Разделение изотопов и применение их в ядерном реакторе

Both views were heavily lobbied by different groups, including the reactor's designers, power plant personnel, and the Soviet and Ukrainian governments. According to the IAEA's 1986 analysis, the main cause of the accident was the operators' actions. But according to the IAEA's 1993 revised analysis the main cause was the reactor's design.[51] One reason there were such contradictory viewpoints and so much debate about the causes of the Chernobyl accident was that the primary data covering the disaster, as registered by the instruments and sensors, were not completely published in the official sources.

Once again, the human factor had to be considered as a major element in causing the accident. INSAG notes that both the operating regulations and staff handled the disabling of the reactor protection easily enough: witness the length of time for which the ECCS was out of service while the reactor was operated at half power. INSAG’s view is that it was the operating crew's deviation from the test program that was mostly to blame. “Most reprehensibly, unapproved changes in the test procedure were deliberately made on the spot, although the plant was known to be in a very different condition from that intended for the test.” [11]:24

 

As in the previously released report INSAG-1, close attention is paid in report INSAG-7 to the inadequate (at the moment of the accident) “culture of safety” at all levels. Deficiency in the safety culture was inherent not only at the operational stage but also, and to no lesser extent, during activities at other stages in the lifetime of nuclear power plants (including design, engineering, construction, manufacture and regulation). The poor quality of operating procedures and instructions, and their conflicting character, put a heavy burden on the operating crew, including the Chief Engineer. “The accident can be said to have flowed from a deficient safety culture, not only at the Chernobyl plant, but throughout the Soviet design, operating and regulatory organizations for nuclear power that existed at that time.” [11]:24

Effects

Main article: Chernobyl disaster effects

International spread of radioactive substances

An exhibit at the Ukrainian National Chernobyl Museum. Mutations in both humans and other animals may have increased as a result of the disaster.[52]

Four hundred times more radioactive material was released than had been by the atomic bombing of Hiroshima. However, compared to the total amount released by nuclear weapons testing during the 1950s and 1960s, the Chernobyl disaster released 1/100 to 1/1000 the radioactivity.[53] The fallout was detected over all of Europe except for the Iberian Peninsula.[54][55][56] This article appears to contradict the article Forsmark Nuclear Power Plant#April 1986. Please see discussion on the linked talk page. Please do not remove this message until the contradictions are resolved. (March 2011)

The initial evidence that a major release of radioactive material was affecting other countries came not from Soviet sources, but from Sweden, where on the morning of 28 April[57] workers at the Forsmark Nuclear Power Plant (approximately 1,100 km (680 mi) from the Chernobyl site) were found to have radioactive particles on their clothes.[58] It was Sweden's search for the source of radioactivity, after they had determined there was no leak at the Swedish plant, that at noon on April 28 led to the first hint of a serious nuclear problem in the western Soviet Union. Hence the evacuation of Pripyat on April 27, 36 hours after the initial explosions, was silently completed before the disaster became known outside the Soviet Union. The rise in radiation levels had at that time already been measured in Finland, but a civil service strike delayed the response and publication.[59]Areas of Europe contaminated with Cs137 (km2)[60]

Country 37-185 kBq/m2 185-555 kBq/m2 555-1480 kBq/m2 +1480 kBq/m2

Russia 49 800 5 700 2 100 300

Belarus 29 900 10 200 4200 2200

Ukraine 37 200 3 200 900 600

Sweden 12 000 - - -

Finland 11 500 - - -

Austria 8 600 - - -

Norway 5 200 - - -

Bulgaria 4 800 - - -

Switzerland 1 300 - - -

Greece 1 200 - - -

Slovenia 300 - - -

Italy 300 - - -

Moldavia 60 - - -

 

 

Contamination from the Chernobyl accident was scattered irregularly depending on weather conditions. Reports from Soviet and Western scientists indicate that Belarus received about 60% of the contamination that fell on the former Soviet Union. However, the 2006 TORCH report stated that half of the volatile particles had landed outside Ukraine, Belarus, and Russia. A large area in Russia south of Bryansk was also contaminated, as were parts of northwestern Ukraine. Studies in surrounding countries indicate that over one million people could have been affected by radiation.

Recently published data from a long-term monitoring program (The Korma Report)[62] shows a decrease in internal radiation exposure of the inhabitants of a region in Belarus close to Gomel. Resettlement may even be possible in prohibited areas provided that people comply with appropriate dietary rules.

