Nuclear Power Plant Accident Research Articles

Importance of continuing health care before emergency hospital evacuation: a fatal case of a hospitalized patient in a hospital within 5 km radius of Fukushima Daiichi Nuclear Power Plant: a case report

BackgroundAfter a disaster, it is essential to maintain the health care supply levels to minimize the health impact on vulnerable populations. During the 2011 Fukushima Daiichi Nuclear Power Plant accident, hospitals within a 20 km radius were forced to make an immediate evacuation, causing a wide range of short- and long-term health problems. However, there is limited information on how the disaster disrupted the continuity of health care for hospitalized patients in the acute phase of the disaster.Case presentationAn 86-year-old Japanese man who needed central venous nutrition, oxygen administration, care to prevent pressure ulcers, skin and suctioning care of the trachea, and full assistance in the basic activities of daily living had been admitted to a hospital within 5 km radius of Fukushima Daiichi Nuclear Power Plant and experienced Fukushima Daiichi Nuclear Power Plant accident. After the accident, the hospital faced a manpower shortage associated with hospital evacuation, environmental changes caused by infrastructure and medical supply disruptions, and the difficulty of evacuating seriously ill patients. As a result, antibiotics and suction care for aspiration pneumonia could not be appropriately provided to the patient due to lack of caregivers and infrastructure shortages. The patient died before his evacuation was initiated, in the process of hospital evacuation.ConclusionsThis case illustrates that decline in health care supply levels to hospitalized patients before evacuation during the acute phase of a radiation-released disaster may lead to patient fatalities. It is important to maintain the health care supply level even in such situations as the radiation-released disaster; otherwise, patients may experience negative health effects.

Flexible Ion Adsorption Electrodes Using Natural Zeolite and Rice Husk Charcoal for FEM-EK Treatment

The Fukushima Daiichi nuclear power plant accident happened after the devastating earthquake in the Pacific coastal area of Japan on 11 March 2011. After the accident, radioactive materials spread out over a wide area in Japan. Radioactive materials were retained on soil surfaces, causing environmental problems. Among the radioactive materials, cesium (137Cs) has a long half-life of 30.2 years, and it remains near the surface soil; therefore, it is necessary to remove soil contaminated by 137Cs. The contaminated soil layer of inhabited areas in Fukushima was already removed before April 2020. However, the remediation method of Cs with other radioactive materials needs further study, as the large quantity of contaminated soil is not easy to preserve. Electrokinetic (EK) treatment is one of the soil remediation technologies that utilizes EK phenomena at the interface between contaminated soils by transferring ions from the soil. We have developed a new type of EK method in which a cathode is placed on the surface of the soil and an anode is place inside the soil. By applying DC voltage in between the electrodes, the Cs ions can be removed from the contaminated soil. The removed Cs ions are gathered near to the cathode, and if the cathode can adsorb the Cs ions, then only the cathode needs to be preserved, solving the problem of storing a large amount of soil. We have been working to prepare a new type of cathode that can be effective in adsorbing Cs ions and at the same time easier to store and handle. We used natural zeolite and rice husk charcoal (kuntan) to prepare this electrode, which showed good potential for adsorbing Cs ions. The electrode showed flexibility, which is helpful for storing it in the same way as pasture rolls. However, the experiments were conducted in the laboratory with non-radioactive Cs; field experiments and observations are needed for practical applications of this method, as well as the new electrodes.

The development of a long-term predictive model of the changes in debris properties during interaction with aqueous solutions. Thermodynamic–kinetic modeling

