Yuku free message boards

StevoJH wrote:

---

Basicly I'm asking if it would be possible to build the carrier with gas turbines now and switch for something new later, the reason i'm asking is that if a ship is designed for a 50 year life you would assume that it is capable of being refit with different engines if fuel became prohibitably expensive. Similar concept to how the CVF is fitted for STOVL but has all the space saved so it can be converted to CATOBAR.

My first thought would be "no," as the fuel for a fossil-fired plant is distributed throughout a ship; the fuel for a nuclear plant is concentrated in the reactor core; there would be severe weight penalties to provide both bunkerage for oil and the structural features needed for a reactor.

I'm also unsure about how much energy it actually takes to produce the fuel needed for a naval reactor, as these need highly enriched fuel in order to have useful lives measured in many years (commercial plants are designed to be refueled frequently; naval plants are designed to avoid refueling as much as possible), and the process of enrichment is quite energy intensive. I don't know how energy intensive; it's possible that the net fossil fuel use in enriching the fuel for a naval reactor exceeds the energy that reactor produces during its lifetime.

To conclude: I suspect that fossil fuel prices would have to go up quite a lot more to make nuclear power economical for most naval ships, even for countries, like France or the UK, which have the infrastructure in place to provide fuel (usually uranium) sufficiently enriched for naval reactors. For those countries without an indigenous nuclear industry, the infrastructure would be very difficult to build, as the facilities to produce the fuel for naval reactors are interchangeable with the facilities to produce the nuclear element of atomic bombs. I suspect that the current signatories of the Non-Proliferation Treaty would look at construction of the required infrastructure with something less than joy, even if that construction is in a country with absolutely no current aggressive tendencies. I don't think the US, for example, would say "go for it!" if Sweden decided to build nuclear submarines or if New Zealand ordered a batch of nuclear-powered cruisers.

Zen9 wrote:

---

(there have been closed cycle gas turbines studied for the USN which were supposedly more compact than the present PWR's),

Gas cooled reactors?

Oh my!

Well, they were design studies, so the authors' conclusions were heavily dependent on the initial assumptions. My suspicion is that a gas-cooled reactor is bulkier, because water is a very good heat transfer fluid (not as good as liquid metals, but much easier to handle), with the putative savings being from the elimination of the steam generating heat exchangers and more compact turbomachinery.