Nuclear Waste Disposal

Current disposal and storage methods

Disposal of low level waste:

Some wastes produced from pharmaceutical plants, universities, and medical facilities, are often kept on-site for the short time it takes for them to decay to safe levels Then they are deposited into sanitary landfills.

Low-level waste landfills were first built in the 1960s and consist of containers of waste buried in a near-surface trench and surrounded by compacted land.
Waste containers in near-surface landfills are prone to corrosion, particularly in moist climates. Alternatives include on site storage facilities.

Disposal of High level waste:

The majority of high level waste is produced from the reactor core in the form of fuel rods.

When the used fuel rods are first removed from a reactor, they are extremely hot. The fuel rods are placed in a special pool of with boric acid contained in a steel-lined concrete basin. The boric acid acts to cool the spent fuel and protects the workers from ionizing radiation by absorbing any neutrons emitted.

After the waste has cooled considerably, some commercial power plants and government facilities move the fuel to dry-storage containers made of steel and/or concrete to shield radiation.

The containers are either placed upright on concrete pads, or stored horizontally in metal canisters in concrete bunkers.

The Fuel rods can also be left in the storage pools until a permanent disposal option is available.

Storage pools and containers

Permanent High-level waste disposal options

There have been many proposed ideas for the disposal of high-level radioactive wastes.
These ideas include the following:

• Leaving the material at current storage sites (storage pools, dry storage containers) for approximately 40 years so the radioactivity decreases to much more manageable levels
• Burying it in the ocean repositories (seabed disposal)
• Putting it in polar ice sheets
• Sending it into outer space
• Placing it deep underground in a geologic repository

The best long-term solution to managing highly radioactive waste is disposal in an underground repository

Oceanic Repositories:

Many factors need to be taken into consideration when selecting an oceanic site for waste disposal. These include:

• Disposal sites need to be free from erosion and located away from the edges of tectonic plates where seismic or volcanic movements could disrupt a repository and exposes the waste packages.
• Isolated ocean regions under water at least 4,000 meters deep
• Sites must possess thick, weak, relatively homogenous sediments of very fine particles

Land-based Geologic Repositories:

The factors that need to be considered when selecting a geologic site for high-level nuclear waste disposal are:

• Geological hazards, such as earthquakes, volcanic activity, cyclones, and landslides;
• Local environmental hazards such as flooding and fires;
• Natural environmental features such as surface drainage, types of soil, and water (both under the ground and in lakes, streams and rivers);
• Hydrology of the site ie. Average rainfall, amount of water percolation, depth of water table at site;
• Mineral, oil, and gas resources that could invite future human intrusion;
• Access to transport, support facilities and infrastructure;
• Population densities;
• Social impacts;
• Land ownership;
• Sites or areas of special environmental, cultural or historical significance;
• Security; and
• Security of land tenure and compatibility with adjacent land use.

Overview of High-level nuclear waste disposal

As long as nuclear waste remains in a solid form and is properly shielded, it will cause minimal harm and contamination to the environment.

Deep geologic disposal is designed to keep the waste dry and isolated for as long as possible, so that its radiation can diminish to safe levels.

Current storage methods shield any harmful radiation and are presently safe. However, modern aboveground storage structures are designed for temporary storage only and will not withstand environmental factors for the tens of thousands of years while the waste is radioactive.

Several countries are currently investigating sites acceptable for long term waste disposal.

Australia's waste production

While Australia has no nuclear power producing electricity, it does have well-developed usage of radioisotopes in medicine, research and industry. Many of these isotopes are produced in the research reactor at Lucas Heights, near Sydney, then used at hospitals, industrial sites and laboratories around the country.

Each year Australia produces about 45 cubic metres of radioactive wastes arising from these uses and from the manufacture of the isotopes - about 40 cubic metres of low-level wastes (LLW), and 5 cubic metres of intermediate-level wastes (ILW).

At present Australia has about 3700 cubic metres of low-level waste awaiting proper disposal, though annual arisings are small (the 40 cubic metres would be three truckloads). Over half of the present material is lightly-contaminated soil from CSIRO mineral processing research over 30 years ago.

In addition to the information listed in the table above, low level and short-lived intermediate level waste will be generated by the decommissioning of the High Flux Australian Reactor (HIFAR) and the replacement research reactor. Depending on the decommissioning options chosen, between 500 and 2500 cubic metres of waste will be generated by the decommissioning of each reactor.

Australia's storage solutions

Current storage

Radioactive waste is currently in temporary storage at hundreds of locations around Australia, often within towns and cities. The Australian and state and territory governments have responsibility for safe and secure management of radioactive waste in their jurisdictions. This is not considered a suitable long-term strategy.

Previous projects

Prior to 2004, the Australian Government was proceeding with two radioactive waste management projects: the national repository and the national store.
These projects proposed three radioactive waste management facilities:

• The National Low Level Waste Repository: an engineered near-surface underground facility for the disposal of low level nuclear waste.
• The National Store: an interim purpose-built above ground storage facility for the safe storage of intermediate level radioactive waste.
• The National Geological Repository: an engineered underground facility at depth for the disposal of intermediate level radioactive waste. Disposal at depths of typically several hundred metres is an internationally accepted standard.

In May 2003 a final site for the National Store was decided, near Woomera in South Australia. But on 14 July 2004, the Prime Minister, John Howard, announced that the Australian Government was abandoning the national radioactive waste repository project for low-level and short-lived intermediate level radioactive waste, and that the Government will construct co-located facilities for the management of low level and intermediate level radioactive waste.

Future proposals and current projects

On the 15 of July 2005, three potential locations were announced to be investigated for the Radioactive Waste Management Facility.
The three locations are Department of Defence properties located near Katherine and Alice Springs in the Northern Territory;

• Fishers Ridge, Department of Defence property, southeast of RAAf Base Tindal;
• Mt Everard, Department of Defence property, northwest of Alice Springs; and
• Harts Range, Department of Defence property, northeast of Alice Springs.

Each site will be assesed to determine the most suitable site. Then, after environmental impact assessment and site licensing by the Australian Radiation Protection and Nuclear Safety Agency (ARPANSA), the facility will undergoe ARPANSA construction and operating licensing processes, will operation expected to commence in late 2011.

An Australian Low-level solid waste storage facility.

Case Study: YUCCA Mountain

Yucca Mountain is a permanent waste disposal site in the US. Yucca Mountain is in an extremely dry area of Nevada. This minimizes the possibility of water seeping through the rock and corroding the casks resulting in radiation leakage.

• It lies 1600 kilometers northwest of its closest city, Las Vegas
• The casks will be buried about 500m underground
• if the casks do get corroded, there is not much water flow to carry the nuclear wastes away
• While Yucca Mountain is near of a fault line, the fault is believed to be inactive
• The Yucca Mountain Deep Geological Repository is projected to be ready by the year 2010.
  

A storage Tunnel in Yucca Mountain.