The other report on Chernobyl (TORCH)
|Auteur||I.Fairlie, Greens in EP, EFA|
|Classificatie||18.104.22.168/30 (TSJERNOBYL - ONGELUK & OMGEVING - MEDISCH/MUTATIES)|
|Opmerking||Also available in Ukrainian: 22.214.171.124/31. See 126.96.36.199/112 for TORCH 2016|
Uit de publicatie:
EXECUTIVE SUMMARY AND CONCLUSIONS On 26 April 2006, twenty years will have passed since the Chernobyl nuclear power plant exploded, releasing large quantities of radioactive gases and particles throughout the northern hemisphere. While the effects of the disaster remain apparent particularly in Belarus, Ukraine and Russia, where millions of people are affected, Chernobyl’s fallout also seriously contaminated other areas of the world, especially Western Europe. The Other Report on Chernobyl (TORCH) provides an independent scientific examina- tion of available data on the release of radioactivity into the environment and subsequent health-related effects of the Chernobyl accident. The Report also critically examines recent official reports on the impact of the Chernobyl accident, in particular two reports by the “UN Chernobyl Forum” released by the International Atomic Energy Agency (IAEA) and the World Health Organisation (WHO) in September 2005 6 , which have received considerable attention by the international media. Many uncertainties surround risk estimates from radiation exposures. The most fundamental is that the effects of very low doses are uncertain. The current theory is that the relationship between dose and detrimental effect is linear without threshold down to zero dose. In other words, there is no safe level of radiation exposure. However the risk, at low doses, may be supralinear, resulting in relatively higher risks, or sublinear, resulting in relatively lower risks. Another major source of uncertainty lies in the estimates of internal radiation doses, that is, from nuclides, which are inhaled or ingested. These are important sources of the radiation from Chernobyl’s fallout. Uncertainties in internal radiation risks could be very large, varying in magnitude from factors of 2 (up and down from the central estimate) in the most favourable cases, to 10 or more in the least favourable cases for certain radionuclides. The Accident Early on April 26 1986, two explosions in Chernobyl unit 4 completely destroyed the reactor. The explosions sent large clouds of radioactive gases and debris 7 - 9 kilometres into the atmosphere. About 30% of the reactor’s 190 tons of fuel was distributed over the reactor building and surrounding areas and about 1-2% was ejected into the atmosphere. The reactor’s inventory of radioactive gases was released at this time. The subsequent fire, fuelled by 1,700 tons of graphite moderator, lasted for eight days. This fire was the principal reason for the extreme severity of the Chernobyl disaster. How Much Radioactivity Was Released? The World Health Organisation (WHO) has estimated that the total radioactivity from Chernobyl was 200 times that of the combined releases from the atomic bombs dropped on Hiroshima and Nagasaki. The amount of radioactivity released during a radiological event, is called the ‘source term’. It is important because it is used to verify nuclide depositions throughout the northern hemisphere. From these, collective doses and predicted excess illnesses and fatalities can be estimated. Of the cocktail of radionuclides that were released, the fission products iodine-131, caesium-134 and caesium-137 have the most radiological significance. Iodine-131 with its short radioactive half-life 7 of eight days had great radiological impact in the short term because of its doses to the thyroid. Caesium-134 (half-life of 2 years) and caesium-137 (half-life of 30 years) have the greater radiological impacts in the medium and long terms. Relatively small amounts of caesium-134 now remain, but for the first two decades after 1986, it was an important contributor to doses. Most of the other radionuclides will have completely decayed by now. Over the next few decades, interest will continue to focus on caesium-137, with secondary attention on strontium-90, which is more important in areas nearer Chernobyl. Over the longer term (hundreds to thousands of years), the radionuclides of continuing interest will be the activation products, including the isotopes of plutonium, neptunium and curium. However, overall doses from these activation products are expected to remain low, compared with the doses from caesium-137. The authors have reassessed the percentages of the initial reactor inventories of caesium- 137 and iodine-131 which were released to the environment. They conclude that official figures underestimate the amounts released by 15% (iodine-131) and 30% (caesium-137). Dispersion and Deposition of Chernobyl Fallout During the 10 day period of maximum releases from Chernobyl, volatile radionuclides were continuously discharged and dispersed across many parts of Europe and later the entire northern hemisphere. For example, relatively high fallout concentrations were measured at Hiroshima in Japan, over 8,000 km from Chernobyl. Extensive surveying of Chernobyl’s caesium-137 contamination was carried out in the 1990s under the auspices of the European Commission. The largest concentrations of volatile nuclides and fuel particles occurred in Belarus, Russia and Ukraine. But more than half of the total quantity of Chernobyl’s volatile inventory was deposited outside these countries. Russia, Belarus and Ukraine received the highest amounts of fallout while former Yugoslavia, Finland, Sweden, Bulgaria, Norway, Rumania, Germany, Austria and Poland each received more than one petabecquerel (1015 Bq or one million billion becquerels) of caesium-137, a very large amount of radioactivity. 8 In area terms, about 3,900,000 km2 of Europe was contaminated by caesium-137 (above 4,000 Bq/m2) which is 40% of the surface area of Europe. Curiously, this latter figure does not appear to have been published and, certainly has never reached the public’s consciousness in Europe. Also 218,000 km2 or about 2.3% of Europe’s surface area was contaminated to higher levels (greater than 40,000 Bq/m2 Cs-137 9 ). This is the area cited by IAEA/WHO and UNSCEAR, which shows that they have been remarkably selective in their reporting. In terms of their surface areas, Belarus (22% of its land area) and Austria (13%) were most affected by higher levels of contamination. Other countries were seriously affected; for example, more than 5% of Ukraine, Finland and Sweden were contaminated to high levels (> 40,000 Bq/m2 caesium-137). More than 80% of Moldova, the European part of Turkey, Slovenia, Switzerland, Austria and the Slovak Republic were contaminated to lower levels (> 4,000 Bq/m2 caesium-137). And 44% of Germany and 34% of the UK were similarly affected. The IAEA/WHO reports do not mention these comprehensive datasets on European contamination by the European Commission. No explanation is given for this omission. Moreover, the IAEA/WHO reports do not discuss deposition and radiation doses in any country apart from Belarus, Ukraine and Russia. Although heavy depositions certainly occurred there, the omission of any examination of Chernobyl fallout in the rest of Europe and the northern hemisphere is questionable.