The Army’s Nuclear Ship

Wired has a piece on the almost billion dollar cost of a mid life overhaul of a Nimitz class carrier. It’s pretty interesting. Not only does it involve refueling the ship’s two nuclear reactors, but the RCOH pretty much rebuilds everything from the bulkheads in. Think of all the plumbing and wiring in a ship  designed to last 50 years. The RCOH is the one big opportunity to rebuild a lot of that stuff.

Now, you say, XBrad, that’s nice and all, but what does it have to do with the title of this post? Well, bear with me a bit.

The dawning of the age of nuclear power, as exemplified by the sailing of the USS Nautilus led to something of a frenzy in terms of nuclear power.

For a while, it seemed that in the very near future, everything would be nuclear powered. Heck, the Air Force was researching using nuclear reactors to power bomber aircraft, and actually flew a working reactor aboard a B-36.

The Army, which has always had a strong interest in prime power generation, saw nuclear power as an answer to the challenge of providing prime power in remote locations with little or no infrastructure, especially those that would be difficult to supply. And so it began research and experimentation with very small reactors. Most Army reactors were very compact, and designed to use Highly Enriched Uranium. All of the reactors under the Army Nuclear Power Program (ANPP) were one of a kind prototypes. Powerplants were used in Greenland, Wyoming, Alaska and even Antarctica.

As the wiki entry notes, a lot of the ANPP actually seemed more a solution in search of a problem. But there was one plant that actually helped solve a vexing problem.

The only ANPP plant that didn’t use HEU was the topic at hand. The Army often operates close to shores and ports, for obvious logistical reasons. And again, the need for prime power is often on the mind of the logistician. And so, someone had the idea that the Army could utilize a barge mounted reactor, not for propulsion, but for electricity and fresh water generation.

Rather than building a barge from scratch, the Army took possession of a surplus Liberty ship, and removed the steam boiler and engine, and build in its place, via its contractor Martin Marrietta, a 10 Mv Pressurized Water Reactor with Low Enriched Uranium and associated turbines and distillation machinery. The contract was signed in 1961, construction began in 1963, and by early 1967, the vessel, known as Sturgis (MH-1A) went critical while moored near Ft. Belvoir, Virginia.

File:MH1Anuclearpowerplant.JPG

While the Sturgis was being built and tested, an actual use for it was found, one that was, in fact, somewhat urgent.

The Panama Canal, was, of course, of strategic interest to the US, and at that time under the administration of the US. The locks of the canal are operated by gravity fed water from Lake Gatun, the body of water in the center of the isthmus when the canal was built. It’s normally replenished by the torrential rains there. Fresh water from the lake fills the locks to lift ships, and then is allowed to flow out into the ocean when the locks are lowered.

Electrical power for the Canal Zone was also powered by water from Lake Gatun, via a hydroelectric station.  The combined outflow of water via the locks and the hydro power station meant that during the dry season, the water level in Lake Gatun would fall to unacceptable levels. Power was required just to operate the Canal Zone, and the locks. That meant ship traffic through the canal itself had to be restricted. But if power could be provided without having to use the hydro plant, obviously that water would be available for the locks, increasing throughput of the canal.

And so, after a few months of testing and training at Ft. Belvoir, Sturgis was towed to Panama, and from 1968 to 1975 provided its power to the Canal Zone. It’s estimated that the water savings provided by Sturgis allowed an additional 2500 ship transits per year.

By the mid 1970s, conventional powerplants were built along the eastern and western termini of the canal, and Sturgis’ power was surplus to needs. Furthermore, since she had a one of a kind plant, parts and training were uneconomical. She was returned to the US, defueled, and put into storage in the James River fleet, where today she awaits decommissioning** and disassembly.

 

*Highly Enriched Uranium is, of course, more “power dense” than Low Enriched Uranium, but it still below weapons grade enriched uranium.

**Decommissioning in this case has a somewhat different meaning than for a warship of the US Navy.

3 thoughts on “The Army’s Nuclear Ship”

  1. Ironic, innit? The Liberty ships were built with a reciprocating steam plant, for simplicity of construction and maintenance. That technology was a throwback to the last century. That one of them would be home to a nuclear reactor is pretty incredible. Like putting a turbojet on a Sopwith Camel.

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