Questions

The cross-section data needed to answer these questions have been supplied here. To find further cross-sections, consult the Evaluated Nuclear Data File (ENDF).

Quick questions

You should be able to answer these questions without too much difficulty after studying this TLP. If not, then you should go through it again!

1. Check which elements are fissionable but not fissile:

   	a	U-233
   	b	U-235
   	c	U-238
   	d	Pu-239
   	e	Th-232

2. Which of the following are NOT suitable moderating materials?

   	a	Deuterium (A=2)
   	b	Helium (A=4)
   	c	Beryllium-9 (A=9)
   	d	Boron (A=11)
   	e	Graphite (A=12)
   	f	Iron (A=56)

3. Which of the following would NOT be classified as "Sabsorption" cross-sections?

   	a	(n, n)
   	b	(n, n')
   	c	(n, γ)
   	d	(n, f)
   	e	(n, α)
   	f	(n, p)

4. Which of the following discourages void formation?

   	a	More interstitial atoms.
   	b	Fewer interstitial atoms.
   	c	More vacancies.
   	d	Fewer vacancies.
   	e	More transmutation.
   	f	Less transmutation.

5. Which of the following material properties have lower values after irradiation?

   	a	Yield strength
   	b	Thermal conductivity
   	c	Electrical conductivity
   	d	Tensile strength
   	e	Ductility
   	f	Density
   	g	Creep rate

Deeper questions

The following questions require some thought and reaching the answer may require you to think beyond the contents of this TLP.

6. Zirconium minerals are often found with small amounts of hafnium present due to their chemically similar nature. Zirconium is also used as a primary component of Zircaloy, a cladding material designed to be almost transparent to neutrons.
   
   By comparing how the mean free path of a thermal neutron in pure zirconium differs from that of zirconium with 0.01% hafnium impurities, comment on the consequences of hafnium impurities in Zircaloy.
   
   (Zr: A = 91.22, ρ = 6.52 g cm⁻¹, σ_c = 0.18 barns;
   Hf: A = 178.49, ρ = 13.31 g cm⁻¹, σ_c = 105 barns)