In Western Europe, precautionary measures taken in response to the radiation included seemingly arbitrary regulations banning the importation of certain foods but not others. In France some officials stated that the Chernobyl accident had no adverse effects.[63] Official figures in southern Bavaria in Germany indicated that some wild plant species contained substantial levels of caesium, which were believed to have been passed onto them by wild boars, a significant number of which had already contained radioactive particles above the allowed level, consuming them.

Radioactive release

The external gamma dose for a person in the open near the Chernobyl site.

Contributions of the various isotopes to the (atmospheric) dose in the contaminated area soon after the accident.

Like many other releases of radioactivity into the environment, the Chernobyl release was controlled by the physical and chemical properties of the radioactive elements in the core. While the general population often perceives plutonium as a particularly dangerous nuclear fuel, its effects are almost eclipsed by those of its fission products. Particularly dangerous are highly radioactive compounds that accumulate in the food chain, such as some isotopes of iodine and strontium.

Two reports on the release of radioisotopes from the site were made available, one by the OSTI and a more detailed report by the OECD, both in 1998.[65][66] At different times after the accident, different isotopes were responsible for the majority of the external dose. The dose that was calculated is that received from external gamma irradiation for a person standing in the open. The dose to a person in a shelter or the internal dose is harder to estimate.

The release of radioisotopes from the nuclear fuel was largely controlled by their boiling points, and the majority of the radioactivity present in the core was retained in the reactor.

All of the noble gases, including krypton and xenon, contained within the reactor were released immediately into the atmosphere by the first steam explosion.

About 1760 PBq of I-131, 55% of the radioactive iodine in the reactor, was released, as a mixture of vapor, solid particles, and organic iodine compounds.

Caesium (85 PBq Cs-137 [67]) and tellurium were released in aerosol form.

An early estimate for fuel material released to the environment was 3 ± 1.5%; this was later revised to 3.5 ± 0.5%. This corresponds to the atmospheric emission of 6 t of fragmented fuel.

 

Two sizes of particles were released: small particles of 0.3 to 1.5 micrometers (aerodynamic diameter) and large particles of 10 micrometers. The large particles contained about 80% to 90% of the released nonvolatile radioisotopes zirconium-95, niobium-95, lanthanum-140, cerium-144 and the transuranic elements, including neptunium, plutonium and the minor actinides, embedded in a uranium oxide matrix.

Health of plant workers and local people

In the aftermath of the accident, 237 people suffered from acute radiation sickness, of whom 31 died within the first three months.[68][69] Most of these were fire and rescue workers trying to bring the accident under control, who were not fully aware of how dangerous exposure to the radiation in the smoke was. Whereas, in the World Health Organization's 2006 report of the Chernobyl Forum expert group on the 237 emergency workers who were diagnosed with ARS, ARS was identified as the cause of death for 28 of these people within the first few months after the disaster. There were no further deaths identified, in the general population affected by the disaster, as being caused by ARS. Of the 72,000 Russian Emergency Workers being studied, 216 non-cancer deaths are attributed to the disaster, between 1991 and 1998. The latency period for solid cancers caused by excess radiation exposure is 10 or more years; thus at the time of the WHO report being undertaken, the rates of solid cancer deaths were no greater than the general population. Some 135,000 people were evacuated from the area, including 50,000 from Pripyat.

Residual radioactivity in the environment

Rivers, lakes and reservoirs

Earth Observing-1 image of the reactor and surrounding area in April 2009

The Chernobyl nuclear power plant is located next to the Pripyat River, which feeds into the Dnipro River reservoir system, one of the largest surface water systems in Europe. The radioactive contamination of aquatic systems therefore became a major problem in the immediate aftermath of the accident.[70] In the most affected areas of Ukraine, levels of radioactivity (particularly radioiodine: I-131, radiocaesium: Cs-137 and radiostrontium: Sr-90) in drinking water caused concern during the weeks and months after the accident. After this initial period, however, radioactivity in rivers and reservoirs was generally below guideline limits for safe drinking water.

Bio-accumulation of radioactivity in fish resulted in concentrations (both in western Europe and in the former Soviet Union) that in many cases were significantly above guideline maximum levels for consumption. Guideline maximum levels for radiocaesium in fish vary from country to country but are approximately 1,000 Bq/kg in the European Union. In the Kiev Reservoir in Ukraine, concentrations in fish were several thousand Bq/kg during the years after the accident.  In small "closed" lakes in Belarus and the Bryansk region of Russia, concentrations in a number of fish species varied from 0.1 to 60 kBq/kg during the period 1990–92.[73] The contamination of fish caused short-term concern in parts of the UK and Germany and in the long term (years rather than months) in the affected areas of Ukraine, Belarus, and Russia as well as in parts of Scandinavia.

