Zirconium gives nuclear reactors their corrosion resistance — and gives machining shops a genuine fire hazard. Fine zirconium chips and dust ignite readily and burn violently. Drilling deep holes in zirconium is very doable; it is safe only if the chip and coolant handling is engineered for it.
Zirconium (and the Zircaloy alloys used in nuclear fuel) is strong, corrosion-resistant and neutron-transparent — why it lines reactor cores. It is also pyrophoric: fine chips, dust and fines ignite easily in air, and a zirconium fire burns at extreme temperature and is almost impossible to extinguish with water. Everything in the process design — chip size, coolant, cleanup — exists to prevent the fine-chip state.
| Parameter | Zirconium / Zircaloy |
|---|---|
| Gundrill Vc (m/min) | 20–40 |
| BTA Vc (m/min) | 20–35 |
| Feed @ Ø10 mm (mm/rev) | 0.02–0.05 |
| Coolant | Water-based emulsion or oil |
| Coolant pressure | 50–120 bar (gundrill) |
Carbide gundrills with sharp, positive geometry and a moderate edge hone. Coated tools (TiN/TiAlN) reduce galling; uncoated sharp edges work well at low speed. Guide pads must be well-matched — a zirconium bore that grabs the pads can spin the tool. Keep coolant flowing at all times, including during retract.