1. Different Types Of Nuclear Reactors
a nuclear reactor may be defined as a device in which energy is liberated
as a result of a chain reaction involving neutrons and fissionable
elements. it is a source of thermal and
radiant energy that utilizes nuclear reactions rather than chemical or electrical
processes.
nuclear reactors are of different
types depending on the purposes , nuclear
fuels and method of coolant circulations among others, below are the
classifications of a nuclear reactor;
· energy of the neutrons that produces
the fission
(a) fast , in fast neutron reactors
neutron moderators are not needed but a highly fissible fuel is necessary.
(b) intermediate or epithermal
(c) thermal
· nuclear fuel, based on these there
are three types of the reactor.
(a) natural, e.g uranium 235 of
0.7%, this uranium natural abundance
(b) slightly enriched uranium 235 of
about 1-2%
(c) highly enriched uranium 235 about 90%
(d) plutonium 239
(e) and uranium 233
· nuclear reactors are also classified
based on the method of heat removal , based on these we have
(a) Reactors based on circulations of
coolant only.
(b) fuel mixed with coolant
(c) moderator coolant
(d) and lastly fuel , moderator and
coolant
· nuclear reactors are also classified
based on purpose on which they are developed. they could be for
(a) for research
(b) prototype
(c) propulsion
(d) heat source
(e) electric power generation
(f) isotope productions
2)
What Does A Moderator Do In A Nuclear
Reactor
moderators are use to
control the speed of neutron and the
overall nuclear reaction, the moderator
can contain a light element such as hydrogen or carbon and is intermixed with
the nuclear fuel. a successive collision with the moderator nuclei will reduce
the energy of the fission neutron by 2Mev on average to the thermal level. in
the cause of slowing down many neutron escapes through the boundaries of the
central core.
1)
How Does A Chain Reaction Occur In
Nuclear Fission
a nuclear reaction is
said to chain reaction when it is self-sustaining, it occurs only if the number
of neutrons in an assembly of fissionable materials can be maintained constant.
this possible only because more than one
neutron is produced for each neutron that set off the fission process. assume that the reactor contains uranium-235 as fuel and operating with low
energy neutrons. the fission of a nucleus of uranium 235 gives rise to about
2,5 neutrons on average and 190MeV of energy. the kinetic energy of the fission
fragments is the primary source of useful heat which can be removed by
circulating coolant.
the reaction is self-sustaining or critical if
the neutron released from the fission eventually produced one more fussion, a
sub-critical reactor is one when sustained by a separate supply of neutrons ,
in the supercritical reactor the neutrons the neutron will accumulates.
2)
What Is A Radiation Shield In A
Nuclear Reactor
a nuclear shield is a protection
against harmful nuclear radiations, it provides protections for personnel from
neutrons and gamma rays.
Fission Product Poisoning
In a nuclear reactor there are other product that are
poisonous personnel, all fission product
are beta active , two poisons of particular concern are produced in nuclear
fission are xenon-135 135xe and 149sm samarium 149, 135te which is
formed in 61.% of fission processes
produces .
The 135xe is produced from the decay of 135ln with a half
life of 6.7hrs and decays with a half life of 9.2hrs.
What Is Neutron Moderation
a neutron moderation is the process of slowing
down the speed of a fast neutron, this is aimed at to reduce and control the
rate of nuclear reactions, this function
is done by a moderator in the nuclear reactors, these moderators are piece
either hydrogen or carbon intermixed with the nuclear fuel. when a fast neutron get contact with a
moderator it loses its energy an amount 2 Mega evolt on average, this help to
slow down the neutron and the entire nuclear fission reaction.
Comparing Nuclear Fusion And Fission
booth the two a nuclear processes, the fission
involves the splitting of a large nuclear in two or two unequal nuclei, the nuclei involve in fission is a very large
nuclear may or may not be radioactively
stable, in the reaction process, a
particle called a target is used to bombard the large the nuclear, what follow next is that the nuclear become
unstable and must break into two
unequal lighter nuclei, this process is
followed by a tremendous release of heat and radiations, apart from the two
nuclei other fission products are also released like gamma rays, ,2 or 3
neutrons particles. fission process involve heavy nuclei, little energy is
needed to kick it start and can be harness
for human use.
Whereas fusion reactions involves the fusing
of two single nuclei into a new atom, the fusing nuclei are lighter than
the product. it require large energy or heat large enough to bring the two
nuclei together. the energy required is almost equal to what is released in
fusion reaction. Sun produces its energy from nuclear fusion reactions , tars
also do so, the only man-made fusion reaction is the hydrogen bomb.
the fusion
reactions involving the heavier isotope of hydrogen, deuterium and
tritium produce energy in a controlled manner on earth. two deuterons fuse together
to produce either helium -3 plus a
neutron or hydrogen-3 plus a proton.
the fusion of deuteron with a triton is even
more exothermic because it leads to
production of helium-4 with its very high internal binding energy.
the T(d,n) 4He,
D(d,n) 3He, and D(d,p)3H
these reactions are easily produced in the laboratory by bombarding target rich
in deuterium or tritium with deuterons
which has been accelerated.
What Is Energy Released Nuclear
Fission
the energy
released nuclear fission varies between many possible fission modes, however
the average release per fission is about 207mev and of this, some 200mev is
converted as heat within the reactor
core.
how
does an atom break in nuclear fusion
according
to liquid drop model in nuclear physics, the repulsive force is
sufficient to overcome attractive force due to the few nucleons which continue
to be within the range of the nuclear force in the elongated region between the
two spherical sections and the highly deformed nucleus thus splits into two, because
of the large neutron excess, either two or three neutrons are released at
fission. fission into two nuclei of equal or approximately equal mass number is
very rare.
