Radiation

Today we saw our first really high radiation readings.   Although for now we think the most likely explanation is some problem with the geiger counter.

For a while we had repeated readings of up to 70 micro-sieverts per hour,  100x higher than our previous maximum.   

For comparison, one standard exposure limit for the general public is 1 milli-sievrt per year,  which is an average of 0.11 micro-sieverts per hour.  The Japanese government controversially raised their exposure limit to 20 milli-sieverts per year or an average 2.2 micro-sieverts per hour (and even higher for radiation workers).   So you don't want to be seeing repeated readings above 2, let alone 50-70!

After the initial very high and variable readings, our readings seemed to settle down for about 5 minutes in a range of 2-5 micro-siverts per hour, both inside and outside our apartment.    

Then Rika switched the device off to reset it, and we once again got readings down at our normal 0.1 to 0.3 range, including the same places where previously we had seen high readings.    

So perhaps there was some error with the device.    Or perhaps some local contamination on its case that was then wiped-off.   Still we'll be watching closely to see if this repeats, and for reports of other people in Tokyo getting high readings.