Shortage of water a big threat to nuclear reactors
During the 2003 heat wave in France, which was responsible for more than 10,000 deaths, nuclear plants had to reduce their output, worsening the crisis. The rising temperature of river water meant they could not achieve sufficient cooling and still observe discharge limits
Nuclear and coal-fired power plants with OTC systems are especially vulnerable to droughts and heat waves because they rely on by far the largest volume of water withdrawals.
US energy supplies imperiled by water shortages, The Age May 1, 2013 - John Kemp Water and energy are inextricably linked.Power plants are the largest users of water in the United States, while substantial amounts of energy are needed to supply fresh water to homes, farms and factories and treat waste water prior to safe disposal.
Rising water consumption for hydraulic fracturing and production of biofuels, coupled with severe droughts in Texas in 2011 and across more than 60 per cent of the continental United States in 2012, have propelled that link up the policymakers’ agenda.
The threat to hydroelectric generation is obvious. But in 2007-2009, drought put the water supplies of 24 of the nation’s 104 reactors at nuclear plants at risk. In 2011, more than 3,000 megawatts of thermal generating capacity in Texas also was considered at risk of having to shut down if the drought persisted as reservoir levels plunged.
Texans were asked to conserve water to keep the lights on. The state was only spared blackouts because of high output from wind farms.
On April 25, the Energy and Natural Resources Committee of the US Senate held a hearing to explore the effect of drought on the energy sector and water management, reflecting lawmakers’ fears about the instability created by the tightening links between water and energy supplies.
Power and water
The United States withdrew 410 billion gallons of water from aquifers, rivers and the ocean every day in 2005, of which 350 billion gallons were fresh water and 60 billion gallons were saline or brackish, according to a US Geological Survey (USGS) report on “Estimated use of water in the United States” published in 2009.
Cooling systems for nuclear plants and power plants that burned coal, gas and oil accounted for 41 per cent of fresh water withdrawals and 49 per cent of all water withdrawals. That put them ahead of irrigation (31 per cent of total withdrawals) and public supply to homes and offices (11 per cent). The remaining uses including industry, mining, livestock and aquaculture accounted for less than 10 per cent combined…….
If there is insufficient water or it is too hot, power plants may be forced to close or cut output, which explains the near shutdowns of many power plants in 2007-2009 and again in 2011-2012.
On other occasions, low water levels forced power plants to turn down. During the 2003 heat wave in France, which was responsible for more than 10,000 deaths, nuclear plants had to reduce their output, worsening the crisis. The rising temperature of river water meant they could not achieve sufficient cooling and still observe discharge limits, Michael Webber of the University of Texas Energy Institute told senators.
Nuclear and coal-fired power plants with OTC systems are especially vulnerable to droughts and heat waves because they rely on by far the largest volume of water withdrawals. Combined-cycle gas plants are much more efficient. And gas turbines, solar and wind generators use negligible quantities, Webber testified.
Options for reducing the power sector’s vulnerability include switching the type of fuel from nuclear and coal to gas, solar or wind; switching to recirculating or dry and hybrid wet-dry cooling systems; or switching the water source from fresh water to saline or waste water. The drawback is the capital cost and reduced efficiency of the plant. Cleaning waste water so it can be used in the cooling system or using a dry cooling mechanism imposes an “energy penalty” on the plant’s efficiency.
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