08/08/2012 - 07:46

To each technology its proper time and place

In his first Roundtable essay, Anthony Turton presented a perceptive analysis of the linkages among water scarcity, electricity demands, and climate change in South Africa. He also outlined inspiring ideas about easing that country's water constraints by using nuclear energy in the desalination of seawater. It is my view, however, that while Turton's ideas may be sound for South Africa, they have limited applicability in many other places -- including China.

If nuclear energy is to be developed in a sustainable fashion, cost-benefit ratios must always be kept clearly in mind -- and in different locations, nuclear power can present starkly different cost-benefit ratios. In developing countries with constrained water supplies and less constrained electricity supplies, it may make sense to use nuclear energy to desalinate seawater (and even to pump it to remote locations). But in developing nations where the population suffers from an urgent shortage of electricity, the idea of consuming a great deal of power to produce fresh water would seem to lack a firm economic basis.

China, a country whose economy and electricity needs are both growing rapidly, currently operates 15 nuclear reactors. More than one of these plants is used for desalinating seawater, but only when, as is the case with the Hongyanhe facility in Liaoning province, desalination is unavoidable. The pressurized water reactors at the Hongyanhe facility require a great deal of fresh water to operate, and the local supply of fresh water is inadequate for this purpose. Therefore, the plant has been designed to desalinate over 10,000 cubic meters of seawater daily for its own operation.

Significantly, the desalination technology that the plant has adopted is reverse osmosis. The choice is significant because reverse osmosis consumes less energy per unit of fresh water produced than do other desalination methods, rendering the energy needs and economic costs of desalination acceptable to the plant's operators. But -- according to an interview I recently conducted with a senior economist at China Guangdong Nuclear Power Group, the plant's owner -- the company has no plans to desalinate more seawater than the Hongyanhe facility needs for its own operation.

The company's decisions regarding desalination reflect a trade-off between water demands and power demands; such trade-offs are common in the developing world, where many countries require more water, more electricity, or both. I believe that, in a world where 1.5 billion people lack access to electricity, it is power demands that, on the whole, are more acute than water demands.

This is not to minimize the severity of water shortages in many countries, least of all in Africa -- where persistent drought in nations such as Sudan and Somalia has contributed to bloody conflicts in recent years. And because persistent drought in some regions is among the expected outcomes of global warming, it is hard not to associate drought-related conflicts with increased levels of carbon dioxide in the atmosphere. Therefore, so that the climatic challenges facing countries such as Sudan can be minimized, countries around the world must increase their efforts to reduce emissions of carbon dioxide -- for instance, through greater use of low-carbon energy sources like nuclear power. There is no guarantee that nuclear energy will forestall the worst effects of climate change, but hope at least lies in that direction.

Finally, I would take some issue with Turton's assertions that South Africa "has large reserves of thorium" and "is ideally positioned to utilize thorium-based power reactors." I find these statements too optimistic and perhaps oversimplified -- in view of the fact that India, a country with greater thorium reserves than South Africa, with well-known ambitions in thorium technology, and with 20 nuclear reactors currently in operation, nonetheless relies primarily on pressurized heavy water reactors at its nuclear facilities. Thorium-based power reactors are of course a wonderful idea. But like fast breeder reactors, they belong more to the future than to the present. Many years are likely to pass before thorium reactors become a mature technology.