**2.2. Tritium and other radionuclides**

### *2.2.1. Tritium*

The main feeders, contributing to the radioactive pollution of the Yenisei, are majorly the right bank feeders, situated near MCC outlet: river Kan, on the bank of which the electrochemical plant (ECP, Zelenogorsk city) is situated, and river Bolshaya Tel', flowing along the border of

According to data, presented in the monograph [9], the most of the region's waters, related to the bottomland of Kan, contain from 0.04 to 3 µg/l of uranium that is considered as highly pure with respect to natural radionuclide content. In addition, there was no trend in uranium content from the location of selection. Only in one place at the turn of Kan's course to the north vs. course of Bogunay river, it was revealed that all of the waters contain uranium from 1 to 3.3 µg/l. Industrial waters discharged by ECP into Kan near the plant administration were

Natural stream feeding Syrgyl river contained from 0.03–0.07 to 1.0–7.3 µg/l of uranium. The contents in the range 0.3–5.0 µg/l were shown to be natural geochemical background of uranium in the studied region, in particular, in the bottomland of Kan. All of the excesses are

The analysis data [1–12] shows that the geochemical background level of uranium in the Yenisei River is in agreement with the mean statistical level for the basins with major contribution of natural uranium resources, e.g. Baikal Lake and rivers of Altai region: from 0.15 to

Uranium content in waters which were collected from Bol'shaya Tel' in the September 2007 at the 1000 m place from the estuary is 3–60 times higher than values obtained for uranium (mean value 0.33 ± 0.08 µg/l) in background samples (Yenisei, tideway). Moreover, this period was indicated by significantly higher uranium concentrations as compared with other studied months. This increase becomes remarkable for the 1000 m place, where uranium concentration is 16 µg/l that is very close to the accepted in Canada and Australia standards for the minimal allowed uranium concentration—20 µg/l and by 8 times exceeds accepted by WHO standard—2 µg/l. Despite that obtained values are lower than the level of exposure (LE = 75 µg/l) accepted by in NRS of Russian Federation [9, 10], uranium concentration in some places of Bol'shaya Tel' in September is, in general, can be considered as abnormal. It is known that natural uranium is a mixture of three isotopes: 238U—99.2739%

 years). In contrast to other isotope pairs, last two isotopes are in constant proportion, regardless of high migration activity of uranium and geography: 238U/235U = 137.88 [13, 14]. The presence of uranium was truly established in the waters of Bol'shaya Tel', it can only be originated artificially: in the sample from 1000 m (October 2006) ~0.05 ng/l and in the sample from Bol'shaya Tel' (March 2007) ~0.03 ng/l. In addition, the ratio of 236U/234U at these places

Besides, water samples obtained in September provided information about anion content of NO3

in the waters of Bol'shaya Tel' (1000 m from estuary). It is considered that the presence of such anions can indicate the non-equilibrium conditions in basin solution. Such situation is considered rather usual for liquid radioactive wastes, where acetate and nitrate, due to kinetic limitations of the acetate oxidation by nitrate, can coexist even at high (about 100°C) temperatures [10].

(~2 mg/l, while the maximum permissible concentration (MPC) is 45 mg/l), CH3

years) and 234U—0.0057% (T1/2 = 2.455

COO<sup>−</sup>

−

(~7 mg/l)

similar to natural uranium content and contained 0.05–0.08 µg/l of uranium.

years), 235U—0.7024% (T1/2 = 7.038 × 108

testing area 'Sverniy' MCC (Zheleznogorsk city).

considered as abnormal.

less than 2.0 µg/l.

364 Water Quality

(T1/2 = 4.468 × 109

is 1:0.8, respectively.

× 105

Besides artificial radionuclides, Yenisei water was also polluted high tritium content. To prove this, the tritium content was determined in the picked water samples. Results are given in **Figure 3**.

Tritium content in the picking site '0 km' exceeds by 15–20 times the background tritium content obtained via long-term monitoring and typical for Yenisei (4 ± 2 Bk/l) [15–20].

To prove industrial origin of tritium in water samples it is recommended to control content of gamma-emitting radionuclides. There is significant amount of artificial radionuclides in the studied water.

### *2.2.2. Radionuclides without tritium*

Depending on the state of radionuclides that can be present as simple ions to molecules and hydrolyzed forms, colloids and pseudocoolloids, organic and inorganic particles [21, 22] and, respectively, migrates over long distances and be sorbed by ecosystem immediately near the discharge area. Content of TUE in surface basins is extremely low and equals 10−10–10−15 M, within limits of the most sensitive spectral techniques, e.g. mass-spectrometry [23, 24]. For the precise determination of TUE contents as well others radionuclides such as 90Sr in water systems, the most frequently used methods are hybrid ones, combining preliminary concentrating and separating of radioisotopes with various detecting methods, e.g. alpha-, beta- and gamma-spectrometry [25–27].

**Figure 3.** Average tritium content in water samples of Yenisei (distance down the stream from places of water discharge by MCC).

To increase the number of identified radionuclides, the method for concentrating the radionuclide from Yenisei water samples has been introduced [8]. Data obtained after concentration of water samples is given in **Tables 1** and **2**.

Water samples contain the bunch of artificial radionuclides. To increase the number of identified radionuclides, the method for concentrating the radionuclide from Yenisei water samples has been improved [8].

The method for concentrating the radionuclide was accepted on the basis of two widely known methods of co-precipitation with oxyhydroxide of Fe (III) and Mn (IV) oxide [28, 29].

Artificial radionuclides, which have different origin, have been found in water samples: induced (activated) radionuclides—24Na, 46Sc, 51Cr, 54Mn, 59Fe, 60Co, 65Zn, 76As and others; satellite radionuclides—99Mo, 124Sb, 131I, 133I, 141Ce, 144Ce and others. The most distinctive are trans-uranic radionuclides—239Np, isotopes of Pu. In water samples, taken down the stream from MCC (5 km), besides the decreasing concentration of artificial radionuclides there were found some natural radionuclides: 210Pb and 232Th. There were included the presence of longliving satellite isotope 152Eu (T1/2 = 13.6 years) ~ 0.04–0.06 Bk/l and the presence of short-living activated radionuclide 58Co (T1/2 = 71.3 days) ~ 0.03–0.07 Bk/l in water samples.
