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Science-Radioactive Waste Management !!!

Understanding Radioactive Waste

 

Nuclear, or radioactive waste is the waste product of nuclear reactors, fuel processing plants, research facilities and hospitals, and is also produced when nuclear reactors and facilities are dismantled.

Radioactive waste is differentiated into high-level and low-level radioactive waste. While high-level waste is the spent fuel detached from nuclear reactors, low-level waste is generated from other scientific, industrial and commercial uses of radioactive materials (USNRC, 2015).

India however, also includes a third category called intermediate-level radioactive waste, which require shielding for disposal but little or no heat protection. Intermediate-level radioactive wastes are disposed in a similar manner to high-level radioactive waste and are concentrated and fixed in cement. These qualities are delineated according to the radioactive content present in the waste and its half-life i.e. the time consumed by the waste in losing half of its radioactivity.

High-level radioactive waste comprises the fuel which is used up in a nuclear reactor for generating electricity, usually uranium, which is called spent fuel – fuel that is no longer efficient for producing electricity. Nuclear energy produced through the process of nuclear fission produces fission products such as radioactive isotopes of strontium-90 and cesium-137, which are lighter elements that provide the penetrating radiation and the hottest elements in radioactive waste.

Also plutonium, a heavier element produced during fission by the capture of neutrons by uranium atoms and also other trans-uranic elements heavier than uranium do not possess the same heat and penetrative capacity as lighter elements but however, take much longer to decay and can be a radioactive hazard in nuclear waste much longer than 1,000 years (USNRC, 2015).


Management of radioactive waste

Management of radioactive waste is dependent on its properties, which can be radioactive, chemical, or physical properties.

High-level radioactive wastes are made up of complex amalgamations of radionuclides (radioactive forms of elements) of about 30 to 40 different elements. Most of these radionuclides are toxic and emit radioactive particles like alpha, beta or gamma rays during their decay. The disposal of high-level radioactive wastes requires their storage i.e. containment and concentration.

There are different time periods for which high-level radioactive wastes need to be isolated and stored, depending on the amount of time the radioactive wastes take to decay i.e. reach a level roughly equal to naturally occurring radiation levels i.e. to that of uranium ore for example.

The time period required can sometimes extend up to more than 1,00,000 years and as this makes storage difficult. Technologies are being developed in an effort to reduce the time period to about 1,000 to 10,000 years. In contemporary times, however, the most potent storage solution is part-geological – the immobilization of radioactive wastes.


Mechanism of immobilization

The immobilization of radioactive wastes is based on the multiple barrier system (MBS) concept, which is composed of an engineered barrier system and a natural barrier system. The engineered barrier system, with cooled off radioactive wastes contained inside a stainless steel canisters placed inside a drilled hole underground that is surrounded by rocks such as granite or basalt, which act as a natural barrier.

There are other storage methods such as the dry cask method where the stainless steel canisters containing nuclear waste are surrounded by concrete after the spent fuel is cooled for about 5 years.

However, the dry cask method is not as safe as the geological method and cannot be called a permanent method of storage of radioactive wastes. Some other methods of disposal of radioactive wastes include reprocessing, transmutation and space disposal.

Geological disposal of radioactive wastes is not present however, in many countries and some of the countries that have implemented immobilized geological disposal include Sweden, France, Finland and India (in Tarapur and Trombay).

Low-level radioactive waste comprises of substances that are contaminated with radioactive material or those that have become radioactive due to exposure to radioactivity. The amount of radioactivity in low-level radioactive waste can vary from base levels found naturally to the amount of radioactivity found in nuclear reactors. Low-level radioactive wastes are conventionally stored on-site until it decays and then can be disposed off harmlessly or it can also be shipped to a secure location (USNRC, 2015).


Health Effects

The nature and severity of the health effects of radiation exposure depends upon the amount of radiation and the time for which one is exposed to radiation. Radiation exposure in relation to human health can be chronic or acute exposure.

Continuous or intermittent exposure to radiation over a long period of time leads to chronic exposure. In chronic exposure the health effects are observed a certain time period after exposure to radiation, and most commonly leads to cancer.

Other health effects include genetic changes, cataracts, tumors, etc.

Acute exposure occurs when large parts of the human body are exposed to large amounts of radiation and can occur one time or multiple times over intervals of time (USEPA, 2017). Acute exposure leads to radiation sickness, which is a collection of health effects taking effect within 24 hours of acute exposure to radioactivity involving mainly cellular degradation and its various symptoms.

