Neutrons can be slowed down even by ordinary water which has hydrogen-nuclei H 1 1 having mass almost equal to that of neutron. Then, why is heavy water used for this purpose in a reactor?

The heavy water is used in a nuclear reactor as a moderator. It slows down the fast-moving neutrons produced during the fission reaction in a nuclear reactor. Hydrogen nuclei present in ordinary water have almost the same mass as that of a neutron and therefore is suitable for elastic scattering with them. But Hydrogen nuclei H 1 1 have a greater probability of capturing the colliding neutrons, therefore, forming deuterium H 1 2 . The reaction is shown below. 1 H 1 + 0 n 1 → 1 H 2 + γ Heavy water has a negligible cross-section for neutron capture, and it is also suitable for slowing down the neutrons. Hence, it is preferred over ordinary water as a moderator.

Why is it difficult to separate U 235 92 from U 238 92 ?

Isotopes can be separated only by some physical process based on atomic-mass, like diffusion. In natural uranium, the ratio of U 235 and U 238 is 1 : 145 , and the ratio of their atomic masses is very close to 1 . So, the difference in their atomic masses is very close to 1 and correspondingly the difference in the root-mean-square values of velocities of the atoms of these isotopes is very small v 1 r m s v 2 r m s = m 2 m 1 . Hence, to separate them, some gaseous compound of uranium U F 6 is taken, and it has to be diffused thousands of times in ultracentrifuges in series to get the required concentration of U 235

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Which of these instruments are used to detect or monitor nuclear radiation ?

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Important Questions on Radioactivity

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Which of these following methods is the most suitable for disposal of nuclear waste?

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Write a note on the following:

Radio active wastes

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The particles not emitted by radioactive substance are

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Write a note on the following:

Radio active wastes.

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In a radioactive decay chain, the initial nucleus is

_{90}^{232} Th

. At the end, there are

6

α

-particles and

4 β

-particles which are emitted. If the end nucleus is

_{Z}^{A} X, A

and

Z

are given by:

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How did generation of electricity by nuclear energy create serious problem in living organisms?

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Why is the radioactive waste considered harmful?

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The effect of today's radioactive fallout will probably be more harmful to children of future generation than to present day children because

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_____ waste is a type of radioactive waste that is considered to be a highly potent pollutant.

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How should the storage and disposal of nuclear wastes be done?

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The numbers of nuclear divisions involved in a ciliate undergoing binary fission is

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A triglyceride can have how many different acyl groups?

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Chernobyl and Three Mile Island are related with which of the following?

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Write a short note on radioactive waste with example.

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Initially, nuclear energy was considered as a non-polluting way of generating electricity.

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Relative biological effectiveness (RBE) is usually referred to as damages caused by

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Physics>Atomic Physics>Radioactivity>Radioactivity all Around

Neutrons can be slowed down even by ordinary water which has hydrogen-nuclei $({}_{1}H^{1})$ having mass almost equal to that of neutron. Then, why is heavy water used for this purpose in a reactor?

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What type of serious problems arise by using nuclear energy?

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Why is it difficult to separate

{}_{92}U^{235}

from

{}_{92}U^{238}

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Fast neutrons can easily be slowed down by:

Which of these instruments are used to detect or monitor nuclear radiation ?

Important Questions on Radioactivity

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