River (up to 5 kBq/kg) as a result of uncontrolled discharge of this radionuclide. In 2000 a significant level of 60Co was measured in soil on the Don River bank near the mouth of the wastewater discharge pipeline of the nuclear power plant (dose rate up to 30 μSv/h). Thus the failure to detect the leak quickly made it impossible to contain it within a localized area. The above example shows that the system of monitoring leaks of radioactive substances to natural waters from nuclear power plant sites needs to be improved.

5.5.2.Ukraine

In the vicinity of the operating Ukrainian nuclear power plants, environmental monitoring is organized as follows:

(a)At the facilities of nuclear power plants and within the 10 km zone, the safety and environmental departments of nuclear power plants monitor releases. The following are monitored: releases from ventilation stacks, air and soil at nuclear power plant sites and in their vicinity, waste water discharge and water intake points, cooling ponds and underground waters.

(b)Within the 30 km zones around nuclear power plants and the zones of potential impact, monitoring is carried out by units of the Hydrometeorological Service of Ukraine and Gossanepidnadzor.

(c)Sampling near water intakes and other water supply facilities and estimation of radioactive contamination levels is the responsibility of Gosvodkhoz. In addition to Gosvodkhoz, surface and underground waters are monitored by other entities, as prescribed by agency protocols and rules. The system for monitoring groundwater contamination levels in Ukraine is described in Ref. [5.8].

5.5.3.Belarus

There are no nuclear power plants in Belarus, but the 100 km zones of four nuclear power plants (Chernobyl, Ignalina, Rovno and Smolensk) in the neighbouring countries extend into the territory of the republic. The RCREM and its network units carry out radiation monitoring in the nuclear power plant impact zones in Belarus. The radiation dose rate is monitored continuously, and radioactive contamination of the air and atmospheric fallout is

monitored on a regular basis. The monitoring of surface waters and bottom sediments is conducted, however, only on Lake Drisvyaty in the zone influenced by the Ignalina nuclear power plant.

5.6.RELEASES FROM NUCLEAR REACTORS IN THE DNIEPER RIVER BASIN

5.6.1.Releases from the Kursk and Smolensk nuclear power plants

Gaseous and aerosol releases at the Kursk and Smolensk nuclear power plants are discharged through ventilation stacks with a height of 150 m and through small stacks with a height of 60 m. The gases are detained for a certain time prior to release, to allow for decay of short lived radionuclides, and are then partially cleaned of radioactive aerosols and radio-iodine.

During the whole period of operation of the Smolensk and Kursk nuclear power plants, the permissible rate of radionuclide releases into the atmosphere both of groups of and individual radionuclides as prescribed by the Sanitary Rules on Design and Operation of Nuclear Power Plants (SPAES-68 and SPAES-79) have not been exceeded [5.1, 5.7, 5.9–5.12]. Actual releases have been much lower than the requirements of SPAES-88.

In the latest revision of the Sanitary Rules (SPAES-99), the permissible releases into the atmosphere were further reduced. Table 5.3 compares the actual and permissible releases for the Kursk and Smolensk nuclear power plants for the period 1995–2000. The releases were greatest for the inert radioactive gases (isotopes of xenon, krypton and argon), but well below the permissible limits in all cases.

Discharge of radionuclides from nuclear power plants into surface water occurs via the following wastewaters:

(a)Excess (debalanced) water;

(b)Cooling water from the heat exchange equipment in the reactor compartment;

(c)Industrial and shower sewage water;

(d)Special laundry and shower room water;

(e)Utility sewage water.

During the first years of nuclear power plant operation, the release of radionuclides was attributable mainly to debalanced waters and, thereafter,

cooling water and industrial and shower sewage water [5.12]. A typical radionuclide composition of these waters for nuclear power plants of the RBMK type is presented in Table 5.4.

Deviations from the above norms were not observed at the Kursk or Smolensk nuclear power plants. The permissible and actual releases of radionuclides into surface waters during 1998–2000 are presented in Table 4.5. The actual releases are lower than the permissible releases by several orders of magnitude.

5.6.2.Radioactive contamination in the vicinities of the Kursk and Smolensk nuclear power plants

5.6.2.1. Soil

Before the Chernobyl accident, the level of soil contamination in the central regions of the European part of the USSR was, on average, 137Cs = 3.0 kBq/m2 and 90Sr = 1.9 kBq/m2. The density of 137Cs contamination in the soil in the vicinity of the Kursk and Smolensk nuclear power plants was determined by the global background, and it was practically the same as in the reference regions (see Table 5.6).

After 1986 the level of soil contamination with 137Cs in the vicinity of the Smolensk and Kursk nuclear power plants was determined mainly by fallout from Chernobyl (see Section 3). To the north-east of Smolensk, the density of fallout was 18.5–37 kBq/m2 (0.5–1 Ci/km2); in other areas the levels reached 37–74 kBq/m2 (1–2 Ci/km2). In the south-west direction, the densities of contamination were lower than 18.5 kBq/m2 (0.5 Ci/km2).

The Kursk nuclear power plant is located in territory with a general level of contamination of 7.4–18.5 kBq/m2 (0.2–0.5 Ci/km2); at a distance of about 10 km to the south-west there is a spot with a higher concentration, viz. 18.5–37 kBq/m2 (0.5–1 Ci/ km2). According to the assessment in Ref. [5.14], during 16 years of operation of the Kursk nuclear power plant, 0.2 Bq/m2 of 90Sr and 0.8 Bq/m2 of 137Cs

were deposited in the area of Kurchatov town. This is three to four orders of magnitude lower than the level of contamination as a result of global releases.

