4. CHERNOBYL AFFECTED AREAS

4.1. SCOPE

This section presents detailed information on the distribution of radioactivity from the Chernobyl accident, the systems used to monitor the dispersion of the radioactivity, the characteristics of radioactivity in water-borne runoff, the fate of radionuclides in the Dnieper reservoirs and the transboundary movement of radioactivity from Chernobyl affected areas.

The storage and/or disposal by burial of Chernobyl contaminated waste is discussed in Section 7. Section 8 assesses current and future exposure to radiation from Chernobyl affected areas. Section 9 describes the identification and analysis of Chernobyl hot spots.

4.2.DISTRIBUTION OF FALLOUT FROM THE CHERNOBYL ACCIDENT

As a result of the Chernobyl accident, about 85 PBq of 137Cs, 54 PBq of 134Cs, 1760 PBq of 131I, 10 PBq of 90Sr and 0.07 PBq of 239,240Pu were released, as well as many shorter lived radionuclides of lesser radioecological significance [4.1]. Major

releases occurred over a period of ten days, during which time there were a number of changes in wind direction. As a consequence, fallout was deposited over most of Europe; however, the largest areas of contamination were in Belarus, the Russian Federation and Ukraine (see Table 4.1). Much of the fallout in these three countries was deposited in the Dnieper River basin.

After the Chernobyl accident, the responsible agencies in many countries gathered data on soil contamination in their territories. These data were published in the form of reviews, maps and lists of contamination density in populated areas. Much of the data applies to areas within the Dnieper River basin. In 1992–1995 a European Union–Common- wealth of Independent States programme was carried out to study the consequences of the Chernobyl accident [4.2], and within that programme data on soil contamination density were gathered, processed and published as an atlas [4.3], including a CD-ROM version [4.4]. The maps were prepared using the geographic information system ARC/INFO, Version 6.1. The information from participating countries was received in the form of geographically located data for about 400 000 sampling sites selected in 31 European countries,

TABLE 4.1. AREAS IN EUROPE CONTAMINATED BY CHERNOBYL FALLOUT IN 1986 [4.1, 4.4]

		Area with 137Cs deposition density range (km2)
	37–185 kBq/m2	185–555 kBq/m2	555–1480 kBq/m2	>1480 kBq/m2
Russian Federation	49 800	5 700	2100	300
Belarus	29 900	10 200	4200	2200
Ukraine	37 200	3 200	900	600
Sweden	12 000	—	—	—
Finland	11 500	—	—	—
Austria	8 600	—	—	—
Norway	5 200	—	—	—
Bulgaria	4 800	—	—	—
Switzerland	1 300	—	—	—
Greece	1 200	—	—	—
Slovenia	300	—	—	—
Italy	300	—	—	—
Republic of Moldova	60	—	—	—

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Scale 1: 2 500 000

Projection: Lambert Azimuthal

25	0 kilometres						100			200
25	0 miles				50					100
Total caesium-137 (nuclear weapons test, Chernobyl, ...) deposition
kBq/m2	1	2	4	10	20	40	100	185	555	1480
Ci/km2	0.027 0.054		0.1	0.27	0.54	1.08	2.7	5	15	40

© EC/IGCE, Roshydromet (Russia)/Minchernobyl (Ukraine)/Belhydromet (Belarus, 1998)

FIG. 4.1. Distribution of deposited 137Cs in the Russian part of the Dnieper River basin (May 1986) [4.4].

including 19 058, 176 971 and 11 569 sampling points in Belarus, the Russian Federation and Ukraine, respectively.

Figures 4.1–4.3 show 137Cs deposition in the Russian Federation, Belarus and Ukraine areas of the Dnieper River basin based on these sources1. Figure 4.4 is a closer view showing the areas of

greatest 137Cs contamination. Radionuclide fallout was concentrated in the upper Dnieper watershed in Russian and Belarusian territory and in the whole Pripyat watershed. Of the 137Cs deposited in the

1 See Fig. 3.1 for the boundaries of the Dnieper River basin.

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Scale 1: 1 500 000

Projection: Lambert Azimuthal

25	0 kilometres	50	100
25	0 miles		50

Total caesium-137 (nuclear weapons test, Chernobyl, ...) deposition

kBq/m2	1	2	4	10	20	40	100	185	555 1480
Ci/km2	0.027	0.054	0.1	0.27	0.54	1.08	2.7	5	15	40

© EC/IGCE, Roshydromet (Russia)/Minchernobyl (Ukraine)/Belhydromet (Belarus, 1998)

FIG. 4.2. Distribution of deposited 137Cs in the Belarusian part of the Dnieper River basin (May 1986) [4.4].

