Nuclear reactor

Contents
 Introduction
 Definition
 History
 Nuclear Fission
 Components of Nuclear Reactor
 Working of Nuclear Reactor
 Refrences

Introduction
 A Nuclear reactor is a device for producing controlled
release of nuclear energy. Reactors can be used for
research or for power production. A research reactor
is designed to produce various beams of radiation for
experimental application; the heat produced is a
waste product and is dissipated as efficiently as
possible. In a power reactor the heat produced is of
primary importance for use in driving conventional
heat engines; the beams of radiation are controlled
by shielding.

Definition
 A nuclear reactor is device designed to
maintain a chain reaction producing a steady
flow of neutrons generated by the fission of
heavy nuclei. Nuclear Reactors are,
however, differentiated either by their
purpose or by their design features. In terms
of purpose, they are either research reactors
or power reactors.

Early Reactors / History
 The neutron was discovered in 1932. The
concept of a nuclear chain reaction brought
about by nuclear reactions mediated by
neutrons was first realized shortly thereafter,
by Hungarian scientist Leó Szilárd, in 1933.
He filed a patent for his idea of a simple
nuclear reactor .

 Szilárd's idea did not incorporate the idea of
nuclear fission as a neutron source, since
that process was not yet discovered.
Szilárd's ideas for nuclear reactors using
neutron-mediated nuclear chain reactions in
light elements proved unworkable.

 Inspiration for a new type of reactor using
uranium came from the discovery by Lisa
Meitner,Fritz Strassmann and Otto Hahn in
1938 that bombardment of uranium with
neutrons, produced a barium residue, which
they reasoned was created by the fission of
the uranium nuclei.

 Subsequent studies in early 1939 revealed
that several neutrons were also released
during the fission making available the
opportunity for the nuclear chain reaction that
Szilárd had envisioned previously.

 In 1939 Albert Einstein signed a letter to
President Franklin suggesting that the
discovery of uranium's fission could lead to
the development of "extremely powerful
bombs of a new type", giving impetus to the
study of reactors and fission.
 World War II
The first artificial nuclear reactor was
constructed at the University of Chicago, in
late 1942.

 Soon after U.S. military developed a number
of nuclear reactors in 1943. The primary
purpose for the largest reactors was the
mass production of plutonium for nuclear
weapons.
 "World's first nuclear power plant“ was
carried out & operated by the U.S. Atomic
Energy Commission in 1952, having a design
output of 200 kW (electrical).

Nuclear Fission
“A mechanism by which a
heavy nucleus absorbing a
neutron might become
unstable and split into two
lighter nuclei.”

Conditions
 Slow neutrons
 Fissionable material should be unstable
 Critical mass of the enriched Fissionable
material
– Critical mass is the minimum mass of fissionable
material required to sustain the fission reaction
– Enrichment was a way to increase the proportion of
fissionable material (U-235) and aid in the chain
reaction.
Fission Chain Reaction
Chain reaction, a process in which one
of the products of a reaction initiates
another identical reaction

When natural uranium is bombarded by neutrons, the chain
reaction cannot be sustained. Too many neutrons are
absorbed by other entities without leading to fission. To see
why, we need to look at the natural composition of uranium.
Uranium-238: 99.27%
Uranium-235: 0.72% and a trace of uranium-234.
The only one of these isotopes that undergoes fission is
Uranium-235. Uranium-238 does absorb neutrons, but the
uranium-239 that then forms reacts by beta emission rather
than nuclear fission
Why U-235 should Enriched?

Products
 2 new smaller nuclei
 2 or 3 free neutrons
 Huge amount of ENERGY
γ-Rays
– Heat
– Sound
– Light

Where does the Energy come from?
 Sum of Mass of products < Original Mass
 “Missing” Mass (~0.1% of Original Mass) has been
converted to energy
 E=Δmc^2
 U235 + n → fission + 2 or 3 n + 200 MeV

E=Δmc^2
 A very small amount of matter is equivalent to a vast
amount of energy.
 For example, 1 kg of matter converted completely
into energy would be equivalent to the energy
released by exploding 22 megatons of TNT.

 Nuclear fuel
 Neutron moderator
 Coolant
 Control rods
 Pressure vessel
 Reactor Protective System
(RPS)
 Emergency Core Cooling Systems
(ECCS)
 Steam generators (not in
BWRs)
 Containment building
 Boiler feed water pump
 Turbine
 Electrical generator
 Condenser

Moderator
 The fuel rods are
surrounded by a substance
called a moderator
– Function: It slows the
neutrons as they pass
through it.
– Example:
 Normal water
 Gas Cooled
Graphite
Moderated

References
 “Basic Nuclear Fission.” ThinkQuest. Accessed from: http://library.thinkquest.org/17940/texts/fission/ fission.html?tqskip1=1.
on 2-13-05.
 General Atomics. FusEdWeb: Fusion Energy Educational Web Site. accessed from: http://fusedweb.pppl.gov/. on 2-13-05.
 Godfrey Boyle, Bob Everett, Janet Ramage. Energy Systems and Sustainability. Oxfoord University Press 1998.
 How Stuff Works. “How Nuclear Power Works.” Accessed from: http://people.howstuffworks.com/nuclear-power2.htm. on 2-
13-05.
 “Nuclear Fission and Nuclear Fusion.” Accessed from:http://chemed.chem.purdue.edu/genchem/
topicreview/bp/ch23/fission.html. on 2-13-05.
 http://www.chem.duke.edu/~jds/cruise_chem/nuclear/pros.html
 http://starfire.ne.uiuc.edu/~ne201/1996/kopke/problems.html
 http://members.tripod.com/funk_phenomenon/nuclear/procon.htm
 http://www.world-nuclear.org/info/inf69.htm
 http://nuclearhistory.tripod.com/history.html
 www.chemcases.com


Nuclear reactor

More Related Content

What's hot

Viewers also liked

Similar to Nuclear reactor

Recently uploaded

Nuclear reactor