ENVIRONMENTAL MONITORING OF THE MAIN NUCLEAR SITES OF (NORTH-WEST )

M. Magnoni(*), L. Porzio(**), S. Bertino(*), M.C. Losana(*), R. Olivetti(**), F. Righino(*)

(*) ARPA Piemonte – Polo Radiazioni Ionizzanti, Dipartimento di Via Jervis, 30 – 10015 Ivrea (TO), Italy (**) ARPA Piemonte – Area Agenti Fisici, Dipartimento di , Italy

INTRODUCTION In this paper are described the monitoring activities of ARPA Piemonte, principally focused on one of the two major Italian nuclear sites located in Piemonte: Nuclear Site of that, together with the Nuclear Power Plant of Vercellese (272 MWe) are the most important nuclear installations of the Region. Both these sites are located in Po Plain and are quite close together (not more than 20 km). Moreover their discharges flow directly into the Po river (Nuclear Power Plant) or into the Dora Baltea, one of the most important Po affluent, a few kilometres prior to the confluence into Po river. In spite of the fact that the Italian nuclear program stopped in 1987 after the referendum following the Chernobyl accident (1986), a new interest in this subject was now due the imminent start of the decommissioning programs, scheduled for the next years. For that reason, in these years, great efforts were devoted to the study of the radionuclides contents in both the rivers, in “normal” conditions and also during the authorised discharge of the nuclear installations. In this work the results of the monitoring program performed are presented as a contribution to the definition of the “point zero situation” for the environmental pollution before the start of the decommissioning programs. In fact the Italian nuclear program leaves a considerably legacy to Piemonte Region, an administrative district in North West Italy. During the last century, in this Region were constructed one of the four Italian Nuclear Power Plant and many other nuclear facilities, most of which located at the Saluggia Nuclear Site, not far from Trino Vercellese. The Nuclear Power Plant of Trino Vercellese that has been operating from 1965 to 1987 after the referendum that stopped the national nuclear program, was shut down and, in 1995, was put in a surveillance condition, before the start of the decommissioning program. In the Nuclear Site of Saluggia, the main nuclear installations are: the Avogadro storage site, a former experimental nuclear reactor, containing now some irradiated fuel rods and the ENEA- EUREX, an experimentally fuel reprocessing Plant that has been operating during the seventies and that still contains a large quantity of highly radioactive liquid wastes and Sorin, a radiopharmaceutical factory. In this case, the main problem is the solidification of the liquid wastes before the final storage in a Nuclear Repository Site. The location of these sites can be considered quite closed together (not more than 20 km): for that reason the area around these sites, can be considered a potentially critical area and ARPA decided to start a monitoring program of the environment, with a special emphasis of the ecosystem of the rivers Dora Baltea and Po. THE ARPA MONITORING PROGRAM The major part of the ARPA radioactivity monitoring program was performed around the Saluggia Site. An increasing interest on radioactivity monitoring around the Saluggia Site was especially grown after the flood of October 2000, that interested a large part of . In particular, some nuclear facilities at the Saluggia Sites were partially inundated by the overflowing of Canale Farini, an irrigation canal from Dora Baltea river. The monitoring program designed by ARPA Piemonte involves both environmental and alimentary matrices. In particular we have gathered food samples, such as vegetables, drinking water and milk, from the area around the Saluggia Site. However the major part of the samples gathered were environmental ones, such as: groundwater, sediment and water of the rivers (Dora Baltea and Po) and SMOD (Sedimentable Mineral Organic Detritus of Dora Baltea and Po). The sampling program started in November 2000 and ended approximately six months later. The sites of sampling are reported on the map (see Figure 10).

MATERIAL AND METHODS After collection, the samples were carried to the laboratories for the radioactivity measurements. All samples were counted with hyperpure Germanium detectors (relative efficiency 30-40%, FWHM 1.8 keV at 1.3 MeV) in order to obtain detailed information on the presence of artificial gamma emitters. For same samples, more complicated radiochemical analytical techniques were used, in order to detect pure and emitters (Sr-90 and Plutonium respectively).