Groundwater

Map of radiation levels in 1996 around Chernobyl.

Groundwater was not badly affected by the Chernobyl accident since radionuclides with short half-lives decayed away long before they could affect groundwater supplies, and longer-lived radionuclides such as radiocaesium and radiostrontium were adsorbed to surface soils before they could transfer to groundwater.[74] However, significant transfers of radionuclides to groundwater have occurred from waste disposal sites in the 30 km (19 mi) exclusion zone around Chernobyl. Although there is a potential for transfer of radionuclides from these disposal sites off-site (i.e. out of the 30 km (19 mi) exclusion zone), the IAEA Chernobyl Report[74] argues that this is not significant in comparison to current levels of washout of surface-deposited radioactivity.

Flora and fauna

The major plume of radiation released by the Chernobyl disaster was carried directly over what is now called the Red Forest. Radioactive particles settled on trees, killing areas of pine forest.

After the disaster, four square kilometers of pine forest directly downwind of the reactor turned reddish-brown and died, earning the name of the "Red Forest".[75] Some animals in the worst-hit areas also died or stopped reproducing. Most domestic animals were removed from the exclusion zone, but horses left on an island in the Pripyat River 6 km (4 mi) from the power plant died when their thyroid glands were destroyed by radiation doses of 150–200 Sv.[76] Some cattle on the same island died and those that survived were stunted because of thyroid damage. The next generation appeared to be normal.

A robot sent into the reactor itself has returned with samples of black, melanin-rich radiotrophic fungi that are growing on the reactor's walls.

Of the 440,350 wild boar killed in the 2010 hunting season in Germany, over 1,000 were found to be contaminated with levels of radiation above the permitted limit of 600 bequerels, due to residual radioactivity from Chernobyl.

The Norwegian Agricultural Authority reported that in 2009 a total of 18,000 livestock in Norway needed to be given uncontaminated feed for a period of time before slaughter in order to ensure that their meat was safe for human consumption. This was due to residual radioactivity from Chernobyl in the plants they graze on in the wild during the summer. The after-effects of Chernobyl were expected to be seen for a further 100 years, although the severity of the effects would decline over that period.

Chernobyl after the disaster

Main article: Chernobyl after the disaster

Recovery projects

The Chernobyl Shelter Fund

Computer impression of the New Safe Confinement to cover the No. 4 Reactor at Chernobyl

The Chernobyl Shelter Fund was established in 1997 at the Denver 23rd G8 summit to finance the Shelter Implementation Plan (SIP). The plan calls for transforming the site into an ecologically safe condition by means of stabilization of the sarcophagus followed by construction of a New Safe Confinement (NSC). While the original cost estimate for the SIP was US$768 million, the 2006 estimate was $1.2 billion. The SIP is being managed by a consortium of Bechtel, Battelle, and Electricité de France, and conceptual design for the NSC consists of a movable arch, constructed away from the shelter to avoid high radiation, to be slid over the sarcophagus. The NSC is expected to be completed in 2013, and will be the largest movable structure ever built.

Dimensions:

Span: 270 m (886 ft)

Height: 100 m (330 ft)

Length: 150 m (492 ft)

The United Nations Development Programme

The United Nations Development Programme has launched in 2003 a specific project called the Chernobyl Recovery and Development Programme (CRDP) for the recovery of the affected areas.[80] The programme was initiated in February 2002 based on the recommendations in the report on Human Consequences of the Chernobyl Nuclear Accident. The main goal of the CRDP’s activities is supporting the Government of Ukraine in mitigating long-term social, economic, and ecological consequences of the Chernobyl catastrophe. CRDP works in the four most Chernobyl-affected areas in Ukraine: Kyivska, Zhytomyrska, Chernihivska and Rivnenska.

