How nuclear icebreakers work - and the reversible ships that will replace them


December 20, 2011

MT Tempera, one of the new class of double acting reversible ships, going backwards to act as an icebreaker

MT Tempera, one of the new class of double acting reversible ships, going backwards to act as an icebreaker

Image Gallery (22 images)

The Arctic North end of Russia is believed to hold as much as a quarter of all the world's oil deposits - an utterly monstrous economic prize, hidden in one of the toughest and least hospitable environments on the planet. Getting to this prize, and then transporting it back to refineries, is a monolithic task that requires one of the most awe-inspiring pieces of machinery man has ever built - the nuclear icebreaker. Purpose-built to the point of being almost unseaworthy on the open waves, these goliaths smash their way through 3-meter (10-foot) thick ice crusts to create viable pathways for other vessels - but fascinating new technologies could mean the days of the dedicated icebreaker are numbered.

Making hay in the Arctic

Where there's a well, there's a way. An oil well, that is. Black gold. Texas tea. And some of the world's richest reserves of the stuff are buried beneath the beds of the Berents sea, North of Russia and well into the Arctic Circle. It's estimated that this area holds somewhere around a quarter of all the oil reserves in the world.

But it's an area that gets no sun at all for at least one day every year, and which is so cold that the sea itself freezes over with 2-meter (6.5-foot) thick ice for more than two thirds of the year. When it's not frozen over, there's 12-meter (40 foot) waves to deal with. It's one of the world's most extreme environments; inhospitable doesn't even begin to cover it.

Here's a satellite photo of the top left corner of that map, showing just how much ice we're talking about in wintertime.

Getting resources like oil and natural gas out of the earth - and safely back to shore - would be prohibitively expensive, if the prize wasn't worthwhile. Where these sorts of quantities of fossil fuels are concerned, however, all bets are off and just about any expense can be justified.

... and the expense we'd like to take a look at today is the nuclear-powered icebreaker - a vessel whose sole task is to smash its way through packed sea ice and clear a path for other ships to follow in.

It's a specialist job that boats have been designed to tackle since the 1830s - and it's interesting to note that while today's enormous icebreakers generally use nuclear power to generate the immense thrust needed to power through the ice fields, in other ways the design hasn't changed too much for nearly 200 years.

How icebreakers work

So, let's take a look at how they work. For starters, where a regular ship has a pointed bow to slice through the waves, an icebreaker's bow is a much smoother shape, almost like the back of a spoon. When the ship hits ice, the smooth bow causes the front end of the ship to ride up on top of the ice, so the vessel's immense weight can then crush it from above.

It's a truly extraordinary sight in motion.

The hull is shaped to push the crushed ice out of the way of the ship's propulsion system, where it could cause significant damage. The hull is strengthened and reinforced to deal with the additional stress it has to handle, and it's also coated with a low-friction solution that makes it easier to glide over the ice rather than catching or grabbing as it rides over.

The final main element to an icebreaker is enormous power - and for this, it's worth taking a look at the greatest icebreaker ever to ride the White Sea: Russia's NS 50 Let Pobedy (50 лет Победы, which translates to 50 Years of Victory).

The 50 Let Pobedy is 159 meters long (524 ft) and weighs 23,439 metric tons (25,837 tons). That's peanuts next to the massive tankers and container ships it clears a path for, but it makes it the largest icebreaker in the world.

Nuclear Power - the only practical choice for Arctic icebreakers

In order to constantly provide enough power to shove that bulk up over mile after mile of ice, the 50 Let Pobedy (let's just call it the Victory) runs a pair of nuclear reactors that generate a combined 55.2 megawatts (74,000 horsepower), which hits the water through three electric propulsion motors.

Why nuclear? Well, to put it simply, the fuel demands of the task at hand would be outrageous using any other power source. Burning diesel, the Victory would use more than 100 tons (90.7 metric tons) of fuel a day, and have a severely restricted range as a result. But running on nuclear power, she burns less than half a kilo (1 pound) of uranium even on the toughest day, at constant full power across 2.8-meter (9.2-foot) thick ice.

With nuclear reactors on board, fuel stops become almost a thing of the past - a handy feature considering they work in extremely remote areas and have no other compelling reason to come in to port. In fact, the world record for endurance is held by one of Victory's older cousins, the Arktika, which stayed in service on the ice for 357 days without entering a port once.

