Nuclear Power Plant Operation Lecture PDF

How to Operate NPPs  Conversion of Nuclear Energy to Electricity Pressurizer Steam Steam Generator Fuel Assembly Reactor...

How to Operate NPPs  Conversion of Nuclear Energy to Electricity Pressurizer Steam Steam Generator Fuel Assembly Reactor Feed water Turbine Generator Fuel Pellet Sea Cooling Water Reactor Coolant Pump Condenser Fuel Pellet → Fuel Rod (16X16) → Fuel Assembly (177) Feedwater Pump * KSNP : Korea Standard Nuclear Power Plant APR-1400 Fuel Assembly (241) 1 How to Operate NPPs : A lot of Systems Nuclear Power Plant  Advantage  No Greenhouse Gas, No Pollutants  High energy density of fuel  1g of U-235 = 3 tons of coal  Years of supply of fuel at site => stable energy source  Economical  Technology Intensive  Promote development of science and technology  Related industry development  Heavy equipment, Plant Engineering, Construction, Nuclear Fuel, NDE, Operating and Maintenance, I&C, others…  Disadvantage  Huge capital investment  ~3-5 billion $ per 1,000MWe plant  Long construction time (4-6 years)  Radioactive Waste & Spent Fuel  Public’s perception 3 Nuclear Fuel 4 Pressurized Water Reactor (PWR) Pressurized Water Reactor (276 operating, as of 2015 JAN) *Data source: IAEA/PRIS web site as of 2015 Jan (http://www.iaea.org/PRIS/WorldStatistics/OperationalReactorsByType.aspx) 5 Boiling Water Reactor (BWR) (80 operating, as of 2015 JAN) *Data source: IAEA/PRIS web site as of 2015 Jan (http://www.iaea.org/PRIS/WorldStatistics/OperationalReactorsByType.aspx) 6 Pressurized Heavy Water Reactor (PHWR) Pressurized Heavy Water Reactor (49 operating, as of 2015 JAN) *Data source: IAEA/PRIS web site as of 2015 Jan (http://www.iaea.org/PRIS/WorldStatistics/OperationalReactorsByType.aspx) 7  Nuclear Fission  Nuclear Fission: Generation of energy by breaking large atoms (usually Uranium) into smaller atoms.  Nuclear Fusion: Energy is produced by “fusing” light nuclei into heavier ones!  Note the increase in binding energy per nucleon. Fission products (1)  The fission products (PFs) shown are just examples, there are a lot of different possibilities with varying probabilities  “Double-hump” curve  Consider FPs from 100 fissions  Asymmetric splitting, more probable  Most probable, FPs with A~94 & 140 e.g., Fission products (2)  FPs are neutron-rich, hence, highly unstable against Beta decay  Radioactivity of FPs is problematic!  Radiation protection (irradiated fuel)  Residual heat after reactor shutdown (Residual Heat Removal System RHRS)  For a power reactor, accumulation of FPs influences neutron balance  Special case: 135Xe has a huge neutron absorption probability (135Xe poisoning!)  Other FPs are less important (for thermal reactors) Continuous Power Generation  Chain Reaction 11 Linear Chain Reaction  Obviously, an expanding chain reaction cannot be sustained for long (bomb). For controlled nuclear power, once we reach our desired power level we want each fission to produce exactly one additional fission A Single Slow Neutron!  Slow (thermal) neutrons are more effective at inducing fission, but, fissions produce fast moving neutrons. We need to slow them down.  Fissions typically produce several neutrons but a linear chain reaction only needs one. We need to get rid of a good fraction of our neutrons. Moderator  Neutrons are slowed down by having them collide with light atoms.  Highest level of energy transfer occurs when the masses of the colliding particles are equal (ex: neutron wikipedia.org and hydrogen) Control Rods  Control rods are made of a material that absorbs excess neutrons (usually Boron or Cadmium).  By controlling the number of neutrons, we can control the rate of fissions Enrichment  To be used in PWRs, fuel must be 3-5% 235U. Note!  The Uranium is both the fuel and the source of neutrons.  The neutrons induce the fissions  The water acts as both the moderator and a heat transfer medium.  Control rods regulate the energy output by absorbing excess neutrons  A nuclear bomb requires nearly 100% pure 235U or 239Pu. The 3% found in reactor grade Uranium CANNOT create a nuclear explosion! World Distribution of Uranium Gen-IV Reactors  Gen-IV Reactors  Better, safer, more economic nuclear power plant  safety & reliability  proliferation resistance & physical protection  economic competitiveness  sustainability U.S.A. United SwitzerlandSouth Korea South Africa Japan France Canada Brazil Argentina European Kingdom Union 20 Gen-IV Reactors 21 Nuclear Power Plants in Korea *Data source: World Nuclear Association, JAN, 2015