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Airborne gamma-survey after the Chernobyl accident. 1986.

Measurements of atmospheric noble radioactive gases (Kr, Xe).

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Construction materials radiation characteristics data base.

Multi-detector low-background gamma-spectrometer.

 

RADIOACTIVE CONTAMINATION OF THE TERRITORIES OF SEMIPALATINSK TEST SITE INVESTIGATION (1989-1990)

In 1990-1991 the specialists from Laboratory of Environmental Radioactivity (MEPhI) took part in the joined Semipalatinsk Test Site (STS) territories radioactive contamination investigations. The Laboratory task was to conduct the airborne survey of the territories of interest to construct the artificial and natural nuclide activity maps. The results obtained were displayed in the corresponding reports and some of these results were published. The airborne survey results extract of the article by Dubasov Y.V., Krivokhatskiy A.S., Filonov N.P., Kharitonov K.V. "Radiation conditions beyond the bounds of Semipalatinsk nuclear test site" published in "The Atomic Energy Bulletin N.9 1993. Moscow" is adduced here. You may find full text of this article here (263 KB).


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In 1990-1992 the radiation contamination investigation of the Semipalatisk Test Site surrounding territories was conducted by means of ground-based and airborne equipment. The following parameters were measured: dose rate, ground surface and vegetation radionuclide contamination, 137Cs and 90Sr concentration in water, the radioactive atmospheric aerosol and indoors radon concentrations. A great amount of investigations was accomplished in the villages (Dolon, Kaynar, Sarzhal, Caraaul, Mostic, Mayskoe, Egendibulac and Chagan) near the test site borders. More than 30000 km2 of the territories of interest were surveyed by airborne and ground-based equipment (see scheme below).

Surveyed territories scheme

The detailed measurements were carried out in Dolon, Mostic, Kaynar, Sarzhal and Caraaul villages. Being disposed 100-200 km far from the surface nuclear tests these villages were more than the others influenced by radioactive fallouts...

...The airborne survey of the villages and test surrounding territories was conducted by two organization:
    - Laboratory of Environmental Radioactivity of Moscow Engineering Physics Institute
    - Comprehensive Airborne survey expedition of "Aerogeologiya"
by means of their equipment and methods. The MEPhI data are half as many "Aerogeologiya" data. That is because the contamination values are not far from the equipment sensitivity and different survey methods were used: the villages were the territories of interest for MEPhI and the rather big territory including the villages was the zone of interest for "Aerogeologiya".

The ground-based survey of the villages was conducted by the Khlopin Radium Institute and Ministry of Defense specialists. The detailed in-situ dose rate measurements were conducted. The ground, water and vegetation samples were measured later in laboratory conditions.

The results obtained are presented in Tables 1-2. The MEPhI airborne survey results are in good agreement with ground-based survey data.

Table 1

137Cs surface activity according to airborne survey

Village

Distance from STS, km

137Cs surface activity, Ci/km2

by MEPhI

by "Aerogeologiya"

Kaynar

130

0,07-0,1

0,3

Sarzhal

110

0,12-0,14

0,3

Caraaul

200

0,09-0,12

0,2

Egendibulac

115

0,05-0,07

-


Table 2

Surface activity according to in-situ and laboratory measurements, Ci/km2

Village

Dose rate, mR/h

137Cs surface activity

90Sr surface activity

239+240Pu surface activity

Dolon

21/10

0,29/0,02

(0,012)

0,3/0,014

(0,05)

0,3/0,001

(0,093)

Kaynar

20/13

0,3/0,03

(0,12)

0,14/0,02

(0,05)

0,028/0,0006

(0,01)

Sarzhal

20/13

0,3/0,05

(0,12)

0,26/0,04

(0,07)

0,1/0,0003

(0,028)

Caraaul

18/10

0,37/0,008

(0,08)

0,19/0,02

(0,06)

0,032/0,0006

(0,009)

Mostic

18/12

0,13/0,02

(0,06)

0,06/0,02

(0,04)

0,082/0,0006

(0,022)

* Numerators - maximum value, denominators - minimum value, in brackets - averaged values.

...>>

As far as the extract adduced above is concerned we are to say the following.
First. The 137Cs contamination values of the villages (Table 1) were identified by means of Ge detector based airborne gamma-spectrometer.
Second. The MEPhI specialists presented the 137Cs contamination values of the villages as D, where and D are the value and its uncertainty. For unknown reasons the MEPhI data were somewhat uncorrectly transformed.
Third. We regard the explanation of 2-2.5 times discrepancy between ground-based survey and "Aerogeologiya" results being a highly debated one.

Below are shown some airborne artificial nuclide activity maps for the territories surveyed. These results were not included in the paper quoted. Nevertheless we suppose them being very interesting to gain the idea of the territories surveyed contamination and to demonstrate the MEPhI designed airborne technologies.

Cs-137 distribution at 1004-object
137Cs spatial distribution at 1004 object
(artificial lake on Chagan river), Ci/km2.

Co-60 distribution at 1004-object
60Co spatial distribution at 1004 object
(artificial lake on Chagan river), Ci/km2.

Cs-137 distribution at some object
137Cs spatial distribution
at some test place, Ci/km2.

Cs-137 distribution at Caraaul village
137Cs spatial distribution at Caraaul village, Ci/km2.

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