This article presents a long-term predictive model of the properties’ changes of the molten core–concrete interaction (MCCI) debris material formed during the Fukushima Daiichi nuclear power plant (NPP) accident based on the available experimental data. For the development of the model, samples of MCCI debris were synthesized to represent the composition of the actual Fukushima debris. The samples' composition simulated different stages of ablation of the concrete basement beneath the NPP unit, i.e., various “concrete–corium” ratios. MCCI simulated debris samples (monoliths and powders) were exposed to aqueous solutions under the following conditions:1) continuous contact with water, i.e., no renewal of aqueous solutions (batch leaching experiments);2) periodic renewal of aqueous solutions by fresh ones (conditions simulating an open system with a constant inflow of fresh portions of aqueous solution).Experiments were performed under various conditions (temperature, pH) in two types of aqueous solutions: deaerated deionized and aerated deionized water. During the experiments, aliquots were taken to measure the concentrations of dissolved components (Ca, Si, Al, U, Zr, Fe, Ni, and Cr) in the aqueous solution.MCCI debris “aging” experiments were interpreted using kinetic curves and their relationship with physicochemical conditions (temperature, pH, type of aqueous solution). In this interpretation, the chemical processes of the MCCI debris components in water phase (dissolution and precipitation) were considered.The model was extended to 50 years and used to interpret debris aging experiments: (1) prediction of components’ releases into the aqueous phase caused by dissolution of solid phases, and (2) prediction of dusty secondary phase formation at the “debris–aqueous solution” interface.

Long-Term Contamination of the Arabian Gulf as a Result of Hypothetical Nuclear Power Plant Accidents

Long-term consequences of radionuclide contamination of the Arabian Gulf as a result of hypothetical accidents at the Bushehr and Barakah nuclear power plants (NPPs) were studied using a chain of models including the atmospheric dispersion model RIMPUFF, the marine compartment model POSEIDON-R, and the dose model. The compartment model POSEIDON-R is complemented by a dynamic model of the biota food chain that includes both pelagic and benthic organisms. The source terms for the hypothetical releases of the selected radionuclides (134Cs, 137Cs, 106Ru, and 90Sr) in the atmosphere were defined as a fraction of respective reactor inventories available in the literature. Conservative meteorological scenarios for the calculation of the initial depositions of radionuclides were selected. Because the Gulf is shallow, a significant portion of the reactive radionuclides (134Cs, 137Cs, 106Ru) remain in the bottom sediments and continue to contaminate water and benthic organisms for a long period of time. The annual dose due to the consumption of marine products can exceed 1 mSv, whereas the annual dose due to drinking the water from desalination plants is expected to be an order less. The contribution of elements to the dose depends on the type of reactor. This is manifested in differences between the contributions of different marine organisms to the dose.

Assessment of Radiation Risk Perception and Interest in Tritiated Water among Returnees to and Evacuees from Tomioka Town within 20 km of the Fukushima Daiichi Nuclear Power Plant.

In this study, we aimed to investigate radiation risk perception, mental health, and interest in tritiated water among evacuees from and returnees to Tomioka town, Japan, as well as to evaluate the intention to return (ITR) among evacuees living inside and outside Fukushima Prefecture. Of the 1728 respondents, 318 (18.4%) and 1203 (69.6%) participants reported living outside and inside Fukushima Prefecture, and 207 (12.0%) reported living in Tomioka. The ITR was not significantly different between those who lived inside and outside the prefecture among the evacuees. Similarly, there were no significant differences in radiation risk perception, mental health, and interest in tritiated water. However, the evacuees were independently associated with a motivation to learn about tritiated water (OR = 1.242, 95%Cl: 1.041-1.438, p = 0.016), reluctance to consume food from Tomioka (OR = 1.635, 95%Cl: 1.372-1.948, p < 0.001), and concern that adverse health effects would occur because of the Fukushima Daiichi Nuclear Power Plant accident (OR = 1.279, 95%Cl: 1.055-1.550, p = 0.012) compared to returnees, according to logistic regression analysis. Interestingly, the returnees were found to have better mental health but lower life satisfaction than the evacuees. These findings suggest the importance of ongoing risk communication about radiation exposure and tritiated water among residents regardless of their place of residency.

