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March 28, 17:00, 2011

Measurement result of airborne nuclide and air radiation level in Tsukuba area: second report

KEK, in conjunction with National Institute for Environmental Study (NIES) have conducted the measurement to assess the airborne nuclide and air radiation level in Tsukuba area four times between 15 and 17 March as shown in the chart below.

KEK will have another measurement hereafter, and will report the result accordingly.

Measurement condition:

  1. Measurement point: In the premise of NIES (16-2 Onogawa, Tsukuba-City, Ibaraki)
  2. Air sampling instrument: High-volume air sampler, with the capability of filling 600 litters of air per minutes.
  3. Filter used: Double filter with the quartz filter and activated carbon filter
  4. Filter analysis instrument: KEK’s High Resolution Ge detector

Measurement result:

Iodine-131 (half-life of 8.02 days), Tellurium-132 (half-life of 3.204 days), and Iodine-132, the daughter nuclide of Tellurium-132 (half-life of 2.295 hours) have detected.

We have conducted detailed nuclide analysis, and nuclide with smaller contribution has detected.

Samples collected after the afternoon of 16 March, shows much lower value at concentrations one hundred times lower. This result indicates no further spread of airborne nuclide on and after the measurement.

Chart1 Result of first measurement: Detected nuclide and its concentration (Bq/cm3)

Measurement period:15 March, 2011 14:39?15 March,2011 17:34
Air collected:105 cubic meter

graph
NuclideCONC.(Bq/cm3)
Iodine1313.0×10-5
Tellurium1322.0×10-5
Caesium1346.7×10-7
Caesium1361.2×10-7
Caesium1376.5×10-7
Tellurium129m8.1×10-7
Iodine1335.6×10-7
Technetium99m3.6×10-8

Due to miscalculation, resutls of the measurement of 15 March sample are revised.
See the 6th report.

Chart2 Result of second measurement: Detected nuclide and its concentration (Bq/cm3)

Measurement period:15 March, 2011 17:48-16 March,2011 8:48
Air collected:540 cubic meter

graph
NuclideCONC.(Bq/cm3)
Iodine1312.1×10-5
Tellurium1324.9×10-6
Caesium1346.6×10-7
Caesium1361.1×10-7
Caesium1376.5×10-7
Tellurium129m1.2×10-6
Iodine1331.3×10-6
Technetium99m*13.7×10-8

Chart3 Result of third measurement: Detected nuclide and its concentration (Bq/cm3)

Measurement period:16 March, 2011 9:08-17:08
Air collected:288 cubic meter

graph
NuclideCONC.(Bq/cm3)
Iodine1313.2×10-5
Tellurium1323.0×10-6
Caesium1345.2×10-7
Caesium1367.9×10-8
Caesium1375.0×10-7
Tellurium129m9.0×10-7
Iodine1333.6×10-7
Technetium99*12.0×10-8

Chart4 Result of forth measurement: Detected nuclide and its concentration (Bq/cm3)

Measurement period:16 March, 2011 17:21-17 March,2011 9:21
Air collected:576 cubic meter

graph
NuclideCONC.(Bq/cm3)
Iodine1312.7×10-7
Tellurium1327.8×10-9
Caesium1342.9×10-9
Caesium136no detection*2
Caesium1372.1×10-9
Tellurium129mno detection
Iodine1336.5×10-9
Technetium99*19.9×10-9

*2 [Correction] Caesium136 was not detected. Previous data 3.9×10-8 was mistakenly described from the old sample. We are sorry for this mistake. (Mar/28 17:00)



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