particular that the treaty is respected by all the countries. India is not a signatory to the NPT and wants to strike a nuclear deal with Japan.

During the negotiations, Japan is putting forward conditions such as: tracking of the nuclear fuel, accounting and tight management of plutonium generated by reprocessing the spent fuel and clauses in the India’s Civil Liability for Nuclear Damage Act (CLND)-2010.

The clause of Part liability of nuclear plant manufacturers in the event of nuclear accidents in a matter another concern for Japan. Management of nuclear accidents and mitigation measures are very highly cost-intensive and even though the government is planning special insurance to cover the huge expenditure involved, are the insurance companies are able to cope up with the claims? Finally, will Japan will do nuclear business with India which is now a nuclear-armed country and not a signatory to NPT? 

Nuclear desalination of sea water is THE answer

Nuclear desalination is the answer for the world-wide short supply of potable water. One-fifth of the world’s population does not have access to safe drinking water! Without water, one cannot imagine any sustainable development taking place. Brackish or sea water and treatment of urban waste water can be converted to fresh water by nuclear desalination.  

Use of nuclear energy is a much cost competitive method as compared to fossil fuels for desalination, and it has a great potential. Desalination of sea water is used in Middle East and North African countries. Many countries already are into this technology for producing potable water.  China is building 1 million cubic meter per day RO plant to supply water to Beijing. The International Atomic Energy Agency (IAEA) is fostering research and collaboration in the technology in its Member States.

One of the impotent cost-effective technologies used for desalination is Reverse Osmosis (RO). Using electric pumps, sea water is pressurized and forced through semi-permeable membrane against its osmotic pressure. The salt content of the water gets removed. The process is driven by electricity driven pumps. However, the feed water needs to be filtered in this technique. High operating pressure of the order of 55 to 82 bars are required for desalination of sea water. As proved by Australia, renewable energy (CO₂ free) sources can be used for desalination.

Multi-stage flash (MSF) distillation process uses steam. It works by flashing a portion of the water into steam in multiple stages in counter-current heat exchangers and this method for desalination accounted for 23% of the world capacity in 2012. It is more energy intensive process, but can cope with suspended solids and any degree of salinity. There are many other processes such as Multiple-effect distillation (MED) that can be used for desalination

Nuclear desalination studies using small and medium sized nuclear reactors are carried out in US and France. IAEA reports, based on the IAEA Coordinated Research Programs in Kazakhstan, India and Japan, are available which give details on nuclear desalination of sea water. Indicative costs are US$ 70 – 90 cents/cubic metre.

In India, Bhabha Atomic Research Centre (BARC) has undertaken extensive research in the field of nuclear desalination since the 1970s, and thermal desalination process, Multi Stage Flash (MSF) and Reverse Osmosis (RO) process were successfully demonstrated. A demonstration scale hybrid MSF-RO desalination plant coupled to a nuclear power plant at MAPS, Kalpakkam (Tamilnadu) is designed to provide around 6300 cubic metre of desalted water per day. Low pressure steam is gainfully used here. A mechanical vapour compression plant is reported to be set up at Kudankulam (Tamilnadu) to supply fresh water for the plant’s requirement of cooling water.

A low temperature nuclear desalination plant uses decay heat from radioactive waste for desalination. Heat from the high-level waste packages seems to have great potential to meet the requirement of nuclear desalination. Instead of disposal in geological repositories, the decay heat from the high level waste should be utilised to meet heating and steam requirements of a desalination plant. The potable water thus produced can be used at all the nuclear sites and residential areas in coastal areas of India.   

Radiation technology for cleaning of air pollution

IAEA supported project in Poland employs a radiation technology – electron beam accelerator facility to treat flue gases from coal-driven power plants, thus reducing the emissions of sulphur dioxide, nitrogen oxides and polycyclic aromatic hydrocarbons, which can cause damage human health and the environment. Acid rains in and around the site are the result of the acidic pollutants.   