RESULTS AND DISCUSSION The points where the samples were gathered are shown and numbered on detail on the map (Figure 10). We have water samples from Dora Baltea river (points 9 and 14), a drinking water sample (the town of Saluggia, point 12), some groundwater samples (points 10, 11, 20 , 21 and 22), soil samples (points 1,2,3,4,5,6,7 and 8), one mud sample (point 19), some SMOD samples (points 15,16,17 and 18), two sediment samples (points 23 and 24) and fresh milk and vegetables samples (point 13). Because the concentration of artificial radionuclides in drinking water and vegetables samples was always found under the Minimum Detectable Activity (MDA), threshold of the instruments, their results are not reported below. For all the other matrices, the results that we have obtained have been summarised in a graphical form. The water samples of Dora Baltea river (see Figure 1) were collected after the flood (October 2000) and about four months later. The trace of Cs-137 detected in the sample collected in November 2000, can be attributed to the environmental background mainly due to the Chernobyl accident. In fact, the sample of March 2001, collected near the discharge point of EUREX Plant (point 9 in the map), gave a results under the instrumental MDA. In Figures 2 and 3 are shown the results for groundwater samples. In each sample collected at Benne (Figure 2 and point 10 in the map) a little concentration of Co-60 was found (a few mBq/l), probably due to a well known radiological accident that occurred at Sorin in 1986, when some powder coming from a damaged Co-60 source was spread into the environment. The traces of Cs-137 are negligible and can be attributed to the Chernobyl accident. The other groundwater samples were collected in three piezometers, near the EUREX Plant (points 20, 21 and 22 in the map). In Figure 3 we have reported the averages value for the three piezometers. The sample collected the 8th of November, immediately after the flood, has a Cs-137 concentration quite greater than those collected in the past. By contrast, the following samples show a lower Cs-137 concentrations, comparable to usual background levels and attributable to the Chernobyl accident. Therefore it seems probable that a little radioactivity leakage took place immediately after the flood. Many soil samples were collected all around the sites and measured. We have reported in Figure 4 the average results of all the 8 sampling site. The values found for Cs-137 are those typical for Po Plain, mainly related to the Chernobyl fallout, while the small traces of Co-60 measured in one sample is probably due to the Sorin radiological accident above mentioned. For mud samples (see Figure 5), collected at point 19 on the map, low levels of Cs-134 and Cs-137 were measured but the values are compatible with the Chernobyl derived pollution. The SMOD samples were collected in Dora Baltea and in Po rivers. We can notice (see Figure 6) that the values of all radionuclides of “Dora Baltea south” (referred to samples collected below the liquid waste discharge point of EUREX Plant, number 16 on the map) are greater than those of “Dora Baltea north” (referred to samples collected above the discharge of the Plant, point 15 on the map); this holds, in particular, for Pu239/240 and Sr-90. This seems to indicate a contribution due to the discharge of the EUREX Plant. Nevertheless, these little radioactivity increments pose a no significant radiological risk. A confirmation of a direct contribution of EUREX Plant to the radioactivity levels in the Dora Baltea river is shown by the data referring to another SMOD sampling experiment, performed during the Eurex Plant discharge. The SMOD values, shown in Figure 7, are referred to point 16 (“Dora south”), 17 (“Dora Brusasco”) and 18 (“Po ”). The discharge of the EUREX ponds occurred on Thursday, May 17 2001 at 4 PM and lasted for about 12 hours; the Dora Baltea flow was 172 m3/s and the SMOD samplers were left in the river for one week, from Thursday morning. The discharge contribution can be clearly identified by the detection of Am-241 (1.21 Bq/kg) at point “Dora south”. In fact, this radionuclide was not detectable in the previous analysis (see Figure 6) and was significantly present in the liquid waste discharged. This was the unique Am-241 detection in SMOD for Dora Baltea river. Also the Cs-137 value at point “Dora south” is greater than that at “Dora Brusasco”, but in this case the discharge contribution is uncertain. The small values of I-131 detected in the Po river are probably due to hospitals liquid waste discharges. The sediment analysis are shown in Figure 8. The samples were collected at points 23 and 24 on the map. The highest concentration of Co-60 in the sample collected at the most southern point of the nuclear area (point 23) is due to the Sorin accident occurred in 1986. The highest concentration of Cs-137 and the presence of Sr-90 and Am-241 in traces (1.17 Bq/kg) in the sample collected near the EUREX Plant discharge (point 24) IS due to the Plant discharge itself. However the radiological relevance of these values is negligible. In fresh milk samples collected in a farm near the plants (point 13 on the map) Cs-137 was measured (see Figure 9), but the values are comparable to the averages of the whole zone, including also samples collected above the plant discharges. So Cs-137 concentration can be attributed to Chernobyl accident. DORA BALTEA WATER

