NPP Risk Assessments Results Dependence Study on the Composition of the Population Living Around the NPP (on the Example of Rostov and Kalinin NPP) S.S. Zolotarev1, M.A. Berberova2 zolotarev@phystech.edu|maria.berberova@gmail.com 1 Moscow Institute of Physics and Technology, Moscow, Russia; 2 International Nuclear Safety Center, Moscow, Russia Nuclear power plants, being complex technological systems, represent a source of increased risk, in particular, a specific risk of radiation exposure. Obtaining quantitative assessments of radiation risk is critical for risk reduction and accident prevention. Existing methods for assessing radiation risk do not take into account the influence of external factors, such as population composition, geographical features, anthropogenic environmental changes, etc. The result of the risk analysis is the assessment of physical and economic indicators for the Rostov and Kalinin NPPs, taking into account the age composition of the population, as the most significant parameter. Based on a comparison of the estimates obtained with the results without taking into account the age distribution, recommendations are given on the use of adjusted estimates when developing measures to reduce risk and mitigate the consequences for the most sensitive age groups of the population (1-12 years). The objective of the work is to modify the methodological approach to the calculation of radiation risk indicators of the population, taking into account the age composition and the practical application of the formulas for assessing the physical and economic indicators of damage to real objects. Keywords: risk, population, NPP, dose, age composition, damage, safety. established a unified approach to the assessment of risk 1. Introduction indicators for NPPs with reactors of various types, recommendations for organizing and conducting risk Radiation plays a huge role in the development of civilization assessments, and documenting the results of risk assessments in at this historical stage. Due to the phenomenon of radioactivity, accordance with the requirements of the safety data sheet. a significant breakthrough was made in the field of medicine and In 2007, the Methodological Guidelines (MG) “Rapid in various industries, including energy. But at the same time, Assessment of Doses to the Population in Case of Radioactive negative aspects of the properties of radioactive elements became Pollution of the Territory by Air” [4] were developed, defining more pronounced: it turned out that the effects of radiation on the methods for calculating the level of exposure to members of body can have tragic consequences. This fact could not pass by various population groups (depending on age, profession, type of the attention of the public. And the more it became known about dwelling). In the risk assessment for safety data sheets of Russian the effect of radiation on the human body and the environment, NPPs, these MGs were not included. the more controversial became the opinions about how much The study was based on works [5, 6] implemented by radiation should play in various spheres of human activity. Rosenergoatom Concern JSC in the framework of the Over the past 20 years, substantial work has been done to preparation of safety data sheets for Russian NPPs (in particular, reduce the risks and mitigate the effects of man-made Rostov and Kalinin NPPs). The risk assessment of an accident at emergencies. In this regard, nuclear power plants remain the a nuclear power plant is carried out according to the procedure source of radiation around which the most intense disputes are for conducting a Level 3 PSA using the FOOD computer conducted, although they currently contribute very little to the program, which allows the calculation of radiation doses to total exposure of the population. Negative public opinion on personnel and the public at various distances from the source of nuclear power can be justified by the fact that the solution of the radionuclide release. The probabilities of the occurrence of problems of NPP risk analysis is carried out in conditions of various emergency scenarios are calculated according to the MU considerable uncertainty. Moreover, despite the low probability for conducting risk analysis of hazardous production facilities of the most dangerous accident, the radiation effects may be [7]. Physical indicators of the risk of radiation exposure on significant and require close attention. personnel and population are estimated in accordance with [8]. Thus, the task of clarifying the risk assessment of radiation According to [8]: exposure to the population, taking into account the age criterion 1. The radiation sources that create are not considered: as the most significant, becomes more relevant and determines - individual annual effective dose of not more than the significance of this study. 10 µSv; 2. Review of risk assessment methods - collective effective annual dose of not more than 1 person-Sv; This chapter provides an overview of risk assessment 2. It is accepted that radiation in a collective effective dose methods. The chapter consists of two sections. Section one of 1 man-Sv leads to potential damage equal to a loss of provides an overview of risk assessment methods, describes the 1 man-year of life; terms and definitions required for risk assessments, and discusses 3. To assess the harm to health from radiation in small the main quantitative risk indicators. Section two presents the doses, both the effects of irradiation of individual organs methodology for calculating the level of exposure for different and tissues of the body, differing in radiosensitivity, and age groups of the population. the irradiation of the whole organism as a whole are taken into