Smaller exposures can lead to gastrointestinal effects, nausea, vomiting and reduced blood counts. A larger exposure can lead to neurological effects and even death. As the cells of pregnant women and foetuses divide rapidly, providing greater opportunity for radiation to spread and cause cell damage, they are particularly at risk of exposure to radiation.

Among power plant accidents and radioactive contamination risks the most recent disaster in memory is the Fukushima disaster that occurred after the earthquake and tsunami that rocked Japan in 2011.

The disaster led to explosions and melting of fuel rods at the power plants and although there weren’t as many casualties as in the Chernobyl disaster of 1986, the long term effects and cancer-related death are still taking place.

Most of the nuclear power plant disasters in recent history have taken place in Europe and the US, with the Fleurus (Belgium 2006), Forsmark (Sweden 2006), Erwin (US 2006), Sellafield (UK 2005) Braidwood (US 2005) and Paks (Hungary 2003) disasters.

The most severe disasters in terms of casualties and damage to the environment are said to be the Chernobyl (erstwhile USSR 1986), Kyshtym (erstwhile USSR 1957), Windscale (UK 1957) and Three Mile Island (US 1979) disasters with the former two leading to a severe release of radioactivity with severe health and environmental consequences while the latter two had a more limited release of radioactivity (The Guardian, 2011) but led to numerous deaths due to inadequate containment.


Policy Regime on Radioactive Wastes

In terms of the governance of radioactive wastes, the first point is that radioactive wastes can only be handled by trained personnel who are specialists. They mostly work in the 446 nuclear power plants operational in the world that produce radioactive wastes (IAEA, 2017).

However, other than the organizational aspect, the only legal policy to implement safety standards in managing radioactive wastes internationally is the Joint Convention on the Safety of Spent Fuel Management and on the Safety of Radioactive Waste Management.

While the International Atomic Energy Agency (IAEA) manages nuclear safety on the international arena, in India the Atomic Energy Regulatory Board (AERB) formulates policies and lays down safety standards concerning nuclear energy. The AERB exercises regulation by laying down guidelines and a licensing system based on stage-based evaluation, which is the bulwark of India’s nuclear safety programme.

As per the AERB, there are 20 operating nuclear plants in India that includes 4 units of the Tarapur nuclear power station, 6 units of the Rajasthan nuclear power station, 2 units of the Kalpakkam nuclear power station in Tamil Nadu, 2 units of the Narora nuclear power station in UP, 2 units of the Kakrapar nuclear power station in Gujarat and 4 units of the Kaiga nuclear power station in Karnataka (AERB, 2013).

AERB’s involvement in India’s nuclear safety programme includes reactor design policies, radiation exposure targets, radioactive waste management, and preparedness for nuclear emergencies. The most popular storage method is vitrification (converting radioactive waste to glass-like solid cakes) in India, followed by storage in steel canisters. There is a necessity in India for more geological storage facilities like those in Tarapur and Trombay.

The instrument for the IAEA internationally is the Joint Convention that seeks to achieve nuclear safety through an international collaborative approach based on the sharing of expertise on radioactive wastes and spent fuel management.

The Convention fixes international safety standards and measures to ensure nuclear safety based on agreements between stakeholders and it strives to achieve national arrangements in individual countries based on the standards agreed upon in the convention. The Convention also includes clauses that facilitate individual countries with improper infrastructures to receive international assistance in case of a lack of resources. The Convention applies both to countries with nuclear power programmes and those using radiation sources for industrial and commercial purposes (IAEA, 2011).

U.C. Mishra of the AERB, writing while working for the Bhabha Atomic Research Centre (BARC) says that, “The preferred approach in our country in this perspective [environment] is concentration and contamination of radionuclides rather than their dilution and dispersion into the environment” (U.C. Mishra, BARC, 2011). One only needs to remember the Chernobyl, Fukushima and Three Mile Island disasters to understand the horrific impacts radiation discharges can have on the environment and health.

In such a scenario, a proper method and discipline of storing radioactive wastes, coupled with a regulative infrastructure that supports nuclear safety and an international regime that facilitates and ensures the presence of safety standards and infrastructure in case of deficiencies in individual countries is imperative.

The first step towards this would be a foolproof method of containing radioactive wastes, and the geological immobilization of radioactive wastes, seen as among the most effective techniques, or a similarly effective storage technology effectively implemented worldwide would be a giant step forward in this regard.


 

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2017-07-22T02:03:41+00:00