0,00250

0,00200

0,00150 Bq/l 134 Cs 137 Cs 60 Co 0,00100

0,00050

0,00000

10-nov-00 16-mar-01 Sampling date

Figure 1 – Cs-134, Cs-137 and Co-60 activity concentrations in water samples of Dora Baltea river. The 16-mar-01 sample was collected at point 9 on the map. GROUNDWATER AT BENNE

0,0060

0,0050

0,0040

Bq/l 0,0030 134 Cs 137 Cs 60 Co 0,0020

0,0010 60 Co

0,0000 137 Cs

03-nov-00 134 Cs 06-dic-00 24-gen-01 Sampling date 07-mar-01 Figure 2 – Cs-134, Cs-137 and Co-60 activity concentrations in groundwater collected at Benne site (point 10 on the map). GROUNDWATER EUREX PIEZOMETERS

0,1600

0,1400

0,1200

0,1000

Bq/l 0,0800 134 Cs 137 Cs 60 Co 0,0600

0,0400

60 Co 0,0200 137 Cs 0,0000

08-nov-00 134 Cs 07-dic-00 20-feb-01 sampling date

Figure 3 – Cs-134, Cs-137 and Co-60 activity concentrations in groundwater of Eurex Plant piezometers (point 20, 21 and 22 on the map).

SOIL

120.00

100.00 Co-60 Cs-134 Bq 80.00 /k Cs-137 g dr 60.00 y 40.00

20.00

0.00 12345678 Sampling points

Figure 4 – Cs-134, Cs-137 and Co-60 in soil samples. The samples number correspond to the points on the map. MUD

25,00

20,00

15,00 Bq/l 134 Cs 137 Cs 60 Co 10,00

5,00

0,00

1 2 Sampling date Figure 5 – Cs-134, Cs-137 and Co-60 activity concentrations in mud samples collected at point 19 on the map. SMOD

12

10

8 Dora Baltea north Bq/kg Dora Baltea south 6

4

2

0 Cs-137 Cs-134 Co-60 I-131 Sr-90 Pu-239 Pu-238

Figure 6 – Activity concentrations of different artificial radionuclides in SMOD samples of Dora Baltea river. “Dora Baltea north” samples were collected at point 15 on the map, “Dora Baltea south” ones at point 16. SMOD DURING EUREX DISCHARGE

12.00

10.00

8.00

Dora south Bq/kg 6.00 Dora Brusasco Po Crescentino 4.00

2.00

Po Crescentino 0.00 Dora Brusasco Cs-137 Cs-134 Dora south Co-60 I-131 Am-241

Figure 7 – Activity concentrations of different artificial radionuclides in SMOD samples collected during Eurex Plant discharge. “Dora south” samples were collected at point 16, “Dora Brusasco” ones at point 17 and “Po Crescentino” ones at point 18 on the map.

SEDIMENT

30.00

25.00

20.00

134 Cs Bq/Kg 15.00 137 Cs 60 Co 90 Sr 10.00 241 Am

5.00

0.00

0 -0 v 1 o 0 -n - 9 r 2 a -m 6 1 sampling date

Figure 8 – Activity concentrations of different artificial radionuclides in sediment samples, collected in the most southern point of the area (point 23 on the map) and near the point of liquid waste discharge of Eurex Plant (point 24 on the map). FARM FRESH MILK

0,40

0,35

0,30

0,25 Bq/l 0,20

0,15

0,10

0,05

90 Sr 0,00 134 Cs 23-nov-00 13-dic-00 137 Cs 24-gen-01 60 Co 07-mar-01

Sampling date

Figure 9 – Activity concentrations of different radionuclides in fresh milk samples collected in a farm near the nuclear sites (point 13 on the map).

CONCLUSIONS The monitoring program allowed the assessment of the radioactivity levels in the most relevant environmental and alimentary matrices. In a few cases the activity concentrations of some radionuclides (Am-241, Cs-137, Pu-239/240 and Sr-90 in SMOD samples from Dora Baltea river) showed a significant contribution due to the nuclear installations of the Saluggia Site (mainly related to the EUREX Plant). However, the radiological impact of these data is negligible.