Nuclear Efficiency and The Wins In Front of Our Faces

September 08, 2018

Big Ships

A couple of weeks ago, I was headed over the Chesapeake Bay Bridge to Delaware with a large container ship about to head out under the bridge to the ocean. It was a medium-sized ship with very recognizable script, so me being me, I looked it up. It looked like this:


Here’s what I found - it’s a 150m long vessel that carries cars all over the world, and Hoegh has over 50 of them this size or larger. Altogether, the fleet carries over 2 million cars per year and won “Best Shipping Line of the Year” in 2018.

Finding any details about the engine in this behemoth was a little tougher, but I think it’s something like a Mitsubishi 8UEC60LS 8-cylinder diesel making almost 20,000 hp driving a single prop shaft. These are enormous engines, usually a couple of stories tall and the size of a small house. Near as I can tell, this fact sheet from Mitsubishi Heavy Industries describes pretty closely the engine that was in the Hoegh ship in the Bay. Specific fuel oil consumption - SFOC - is measured in grams per Kilowatt-Hour. Kilowatts are a unit of (electrical) power, somewhat equivalent to horsepower, so the measurement describes how many grams (mass of fuel) it takes to run a ship at a certain power for one hour.

That answer for the case of our Hoegh autoliner, assuming 85% load is 157 g/kWh, which seems to mean about 2.5 metric tons of diesel fuel per hour.

Tons. Per Hour. And Hoegh has 50 ships this size or larger. And there’s plenty more shipping lines too.

I’m not positive I’m doing the calculations or the research correctly, but I think I’m close. Instructables says that the largest ship in the world, the Emma Maersk, burns around 20 tons of diesel per hour, which makes this sound about right. There’s also some good descriptions from experts on Quora that get more into the details, and a very comprehensive article on different tanker types from an Arctic Climate group.

What’s The Point?

Ok, why are we doing all these diesel calculations? Well, according to this article, there’s something like 90,000 cargo ships plying the world’s oceans, moving something like 90% of all the world’s goods. And on certain pollution metrics, like Sulphur Oxides, just one massive container ship is equivalent in output to about 50 million cars.

In terms of total pollution output, it’s not huge for CO2, but it is a massive portion of sulfur, nitrogen, and other particulates.

There’s more focus on shipping, fuel usage, and the environment today than in the past, but most of the conversation is focused on cleaner fuels (shipping fuel today is literally the worst fossil fuel there is) or on more efficient engines. The unregulated industry may even be regulated sometime soon. But there’s another obvious remedy, pioneered and demonstrated by the Navies of the world, that literally removes the entire problem.


Submarines, aircraft carriers, and lots of other large military ships have been powered by small reactors for decades. They produce a huge amount of energy in a very small footprint and eliminate the need for refueling, which would be both expensive and dangerous in war zones.

Safety is the biggest concern with nuclear power, but it’s something that most of the public doesn’t understand very well. They just know names like Fukushima, Chernobyl, and 3 Mile Island. But the US Navy track record is basically flawless.

Nuclear proliferation is the second big concern, and it’s true that early PWR reactors used highly enriched U-235. More recently, reactor designs have allowed for low-enriched uranium fuel that can’t be converted into anything weapons-grade. Brazil, a non-nuclear country, is working on a nuclear submarine while still adhering to it’s placement with the Non-Proliferation Treaty.

Moving towards safe, low-enrichment PWR nuclear reactors for the world’s container ship fleets would make an absolutely massive dent in both emissions and fossil fuel usage. Shipping uses something like 7.5mm barrels of oil a day today.

Right In Front of Us

This solution is right in front of our faces. The Navy realized it decades ago. They invested in safe reactor design and knowledgable crew and staff to drive them. It’s paid off.

We need to be able to get past the thin veneer of fear, confirmation bias, politics, and related problems to be able to evaluate the available set of options to our problems. Nuclear container ships with uranium fuel that cannot be harnessed for weapons is simply good for the world. While there are no doubt still technical challenges with this future, they are not the roadblock. The roadblocks are all politics and perception.

Which makes me wonder how many other easy wins for the world are just outside the range of our voluntary blinders. You may have heard of Bjorn Lomborg - he’s the skeptical environmentalist that so many people loved to hate. When I listed to his TED talk a few years back, the thing that struck was his ability to find ways to measure problems against each other. There’s no question in my mind that the problems of malaria and malnutrition in today’s poor far outweighs the problem of climate change. The impacts are far more direct in terms of human lives.

The same is true with nuclear ships for climate change. We focus on car efficiency, electricity and better mileage standards. But we’re still missing entire variables in our equations.

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