Research and Development Relating to the Accident at the TEPCO's Fukushima Daiichi NPS

1-4

How Far Did Radionuclides Diffuse from the Accident?
=Measurement of Atmospheric Anthropogenic Radionuclides Using the CTBT IMS Network=

109

Activity Concentration (ǴBq/m3)

108

All

Cs-137

I-131

Te-132

107
106
105
104
103
102
101

Fiji (Nadi)

Malaysia (Kuala Lumpur)

Papua New Guinea (New Ireland)

Cameroon (Douala)

Mexico (Guerrero Negro)

Panama (Panama City)

Kiribati (Kiritimati)

France (Pointe-a-Pitre, Guadeloupe)

Philippines (Tanay)

France (Kourou, French Guiana)

Kuwait (Kuwait City)

Germany (Schauinsland, Freiburg)

Russia (Zalesovo)

Mauritania (Nouakchott)Sweden (Stockholm)

Portugal (Ponta Delgada, Azores)

U.S.A. (Ashland, KS)

Mongolia (Ulaanbaatar)

Iceland (Reykjavik)

Norway (Spitsbergen)

Japan (Okinawa)

Canada (St. John's, N.L.)

U.S.A. (Upi, Guam)

Russia (Kirov)

U.S.A. (Wake Island)

Russia (Dubna)

Russia (Ussuriyk)

Canada (Vancouver, B.C.)

U.S.A. (Charlottesville, VA)

Russia (Petropavlovsk-Kamchatskkiy)

Canada (Yellowknife, N.W.T.)

U.S.A. (Salchaket, AK)

U.S.A. (Midway Islands)

Canada (Resolute, NU)

U.S.A. (Sacramento, CA)

U.S.A. (Oahu, HI)

U.S.A. (Melbourne, FL)

Japan (Takasaki)

U.S.A. (Sand Point, AK)100

Fig.1-9 Comparison of the integral activity concentration of particulate radionuclides detected at each IMS station
Data for each station is presented in descending order of activity concentration for all radionuclides. It can be seen that the activity
concentration has a tendency to be high in North America, Russia, and Japan and low in equatorial regions and the SouthernHemisphere.

The Comprehensive Nuclear-Test-Ban Treaty (CTBT) bans
all nuclear explosions. Although it has not been in effect yet,the International Monitoring System (IMS) is underconstruction around the world and approximately 80% of thesystem is provisionally operated in order to monitor nucleartests. The IMS network consists of 337 monitoring stations,
including 80 radionuclide (RN) stations. In Japan, we havealready built IMS RN stations for the continuous monitoringin Takasaki, Gunma and Onnason, Okinawa.
The accident at the TEPCO s Fukushima Daiichi NPS (1F)in March 2011 emitted copious amounts of anthropogenic
RNs into the environment. The RNs emitted into the ambient
air were detected by the IMS RN stations. Part of theradioactive plume containing particulate RNs derived fromthe accident diffused eastward owing to westerly winds andbegan to be detected at the IMS stations one after another on
the North American and Eurasian Continents. Eventually,
the particulate RNs were detected at 39 out of 63 operating

stations: all stations in the Northern Hemisphere and twostations in the Southern Hemisphere. Fig.1-9 shows acomparison of the integral activity concentration of threemajor RNs and all of the anthropogenic RNs found at eachstation from the detection start date to September 30, 2011,
when the detection subsided. Although the integral activity
concentration itself means nothing, it is used as a guide todetermine any tendencies in the spread of RNs among theIMS stations.
As mentioned above, the network of IMS RN stations
illustrates the global extent of the RN contamination in not
only the Northern Hemisphere but also a part of the SouthernHemisphere. Therefore, in addition to its primary role, theIMS network contributed greatly to the measurement of theanthropogenic RNs released from the accident at 1F.
The present study was sponsored by the Japan Institute ofInternational Affairs (JIIA).

Reference
Yonezawa, C., Yamamoto, Y., Measurement of Anthropogenic Radionuclides in the Atmosphere with a Radionuclide Monitoring Network for Nuclear
Tests, Bunseki, vol.2011, no.8, 2011, p.451-458 (in Japanese).
JAEA R&D Review 201215