It is not possible to discern any statistically significant contribution from releases of the Smolensk and Kursk nuclear power plants into the soil [5.12, 5.14, 5.15]. Firstly, the necessary information on the initial contamination of the regions is absent or insufficiently complete and qualitative. Secondly, the contribution of the nuclear power plants is negligibly low.

5.6.2.2. Air

During the whole period of their operation, gaseous and aerosol releases from the Kursk and Smolensk nuclear power plants did not lead to any

significant contamination of the air; they were lower than the effective norms. In 1983–1985 the content of 137Cs in the area of the Smolensk nuclear power plant was (1–4) × 10–6 Bq/m3. After the Chernobyl accident it significantly increased, and in 1988–1989 was tens of mBq/m3 [5.15]. In 2000 the maximum concentration of 137Cs in the area of the Smolensk nuclear power plant equalled 3 × 10–5 Bq/m3. At a distance of 35 km from the nuclear power plant it was approximately the same as at the plant site.

In the vicinity of the Kursk nuclear power plant the content of 137Cs in the air increased by 104 times during 1986 and reached (2–4) × 10–4 Bq/m3 [5.14]. In 2000 at the Kursk nuclear power plant site the mean annual content of 137Cs in the air equalled 8 × 10–5 Bq/m3 [5.7]. Releases from the Kursk nuclear power plant were proposed as an explanation for a small increase in the airborne concentration of 137Cs in Kursk city compared with the average over the whole of the Russian Federation [5.11]; however, this may be a result of contamination from the Chernobyl releases.

5.6.2.3. Natural water

The concentrations of radionuclides in the surface waters of the Bryansk region may be used to assess the pre-Chernobyl concentrations in rivers in the territories of the Kursk and Smolensk regions, namely 14–20 mBq/L for 90Sr, 4–8 Bq/L for tritium and 0.2–1.3 mBq/L for 137Cs [5.17]. Before 1986 the content of radionuclides in the surface waters in the area of the Smolensk nuclear power plant did not exceed these ranges. In 1983–1985 the concentrations in this area were 0.4–1.2 mBq/L 137Cs and 1.5– 5.6 Bq/L tritium [5.15]. The median value of 137Cs activity in the water of the Smolensk cooling pond during the operational period up until the beginning of the 1990s, excluding 1986, was 0.7 mBq/L [5.18].

Concentrations of 137Cs are a little higher in the Smolensk cooling pond and in the Seim and Reut Rivers in the area of the power plant (see Table 5.7). In 1986 they increased 2.5–3 times, but in 1988 they were back to the pre-Chernobyl level [5.18].

At present, the concentrations of 137Cs in the surface waters in the vicinity of nuclear power plants remain at low levels that do not require intervention, although they are a little higher than the pre-Chernobyl concentrations caused by global releases. In 1999 the activity of 137Cs in the Desna River and the Desnogorsk reservoir was 13 mBq/L [5.11] and in the Seim and Reut Rivers up to 20 mBq/L (see Table 5.8).

Since there were no significant releases of 90Sr from the Chernobyl nuclear power plant in the areas of the Kursk and Smolensk plants, its present concentrations in surface waters are approximately the same as before 1986.

Thus the operation of the Kursk and Smolensk plants has not led to significant releases of radionuclides into the environment. The influence of nuclear power plants on the radioactive contamination of soil, air and natural water becomes apparent mainly at certain times in a few samples, where trace quantities of radionuclides of reactor origin, such as 51Cr, 54Mn and 58,60Co, are detected. The only detectable influence of the nuclear power plants on the radioactive contamination of the environment is apparently a small increase (compared with the global level) in the 137Cs concentration in surface waters in the vicinity of the Kursk nuclear power plant.

5.6.3.Releases from Ukrainian nuclear power plants

Release of radioactivity from nuclear power plants can occur via either the air or water pathway.

aISS: interim storage site.

bWK: wastewater treatment works, Kurchatov.

After cleaning, ventilation air is released to the atmosphere via tall stacks. Gaseous and aerosol releases may also enter the atmosphere via ejectors when there is a leak of coolant from the primary to the secondary circuit. In the turbine condenser, separation of non-condensable gases takes place, which then are exhausted by the ejectors. The gases are exhausted into the outlet canal of the circulating water and then into the cooling ponds.

The permissible release of radioactivity to the environment is determined for each nuclear power plant taking account of the stack height, average meteorological conditions at the site and location of the sanitary and protective zones. Table 5.9 shows these permissible releases for Ukrainian nuclear power plants. Before 2000, ischarges from all nuclear

power plants were below the requirements set out in standard SPAS-88.

In 1997 new radiation safety regulations were introduced (NRBU-97) based on the Basic Safety Standards [5.19] and the recommendations of the IAEA. Under these regulations, the permissible release is calculated on the basis of a dose quotient that takes account of all exposure routes to a critical group of the population. For nuclear power plants, the dose limit is 40 mSv/a, which represents 4% of the allowable dose to the general population from all sources (1 mSv/a).

In addition to the permissible limits, more restrictive control levels for releases to air and water are set following discussions with the State Sanitary Supervisory Agency.

The main releases of radioactivity to water occur via primary circuit leaks, blowdown of cooling water systems, drainage from active areas, spent fuel pond operations, decontamination and maintenance operations, and drains from washrooms, showers, etc. Table 5.10 shows the radionuclide releases from all Ukrainian nuclear power plants for the five years from 1997.

Tables 5.11–5.13 show releases to the cooling ponds. In all cases the release rates are only a small

fraction of the maximum permissible releases or the control level.

Tables 5.14 and 5.15 show the concentrations of the key radionuclides, 137Cs and 90Sr, in the ponds and receiving waters of Ukrainian nuclear power plants. These data demonstrate that, at least under post-Chernobyl conditions, it is impossible to distinguish the influence of nuclear power plant releases. Actual releases are significantly lower than permissible releases.