The technology is useful in countries which produce electricity by coal/oil combustion and required to meet pollution control regulations. Unlike other conventional technologies, the use of electron beam accelerator technology removes 95% of sulphur dioxide, and 70% of nitrogen oxides present in flue gases. The by-product is high quality fertilizer for use in agriculture. Not much of secondary waste! 

It is a proven green technology according to the Director General of the Institute of Nuclear Chemistry and Technology, Poland (source: www.iaea.org) 

Billions of dollars’ nuclear industry's predicament?

BIER Report VII: Biologic Effects of Ionizing Radiation (BEIR) develops the most up-to-date and comprehensive risk estimates for cancer due to exposure to radiation.

The report which gives results of the life time cancer risk calculation using mathematical models from an exposure of 100 mSv dose to a typical US population. The calculations predicted one individual in 100 persons would be expected to develop solid cancer or leukemia. This can be compared with the expected 42 cancer cases that would be developed in 100 persons spontaneously due to other causes!

Risk is lower at lower exposures. Similar calculations for a lower dose of 10 mSv predict one out of 1000 exposed individual would develop cancer. However, it is very difficult due to statistical limitations, to predict reliable number of cancers at these low levels of exposure. Now, 100 mSv is the occupational dose limit for radiation workers for 5-year period, average of 20 mSv per year. The world average natural background radiation is 2.4 mSv in a year to which all of us are exposed. Average radiation exposure of the occupational workers, in general, is in the range of natural background radiation levels.

Under such situations of uncertainty how one can assume that at low doses, the cancer risk is linearly lower?  It is quite possible that the risks are lower than predicted by LNT model or non-existent or even beneficial to health. There is also no direct evidence of increased risk of non-cancer diseases at low doses.    

Now why at all assume existence of cancer risk at such low levels of radiation and impede progress of the nuclear industry worth billions of dollars? 

[The BIER VII document: Health Risks from Exposure to Low Levels of Ionizing Radiation is available from the National Academies Press, 500 Fifth Street, NW, Washington, DC 20001, 2006] 

News item in Sunday Times (Sept. 7, 2014): Cancer behind 70% deaths in India’s atomic energy hubs

The change in the cell's genetic material may occur spontaneously or be brought on by an agent that causes cancer (a carcinogen). There are hundreds of reasons such as pollution, family history, cigarette smoking, intake of alcohol, exhausts from vehicles, etc for initiation of mutation in the body. As compared to these, radiation is a weak carcinogen.

It is a well-known fact that aging is associated with a number of events at the molecular, cellular and physiologic levels in our body that influence carcinogenesis and subsequent cancer growth. It is also well documented that the incidence of malignant tumors increases progressively with age, in both animals and humans.

A clearer understanding of these events will help in predicting and scientifically explaining the incidences of cancer.

The radiation doses received by workers in most of the facilities are in the range of natural background radiation dose to which all human being are exposed. The increase, if at all true, may not be related to the small radiation doses received by the workers and the members of the public living near nuclear facilities. It is reported that majority of deaths of persons in DAE centres are caused from cancer. If this is true, department should investigate the reasons other than radiation exposure for such a trend.

Kudankulam Judgment – well delivered

There was a news item in today’s DNA: “No clear reason in the Kudankulam judgment” authored by Praful Bidwai. It is shocking to see that he is questioning the very judgment of the Supreme Court which we all hold in great esteem. It is a well-informed judgment.

The judgment is very well made asking the government to follow all the safety related recommendations of the Indian Regulatory Board, AERB. The plants are ready and the technology is well known. There are very few cases of fatality in nuclear industry as compared to any other industry. There are well studied and well established techniques for the management of radioactive wastes.

One should not forget that we are all exposed to natural background radiation from space, from the radioactivity present in earth and the air we breathe. This we cannot avoid. We also do not mind getting X-rayed or CT scanned for diagnosis of diseases. These procedures do result in giving radiation dose to us.

