Influence of solar activity on ambient dose equivalent H*(10) measured with thermoluminescent dosimeters in Slovenia

Ambient dose equivalent H*(10) is measured to assess general population exposure to ionising radiation. From its spatial and time variations it is possible to identify sources of exposure. In Slovenia, semi-annual H*(10) is measured routinely with thermoluminescence dosimeters at 66 locations around the Nuclear Power Plant (NPP) Krško and at 50 other locations covering the rest of Slovenian territory. Since the Chernobyl accident contamination had ceased to contribute to ambient dose equivalents, we have been calculating correlation coefficients between annual mean number of sunspots and annual H*(10). These correlation coefficients were calculated for five locations in western Slovenia and for five annual H*(10) extracted from measurements around NPP Krško. Their ranges between –0.64 and –0.38 suggest a clear negative correlation between solar activity and H*(10). Mean annual H*(10) averted by solar activity in the past two solar maxima reached 0.070 mSv around NPP Krško (155 m.a.s.l.) and 0.132 mSv and 0.180 mSv at Kredarica (2515 m.a.s.l.). Quantifying the influence of the solar activity on the ambient dose equivalent helps us to better understand exposure of the general population to ionising radiation.
Okoljski dozni ekvivalent H*(10) merimo, da ocenimo izpostavljenost populacije ionizirajočemu sevanju. Iz časovne in prostorske odvisnosti je mogoče ugotoviti vire izpostavljenosti. Polletne dozne ekvivalente H*(10) merimo rutinsko s termoluminiscenčmimi dozimetri na 66 lokacijah v okolici Jedrske elektrarne Krško (NEK) in na 50 drugih lokacijah na teritoriju Slovenije. Ker kontaminacija zaradi Černobilske nesreče ne prispeva več k okoljskemu doznemu ekvivalentu smo izračunali korelacijske koeficiente med povprečnim letnim številom sončnih peg in letnim H*(10). Korelacijske koeficiente smo izračunali za pet lokacij v Zahodni Sloveniji in pet lokacij v bližini NEK. Vrednosti korelacijskih koeficientov so v intervalu od -0.64 do -0.38, kar kaže na močno korelacijo med sončno aktivnostjo in H*(10). Zaradi sončeve aktivnosti so bili povprečni letni H*(10) v zadnjih dveh sončnih maksimumih zmanjšani za 0.070 mSv v okolici NEK (na nadmorski višini 155 m) in za 0.132 mSv in 0.180 mSv na Kredarici (na nadmorski višini 2515 m). Ovrednotenje vpliva sončeve aktivnosti na okoljski dozni ekvivalent boljša razumevanje izpostavljenosti populacije ionizirajočemu sevanju.