1. Radioactive pollution of food chain - Α Air - soil pathways of radioactive pollution Source Inhalation ( External radiation ) Direct pollution Food Air Soil Plants Animals MAN Pollution of – and from water sources

2. Radioactive pollution of food chain - Β Fresh and marine water pathways of radioactive pollution Pollution source Direct pollution Food Air Plants Fish Lakes, Sea Soil Soil pathways to man MAN FishRivers Washout, irrigation

3. Environmental monitoring External dose rate Air radioactivity Radioactive deposition Soil radioactivity Radioactivity of waters Radioactivity of food Radioactivity of building materials Specific indicators

4. Environmental monitoring Routine network design principles 1.Optimal selection of sampling and measuring stations with respect to the potential sources of pollution 2.Balance between a source-orientated and population- oriented sampling network 3.Monitoring of all the major pathways of potential propagation of the radioactive pollution 4.Balance between fast availability and quality of the information obtained

5. Environmental monitoring Greece: map of the routine monitoring network Total beta in air On daily basis LLD: 0.3 mBq m -3 Total beta in water Integrated monthly samples LLD: 4 Bq m -3 Radioactive deposition On monthly basis LLD: 0.2 Bq m -2 Food radioactivity On monthly basis or else LLD: 1 - 10 Bq kg -1 External dose rate Every 6 hours + telemetric LLD: 2 nGy h -1 Marine and lake samples Occasionally

6. Environmental monitoring Basic measuring techniques, advantages / disadvantages 1.External dose rate Fast information, telemetry No data on the source nuclides 2.Total beta counting High sensitivity No data on the source nuclides. No telemetry 3.Gamma spectrometry Data on specific radionuclides No telemetry 4.Alpha spectrometry Data on specific radionuclides High sensitivity. No telemetry 5.Radiochemical analysis Data on specific radionuclides High sensitivity. No telemetry

7. Monitoring of external dose rate - Provides fast information, especially in the case of a telemetric network -Allows the detection of reliably low increases of the dose rate -Problems: - No data on the composition of the pollutant - Stability problems with certain types of detectors - Possibility of false alarms A temporary increase of the dose rate, caused by deposition of External dose rate radon daughters washed out by rain The simultaneous measurement of Rainfall rainfall provides additional information

8. Monitoring of external dose rate (2) A telemetric network allows to compare quickly the data from different locations, which help to form a first picture of the pollution propagation and also to avoid false alarms. The background dose rate in each station has to be known with sufficient accuracy, as long as it can vary considerably. In the case of Greece, the background dose rate varies within 30 – 120 nGy h -1.

9. Monitoring of external dose rate (3) In the case of air pollution, the additional dose rate is composed by 2 parts: 1. The part determined by the radionuclides in the air 2. The part determined by the radionuclides deposited in the ground Depending on the deposition conditions, the second part may gradually dominate over the first and determine a significant residual dose rate, even after the end of air contamination. Air radioactivity External dose rate Background Dry deposition Wet deposition

10. Monitoring of air radioactivity A known volume of air is filtered and the filter activity is consequently determined by use of different techniques. It is possible - in principle - to perform real time telemetric measurements. However, the accumulation of decay products of Rn222 and Rn220 contributes unfavorably and reduces significantly the sensitivity. Sample volumes of the order of 50 – 100 m 3 are sufficient to achieve LLD values of the order of 0.2 mBq m -3, in the case of delayed total beta measurement. This ensures the monitoring of the bckg levels, which are of the order of 1 mBq m -3. Much higher sample volumes are necessary in order to detect the background levels of specific artificial radionuclides in air. Series of 24-h sampling are applied typically, to ensure continuous air monitoring. If necessary, the density of sampling can be enhanced. Special filters are used in order to measure gaseous forms of radionuclides in air (e.g. the non-particulate fraction of I131).

11. Monitoring of air radioactivity (2) When using the total beta counting method, a delay of 4-5 days is necessary between the end of sampling and the start of measurement, in order to allow the decay of the Rn222 and Rn220 decay products accumulated on the filter. Note that the concentrations of these natural nuclides in open air are typically within 2 – 3 Bq m-3 or 3 orders of magnitude higher than the total activity of the long-lived background radionuclides. The delay mentioned is not necessary when high-resolution gamma spectrometry is applied instead. Nevertheless, the presence of radon daughters may reduce significantly the accuracy of the measurement. ________ A derived quantity is the integrated air concentration - the time integral of the air concentration during a given period of time. This quantity characterizes the total ‘exposure’ of a given atmosphere to the pollutant(s) and is used as an input value for various environmental and dosimetric models.