The number of deaths Mr. Bidwai claiming (Chernobyl and Fukushima) is only the estimates and not the actuals! People should not be misguided by these mathematically calculated numbers. Compared to this calculated numbers, one can see instant fatalities in natural events. For example, the recent US twister with the energy equivalent of 600 Hiroshima bombs, resulted in deaths, and mass destruction in Oklahoma, of the order of USD2 billion!

It is rightly pointed out that one has to pay a small price for the immense benefits one gets from the use of electricity. These small risks are ACCEPTABLE.

It is time that the anti-development groups, anti-nuclear group in particular, should stop playing with estimated number of fatalities in any development programmes and focus on something more productive and serve the humanity. 

Cancer risk estimates by WHO - Fukushima radioactivity releases

This has reference to the News Report (Fukushima Disaster raised Cancer Risk - WHO...) in Times of India dated March 1, 2013.

With all the due respect for the WHO and the team of experts who have done the risk estimations, it can be stated that: 

1. The releases from Fukushima are very much lower than the Chernobyl. 

2. The estimated number of cancer incidences from the Chernobyl releases, predicted using the similar line of calculations followed by WHO, never occurred and far from reality. 

3. The very concept of Linear No-Threshold (LNT) approach followed for the risk estimations is not  experimentally proved and hence should not be used for actual risk calculations. 

4. The LNT concept can only be used for general optimization of protection.  

5. The International Commission on Radiological Protection (ICRP), in its latest recommendations, clearly stated that: Risk factors for carcinogenesis calculated using LNT approach have a high degree of uncertainty. This is particularly so for the calculation of cancer risk by adding up of the calculated low levels of individual doses to the members of the public (which is a small fraction of the natural radiation dose received by all of us), in situations of environmental releases in accidents. This is exactly the situation encountered in Fukushima nuclear accident. 

6. The ICRP Recommendations (ICRP-103, page no. 313) is the backbone of Radiological Protection   world-wide, and it clearly states that the adding up of small estimated doses over large populations and calculating the cancer risk is using LNT approach is NOT A VALID PROCEDURE. 

Based on the above facts, it is not advised to give such a publicity to the news item, which will only harm the nuclear industry. 

For further reading pl see: 

http://healthcare.financialexpress.com/inimaging2011jul/inimaging2011july09.shtml  

Storage of Spent Nuclear Fuel, IAEA Safety Standards Series SSG-15 Subject Classification: Radioactive waste management, STI/PUB/1503, 110 pp. Language: English, Date Published: 2012.

This Safety Guide provides recommendations and guidance on the storage of spent nuclear fuel. It covers all types of storage facilities and all types of spent fuel from nuclear power plants and research reactors. It takes into consideration the longer storage periods that have become necessary owing to delays in the development of disposal facilities and the decrease in reprocessing activities. It also considers developments associated with nuclear fuel, such as higher enrichment, mixed oxide fuels and higher burn-up. Guidance is provided on all stages in the lifetime of a spent fuel storage facility, from planning through siting and design to operation and decommissioning, and in particular retrieval of spent fuel. 

Contents: 1. Introduction; 2. Protection of human health and the environment; 3. Roles and responsibilities; 4. Management system; 5. Safety case and safety assessment; 6. General safety considerations for storage of spent fuel. Appendix I: Specific safety considerations for wet or dry storage of spent fuel; Appendix II: Conditions for specific types of fuel and additional considerations; Annex: I: Short term and long term storage; Annex II: Operational and safety considerations for wet and dry spent fuel storage facilities; Annex III: Examples of sections in operating procedures for a spent fuel storage facility; Annex IV: Related publications in the IAEA Safety Standards Series; Annex V: Site conditions, processes and events for consideration in a safety assessment (external natural phenomena); Annex VI: Site conditions, processes and events for consideration in a safety assessment (external human induced phenomena); Annex VII: Postulated initiating events for consideration in a safety assessment (internal phenomena) (Source; www.iaea.org).

