Nuclear Waste

Nuclear waste, also known as radioactive waste, is the byproduct of nuclear reactors, fuel processing plants, hospitals, and research facilities, as well as from nuclear weapons production. Read here to learn more.

Managing and disposing of nuclear waste safely is one of the most critical challenges in the nuclear power industry due to its potentially harmful effects on humans and the environment if not handled properly.

The complexity of nuclear waste management is compounded by the fact that some forms of waste remain radioactive and hazardous for thousands to millions of years.

Nuclear waste

Any activity related to the nuclear fuel cycle, that produces or uses radioactive materials generates radioactive waste.

• The management of radiation-emitting radioactive material is a matter of concern and is what sets nuclear waste apart.
• Public acceptance of nuclear energy largely depends on the public assurance of safe management of radioactive wastes.
• Not all nuclear wastes are particularly hazardous or difficult to manage as compared to other toxic industrial wastes.

Radioactive wastes are generated during various operations of the nuclear fuel cycle as well as the production and use of radionuclides for various societal applications.

• Activities like mining and processing of uranium ore, fabrication of nuclear fuel, generation of power in nuclear reactors, processing of spent nuclear fuel, management of radioactive waste, production and use of radionuclides for various industrial and medical applications, research associated with radioactive material, etc. generate the different types of radioactive waste.
• Radioactive waste can be in gas, liquid, or solid form, and its level of radioactivity can vary.
• The waste can remain radioactive for a few hours several months or even hundreds of thousands of years.
• The most important and advantageous property of radioactive waste is ‘Its radioactive hazard potential reduces with time depending on the half-lives of a radionuclide present in the waste’.
• Such feature differentiates them significantly from conventional chemical or industrial waste, hazard potential or toxicity of which does not alter with time and remains constant till its transformation to another suitable form.

Depending on the level and nature of radioactivity, radioactive wastes can be classified as exempt waste, Low & Intermediate level waste, and High-Level Waste.

Read: Nuclear energy

Types of Nuclear Waste

1. High-level waste (HLW): This includes used (spent) reactor fuel and waste materials remaining after spent fuel is reprocessed. HLW contains many of the highly radioactive fission products and transuranic elements generated in the reactor core. It requires cooling and shielding.
2. Intermediate-level waste (ILW): This waste contains higher amounts of radioactivity than low-level waste but does not generate enough heat to require cooling. ILW includes resins, chemical sludge, and metal nuclear fuel cladding, as well as contaminated materials from reactor decommissioning. It typically requires shielding during handling and transport.
3. Low-level waste (LLW): LLW comprises items like paper, rags, tools, clothing, filters, etc., which have been used in areas of nuclear facilities where radioactive materials are produced. LLW can include some materials from hospitals and industries. It has lower levels of radioactivity and may sometimes be disposed of in near-surface disposal facilities.
4. Very Low-Level Waste (VLLW): This waste is similar to LLW but with even lower levels of radioactivity. It can often be disposed of with regular municipal trash, following specific regulatory exemptions.

Management and Disposal

Utmost emphasis is given to waste minimization and volume reduction in the choice of processes and technologies adopted in nuclear waste management plants.

As a waste management philosophy, no waste in any physical form is released/disposed to the environment unless the same is cleared, exempted, or excluded from regulations.

• Temporary Storage: Spent nuclear fuel is initially cooled in spent fuel pools near the reactor site. After cooling, it can be moved to dry cask storage, which is a more stable form of storage.
• Reprocessing: Some countries reprocess spent nuclear fuel to extract usable materials (such as plutonium and uranium) for use in nuclear reactors again. This process reduces the volume of high-level waste but introduces complex chemical processes and potential proliferation risks.
• Deep Geological Disposal: The most widely agreed-upon method for the disposal of high-level nuclear waste is deep geological storage in stable geological formations several hundred meters or more below the surface. Finland, Sweden, and France are at the advanced stages of developing such facilities.
• Transmutation: Research is ongoing into methods to transmute long-lived radioactive elements in spent fuel into shorter-lived or stable elements. However, this technology is not yet commercially available and faces significant scientific and engineering challenges.

In consideration of the primary objective of protecting human health, the environment, and future generations, the overall philosophy for the safe management of radioactive wastes in India, is based on the concept of

1. Delay and Delay
2. Dilute and Disperse
3. Concentrate and Contain
4. Recycle and Reuse

Effective management involves segregation, characterization, handling, treatment, conditioning, and monitoring before final disposal.

Management of Nuclear Waste in India

High levels of radioactive waste are generated during reprocessing of spent fuel. Most of the radioactive isotopes in high-level waste emit large amounts of radiation and have long half-lives.

The management of high-level waste in the Indian context is carried out in the following three stages:

1. Immobilization of high-level liquid waste into inert vitrified borosilicate glasses through a process called ‘vitrification’.
2. Engineered interim storage of the vitrified waste for passive cooling & surveillance over some time, qualifying it for subsequent disposal.
3. Disposal of the vitrified waste in a deep geological repository.

Vitrification

India is one of the few countries to have mastered the technology of vitrification.

• Over the years BARC has developed the technology for vitrification of HLW. India has a unique distinction of having an operating vitrification plant at Trombay, Tarapur, and Kalpakkam.
• The vitrified product is encapsulated in suitable containers and overpacks and stored for dissipation of radioactive decay, heat, and surveillance for 15-20 years.

Wealth from waste

High-level radioactive liquid waste contains various useful fission products such as ¹³⁷Cs, ⁹⁰Sr,¹⁰⁶Ru, etc., which have many industrial as well as medical applications.

• The energy associated with these isotopes can be used for blood irradiation, food preservation, sewage treatment, therapeutic applications, brachytherapy, and various other industrial applications.
• Separation and recovery of these useful isotopes from radioactive waste and their deployment for societal application make the waste a material of resource.

Read: Waste to wealth

Challenges and Concerns

• Longevity: Radioactive waste can remain hazardous for periods far beyond human civilization’s current lifespan, raising ethical questions about our responsibility to future generations.
• Security: There is a need to ensure that nuclear waste storage and disposal sites are secure from theft and cannot be used for malicious purposes.
• Environmental Impact: Potential leakage from waste storage facilities could contaminate water and soil, posing a risk to ecosystems and human health.
• Economic Costs: The construction, maintenance, and monitoring of safe disposal facilities for nuclear waste entail significant financial investments.

Why in the news?

Recently, India loaded the core of its long-delayed prototype fast breeder reactor (PFBR) vessel, bringing it to the cusp of stage II, powered by uranium and plutonium – of its three-stage nuclear programme.

• By stage III, India hopes to be able to use its vast reserves of thorium to produce nuclear power and gain some energy independence. However, the large-scale use of nuclear power is accompanied by a difficult problem: waste management.

Conclusion

Nuclear waste management requires meticulous planning, robust engineering solutions, stringent regulatory frameworks, and international cooperation to address the challenges posed by the safe disposal of nuclear waste and to minimize its impact on the environment and human health.

-Article by Swathi Satish