Hf
Hafnium
Z = 72 · Transition Metal · 178.5 u
Nuclear Engineering Significance
Strong thermal neutron absorber (σ_a = 104 b) used in control rods, especially in naval reactors. Hafnium is naturally present in zirconium ores and must be removed (Hf < 100 ppm specification) during Zircaloy production to maintain cladding neutron transparency. The Hf/Zr separation is one of the more costly steps in cladding fabrication.
Basic properties
- Atomic number (Z)
- 72
- Standard atomic mass
- 178.5 u
- Category
- Transition Metal
Isotopes & cross-section data
| Isotope | Mass (A) | Half-life | ZAID | Libraries |
|---|---|---|---|---|
| Hf-174 | 174 | 2.0e15 y | .80c.71c.70c | |
| Hf-176 | 176 | Stable | .80c.71c.70c | |
| Hf-177 | 177 | Stable | .80c.71c.70c | |
| Hf-178 | 178 | Stable | .80c.71c.70c | |
| Hf-179 | 179 | Stable | .80c.71c.70c | |
| Hf-180 | 180 | Stable | .80c.71c.70c |