The Union of Concerned Scientists, which bills itself as “the leading science-based nonprofit working for a healthy environment and a safer world,” has issued a call to nuclear power plant operators to change the way they store highly radioactive spent fuel rods.
Currently, at many sites including the San Onofre Nuclear Generating Station, when reactor fuel is no longer usable, it’s moved to a temporary storage pool, where water is circulated to ensure the fuel rods, which continue to generate massive amounts of heat for decades after use, don’t overheat and cause their casing to catch fire, releasing radiation into the atmosphere.
Since there is no permanent storage site for spent nuclear fuel in the United States, hundreds of tons of it have been accumulating on the sites of power plants for decades. Most of the pools designed for temporary storage have been “re-racked” to allow up to five times as much fuel to be placed into storage as the pools were designed to hold.
Because these facilities are generally outside the primary containment meant to prevent radiation release in an emergency, they’re both more susceptible to forces such as a terrorist attack and more likely to release large amounts of radiation in the event of an incident. The San Onofre site does use the containment structure of its decommissioned Unit 1 reactor as a storage area for some fuel.
What the group is proposing instead of exposed fuel tanks for long-term storage of spent fuel is what’s known as “dry cask storage.”
After about five years in a pool, fuel rods will have cooled enough to be inserted into large concrete and steel structures, each holding about 15 tons of radioactive waste. These vessels are preferable, the Union says, because they are less susceptible to attack, hold less fuel in one containment vessel than a pool, and make the pools themselves safer by virtue of not overloading them. This makes the cooling process itself less challenging and extends the time workers would have to respond to an emergency such as a draining of the pool before fire risks present themselves.
The dry casks are also transportable, meaning fuel would already be packaged for shipment to a permanent storage site, if and when such a facility comes online.
The Union is asking the Nuclear Regulatory Commission to consider a rule requiring all spent fuel to be moved from temporary cooling pools to dry cask storage within five years of it being removed from a reactor, and to implement safeguards designed to protect cask sites from terrorist attack.