In the last year, TEPCO has continued its efforts to reduce groundwater flow though the site, has capped the port sediments to reduce the risk of resuspending radionuclides, and has begun evaluating the current state within the primary containment vessels of reactors 1 – 3 while also working on construction of the cranes that will be necessary for eventual removal of spent fuels and decommissioning.
Groundwater flow at the site has been reduced by two-thirds since freezing of the ice wall began at the end of March 2016. The wall has been frozen in a phased approach and currently roughly five sections of the wall on the mountain side of the site have yet to be frozen which should further reduce water flow.
Two layers of capping sediments have been laid down within the Fukushima marine port in an effort to limit resuspension of radionuclides in the sediments through water or animal movements of sediments. The areas immediately adjacent to the reactors were covered in 2012, but the cap over the rest of the port was completed in December 2016. Water samples within the port show that contamination has decreased substantially since 2013 and that levels of 134Cs have dropped below the TEPCO detection limit (280 – 640 Bq m-3) in most locations. Levels of 137Cs remain between 480 and 3,100 Bq m-3 within the port. Immediately outside the port, levels of both 134Cs and 137Cs are below detection limits (420 – 800 Bq m-3). While these levels far exceed what we are measuring on the west coast of British Columbia, and are far higher than InFORM detection limits, they are a significant drop compared to what was seen even in 2013 and are below the Canadian action level for drinking water of 10,000 Bq m-3, though drinking seawater is never a good idea for humans.
At units 1 and 3, construction of building covers and cranes to remove debris and materials from the spent fuel pools is ongoing. Gaining more press attention were the results and images from two robotic incursions into the primary containment vessel of reactor 2 in January. Not unexpectedly, as the robots approached to the reactor pressure vessel, radiation levels increased to the highest levels yet measured at the site, potentially fatal to humans if exposed for only a few seconds. While the robots were disabled by the conditions, the images are vital for developing an initial plan later this year for the lengthy decommisioning process ahead. Robotic investigations of the primary containment vessel are planned for reactor 3 in the coming weeks. Additional robotic imaging missions will be necessary to obtain a better picture of the damages sustained and the current fuel placement after the meltdowns in 2011.
Additional recent reporting from Science.