Comparative Analysis of Paired Correlations Structure Between Psychological Scales in Relation to Groups of Different Sizes

Purpose: To propose a procedure for comparative analysis of correlation relationships structure between psychological scales in samples of different sizes. Material and methods: A procedure of comparative analysis of correlation relationships structure between psychological indicators in groups of different sizes based on the «zet» method of R. Fisher is proposed. To illustrate the method, data from psychodiagnostic surveys of the nuclear power plant (NPP) personnel who worked in normal conditions and the personnel of the Chernobyl NPP at four different stages of aftermath activities in 1986–1987 were used. All the subjects performed the Minnesota Multiphasic Personality Inventory (MMPI); the results of each of the groups were subjected to a correlation analysis using the Pearson method. The analysis took into account average (0.5 ≤ r < 0.7) and strong (r ≥ 0.7) correlations. Results: Using the example of a number of psychodiagnostic examinations of the Chernobyl NPP personnel at various stages of aftermath activities, it is shown that the structure of correlation relationships between the MMPI scales can reflect the peculiarities of mental adaptation of professional teams working in regular and extreme conditions. It was shown that in the aftermath process by March–April 1987, the number of medium and strong pairwise Pearson correlations between the clinical MMPI scales increased. This fact apparently indicates that during this period, the NPP personnel were characterized by the simultaneous activation of various mechanisms of intrapsychic adaptation. The core of the correlation pleiad consisted of scales 1, 2, 7, and 8. Such a multidirectional reaction to the aftermath stressors was accompanied by a statistically significant increase in almost all clinical scales (except scale 6) of the average MMPI profile in comparison with the control group. The absence of stable correlations of clinical scales with the F scale indicates that the marked increase in the MMPI profile was not associated with a tendency to aggravation. By the period of November–December 1987, the hypochondria scale occupied a leading place in the correlation pleiad of the MMPI indicators of the Chernobyl NPP personnel, the number of its significant connections with other clinical scales (2, 3, 7 and 8) reached four. Apparently, the mechanism of anxiety somatization at that time could be considered as a syndrome-forming factor and taken into account when planning rehabilitation and health measures. Conclusion: The use of the proposed method of the strength standardization of pairwise correlation relationships between the MMPI scales allowed us to legitimately compare these indicators in groups that differ significantly in number. The chosen representation form of correlations facilitates the analysis of their structure.

Radiation Safety During the Construction of the «Sarcophagus» («Shelter» object) at the 4-th Unit of the Chernobyl Nuclear Power Plant in May-November 1986

This year marks the 35-th anniversary of the events related to the liquidation of the consequences of the accident at the Chernobyl nuclear power plant (Chernobyl NPP) and their most important stage - the closure of the destroyed 4-th power unit with a special structure, which was initially called the «Sarcophagus» (later the «Shelter» object). This article presents information about the period May-November 1986 in the aspect of radiation safety of the builders of this unique facility.

UNORGANIZED AIR RELEASES WITH RADIOACTIVE AEROSOLS FROM THE NEW SAFE CONFINIMENT OF CHNPP INTO THE ENVIRONMENT

The New Safe Confinement (NSC) of the Chernobyl NPP, which isolates the destroyed reactor and the “Shelter Object” from the environment, is not airtight, so the problem is the lack of information on the flow of unorganized air with radioactive aerosols outside the NSC. This work presents computational model of the hydraulic state of the NSC, which allows to determine these flow rates through the leaks in the shells and building structures under the walls of the NSC. In addition to the developed model, the NSC hydraulic state model, created by neural network technology, was tested, which showed similar results and much higher computational performance, which allows its use for analysis and prediction of NSC`s hydraulic state in real time.

Radionuclides contamination of leaves of woody plants growing within the CHNPP cooling pond

The data on the state of radioactive contamination of leaves of plants growing directly on the territory of the drained part of the cooling pond of the Chernobyl NPP are presented. It was shown that the main source of contamination is the root intake of radionuclides (137Cs and 90Sr). This contamination is larger in previously drained areas compared to recently exposed ones. Hot particles were found on the leaf surface by autoradiography. Their total β-activity is a few percent of the total pollution. Possible sources of hot particles – resuspension in the air in the region of the northern part of the cooling pond are discussed.

Analysis of the Dynamics of Mortality of Liquidators of the Consequences of the Accident at the Chernobyl NPP - Workers of the Atomic Industry of Russia

