SciCombinator

Discover the most talked about and latest scientific content & concepts.

Concept: RBMK

27

The root causes and impacts of three severe accidents at large civilian nuclear power plants are reviewed: the Three Mile Island accident in 1979, the Chernobyl accident in 1986, and the Fukushima Daiichi accident in 2011. Impacts include health effects, evacuation of contaminated areas as well as cost estimates and impacts on energy policies and nuclear safety work in various countries. It is concluded that essential objectives for reactor safety work must be: (1) to prevent accidents from developing into severe core damage, even if they are initiated by very unlikely natural or man-made events, and, recognizing that accidents with severe core damage may nevertheless occur; (2) to prevent large-scale and long-lived ground contamination by limiting releases of radioactive nuclides such as cesium to less than about 100 TBq. To achieve these objectives the importance of maintaining high global standards of safety management and safety culture cannot be emphasized enough. All three severe accidents discussed in this paper had their root causes in system deficiencies indicative of poor safety management and poor safety culture in both the nuclear industry and government authorities.

Concepts: Chernobyl disaster, Uranium, Nuclear fission, Nuclear power, Nuclear safety, Three Mile Island accident, RBMK, Nuclear meltdown

5

Most studies of the properties of airborne radionuclides emitted from the Fukushima Daiichi Nuclear Power Plant have focused on the relatively early stages of the accident, and little is known about the characteristics of radiocesium in the long-term. In this study, we analyzed activity size distributions of airborne radiocesium collected over 5 months in Tsukuba, Japan. Radiocesium in the accumulation mode size range (0.1-2 μm in aerodynamic diameter) was overwhelming in the early aerosol samples and decreased with time, while that associated with coarse aerosols remained airborne. We examined the radiocesium adsorbed onto airborne soil particles, and found that the size dependence of (137)Cs surface density adsorbed on soil particles was weak. That is, radiocesium was distributed homogeneously throughout the aerodynamic diameter range of 2.1-11 μm. This characteristic may be related to the reported structure of radiocesium-bearing soil particles collected from the ground, which consisted of an aggregate of specific clay minerals and other non-cesium adsorbing particles. The resuspension factors for the first two aerosol samples collected during late April and May 2011 were close to those in European cities in the months following the Chernobyl accident, despite different soil and weather conditions.

Concepts: Chernobyl disaster, Uranium, Nuclear power, Radioactive contamination, Nuclear safety, Three Mile Island accident, RBMK, Nuclear meltdown

3

After the Chernobyl Nuclear Power Plant accident, the residents living around the Chernobyl were revealed to have been internally exposed to 137Cs through the intake of contaminated local foods. To evaluate the current situation of internal 137Cs exposure and the relationship between the 137Cs soil contamination and internal exposure in residents, we investigated the 137Cs body burden in residents who were living in 10 selected cities from the northern part of the Zhitomir region, Ukraine, and collected soil samples from three family farms and wild forests of each city to measured 137Cs concentrations. The total number of study participants was 36,862, of which 68.9% of them were female. After 2010, the annual effective doses were less than 0.1 mSv in over 90% of the residents. The 137Cs body burden was significantly higher in autumn than other seasons (p < 0.001) and in residents living in more contaminated areas (p < 0.001). We also found a significant correlation between the proportion of residents in each city with an estimated annual exposure dose exceeding 0.1 mSv and 137Cs concentration of soil samples from family farms (r = 0.828, p = 0.003). In conclusion, more than 25 years after the Chernobyl accident, the internal exposure doses to residents living in contaminated areas of northern Ukraine is limited but still related to 137Cs soil contamination. Furthermore, the consumption of local foods is considered to be the cause of internal exposure.

