October 25, 2011
Implementation of Radioactive Nuclide Analysis of
Deposits Collected by City of Yokohama and Soil around
the Points where the Deposits were Collected
MEXT will conduct radioactive nuclide analysis of the deposits collected by the City of Yokohama
and the soil around the points where the deposits were collected.
1. Objective of the survey
MEXT will conduct radioactive nuclide analysis regarding deposits for which the City of
Yokohama had conducted an analysis of radioactive strontium (see the Attachment), and the soil
around the points where the deposits were collected.
2. Details of the survey
○ Entity for conducting nuclide analysis: Japan Chemical Analysis Center
○ Samples to be analyzed:
Deposits for which the City of Yokohama had conducted an analysis of radioactive
strontium (two samples) and the soil collected at the surface layer (at the depth of 5 cm) of
the points where said deposits were collected (two samples)
○ Targets:
(i) Concentration per unit weight of Cs-134 and Cs-137 [Bq/kg]
(ii) Concentration per unit weight of Sr-89 and Sr-90 [Bq/kg]
○ Analysis methods
(i) Radioactive cesium: Germanium semiconductor detectors
(ii) Radioactive strontium: Low background beta-ray counters
○ Analysis period: Around three weeks
Emergency Operation Center
Horita, Oku
Tel : 03-5253-4111 Ex.4604, 4605
Attachment
Press Release by City of Yokohama
October 14, 2011
Yokohama Disaster Countermeasures Headquarters
Radiation Countermeasures Division
Results of the Measurements of Strontium Contained in Deposits
at So-called Micro Spots
The City of Yokohama has confirmed so-called micro spots, where high radiation doses are detected
locally, based on information provided by citizens, and has conducted measurements and decontamination,
etc. at such spots. Strontium was detected in samples collected by citizens who provided the information.
Therefore, the City of Yokohama asked the Isotope Research Institute to conduct an examination of
strontium and cesium for confirmation. The results thereof and measures to be taken in the future are
reported as follows.
1. Results of the measurement of strontium
Measurement of strontium was conducted for the same samples of deposits collected at Okurayama in
Kohoku ward and near Shin-Yokohama, for which nuclide analysis was conducted and the results were
publicized on September 17.
No.
Sampling point
Results of nuclide
analysis of the total
of Sr-89 and Sr-90
(against Cs-137)*
Results of cesium analysis
(Bq/kg)
Total
1
2
(Near a civil engineering
office)
Deposits collected around a
street inlet in a road gully
(Near Shin-Yokohama)
Deposits collected from the
bottom of a fountain (not
working) within a road area
Cs-137
Cs-134
129 Bq/kg
(0.60 %)
39,012
21,385
17,627
59Bq/kg
(0.35 %)
31,570
17,008
14,562
* The results of the survey by MEXT (released on September 30) show that the ratio of Sr-90 against Cs-137
was 0.016 to 5.8 %. In the current examination, Sr-89 and Sr-90 could not be separated, so the results show
total measurement values of Sr-89 and Sr-90.
2. Our response on the day
As the existence of strontium was confirmed, we held a meeting of the Radiation Countermeasures
Division of Yokohama Disaster Countermeasures Headquarters, and confirmed the following.
(i) We will provide the results of the measurements and other information to the national
government (MEXT, etc.).
(ii) We will request the national government to expand the scope area of surveying strontium, etc.,
where it has been conducting within a 100 km-radius from TEPCO’s Fukushima Dai-ichi NPP, to
include the City of Yokohama.
3. Measures to be taken by the City of Yokohama in the future
(i) We will continue measures for micro spots.
(ii) We will provide information properly to relieve the anxiety of citizens.
Contact point
John Robert Car Kuramochi, Division Chief, Health Safety Division, Health and Social Welfare Bureau
Tel. 671-2468