Purpose: Assessment of the health of persons working under the influence of certain adverse environmental factors. Material and methods: The work includes all male liquidators registered in the Sectoral Register of persons exposed to radiation as a result of the accident at the Chernobyl nuclear power plant. This is about 18.5 thousand people. More than half of them have a verified dose load, all of which were exposed to radiation while working in the 30-km zone of the Chernobyl NPP. At this stage of the study, estimates were obtained for the corresponding retirement intensity function for two cohorts of liquidators – 1986 and subsequent years of work.In order to assess the dynamics of the age-specific mortality of the liquidators, the data for the years 2000 and 2014 are considered. It did not make sense to take earlier years due to the relatively young age of the liquidators at that point in time. The second estimate is related to exactly 15 years – half the entire period of observation of the register. 2014 turned out to be more preferable compared to 2015 due to the fact that it was in 2014 that a significant number of people were deregistered and thus dropped out of consideration. Empirical analysis methods are used – survival curves are considered (data such as the lifetime) both in terms of morbidity and mortality. And a comparison is made of the curves obtained in different rank groups. For fitting curves, risk functions of various parametric distributions constructed using the likelihood function can be used. The main problem of this analysis is a large number of censored data at this stage of the study. Results: The death rate of the liquidators differs significantly from the death rate of the male population of the Russian Federation, however, this difference decreases with time, primarily due to a decrease in the death rate of the population in the Russian Federation. If the trends in the dynamics of age-specific mortality in the Russian Federation correspond to global standards, which corresponds to a positive dynamic, the dynamics of the age-specific mortality of the liquidators is paradoxical, which primarily concerns the cohort of liquidators of 1986. The weather smoothed mortality of the liquidators of 1986 exceeds that calculated for all the liquidators of the register, which may indicate the presence of some additional factors determining the health of this group of persons. By the years 2007–2010, a significant increase in the slope of the mortality curve is observed as a sign of the cohort selection, relegation of the weaker ones first. Using the Kaplan –Meier method, survival curves for cohorts were constructed, and the presence of significant differences in their mortality was shown.

Change in plutonium sedimentation fluxes into the bottom sediments of the Sevastopol Bay before and after the Chernobyl NPP accident

The Sevastopol Bay located in the northern Black Sea was exposed to radioactive contamination by anthropogenic radionuclides, inter alia 238,239+240Pu, and to other types of anthropogenic load. One of them was the construction of breakwaters at the bay mouth in 1975–1986, which resulted in a change in the hydrological regime. The aim of this work was to assess the change in 238Pu and 239+240Pu sedimentation fluxes into the bottom sediments of the Sevastopol Bay mouth in the period before and after the Chernobyl NPP accident (1962–1986 and 1986–2013, respectively). Plutonium in sediments was determined by the radiochemical method, followed by measurement of the activity of radioisotopes with an alpha spectrometer. The sedimentation rate was defined by geochronological dating of sediment layers, accessing the change in 238Pu/239+240Pu activity ratio in the bottom sediment core. Then, the mass accumulation rate in the bottom sediments was calculated. As established, in the period after 1986, the mean annual sedimentation rate and mass accumulation rate in the bay mouth increased by 63 and 70 %, respectively. Assessment of 238,239+240Pu sedimentation fluxes during two research periods showed as follows: after 1986, 238Pu and 239+240Pu fluxes into the bottom sediments increased by 150 and 49 %, respectively. The increased 238Pu percentage in plutonium sedimentation flux after 1986 indicates Chernobyl origin of plutonium in the bottom sediment layers above 11 cm. In the post-Chernobyl period, the cumulative effect of an increase in 238,239+240Pu sedimentation flux into the bay mouth results both from an increase in the radioactive fallout intensity after the Chernobyl NPP accident and an effect of breakwaters on the regime of sedimentation processes in the water area (an increase in the mass accumulation rate).

Radiological consequences and lessons of the Chernobyl NPP and «Fukushima-1» NPP radiation accidents

35 years have passed since the Chernobyl NPP accident, 10 years – since the «Fukushima-1» NPP accident. At the present time extensive activities on the remediation of the consequences of two major large-scale radiation disasters are performed in the Belorussia, Russian Federation, Ukraine, and Japan. Releases of radiologically significant radionuclides after the Chernobyl NPP accident correspond to 14 exaBecquerel – higher up to an order of magnitude compared to 3 emergence power units of the «Fukushima-1» NPP. The significantly lower release rate and deposition of 80% of the radionuclides released into the atmosphere on the surface of the Pacific Ocean lead to lower up to several orders of magnitude radioactive contamination of the Japanese territory compared to the territories of the former USSR and neighboring countries after the Chernobyl NPP accident. Collective dose to the public due to the Chernobyl NPP accident is higher up to several orders of magnitude compared to the dose to the Japanese population after the «Fukushima-1» accident. No statistically reliable long-term medical consequences are expected for all groups of the Japanese public, additionally exposed due to «Fukushima-1» accident. 134 emergency workers have developed acute radiation sickness due to the Chernobyl NPP accident. Emergency workers with doses higher than 150 mSv had increased radiation-induced morbidity with leukemia and solid cancers. Among the individuals, that were kids or adolescents in the exposure period after the Chernobyl NPP accident and residing on the territories of Belorussia, Ukraine and four most radioactively contaminated regions of the Russian Federation, morbidity with thyroid cancer is increase by a factor of 10 compared to the pre-accidental levels. The following lessons of the Chernobyl NPP and «Fukushima-1» NPP can be derived: faults in the NPP design and lack of response after the recognition of the faults; lack of timely full-scale prophylactic with iodine; unjustified resettlement of the residents of the radioactively contaminated territories several years after the accident.