Edition 3, Revised 20/10/2016
In this Edition 3 of the website, two new tabs outlining regions of interest for nuclear power plants in Western Australia and South Australia have been added to the existing New South Wales and Victoria.
The selection of sites for nuclear power stations needs to balance key issues such as water for cooling, transmission grid capacity, geology, seismicity and social factors affecting local populations. A very good resource for detailed discussion can be found Information Library – World Nuclear Association.
Australia’s long coastlines provide many options for locating nuclear power plants such as the Qinshan Power plant in China shown in Figure 1.
An excellent and detailed outline of the cooling options is available at: Cooling Power Plants | Power Plant Water Use for Cooling – World Nuclear Association
This page will monitor the development of options for locating reactors in Australia which is an essential step in progressing a Nuclear for Climate plan. A brief outline of a few key issues used to determine nuclear reactor sites will be followed by an outline of regions of interest within Australia.
Water is key to cooling nuclear power reactors. Close proximity to reliable sources of water for cooling is a key factor in locating any reactor. The water can be used as “first pass” where it flows into the power plant heat exchangers and back out to the source. This typically occurs at seaside locations or on large rivers or lakes. It doesn’t consume much water but it does heat up the source. This is of little consequence in the sea however, it can limit the amount of energy generated at inland water ways.
Where inland rivers or lakes need to be protected from heat gain, evaporative mechanical and natural draft cooling towers are used. There use however requires a continued supply of makeup water to replace that lost to evaporation and “blowdown”.
To address these water demand future reactors at inland sites will increasingly use “hybrid” systems which rely upon fresh water when supplies are plentiful and air cooling when water resources are under strain. An excellent reference describing this process is available at ASME: Economic design of hybrid wet-dry cooling systems – Energy-Tech Magazine: Heat Exchangers
From a cost perspective advantages are gained where new low carbon generation sources are able to maximise the use of the existing National electricity grid. Our Australian grid is long and in places has been developed around lower output generating plants. Nuclear power plants are large and are best built with multiple reactors at each site. This means the transmission lines need to be at least 330 kV and ideally 500kV.
New sites will need to be located close by the grid or will require regional grid expansion to be taken into account. This will include in most cases new switchyards and transformers in addition to the transmissions lines.
A very detailed discussion of the challenges being faced by countries integrating different forms of energy generation onto their grids can be found at: Electricity Transmission Grids – World Nuclear Association
There is a strong preference towards founding nuclear power plants on rock. This approach largely overcomes the potential for surface deformations that may arise from subsidence and settlement associated with alluvium, beach deposits and glacial deposits.
When located in coastal regions the site itself should be adjacent the shore line, generally within 2 or 3 km and needs to be about 20 m above mean sea level.. This level is required to address factors such as future global warming induced sea level rise and the seiche or tsunami induced flooding within the enclosed gulf waters.
At coastal locations excessively high sites will add substantially to the cost of sea water cooling structures. Sites located on alluvial flats at low elevations are not suitable due the long term inundation and surface settlement potential. Construction of reactors on alluvial materials is possible, but is generally avoided for reasons of cost and undesirable seismic response.
Australia is a seismically stable continent. Nuclear facilities are rigorously designed to resist the effects of earthquakes such that the plants are able to operate continuously during and after the Design Basis Earthquake (DBE). The profession is highly experienced in the area of seismic design and seismic response. Even during the catastrophic earthquake in Japan in 2011, the nuclear plants performed as intended—the associated tsunami was the cause of the widespread damage, not the earthquake per se.
As stated on the World Nuclear Association website, the Peak Ground Acceleration (PGA) or Design Basis Earthquake Ground Motion (DBGM) is used as a measure of the size of an earthquake. It is measured in Galileo units – Gal (cm/sec2) or g – the force of gravity, 1.0 g being 980 Gal. The PGA is a measure but of course the seismic design basis for a nuclear power plant includes other parameters such as the frequency spectrum and duration of the design earthquake, damping (energy dissipation) in the foundation media, surrounding soil or rock and the structure itself. Modern nuclear plants are designed for a standardized earthquake, and therefore, the site where the nuclear plant is constructed must have a seismic hazard level enveloped by the standardized design. Typical reactor designs require them to automatically shut down when the peak ground acceleration exceeds 0.3 g. To put this into perspective, the Newcastle earthquake of 1989 had a Richter scale value of 5.6 and an estimated peak ground acceleration of 0.24 g.
Issues addressing the impact upon local populations will be explored as this site develops. Reactors are frequently surrounded by populations of modest density as shown Figure 4 at the Tihange Nuclear Power Plant in Belgium.
In the United States the Nuclear Regulatory Commission defines two emergency planning zones around nuclear power plants. Frstly a plume exposure pathway zone of 10 miles or 16km radius. This is concerned primarily with exposure to, and inhalation of, airborne radioactive contamination. Secondly a larger ingestion pathway zone of about 50 miles or 80km radius is concerned primarily with ingestion of food and liquid contaminated by radioactivity.
By way of example, the population within 16km of the Sequoyah plant shown in Figure 3 was 99,664, according to 2010 U.S. Census data. The 2010 population within 80km was 1,079,868. Cities within 80 km included Chattanooga being 22 km to the city centre.
As this site develops the suitability and the number of regions and specific sites within those regions will be explored. Some regions may be found to be unsuited and new options added. Regions within Queensland, South Australia, Tasmania and Western Australia will be investigated.
Within Australia the site selection for nuclear power generation would come under the guidance of our nuclear regulator ARPANSA.
Some of the issues that will influence the selection of a region of interest would be:
In most nuclear powered nations such as France, Japan, and Korea, reactors are constructed as multiple units on each site. On the Technology page the scale of Nuclear for Australia has been identified as 59.2 Gigawatts of power in about 2040 requiring the construction of 53 reactors of the Westinghouse AP1000 size. It’s conceivable therefore that these reactors would be constructed at notionally 18 or more sites together with the required grid upgrades.