Disaster by Design
The March 2011 disaster at the Fukushima Daiichi nuclear plant in Japan did not reveal flooding to be a nuclear safety hazard; it reminded us of this well-known threat. Flooding from internal sources (e.g., broken pipes and failed storage tanks) and from external sources (e.g., heavy rainfall and swollen rivers) had long been recognized as a risk to be managed with an array of flood protection measures. As the following summaries—an abridged sampling among many such events—indicate, there were numerous reminders before Fukushima.
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LaSalle (Illinois): Fission Stories #113 described the May 13, 1985, event where one of the circulating water pumps that sent cooling water from the lake through the plant stopped running. A worker dispatched to the pump house to investigate the problem discovered the building filling with water through a broken rubber expansion joint. The pump house flooded to a depth of 15 feet, disabling all the circulating water and service water pumps for both reactors.
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The summaries indicate that adequate flood protection relies on (1) preventing water from entering areas housing vital equipment, (2) locating vital equipment in diverse locations to lessen the chances for a flood to disable it all, (3) draining areas containing vital equipment faster than then can flood, and (4) detecting a flooding condition as soon as possible to maximize the time available to successfully intervene.
Flooding is but one of many risks to be managed at a nuclear plant. Properly managing a single risk factor would be relatively simple. Properly managing multiple risk factors, often at odds with one another, complicates the task quite a bit. For example, installing fire headers and fire sprinklers within a nuclear power plant decreases the fire risk. But it increases the flooding risk. It’s not a matter of choosing which risk to manage and which to neglect; it’s a matter of understanding all the risks and developing designs and procedures that effectively manage them.
Read more at Flooding at the Nuclear Plant: Disaster by Design/Safety by Intent #1
