(b) The main reactions that fuel the Sun are the fusion of hydrogen nuclides to form helium nuclides. However, other reactions do occur. In one such reaction, known as the triple alpha process, three helium nuclei collide and fuse to form a carbon-12 nucleus.

(ii) Calculate the energy released in the triple alpha process.

The isotope of polonium, ${}_{81}^{218}\mathrm{Po}$, decays by the emission of an $\alpha$ -particle with a half-life of $183 \mathrm{s}$.

(a) In an accident at a reprocessing plant some of this isotope, in the form of dust, is released into the atmosphere. Explain why a spillage in the form of a dust is far more dangerous to health than a liquid spillage.

The isotope of polonium, ${}_{81}^{218}\mathrm{Po}$, decays by the emission of an $\alpha$ -particle with a half-life of $183 \mathrm{s}$.

(b) It is calculated that $2.4 \mathrm{g}$ of the isotope is released into the atmosphere. The molar mass of polonium is $218 \mathrm{g}{ \mathrm{mol}}^{-1}$. Calculate the initial activity of the released polonium.

Avogadro's number $=6.63\times {10}^{21}$

The isotope of polonium, ${}_{81}^{218}\mathrm{Po}$, decays by the emission of an $\alpha$ -particle with a half-life of $183 \mathrm{s}$.

(c) It is felt that it would safe to re-enter the laboratory when the activity falls to background, about $10 \mathrm{Bq}$. Calculate how many hours must pass before it is safe to re-enter the laboratory.

A nuclear reactor is fuelled by fission of uranium. The output from the reactor is $200\mathrm{MW}$. The following equation describes a typical fission reaction:

${}_{92}{}^{235}\mathrm{U}+{}_0{}^1\mathrm{n}\to {}_{92}{}^{236}\mathrm{U}\to {}_{35}{}^{87}\mathrm{Br}+{}_{57}{}^{146}\mathrm{La}+3{}_0{}^1\mathrm{n}$

(a) State and explain into what form the majority of the energy released in the reaction is transformed.

A nuclear reactor is fuelled by fission of uranium. The output from the reactor is $200\mathrm{MW}$. The following equation describes a typical fission reaction:

${}_{92}{}^{235}\mathrm{U}+{}_0{}^1\mathrm{n}\to {}_{92}{}^{236}\mathrm{U}\to {}_{35}{}^{87}\mathrm{Br}+{}_{57}{}^{146}\mathrm{La}+3{}_0{}^1\mathrm{n}$

(b) (i) Calculate the energy released in the reaction. The kinetic energy of the captured neutron is negligible.

Mass of electron, $m=1.67\times {10}^{-27 }kg$

A nuclear reactor is fuelled by fission of uranium. The output from the reactor is $200\mathrm{MW}$. The following equation describes a typical fission reaction:

${}_{92}{}^{235}\mathrm{U}+{}_0{}^1\mathrm{n}\to {}_{92}{}^{236}\mathrm{U}\to {}_{35}{}^{87}\mathrm{Br}+{}_{57}{}^{146}\mathrm{La}+3{}_0{}^1\mathrm{n}$

(b) (ii) Assume that the energy released in this fission is typical of all fissions of U-236. Calculate how many fissions occur each second.

A nuclear reactor is fuelled by fission of uranium. The output from the reactor is $200\mathrm{MW}$. The following equation describes a typical fission reaction:

${}_{92}{}^{235}\mathrm{U}+{}_0{}^1\mathrm{n}\to {}_{92}{}^{236}\mathrm{U}\to {}_{35}{}^{87}\mathrm{Br}+{}_{57}{}^{146}\mathrm{La}+3{}_0{}^1\mathrm{n}$

(b) (iii) Calculate the mass of uranium-235 that is required to run the reactor for 1 year (Use Avogadro's no. = $6.02\times {10}^{23}$).