Difference Between Artificial And
Natural Transmutation
Natural
nuclear transmutations or the spontaneous decay of a nuclide; the release of
either alpha, beta or gamma ray in natural atomic transmutation is independent
of heat or pressure and does not require energy and it only occur with
radioactive element.
Particles
released are only alpha, beta or gamma ray and the original atom changes atom
undergo transmutation (changes from one nucleus to another).
when an
alpha particle is released an atom lost two from it atomic number and four from
it nuclear mass, it dropped two places from the periodic table, when atom
releases a beta particle it gain one to it atomic number while nuclear mass
does not change, therefore it rises one places in a periodic table of elements.
whereas in artificial transmutation, the
change of a nuclide to another require
energy and this is only done through fission of fusion nuclear reaction, when a large nuclei is split into lighter
ones it is said to be fission , while fusion occur when two light nuclei
combine to form a heavier nuclei.
artificial transmutation may occur with both
stable and unstable atoms, it involves the bombarding of with particles such as
alpha, neutron, protons , deuteron.
beside alpha
particles and beta particle, other particles may be emitted .
When Substance Decays Through Its
Half Life Does The Atom Change?
actually when an atom under radioactivity and decays through it half life, it is the
energy of the atoms that reduces to half
and not the actual atom. otherwise the
nuclear
energy from uranium-235
the fission
of uranium-235 produces from radioactive nuclei, some neutrons and release
nuclear energy are shown by the equation
235U + 1n = 144Ba56
+ 90Kr36 + 2 1n + energy.
The mass of the
original substances = 235.124 +1.009= 236.135amu
the mass of the product
144.934 + 89.974 + 2.018 =235.926.
Therefore the mass of the original substance
is greater than the mass of the product.
therefore mass lost = 236.133- 235.926
=0.207amu
but the mass
of 1 amu =1.6 x10-27kg and velocity of electromagnetic waves = 3 x108m/s
from Einstein energy equations
E = MC2
0.0207 x1.6 x 10-27 (9 x 1016)
= 3 x10-11J
just for 0.207 amu
Comparing
Nuclear Energy And Other Source
Therefore 3x 10-11J joules of energy is released for every atom
of uranium 235U that undergo
fission . this looks small. but let us calculate the energy released when 1kg of uranium undergo fission.
in 1kg of uranium, 235U , there
are about
100/235 x
6x1023 atoms.
therefore
energy released when 1kg of 235U
undergo fission is
7.5 x 1013J
In order to quantify the amount of energy
released , let us look at it in terms of supply of domestic electricity.
1 units of electricity = 1 kwhour =1kw x 3600 seconds
3600kJ
therefore
number of units of electricity supplied when 1kg of uranium undergo fission is
7.5 x 1013J/3.6x
106= 2.0 x107 units
this I equal to the amount of energy supplied
when 3 , 000,000 kg of coal is burnt. this show nuclear is the cheapest source
of energy
How Nuclear Bomb Works
A nuclear
bomb is a nuclear chain reactor that operates in a rapid and uncontrolled
manner. It only needs a kick off start and the process continues.
Chain
explosion occur on e fission of uranium-234, 235U, only, when the quantity
of uranium is large, if the quantity is small, and undergoes nuclear fission
the secondary neutron escape from the piece before they cause another fission,
there is therefore a critical size of uranium 235U. Above which
chain explosion can occur, this is why nuclear bombs are in are in tons and megatons.
How Many Tons Of Tnt Is An Atomic
Bomb Equal To
if you want
to know how many megatons is a nuclear bomb Knowing fully that a kilogram mass
of uranium can produce energy equivalent to what 3 million kilogram of coal can
produces in electricity generations, the first fission bomb released an energy
same as 20,000 tons of TNT while the first thermonuclear bomb, hydrogen released
as must as 10,000,000 tons of TNT, it is
left for you to imagine what blast a megaton nuclear weapon will cause. A
hundred kilogram of nuclear bomb can detonate a whole city.
This is why they are called weapon of massive destructions;
nukes can wipe out the entire human population within some minutes.
Nuclear explosion produces radiations and
radioactive debris, this debris are remain of radioactive active atoms , with
half life varying half lives, this debris will continue spontaneously to emit
radiation which is harmful to human, plant , animal and the environment at
large.
The eat and
temperature reach in nuclear explosion are in the ranges of megakelvins, it has
the same burning effect as other conventional explosion but it’s explosion capability is million times per
kilogram greater than that of other conventional bomb.
What Is Nuclear Bomb Test
Nuclear test
are experiment done to determine three things about nuclear weapon.
1) Yields
2) Its effectiveness
3) And explosion capability
When a nuclear bomb is
been tested, a mushroom of cloud is seen and this rises some kilometers above
the earth surfaces, an atmospheric nuclear test will show a mushroom of fire
ball as observed in recent test.
A nuclear bomb, cannot be said to be fission
or fusion, though all know nuclear bomb kick off as fission bomb, but as the explosion
unveils both fission and fusion reaction occur in an uncontrolled manner.
When weapon drive must of its energy from fission reaction
it is said to be a fission bomb, they are most called atomic bombs or atom
bombs while those that require fission reaction to start are called fusion bomb
or thermonuclear or simply hydrogen bomb.
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