High Beta Radiation on Floor Surface in Reactor 2 Building at #Fukushima I Nuke Plant

As Toshiba workers splashed strippable paint on the floor at the Truck Bay Door of the Reactor 2 building (southwest corner) and stripped the paint to remove radioactive materials on the floor to lower the radiation for the future work (installing thermocouples), they were mostly removing the radioactive materials emitting beta radiation.

Outside Fukushima I Nuclear Power Plant, if the gamma radiation levels are measured in microsievert/hour in single or double-digit (i.e. 2 microsieverts/hour or 20 microsieverts/hour), they are considered high. The samples of the "black dust (thing, material, plant, dirt, etc.) measure anything from 0.6 microsievert/hour to over 50 microsieverts/hour depending on the locations, usually measuring gamma ray only.

At the entrance of the Reactor 2 building, the radiation levels on the floor are measured in millisieverts/hour. Of the four decon methods tried on the floor, vacuuming and strippable paint were somewhat effective in reducing the gamma radiation. Strippable paint was the most effective in reducing the beta radiation, and wet mopping and vacuuming were somewhat effective. Dry mopping spread the beta contamination, instead of reducing it.

10 millisieverts/hour is 10,000 microsieverts/hour.

I'm waiting to see if TEPCO does the nuclide analysis of the vacuumed dust or stripped paint, but TEPCO being TEPCO I don't have much hope. I'd love to know what kind of radioactivity by what nuclide would cause such high radiation levels.

From TEPCO's Working Group meeting reference material, pages 8 to 18 (I added English labels; 5/28/2012):

All this work is to later install thermocouples in the Containment Vessel, and that will have to be done by human workers. The Truck Bay Door is one of the two ways to get to the possible installation locations (there are two). Near one of the installation location candidates, there is a spot whose surface radiation exceeds 3,000 millisievert/hour (3 sieverts/hour or 3 million microsieverts/hour, take your pick). TEPCO's first choice is to install on top of the TIP Room by entering from the Truck Bay Door (access route 1, in blue). They may not be too keen to do the installation work near 3,000 millisievert/hour location...

Tweet