In April this year, a citizen volunteer group in Tsukuba City in Ibaraki Prefecture set up "Ibaraki Citizens Radioactivity Measuring Station" to test food and soil for radioactive materials (iodine, cesium). The group uses AT1320A by ATOMTEX (Belarus) with an NaI scintillation survey meter.
The group says over 100 Bq/kg of radioactive cesium was detected from the barley harvested in 2011, using their detector. From the same barley, Tsukuba City had only detected 35 Bq/kg. Tsukuba City uses Hitachi NaI scintillation survey meter, according to the city's website. (The new safety limit for radioactive cesium is 100 Bq/kg.)
So why the huge difference?
It turned out that the city's measurement time was too short, and the software for the detector was not updated. When the city lengthened the measurement time and did the software upgrade, the city's detector found 115 Bq/kg of radioactive cesium.
What a surprise.
According to their blogpost on May 29, 2012, here's what happened:
At our Citizens Radioactivity Measuring Station, barley harvested in 2011 by one of our staff was found with 110 Bq/kg [of radioactive cesium]. We repeated the measurement a number of times by extending the measurement time, but the result was still about 100 Bq/kg.
The same barley had been tested before, using the detector of Tsukuba City. The result then had been 35 Bq/kg. The two numbers diverged so much, so we had it tested again by Tsukuba City's detector.
The result was 115 Bq/kg.
[Since the previous measurement,] the city lengthened the measuring time from 10 minutes to 30 minutes and did the software version update [for the detector], which allowed their detector to obtain the similar result as ours.
Based on this result, we made an oral request to Ibaraki Prefecture and Tsukuba City to re-test the barley grown in the neighborhood areas [of Tsukuba, I assume], but they said they wouldn't, because the barley was for "personal consumption".
After we had an opportunity to further discuss with them, we submitted the written request [to the prefecture and the city] today.
The group calls for the consistent and continuous monitoring of radioactive materials in food, and prompt and open disclosure of the results. For Tsukuba City in particular, the group is asking the city to (1) test commercially available food if the radioactivity in food for non-commercial, personal consumption exceeds 100 Bq/kg; and (2) test using the germanium semiconductor detector owned by the prefectural government when the radioactivity in food (commercial or non-commercial) exceeds 100 Bq/kg by the group's testing
Mainichi Shinbun (5/30/2012) reported on this written request from this group. In the article, Mainichi says "Tsukuba City stopped publishing the test results for the agricultural products for personal consumption".
This news hasn't got much attention in Japan, and the group's site does not have an update.