The International Project on the Health Effects of the Chernobyl Accident

The International Project on the Health Effects of the Chernobyl Accident (IPEHCA) was created and received US $20 million, mainly from Japan, in hopes of discovering the main cause of health problems due to 131I radiation. These funds were divided between Ukraine, Belarus, and Russia, the three main affected countries, for further investigation of health effects. As there was significant corruption in former Soviet countries, most of the foreign aid was given to Russia, and no positive outcome from this money has been demonstrated.[citation needed]

Assessing the disaster's effects on human health

Demonstration on Chernobyl day near WHO in Geneva

An international assessment of the health effects of the Chernobyl accident is contained in a series of reports by the United Nations Scientific Committee of the Effects of Atomic Radiation (UNSCEAR).[81] UNSCEAR was set up as a collaboration between various UN bodies, including the World Health Organisation, after the atomic bomb attacks on Hiroshima and Nagasaki, to assess the long-term effects of radiation on human health.

UNSCEAR has conducted 20 years of detailed scientific and epidemiological research on the effects of the Chernobyl accident. Apart from the 57 direct deaths in the accident itself, UNSCEAR originally predicted up to 4,000 additional cancer cases due to the accident.[82]

UNSCEAR now states:

Among the residents of Belarus, the Russian Federation and Ukraine, there had been up to the year 2005 more than 6,000 cases of thyroid cancer reported in children and adolescents who were exposed at the time of the accident, and more cases can be expected during the next decades. Notwithstanding the influence of enhanced screening regimes, many of those cancers were most likely caused by radiation exposures shortly after the accident. Apart from this increase, there is no evidence of a major public health impact attributable to radiation exposure two decades after the accident. There is no scientific evidence of increases in overall cancer incidence or mortality rates or in rates of non-malignant disorders that could be related to radiation exposure. The incidence of leukaemia in the general population, one of the main concerns owing to the shorter time expected between exposure and its occurrence compared with solid cancers, does not appear to be elevated. Although those most highly exposed individuals are at an increased risk of radiation-associated effects, the great majority of the population is not likely to experience serious health consequences as a result of radiation from the Chernobyl accident. Many other health problems have been noted in the populations that are not related to radiation exposure.

However, thyroid cancer is generally treatable.[84] With proper treatment, the five-year survival rate of thyroid cancer is 96%, and 92% after 30 years,[85] suggesting there may be up to 500 early deaths from this cause.

In addition, the IAEA states that there has been no increase in the rate of birth defects or abnormalities, or solid cancers (such as lung cancer) corroborating UNSCEAR's assessments.[86] UNSCEAR does also raise the possibility of long term genetic defects, pointing to a doubling of radiation-induced minisatellite mutations among children born in 1994.[87] There is some dispute over the control groups in this study and the long term effects are not clear.

The Chernobyl Forum is a regular meeting of IAEA, other United Nations organizations (FAO, UN-OCHA, UNDP, UNEP, UNSCEAR, WHO, and the World Bank), and the governments of Belarus, Russia, and Ukraine that issues regular scientific assessments of the evidence for health effects of the Chernobyl accident.[88] The Chernobyl Forum concluded that twenty-eight emergency workers died from acute radiation syndrome including beta burns and 15 patients died from thyroid cancer, and it roughly estimated that cancer deaths caused by Chernobyl may reach a total of about 4,000 among the 600,000 people having received the greatest exposures. It also concluded that a greater risk than the long-term effects of radiation exposure is the risk to mental health of exaggerated fears about the effects of radiation:[86]

The designation of the affected population as “victims” rather than “survivors” has led them to perceive themselves as helpless, weak and lacking control over their future. This, in turn, has led either to over cautious behavior and exaggerated health concerns, or to reckless conduct, such as consumption of mushrooms, berries and game from areas still designated as highly contaminated, overuse of alcohol and tobacco, and unprotected promiscuous sexual activity.[89]

Fred Mettler commented that 20 years later:

The population remains largely unsure of what the effects of radiation actually are and retain a sense of foreboding. A number of adolescents and young adults who have been exposed to modest or small amounts of radiation feel that they are somehow fatally flawed and there is no downside to using illicit drugs or having unprotected sex. To reverse such attitudes and behaviors will likely take years although some youth groups have begun programs that have promise.

In addition, disadvantaged children around Chernobyl suffer from health problems that are attributable not only to the Chernobyl accident, but also to the poor state of post-Soviet health systems.

