Answer to Question #5383 Submitted to "Ask the Experts"

What are the advantages of nuclear-powered submarines over conventional submarines?

Having spent several years on a nuclear submarine, I can tell you that they have several advantages and a few disadvantages when compared to diesel submarines; some of these you can read about in the navy recruiter's literature, and some they probably won't go into much.
The single biggest advantage is that nuclear subs are truly independent of the surface for as long as their food (and the sanity of the crew) holds out. We made our own water and oxygen, we didn't have to come to the surface to run a diesel, our batteries could be recharged even while deeply submerged, and we were actually faster when submerged than on the surface. The nuclear reactor provided all the energy we needed and let us operate up to (in my case) 10 weeks continuously submerged. This was a huge tactical advantage.

The nuclear reactor also let us operate at high speeds for long periods of time. We could cross the Pacific at a higher rate of speed than any conventionally powered ship because we didn't have to slow down every so often to take on new fuel. So, for example, we made it from San Diego to the Kamchatka Peninsula in 10 days, compared to over two weeks for a conventionally powered surface ship. A diesel submarine would probably not have made the trip because they may not have had enough fuel to go over and back, while remaining on station long enough to do any good.

Which brings us to a third thing—endurance on station. We could spend as much time on station (in our designated operating area) as necessary because, again, we were not tied to a fuel supply. So, as long as the food held out, we could stay happily snapping photos of Soviet ships. This is why, for example, a missile submarine can stay out for three straight months.

Finally, we had a lot more room, and our living conditions were much nicer than a diesel boat. Our battery was much smaller, our diesels were much smaller, and the amount of fuel oil we carried was much smaller than a conventional sub, giving us a lot more room inside for weapons, electronics, and the crew. We did not live in the lap of luxury, but it was a lot nicer than on a diesel sub—and we could shower every two to three days, instead of every one to two weeks. Plus do laundry every week or so! Not the Ritz, but not bad.

The main disadvantage is that a nuclear power plant is noisier than a sub running on batteries. Our pumps were noisy, we had steam noise, and our electric plant put out a 60-cycle "hum," all of which could be picked up by a good sonar system. We were quiet, but even the quietest nuclear sub makes more noise than a conventional boat running on batteries. Luckily, most navies don't have very good sonar, so we were able to spend a total of eight months near the Soviet Union without being heard—as did most other fast attack subs in the US Navy.

The other disadvantages are fairly obvious—nuclear subs are larger, more expensive, and more complicated than diesel boats. However, the advantages far outweighed the disadvantages for the US Navy.

Lastly, believe it or not, our radiation dose dropped when we went to sea, in spite of the reactor being run at sea and shut down in port. It turns out that the nuclear reactor gave us less radiation exposure than natural background, so when we were at sea the drop in background (we were surrounded by water, which is a good radiation shield) more than offset the radiation from our reactor.

Andrew Karam, CHP, PhD