This work by Leung Tsun Kin of the Department Applied Physics, The Hong Kong Polytechnic University is licensed under a Creative Commons Attribution- NonCommercial-ShareAlike.

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Presentation transcript:

This work by Leung Tsun Kin of the Department Applied Physics, The Hong Kong Polytechnic University is licensed under a Creative Commons Attribution- NonCommercial-ShareAlike 3.0 Hong Kong License To view a copy of this license, visit Commons Attribution- NonCommercial-ShareAlike 3.0 Hong Kong Licensehttp://creativecommons.org/licenses/by-nc-sa/3.0/hk/deed.en_HK Understanding common nuclear radiation units used in mass media ( 如何解讀新聞報導中常見的核幅射單位 ) Leung Tsun Kin, Student of Department of Applied Physics, The Hong Kong Polytechnic University

This work by Leung Tsun Kin of the Department Applied Physics, The Hong Kong Polytechnic University is licensed under a Creative Commons Attribution- NonCommercial-ShareAlike 3.0 Hong Kong License To view a copy of this license, visit Commons Attribution- NonCommercial-ShareAlike 3.0 Hong Kong Licensehttp://creativecommons.org/licenses/by-nc-sa/3.0/hk/deed.en_HK Articles from the Web Article 1 日本農林水產省從福島縣二本松市生產的食米樣本中, 初步驗出達每公斤五百貝可放射性銫, 含量超出政府規定商業電台 12/9/2011 Article 2 松戶和千葉縣柏市等地土壤中放射線量達每小時 0.2 至 0.5 微希放射銫污染擴散至日首都圈 >30/9/2011

This work by Leung Tsun Kin of the Department Applied Physics, The Hong Kong Polytechnic University is licensed under a Creative Commons Attribution- NonCommercial-ShareAlike 3.0 Hong Kong License To view a copy of this license, visit Commons Attribution- NonCommercial-ShareAlike 3.0 Hong Kong Licensehttp://creativecommons.org/licenses/by-nc-sa/3.0/hk/deed.en_HK Units of radiation UnitDefinition Activity ( 放射強度 ) becquerel(Bq)( 貝克 ) Decay occur per second Absorbed dose ( 吸收劑量 ) gray(Gy)( 戈瑞 ) Ionized energy absorbed by 1kg of matter. Effective dose ( 有效劑量 ) sievert(Sv)( 希沃特 ) Millisievert(mSv)( 毫希 ) microsievert(µSv)( 微希 ) Radiation between different parts of body calculated by two weighting factors and absorbed dose. E = ∑(W T x W R x D) W T = weighting factor of body tissues W R = weighting factor of radiation D = absorbed dose Safety limit: 1mSv/yr (excluding background radiation)

This work by Leung Tsun Kin of the Department Applied Physics, The Hong Kong Polytechnic University is licensed under a Creative Commons Attribution- NonCommercial-ShareAlike 3.0 Hong Kong License To view a copy of this license, visit Commons Attribution- NonCommercial-ShareAlike 3.0 Hong Kong Licensehttp://creativecommons.org/licenses/by-nc-sa/3.0/hk/deed.en_HK Calculation example Q : What is the effective dose of 1 Gy of alpha particle to bone marrow? Given W R of alpha particle = 20 W T of bone marrow = 0.12 A : W T x W R x D = 0.12 x 20 x 1 = 2.4Sv Q : What is the effective dose of 1 Gy of beta particle to liver? Given W R of beta particle = 1 W T of liver = 0.04 A : W T x W R x D = 0.04 x 1 x 1 = 0.04Sv

This work by Leung Tsun Kin of the Department Applied Physics, The Hong Kong Polytechnic University is licensed under a Creative Commons Attribution- NonCommercial-ShareAlike 3.0 Hong Kong License To view a copy of this license, visit Commons Attribution- NonCommercial-ShareAlike 3.0 Hong Kong Licensehttp://creativecommons.org/licenses/by-nc-sa/3.0/hk/deed.en_HK Article analysis 1 Cesium-137 ( 銫 -137) does not appear naturally. Main source : nuclear power plant. Safety limit of Cesium-137 for vegetables in Japan 370 Bq/kg  500 Bq/kg after Fukushima Incident. IAEA( 國際原子能機構 ) safety limit for Cesium-137 in vegetables: 1000Bq/kg. 日本農林水產省從福島縣二本松市生產的食米樣本中, 初步驗出達每公斤五百貝可放射性銫, 含量超出政府規定商業電台 12/9/2011

This work by Leung Tsun Kin of the Department Applied Physics, The Hong Kong Polytechnic University is licensed under a Creative Commons Attribution- NonCommercial-ShareAlike 3.0 Hong Kong License To view a copy of this license, visit Commons Attribution- NonCommercial-ShareAlike 3.0 Hong Kong Licensehttp://creativecommons.org/licenses/by-nc-sa/3.0/hk/deed.en_HK Article analysis 2 松戶和千葉縣柏市等地土壤中放射線量達每小時 0.2 至 0.5 微希放射銫污染擴散至日首都圈 >30/9/2011 Calculation: 1mSv/(0.2µSv x 24) ≈ 208 days In this news, if the value measured does not decrease, living in that area for 208 days may over safety limit.

This work by Leung Tsun Kin of the Department Applied Physics, The Hong Kong Polytechnic University is licensed under a Creative Commons Attribution- NonCommercial-ShareAlike 3.0 Hong Kong License To view a copy of this license, visit Commons Attribution- NonCommercial-ShareAlike 3.0 Hong Kong Licensehttp://creativecommons.org/licenses/by-nc-sa/3.0/hk/deed.en_HK Article analysis 3 …radioactivity in the sea near Fukushima is 7.5 million times the normal values… (news adopted from Corriere Online, 5/4/2011) Given normal background radiation = 2.4mSv/yr

This work by Leung Tsun Kin of the Department Applied Physics, The Hong Kong Polytechnic University is licensed under a Creative Commons Attribution- NonCommercial-ShareAlike 3.0 Hong Kong License To view a copy of this license, visit Commons Attribution- NonCommercial-ShareAlike 3.0 Hong Kong Licensehttp://creativecommons.org/licenses/by-nc-sa/3.0/hk/deed.en_HK What happens if the article’s figure is true? In this case, the effective dose ≈ 18000Sv/yr ≈ 6 Sv in 3 hours. As 6 Sv dose is fatal to human, if so, people at there will die within days. However, this did not happen.

This work by Leung Tsun Kin of the Department Applied Physics, The Hong Kong Polytechnic University is licensed under a Creative Commons Attribution- NonCommercial-ShareAlike 3.0 Hong Kong License To view a copy of this license, visit Commons Attribution- NonCommercial-ShareAlike 3.0 Hong Kong Licensehttp://creativecommons.org/licenses/by-nc-sa/3.0/hk/deed.en_HK Recent news > 13/11/2011 平反到日本旅遊受輻射影響的謠言 vs > 16/11/2011 東京銫污染量成旅遊城市之最