In fact, the specific needs of icebreaking vessels make them one of the only cases where nuclear propulsion is economically practical - barring nuclear submarines, which take advantage of the fact that the reactors don't require oxygen to run. Nuclear reactors are more expensive to build than combustion engines, and enriched uranium doesn't come cheap - but at the end of the day, by virtue of sheer volume, the fuel costs end up being much, much lower than an equivalent diesel engine.

No, the main issue is insurance. Imagine trying to insure one of these things, given the catastrophic and lasting damage that could occur in the "unlikely event" of an accident. Luckily, so far, there has not been a major incident.

Icebreakers - almost unseaworthy outside their element

Icebreakers are an excellent example of a laser-focused vehicle. In the same way as a half-million dollar sports car can be a real pain around the speed humps and u-turns of the city, these goliaths of the Arctic are very poorly designed for operation outside their specific envelope.

The key element here is that rounded bow. A shape best suited to riding up on ice shelves and crushing them from above, it causes the ships to roll from side to side in the waves when sailing on open water, making for a very seasick ride for the crew.

When the seas come up (remember those 12-meter waves we spoke about earlier?) the shape opens itself up to another problem - where a typical pointed bow can pierce through an oncoming wave, greatly reducing its effect on the boat, the rounded bow of an icebreaker lets the water slam into it at full force.

These are certainly not comfortable vessels on the open water. Even once on the ice, the crew has to deal with the constant jarring and shuddering of ice breaking beneath the boat, as well as the low, constant rumble it produces.

A relatively new development in engine design, however, might put dedicated icebreakers out of service for all but the thickest surfaces.

Double-acting reversible tankers - ships that go both ways

In the 1990s, a new class of propulsion device was designed. Previously, most ships had a fixed propeller system which could run either in forward or reverse, and some sort of rudder arrangement for steering, but the development of the azimuth thruster pod instantly changed the state of the game.

These hardy propulsion pods hung under the ship's hull, housing a motor and propeller, with the ability to rotate each pod 360 degrees to provide thrust in any direction. This makes the ships much more maneuverable.

It turns out, the pods also have a special advantage in icebreaking applications. These "Azipod" propulsion units typically have their propellers facing forwards and operate in a pulling motion to take advantage of an untroubled stream of water. When you turn them 180 degrees and run the ship backwards, it turns out that the intense agitating power of the Azipods can actually help break ice from underneath.

In fact, ships running astern (backwards) with Azipods leading the way have proven to be significantly more efficient at breaking ice than ships with the same bow shape running with rear propulsion.

This means that you can build ships with an icebreaking bow and Azipods at the rear, and a regular wave piercing bow at the front - double-acting reversible ships that can efficiently drive forward in the open sea without any of the roll effect of a dedicated icebreaker, but that can turn tail and run butt-first if they run into sea ice and need to smash through it. They can perform both jobs with high efficiency, while carrying cargo.

Here's an example, the MT Tempera - one of the first double acting cargo ships. Here she is running ahead in open water:

And backing up to break through the ice:

These double-acting ships, many of which are now in operation, more or less render the dedicated icebreakers obsolete where the ice is only a meter or a meter and a half thick - which opens up a lot of shipping routes. But the big boys like the 50 Let Pobedy are still needed when the going gets really tough with ice beyond 2 meters thick.

I hope you've enjoyed this quick overview - the icebreaker and double acting ship class is such an impressive answer for such a specific problem in such a harsh environment that we thought it was worth a feature.

About the Author
Loz Blain Loz has been one of Gizmag's most versatile contributors since 2007. Joining the team as a motorcycle specialist, he has since covered everything from medical and military technology to aeronautics, music gear and historical artefacts. Since 2010 he's branched out into photography, video and audio production, and he remains the only Gizmag contributor willing to put his name to a sex toy review. A singer by night, he's often on the road with his a cappella band Suade. All articles by Loz Blain

very interesting article, I learned something new today, thank you


What an excellent article Loz - and glad you\'re still with us after your little incident months ago.

Todd Dunning

Why is its butt called the Mastera?


Sorry Ozuzi, my mistake, the Mastera is the Tempera\'s sister ship.


Nice article indeed! Just a question, was the azimuth thrust unit (or Z-drive) not already developed in the 1950\'s ? If memory serves me right, it was the founder of the schottel company in germany who made the first models.


Interesting article, thanks. How much does one kilogram of enriched uranium (and non-enriched) cost compared to the diesel (and how much would that cost?)

Renārs Grebežs


Raja Sekaran

Very interesting thank you for sharing!


