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Systematic and continuous monitoring 14C activity in atmospheric CO2 and biological samples in the vicinity of the Krško Nuclear Power Plant (NEK) in Slovenia has been performed since 2006. The aim of the monitoring was to determine 14C distribution in a close vicinity of the power plant and to estimate a possible contribution of NEK to the effective dose to the local population through food chain. This paper describes a model of food origins developed for the purpose of estimating the effective dose from ingestion of 14C via local food. Some other approaches of diet estimation are also discussed. The slightly increased 14C specific activity in plants very close to NEK could not change significantly the effective dose to the local population due to ingestion of 14C when compared to the effective dose from the ingestion of natural 14C. Sustavni monitoring specifične aktivnosti 14C u atmosferskom CO2 i u biološkim uzorcima iz neposredne okolice Nuklearne elektrane Krško (NEK) u Sloveniji provodi se od 2006. godine. Cilj monitoringa je odrediti prostornu raspodjelu specifične aktivnosti 14C u neposrednoj okolici NEK-a, te njenu ovisnost o razdobljima promjene goriva koja se obavlja svakih 18 mjeseci. Na osnovu izmjerenih specifičnih aktivnosti 14C može se procijeniti doprinos NEK-a efektivnoj dozi koju lokalno stanovništvo primi zbog konzumacije (ingestije) hrane porijeklom iz okolice NEK-a. Budući da je ugljik, pa time i 14C, sastavni dio sve hrane, nije potrebno poznavati detaljne prehrambene navike lokalnog stanovništva. Međutim, potrebno je poznavati ili procijeniti udio hrane iz okolice NEK-a u ukupnoj prehrani. U ovom radu opisano je nekoliko scenarija za porijeklo hrane, počevši od vrlo konzervativnog i malo vjerojatnog scenarija konzumacije samo hrane iz neposredne okolice NEK-a do realističnijeg (iako još uvijek konzervativnog) scenarija od 17 % hrane iz okolice NEK-a, a ostalih 83 % s kontrolne točke na kojoj nije opažen utjecaj 14C iz NEK-a. Malo povišenje specifične aktivnosti 14C u biljkama iz neposredne okolice NEK-a, koje je opaženo tijekom monitoringa, ne utječe značajno na procjenu efektivne doze zbog ingestije 14C, jer je razlika u odnosu na efektivnu dozu zbog ingestije "prirodnog" 14C usporediva ili manja od prirodnih varijacija.

Sustavno praćenje aktivnosti 14C atmosferskog CO2 i bioloških uzoraka (voće – uglavnom jabuke, povrće, žitarice, kukuruz) u neposrednoj okolici Nuklearne elektrane Krško (NEK) provodi se od 2006. godine s ciljem procjene mogućeg utjecaja NEK-a na razinu aktivnosti 14C u okolišu te na efektivnu dozu koju primi lokalno stanovništvo putem prehrane. Posebna je pozornost posvećena praćenju utjecaja remonta elektrane, koji se provodi svakih 18 mjeseci, na aktivnost 14C u okolišu. U radu će se pokazati značajke aktivnosti 14C u okolišu elektrane i neki zaključci zasnovani na dugogodišnjem iskustvu monitoringa. Atmosferski CO2 sakuplja se na dvije lokacije unutar kruga NEK-a, obično u dvomjesečnim intervalima te u kraćim intervalima tijekom i neposredno nakon remonta. Biološki materijal koji integrira 14C iz atmosfere tijekom relativno kratkog vegetacijskog razdoblja (plodovi jabuke, kukuruz, žitarice i slično) skuplja se na početku vegetacijskog razdoblja (lipanj ili srpanj) te ujesen (prije berbe, rujan ili listopad) na više lokacija u unutarnjem i vanjskom krugu. Referentni uzorci bilja sakupljaju se na kontrolnoj točki kraj Dobove, 11, 2 km (zračna udaljenost) jugoistočno od NEK-a, na kojoj se ne očekuje utjecaj zračnih ispusta iz NEK-a. Praćenje aktivnosti 14C u okolici NEK u razdoblju od 2006. do kraja 2016. godine pokazuje da je utjecaj 14C ispuštenog u okoliš zračnim putem mjerljiv i u atmosferskom CO2 i u biljkama koje koriste CO2 za fotosintezu. Taj je utjecaj kratkoročan i prostorno ograničen na najbližu okolinu. Uočena je korelacija između ukupno ispuštene aktivnosti A14C i izmjerenih vrijednosti a14C u CO2 i u bilju. Systematic and continuous monitoring 14C activity in atmospheric CO2 and biological samples (mostly apples, vegetable, cereals, corn) in the vicinity of the Nuclear Power Plant Krško (NEK) in Slovenia has been performed since 2006. The aim of the monitoring is to determine 14C distribution in a close vicinity of the power plant and to estimate possible contribution of NEK to the effective dose of the local population through food chain. In this paper we describe some characteristics of the 14C distribution in the environment of NEK. The 14C activity of atmospheric CO2 at two locations inside the NEK area is on the average slightly higher than that in Zagreb. It depends on the 14C activity (A14C) released in air-born effluent. The influence of the 14C releases has been observed also in plants. Higher 14C activity in plants is most pronounced shortly after spring refuelling, when plants use atmospheric CO2 that contains 14C released from NEK. The influence of the released air-born 14C activity is measurable in both atmospheric CO2 and in plants; the higher the activity of gaseous effluent, the higher the atmospheric and plant 14C activity. However, the influence is temporally and spatially limited. Average 14C activity in plants at the control location Dobova does not differ from the average atmospheric 14C activity in Zagreb. It was shown earlier that the slightly increased 14C activity in plants does not contribute significantly to the effective dose of the local population due to ingestion of 14C. According to the experience of the whole monitoring, 14C is the only released radionuclide detected in the environment of NEK (Report IJS-DP-12059).