Another study critical of the Chernobyl Forum report was commissioned by Greenpeace, which asserts that "the most recently published figures indicate that in Belarus, Russia and Ukraine alone the accident could have resulted in an estimated 200,000 additional deaths in the period between 1990 and 2004."[92] The Scientific Secretary of the Chernobyl Forum questioned the choice by the report authors to selectively use non-peer reviewed papers and only those non-peer reviewed papers as their source material while Gregory Härtl (spokesman for the WHO) expressed concern that the conclusions were motivated by ideology.[93]

 

The German affiliate of the International Physicians for the Prevention of Nuclear War (IPPNW) argued that more than 10,000 people are today affected by thyroid cancer and 50,000 cases are expected in the future.

Chernobyl: Consequences of the Catastrophe for People and the Environment is an English translation of the 2007 Russian publication Chernobyl. It was published online in 2009 by the New York Academy of Sciences in their Annals of the New York Academy of Sciences. It presents an analysis of scientific literature and concludes that medical records between 1986, the year of the accident, and 2004 reflect 985,000 deaths as a result of the radioactivity released. The authors suggest that most of the deaths were in Russia, Belarus and Ukraine, but others were spread through the many other countries the radiation from Chernobyl struck.[95] The literature analysis draws on over 1,000 published titles and over 5,000 internet and printed publications discussing the consequences of the Chernobyl disaster. The authors contend that those publications and papers were written by leading Eastern European authorities and have largely been downplayed or ignored by the IAEA and UNSCEAR.[96] Author Alexy V. Yablokov was also one of the general editors on the Greenpeace commissioned report also criticizing the Chernobyl Forum finds published one year before the Russian-language version of this report.

Other health problems linked with the Chernobyl disaster include

Graph of Down syndrome cases in Belarus around the time of Chernobyl

Down syndrome (trisomy 21). In West Berlin, Germany, prevalence of Down syndrome (trisomy 21) peaked 9 months following the main fallout.[11, 12][citation needed] Between 1980 and 1986, the birth prevalence of Down syndrome was quite stable (i.e., 1.35–1.59 per 1,000 live births [27–31 cases]).[citation needed] In 1987, 46 cases were diagnosed (prevalence = 2.11 per 1,000 live births). Most of the excess resulted from a cluster of 12 cases among children born in January 1987.[citation needed] The prevalence of Down syndrome in 1988 was 1.77, and in 1989, it reached pre-Chernobyl values. The authors[citation needed] noted that the isolated geographical position of West Berlin before reunification, the free genetic counseling, and complete coverage of the population through one central cytogenetic laboratory support completeness of case ascertainment; in addition, constant culture preparation and analysis protocols ensure a high quality of data.

Chromosomal aberrations. Reports of structural chromosome aberrations in people exposed to fallout in Belarus and other parts of the former Soviet Union, Austria, and Germany argue against a simple dose-response relationship between degree of exposure and incidence of aberrations.[citation needed] These findings are relevant because a close relationship exists between chromosome changes and congenital malformations. Inasmuch as some types of aberrations are almost specific for ionizing radiation, researchers use aberrations to assess exposure dose. On the basis of current coefficients, however, one cannot assume that calculation of individual exposure doses resulting from fallout would not induce measurable rates of chromosome aberrations.[citation needed]

Neural tube defects (NTDs) in Turkey. During the embryonic phase of fetal development, the neural tube differentiates into the brain and spinal cord (i.e., collectively forming the central nervous system). Chemical or physical interactions with this process can cause NTDs. Common features of this class of malformations are more or less extended fissures, often accompanied by consecutive dislocation of central nervous system (CNS) tissue. NTDs include spina bifida occulta and aperta, encephalocele, and—in the extreme case—anencephaly. The first evidence in support of a possible association between CNS malformations and fallout from Chernobyl was published by Akar et al.. in 1988.[citation needed] The Mustafakemalpasa State Hospital, Bursa region, covers a population of approximately 90,000. Investigators have documented the prevalence of malformations since 1983.[citation needed] The prevalence of NTDs was 1.7 to 9.2 per 1,000 births, but during the first 6 months of 1987 increased to 20 per 1,000 (12 cases). The excess was most pronounced for the subgroup of anencephalics, in which prevalence increased 5-fold (i.e., 10 per 1,000 [6 cases]). In the consecutive months that followed (i.e., July–December 1987), the prevalence decreased again (1.3 per 1,000 for all NTDs, 0.6 per 1,000 for anencephaly), and it reached pre-Chernobyl levels during the first half of 1988 (all NTDs: 0.6 per 1,000; anencephaly: 0.2 per 1,000). This initial report was supported by several similar findings in observational studies from different regions of Turkey.[citation needed]