Thanks for taking the trouble, much appreciated. (A weekly in-depth item would be a good selling point for the site.)

Mel Tisdale

\"Here\'s an example, the MT Tempera\" at first I thought the name was written in reverse on the other photo (just to confuse!) but reading your comment set things straight!

Have come across these before but nice to see such an informative (as always!) and well-written article on Gizmag.. Thanks!! ;-)


Great article!


Sometimes the incredible stupidity of corporate greed defies belief. Arctic ice is melting at an alarming rate due to climate change helped along by massive global oil consumption. Meanwhile, these oil companies are pushing channels through the Arctic, assisting the ice break up, to try to get more oil. These idiots should be arrested and put in a prison on a low-lying island in the South Pacific.

Kiwi Mark

Kiwi Mark, you need to complain to the people who drove their cars to work today, not the oil companies.

Captain Obvious

Nice idea but I\'d worry excessively about the propellers hitting hitting a piece of ice driven under the ice sheet by a previous icebreaker or storm.

Fluid dynamics is weird but I wonder if you could get better efficiency by putting the propeller pods on rams so that they could be lowered in deep water but raised for shallows.

Nuclear reactors are expensive because nobody ever set up an assembly line to produce them. Granted enriched uranium is expensive but there are at least 2 reactor types that don\'t need enriched fuel and produce \"enriched\" fuel as a byproduct. the real expense of nuclear power is dealing with the constant ludicrous protests and lawsuits from the green fascist.


Kiwi Mark I have some news for you: It is not 2006 anymore. You are just embarrassing yourself. Don\'t worry, it\'s possible for you to be successful and happy without jealousy of others who are successful and happy.

Todd Dunning

Thank you for the well written and interesting article.


I can\'t be the only one that feels that taking nuclear reactors into the environment to get to the number 1 cause of Global Warming isn\'t really a smart move. On the upside, such activities will probably get rid of the ice so they won\'t need ice breakers. Oh wait! That will probably get rid of HUMANS too! Insane!


This was a most interesting and informative article. While global warming may well reduce the amount of polar ice, there will still be a need for icebreaker ships in the future to help address the inevitable and necessary exploitation of Arctic and Antarctic resources. Indeed, if the ice season is reduced there will be more open sea conditions to cope with so the double-acting reversible funcion design and rotatable drive - with one end as a rounded icebreaker and the other as a sharply pointed wavebreaker - will become important. \"Gizmag\" is one of my favourite e-mail information services. There is always something of great interest and sometimes information can lead to new business and investment opportunities. I have recently had to purge my inbox of many newsletter subscriptions as I did not have the time to read them all but \"Gizmag\" remains as essential reading!


Good attempt to make a sorry story interesting. Cleaner energy is available without all this drama. Those oil barons will be buying your news networks and politicians with this oil money. Think consumer owned solar PV rooftops and electric cars. Quit supporting these idiots who are killing your grandchildren with fossil fuel pollution.


Very good article. A few things are notworthy: 1. It should be interesting to know that with the price of oil ever increasing, nuclear power becomes interesting for cargo ships and oil tankers as well. 2. Todays large cargo ships are among the worst polluters. In fact replacing all of them with nuclear powered ships would greatly reduce global warming. 3. Some people here seem to be quite concerned about the melting of the Arctic ice. This is not really such a big deal however. Ice that swims on water displaces the same amount of water that it contains. So if that melts, it has no effect on the water level whatsoever.


skipjack, your third point is true, but neglects that melting won\'t stop at the littoral zone

the antarctic will melt too, but it\'s largely not sea ice, but terrestrial icing on rock

personally i am sceptical of anthropogenic climate change being the biggest driver, but we certainly come in at #1 for pollution and wastage of resources

a species that embraces bottled water in plastic as a clever concept are patently idiots


1 like here

Dawar Saify

Damn-straight, ash. We\'re idiots.

Great article, Loz. Definitely appreciate the extra background on something I knew nothing about.

Chris Hooley

Kiwi Mark! Send me to a \"prison on a low-lying island in the South Pacific.\" Right now it\'s 19 F (-7C) outside. I could use a bit of Climate Change.

Come on, man. Hook a brother up?


Why not use a custom made laser gun/s ( as whaling ships use a harpoon canon ) to penetrate or fracture the ice crust immediately ahead of the bow to allow the ship to more easily pass through . Less steel needed to build the ship and far less energy to propel it .

George Krooglik

I really like all the Youtube videos on ice breakers.....

Some pretty fascinating things going on.

