Topic Menu

Cyber-chess a chess instruction site

Nuclear Fission

Q9.

(a)

(i) State two physical features or properties required of the shielding to be placed around the reactor at a nuclear power station.

thick

high density

material giving minimal fatigue problems after irradiation

withstands high temperature

any two

(ii) Which material is usually used for this purpose?

(reinforced) concrete

(3 marks)

(b) Describe the effect of the shielding on the γ rays, neutrons and neutrinos that reach it from the core of the reactor. Also explain why the shielding material becomes radioactive as the reactor ages.

The effect of shielding on :

γ-rays - the intensity of gamma rays is (greatly) reduced by the shielding

neutrons - there is some absorption the speed or energy of the neutrons is reduced by collisions with the shielding

neutrinos - very little effect, most pass straight through

Why the shielding becomes radioactive:

Neutron absorption by nuclei within the shielding produces neutron rich or unstable nuclei by artificial transmutation. These nuclei become β– emitters and/or γ emitters, and these often decay to produce daughter radioactive isotopes.

(4 marks)

(Total 7 marks)