Binding Energy, Mass Defect, & Einstein Equation

Ok, today update is 3 topics which are

1) Binding Energy (BE)
2) Mass Defect
3) Einstein Equation, E=mc2

BE in scientific terms is the amount of energy that must be supplied to a nucleus to completely separate its nuclear particles(nucleons). This definition is based on the fission process, whereby in order to separate the nucleons, we bombarded a nucleus with a minimum amount of energy known as BE.

Next, we go to mass defect. By scientific definition, mass defect is the difference between the mass of the atom and the sum of the masses of its constituent parts. To make this clear, let say I can take a water molecule H2O. If I can measure the weight of 1 H2O molecule, its mass is not the same as the mass of 2 Hydrogen atom + 1 Oxygen atom which is not combined.

How could this happen? Well, its due to the theory of mass defect as explained above. Besides that, the loss of mass is due to BE. Scientists believe that a portion of energy has been release which compromise the loss of mass in an atom if that particular atom has been separated within its neutron as shown if the figure above, when the fission process occurs. Next thing is related to Einstein famous equation as shown below:

So, people might ask how are BE, E=mc2 & Mass Defect relate to each other?? The answer is the amount of energy loss through Mass Defect is known as Binding energy, yes you all know that in the previous elaboration. In addition, the amount of energy lost through mass defect or rather the total amount of BE can be calculated thanks to Einstein. This is because, his equation has proven that 1amu (atomic mass unit) is equivalent to 931.5 MeV (mega electron volt) and the total Binding Energy in MeV is 931.5MeV multiplied with the total of Mass Defect in amu units as shown below:


So how does this relates with our life? Basically, if we can calculate BE/A where A is the atomic mass for each perspective elements, we will get that the highest value of BE/A is found in iron or rather Fe-56. That explains how come iron is abundant on Earth - due to its high BE/A value. Hope you learn something here =).

Xenon

Xenon that we are going to discuss here is not the xenon flash in mobile camera or xenon gas which is one of the member in inert gas family. It is Xenon-135 that we are talking about. Being one of the fission products in reactors, and with its significant neutron absorption cross sections, Xenon-135 is not very "welcomed" or "liked" by nuclear reactor operators or designers. It removes neutrons from the reactor, affecting the thermal utilization factor and thus keff and reactivity. It will builds up to an equilibrium level and absorbs neutrons up to an extend that, even when the reactor is shut down, it goes through a peaking transient that can affect the ability to restart the reactor.


Xenon-135 is produced in 2 ways. It is produced as a daughter in a radioactive decay chain (from Iodine-135) and also as a direct yield from fission. By all means, it can be "eliminated" or "wasted" by radioactivedecay and also by absorption of a neutron to become Xenon-136 which is a weaker absorber. Such "elimination" process is also knowned as poison removal from the reactor, as Xenon-135 is considered as poison and undesirable in the reactor.

Now, let us see the effect of xenon on reactivity. When a new reactor was started up, it was xenon-free; as the reactor goes critical at low power (low flux) xenon starts to be produced but in a negligible amount. However, when the reactor is brought up to high power, the xenon will builds up to an extend that the operators have to withdraw control rods in order for the reactor to maintain the critical state as if the control rods remain, the reactor will face deficit in neutrons.

Hope this post will provide you readers with better understanding of xenon in nuclear field. Thank you for viewing and again do not hesitate to LIKE and COMMENT! =)

Reactivity II

WARNING!!! ... Today topic is slightly nuclear science tuned. Therefore it might be a bit complex, but we are ready to be received comments and questions. =)

Recalling back, reactivity is define as fractional change in neutron population per generation. But today we are more into reactivity coefficient.