account. The averaged value of the risk 3. Risk assessment methodology coefficient used to establish dose limits for personnel In 2004, by order of the Minister of Emergencies of Russia and the public was assumed to be 0.05 1 / Sv. [1], a typical safety data sheet of a hazardous facility was The distribution of radionuclides in the environment from the approved. On its basis, a safety data sheet was developed for the emission source to the direct impact on humans or the critical (dangerous) object of Rosatom [2]. environment can be divided into three areas: To solve the problems of risk assessments in 2004, it was - Emissions to the atmosphere; decided to develop a “Methodology for assessing risk indicators - Liquid discharges into rivers, reservoirs or seas; for managing the safety of critical (hazardous) facilities of - Disposal of waste in the ground. ROSATOM. The methodology developed in 2010 [3] The considered methodology for assessing NPP risk indicators is devoted to the first direction of propagation, and Copyright © 2019 for this paper by its authors. Use permitted under Creative Commons License Attribution 4.0 International (CC BY 4.0). specifically to the effects of air emissions on the population and external. The main ways of radioactive pollution of the personnel. environment are: - As initial data for the calculation of risk for personnel - release of radioactive substances into the atmosphere; and the population are used: Frequencies of - discharge of radioactive substances into surface waters consequences in design and beyond design basis (rivers, lakes, etc.). accidents (calculated using probabilistic safety analysis In this study, only the first pathway is considered. (PSA)); Estimation of population exposure doses is carried out for - Estimation of the number of radionuclides involved in three age groups: the design and beyond design basis accidents; - for adults (over 18); - Data on climatic conditions in the area of the NPP - for school-age children (from 7 to 12 years old); location: repetition of wind directions, average annual - for preschoolers (from 1 to 2 years). wind speed; Evaluation of external exposure doses of the population is - Data on the population in the 100-km NPP zone, carried out for two directions of external exposure: population distribution by points. - exposure from a radioactive cloud; Release of radionuclides into the environment is considered - irradiation from the underlying surface. short-lived. When estimating the population exposure doses, In general, the model of external exposure is based on the three methods of exposure are taken into account: presence of a dose coefficient relating the concentration of - direct inhalation; radionuclides to the dose characteristic of the external radiation - exposure from a radioactive cloud; field or directly to the effective dose. This approach involves the - exposure from a contaminated surface to the ground. use of measured data during radiation monitoring as source data: The assessment result of the accident radiation consequences - concentrations of individual radionuclides in the surface on the population are: layer of air; - absorbed dose of external irradiation of the whole body - surface contamination of the underlying surface by and internal irradiation of the thyroid gland during individual radionuclides. inhalation at the initial stage (first 10 days) of the The effective external dose for the i-th group of the accident; population when exposed to a radioactive cloud Eext i,a (mSv) is - annual effective radiation dose. defined as: Early deaths among the population are excluded, because Eext 𝑎 𝑎 i,a = Ki,a ∙ T ∙ ∑𝑘=1 e𝑘 ∙ 𝐶𝑘 , (1) maximum individual absorbed doses do not reach the level of 1 where: e𝑎𝑘 is the dose coefficient determining the absorbed Gray, and internal exposure of the thyroid gland during dose rate of gamma radiation from the k-th radionuclide at a inhalation does not reach the level of 5 Gray, at which height of 1 m above the underlying surface from the source in the deterministic effects are possible. form of a radioactive cloud, (mGy / h) / (kBq / m3); In [5, 6], the assessment is made for an average adult with an 𝐶𝑘𝑎 − the average concentration of the 𝑘-th radionuclide, kBq average radiosensitivity. This provides a basis for studying the / m3; influence of age composition on estimates of radiation risk T − the time of exposure from this source, hour; indicators of the population. Ki,a is the coefficient of transition from the dose in the air to According to the results of calculations, indicators of the effective dose for the 𝑖th group of the population, mSv / mGy. radiation and economic risks from accidents for nuclear power Ki,a is assumed to be: plants are compared with [8, 9]. - 0.7 mSv / mGy - for adults; 4. Calculating Method of the exposure level for - 0.75 mSv / mGy - for schoolchildren; different age population groups - 0.85 mSv / mGy - for preschoolers. Based on Formula 1, we can assume that the effective dose In [5, 6], the radiation risk assessment is made for an average of external exposure from a radioactive cloud linearly depends adult with an average radiosensitivity. According to [4], which on the coefficient Ki,a . regulates the process of rapid assessment of doses to the public Similarly, the effective external dose of the i-th group of the during radioactive contamination of the territory by air, there is population from a mixture of radionuclides dropped on the a significant difference in the transition factors from the absorbed underlying surface, Eext i,𝑠 , linearly depends on Ki,s : radiation dose to the effective dose, reflecting the risk of Eext 𝑠 𝑠 i,𝑠 = Ki,s ∙ T ∙ ∑𝑘=1 e𝑘 ∙ 𝜎𝑘 , (2) radiation effects for different age groups. 