Message from the Winner

I would like to express my sincere gratitude for the MURAKAMI Suminao Award for Disaster Research 2022 and the JDR Award for the Most Contributory Reviewer 2022. It has been a great pleasure to serve on the editorial board for many years, and I have had the opportunity to talk with distinguished members of the editorial board who specialize in natural disasters such as earthquakes, volcanoes, and floods, which are completely outside my field of expertise, biology and medicine, and who have greatly broadened my perspective. The saying goes that disasters come just when you forget about them, but we have been in a situation recently where disasters come before we forget about them. There have been so many disasters: the panic that began with the discovery of cattle infected with bovine spongiform encephalopathy in Japan in 2001, the simultaneous terrorist attacks in the U.S. and the U.S. military invasion of Afghanistan around the same time, the poisoning of frozen dumplings made in China in 2007, the Tohoku Earthquake and Fukushima Daiichi Nuclear Power Plant accident in 2011, the COVID-19 problem that has continued from 2019 to the present, the invasion of Ukraine by Russia in 2022 and the resulting energy crisis and food shortages, as well as earthquakes, torrential rains, landslides, and typhoons that have occurred every year. The purpose of JDR, I believe, would be to stimulate research on these disasters, thereby providing a basis for the development of technologies for disaster prevention and control. In this regard, I have been concerned about the distance between science and technology: in the case of COVID-19, research on the causative virus, combined with messenger RNA vaccine technology, led to the fastest vaccine ever developed. On the other hand, the development of a cure has been slow, and the only treatment for pneumonia has been the old-fashioned one. Recently, antiviral drugs have been developed, but their efficacy has yet to be determined. There are many reasons for the distance between science and technology, and I hope that the research results published in JDR will play a role in reducing that distance.

Impact evaluation of typhoons and remediation works on spatiotemporal evolution of air dose rate in two riverside parks in Fukushima, Japan after the Dai-ichi nuclear power plant accident

This study elucidated the impacts of typhoon events and remediation works on the spatiotemporal evolution of the air dose rate in riverside areas frequented by residents. Spatial distribution of the air dose rate and radiocesium concentration in the sediments were measured in two riverside parks located near each other in Fukushima Prefecture, Japan, for 2015–2020. The air dose rates measured by walk surveys were interpolated using ordinary kriging to generate air dose rate maps, to facilitate a comparison between the results at different points in time during the measurement campaigns. After the typhoons that occurred during 2015–2018, the air dose rate near the riverside in one park decreased, but not in the other, because the erosion and sediment deposition patterns differed between them. This could be due to the presence of a dam upstream, which serves a flood mitigation function. However, the extreme event of typhoon Hagibis in 2019 dropped the air dose rates near the riversides in both parks. In contrast to the typhoon events which affected the riverside areas, remediation works such as decontamination undertaken during 2015–2019 reduced the air dose rates around the garden and lawn areas which are frequently used as recreational sites. Modeling the temporal evolutions in the air dose rates for the entire area of the riverside parks revealed that 35% of the reduction was caused by physical decay of radiocesium on average, 14% by vertical migration of radiocesium in the soil through precipitation, and 51% by the three typhoons and remediation works during 2015–2019. The contribution of 20% from the strongest typhoon Hagibis highlights the fact that floods resulting from large typhoons are effective in causing natural attenuation of air dose rates in riverside parks.

Comparison between external and internal doses to the thyroid after the Fukushima Daiichi Nuclear Power Plant accident.

To analyze the association between radiation dose and thyroid cancer after the 2011 Fukushima Daiichi Nuclear Power Plant (FDNPP) accident, external doses have often been used because of the difficulty to estimate internal thyroid doses individually due to the lack of human data. However, no evaluation has been made as to whether external dose is a good surrogate marker for internal thyroid dose individually. This study aimed at analyzing the relationship between external doses and internal thyroid doses estimated by recently developed methodology. For four municipalities affected by the accident, 200 individuals aged under 20 at the time of the accident per municipality were randomly selected, and their external and internal thyroid doses and their ratios were estimated individually. In a separate analysis, median and arithmetic mean values for external thyroid doses estimated for persons of 16 municipalities that included the above four were compared with those for previously estimated internal thyroid doses. The ratios of the median of internal thyroid dose to that of external thyroid dose in these 16 municipalities ranged from 0.56 to 13.8 for 15-year-old children and 0.91 to 21.1 for 1-year-old children. No consistent relationship between external and internal thyroid doses was found in all 16 municipalities. Thus, thyroid doses from both external and internal exposures should be used to analyze the association between radiation dose and thyroid cancer detection rates for persons who lived in Fukushima Prefecture at the time of the FDNPP accident. (240).

