The nuclear accidents in the Chernobyl NPP and the Fukushima Daiichi Nuclear Power Station Gerhard Proehl
Surface ground deposition of Cs-137 near Chernobyl. (IAEA “STI/PUB/1239” , 2006) Same scale Surface ground deposition of Cs-137 near Fukushima-1. (Based on MEXT Data University of Tsukuba

26 April 1986
−1:23:00 am: • A test of the cooling system begins in unit 4 −1:23:40 am: •  Emergency shut-down fails −1:23:44 am: • The reactor runs out of control and explodes
Emergency measures • Evacuation • Application of stable iodine • Food restrictions • Decontamination of Surfaces • Relocation
26 April
– Morning, town of Pripyat (population 45000, @ 3 km) • Instruction to remain indoors and to close doors and windows –   γ-dose rates start rising
27 April
–   γ-dose rates reach 10 mSv/h – Evacuation of 45000 people starts in Pripyat
Till 7 May
– ca 100 000 evacuees from 76 settlements in a radius of 30 km – Establishment of the Chernobyl Exclusion Zone with a radius of 30 km
In 1986:
– 116000 evacuees in total
Beyond 1986
– Relocation of additional 220 000 people from outside the Exclusion Zone

• Application of stable iodine
– Starting on 26 April – 5.4 million people in the USSR – No systematic distribution
• Food restrictions
– Restrictions on grazing and fresh fodder to reduce thyroid doses => Very effective, if applied immediately – Delayed  implementation of early countermeasures in the former Soviet Union
• Information
– Delayed information of the population •  Private farmers continue to consume fresh milk and green vegetables => high doses to thyroid, which could have been avoided
Chernobyl: In 1986, the USSR Ministry of Health introduced – 100 mSv  as a temporary limit for the average equivalent whole body dose for the period 26 April 1986 until 26 April 1987, – 30 mSv for the 2nd  year – 25 mSv for the 3rd and the 4th year (1988 and 1989) From 1991: Belarus, Russian Federation, Ukraine: – Intervention level  of 1 mSv/α  for post-emergency situations – Exceeding this level triggered the implementation of remediation measures

¹ external+internal dose, excluding thyroid doses
Long-term countermeasures to reduce exposure from radiocaesium Residential areas (emphasis on schools, kindergartens, public buildings) – Washing of buildings with water or special solutions – Cleaning of residential areas and roads – Removal of contaminated soil
Agricultural land
— Ploughing – Food restriction: especially in milk and meat – Treatment of pasture: ploughing, re-seeding, K-fertilizer, lime – Clean fodder and caesium binders (Prussian Blue) Measures to reduce Cs-137 in crops and animal products are still on-going in some areas
Freshwater bodies
– Early restrictions on drinking water and consumption of freshwater fish – Other countermeasures are generally ineffective and not sustainable — Ofe ENEP
Fukushima (Japan) 11 March 2011 of ENEP
Fukushima Daiichi Nuclear Power Station ofo