Not keen on whoring up the remaining oil reserves though.

Mr Stiffy

Great video but I want to know how thick that ice was.

The Hoff

\" utterly monstrous economic prize,...\"

Which by rights belongs to the entire planet but which will undoubtedly find it\'s way into the private grasp of a few companies which will profit off of a natural resource belonging to everyone.. While everyone else will bear the burdens of environmental clean-up (sand probably subsidized exploration and extraction, the few, the wealthy, the connected will acquired even more control over public resources for private profit.

Charles Barnard

If we somehow were able to extract and burn up all the fossil fuel which has been kept underground for the millions of years it took to form that fuel, we will raise the average temperature of the Earth by at least 10F. That is simply suicidal to future generations of both humans and animals.

Bob Carver

Um, I think pics 4 & 5 in the image gallery might be mixed up in relation to their captions...unless that\'s one strong propeller blade.

C. Walker Walker

oops. that\'s what I get for not reading all the way to the end first. I\'ve learned nothing from the reading comprehension section of the standardized testing of my youth.


C. Walker Walker

re; Bob Carver

do you really believe that nonsense, or do you believe that you will be part of the ruling class with access to all the luxuries?


It seems a bit silly having a nuclear powered boat travelling all that way burning half a ton of uranium a day when it could sit in one spot. our current world needs fuel but if were willing to invest our nuclear technology into fuel luggers we should be a bit more open to nuclear power.


Wrong use of the word \"monolithic\" in the article:

To say \" is a monolithic task \" means using the term in the context of a building or in the use of describing an activity with stone-like qualities\". It is not to be used when describing a \" massive/time-consuming/mind-boggling task \".

Thanks, Jay


Before anyone comments on the ice breaking/global warming/ save the polar bears stuff, let me say this. Ice breaks. The freaking Polar Bears are fine. If a species is over-specialized for a specific climate and that climate disappears, then the species will either disappear too or will adapt to the new climate. There is already a new species of bear that has emerged since the decline of your beloved and deadly polar bear. It is a hybrid Polar/ Grizzly bear which is fully capable of reproducing and is booming in population across Alaska and northern Canada, even becoming a pest in some areas already. The cute/man-eating polar bear that you so adore lives on, now stop your whining and get out of the way of progress. Especially huge, awesome, nuclear powered progress. I found those pods to be a bit comical, essentially being nuclear powered trolling motors.

Ethan Brush

The photo of Scandinavia doesn\'t really add much, does it? Sweden isn\'t even completely snowcovered and there is only ice in the extreme North of the gulf of Bothnia. It shows a mild period of winter and the area is not the one discussed in the article.

Stefan Andersson

Superb article. Good learning from it too.


\"burning half a ton of uranium a day\" foathkent, learn to read. The article says half a KILO, which is the short form of KILOGRAM.

The whole anthropogenic global warming/climate change hoax/fraud was revealed more than two years ago with the release of the e-mails, documents, notes and program code from the Climactic Research Unit at the University of East Anglia.

Recently, another large batch of e-mails was released, including even more damning evidence against the hoaxers.

Those guys know the planet has been cooling for over a decade, right in step with the sunspot cycle, just like the AGW skeptics have said all along - the sun is the main driver of Earth\'s climate and there\'s nothing we can do about that.

Gregg Eshelman

I think these Ice Breakers are a bigger threat to global warming than all the cars in thew world. Has anyone ever studied the problem of breaking up all that arctic or antarctic ice? When I put a block of ice in my cooler it last much longer than crushed ice. The same might be true of our earthly blocks.

Layne Nelson

it would seem , if we had mapps of ice thickness, which indeed are more like weather updates, as ice thickness changes with time rapidly----

there would be more value added to any ship with this functionality.

if they get stuck or at least, hit a dead end---where ice thickness precipitously increases, then they just lost a lot of money and time.

to make it feasibly for non-icebreaking ships to travel in thin iced shipping lanes---you need real time maps of ice thickness and ice thickness predictions to map out an ice path.

yes the ship probably can and must use radar to traverse its immidiate path, but no----if a ship is heading for a few weeks in a realtively icey sea----it's not going to assume and hope for the best. it would need relative knowledge of ice thickness.

otheriwse, that would be too big a risk, and it would be the ice free sea as the default choice. and in that case, why bother building the dual functionality into the boat--which is a massive added cost.

so before these boats are built with investor money, you'd probably need a substnatially more accurate ice thickness monitoring and prediction system than what we have now.

most likely---

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