Nuclear Fission: Principle Of Nuclear Reactor

nciple of Nuclear Reac

NUCLEAR FISSION

Fission Process U+n

235

U*

236

(A1,Z1) + (A2,Z2) + Nn + Υ

• Z1 + Z2 = 92, A1 + A2 + N = 236 • A1 = A2, symmetric fission rare (~0.01%) • Capture of neutron by 235U forms compound nucleus • ~2.4 prompt neutrons released per fission event • Delayed neutrons account for ~0.65% of fission neutrons • Probability of fission occuring is dependant upon the crosssection for that reaction

The Nuclear Reactor

 To build a nuclear reactor, what you need is some mildly enriched uranium. Typically, the uranium is formed into pellets . The pellets are arranged into long rods, and the rods are collected together into bundles. The bundles are then typically submerged in water inside a pressure vessel. The water acts as a coolant. In order for the reactor to work, the bundle, submerged in water, must be slightly supercritical. That means that, left to its own devices, the uranium would eventually overheat and melt.  To prevent this, control rods made of a material that absorbs neutrons are inserted into the bundle using a mechanism that can raise or lower the control rods. Raising and lowering the control rods allow operators to control the rate of the nuclear reaction. When an operator wants the uranium core to produce more heat, the rods are raised out of the uranium bundle. To create less heat, the rods are lowered into the uranium bundle. The rods can also be lowered completely into the uranium bundle to shut the reactor down in the case of an accident or to change the fuel.

The Lead-Cooled Fast Reactor (LFR)

 The Lead-Cooled Fast Reactor (LFR) system features a fast-spectrum lead or lead/bismuth eutectic liquid metalcooled reactor and a closed fuel cycle for efficient conversion of fertile uranium and management of actinides.

Fuel : Metal or nitride based uranium and transuranics.

Coolant Temperature :

The Molten Salt Reactor (MSR)

FUEL: the fuel is a circulating liquid mixture of sodium, zirconium,and uranium fluorides.

POWER EFFECIENCY : 1,000 MWe.

 SYSTEM TEMP. : 700 degrees Celsius 800 degrees Celsius

The SupercriticalWater-Cooled Reactor (SCWR)

 The supercritical water coolant enables a thermal efficiency about one-third higher than current light-water reactors, as well as simplification in the balance of plant. FUEL: The fuel is uranium oxide. POWER EFFECIENCY :

1,700 MWe

SYSTEM TEMP.: 510 degrees Celsius to 550 degrees Celsius.

The Sodium-Cooled Fast Reactor (SFR)

 The SFR's fast spectrum makes it possible to use available fissile and fertile materials (including depleted uranium) considerably more efficiently than thermal spectrum reactors with once-through fuel cycles.

FUEL : uranium-plutonium-minor-actinide-zirconium metal alloy fuel

POWER EFFICIENCY : a)Intermediate Size – 150 to 600 Mwe b)Large Size - 500 to 1,500 MWe SYSTEM TEMP.: The outlet temperature is approximately 550 degrees Celsius for both.

Advantages Of Nuclear energy over other forms Economical aspect Environmental friendly Nuclear Energy – The Future…

Economics 

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~90% capacity Reliable and available Fuel cost relatively low Decreasing capital investment with NGR Social, health, and environmental costs are lower 1Kg U yields ~20 000 times more energy than same amount of coal

Average Capacity Factor by Energy Source, 2002

Environmental Friendly

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Reduced SO2 and CO2 emissions Solidified high-level waste is geologically disposed

THE FUTURE    

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440 reactors currently operating worldwide 30 being built and 33 in planning Another 69 are being proposed Generation lV reactor designs are being developed U.S. investing $410 million into research Enrollment in nuclear engineering is up

Conclusions 

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Solution to energy crisis… more construction on the way. Better for the environment, more economical, and more abundant than other energy sources. Less dependance on foreign oil. Nuclear power can prove disastrous … but mankind has to work on its positive aspect and our earth can become a heaven to live in.