Naval Nuclear Power MM1(SS) Ryan Reed Nuclear Field Coordinator NRD Michigan
POWER GENERATION BREAKDOWN • 55% COAL • 22% NUCLEAR • 10% NATURAL GAS • 9% HYDRO • 3% PETROL. • 1% SOLAR, WIND, BIOMASS, GEOTHERMAL
What is nuclear power? Extracting usable energy from atomic nuclei via controlled nuclear reactions.
History • Fission experimentally achieved by Enrico Fermi in 1934 by bombarding uranium with neutrons. • First nuclear power plant used for civil purpose was launched in 1954 • The Navy’s first nuclear powered ship USS Nautilus was put to sea in 1955
So why would the Navy want to use Nuclear Power? • Efficiency • Zero emissions • Longevity
CONS OF FOSSIL FUEL SOURCES • COAL • NATURAL GAS • OIL
PROS & CONS OF RENEWABLE SOURCES • SOLAR • WIND • BIO-MASS • GEO-THERMAL
Coal vs. Nuclear Power • How long can one pound of coal light one 100 watt light bulb, once all of its energy is converted to electricity? • Approximately 9 hours • How long can one pound of uranium light the same bulb?
Nuclear power plants use a series of physical barriers to make sure radioactive material cannot escape. In today’s water-cooled reactors, the first barrier is the fuel itself: the solid ceramic uranium pellets.
Why do you think the Navy takes advantage of this technology? • Prior to this, submarines relied on diesel generators to charge the ships batteries. This limited the submarine submergence time to a maximum of 12 hours before it would have to resurface and recharge. Today, submarines have the ability to stay submerged and perform several types of missions without being detected for up to 90 days (limited on food and supplies)!!
Longevity • Navy’s nuclear ships can run for decades without refueling. • Allowing our submarines to remain submerged, and aircraft carriers to stay on station without having to return to port to refuel.
Why can an atom produce so much energy? • First, consider the type of reaction that is taking place? • Second, what are the individual particles that make-up the atom? • Which particles are in the nucleus and what electrical charge do they possess? • What holds the nucleus together?
Nuclear Physics“Nuclear Strongforce” • The nucleus always has a smaller total mass than the sum of its component masses. • That is if you weighed the protons and neutrons individually they would weigh a total of 235 atomic mass units. • However, when grouped to form the nucleus some of the mass is converted to energy (nuclear strongforce) holding it together which makes it weigh less. This is derived from: E = mc2
Nuclear Physics“Fission” What causes fission to occur?
Nuclear Physics“Fission” • Addition of a neutron to the nucleus, causes it to become unstable. In order for the nucleus to reach stability again, it fissions (breaks apart) releasing the energy (nuclear strongforce) in the form heat. • Also, 2 to 3 more neutrons are released.
* 235 1 236 134 100 1 1 Xe U U Sr E + n + + n + n + 92 0 92 54 38 0 0 Basic fission reaction
Nuclear Physics“Fission” • Are the neutrons “born” from fission important? • Yes! • They go on to cause more fissions to keep the chain reaction continuing.
Xenon Xenon Xenon Strontium Strontium Strontium Basic Nuclear Reaction (Fission) U 235 U 235 U 235 = Neutron = energy released (heat) = Fission Products
Nuclear Physics • If one neutron produces one fission and three neutrons are “born” and they cause three fissions to occur how many do we having at the beginning of the third generation? • 9 • Fourth and so on? • 27, 81, 243, 729, 2187 • How is the reactor responding to this increase in neutron population per generation? • It is increasing at an exponential rate, resulting in the reactor to operate near or above its designed limits.
Nuclear Physics • To control the neutron population within the reactor, operators use control rods which are made of non-fissionable materials such as Boron or Hafnium. These elements are “neutron sponges” they can absorb neutrons, to prevent them from interacting with Uranium. • The control rods are remotely controlled and can be raised and lowered to control the neutron population within the reactor. • At steady state levels of operation, one neutron causes a fission, an only 1 of 3 born from fission goes onto to cause another fission. This is called “criticality”.
