Modelling of hydrodynamic and solute transport with consideration of the release of low-level radioactive substances

When nuclear power plants are dismantled, only a small portion is heavily contaminated with radioactivity and must be stored in a repository. The remaining material, mainly concrete rubble (construction waste), is decontaminated if necessary and can be stored in conventional surface landfills after clearance. The focus of this work is on the modelling of such landfills and the radioactive substances during raining events. The influence of the heterogeneous nature of the construction rubble should also be investigated. The simulation environment DuMux, mainly developed by our institute, is used to compare different modelling approaches. It follows a previous work by Merk (2012). The research work is supported and accompanied by the Federal Office for Radiation Protection (BfS). Parts of the research initiatives of the BfS in the area of clearance of materials with negligible radioactivity are also presented.

Safety Culture in Handling Radioactive Materials for Radiation Practitioners: A Review

This paper reviews the safety culture in handling radioactive sources. Safety culture refers to how safety is addressed and communicated in the workplace. It encompasses the attitudes, beliefs, perceptions, and values of all employees in an organization in relation to safety. A good safety culture can be promoted by management through commitment to safety, realistic practices for handling hazards, continuous organizational learning and concern for hazards shared across the workforce. The radioactive substances used should comply with the following characteristics where radiotoxicity must be as low as possible, short-living isotopes are preferred than long-living ones and the amounts used must be kept to a minimum. Therefore, the ‘As Low As Reasonably Achievable’ (ALARA) principle was applied that based on the minimization of radiation doses and limiting the release of radioactive materials into the environment by employing all reasonable methods. Besides that, the ALARA principle is an integral part of all activities that involve the use of radiation or radioactive materials and can help prevent unnecessary exposure as well as overexposure. The three major ALARA principles to assist with maintaining doses are time, distance and shielding. It takes a whole team effort to successfully implement the ALARA in safety culture while doing routine element of working in handling radioactive materials.

Decontamination of Victims in the Event of a Radiation Accident at the Stages of Provision Medical Care

Purpose: To summarize and analyze the results of research and practical recommendations on the decontamination of victims in the event of radiation accidents, including taking into account the authors’ experience gained in the initial period of the Chernobyl accident (April – August 1986) and in other local radiation accidents (incidents), as well as during emergency exercises. Results: The indications for carrying out decontamination and the technique of its implementation were considered, a comparative assessment of the effectiveness of skin decontamination agents was presented. Recommendations were formulated for determining the priority (urgency) of carrying out decontamination, depending on the level of external radioactive contamination of the victims. Criteria, rules and methods for carrying out decontamination were proposed for use in relation to the practice of medical and hygienic measures at the stages of medical evacuation (accident site, enterprise health center, enterprise sanitary inspection department, triage site, hospital admission department). The features of decontamination of victims with combined radiation injuries and contaminated wounds (burns) were considered, issues of ensuring the radiation safety of medical personnel who provide assistance to victims are touched upon. Conclusion: Timely and correctly performed decontamination reduces the exposure of the skin, prevents the entry of radioactive substances into the body and the transfer (spread) of radioactive substances to the subsequent stages of medical evacuation. The main criteria for the urgency (priority) of carrying out decontamination are the levels of radioactive contamination of the skin, contamination nature (radionuclide composition, physicochemical form, etc.) and the presence of victim’s skin lesions (wounds, burns). Decontamination of victims with high levels of radioactive contamination should be considered as a part of the first and subsequent emergency health care and should be carried out as prescribed or with the direct participation of a healthcare professional. At the stages of medical evacuation, decontamination can be carried out if the victim’s condition is stabilized. In the case of a serious condition of the victim, the priority is evacuation to a hospital, while in the prehospital period, as a rule, only partial decontamination of skin areas with high levels of contamination can be carried out. The procedure and rules for decontamination, including the use of skin decontaminating agents, should be reflected in the action plans of the personnel of radiation hazardous enterprises and the plans for medical support of medical units of the FMBA of Russia.

Аnalysis Catalytic Hydrogen Recombiner Capacity Calculation Taking into Account Conditions Inside Sealed Enclosure of Containment Safety System of Nuclear Power Plants with Water-Water Energetic Reactor

Localizing safety systems are provided to contain radioactive substances in an accident and attenuate ionizing radiation at a modern nuclear power plant. Together with radioactive substances, hydrogen is also retained, which is formed during the decomposition of the primary coolant. The accumulation of hydrogen in the presence of oxygen from the atmosphere in the accident localization zone carries the danger of the formation of flammable and explosive concentrations of these components. Nuclear power plant (NPP) deigns with water-water energetic reactor (WWER) provides for a hydrogen removal system including passive catalytic hydrogen recombiners. The device capacity is confirmed experimentally under reference conditions (lean air-hydrogen mixture, pressure and temperature close to normal, no interference with gas exchange). Capacity is an important safety parameter. In the event of an accident, conditions inside the ealed enclosure of the localizing system of NPP with WWER can differ from the reference ones and affect the capacity. On the basis of calculations, the operation of recombiners with lack of oxygen and with hindered gas exchange has been investigated in the paper. The decrease in capacity with lack of oxygen reaches 50 %, which is mainly caused by an increase in underburning. Compared to the reference conditions, the effect is more pronounced in the event of an accident – 60–70 %. The hindered gas exchange is modeled by a decrease in the height of recombiner traction channel. This case can be reduced to the placement of the device in cramped conditions and the effect of the atmosphere speed inside the enclosure. Regardless of the hydrogen concentration, the operating characteristic of the device remains linear, with a two-fold decrease in height leads to a decrease in capacity by 20 %. The results can be used to substantiate the safety of NPPs with WWER and to review on the safety subtantiation of power units.

