Civilian Marine Nuclear Propulsion

The 22,000 tonne US-built NS Savannah, was commissioned in 1962. It had a 74 MWt reactor delivering 16.4 MW to the propeller.
The 1960s era US civilian nuclear power vessel, Savannah, functioned as both a cargo and a passenger ship.

For a few brief years during the Kennedy and Johnson administrations, the vessel was a nautical superstar, touring the world as an ambassador for the peaceful use of nuclear energy and playing host to royalty. In May 1964, it drew more than 13,000 visitors during a call here.

...Still owned and maintained by the Federal Maritime Administration and regulated by the Nuclear Regulatory Commission, the ship is occasionally opened to visitors. Groups can arrange tours by request, as long as they don't expect too much in the way of air conditioning, elevators or other modern comforts. _LATimes

The German-built 15,000 tonne Otto Hahn cargo ship and research facility sailed some 650,000 nautical miles on 126 voyages in 10 years without any technical problems. It had a 36 MWt reactor delivering 8 MW to the propeller.

The 8000 tonne Japanese Mutsu was the third civil vessel, put into service in 1970. It had a 36 MWt reactor delivering 8 MW to the propeller. It was dogged by technical and political problems and was an embarrassing failure. These three vessels used reactors with low-enriched uranium fuel (3.7 - 4.4% U-235).

In 1988 the NS Sevmorput was commissioned in Russia, mainly to serve northern Siberian ports. It is a 61,900 tonne 260 m long LASH-carrier (taking lighters to ports with shallow water) and container ship with ice-breaking bow. It is powered by the same KLT-40 reactor as used in larger icebreakers, delivering 32.5 propeller MW from the 135 MWt reactor, and it needed refuelling only once to 2003.

A more powerful Russian icebreaker of 110 MW net and 55,600 dwt is planned, with further dual-draught ones of 32,400 dwt and 60 MW power at propellers. The first of these third-generation icebreakers is expected to be finished in 2015 at a cost of RUB 17 billion. _WorldNuclearNews

The Russians are devoting a good deal of effort to the development of a floating nuclear infrastructure that can be used to develop rich Arctic energy resources. To this point, no other nation's industries are as devoted to the development of non-military nuclear marine propulsion.

The world's naval forces have a good safety record with regard to nuclear marine propulsion. More from Rod Adams:

No Western nuclear ship has been lost because of a power failure.

Nuclear propulsion is clean. A nuclear engine can push a sealed submarine for months at a time without affecting the atmosphere in the ship.

Nuclear engines can be very powerful for a given total propulsion plant weight. Though the exact numbers are classified, it is obvious that an engine that can drive an 80,000 ton aircraft carrier at 35 knots into the wind while launching aircraft with steam driven catapults has a significant power capacity.

Based on the amount of payload on nuclear carriers compared to fossil fuel driven carriers, the nuclear engines require less space and weight than the oil fired steam turbines that they replaced.

Purely on capability, nuclear power is worth a look. Cost is a hurdle, however, since aircraft carriers and large submarines are several billion dollar machines. _RodAdams

High cost is a problem for civilian applications, and the highly-enriched nature of the fuel used in marine reactors could also be a problem.

they deliver a lot of power from a very small volume and therefore run on highly-enriched uranium (>20% U-235, originally c 97% but apparently now 93% in latest US submarines, c 20-25% in some western vessels, 20% in the first and second generation Russian reactors (1957-81)*, then 45% in 3rd generation Russian units, 40% in India's Arihant)

...The long core life is enabled by the relatively high enrichment of the uranium and by incorporating a "burnable poison" such as gadolinium - which is progressively depleted as fission products and actinides accumulate. These accumulating poisons would normally cause reduced fuel efficiency, but the two effects cancel one another out.

However, the enrichment level for newer French naval fuel has been dropped to 7.5% U-235, the fuel being known as 'caramel', which needs to be changed every ten years or so. This avoids the need for a specific military enrichment line, and some reactors will be smaller versions of those on the Charles de Gaulle. In 2006 the Defence Ministry announced that Barracuda class subs would use fuel with "civilian enrichment, identical to that of EdF power plants," which may be an exaggeration but certainly marks a major change there. _NWN

The French use of 7.5% U-235 is a promising development, which could help open the way to easier approval for civilian marine reactors.

Another promising trend for civilian nuclear marine power is the development of factory-built and transportable small modular reactors (SMRs), which are being designed to provide power anywhere between 25 MW and 250 MW. Many of these smaller designs could be fitted onto a large ship, perhaps in multiple-reactor configurations.

One other application for civilian nuclear marine propulsion which should be mentioned, is the civilian seastead. A seastead is a permanent floating workplace and residence for large numbers of people. Well designed seasteads could float the open oceans, performing many jobs which require long periods of time offshore. Nuclear power is a natural fit for such floating cities.

