1. LOW PRESSURE REACTORS

2. Muhammad Umair Bukhari Engr.umair.bukhari@gmail.com www.bzuiam.webs.com 03136050151

3. OVERVIEW I’ll discuss here: What is nuclear energy? Nuclear reactor Nuclear power plant Types of nuclear reactors and Nuclear reactor hazards

4. What is nuclear energy? Nuclear energy produces electricity from heat through a process called fission. Nuclear power plants use the heat produced by fission of certain atoms. 1. Nuclear fission nucleus of atom is split into parts, produces free neutrons and energy

5. Nuclear Reactors Nuclear Reactor Nuclear Reactor  device built to sustain a controlled nuclear fission chain reaction www.pbase.com/pbrakke/image/44279993 http://en.wikipedia.org/wiki/Image:Crocus-p1020491.jpg Main Components of Nuclear Reactor: - reactor vessel - tubes of uranium - control rods - containment structure control rods control radioactivity, absorbs neutrons Containment structure contains the reaction in at least 3 feet of concrete!

6. The Nuclear Power Plant Fission occurs in the reactor vessel. Heat is produced. The heat is used to heat water to create steam The steam is used to turn the turbine in the generator to produce electricity The steam is cooled in the condenser to return to the liquid phase. Nuclear power plant Nuclear power plant consists of all the parts needed to create electricity by using nuclear energy

7. Types of Nuclear Reactors: Thermal Reactors and Fast Reactors Homogeneous and Heterogeneous Reactors Low Pressure and High Pressure and Reactors Low Pressure Reactors: Pressure is normally 7MPa Water boils in the core of the reactor Low pressure reactors are working in a “DIRECT CYCLE” Most common low pressure reactors are : Boiling Water Reactors BWR Advanced BWR, ABWR Economical Small Boiling Water Reactor (ESBWR) RBMK Reactor

8. Boiling Water Reactors BWR: Direct Boiling 10% Coolant = Steam 3.2% U-235 Fuel Lower Power Density than PWR Corrosion Product Activated in Core Higher Radiation Field UO 2 Fuel 60 – yr Service Life Internalized Safety and Recirculation Systems

9. http://www.nrc.gov/

10. 1350 MWe 77% more compact than BWR design 39 month construction period TOSHIBA, Kashiwazaki-Kariwa Unit 6, Japan GE

12. Early 1990s - TEPCO, 5 other utilities, GE, Hitachi and Toshiba began development 1700 MWe Goals 30% capital cost reduction Reduced construction time 20% power generation cost reduction Increased safety Increased flexibility for future fuel cycles Commercialize – latter 2010s

13. 1550 MWe (4500 MWt) Passive Condenser Systems for Heat Transfer Standard Seismic Design Improved Economics Shorter Construction Time Reduced Plant Staff and Operator Requirements

14. RBMK Reactor High Power Channel-type Reactor Graphite-moderated 1986 Chernobyl disaster Reactor pit is made of reinforced concrete Pit Dimensions 21.6×21.6×25.5 meters Vessel of the reactor, made of a cylindrical wall and top and bottom metal plates Moderator blocks are made of nuclear graphite of dimensions 250×250×500 mm There are holes with 11.4 cm (4.5 in) diameter Cylindrical core 14 m (45 ft 11 in) in diameter and 8 m (26 ft 3 in) high Maximum allowed temperature of the graphite is less or equal to 730 °C (1,350 °F) Top of the reactor is covered by the upper biological shield, called "Schema E" Fuel channels consist of welded zircaloy pressure tubes 8 cm (3.1 in) in inner diameter with 4 mm (0.16 in) thick walls There are 1661 fuel channels and 211 control rod channels in the reactor core UO 2 pellets 1.15 cm (0.45 in) in diameter and 15 mm (0.59 in) long Emergency Core Cooling System (ECCS)

16. Nuclear Reactor Hazards Radiation effects to the workers of plant Radiation effects on environment and atmosphere Power plant is a major threat for public in case of a disaster like Chernobyl Ageing process of nuclear reactors produces: Small leakages Cracks Short-circuits due to cable failure Gradual weakening of materials Embrittlement of the reactor pressure vessel There is also a threat of terrorism attack That attack may be from air, water or firing on plant from a distance Spent fuel pool disaster Radioactive waste storage disaster Two major nuclear reactor disasters are Three miles island and Chernoby l