Nature of Relationships Between Atmospheric Electricity Parameters at Ground Surface and Air Ionization on the Basis of Nuclear Accidents in Power Plants and Weapons Tests

In this work we present an analysis of selected atmospheric electricity parameters, measured at the Geophysical Observatory in Świder (near Warsaw, Poland), in a review of the major events that resulted in the release of a significant amount of artificial radioactive substances in the Earth’s atmosphere: the radioactive accident in Fukushima, Japan, beginning 12 March 2011, followed by the 9.0 earthquake and tsunami; Chernobyl disaster (27 April 1986); and nuclear weapons testing (1958–1965). The physical mechanisms of the impact of radioactive sources on the electrical parameters of the atmosphere are analyzed. The formation of free charge (small ions, represented by electric air conductivity) and bound-induced charges (measured vertical electric field and current) by radioactive aerosol and cloud nuclei were taken into account. The values of electric field Ez, atmospheric air conductivity λ, and aerosol concentrations measured at a certain site depend on the time and space location of the released radioactive materials in relation to the measurement site and the meteorological situation. A frontal inflow of air masses containing radioactive substances may be noticeable at a large distance from the atmospheric electricity measuring site in fair weather conditions (Chernobyl disaster). Atmospheric precipitation plays a very important role in the transport of radioactive substances to the ground level (nuclear weapons testing). The relationship between the ionospheric potential Vi and the electric field near ground level Ez resulting from the Global Electric Circuit (GEC) concept for the presence of a strongly ionized air layer in the lower stratosphere and the ground level was disturbed in nuclear weapons testing time. The aim of this work is a qualitative characterization of discussed events. Future modeling works are needed to investigate the dependence of quantitative GEC parameters in situations of global or regional high air ionization. For this purpose, available measurements of recorded atmospheric electricity parameters will be used.

RADIATION RISK MANAGEMENT WHEN HANDLING RADIOACTIVE SUBSTANCES AND MATERIALS

The system of personnel protection from ionizing radiation in laboratories and industrial premises, where they work with radioactive substances and materials has been considered. A logical scheme in the form of a tree of failures and mathematical expressions for calculating the reliability of the protection system are presented. The coefficients of the influence of individual elements on the reliability of the system are determined. A quantitative analysis of the coefficients of influence made it possible to identify the most significant and most unreliable elements (“weak links”). In order to replace the “weak links”, a list of alternative elements and possible combinations of elements in the protection system has been compiled. Two risk management strategies are proposed. The first strategy involves minimizing the likelihood of failure of the protection system. The second is to minimize the cost of its operation. The possibility of achieving a positive effect has been demonstrated in both cases.

On the Regulation of Liquid and Airborne Radioactive Discharges of the Industrial Enterprises that do not Use Atomic Energy

In accordance with the legislative framework of the system for regulating liquid and airborne discharges of radioactive substances into the environment in force in the Russian Federation, this system is equally designed to regulate discharges of the radionuclides of both artificial and natural origin. The mechanisms of radiological impact of the discharges of natural origin radionuclides on the environment and population do not have any specificity in comparison with the ones of artificial origin radionuclides. Nevertheless, to date, the law enforcement of the Russian system for regulating discharges of the radioactive substances is applied only in relation to the discharges of the radionuclides of artificial origin carried out by nuclear facilities. At the same time, regulation of the discharges of natural origin radionuclides, in accordance with the safety standards of the International Atomic Energy Agency, is the best practice in the field of environmental protection, and the levels of radiation exposure, which characterize such discharges, are not low enough to be neglected. Regulation of the discharges of natural origin radionuclides is provided for in the norms of the European Union and is practically applied in the number of countries of the European Union, where the legislation provides for the regulation of activities, in which the raw materials containing radionuclides of natural origin are used, and the types of economic and other activities subject to this regulation are determined. The Russian system of regulation of discharges of the radioactive substances into the environment is built on the same basic principles and criteria that underlie foreign regulation systems, and which are recommended by the International Atomic Energy Agency. The regulatory and methodological base formed to date in the Russian Federation contains all the required legal mechanisms for the regulation of discharges of the radioactive substances from nuclear facilities, is based on the best international practices and fully complies with the standards of the International Atomic Energy Agency.