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“Nuclear Radiation, Environment and Energy” Workshop

General discussion on the Daya Baycontingency plan( 大亞灣應變計劃的通識討論 )

香港理工大學應用物理系王碧裕

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-50 km from Tsim Sha Tsui

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Platform of spreading

radioactive plume(輻射煙羽 )Iodine-131Half-life: 8 daysgaseous and volatile

Ingestion of contaminated foodstuffs and drinking waterCesium-137Half-life: 30 yearsWater-soluble

-release of radioactive fission products (放射性裂變產物 ) into the atmosphere

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TECHNICAL WORKING GROUP ( 技術工作小組 ) - Secretary for Security or his representative (Chairman)

2. IAEA four-category system (國際原子能機構的四級分類系統 ) (classifying nuclear power emergencies)

Decision on the activation level of the plan ( 決定應變計劃的動階段 )1. Technical advice from these key departments

Four-category system (四級分類系統 )

Counter-measures in activation levels ( 動階段 )

3. Site Emergency (站址緊急情況 )

4. Off-Site Emergency (站外緊急情況 )

1. Plume Exposure Pathway Counter-measure

( 煙羽防護措施 )2. Ingestion Pathway Counter-measure

( 飲食防護措施 )

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1. Plume Exposure Pathway Counter-measure ( 煙羽防護措施 )

Counter-measures

(a) Evacuation or sheltering ( 疏散或掩蔽 )

-only apply to Ping Chau (坪洲 )

(within 20 km of the nuclear plant)

(ii)Sheltering (掩蔽 )

(i)Evacuation (疏散 )

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1. Plume Exposure Pathway Counter-measure ( 煙羽防護措施 )

Counter-measures

(b) Monitoring the radiation level (輻射水平監測 )of - persons who have been within the 20 km range- incoming cargo

(c) Issue of potassium iodate tablet (派發碘酸鉀藥片 )

2. Ingestion Pathway Counter-measure ( 飲食防護措施 )

(a) Control of food and livestock (食物及禽畜管制 )

(b) Control of water (水質管制 )

-1000 Bq/kg

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Operational criteria for evacuation (IAEA)

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Air Dose Rate Readingson 17th March, 2011

=170.0µSv/hr

Major factors that affect the spreading of plume1. Distance2. Dilution by the atmosphere

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Major factors that affect the spreading of plume1. Distance2. Dilution by the atmosphere

Criteria for evacuation:> 297.62µSv/hr

MODEL 1:

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Spread in “sphere”

Major factors that affect the spreading of plume1. Distance2. Dilution by the atmosphere

MODEL 2:

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Major factors that affect the spreading of plume1. Distance2. Dilution by the atmosphere

Spread in “sphere”km µSv/hr

22 475.6264

23 416.2464

24 366.3534

25 324.1261

26 288.1469

27 257.3017

28 230.7065

29 207.6539

30 187.573

Criteria for evacuation:> 297.62µSv/hr

MODEL 2:

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Wind:- wind direction affect the direction of dispersion

- wind speed affect the rate of dispersion

Uncertainties that affect the spreading of plume1. Size of explosion2. Weather (Wind, Rain)

Rain :- rainfall greatly enhance the deposition rate → Radiation level in air ↓

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“First assessment indicates that one of the IAEA operational criteria for evacuation is exceeded in Iitate village.” --- IAEA

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Reference data:Akogi Teshichiro, Namie Town, Futaba County (双叶郡浪江町赤宇木手七郎 )- 31km from Fukushima Dai-ichi Nuclear Power Plant

Time for the evacuation zone to safety level

17/3/2011 – 23/4/2011 Criteria for evacuation : > 297.62µSv/hr

http://eq.wide.ad.jp/index_en.html (April 24th version -http://eq.wide.ad.jp/files_en/110424map_1800rev2_en.pdf)

This work by Wong Pik Yu of the Department of 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 http://creativecommons.org/licenses/by-nc-sa/3.0/hk/deed.en_HK

Days µSv/hr

232 11.53592

233 11.50164

234 11.4676

235 11.43381

236 11.40026

237 11.36696

238 11.33388

239 11.30105

240 11.26844

Time for the evacuation zone to safety level

<11.42µSv/hr

This work by Wong Pik Yu of the Department of 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 http://creativecommons.org/licenses/by-nc-sa/3.0/hk/deed.en_HK

THE END