IN defending the use of nuclear power sources for electricity generation, I will focus on the science behind nuclear waste management.
Let us first define what nuclear waste is. Generally speaking,
there are three categories of nuclear waste: low-level waste (LLW), intermediate-level waste (ILW) and high-level waste (HLW).
Of these, LLW makes up around 90 per cent of the waste generated by nuclear plants.
These include scrap metal, paper and plastics contaminated with radioactive material or exposed to neutron radiation.
These wastes are sent to be processed and disposed of at certain sites, which are purpose-built yet are not dissimilar to normal municipal waste disposal sites. Disposal facilities have strict limits on radioactivity for LLW.
LLW that exceeds this amount, like graphite from reactor cores, must be considered when developing long-term disposal options for higher-level wastes.
However, LLW of this type forms only a small proportion of the whole. LLW of very low levels of radioactivity can be disposed of in authorised landfill sites alongside commercial and municipal wastes, with strict limitations, of course.
Traditionally, LLW is stored in repositories by first grouting (immobilising with cement) inside metal containers. Once full, the metal containers will be fit with a cap.
However, further processing may be done before this step to reduce the amount of waste produced. These include recycling metals of low radioactivity, incineration of certain wastes (like plastics and textiles), cutting and supercompacting.
All in all, LLW can be dealt with in a straightforward, uncomplicated manner.
ILW is a little trickier. Treatment, including supercompacting, cutting and drying, may be used before packaging for storage and disposal. ILW is similarly immobilised in cement-based materials and packed into steel, concrete or ductile cast iron boxes.
Where it gets complicated is long-term management of ILW. For this, the method of disposal has to follow that for HLW.
HLW is a main concern when it comes to nuclear waste. Though it makes up a small amount of all nuclear wastes, 99 per cent of the total radioactive content is found in HLW.
Moreover, HLW is a long-lasting waste, with radioactive half-lives of some nuclei stretching thousands of years, though this doesn’t mean the total level of radioactivity remains high for this long due to the decay of other nuclei.
HLW comprises spent fuel rods and other contents of the reactor post-utilisation and is stored initially underwater in pools onsite at power plants.
Water is a good retardant for radiation and also cools the rods for about 50 years until radioactivity and temperature decrease to manageable levels.
The pools are made of thick, reinforced concrete with steel liners, designed to withstand hazards, such as flooding and earthquakes, and will hold all of the used fuel produced over the lifetime of the reactor.
Some of the HLW can be transferred into dry casks with air circulation inside concrete shielding after a minimum of five years inside the water tanks.
Others remain indefinitely in the tanks for about 50 years.
HLW may also be treated through vitrification to facilitate transport.
This includes mixing it with glass-forming materials and heated to high temperatures, which will immobilise HLW in glass. This is then sealed in stainless steel canisters to be stored temporarily.
Permanent disposal of HLW is a bone of contention between professionals and the public, especially because the most viable method of disposal is geological disposal.
This requires disposing of radioactive wastes deep inside a suitable rock volume, for example, hill ranges, that will ensure long-term safety and environmental sustainability.
However, the public is usually opposed to this solution as it is believed burying nuclear waste would irradiate soil, cause massive pollution and health complications.
This is wrong as the methods of disposal are sufficient to ensure any safety or pollution concerns are addressed.
Even so, there is no dedicated deep geological repository site that is in operation anywhere in the world.
Steps to create them were proposed, but most were shot down, again due to public perception.
The most famous among these is the Yucca Mountain nuclear waste repository in Nevada, a huge deep geological repository project approved in 2002 by the United States Congress, but it had to be closed for political reasons.
This leaves nuclear power plants to store their waste through indefinite onsite dry cask storage instead until a long-term solution is found.
All is not lost, though, as Finland and Sweden pave the way forward. Proper inclusion of the public has smoothened efforts in Finland to open a deep geological repository for waste management.
Now, the Onkalo spent nuclear fuel repository is being built and the process of burying nuclear waste is projected to begin in 2020.
It is based on the Swedish KBS-3 method of nuclear waste burial. Ironically, the Swedish have not begun construction of their own spent fuel repository.
All of this shows nuclear waste disposal is a multifaceted, complex process, but is well-established and robust as well.
As before, political and social misconceptions have established nuclear waste as too difficult to handle whereas for over 50 years, it has been dealt with quite well.
In this regard, let us first establish how much waste the technology produces.
If electricity was provided through nuclear fission alone, only 40g of fuel per person is produced.
For coal and fossil fuel-heavy energy production, CO2 emissions run in tonnes per capita. This is not inclusive of particulate matter generation, toxic emissions and other environmental pollutants such as sulphur dioxide.
Arveent Kathirtchelvan is the Chief coordinator of #Liberasi Kuala Lumpur