Flooding of reactor building
•  Back-up diesels stop working => No cooling of the reactors •  No external power due to damage of infrastructure •  Heating up of the reactor core •  Release of radionuclides ENEP
♦ West gate (1) X  Main gate Measurement point 1 O   Measurement point 2 Measurement point 3 Measurement point 4 Measurement point 5 Measurement point 6 Measurement point 7 Measurement point 8
Time Dependence of Air Dose rate at Reading point out of 20 Km Zone of Fukushima Dai-ichi NPP DOI 10.1007/s10669-011-9381-2 Protective actions for the public to reduce external exposure
• Evacuation
– The rapid, temporary removal of people from an area to avoid or reduce short term radiation exposure in a nuclear or radiological emergency
• Sheltering
– The short-term use of a building for protection from external exposure of radionuclides in air or on the ground
• Relocation
– The non-urgent removal of people from an area to avoid long term exposure
11 March
–14:46   Earthquake −19:03 Nuclear emergency declared −20:50   Instruction for evacuation within 0-2 km –21:23   Evacuation within 2-3 km, Stay indoors within 3-10 km
12 March
−05:44   Evacuation within 10 km −18:25   Evacuation within 20 km
15 March
–11:00   Stay indoors within 20-30 km
22 April
Recommendation to leave the area NW outside 20 km Restricted Area ● Specific Spots Recommended for Evacuation Evacuated areas Evacuees in June 2011: 164 000 050 ENEP
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Areas for which evacuation orders are ready to be lifted Areas in which residents are not permitted to live Areas where it is anticipated that residents will not be able to return for a long time N (0 20 km . Early actions for the public to reduce internal exposure
Measures taken
• Intake of stable iodine to block uptake of radioiodine by the thyroid • Setting a limit for total caesium (Cs-134/ Cs-137) in food – March 2011 to March 2012:  500 Bq/kg – From April  2012: 100 Bq/kg • Monitoring on the field and on the market • Providing information on the activity levels in food • Use of clean feed
Effect of the measures
• The rapid application of such measures kept the internal exposure due to intake of food low Fukushima: District average dose to a representative person in 2012 (IAEA, 2015) • External exposure by far dominating • Internal exposure is very low • Strict monitoring of food • Low  limits in foods • Nation-wide food supply Decontamination and remediation activities Radiological criteria set by the Government of Japan Reference level* for remediation of land – 1 mSv/a as a long-term goal – Areas  with a gamma dose rate > 0.23 μSv/h were decontaminated • According to the algorithm applied to determine the dose to people from the gamma dose rate, 0.23 μSv/h is equivalent to a dose of 1 mSv/a
Activity in food
– Total radiocaesium (Cs-134 + Cs-137) in food – March 2011 to March 2012:  500 Bq/kg – From April 2012: 100 Bq/kg
*A reference level is a target, not a strict limit
Fukushima: ENEP
—  O'O ENEP
Source: HPA - EURANC Before and after contamination work in Tamura City (IAEA, 2015) Before and after contamination work in Tamura City (IAEA, 2015)
070
ENEP A) Before > After — 36% reduced Before > Post monitoring — 45% reduced C) Before > After — 21% reduced Before > Post monitoring — 27% reduced B) Before > After — 25% reduced Before > Post monitoring — 37% reduced D) Before > After — 25% reduced Before > Post monitoring — 39% reduced * Conducted between Sep – Oct 2013 Reduction of γ-dose rates by ca. a factor of 1.5 Systematic monitoring of locally grown rice (IAEA, 2015)

• Effective measures available
– Reduction of surface contaminations – Reduction intake of activity • Restriction of food intake and grazing of animals •  Modification of agricultural practice • Information for people on foods to avoid
• Dose reduction achieved
— External dose •  10-50 % (Chernobyl, Fukushima) — Internal dose • Chernobyl: 30 % of the collective ingestion dose (Fesenko, 2009) • Fukushima: Ingestion doses largely avoided due to strict monitoring and food restrictions ene. Interaction of thyroid doses due to I-131 with living habits, enep monitoring and information of the public
Long-term aspects of Cs-137 in the environment  l   ENEP
Next slide ENEP
Surface run-off Continuous input of radiocaesium to water bodies Transfer to crops External exposure during farming Consumption of fish External exposure from sediments
Root uptake, resuspension and erosion => Lead to a continuous re-distribution of radionuclides
Related migration rates are low
• Uptake from arable soil: ca. 0.01 % per year • Resuspension: < 0.1 % per year • Water erosion: depends on topography –Insignificant on a regional scale –Could have local relevance • Accumulation in puddles, ditches, gutters may occur
Continuous decline of activities and dose–rates – Cs-137-activities in suspended sediments – Air-dose rate above decontaminated river banks – Suspended Cs-137 in river water
The decline is faster than the natural decay only
– Migration in soil – Attenuation by less affected sediment- or soil layers – Strong fixation of Cs-137 by clay => low uptake from soil Global experience indicate that these trends will continue ENEP
Impacts of the Fukushima Nudear Accident on Fish and Fishing Grounds OBA & Springer Open ENEP
of ENEP
After decontamination