Radionuclides detected at the CTBT radionuclide observatory station in Takasaki (as of 30, May 2011)

Radionuclides detected at the CTBT radionuclide observatory station in Takasaki (as of 30, May 2011)

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1. The readings of air trapped from March 12 to 14 at the Takasaki Observatory were analyzed by the CTBTO Secretariat. The results showed several particulate radionuclides normally undetected; namely, cesium (Cs) -134, 136 and 137, iodine (I) -131 ~ 133, lanthanum (La) -140, tellurium (Te) -129, 129m, 132, and technetium (Tc)-99m, were detected at very high concentrations.
These radionuclides are thought to have originated from the Fukushima Daiichi nuclear power plant disaster, but it is not certain that they were contained in the air trapped from March 12 to 14. They may have come flying during the measuring operation (the 15th and later) to contaminate the detector and its surroundings. Therefore, the observed radionuclides are qualitatively correct, but the concentrations may not be accurate.

2. As for the analysis of measurements of air trapped after March 15 at the Takasaki Observatory, in addition to radionuclides detected above, barium (Ba) -140 was detected. Activity concentrations of these radionuclides showed a first peak on March 15-16, a second on March 20-21, and a third on 29-30. Peaks are occasionally detected thereafter. Weather conditions such as wind and rainfall are believed to have influenced the second peak and thereafter.

3. The Takasaki Observatory also measures radionuclides in the form of noble gases. Since March 15, xenon(Xe)-133 was detected with its peak on the 21st. This also is believed to have come from the Fukushima nuclear power plant. As gases much denser than normal have penetrated into the detection devece, accurate concentrations can not be measured. This is why we indicated only the estimate figures. (Refer to Appendix for the transition of radionuclide particulate and noble gases.)

(Notes)
Figures for March 14-15 are missing, because the detectors stopped due to the "planned power cut" in the Takasaki region on March 16.

High figures of the particulate radionuclides on March 20-21 seem due to the rain effects.
The peak on March 29-30 may have been due to the dust raised by relatively strong wind, but it is difficult to determin the cause. Also the peak of radioactive xenon on March 21 seems to be highly affected by the rain that day.

The Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO) is an international organization that will be established upon the entry into force of the Comprehensive Nuclear-Test-Ban Treaty, a Convention that outlaws nuclear test explosions. Its seat will be Vienna, Austria. The organization will be tasked with verifying the ban on nuclear tests and will operate therefore a worldwide monitoring system and may conduct on site inspections. The Preparatory Commission for the CTBTO, and its Provisional Technical Secretariat, were established in 1997 and are headquartered in Vienna, Austria. (Wikipedia)