# Nuclear\-Powered Aircraft Carrier Energy Pathway

Follow naval nuclear energy from uranium ore through enrichment, fuel, a pressurized\-water reactor, steam, turbines, gearing and shafts to a carrier under way\.

By happy\-fox\-541b97e8

Topic: Energy

[Open the interactive Jig](https://ask.jig.com/j/vJUfslaYbgnS)

## Transcript

### 1. Nuclear\-Powered Aircraft Carrier Energy Pathway

A Gerald R\. Ford\-class carrier: 333 m overall, about 100,000 long tons full load, sustained speed above 30 kn\. Two Bechtel A1B pressurized\-water reactors supply all propulsion and electrical power through four shafts\. This sequence traces that energy from uranium ore to wake\. Drag empty space to turn the model; pinch or scroll to zoom\.

Dimensions: NAVSEA / Ford\-class fact data\. A1B ratings are not published; the A4W of the Nimitz class is rated 550 MWt per reactor\.

### 2. Ore extraction and milling

Uranium is mined by open pit, underground workings or in\-situ leach, at ore grades down to about 0\.1% U\. Milling crushes and acid\-leaches the ore and precipitates U3O8 concentrate \(yellowcake, above 80% U\), shipped in 200 L drums\. Natural uranium is 0\.711% U\-235; the balance is essentially U\-238\.

Source: World Nuclear Association, Nuclear Fuel Cycle Overview\.

### 3. Conversion and enrichment

Conversion turns U3O8 into UF6, a solid in storage cylinders that sublimes for gas\-phase processing\. Gas centrifuges, rotors 3 to 5 m tall spinning at 50,000 to 70,000 rpm, separate the slightly lighter U\-235 molecules in cascades of stages\. Civil LEU stops at 3 to 5%; US naval fuel is enriched to roughly 93% U\-235\.

Centrifuge figures: WNA, Uranium Enrichment\. Naval assay: Ma and von Hippel, Nonproliferation Review, 2001\. Tails assay is typically 0\.2 to 0\.25%\.

### 4. Naval fuel assembly

Open literature describes highly enriched uranium dispersed in a zirconium alloy matrix and clad in zirconium alloy, with burnable boron poison\. High enrichment and high uranium loading let one core last the planned 50\-year service life of a Ford\-class hull\. The plate assembly shown is representative only: actual naval fuel geometry is classified\.

Nimitz\-class A4W cores required a mid\-life refuelling; Ford\-class A1B cores are designed for life\. Sources: Ma and von Hippel 2001; Arms Control Association 2016\.

### 5. Pressurized\-water reactor

Fission in the core heats primary coolant held near 15 MPa by the pressurizer, so it stays subcooled at roughly 300 to 320 °C\. Reactor coolant pumps drive it through the hot leg to the steam generator and back through the cold leg\. Withdraw the control rods to raise core power and watch the primary loop respond\.

Pressures and temperatures are representative of naval PWR literature; A1B plant data are not public\.

### 6. Steam generation

Primary water passes through the inverted U\-tube bundle and gives up heat across the tube walls; it never leaves the closed primary circuit\. Feedwater on the shell side boils, and separators in the upper dome deliver saturated steam to the main steam line at roughly 4 MPa\. The two loops are physically isolated, so the turbines handle non\-radioactive steam\.

Indicative secondary conditions: about 535 °F \(279 °C\) and 600 psi, from the A1W prototype; carrier values are not published\.

### 7. Turbines and condenser

Steam expands through the main propulsion turbine, turning a bladed rotor at several thousand rpm, then exhausts to a sea\-water cooled condenser\. Condensate returns to the steam generator as feedwater, closing the secondary loop\. Ford also has four steam\-driven main turbine generators, giving about three times the Nimitz electrical capacity for EMALS, AAG and future loads\.

Ford replaced steam catapults with the electromagnetic EMALS launcher and AAG arresting gear\.

### 8. Double\-reduction gearing

Turbine speed is far too high for an efficient propeller\. A double\-reduction gearbox steps it down through two pinion and gear meshes to a bull gear on the line shaft, turning at tens to a little over 100 rpm\. The ratio shown is illustrative; the actual turbine speeds and gear ratios are not published\.

Look at the gear casing for the plant nameplate\.

### 9. Shafting and propeller

The main thrust bearing transfers propeller thrust from the shaft into the hull structure\. The line shaft runs aft through spring bearings and the stern tube to an external strut bearing and a solid nickel\-aluminium bronze propeller of about 30 t\. Each Ford\-class hull has four shafts, two per reactor plant\.

Propeller mass from gCaptain, 2013\. Published diameters vary between 21 ft \(6\.4 m\) and 25 ft \(7\.6 m\)\.

### 10. A carrier under way

Four propellers put roughly 190 MW of shaft power into the water on a Nimitz\-class hull, moving about 100,000 long tons at over 30 kn without refuelling\. Range is limited by aviation fuel, ordnance and stores rather than propulsion\. Raise shaft speed to see the wake build\.

Nimitz shaft power: 260,000 shp \(about 194 MW\) on four shafts\. Ford\-class propulsion ratings are not published\.