Identification and quantification of anomalies in environmental gamma dose rate time series using artificial intelligence

Gamma dose rate (GDR) monitors are the most widely used tool for continuous monitoring of environmental radioactivity. They are inexpensive to procure and operate, and generally require little maintenance. However, since no spectral information is available, the detection limit for irregularities is correspondingly high; A value around 20 nSv/h is often called out.By adding weather data to the GDR measurement and a sequence of machine learning algorithms, the anomaly detection sensitivity can be significantly increased while simultaneously decreasing the number of false positives. The algorithms were designed such that an integrated safety net prevents false negatives. First, the precipitation-induced GDR peaks from washed-out Radon progeny are removed by means of regression, provided that a check of the regression parameters shows sufficient agreement with past data at the measurement site. A neural network then calculates the expected value of the remaining GDR baseline for the prevailing conditions. Finally, an anomaly detection is carried out on the remainder between the expected and actual GDR baseline value. Extreme value theory is used to detect point anomalies, and hierarchical clustering of subsequences for slower processes. By combining the two detection methods, the full spectrum of irregularities is covered.The algorithms were implemented in Python and trained with real measurement data from the German GDR monitoring network. For verification, the data were enriched with results from JRODOS simulations of a nuclear power plant accident. Altogether, the presented methodology can lower the detection limit of irregularities to about 4 nSv/h, i. e. about a factor of 5 below the previous consensus value. The algorithm detects as well as quantifies the anomaly in the GDR, allowing for additional conclusions like potentially involved isotopes. Most important, it allows to refrain from the current practice of defining fixed alarming thresholds between the two contradicting goals of high sensitivity and low false alarm rate. Instead, it allows to transition to the more natural alarming on deviations from the expectation.

Emergency evacuation time model of nuclear power plant pedestrians

The construction of nuclear power plant is usually multi-phase. In the coexisting period of operation and construction, the types of pedestrian in nuclear power plant are complicated. Like Fukushima accident, nuclear power plant accident is dangerous and easy to cause mass panic. In order to improve the efficiency of emergency evacuation in nuclear power plant and accurately obtain the evacuation time of nuclear power plant pedestrians, a pedestrian evacuation time model is established. Firstly, by studying the general layout characteristics of nuclear power plant, nuclear power plant is divided into three areas, protected area, management area and construction area. Secondly, the pedestrian flow movement monitoring data of nuclear power plant are analyzed to obtain the pedestrian movement characteristics and speed-density curves of different locations(facilities) in different areas of the plant, which will provide data support for establishing the pedestrian evacuation time model of nuclear power plant. Thirdly, the evacuation time of nuclear power plant is divided into three parts: pedestrian reaction time, pedestrian walking time and pedestrian waiting time. The evacuation time model of nuclear power plant pedestrian is obtained by analyzing and modeling these three parts respectively. Finally, taking a nuclear power plant as an example, three types of evacuation areas are set up according to the layout characteristics and construction status of nuclear power plant. The model was used to calculate the evacuation time of different types of areas. Based on multi-agent pedestrian flow simulation method, emergency pedestrian flow simulation of three types of evacuation areas is obtained. The results of the model are compared with the simulation results, and it is found that the model has good matching in different nuclear power plant areas, which verifies the rationality and accuracy of the model.

Potassium applications reduced cesium uptake and altered strontium translocation in soybean plants

