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The main feedwater pump failure in the secondary cooling system led to rising reactor pressure, triggering a pilot-operated pressure relief valve (PRV) on the primary side to lift and initiate an automatic shutdown of the pressurized water reactor (PWR) and steam turbine-generator. However, the PRV didn't reseat, causing water discharge for over 2 hours. Misleading control room indicators led operators to believe the PRV was closed and that too much water was injected, resulting in lost coolant. The uncovered reactor core overheated due to coolant loss. Attempts to restart cooling were hindered by steam and hydrogen build-up, vented into containment. Public emergency declaration only occurred around 2 hours 50 minutes into the incident.
Ask yourself and your crew:
- How can something like this happen here (e.g. on our site)?
- What safety measures (i.e. procedures, controls/barriers) do we have in place to mitigate the risk?
- How do we know the risk controls/barriers are working?
- What improvements or changes should we make to the procedures, controls/barriers or the way we work?
Original content courtesy of IChemE Safety Centre