In general, reactivity coefficient is governed by 4 other important coefficients which are:

1) Moderator temperature coefficient

2) Fuel temperature coefficient

3) Pressure temperature coefficient

4) Void temperature coefficient

Moderator temperature coefficient, are found to be more effective for light moderators rather than heavy moderators. This is because, light moderator can remove more energy than heavy moderators. Do note that moderator can be in 2 conditions which is under moderated or over moderated. Under moderated condition will help the nuclear system to have self-regulating effect. This means that the reactivity and power produced by the nuclear power plant is under control automatically due to the nature of the system. This will be a relief to all nuclear engineers. On the other hand, over moderated is very dangerous. This is because, over moderated condition will caused the reactor to have higher reactivity, and this will lead to more power being produced. With the high amount of power being produced, the temperature of the core will significantly increase and causes the core in the nuclear reactor to be melted down. Hence, for every nuclear reactor, under moderated condition is always the best choice. But, how do we know if the system is under moderated or over regulated? This can be done by calculating the moderator-to-fuel-ratio, which is a ratio of moderator and fuel.

More explanation regarding moderator will be given in future, I promise. This is because, we need to fulfill certain criteria for our blog on a daily basis and i am rushing out of time.

Fuel temperature coefficient is rather hard to be explained without the graphs, but in short, it can be defined as the change in reactivity per degree change in fuel temperature. This means that there is an increased tendency of the fuel to absorb neutron as the core temperature begins to increase. This is because, an increase in the core temperature will causes the power level and the control chain reaction to be increased. Hence, it will contribute to higher reactivity.

Pressure temperature coefficient is usually negligible in reactors. This is because, most nuclear reactors uses sub-cooled liquid which means that the liquid density is nearly constant and does not change significantly within the nuclear power plant operating pressure.

Void temperature coefficient, is the change in reactivity per percent change in void volume. Hence, it means that void temperature coefficient is the result of the formation of the steam voids in the moderate. An example is, in theory air bubbles formation in most pipe (closed system) calculation is neglected if and only if the value is small enough. However in reality, air bubbles really does exists and it does contribute to a very minor extend such that its existence can be neglected.

That's all for now ....

P/S Sorry for no cool pictures were being uploaded, but it will ... tomorrow on the fun facts label!!

Reactivity I

In nuclear science, reactivity can be define as

a) a measure of the departure of a reactor from critically or;
b) fractional change in neutron population per generation

Both definition are the scientific definition regarding reactivity. Therefore what does reactivity really means? For us, we believe that reactivity means that the total amount of neutron in the nuclear reactor. This is very important to note as the amount of neutron population will determine if our reactor have enough power to generate electricity, beside ensuring that the nuclear reactor is safe. This is because, neutron is used to to start the nuclear fission process as describe in the post below. Hence, if the neutron population is beyond control, it will result in accidents such as Chernobyl and also 3 Mile Island. In short, reactivity, in nuclear science is a concept which will help us determine the number of neutron present in the "core" after a certain amount of time.

Since we know that neutron population will affect the reactivity, hence reactivity can take place to determine the conditions of the nuclear reactor. There are 3 main conditions which are

1) Sub critical
2) Critical
3) Super critical

Each of the above stage is determine by a ratio which is referring to the rate of neutron created in the "core" divided by the rate of neutron which is being destroyed in the core. Hence, the output of this process can cause the neutron to be decrease (which is known as sub critical), increased (which is known as super critical) and also same (which is known as critical). In fact, to control the amount of neutron which is being produced, the control rod (made of Boron, Cadmium and etc) will be placed in between the nuclear fuel.

So, that's all for now ... more to come later, please do anticipate it! thank you =)

Briefly About How Nuclear Energy Produced

                                                                    ( uranium-235 )
 
Nuclear energy is energy in the nucleus (core) of an atom. Atoms are tiny particles that make up every object in the universe. There is enormous energy in the bonds that hold atoms together.

      
       Nuclear energy can be used to make electricity. But first the energy must be released. It can be released from atoms in two ways: nuclear fusion and nuclear fission. In nuclear fission, atoms are split apart to form smaller atoms, releasing energy. Nuclear power plants use this energy to produce electricity.

        In nuclear fusion, energy is released when atoms are combined or fused together to form a larger atom. This is how the sun produces energy. Fusion is the subject of ongoing research, but it is not yet clear that it will ever be a commercially viable technology for electricity generation.

Stay tune for further journey towards Nuclear Technology with us..