ABSTRACT After the Tokyo Electric Power Company’s Fukushima Dai-ichi Nuclear Power Plant accident in 2011, radioactive cesium (RCs) was released in greater concentrations than radioactive strontium (RSr) in the surrounding environment. Most of the countermeasures were developed to mitigate the RCs transfer from the soil to plants. However, to avoid what has happened after the Chernobyl and Mayak accidents, preventing the transfer of RSr from soil to plants should be a priority. Although the application of potassium (K) fertilizers is the most effective method for preventing agricultural crops from absorbing RCs in contaminated fields, this implementation increases the cost and labor requirements. Considering the preparedness for nuclear accidents, it remains unclear how this countermeasure will be affected if RCs and RSr are released simultaneously. We aimed to explore the effect of K applications on cesium (Cs) and strontium (Sr) uptake and their interaction with and correlation to other elements in the soybean plants and soil. The field experiments were conducted in Fukushima Prefecture, Japan, using different K applications (i.e., no, normal, and high K applications). The dry weight and mineral concentrations of K, Cs, Sr, calcium (Ca), magnesium (Mg), and nitrogen (N) concentration in plants and exchangeable K (ExK), exchangeable Cs (ExCs), exchangeable Sr (ExSr), exchangeable Ca (ExCa), exchangeable Mg (ExMg), NH4+ (ammonium), and NO3- (nitrate) concentrations in the soils were evaluated. This study revealed that K application reduced Cs, Ca, and Mg uptake but did not affect the ExSr, ExCa, and ExMg concentrations in the soil and did not change the uptake of Sr. On the other hand, K concentration of the plant especially at later growth stage, which indicates re-translocation of Sr was negatively regulated by K concentration.

Distinctive physical insights driven from machine learning modelling of nuclear power plant severe accident scenario propagation

The severe accident scenario propagation studies of nuclear power plants (NPPs) have been one of the most critical factors in deploying nuclear power for decades. During an NPP accident, the accident scenario can change during its propagation from the initiating event to a series of accident sub-scenarios. Hence, having time-wise updated information about the current type of accident sub-scenario can help plant operators mitigate the accident propagation and underlying consequences. In this work, we demonstrate the capability of machine learning (Decision Tree) to help researchers and design engineers in finding distinctive physical insights between four different types of accident scenarios based on the pressure vessel's maximum external surface temperature at a particular time. Although the four accidents we included in this study are considered some of the most extensively studied NPPs accident scenarios for decades, our findings shows that decision tree classification could define remarkable distinct differences between them with reliable statistical confidence.

Using ARGOS to simulate radioactive dispersion in the atmosphere from Fangchenggang nuclear power plant to Viet Nam

In this study, ARGOS software was used to simulate the atmospheric radioactive emissions from Fangchenggang nuclear power plant to Viet Nam. The simulated cases are hypothetical accidents with hypothetical source terms equivalent to level 6 of the International Nuclear and radiological Event Scale (INES). The results show the possibility of using ARGOS in simulating atmospheric dispersion, assessing radiation dose to humans from the Fangchenggang nuclear power plant accident to Viet Nam in some accident situations. Furthermore, the obtained results contribute to forecasting and supporting emergency response when an accident occurs in nuclear power plants.

A Numerical Model to Simulate the Transport of Radionuclides in the Western Mediterranean after a Nuclear Accident

The transport of radionuclides in the western Mediterranean Sea resulting from hypothetical accidents in a coastal nuclear power plant, and in a vessel with nuclear power or transporting radioactive material, was assessed with a Lagrangian model developed for this kind of accident assessment. Water circulation was obtained from the HYCOM global ocean model. The transport model was developed in spherical coordinates and includes advection by currents, three-dimensional turbulent mixing, radioactive decay, and radionuclide interactions between water and seabed sediments. Age calculations are included as well. A dynamic model based on kinetic transfer coefficients was used to describe these interactions. Mixing, decay, and water/sediment interactions were solved applying a stochastic method. Hypothetical accidents occurring at different moments were simulated to investigate seasonal effects in the fate of radionuclides. In addition, simulations for different radionuclides were carried out to investigate the effects of their different geochemical behaviours. Thus, in the case of a coastal release, 137Cs is transported at long distances from the source, while 239,240Pu stays close to the release point due to its strong reactivity, most of it being quickly fixed to the seabed sediment. In deep waters, in case of a surface release, 239,240Pu spreads over larger areas since sediments are not reached by radionuclides.

Relationship between haematological data and radiation doses of TEPCO workers before and after the FDNNP accident.