Concepts: Chernobyl disaster, Ukraine, Chernobyl Nuclear Power Plant, Nuclear power, Local food, Three Mile Island accident, RBMK, Nuclear meltdown

3

A possible increase in thyroid cancer in the young represents the most critical health problem to be considered after the nuclear accident in Fukushima, Japan (March 2011), which is an important lesson from the Chernobyl disaster (April 1986). Although it was reported that childhood thyroid cancer had started to increase 3-5 yr after the Chernobyl accident, we speculate that the actual period of latency might have been shorter than reported, considering the delay in initiating thyroid surveillance in the then Soviet Union and also the lower quality of ultrasonographic testing in the 1980s. Our primary objectives in the present study were to identify any possible thyroid abnormality in young Fukushima citizens at a relatively early timepoint (20-30 months) after the accident, and also to strive to find a possible relationship among thyroid ultrasonographic findings, thyroid-relevant biochemical markers, and iodine-131 ground deposition in the locations of residence where they stayed during very early days after the accident.

Concepts: Chernobyl disaster, Ukraine, Nuclear power, Nuclear safety, Three Mile Island accident, Belarus, RBMK, Nuclear meltdown

0

Developments of radioanalytical methods for determination of radiocarbon in wastewaters from nuclear power plants (NPP) with pressurized light water reactors, which would distinguish between the dissolved organic and inorganic forms have been carried out. After preliminary tests, the method was used to process pilot samples from wastewater outlets from the Temelín and Dukovany NPPs (Czech Republic). The results of analysis of pilot water samples collected in 2015 indicate that the instantaneous (14)C releases into the water streams would be about 7.10(-5) (Temelín) and 4.10(-6) (Dukovany) of the total quantity of the (14)C liberated into the environment.

Concepts: Water, Nuclear power, Austria, Plutonium, Nuclear fuel, Enriched uranium, Light water reactor, RBMK

0

What insights can the accident at the Fukushima Daiichi nuclear power plant provide in the reality of decision making on actions to protect the public during a severe reactor and spent fuel pool emergency? In order to answer this question, and with the goal of limiting the consequences of any future emergencies at a nuclear power plant due to severe conditions, this paper presents the main actions taken in response to the emergency in the form of a timeline. The focus of this paper is those insights concerning the progression of an accident due to severe conditions at a light water reactor nuclear power plant that must be understood in order to protect the public.

Concepts: Nuclear power, Plutonium, Nuclear fuel, Enriched uranium, Light water reactor, RBMK, Spent fuel pool, Uranium-235

0

The effects of radiation on polymeric materials are a topic of concern in a wide range of industries including the sterilization, and the nuclear power industry. While much work has concentrated on systems like polyolefins that are radiation sterilized, some work has been done on epoxy systems. The epoxy system studied is an epoxy/amine paint which is representative of the paint that covers the inner surfaces of the French nuclear reactor containment buildings. In case of a severe accident on a Nuclear Power Plant, fission products can be released from the nuclear fuel to the reactor containment building. Among them, volatile iodine (I2) can be produced and can interact with the epoxy-paint. This paint is also subjected to gamma radiation damages (due to the high dose in the containment coming from radionuclides released from the fuel). So the epoxy-paint studied was exposed to gamma radiation under air atmosphere after being loaded with I2 or not. The aim of this study is to characterize by FTIR spectroscopy the iodine-paint interactions, then to identify the radiation damages on the epoxy-paint, and to check their effects on these iodine-paint interactions. This work shows the potential of multi-block analysis method (ANOVA-PCA and COMDIM = AComDim) for such a study as it allows to identify the nature of iodine/epoxy-paint interactions and to characterize the gamma radiation damages on the epoxy-paint. AComDim method conduces to the extraction of Common Components to different tables and highlights factors of influence and their interactions.