Most naval reactors can go 10 years or more without re-fueling. This is a definite advantage for extended cruises. And nuclear fuel is relatively inexpensive, in comparison with fossil fuel costs. It is the up-front costs for nuclear power which represent the greatest expense. And those up-front costs represent enormous opportunities to the innovative engineer.

Ireland and New Zealand: Seaweed Leaders?

Island nations, Ireland and New Zealand, are located almost precisely diagonally half a world apart from each other--both North and South, and East and West. Interestingly, both Ireland and New Zealand are looking at ways of making a common natural resource--seaweed--an increasingly profitable enterprise. Seaweed is a type of multi-cellular algae that can be quite prolific in areas where other plant life is scarce.

'Compared to other bioenergy crops (eg rapeseed, canola, peanut, oil palm) there are a number of species of algae that have higher areal productivities, higher oil content and that can grow in saline waters.

'These apparently very favourable properties have generated a frenzy of interest and activities in the field of energy production using algae, both microalgae and seaweeds.'

He continued, 'For biofuel production the algal biomass needs to be produced at a cost of around $US1 or less per kg. In order to achieve this ambitious goal there is the need for year-round reliable high productivity algal culture and all factors (eg, algae strains, algae culture, harvesting and further downstream processing) need to be optimised and efficiently integrated.'

Ireland boasts 16 commercially useful seaweed species, with additional species being added as more research is carried out. Ireland's location off Western Europe, surrounded by clean seas, is a major selling point to the world market. __BioenergyCheckBiotech

New Zealand also has a long tradition of seaweed cultivation, and Air New Zealand is one of the airlines looking at seaweed, algae, and oil seeds to fuel their fleet.

Most likely, to replace petro-fuels with biofuels, it will be necessary to use significant areas of both land and ocean for growing fuel crops--until advanced synthetic biology finds ways to boost bio-production far beyond current known limits.

Japan, Korea, and China are other countries making use of extensive seaweed cultivation. But coastlines alone may not be enough. As discussed previously, artificial islands or seasteads may become important "ocean farms" for production of bio-energy--turning vast regions of mid-ocean "deserts" into scattered oasis, teeming with useful life.

Mariculture Biofuels--Seaweed to the Rescue!

The oceans of Earth are considered the birthplace of life. Oceans receive most of the sunlight and absorb and convert most of the CO2 produced by nature--including humans. Now mariculturists are experimenting with seaweed a partial solution to the world's energy price crisis. Understand? Sunlight plus CO2, a priceless combination for plant life.

The oceans are the largest active carbon sink on the planet, covering more than 70 per cent of its surface area, and are predicted to grow as sea levels rise. Our seas also receive a larger proportion of the world's sunshine than land does, particularly in the tropical and subtropical belt where land is scarcer.

To agriculturalists, the oceans are vast and grossly underused fields well provided with sunlight and water.

...In Costa Rica and Japan, seaweed farming has been re-established to produce energy. It can quickly yield large amounts of carbon-neutral biomass, which can be burnt to generate electricity. High-value compounds — including some for other biofuels — can be extracted beforehand.

We have calculated that less than three per cent of the world's oceans — that's about 20 per cent of the land area currently used in agriculture — would be needed to fully substitute for fossil fuels. A small fraction of that sea area would be enough to fully substitute for biofuel production on land.
_CheckbiotechBioenergy

Three percent of the world's oceans to fully substitute for fossil fuels? What about using seasteads as centers of mariculture, in addition to all the other renewable energies they will utilise?

How difficult would it be to create an oasis of sea life on the normally life-depleted "desert" of the high seas? Most sea life lives along island and continental shores, and continental shelves and seamounts. What could a serious movement into seasteads do toward expanding life in the oceans?

More on OTEC and Energy Island

Ocean Thermal Energy Conversion (OTEC) is at the center of the Energy Island concept. OTEC was invented by Frenchman Georges Claude in the 1920s. The idea is simple: use the approximately 20 degrees C difference in temperature between the deep ocean and tropical surface ocean to drive a heat engine. Besides producing megawatts of electric power, the byproducts of the process include clean freshwater for drinking and growing crops, and plenty of air conditioning.

There are two basic versions of the technology. The first operates in a "closed cycle", using warm surface water to heat ammonia, which boils at a low temperature. This expands into vapour, driving a turbine that produces electricity. Cold water from the depths is used to cool the ammonia, returning it to its liquid state so the process can start again.

The "open cycle" version offers the added benefit of producing drinking water as a by-product.

Warm seawater is introduced into a vacuum chamber, in which it will boil more easily, leaving behind salt and generating steam to turn a turbine. Once it has left the turbine, the steam enters a condensing chamber cooled by water from the depths, in which large quantities of desalinated water are produced - 1.2 million litres for every megawatt of energy.

