Antinuclear

Nuclear cost and water consumption – The elephants in the control room,

A key issue with nuclear plants is cooling. Because of the cost of shutdowns and the degradation of materials by irradiation, the plants are designed to run at lower peak temperatures (260-320 C) than coal (500-670 C), gas turbines (1,300-1430C) or internal combustion plants (2,000 C).

The thermal efficiency of a plant is directly related to the difference between the peak temperature and the cooling medium – what is termed Carnot efficiency.

Lower temperature means lower efficiency, as less of the heat energy is converted into work and more is removed by the cooling system. So for a given amount of electrical energy delivered, more cooling is required in a nuclear plant. Furthermore the warmer the cooling water or air the more coolant is required.

Thus the Barrakah plants require 100 tonnes of Gulf seawater per second for each generator. In higher latitudes with seawater temperatures in the range of 2-12C, water requirements can still be 40-60 tonnes per second per GW.

Just to put that in perspective Melbourne Water supplies 15-20 tonnes per second to the entire Metropolitan area of almost 5 million people. Even so, the water temperature is raised by 7-10C which is enough to kill any fish larvae unfortunate enough to be sucked into the cooling intakes.

It is enough to change the local environment for all sea life, so finding a suitabable site is very difficult. There are currently no nuclear plants operating using warm seawater for cooling although Barrakah is soon to be commissioned.

The problem there is not just the temperature but the accelerated rates of corrosion and biofouling which will mean the heat exchangers need to be larger, pumping losses will be higher and maintenance bills higher still.

Perhaps the area near Portland in Victoria might work, but then the 500kV line would have to be triplicated to carry away the power, further adding to the cost. Plants at the edges of the grid have a whole lot of other issues so a South Australian plant would be extremely difficult to integrate.

On land in very cold climates, a small number of air cooled plants have been built but the offset is that about 5% of the output of the power plant is used to run the fans. However in warm climates it is virtually impossible to run an air cooled nuclear power plant.

It would require in the order of 450-500 tonnes of air per second to be moved over the heat exchangers per GW of electrical output. At typical air velocities for cooling fans that would have a fan area of 75,000 square meters or if each fan was the cross section of a shipping container, 17,000 fans.

It is enough to change the local environment for all sea life, so finding a suitable site is very difficult. There are currently no nuclear plants operating using warm seawater for cooling although Barrakah is soon to be commissioned.

The problem there is not just the temperature but the accelerated rates of corrosion and biofouling which will mean the heat exchangers need to be larger, pumping losses will be higher and maintenance bills higher still.

Perhaps the area near Portland in Victoria might work, but then the 500kV line would have to be triplicated to carry away the power, further adding to the cost. Plants at the edges of the grid have a whole lot of other issues so a South Australian plant would be extremely difficult to integrate.

On land in very cold climates, a small number of air cooled plants have been built but the offset is that about 5% of the output of the power plant is used to run the fans. However in warm climates it is virtually impossible to run an air cooled nuclear power plant.

It would require in the order of 450-500 tonnes of air per second to be moved over the heat exchangers per GW of electrical output. At typical air velocities for cooling fans that would have a fan area of 75,000 square meters or if each fan was the cross section of a shipping container, 17,000 fans.

In other cases straight through cooling is used from large rivers or lakes. The Murray at the South Australian border is often down to 9 GL/day or even less. 9 Gl/day is about 105 tonnes/second, and so a single unit nuclear power plant located on the Murray would often need the entire flow to cool it, while heating the water by 8-12 C.  This is obviously an environmentally impossible situation.

That is why cooling towers are the most common cooling method because they are the most efficient. Evaporating water carries away much more heat than liquid flows.  In typical Australian conditions the nuclear plant would evaporate between 20 and 24 GL per year per GW so a two unit 2.2 GW plant like Plant Vogtle currently under construction in the US would need 44-50 GL/ year.

That is more than the 4.7 GW of coal in the Latrobe Valley and almost 30% more than the entire demand served by Barwon Water which includes 320,000 people and all their business homes, parks and gardens. At current spot prices for irrigation water that would be an additional cost of $50m per year.

In summary, in a hot dry continent like Australia, providing cooling water for a nuclear power plant would prove a huge cost and distortion to the water industry.

There are many other issue with nuclear power, including a lack of flexibility, large and long duration backup requirements for refueling and outages and large spinning reserve requirements, but these can be explored at another time…….https://www.openforum.com.au/nuclear-cost-and-water-consumption-the-elephants-in-the-control-room/?fbclid=IwAR2M3NxMjfrDJNWTG9tatKSARHGUKWVcG_CE-bSW5wtnAbwhGnYxd1ElugU