In this presentation we will summarize the 10-year-long experience in monitoring 14C activity in the close vicinity of the Krško Nuclear Power Plant (NPP) in Slovenia. Atmospheric CO2 samples have been taken in 2-month periods during the regular operation of the power plant, or in shorter periods during refuelling periods. Biological samples (apples, corn, wheat, grass, vegetables) have been samples twice a year (in summer and autumn) in two circles around the NPP, inner and outer, and at the control point 12 km from the plant. The aim of the monitoring was to estimating a possible influence of the NPP on environmental 14C levels and on the effective dose of local population through food chain. Increase of 14C activity in atmospheric CO2 was observed during and immediately after the refuelling of the power plant, performed every 18 months. Good correlation between the total 14C activity released in gaseous effluents and the 14C activity of the atmospheric CO2 has been observed. 14C activity in plants collected close to the Krško NPP is always higher than the activities on the control point, and depends both on the distance from the exhaust of the plant ventilation system and on wind direction: it is higher on the location in the SW-NE direction that coincided with the most pronounced wind directions. Higher 14C activities have been determined in plants collected in summer after the spring refuelling than in those collected during the following vegetation period after the autumn refuelling. This can be explained by the uptake of the CO2 of higher 14C activity for the process of photosynthesis after spring refuelling. To estimate the realistic effective dose due to ingestion to the population in the vicinity, a model of food consumption has been proposed. The calculated dose for the population at the NPP vicinity is not significantly different from the dose for the population at the control point.

14C activity in the atmospheric CO2 and in biological samples in the close vicinity of the Krško Nuclear Power Plant (NPP) in Slovenia has been regularly monitored since 2006 with the aim of estimating a possible influence of the NPP on environmental 14C levels and on the effective dose of local population through food chain. Atmospheric CO2 on two locations was collected every two months, or in shorter periods during some refuelling periods. Biological samples (apples, corn, wheat, grass, vegetables) were collected twice a year (in summer and autumn) in two circles around the NPP, inner and outer, and at the control point 12 km from the plant. Increase of 14C activity in atmospheric CO2 was observed during and immediately after the refuelling of the power plant, performed every 18 months. Good correlation between the total 14C activity released in gaseous effluents and the 14C activity of the atmospheric CO2 has been observed. 14C activity in plants collected close to the Krško NPP is always higher than the activities on the control point, and depends both on the distance from the exhaust of the plant ventilation system and on wind direction: it is higher on the location in the SW-NE direction that coincided with the most pronounced wind directions. Higher 14C activities have been determined in plants collected in summer after the spring refuelling than in those collected during the following vegetation period after the autumn refuelling. This can be explained by the uptake of the CO2 of higher 14C activity for the process of photosynthesis after spring refuelling. To estimate the realistic effective dose due to ingestion to the population in the vicinity, a model of food consumption has been proposed. The calculated dose for the population at the NPP vicinity is not significantly different from the dose for the population at the control point.

14C activity in the atmospheric CO2 and in biological samples in the close vicinity of the Krško Nuclear Power Plant (NPP) in Slovenia has been regularly monitored since 2006 with the aim of estimating a possible influence of the NPP on environmental 14C levels and on the effective dose of local population through food chain. Atmospheric CO2 on two locations was collected every two months, or in shorter periods during some refuelling periods. Biological samples (apples, corn, wheat, grass, vegetables) were collected twice a year (in summer and autumn) in two circles around the NPP, inner and outer, and at the control point 12 km from the plant. Increase of 14C activity in atmospheric CO2 was observed during and immediately after the refuelling of the power plant, performed every 18 months. Good correlation between the total 14C activity released in gaseous effluents and the 14C activity of the atmospheric CO2 has been observed. 14C activity in plants collected close to the Krško NPP is always higher than the activities on the control point, and depends both on the distance from the exhaust of the plant ventilation system and on wind direction: it is higher on the location in the SW-NE direction that coincided with the most pronounced wind directions. Higher 14C activities have been determined in plants collected in summer after the spring refuelling than in those collected during the following vegetation period after the autumn refuelling. This can be explained by the uptake of the CO2 of higher 14C activity for the process of photosynthesis after spring refuelling. To estimate the realistic effective dose due to ingestion to the population in the vicinity, a model of food consumption has been proposed. The calculated dose for the population at the NPP vicinity is not significantly different from the dose for the population at the control point.