Concepts: Nuclear physics, Nuclear fission, Coal, Nuclear power, Electricity generation, Nuclear technology, Three Mile Island accident, RBMK

0

The Fukushima Daiichi Nuclear Power Plant (FNPP) accident, the largest nuclear incident since the 1986 Chernobyl disaster, occurred when the plant was hit by a tsunami triggered by the Great East Japan Earthquake on March 11, 2011. The subsequent uncontrolled release of radioactive substances resulted in massive evacuations in a 20-km zone. To better understand the biological consequences of the FNPP accident, we have been measuring DNA damage levels in cattle in the evacuation zone. DNA damage was evaluated by assessing the levels of DNA double-strand breaks in peripheral blood lymphocytes by immunocytofluorescence-based quantification of γ-H2AX foci. A greater than two-fold increase in the fraction of damaged lymphocytes was observed in all animal cohorts within the evacuation zone, and the levels of DNA damage decreased slightly over the 700-day sample collection period. While the extent of damage appeared to be independent of the distance from the accident site and the estimated radiation dose from radiocesium, we observed age-dependent accumulation of DNA damage. Thus, this study, which was the first to evaluate the biological impact of the FNPP accident utilizing the γ-H2AX assays, indicated the causal relation between high levels of DNA damage in animals living in the evacuation zone and the FNPP accident.

Concepts: DNA, Chernobyl disaster, Nuclear power, Radioactive contamination, Nuclear safety, Three Mile Island accident, RBMK, Nuclear meltdown

0

There are two RBMK-1500 type graphite moderated reactors at the Ignalina nuclear power plant in Lithuania, and they are under decommissioning now. The graphite cannot be disposed of in a near surface repository, because of large amounts of (14)C. Therefore, disposal of the graphite in a geological repository is a reasonable solution. This study presents evaluation of the (14)C transfer by the groundwater pathway into the geosphere from the irradiated graphite in a generic geological repository in crystalline rocks and demonstration of the role of the different components of the engineered barrier system by performing local sensitivity analysis. The speciation of the released (14)C into organic and inorganic compounds as well as the most recent information on (14)C source term was taken into account. Two alternatives were considered in the analysis: disposal of graphite in containers with encapsulant and without it. It was evaluated that the maximal fractional flux of inorganic (14)C into the geosphere can vary from 10(-11)y(-1) (for non-encapsulated graphite) to 10(-12)y(-1) (for encapsulated graphite) while of organic (14)C it was about 10(-3)y(-1) of its inventory. Such difference demonstrates that investigations on the (14)C inventory and chemical form in which it is released are especially important. The parameter with the highest influence on the maximal flux into the geosphere for inorganic (14)C transfer was the sorption coefficient in the backfill and for organic (14)C transfer - the backfill hydraulic conductivity.

Concepts: Chemistry, Organic compound, Nuclear power, Inorganic compound, Lithuania, RBMK

0

30 years after the Chernobyl Nuclear Power Plant (CNPP) accident, its radioactive releases still remain of great interest mainly due to the long half-lives of many radionuclides emitted. Observations from the terrestrial environment, which hosts radionuclides for many years after initial deposition, are important for health and environmental assessments. Furthermore, such measurements are the basis for validation of atmospheric transport models and can be used for constraining the still not accurately known source terms. However, although the “Atlas of cesium deposition on Europe after the Chernobyl accident” (hereafter referred to as “Atlas”) has been published since 1998, less than 1% of the direct observations of (137)Cs deposition has been made publicly available. The remaining ones are neither accessible nor traceable to specific data providers and a large fraction of these data might have been lost entirely. The present paper is an effort to rescue some of the data collected over the years following the CNPP accident and make them publicly available. The database includes surface air activity concentrations and deposition observations for (131)I, (134)Cs and (137)Cs measured and provided by Former Soviet Union authorities the years that followed the accident. Using the same interpolation tool as the official authorities, we have reconstructed a deposition map of (137)Cs based on about 3% of the data used to create the Atlas map. The reconstructed deposition map is very similar to the official one, but it has the advantage that it is based exclusively on documented data sources, which are all made available within this publication. In contrast to the official map, our deposition map is therefore reproducible and all underlying data can be used also for other purposes. The efficacy of the database was proved using simulated activity concentrations and deposition of (137)Cs from a Langrangian and a Euleurian transport model.

Concepts: Chernobyl disaster, Isotope, Nuclear power, Radioactive contamination, Nuclear safety, Three Mile Island accident, RBMK, Nuclear meltdown