A 250MW plant (a sixth of the capacity of the new coal-fired power station that has just won planning permission in Kent) could produce 300 million litres of drinking water a day, enough to fill a supertanker. Using electrolysis, it would also be possible to produce hydrogen fuel.

Telegraph
The map below displays the ocean area where the temperature difference between surface waters and the deep ocean is great enough to allow large scale economical OTEC . By placing a site close to an arid coastline, an OTEC energy island could make a huge difference in quality of life--by providing reliable electric power, plentiful fresh water for drinking and crop irrigation, and chiller-based air conditioning.
Energy island based seasteads could also provide a nucleus for burgeoning aquaculture--based upon the nutrient-rich deep ocean water routinely pumped into the OTEC generator.

Projects for Harvesting the Energy and Other Riches of the Ocean

Energy Islands are floating modular renewable energy platforms that incorporate photovoltaics, solar thermal towers, wave energy, ocean current energy turbines, wind turbines, and OTEC (ocean thermal energy conversion). Designed by architect Alex Michaelis, the concept is aimed at capturing a share of Richard Branson's Virgin Earth Prize.

Each island would be built on a floating platform and at its centre would be a plant that converts heat from the tropical sea into electricity and drinking water. Below deck would be marine turbines to harness energy from underwater currents and around the edge floating devices to provide wave power.

Vegetable farms and homes for workers will complete the colony and the power will be piped back to be used on the nearest populated land mass.

Michaelis, who is working together with his father Dominic, an engineer, estimates that each island complex could produce 250MW.

NextEnergy

Combining enough Energy Island modules to form the outside of a protected lagoon, you would be on your way to renewable power, agriculture, and aquaculture for your floating city.
Aquarius is the sea-colony concept from Marshall Savage, writer of The Millenial Project. Self-sufficient Aquarius floating cities would be the first step to colonising the galaxy. The lessons learned from building sustainable and profitable colony-cities-on-the-ocean could be transferred to floating cities in outer space.

A different group has coalesced around the concept of "Seasteads". For the seastead movement, building a sustainable floating city is an end in itself.

In the past, pioneers and malcontents would head to the frontiers, of which few now exist. The oceans, which make up 71% of the earth's surface, have always been a place for those seeking new ways of life. They are the last great unclaimed region. Ships are not well suited for permanent living, but by creating new land on the oceans we can achieve both freedom and a reasonable degree of comfort.

Freedom of movement and self-sufficiency are both intimately connected with political freedom. Fixed locations such as seamounts, islands, and atolls are much more vulnerable to the whims of nearby governments [minerva link], but a mobile seastead can always move if the political climate becomes unsuitable. While a seastead is likely to import many goods, being able to supply its own basic necessities will also add greatly to its independence. This approach to nation founding reduces - but does not eliminate - the difficulty in finding sovereignty, by operating in international waters...If the seastead is parked in area that does not get regular rain storms an alternative method of fresh water replenishment is needed. Either sea water distillation or reverse osmosis will work. Both forms of sea water reclamation require pretty hefty amounts of power. Distillation can be done with solar evaporation trays and condensers; whereas reverse osmosis runs off of electricity....

Seastead Book
Seascape One, pictured above, is a combination tourist destination and high-end condominiums designed to float around the Mediterranean Sea. It incorporates multiple renewable energy features, including wind and solar power. The tall white structure projecting above the living section is a solid sail, for clean (but slow) propulsion. Lessons learned from operating such a design should be applicable to a more rough weather seastead.
Paolo Soleri designed floating arcologies which could also be classified as "seasteads." The "Nexus" floating city project is more than a little based on a Soleri design.

This is a floating city designed to accommodate 100,000 persons. 7 kilometers long and 4 kilometers wide with the capacity to be mobile, grow its own food, produce its own electricity and, owing to it existing beyond the 12 mile governmental jurisdiction boundaries, create its own government, income system and tax base. In essence, this mobile city becomes its own independent country....The city utilizes several different types of electrical power generation. Five Ocean Thermal Energy Conversion units are positioned at strategic zones of the city to supply electricity. Banks of freestanding windmills and photovoltaic solar cells produce additional electricity. The "head" of the floating city is a small mountain range with a specially designed frontal structure that cuts Tsunami tidal waves into smaller, manageable waves with little destructive effect. It is a tidal wave barrier that requires the city to head into the on-coming wave.

Nexus

The video above is a graphic portrayal of some of the aspects of the "Energy Island" concept--the UK project that wants a piece of the Virgin Prize.

A safe, self-sufficient living structure in mid-ocean for thousands of residents would require considerable care in design and testing--long before it was ever built or floated. The ocean is a dangerous environment under the best of conditions. Any floating structure destined to remain in mid-ocean would eventually see the ocean in all of its moods. Hurricanes, deadly squalls, typhoons, giant rogue waves, perfect storms, etc. The seastead would have to be built to survive anything it could not avoid.

From Alfin2100