We evaluated the correlation between radiation dose and the medical examination data of Tokyo Electric Power Company Holdings, Inc (TEPCO) employees working during the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident in 2011. This study included 2164 male TEPCO workers who received periodic medical examinations from March 2006 to January 2013. First, we conducted log-linear regression analyses using the haematological data of 585 emergency workers and confounding factors to examine the effect of internal radiation exposure in March 2011. Since external radiation exposure was a major influence, we then evaluated the correlation between both internal and external radiation dose and the haematological data of 1801 emergency workers and confounding factors before and after the accident. Among 585 workers, internal radiation exposure in March 2011 alone was mainly due to thyroid doses (0.1-10Gy) but not to bone marrow (BM) doses (0.01-1mGy). Compared to before and after the accident, we found that the levels of monocytes, eosinophils (Eos) and basophils increased slightly, whereas the frequency of smoking and alcohol consumption decreased substantially. External dose exposure was positively correlated with haemoglobin (Hb), red blood cell and Eos but negatively correlated with age, haematocrit and frequency of alcohol consumption. Among these variables, Hb exhibited the strongest correlation with external dose. Regarding the correlation with Hb, although there is a possibility that confounding factors other than exposure were not evaluated, our findings on emergency workers can serve as a reference for the evaluation of health conditions during the emergency period of future nuclear-related accidents.

No evidence of thyroid consequences in seven nuclear workers at the Tokyo Electric Power Company Fukushima Daiichi Nuclear Power Plant accident: 10-year follow-up results of thyroid status.

Seven emergency nuclear workers, who had internal exposure due to an intake of radionuclides, mainly I-131, during the emergency response operation in March 2011, after the accident at the Tokyo Electric Power Company (TEPCO) Fukushima Daiichi Nuclear Power Plant (FDNPP), visited the National Institute of Radiological Sciences (NIRS) outpatient clinic for medical evaluation. They were followed up after their first visit for 10 years. The estimated committed equivalent doses to the thyroid were distributed between 3.2 to 1.2 × 10Sv. This group thought to be received highest exposure at the accident. None of the workers had symptoms related to abnormal thyroid function. The examinations, including thyroid function tests and ultrasound, detected no abnormalities related to radiation exposure. However, there is a need for continuous monitoring of their thyroid status for longer periods in the future.

The Predictors of Unsafe Behaviors among Nuclear Power Plant Workers: An Investigation Integrating Personality, Cognitive and Attitudinal Factors.

Unsafe behaviors, such as violations and human errors, have long been recognized as the main causes of accidents in nuclear power plants (NPPs). However, personal factors that influence unsafe behaviors among NPP workers have not been well examined, especially in an integrated model. This study proposes an integrated contextual mediated model to examine personality, cognitive and attitudinal predictors of unsafe behaviors among commissioning workers at NPPs. The model was verified using structural equation modeling technique with survey data from 177 commissioning workers in two Chinese NPPs. Results show that personality traits (i.e., conscientiousness, neuroticism, openness and agreeableness), executive function and safety attitudes exerted significant effects on unsafe behaviors. In addition, the effects of agreeableness and executive function were partly mediated by safety attitudes. Both conscientiousness and neuroticism indirectly influenced unsafe behaviors through the mediating role of executive function. The findings shed light on the design of evidence-based interventions for safety performance in NPPs.

Thermophysical properties of molten (Fe2O3)0.95-(SiO2)0.05 measured by aerodynamic levitation

In order to establish an evaluation method/numerical simulation for nuclear reactor safety under severe accidental conditions, it is necessary to obtain the physical properties of the relevant molten materials at very high temperatures. In particular, the reaction/interaction between the melt of stainless-steel oxide originating from the nuclear reactor component and the composition of structural concrete is an important phenomenon in terms of understanding of the progress of severe accidents in nuclear power plants and the planning/installation of equipment/devices as countermeasures. The installation of a core catcher is one possible countermeasure to safely terminate a severe accident. For this to work a sacrificial material is placed in the core catcher to increase the fluidity of the molten material. Iron oxide (Fe2O3) is considered a promising candidate. In this study, thermophysical properties such as the density and the viscosity of a (Fe2O3)0.95-(SiO2)0.05 mixture were obtained using the aerodynamic levitation method. The chosen composition is representative for the Molten-Core-Concrete-Interaction at early stages of a severe accident event. Although partial Fe2O3 changes to Fe3O4 during the experiment, this composition change would occur under the actual severe accident conditions. The physical property values of the (Fe2O3)0.95-(SiO2)0.05 mixture were almost the same as those of Fe2O3 obtained in an earlier study. Therefore, it can be concluded that the fluidity of Fe2O3 is not significantly affected in the early stages of a severe accident whereby small amounts of SiO2 (approximately 5 mol. %) are dissolved into Fe2O3.

