The Lesson from Fukushima

control room

By Harry Valentine 2015-08-15 01:39:58

Thermal power stations that produce steam to drive turbines require cooling systems to condense turbine exhaust steam so as to continuously recycle massive volumes of purified water within the power station. 

Air and water are the two choices for cooling, with seawater providing some 3,600 times the cooling capacity as the identical volume of air at atmospheric pressure. 

It is cheaper to install a water-based cooling system than construct several massive cooling towers in close proximity to each other. As a result, many thermal power stations worldwide are located next to a river, lake or ocean coast.

Oversized Coastal Waves

Japan’s Fukushima nuclear power station was built close to maritime sea level along a coast that experienced frequent cyclones and earthquakes, increasing the risk of occasional over large sea waves striking the coast. 

An overly large sea wave breached the sea wall at New Orleans during a tropical storm, devastating entire neighborhoods built below sea level. An overly large sea wave breached the 50 feet high sea wall at Fukushima and flooded the lower levels of the nuclear power station. However, Japan has successfully operates other water-cooled nuclear power stations at other ocean coastal locations, without incident.

The lesson from Fukushima is that future water-cooled coastal nuclear power stations would best be built away from known or suspected earthquake or tsunami zones with the lowest levels of the power station at an elevation above tsunami height of sea waves. 

There are many coastal mountains worldwide as well as coastal plateau of sufficient elevation where a site may be excavated for a thermal power station. A pump-driven, closed-circuit pipe system may connect between the power station to provide cooling and a heat exchanger submerged under seawater at a location protected from powerful waves or incoming super-tidal currents.

New Nuclear Power

At the present time, some 70 new nuclear power stations are either under construction or will soon begin construction, worldwide, with many more planned for the future. Researchers and scientists in China, India and the United States are working on developing thorium-based nuclear power, while researchers in the U.S. have also been exploring future possibilities in radiation-free nuclear fusion power. 

Future nuclear power stations will require cooling systems and water cooling is a cost-competitive option against building massive cooling towers at suitable oceanic coastal locations. Such locations offer future options to the maritime transportation sector.

When a nuclear or thermal power station is located along an ocean coast, there may be scope to build a maritime terminal within close proximity to the power station, allowing ships to deliver massive amounts of coal or biomass to a conveyor that connects directly into the power station. 

Ships may also carry nuclear ore to a coastal power station or allow for more easily accessible maritime transportation of nuclear components. A coastal nuclear or thermal power station could also supply energy directly to some forms of rechargeable energy storage systems located on board ships.

Maritime Battery Propulsion

Battery powered ships and ferries have recently been introduced into short-distance maritime transportation service, allowing such technology to receive an energy recharge directly from the power station. The solar thermal power industry has developed heat-of-fusion and also heat-of-chemical-decomposition thermal storage batteries that can offer greatly extended service lives compared to electro-chemical storage batteries. 

For large-scale, short-distance maritime transportation, super-sized tugs carrying batteries may push and navigate mega-scale size of barges of up to 200,000 tons. Tugs of 80,000 tons deadweight could carry insulated chambers of heat-of-fusion compound to provide 200 to 500 nautical miles of propulsion.

Insulated steam lines between coastal power stations and maritime terminals could provide access to thermal reheating of the thermal storage compound that could generate steam to drive propulsion engines. 

While the optimal thermal storage compound is a mixture of 80 percent lithium hydroxide and 20 percent lithium fluoride, offering over 1100KJ/kg storage at 450⁰C, the present and projected market demand for lithium raises its price. The combination of 48 percent sodium chloride and 52 percent magnesium chloride offers 430 KJ/kg storage capacity at the same temperature and could offer perhaps 200 nautical miles of propulsive power at 35,000kW.

Conclusions

Despite opposition to nuclear power, some 70 new nuclear power stations may be expected to enter service over the next five years, several of them being located along an ocean coast and being cooled by seawater. Other seawater-cooled thermal power stations powered by concentrated solar thermal energy, biomass and clean coal technologies are also expected to open within the next few years. 

Coastal power stations could directly supply propulsive energy to various electrical and thermal battery-powered ships and tugs. The projected future cost of oil and natural gas will determine the pace at which battery-powered vessels will enter service.

The opinions expressed herein are the author's and not necessarily those of The Maritime Executive.