Nuclear Disasters and Groundwater

On March 11, 2011, a tsunami struck the coast of norther Japan, damaging the cooling system at the Fukushima Daiichi Nuclear Power Station.  Authorities worry that cracks in one or more reactor chambers could release a flood of contaminated water into the aquifer below.

On March 15, the Global Post interviewed Arnold Gundersen, a former nuclear plant operator who served as an expert witness in the investigation into the Three Mile Island accident.  Asked about the potential impact on groundwater of a meltdown at Dai-ichi he said, “Chernobyl had a meltdown, and that groundwater wedge is gradually working its way toward Kiev, which is a very large city [about 80 miles away]. That groundwater contamination lingers for 300 years. It’s not something that’s easy to mitigate.”

I have my doubts that the situations are comparable.  The position of the Dai-ichi plant on a marine coast suggest that groundwater flux would be steadily away from land.  While drinking water contamination warnings have been issued, this is probably related more to short lived isotopes and airborne deposition to reservoirs.  Even in the event of contaminated water directly discharging to the earth’s surface, soil would probably be more contaminated than groundwater.  The greatest danger to groundwater from this disaster will probably revolve around whether or not the waste from the disaster can be safely disposed.

How did the Three Mile Island Impact Groundwater?

On March 28, 1979, the cooling system failed at the Three Mile Island nuclear power plant in Middletown, PA.  The cooling water level dropped within the reactor, partially exposing the nuclear rods, which began to disintegrate.  Plant engineers managed to advert a full melt down, but radioactive gas and water discharged from the broken containment vessel.  Contaminated water probably impacted the Susquehanna River more than local groundwater.  In the short time that I have spent researching this post, I have only been able to find anecdotal evidence of elevated levels of radiation in groundwater after the event.  It may not have been well studied.

Operators halted the meltdown before the fuel core melted through the containment vessels and supporting cement pads.  If the core had come in contact with the relativity shallow water table, groundwater would have instantly vaporized, causing explosions and sending up a plume of radioactive steam.

Every-day plant operations at the plant probably pose a bigger threat to groundwater than the legacy of the accident.  In 2010, Greenepeace reported that 20 US nuclear power plants, including Three Mile Island, had admitted to leaking radioactive tritium into groundwater during the coarse of their normal operations.

How did the Chernobyl Disaster Impact Groundwater?

On April 26, 1986, a power surge caused an explosion in a reactor at the Chernobyl Nuclear Power Plant located in the former Ukrainian Republic of the Soviet Union.  The explosion and subsequent 10-day fire released a huge volume of radioactive fission products to the environment.  This event is considered the worst nuclear disaster in history.

In 2006, the International Atomic Energy Agency reported that the Chernobyl disaster has had less of an impact to groundwater quality than had the problematic disposal of the waste from the disaster.  Most radionuclides that were released in the immediate aftermath were either fast-decaying or had high soil partitioning coefficients.  The agency  found that the rate of transfer from soil to water of residual long-lived radionuclides was very slow.  However, the disposal of radioactive debris and contaminated trees in unlined waste pits has released a significant amount of radionuclides to groundwater.  Still, the effects of the radiation released on the earths surface dwarf the impact to groundwater.

Conclusions

While nuclear accidents are scary and attract a lot of attention, in the long run it is more important to focus on responsible management of nuclear power plants on a daily basis, and to properly store nuclear waste to keep it out of the environment.