01․ Which of following are the fertile materials
The materials are not fissile but can be converted to fissile materials is called fertile materials. Pu239 and U233 are not found in nature nut U238 and Th232 can produce them by nuclear reaction.
02․ Which of the following are the fissile materials
The materials which are undergo neutron fission are U235, U233 and Pu239. These are called fissile materials.
03․ When a nuclear reaction is operating at constant power the multiplication factor is
As all neutrons released in the fission reaction are not up in propagating the chain reaction but some of these are lost to the surroundings. For maintaining chain reaction, it is essential that the number of neutrons after fission should be slightly more than the number before it to allow for the escape or leak of neutrons from the reactor core. The ration is known as multiplication factor. So it is defined by the ratio of number or neutrons produce in one generation to number of neutrons produce in the preceding generator. If multiplication factor is 1, that indicates the chain reaction will continue at a steady state. If multiplication factor is less than 1, the chain reaction will stop and if multiplication factor is greater than 1, the chain reaction will build up.
04․ A CANDU reactor uses
The word CANDU stands for Canadian Deuterium uranium. These reactor makes use to heavy water composed of the heavy hydrogen isotope as moderator to have maximum neutron economy and as a coolant also. Now heavy hydrogen isotope exists in nature in the ratio 1 : 6700 as compared to ordinary hydrogen and therefore, heavy water is very difficult and expensive to separate from ordinary water. As enrichment of uranium is costly affair so such reactors use natural uranium as fuel.
05․ Which one of following is employed as a moderator by CANDU type of slow thermal nuclear reactors
Heavy water composed the heavy hydrogen isotope as moderator to have maximum neutron economy and as coolant.
06․ A moderator material should have
The moderator is used to slow down the neutrons by absorbing some of the kinetic energy of neutrons by direct collision and thereby increasing the chances of fission. From the requirement of moderator, it is clear that the material should have light weight nucleus, So that it does not absorb the neutron as collides.
07․ The function of moderator in a nuclear reactor is
The moderator is used to slow down the neutrons by absorbing some of the kinetic energy of neutron by direct collision, thereby increasing the chances of fission.
08․ Nuclear reactors usually employ
Nuclear reactor is that part of nuclear power plant where nuclear fuel is subjected to nuclear fission.
09․ The power level of nuclear reactor can be increase by ( K = multiplication factor )
The multiplication factor(K) is defined by the ratio of number of neutron produce in one generation to number of neutron produced in the preceding generation. The desirable requirement of power reactors is that the system should be critical ( K = 1 ). For reactor control, the value of K is to be controlled. If K is greater than 1, the chain reactor will build bu. So at the time of starting of the reactor, the value of K is kept above unity. This increase the power level. Once the required power level has been attained, K is reduce to unity.
10․ Reflector nuclear reactor are made of
Since the reflector should have good neutron scattering properties and preferably a small tendency to absorb neutron, so beryllium is used to make reflector.
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