After an EMP Event, Can A Nuclear Plant Shutdown Safely?

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If an electric pulse shut down the grid, how would nuclear reactors cool spent fuel rods? Image by Oliver Steinke

Nuclear Power Plant Shutdown After an EMP

When a electromagnetic energy-burst occurs, transformers can be destroyed in the electrical transmission lines carrying power away from the plant. When this happens, the nuclear power plant’s output is reduced to zero, and the plant shuts down. Nuclear power plants are designed to allow for sudden interruption of their output by many causes; lightening strikes, equipment failure and transmission failures, to name a few.

When a nuclear power plant loses off-site power, it is called a station blackout. All US nuclear power plants are designed to withstand this event with no core damage, through the automatic start of the emergency diesels. After the start of emergency power, the automatic shutdown of the plant commences. Control rods are dropped into the core, while water is pumped into the reactor to reduce the heat. The fuel is encased in a primary and secondary containment structure designed to withstand a potential core melt, should the pumps stop and fuel become uncovered.

Preventing a Nuclear Meltdown After a Blackout

Most station blackouts are assumed to be of short duration, concluded within 24 hours. With an electromagnetic pulse, however delays could extend from a short duration to months, and some hypothesize years, before power could be restored. Transformer parts can take one to two years to produce, and with potentially-reduced transportation efforts, maybe longer. Nuclear power plants typically have enough emergency diesel fuel to run for seven days, some up to thirty days, but all will need more fuel to continue the cooling operation in a prolonged station blackout. Depending on the size of the EMP and its effects, getting additional diesel to the plants in a timely manner may be difficult or impossible.

A recent petition has been submitted for rulemaking to the United States Nuclear Regulatory Commission on perhaps the most pressing issue of a long-term station blackout, “Regulations that would require facilities licensed by the NRC under 10 CFR Part 50 to assure long-term cooling and unattended water makeup o f spent fuel pools. There are 104 nuclear power reactors operating in the United States at 65 sites in 31 states.”

Each of these power plants has at least one and possibly more spent fuel pools. A long-term loss of outside power could interrupt the circulation of cooling water to the pools. Spent fuel pools carry depleted fuel for the reactor, up to five times the fuel in the core. Typically, this spent fuel has had considerable decay time reducing radioactivity and heat, but newer discharged fuel still produces heat and needs cooling.  Housed in high density storage racks, contained in industrial-design buildings that vent to the atmosphere, radiation containment is not provided for the spent fuel racks. With a long outage, where emergency power may be unavailable or unsustainable, cooling may not be possible. In this event, the water will heat and boil away, uncovering the spent fuel. The exposed fuel rods could then cause fires as well as the potential release of radioactivity.

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