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

Benjamin Zorko,Matjaž Korun,Boštjan Črnič,Branko Vodenik,Sandi Gobec

doi:10.2478/aiht-2021-72-3475

Benjamin Zorko, Matjaž Korun + Show 3 more

Open Access

https://doi.org/10.2478/aiht-2021-72-3475

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Abstract

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.

Highlights

Ambient dose equivalent H*(10) is measured to assess general population exposure to ionising radiation
Articles 35 and 36 of the EURATOM treaty (1) require from the European Union (EU) member states to monitor continuously the levels of environmental radioactivity, which is carried out in line with the Safety Standards Series No RS-G-1.8 issued by the International Atomic Energy Agency (IAEA) (2)
Our findings suggest that the contribution of cosmic rays to annual ambient dose equivalent can be identified through solar activity

Summary

Introduction

Ambient dose equivalent H*(10) is measured to assess general population exposure to ionising radiation. Articles 35 and 36 of the EURATOM treaty (1) require from the European Union (EU) member states to monitor continuously the levels of environmental radioactivity, which is carried out in line with the Safety Standards Series No RS-G-1.8 issued by the International Atomic Energy Agency (IAEA) (2) These include networks of thermoluminescence (TL) dosimeters measuring the ambient dose equivalent H*(10) of external ionising radiation around nuclear facilities to provide radiation safety information for workers and nearby population (3). They can cover a larger territory to provide environmental radiation exposure information for the general public (4, 5). The dosimeters are mainly exposed to ionising radiation from secondary cosmic rays (9), which are generated in the stratosphere and the upper troposphere by primary cosmic

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