ME-Nuclear/GT

PWR

Pressurized Water Reactor

Nuclear Propulsion

U.S. Submarines, Aircraft Carriers

Russian Submarines, Aircraft Carriers, Icebreakers, few commercial

Nuclear Pros

1. High energy density

2. “clean” — no exhaust

3. No refueling on regular basis

4. No air required to produce power

5. Less Space when considering fuel tanks

Nuclear Cons

1. High Cost in building and more in safety training

2. Radiation

3. Disposal of Spent Fuel

4. Not Welcome in Ports

Pressurized Water Reactor Components

Primary and Secondary Coolant Loops

Primary Coolant Loop

Water is used to cool the reactor, it goes through pressurizer and then to steam generator where it heats the secondary coolant in steam generator. Water remains liquid in primary loop because of the high pressure

Temp and Pressure of Primary Coolant

1800-2000 psi, 550F

Secondary Coolant Loop

Essentially steam plant that uses boiler without a superheater.

Nuclear Fuel

Uranium 235 enriched to about 20%, normally found at 0.7%; Uranium Dioxide Pellet; melts at 4500F

Nuclear Reaction

Low Speed Neutron (Thermal) →U235 splits (E=mc²; mass to energy as heat)→ releases fast (prompt) neutrons→ slow fast ones with moderator (water) == Self Sustaining Reaction

Water in PWR

Both coolant and moderator; when reactor gets too hot, water becomes steam and then there is less moderating so reaction fizzles out; has negative temperature coefficient

Reactor Control Mechanism

1. At steady State Heat Release

2. Steam Demand in Secondary Loop Drops

3. Primary Coolant Temp Rises

4. Density Drops

5. Reduces Moderating Effect

6. Reaction Slows Down

7. Remain in Equilibrium

Fuel Tubes

Zircaloy Tube → Zirconium; melting temp is 800F; permeable to radiation; maximum temp inside tubes is 600F to prevent melting

Control Rods

Raised and Lowered into grid of fuel rods, made of boron which absorbs neutrons, used to slow or stop reaction; scram

Reactor Vessel

Outside Lead shielding; housed in containment building to prevent explosion

Input and Outlet Nozzles

Spread around circumference of reactor vessel, 2 outlet. 4 inlet

Steam Generator

Generates Saturated Steam from the secondary coolant using the heat from the primary coolant, primary coolant enters at 550F and leaves at 500F. Different coolants do not interface

Tube Bundle

Group of U shaped tubes in steam generator that heat the secondary coolant. Maintain high pressure

Pressurizer

Maintains primary coolant pressure, T’ed into high pressure line. Changes the pressure of steam in the top in order change water pressure. Has pressure relief valve

Spray Line Nozzle

Sprays cold water into pressurizer to condense vapor and lower pressure in system

Heater Bundles

Raises Temperature in pressurizer which raises the pressure of the system

Future of Nuclear

Generation 4, SMR

SMR

Small Modular Reactors, factory build, tested to standard approved design =, whipped to site and assembles (50-100 MW)

MSR

Molten Salt Reactor, type of SMR with fluidized bed of molten salt and uranium fuel, mix of moderator and fuel. At atmospheric pressure. If accident fluid drains out of reactor and solidifies to prevent thermal runaway.

MSR vs PWR

MSR runs at higher temp —880C = 1600F which allows for superheating so its more efficient

NS Savannah

Nuclear ship owed by MARAD, ½ Cargo, ½ Passenger

Power Turbine

LP Turbine which provides output, only on ships, also called load turbine

How are GT Maintained

Taken out of ship through intake duct and maintenance done onshore, there are tracks in the exhaust duct to aid with removal

Soft Patch

Covering on intake duct after filters that can be removed when GT is being taken out and installed

Regenerator

Heats compressed air which lowers the fuel needed for a given load in a GT

Intercooler

Lowers temperature of outlet air from HPC, which allows for more heat to ab absorbed in regenerator and increases efficiency

Simple Cycle GT

Normal GT cycle without any increased efficiency

Regenerative-Cycle GT

GT with Regenerator to increase efficiency

Intercooled, Regenerative-Cycle GT

GT with intercooler and regenerator

Combined Gas and Steam Turbine

Simple GT Cycle which uses the exhaust gas to heat a boiler. Dual systems, more efficient

COGSAT Pros

Very efficient = 50% which is better than LSDE

COGAST Cons

Expensive, Heavy, Hard to maintain

Triple Shaft Turbine

2 concentric shafts for different speed compressors along with shaft for power turbine

Enclosure

Sound proof and insulated for safety. Prevents tampering

Debris Testing

Throw different size dead chickens into GT to see what size bird breaks the system.

Starter Motor

Runs up to 40% of full RMP, Hydraulic

Gear Box

Increases the speed on the starter motor and creates hydraulic pressure for auxiliaries during engine operation

Exhaust Gas Temp

1100 F

Heavy Duty Gas Turbines

Can use lower quality fuel, run only at constant speed, Not used in marine applications

Aero Derivative Gas Turbines

Light weight, high power, variable speed, little maintenance on ship, unit taken replaced and overhauled on shore

ADGT Pros

• High Power Density, low Specific Weight

• Rapid Start & Assumption of Load

• Low Emissions

• High Quality Exhaust Gas

ADGT Cons

• Sensitive to fuel quality

• high fuel consumption

• High air and exhaust flows

• reduced Performance at high

  temps

• High Maintenance Cost

• High Thermal Profile

Pressure Ratio

Change in pressure from intake to compressor discharge

Turbine Temps and Pressures

260psi =18 atm,1250C in combustion section; 90psi= 6atm, 850C after HP turbine (compressor); 1atm, 550C=1100F after LP turbine

Gas Generator

Compressor + High Pressure (compressor) turbine

Turbine Cooling

Air Cooled

COGAG

Combined Gas Turbine and Gas Turbine, identical set of GT used for high speed

COGOG

Combined Gas Turbine or Gas Turbine, low power GT for cruising and high power GT for high speed

CODOG

Combined Diesel and Gas Turbine, diesel for cruising, GT for high speed

Prop for GT

Controllable Pitch Propeller

Flux

Number of Neutrons in Circulation

Channels

Spaces between Fuel Rods