Nuclear Waste

Context (TH): Researchers at the Bhabha Atomic Research Centre (BARC) in Mumbai studied 20 years of radiological data (2000-2020) from six nuclear power plants in India.
They discovered that the radioactive releases and their possible impact on the environment have been very low. This information could support India to advancing its nuclear power program.

Radioactive (or nuclear) waste is a byproduct from nuclear reactors, fuel processing plants, hospitals and research facilities.
It is also generated while decommissioning and dismantling nuclear reactors and other nuclear facilities.
Nuclear Wastes: Argon 41, radioiodine, pcobalt-60, strontium-90, tritium and caesium-137.
There are two broad classifications: high-level or low-level waste.

It is primarily uranium fuel that has been used in a nuclear power reactor and is “spent,” or no longer efficient in producing electricity.
- The fission creates radioactive isotopes of lighter elements such as cesium-137 and strontium-90. These isotopes, called “fission products,”. It accounts for most of the heat and penetrating radiation in high-level waste.
- Some uranium atoms capture neutrons produced during fission. These atoms form heavier elements such as plutonium. It is known as “transuranic,” elements. They take much longer to decay.

It includes items that have become contaminated with radioactive material. For example, shoe covers and clothing, wiping rags, filters, etc.
They are commonly disposed of in near-surface facilities rather than in a geologic repository. There is no intent to recover the waste once it has been disposed of.

In a fission reactor, neutrons collide with the nuclei of specific atoms.
When a nucleus absorbs a neutron, it becomes unstable and splits, releasing energy and forming nuclei of other elements.
- For instance, uranium-235 can split into barium-144, krypton-89, and three neutrons when it absorbs a neutron.
If the resulting elements cannot undergo further fission, they become nuclear waste.

Nuclear waste also includes the spent fuel which is extremely radioactive and requires secure storage to prevent environmental contamination.
Fuel used in a nuclear reactor becomes irradiated and is known as spent fuel when removed.

It is challenging to handle due to its high temperature and radioactivity, often requiring underwater storage for several decades.
Once cooled, spent fuel can be transferred to dry casks for long-term storage.
Storage periods for spent fuel can extend for millennia, requiring isolation from human contact.
Countries with established nuclear power programs have accumulated significant amounts of spent fuel.

Liquid waste treatment facilities in nuclear power plants manage aqueous wastes containing short-lived radionuclides.
- Japan, for example, treats and discharges such water from the Fukushima nuclear plant into the Pacific Ocean.
Other liquid wastes can be evaporated, chemically precipitated into sludge, absorbed on solid matrices, or incinerated depending on their hazard.
Liquid high-level waste, containing most fission products, is vitrified into glass for storage.
In India, fission products from pressurized heavy-water reactors must be stored as liquid waste due to reprocessing, posing accident hazards.

Vitrification: It is the full or partial transformation of a substance into a glass.

After spending at least, a year in a spent-fuel pool, cooled spent fuel can be moved to dry-cask storage.
In dry-cask storage, spent fuel is placed inside large steel cylinders and surrounded by inert gas before being sealed shut and placed in larger steel or concrete chambers.

Some experts advocate for geological disposal, where waste is sealed in special containers and buried underground in granite or clay.
Geological disposal offers long-term storage away from human activity, but there are concerns about potential exposure if containers are disturbed.
The emplacement of waste can affect the properties of surrounding rock, creating increased fracture zones and thermal pulses.

It is a method to separate fissile from non-fissile material in spent fuel.
The material is chemically treated to separate fissile material left behind from the non-fissile material.
Reprocessing facilities require specialized protection and personnel due to the hazardous nature of spent fuel.
Reprocessing offers higher fuel efficiency but is expensive and yields weapons-usable plutonium (different from weapons-grade).
The IAEA regulates reprocessing facilities tightly, specifying thresholds for plutonium content to ensure safeguards.

The Trombay facility reprocesses 50 tonnes of heavy metal per year (tHM/y) as spent fuel from two research reactors to produce plutonium for stage II reactors as well as nuclear weapons.