Stable iodine prophylaxis

Stable iodine prophylaxis is a protective measure of administration of stable iodine to block uptake and reduce accumulation of of radioactive iodine released in nuclear reactor accidents, in thyroid. The administration is done before, or promptly after, intake of radioactive iodine released in nuclear reactor accidents. Intake of radioactive iodine by inhalation begins when the radioactive cloud arrives at a location and continues during the passage of the cloud. Action to implement stable iodine prophylaxis, and thereby reduce the dose to the thyroid, will be required promptly. The decision will most probably have to be made in a situation when reliable data for calculating the potential dose to the thyroid are not available. 

Stable iodine could also be used as prophylaxis against ingested radioactive iodine from contaminated food. However, in such situations, the iodine prophylaxis will be required for a longer period of time, leading to a need for repeated doses. In such situations, food controls would be easier to implement and more effective in the long term in reducing the collective dose than stable iodine prophylaxis.

Spent Nuclear Fuel – A Waste or a Resource?

In any power plant, there is a need of fuel which needs to be burnt to generate heat which in turn is used to produce steam and ultimately to produce electricity. In fossil fuel based plants, the fuel is coal or gas. There are different types of fuels, such as heavy metal fuels like naturally occurring uranium, enriched uranium ²³⁵U, plutonium (Pu) or their appropriate mixtures can be used in nuclear reactors. The radioactive isotopes – ²³⁵U and ^239/240Pu are fissile materials, meaning that the radioisotopes can undergo fission reaction to produce energy, termed as nuclear energy. Very highly radioactive fission products (see the reaction below) are also produced in the fission reaction. The half-lives of these fission products vary from seconds to several years. In addition to the release of energy during fission reaction, the decaying fission produce in the fuel generates large amount of heat (termed as decay heat). The heat from the fuel is utilized to produce steam via suitable heat exchanger systems.

In nuclear reactors, this rate of fission reaction is controlled, by design, to ensure proper and safe utilization of the released energy.     

In the reactors, nuclear fission reaction is induced using a sub-atomic particle, neutron. For example, heavy metal, ²³⁵U absorbs a neutron in the reactor to become an unstable nucleus ²³⁶U, which splits into two lighter and highly unstable products fission products, three neutrons and a lot energy. The unstable fission products quickly decay to finally become ¹³⁷Cs (a beta-gamma emitter) and ⁹⁰Sr (a beta emitter) with half-lives of around 30 years.

The ²³⁸U isotope forms about 99.27% of natural uranium. In the nuclear reactors, due to the neutron absorption, a small percentage of the uranium isotope gets converted through nuclear reactions, to plutonium isotopes which are again good fissile materials and can be used in nuclear weapons, and as part of mixed nuclear fuel used in “breeder” reactors. The remaining portion of the spent fuel consists of depleted uranium (DU) where the percentage of fissile ²³⁵U is reduced due to the fission reaction in the reactor to below the existing level of 0.72% in natural uranium fuel.

After the useful life of the nuclear fuel in the reactor, the highly radioactive fuel is called Spent Nuclear Fuel (SNF). As such, SNF does not have further use as nuclear fuel.

In addition to the fission products, plutonium, depleted uranium, the SNF also contains minor actinides which include long-lived and relatively long-lived isotopes of neptunium (²³⁷Np), americium (²⁴¹Am and ²⁴³Am) and curium (²⁴²Cm, ²⁴⁴Cm). These are also useful radioisotopes. Efforts are underway to separate the fission product radionuclides chemically from the waste and use them as radiation sources in industrial applications of radioisotopes.   

In countries where nuclear power has a considerable share in electricity production and has adequate uranium resources, the SNF is considered as nuclear waste and is disposed of or stored safely in isolation from the biosphere.  In countries like India, where there is shortage of uranium and need plutonium as fuel for the future up-coming reactors, the SNF is the resource material which can be reprocessed chemically to separate the useful plutonium and depleted uranium from the spent fuel.  

It is reported that India now retains the right to reprocess the SNF in India, with all the safety aspects considered, from upcoming Kudankulam nuclear power plant instead of sending them away to Russia.