WORKING MATERIAL (Limited Distribution) Environmental Consequences of the Chernobyl Accident and Their Remediation: Twenty Years of Experience Report of the UN Chernobyl Forum Expert Group “Environment” (EGE) August 2005 FOREWORD The explosion on 26 April 1986 at the Chernobyl Nuclear Power Plant located just 100 km from the city of Kyiv in what was then the Soviet Union and now is Ukraine, and consequent ten days’ reactor fire resulted in an unprecedented release of radiation and unpredicted adverse consequences both for the public and the environment. Indeed, the IAEA has characterized the event as the “foremost nuclear catastrophe in human history” and the “largest regional release of radionuclides into the atmosphere”. Massive radioactive contamination forced the evacuation of more than 100,000 people from the affected region during 1986, and the relocation, after 1986, of another 200,000 from Belarus, the Russian Federation and Ukraine. Some five million people continue to live in areas contaminated by the accident and have to deal with its environmental, health, social and economic consequences. The national governments of the three affected countries, supported by international organizations, have undertaken costly efforts to remedy contamination, provide medical services and restore the region’s social and economic well-being. The accident’s consequences were not limited to the territories of Belarus, Russia and Ukraine but resulted in substantial transboundary atmospheric transfer and subsequent contamination of numerous European countries that also encountered problems of radiation protection of their populations, although to less extent than the three more affected countries. Although the accident occurred nearly two decades ago, controversy still surrounds the impact of the nuclear disaster. Therefore the IAEA, in cooperation with FAO, UNDP, UNEP, UN- OCHA, UNSCEAR, WHO and The World Bank, as well as the competent authorities of Belarus, the Russian Federation and Ukraine, established the Chernobyl Forum in 2003. The mission of the Forum was — through a series of managerial and expert meetings — to generate “authoritative consensual statements” on the environmental consequences and health effects attributable to radiation exposure arising from the accident as well as to provide advice on environmental remediation and special health care programmes, and to suggest areas where further research is required. The Forum was created as a contribution to the United Nations’ ten years strategy for Chernobyl, launched in 2002 with the publication of Human Consequences of the Chernobyl Nuclear Accident – A Strategy for Recovery. In 2003-2004, two groups of experts from twelve countries, including Belarus, Russia and Ukraine, and from relevant international organizations have assessed the accident’senvironmental and health consequences. In early 2005, the group “Environment,” coordinated by the IAEA, and the group “Health,” coordinated by the WHO, have presented their reports for Forum consideration. Both reports were considered and approved by the Forum at its meeting on 18-20 April 2005. This meeting also decided, inter alia, ‘to consider the approved reports … as a common position of the Forum members, i.e., of the eight United Nations organizations and the three more affected countries, regarding environmental and health consequences of the Chernobyl accident, as well as recommended future actions, i.e., as a consensus within the United Nations system’. This report presents the findings and recommendations of the Chernobyl Forum concerning environmental effects of the Chernobyl accident. The Forum’s report considering health effects is in process of publication under WHO responsibility. The environmental group of experts was chaired by Dr. Lynn Anspaugh from the University of Utah, USA; the scientific secretary of this group and of the whole Chernobyl Forum activity was Dr. Mikhail Balonov of the Division of Radiation, Transport and Waste Safety, IAEA. In all cases the scientists from the UN organisations, the international community, and the three more affected countries have been able to reach consensus in the preparation of their respective documents. After approval by the members of the Forum, this report is the result of that process. CONTENTS EXECUTIVE SUMMARY........................................................................................................ 1 INTRODUCTION...................................................................................................................... 1 RADIOACTIVE CONTAMINATION OF THE ENVIRONMENT ........................................ 2 ENVIRONMENTAL COUNTERMEASURES AND REMEDIATION.................................. 8 HUMAN EXPOSURE ............................................................................................................. 13 RADIATION-INDUCED EFFECTS ON PLANTS AND ANIMALS................................... 16 ENVIRONMENTAL ASPECTS OF DISMANTLEMENT OF THE SHELTER AND RADIOACTIVE WASTE MANAGEMENT ................................................................ 18 1. INTRODUCTION .......................................................................................................... 21 1.1. Purpose ............................................................................................................. 21 1.2. Background....................................................................................................... 21 1.3. Objectives ......................................................................................................... 22 1.4. Method of operation ......................................................................................... 22 1.5. Structure of the Report ..................................................................................... 23 SECTION 1 REFERENCES.................................................................................................... 24 2. RADIOACTIVE CONTAMINATION OF THE ENVIRONMENT............................. 25 2.1. Radionuclide release and deposition ................................................................ 25 2.1.1. Radionuclide source term................................................................... 25 2.1.2. Physical and chemical forms of released materials; hot particles ...... 27 2.1.3. Meteorological conditions during the course of the accident............. 29 2.1.4. Concentration of radionuclides in air ................................................. 32 2.1.5. Deposition of radionuclides on the soil surface ................................. 32 2.1.6. Isotopic composition of deposition .................................................... 40 2.2. Urban environment........................................................................................... 41 2.2.1. Deposition patterns............................................................................. 41 2.2.2. Migration of radionuclides in the urban environment........................ 41 2.2.3. Dynamics of exposure rate ................................................................. 44 2.3. Agricultural environment ................................................................................. 44 2.3.1. Radionuclide transfer in the terrestrial environment.......................... 44 2.3.2. Food-production systems affected by the accident ............................ 46 2.3.3. Early phase......................................................................................... 47 2.3.4. Long-term phase................................................................................. 48 2.3.4.1. Physico-chemistry of radionuclides in the soil plant system ................................................................................ 49 2.3.4.2. Migration of radionuclides in soil...................................... 52 2.3.4.3. Radionuclide transfer from soil to crops............................ 52 2.3.4.4. Dynamics of radionuclide transfer to crops....................... 56 2.3.4.5. Radionuclide transfer to animals ....................................... 60 2.3.5. Current contamination of foodstuffs and expected future trends ....... 65 2.4. Forest environment........................................................................................... 66 2.4.1. Radionuclides in European forests ..................................................... 66 2.4.2. The dynamics of contamination during the early phase..................... 67 2.4.3. The long-term dynamics of radiocaesium in forests .......................... 68 2.4.4. Uptake into edible products................................................................ 69 2.4.5. Contamination of wood ...................................................................... 72 2.4.6. Expected Future Trends...................................................................... 74 2.4.7. Radiation Exposure Pathways Associated With Forests and Forest Products ................................................................................... 74 2.5. Radioactivity in aquatic systems ...................................................................... 76 2.5.1. Introduction ........................................................................................ 76 2.5.2. Radionuclides in surface waters ......................................................... 77 2.5.2.1. Distribution of radionuclides between dissolved and particulate phases............................................................... 77 2.5.2.2. Radioactivity in rivers.......................................................