<p>Tungsten is considered the most promising plasma-facing material for fusion reactors with exceptional performance. Under certain conditions, activated tungsten dust can be generated through plasma–wall interactions and released into the atmosphere. Activated tungsten migrates downward in the soil after atmospheric deposition. However, effective methods for evaluating the environmental dose of gamma rays emitted by activated tungsten are still lacking. Consequently, a method for evaluating the air-absorbed dose rate of activated tungsten dust was proposed considering soil attenuation. Key parameters including the mass attenuation coefficient and energy absorption build-up factor were determined for the main gamma ray energies of radionuclides within the activated tungsten dust. Additionally, air-absorbed dose rates were calculated by assuming that radioactive sources were located at different soil depths and radii. It was found that a soil depth of <InlineEquation ID="IEq1"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="41365_2025_1757_Article_IEq1.gif" Format="GIF" Height="14" Rendition="HTML" Resolution="72" Type="Linedraw" Width="41" /> </InlineMediaObject> <EquationSource Format="TEX">$50\,\hbox {cm}$</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mn>50</mn> <mspace width="0.166667em" /> <mtext>cm</mtext> </mrow> </math></EquationSource> </InlineEquation> significantly attenuated the environmental dose by 99.9%, whereas the air-absorbed dose rates within the horizontal distance of <InlineEquation ID="IEq2"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="41365_2025_1757_Article_IEq2.gif" Format="GIF" Height="14" Rendition="HTML" Resolution="72" Type="Linedraw" Width="49" /> </InlineMediaObject> <EquationSource Format="TEX">$500\,\hbox {cm}$</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mn>500</mn> <mspace width="0.166667em" /> <mtext>cm</mtext> </mrow> </math></EquationSource> </InlineEquation> accounted for 91% of the total dose rate. Therefore, this study underscored the importance of soil attenuation in environmental dose assessments, which must be carefully re-examined for the safety analysis of fusion reactors.</p>

Methodology for estimating external radiation dose exposed to deposited activated tungsten dust in the soil

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发表日期：

2025年6月29日

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Feng-Die Wang,
Bao-Jie Nie,
Yu-Xuan Wang,
De-Yi Chen,
De-Zhong Wang

摘要

Tungsten is considered the most promising plasma-facing material for fusion reactors with exceptional performance. Under certain conditions, activated tungsten dust can be generated through plasma–wall interactions and released into the atmosphere. Activated tungsten migrates downward in the soil after atmospheric deposition. However, effective methods for evaluating the environmental dose of gamma rays emitted by activated tungsten are still lacking. Consequently, a method for evaluating the air-absorbed dose rate of activated tungsten dust was proposed considering soil attenuation. Key parameters including the mass attenuation coefficient and energy absorption build-up factor were determined for the main gamma ray energies of radionuclides within the activated tungsten dust. Additionally, air-absorbed dose rates were calculated by assuming that radioactive sources were located at different soil depths and radii. It was found that a soil depth of $50\,\hbox {cm}$ $50 cm$ significantly attenuated the environmental dose by 99.9%, whereas the air-absorbed dose rates within the horizontal distance of $500\,\hbox {cm}$ $500 cm$ accounted for 91% of the total dose rate. Therefore, this study underscored the importance of soil attenuation in environmental dose assessments, which must be carefully re-examined for the safety analysis of fusion reactors.