CONTROL ROD THREADED SHAFT FOR DRIVE MOTOR CONTROL RODS ARE MADE OF A MATERIAL WITH A VERY HIGH PROBABILITY OF NEUTRON ABSORPTION, USUALLY BORON OR HAFNIUM. THIS ALLOWS THE CONTROL RODS TO BE RAISED AND LOWERED IN THE REACTOR CORE TO CONTROL THE RATE AT WHICH FISSION OF U-235 OCCURS. THE RODS ARE CONTROLLED AS A GROUP BY MOTORS AND ELECTRONICS FROM A LOCATION AWAY FROM THE REACTOR. CONTROL ROD
TOP VIEW OF REACTOR CORE WITH CONTROL RODS AND FUEL CELLS IN OUT CRDM CONTROL ROD FUEL CELL
The Nuclear Reactor • Made of Corrosion Resistant Stainless Steel • Built to withstand high temperature and pressure • Initial Containment for radioactive material
Steam produced Heat We then convert the heat from the fission reaction to steam in a steam generator. The primary coolant passes through tubes which have cooler secondary coolant sprayed on them. The secondary coolant flashes to high pressure steam.
Steam Generator Turbine The steam then flows down a pipe where it will turn generators to generate electricity and on ships to turbines. The steam will spin the turbines at a high rate of speed. This will be reduced by reduction gears to a useful speed to turn the shaft and ultimately the screw on a ship or submarine to propel the vessel through the water.
Completing the Cycle • The steam, which is now low pressure and exhausted of its’ energy, is condensed back to secondary coolant. • This secondary coolant is pumped back into the steam generator to be used again. • The primary coolant, after transferring its’ energy, is pumped back through the core repeating the cycle.
NUCLEAR REACTOR OPERATION STEAM SECONDARY SHIELD TURBINE SW OUT CONDENSER STEAM GENERATOR REACTOR SW IN PRIMARY SHIELD COOLANT PUMP CONDENSATE PUMP REACTOR COMPARTMENT
Common concerns regarding nuclear energy • Explosions • Meltdowns • Radiation • Toxic Waste • Mutations
TYPES OF RADIATION GAMMA RAYS - no electric charge, most penetrating. ALPHA PARTICLES - identical to a Helium-4 atom, ingestion hazard. BETA PARTICLES - electron with a - or + charge. NEUTRON - no electric charge.
BIOLOGICAL EFFECTS • KILL OR DESTROY CELLS. • GENETIC DEFECTS. • CANCER • NOTHING.
RADIATION LIMITS & EXPOSURE GOVERNMENT NAVY 5,000mrem/yr 500mrem/yr Average exposure working with nuclear power: 150mrem/yr Average exposure received in the United States: 360mrem/yr Medical X-rays: 60mrem/dose Smokers: 1300mrem/yr
HEALTH EFFECTS OF RADIATION EXPOSURE • 0-25 Rem None detectable • 25-100 Rem Minor blood changes, nausea, fatigue • 100-200 Rem Disability, blood changes, vomiting. Several weeks to recover • 200-600 Rem Blood changes, internal hemorrhaging, disability, vomiting. 50% die w/o treatment • 600-1000 Rem Accelerated symptoms. Death may occur w/in 2 weeks, with delayed mortality of 100% w/o medical treatment • 1000-2000 Rem 100% fatality w/o medical treatment • 1 Rem = 1000mRem `
CHERNOBYL: AN ACCIDENT WAITING TO HAPPEN • Boiling Water Reactor • Runaway Reactor => 7% to 50% in 3 sec • Slow Control Rods • Loss of coolant due to operator error • Graphite Moderator vice water • No Containment
RECENT NUCLEAR ACCIDENTS • CHERNOBYL-1986 • TECHNICIANS REMOVE ALL 30 CONTROL RODS, LOSE CONTROL OF ENERGY • ATTEMPT TO SHUT DOWN REACTOR, ONLY INSERT 6 CONTROL RODS • RAPID INCREASE OF HEAT CAUSES COOLANT TO EXPLODE INTO STEAM, RUPTURING REACTOR VESSEL • CONTAIMENT BUILDING RUPTURES RELEASING RADIOACTIVE MATERIAL
RECENT NUCLEAR ACCIDENTS • THREE MILE ISLAND- 1979 • WORKERS DISABLE CONTROL AIR SYSTEM • SECONDARY SYSTEM SHUTS DOWN, LOSS OF WATER IN STEAM GENERATORS • REACTOR SCRAMS, PRIMARY SYSTEM OVERHEATS, RELIEF VALVE GETS STUCK OPEN • LOSS OF COOLANT IN PRIMARY SYSTEM, CORE IS UNCOVERED • FUEL RODS BREAK DOWN RELEASING HYDROGEN INTO REACTOR VESSEL AND BLDG • GASES RELEASED TO ATMOSPHERE TO PREVENT HYDROGEN EXPLOSION
Three Mile Island • Maintenance stopped feedwater to Steam Generators => Rx automatically shutdown • Emergency Core Cooling System malfunction • Leaking pressure relief valve • Partial Meltdown • Almost fully contained • Turned the tide on public sentiment for Nuclear Power