Chlorine leak as pipe burns away
35kg of chlorine were lost due to pipe burning away. The cause has not been totally identified. Chlorine and iron are known to react, but at temperatures greater than 200°C. It is possible that traces of water were left in during system checks, and that when the chlorine was turned on, the water initiated the reaction, causing the iron pipe to become hot enough for the reaction to take place.
As the pipe burnt away, one cannot be 100% sure of the cause. Water ingress is the most plausible answer, and goes to show the importance of proper procedures necessary for plant start-up when using such agressive chemicals.