12. Ε ΡΓΑΣΤΗΡΙΟ Ρ ΑΔΙΕΝΕΡΓΕΙΑΣ Π ΕΡΙΒΑΛΛΟΝΤΟΣ ΟΡΙΟ ΑΝΙΧΝΕΥΣΗΣ ΚΑΙ ΕΠΙΠΕΔΟ ΕΠΙΦΥΛΑΚΗΣ ΓΙΑ ΤΙΣ ΜΕΤΡΗΣΕΙΣ ΟΛΙΚΗΣ-β ΣΤΟΝ ΑΕΡΑ Monitoring of air radioactivity (3) The reasonably low alarm level of the total beta measurements should ensure low inhalation doses during the period necessary to perform further analyses and consider the application of countermeasures Annual dose limit Alarm level Typical levels Weeks LLD

13. Monitoring of radioactive deposition The radioactive deposition is defined as the activity deposited in unit area of the ground surface (during a given period of time). The monitoring may refer to the total beta deposition, as well as to the deposition of specific radionuclides. This quantity is of primary importance for the prediction of the additional external dose rate due to the soil pollution, as well as the pollution of plants and surface waters and the propagation of the pollutants through various environmental pathways and trophic chains. Due to its integral nature, the radioactive deposition is a more easily detectable quantity than the air concentrations of the radionuclides from which it results. Under given concentrations of radionuclides in air, the radioactive deposition is considerably enhanced during rainfalls. The difference between “dry” and “wet” deposition may depend on the chemical properties of the radioactive materials. Radioactive deposition = Integrated air concentration x Deposition velocity

14. Radioactive deposition Relation between radioactive deposition and rainfall Rainfall, mm Radioactive deposition, kBq m -2

15. Monitoring of radioactive deposition (2) The radioactive deposition is usually sampled by use of collective vessels of known area (typically 0.1 – 1 m 2 ). To avoid re-suspension losses, an layer of distilled water has to be present in the vessel’s bottom. The typical collection duration is 1 month, but shorter collection times may be applied in the case of radiological emergency After the end of collection, the water sample is transferred to the laboratory and mildly evaporated, to avoid loss of volatile components. The activity of the residue is determined by total beta counting or gamma-spectrometry or some radiochemical method. In the case of total beta counting, the LLD is of the order of 0.05 – 0.2 Bq m -2, depending on the area of the collecting vessel and for 1 month sampling duration. In the case of enhanced accidental contamination (deposition values of the order of 1 kBq m -2 or higher), gamma-spectrometry can be easily applied. To determine the current background monthly deposition values of Cs137, vessels of larger area ( 1 m 2 ) have to be used.

16. Monitoring of soil radioactivity Although not included in the group of standard monitoring procedures of the EU, the measurement of soil radioactivity is a useful additional method. It is one of the simplest methods for a detailed post-accidental mapping of the radioactive pollution. In this case, samples of well defined area are collected, in order to enable the expression of results in deposition units as well ( Bq m -2 ). The sampling is done from a layer 0 – 5 or 0 – 10 cm. The samples are homogenized, dried, shifted and analyzed by means of gamma-spectrometry or certain radiochemical procedure. The presence of natural radionuclides restricts the application of this method to the cases of rather significant soil pollution. Depending on the radionuclide, the efficiency of the detector used and the duration of measurement, the LLD may vary within 0.1 – 10 Bq kg -1 which, for a sample size of 10 x 10 x 10 cm, corresponds to deposition values of 10 – 100 Bq m -2. When the measurements aim the determination of radioactive deposition, attention has to be paid to the selection of soil undisturbed since the pollution event. Areas of possible rainwater accumulation have to be excluded as well.

