NUCLEAR REACTORS G. HETSRONI Emeritus Danciger Professor of Engineering Technion – Haifa – Israel

Contents 1. History 2. Fission 3. Nuclear reactor basics 4. Classifications 5. Current technologies

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אויר ארובה גזי שריפה קיטור מים גנראטור דוד פחם טורבינה חשמל מעבה קיטור מוחלש

Enrico Fermi

NUCLEAR CHAIN REACTION

Nuclear reactor principle

As of 2005, nuclear power provided 6.3% of the world's energy and 15% of the world's electricity. As of 2007, there are 439 nuclear power reactors in operation in the world, operating in 31 countries. In 2007, nuclear´s share of global electricity generation dropped to 14%, because of earthquake in western Japan on 16 July The United States produces the most nuclear energy, with nuclear power providing 19% of the electricity it consumes, while France produces the highest percentage of its electrical energy from nuclear reactors— 78% as of In the European Union as a whole, nuclear energy provides 30% of the electricity.

Boiling water reactor (BWR) is the simplest of all facilities. Water absorbs heat from the reactions in the core and is directly driven to the turbines. After condensing the water is pumped back to the reactor core. CLASSIFICATIONS BY TYPE

Pressurized water reactor (PWR) uses a sealed system to prevent water circulating through the core from boiling due to high pressure. The heat from this system is removed by the water in pipes to the steam generator. CLASSIFICATIONS BY TYPE

Gas cooled reactor (GCR) uses CO 2 gas to remove heat from the core. This is then piped through the steam generator where heat is removed from the gas and it can then be recirculated to the reactor. As usual steam generated is used to drive the turbine and generate electricity, condensed then recirculated. Graphite is used as a moderator to allow energy production by un-enriched uranium. CLASSIFICATIONS BY TYPE

BASIC PWR - STEAM CYCLE I. Primary circuit A. Reactor II. Secondary circuit B. Steam generator III. Tertiary circuit C. Turbine D. Condenser

PWR in Operation A Primary circuit B. Secondary circuit C. Tertiary circuit 1. Reactor 2. Fuel assemblies 3. Control rods 4. Pressurizer 5. Steam generator 6. Primary pump 7. Feedwater primary circuit 8. Feedwater secondary circuit 9. Steam secondary circuit 10. High pressure turbine 11. Low pressure turbine 12. Condenser 13. Feedwater pump 14. Generator 15. Exciter 16. Transformer 17. High voltage line 18. River 19. Intake cooling water 20. Cold cooling water 21. Warm cooling water 22. Cooling water 23. Upward airflow 24. Steam 25. Outlet cooling water

Diagram of the reactor

REACTOR COOLANT SYSTEM PHYSICAL ARRANGEMENT The PWR reactor coolant system (RCS) circulates water in a closed cycle, removing heat from the reactor core and internals and transferring it to a secondary (steam generating) system. The steam generators provide the interface between the reactor coolant (primary) system and the main steam (secondary) system. The steam generators are vertical U-tube heat exchangers with an integral economizer in with heat is transferred from the reactor coolant to the main steam system. Reactor coolant is prevented from mixing with the secondary steam by the steam generator tubes and the steam generator tube sheet, making the RCS a closed system thus forming a barrier to the release of radioactive materials from the core of the reactor to the containment building.

Reactor Vessel Assembly Arrangement

Fuel assembly

STEAM GENERATOR Nuclear Steam Supply System (NSSS) of KNSP uses two steam generators for transfer of heat from the RCS to the main steam system, One steam generator is located in each loop. PWR, inverted U-tube steam generator with an integral economizer which operates with the reactor coolant on the tube side and secondary coolant on the shell side.

HEAT EXCHANGER This is a heat exchanger in which two water circuits meet each other: hot water under extremely high pressure in the primary circuit leaves the reactor and flows through thousands of U-shaped heat conducting tubes.

STEAM TURBINE Steam turbine consists of a series of blades mounted on a shaft. As the steam jet is inflected, it puts pressure on these blades, making the shaft rotate.

Generator

Condenser and cooling towers

CLASSIFICATIONS BY TYPE

CANDU at Qinshan Electricity Nuclear power plants