Evaluation of indoor air dose rate based on Cs‐137 depth distribution in surrounding artificially paved surfaces surveyed 10 years after the Fukushima Daiichi nuclear power plant accident

AbstractUnderstanding residual radioactive contamination state and the resulting radiation environment is vital before reconstructing the lives of residents in areas affected by nuclear power plant accidents. In this study, we surveyed the depth profiles of Cs‐137 in three artificially paved ground surfaces: impermeable asphalt, permeable asphalt, and concrete, in areas affected by the Fukushima Daiichi Nuclear Power Plant accident after a period of 10 years and analyzed the gamma‐ray air dose rate distribution in a two‐story wooden house model surrounded by different ground surfaces using the Particle and Heavy Ion Transport code System of the Japan Atomic Energy Agency. The air dose rate distribution tendencies within the building for different surrounding ground surfaces were clarified by analyzing the transport of gamma rays emitted from the Cs‐137 in the ground. Moreover, the shielding effect of an ordinal concrete fence on the indoor air dose rate was analyzed. The analysis showed that the indoor air dose rate was higher in an environment with artificial pavement than in that with a soil surface, and even a simple measure, such as installing an ordinal concrete fence, could significantly reduce indoor radiation dose rates.

CHARACTERISTICS OF NON-RENAL NORMOCALCIEMIC HYPERPARATHYROIDISM IN THE CHORNOBYL NPP ACCIDENT SURVIVORS.

to assess the hormonal and metabolic disorders in the Chernobyl nuclear power plant (ChNPP) accident survivors (AS), having got secondary normocalcemic non-renal hyperparathyroidism (HPT) in the late period upon exposure to ionizing radiation (IR). The routine clinical, anthropometric, instrumental (thyroid and parathyroid diagnosticultrasound), laboratory (biochemical, hormonal), statistical methods were applied. In both prospective (n = 48, control group n = 19) and retrospective studies the data of 2,234 subjects including 1,372 irradiated adults (862 non-irradiated persons in the control group) were evaluated. Clinical consequences of exposure to IR on the endocrine system were evaluated in ChNPP AS. High prevalence of vitamin D lack or deficiency was established retrospectively in 81.8 % of the ChNPP AS and in 89.5 % of the control group subjects. In general, there was neither effect of exposure to IR on the vitamin D status in study subjects, nor any difference between the study groups. According to diagnostic ultrasound patterns the parathyroid hyperplasia was diagnosed in 629 cases (28.2 %). Among the ChNPP AS it was found in 32.7 % of cases (n = 450) vs. 20.7 % (p > 0.005) in the control group (a 1.6-fold difference). HPT diagnosed as serum parathyroid hormone content > 65 ng/ml was diagnosed in 123 cases (21.1 %) i.e. in almost every fifth person. Increased serum level of parathyroid hormone was found in the 94 ChNPP AS and in 25 persons of the comparison group. In other words, the frequency of HPT was 23.7 % among the AS being significantly more than in the comparison group (13.2 %, p < 0.005). Frequency of normocalcemic non-renal HPT was slightly different by years of observation with a trend to the year-by-year increase. High prevalence of vitamin D lack or deficiency was established in the ChNPP AS, being however independent of exposure to IR. Frequency of parathyroid hyperplasia/adenoma was 1.6 times higher in the irradiated subjects than in persons of the control group. Annual increase in frequency of the non-renal normocalcemic HPT was also revealed reaching nowadays 23.7 % among the AS, which is significantly higher than in the comparison group.