The importance of ichthyofauna of radioactively-contaminated reservoirs from the point of view of radiation safety provision

FIGURE 4-14.VIEWS AROUND THE DIFFERENT PERSPECTIVES INVOLVED WHEN CONSIDERING RADIOACTIVE WASTE. However, the radioactive waste cannot be made to disappear and the case of Asse mine

demonstrates that decisions must be made on where and how retrieved wastes will be disposed of.

In order to avaoid any short-term need for decision the political wisdom is therefore that stakeholders have to be involved for reaching the best solution.

In summary it was concluded that the Asse II mine was and remains an interesting example of the views of society toward radioactive waste. It demonstrates the power of emotions and the limits of radiation protection. It is an outstanding example of ‘security theatre’ with respect to radioactive waste and demonstrates the meaninglessness of radiation protection principles in politics.

Nevertheless, radiation protection experts should accept their role with modesty but trust in the power of scientific truths.

4.9 The importance of ichthyofauna of radioactively-contaminated reservoirs

FIGURE 4-15.LOCATION OF SAMPLING STATIONS ON THE TECHA AND MIASS RIVERS.

Concentrations of radionuclides such as Sr-90 in fish tissues were compared against those from previous studies carried out in the 1960’s. The results of the recent study for Sr-90 were similar to those from the past study, but differences were noted for Cs-137, with higher activity

concentrations being measured in fish sampled in 2015 as compared with 1969.

Differences have been observed in the concentration of both Sr-90 and Cs-137 in spring and autumn. The differences are more or less notable depending on the sampling station (Figure 4-16).

It is thought that the differences observed relate to differences in dissolution of radionuclides in spring and summer.

FIGURE 4-16.CONCENTRATION OF ANTHROPOGENIC RADIONUCLIDES IN TECHA RIVER WATER IN SPRING AND AUTUMN AT DIFFERENT SAMPLING STATIONS (FROM SHISHKINA ET AL.,2016).

Internal hydroxyapatite-based EPR detectors were used in fish from the reservoir to verify internal exposure doses calculated using the ERICA assessment tool with the assumption of uniform distribution of radionuclides throughout the body of the fish. The results were very close to each other and the conclusion drawn that ERICA is an effective tool for evaluating internal exposure dose.

The total dose rate to fish in different reservoirs, calculated using the ERICA tool is variable (Figure

rates to fish at different stations in the Techa River are detailed in Table 4-4. The highest doses (150 µGy/d) occur in the sampling station closest to Mayak. Doses then decreased with distance down the river. The three species (perch, pike and roach) were found in each of the three reservoirs associated with the Techa River. However, one reservoir is a source of drinking water for the local population and fish were placed there artificially. The third reservoir (R3) is small and no pike are present.

FIGURE 4-17.TOTAL DOSE RATE FOR ROACH IN MAYAK RESERVOIRS (* NO FISH PRESENT IN THE RESERVOIR).

The three species (perch, pike and roach) were found in each of the three reservoirs associated with the Techa River. However, one reservoir is a source of drinking water for the local population and fish were placed there artificially. The third reservoir (R3) is small and no pike are present.

TABLE 4-4.INTERNAL,EXTERNAL AND TOTAL DOSE RATES FOR FISH INHABITING THE TECHA RIVER

.

The species composition of fish in the Techa and Miass rivers was similar and no differences in the age structure of roach populations was detected. A difference in the age structure of perch and pike populations was observed with fewer older fish being present in the Miass River, but this is due to fishing being permitted within this river.

A range of bioindicator tests have been performed on fish. No difference was observed in body weight, but a statistically significant difference was observed for the DNA comet assay for erythrocytes from fish sampled from the upper Techa River. The frequency of roach erythrocytes with micronuclei was also significantly increased in fish from the Techa River. Peripheral blood cell number was also linked to dose rate with a threshold level being observed; a temporary reduction in peripheral cell number was observed at a dose rate of 70 µGy/d. The results suggest that radiation leads to an increase in blood cell reactions in fish.

Another detriment observed in sampled fish was the presence of trypanosome parasites. The prevalence of parasites was increased in fish exposed to higher dose rates in the Techa River.

Differences have also been observed in relation to the active sperm content in fish and in antioxidant levels with higher levels being observed in fish experiencing greater dose rates.

Transplant studies have also been undertaken with fish from both the Techa and Miass rivers being transplanted in cages to the Zyuzelga River. Fish from the Miass River were similarly transplanted in the Techa River. The experiment is summarized in Figure 4-18.

FIGURE 4-18.EXPERIMENTAL PLAN FOR THE TRANSPLANTATION OF FISH FROM THE TECHA AND MIASS RIVERS (UP) AND LOCATION OF IN SITU EXPERIMENTAL SITES (DOWN).

Fish transplanted from contaminated to clean river water were found to have an increase in peripheral blood cell number. Similar results were observed for fish transported from contaminated to clean reservoirs.

The radionuclide intake for the local population from the consumption of fish from the Techa River has also been investigated. Fishing is not permitted in the river, but does occur. If fish were to be

consumed from the mid reaches of the river, the intake of Sr-90 would be higher than the allowable dose. Fish consumption could give rise to an effective dose of up to 0.5 mSv.

From the experiments conducted, it has been concluded that chronic dose rates of more than 100 µGy/d leads to genotoxic effects in fish and changes in physiological and pathophysiological reactions, as well as changes in the response to other factors. Adaptive reactions in fish allow the survival of populations of perch, roach, pike, tench, carp and ide at chronic exposures up to 18 mGy/day.

4.10 Determining limit parameters of radionuclides in soil for producing