Scale 1: 2 500 000

Projection: Lambert Azimuthal

25	0 kilometres						100			200
25	0 miles					50				100
Total caesium-137 (nuclear weapons test, Chernobyl, ...) deposition
kBq/m2	1	2	4	10	20	40	100	185	555	1480
Ci/km2	0.027	0.054	0.1	0.27	0.54	1.08	2.7	5	15	40

© EC/IGCE, Roshydromet (Russia)/Minchernobyl (Ukraine)/Belhydromet (Belarus, 1998)

FIG. 4.3. Distribution of deposited 137Cs in the Ukrainian part of the Dnieper River basin (May 1986) [4.4].

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FIG. 4.4. Distribution of deposited 137Cs in the most contaminated areas of the Dnieper River basin (December 1989)[4.1].

Dnieper River basin, approximately 30% was in the CEZ (see Fig. 4.5), 30% in the far zone of the Belarusian and Ukrainian sections of the Pripyat River basin and about 40% in the basins of the Sozh and Iput Rivers, in the so called Gomel and Bryansk–Tula hot spots. Table 4.2 shows data on contamination levels in the administrative regions of Belarus, the Russian Federation and Ukraine within the Dnieper River basin.

More detailed information on these three countries is contained in the atlas of the radioactive contamination of the European part of the Russian Federation, Belarus and Ukraine [4.5]. The maps were generated from the databases and electronic maps of the hydrometeorological service organizations of the three countries.

There are also maps and databases of the radionuclide deposition density in specific regions contaminated following the Chernobyl accident. Less data are available for radionuclides other than 137Cs because they are not as easily measured and because they were deposited closer to their source,

FIG. 4.5. Distribution of 137Cs within the CEZ, 1986 [4.1].

due to their lower volatility under the accident conditions.

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TABLE 4.2. AREAS (THOUSANDS OF km2) WITH ELEVATED CAESIUM-137 DEPOSITION IN THE REGIONS WITHIN THE DNIEPER RIVER BASIN (AS OF 1993–1995)

		Caesium-137 soil deposition (MBq/m2)
	0.04–0.2	0.2–0.6	0.6–1.5	>1.5	Total >0.04
		Belarus
Gomel	16.9	6.7	2.8	1.6	28.0
Minsk	2.0	0.05	—	—	2.1
Mogilev	5.5	2.9	1.5	0.5	10.4
Subtotal	24.4	9.7	4.2	2.1	40.4
		Russian Federation
Bryansk	6.7	2.7	1.9	0.3	11.6
Kaluga	3.4	1.4	—	—	4.8
Kursk	1.4	—	—	—	1.4
Smolensk	0.08	—	—	—	0.08
Subtotal	11.6	4.1	1.9	0.3	17.9
		Ukraine
Cherkassy	3.2	0.07	—	—	3.3
Chernihiv	2.2	0.14	—	—	2.3
Dnipropetrovsk	0.04	—	–	—	0.04
Kiev	7.7	1.0	0.6	0.4	9.7
Nikolaev	0.02	—	—	—	0.02
Rovno	0.2	—	—	—	0.2
Zhytomyr	9.2	1.8	0.3	0.15	11.5
Subtotal		3.0	0.9	0.6	27.1
Total	58.6	16.8	7.0	3.0	85.4

Figure 4.6 shows the distribution of deposited 90Sr; of the 90Sr deposited in the Dnieper River basin, about 70% was deposited on the catchments and floodplain areas of the CEZ within Belarus and Ukraine, and the remainder was deposited in the far catchment areas of the basin. The Russian part of the Dnieper River basin received less than 10% of the 90Sr inventory of the Dnieper River basin as a whole. This explains the importance of the CEZ as a source of 90Sr contamination. Plutonium, which was associated with fuel particles that became airborne, was even more localized (see Fig. 4.7). The only areas with plutonium levels exceeding 4 kBq/m2 are located within the CEZ.

A significant portion of the point type data on soil contamination density in the Dnieper River basin obtained by organizations within Belarus, the

Russian Federation and Ukraine from 1986 to the present day was entered into the databases of subprojects of Project 2, Radioecology, of the French–German Chernobyl Initiative [4.6]. The database contains several thousand determinations of 137Cs and 90Sr densities on agricultural land; data on contamination density, speciation and vertical distribution of 137Cs and 90Sr in soils on the catchments of the rivers flowing in the Dnieper River basin; and data on 137Cs and 90Sr soil contamination density in population centres. As part of these projects a series of electronic maps was generated for the six most contaminated regions of Belarus, the Russian Federation and Ukraine (Gomel, Mogilev, Bryansk, Kaluga, Kiev and Zhytomyr regions), including maps of 137Cs contamination density.

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