17. Monitoring of soil radioactivity A map of Cs137 deposition after the Chernobyl accident derived on the basis of about 2000 soil measurements performed in Greece by NTUA ( ~ 1500) and ERL ( ~ 500). This type of maps are very useful not only for various model evaluations, but also as background data in the case of any consequent pollution event. Depending on the region, the current concentrations of Cs137 in the surface layer of undisturbed soil in Greece vary within 4 – 1000 Bq kg -1.

18. Monitoring of water radioactivity The monitoring of surface waters is often source-oriented and concerns areas of routine or possible accidental release of specific radioactive liquid materials. In this cases the methodology applied depends on the specific radionuclides of interest. In other cases the monitoring is population-oriented and concerns reservoirs of drinking water and major rivers, supplying these reservoirs. The tap water is also monitored on regular basis, at least that of the largest population centers. The well drinking waters are often controlled for the possible presence of enhanced concentrations of natural radionuclides. The marine water is monitored on regular basis only near points of routine or possible accidental releases. In Greece, where no major nuclear facilities exist, sea water monitoring is regularly performed during the visits of nuclear-powered military vessels.

19. Monitoring of water radioactivity (2) The lake water is usually monitored on a weekly bases, except in regions of routine radioactive releases. The river water should be sampled more often, preferably on daily basis, but composite samples may be measured instead. The total beta measurements are usually applied in the cases of drinking water samples. The samples are mildly evaporated in order to avoid losses of some volatile components. The results of total beta measurements have to be corrected for the presence of K40, to provide the so-called “residual beta-activity” = beta activity – that of K40. In the case of total beta activity exceeding certain level, additional analysis has to be performed for the determination of the radionuclide composition. Underground waters should be analyzed for determination of radon isotopes and other radiologically important natural radionuclides, e.g. Ra226.

20. Chernobyl accident - Greece Average 1st year and 50-year doses through various pathways, μSv Pathway 1st year 50 years Inhalation 22 22 External exposure 52 190 Food - water 420 500 TOTAL 490 710 The radiologically most important food chain pathways Grass pollution with Ι131 > Sheep and goat milk Grass pollution with Cs137>Sheep and goat milk and meat Pollution of fruits and vegetables Animal foodstuff pollution >Meat and milk products, 1986/87 Cereals pollution>Bread and pastry, 1986/87

21. Monitoring of food radioactivity Two basic types of food control are performed during the routine radioactivity monitoring: 1. Deternination of Cs137 and Sr90 in milk. In some cases the milk sampling is location-oriented. In other cases a composite sample of diary milk from different producers, mixed in proportion to their coverage of the market. 2. Deternination of Cs137 and Sr90 in the so-called “mixed diet” sample. The “mixed diet” sample is composed by the most representative food products of a given country, in proportions according to the consumption of the average citizen. Therefore, their constituents and the proportions they are mixed may vary significantly from country to country. In both cases specific radiochemical analysis is applied for determination of Sr90 and Cs137, after proper homogenization of the samples. The determination of Cs137 can be based also on gamma-spectrometry measurements, if the sensitivity of the system is high enough.

22. Monitoring of food radioactivity (2) After the Chernobyl accident (1986) a lot of countries require radioactivity certificates from the exporting countries known to be affected by the resulted radioactive pollution. At the same time, many countries perform a sample or even a regular control of imported foodstuffs, depending on the country of origin. Most of the above controls refer (today) to the concentration of Cs137. If a sertification of the type “Cs137 below 10 Bq kg -1 ” is acceptable (in most cases it is), the analysis is relatively simple and includes sample homogenization and gamma-spectrometry measurement for about 1 h. Sample pre-concentration by low-temperature ashing may be necessary if detection of 1 Bq kg -1 levels is required.

23. Monitoring of building materials The monitoring of building materials is not currently a part of the routine control in most EU countries. Nevertheless, when the existing suggestions regarding the natural radioactivity of building materials will become regulations, this type of monitoring may be included as a standard. Even today, the requests for analyses of building materials (domestic and/or imported) are continuously growing. The concentrations of natural radionuclides in building materials are usually high enough to be easily detected by gamma-spectrometry. The only difficulties refer to the sample preparation (in some cases) and to the application of proper self-absorption corrections. The compliance with future regulations regarding indoor radon may require the determination of radon exhalation rate from the major building materials and/or their components.

25. Interpretation of the results of an environmental monitoring program 1.