𝑠 where: e𝑘 is the dose coefficient determining the absorbed 5. Estimation of the exposure level for different age dose rate of gamma radiation from the k-th radionuclide at a population groups height of 1 m from a flat isotropic source located at the air-to- ground boundary, (mGy/hour) / (kBq/m2); The following concepts are used for evaluation: 𝜎𝑘𝑠 − surface activity of the k-th radionuclide on the soil, - Absorbed dose in a tissue or organ - the amount of kBq/m2; ionizing radiation energy transferred to the tissue or T − the time elapsed since the end of the radioactive fallout, organ; hour; - Equivalent dose - absorbed dose in an organ or tissue Ki,s is the transition coefficient from the dose in air at a height multiplied by the corresponding weighting factor of this of 1 m above the underlying surface to the effective dose for the type of radiation, reflecting the ability to damage body i-th group of the population, mSv / mGy. Ki,s is assumed to be: tissues (the weighting coefficient of gamma radiation - 0.75 mSv / mGy - for adults; for biological tissue is taken to be unity); - 0.80 mSv / mGy - for schoolchildren; - Effective dose - the value used as a measure of the risk - 0.90 mSv / mGy - for preschoolers. of the occurrence of the remote effects of exposure of When a population is exposed to a man-made environment, the entire human body and individual tissues and the characteristics of the radiation field change. It is possible to organs, taking into account their radiosensitivity. take into account this change in the calculations using the Radioactive pollution of the environment is the starting point location factors Lj , defined as the ratio of the dose rate in the air in the further chain of human exposure pathways: internal and at point j within the settlement or in its area due to man-made gamma radiation, to a similar value over the open virgin soil . 6. NPP Radiation Risk Assessments Human behavior in the radiation field is described using the In this section, a quantitative assessment of the physical and factors of behavior Fij , depending on the season and representing economic indicators of radiation risk for the Rostov and Kalinin a fraction of the time during which representatives of the i-th nuclear power plants taking into account the age composition of population group are located at the j-th point of the locality. the population. In the study we neglect these parameters due to the lack of anthropogenic characteristics of the territory around the NPP. Radiation Risk Assessments at Rostov NPP The study of the influence of place factors and factors of population behavior is also of scientific value and can be Rostov NPP is located in the Rostov region, 12 km from the considered as part of a separate work. city of Volgodonsk on the bank of the Tsimlyansk reservoir. The following initial data are used in assessing the internal Volgodonsk is located in the eastern part of the Rostov region, exposure doses of the population: between two million-plus cities - Rostov-on-Don and Volgograd. - concentration of radionuclides in the air; Rostov NPP is one of the largest energy companies in the - duration of inhalation. south of Russia, providing about 15% of the annual electricity The value of the effective dose from inhalation in the i-th generation in the region. group of the population can be calculated using the expression: The electrical capacity of the three existing power units is 3.1 GW. All reactors (four power units) are VVER-1000 water-to- 𝐸𝑖𝑖𝑛ℎ = 10−6 · 𝑉𝑖 · 𝑇 · ∑𝑘=1 𝐶𝑎𝑘 ∙ ℎ𝑖,𝑘 𝑖𝑛ℎ , (3) water power reactors. Power units of the Rostov NPP were where: ℎ𝑖,𝑘 𝑖𝑛ℎ is the dose coefficient for the 𝑖-th group of the commissioned in 2001, 2009, 2015 and 2018. population and the 𝑘-th radionuclide, Sv / Bq; Estimation of the potential radiative forcing of radionuclide 𝐶𝑎𝑘 is the average concentration of the 𝑘th radionuclide in the emissions (RS) is made on the basis of population data by points surface air layer during the passage of the radioactive cloud, kBq and distance from Rostov NPP from 3 km to 30 km, and the / m3; average population density outside the 30 km zone to 100 km is 𝑇 − time of exposure from the source, hour; also estimated (Table 1 and Fig. 1). 𝑉𝑖 − respiration intensity of representatives of the 𝑖-th group Table 1. Population distribution in the zone with a radius of of the population, m3 / hour. 100 km around the Rostov NPP Based on Formula 3, we can assume that the effective dose Rumba Distance from NPP, km Total people 3-10 10-15 15-20 20-30 30-40 40-50 50-100 from inhalation depends linearly on ℎ𝑖,𝑘 𝑖𝑛ℎ and 𝑉𝑖 . North - - 315 868 1 044 1 342 11 186 14 755 Data on ℎ𝑖,𝑘 𝑖𝑛ℎ are known only for the most irradiated critical Northeast East 860 860 - - 88 620 390 512 1 044 1 342 1 044 1 342 11 186 11 186 14 910 15 564 age groups of the population [8], therefore, it is impossible to Southeast 230 - 591 791 1 044 1 342 11 186 15 184 differentiate according to a given coefficient for different age South 230 345 193 1 076 1 044 1 342 11 186 15 416 Southwest - 595 74 952 15 432 1 044 1 342 11 186 104 553 groups. West - 250 75 574 26 780 1 044 1 342 11 186 116 176 The value of the equivalent dose to the thyroid gland in the Northwest - - 1 071 12 622 1 044 1 342 11 186 27 265 𝑖𝑛ℎ Total 2 180 1 190 153 404 58 571 8 352 10 736 89 488 323 823 i-th group of the population from inhalation 𝐻𝑖,𝑡ℎ𝑟 is calculated as: 𝑖𝑛ℎ 𝐻𝑖,𝑡ℎ𝑟 = 𝑉𝑖 · 𝑇 · ∑𝑘=1 𝐶𝑎𝑘 ∙ ℎ𝑖,𝑘 𝑡ℎ𝑟 (4) 𝑘 where: ℎ𝑖, 𝑡ℎ𝑟 − dose coefficient for the i-th population group and the k-th radionuclide (iodine or tellurium), mSv / kBq; 𝐶𝑎𝑘 is the average concentration of the 𝑘th radionuclide in the surface air layer during the passage of the radioactive cloud, kBq / m3; 𝑇 − time of irradiation from this source, hour; 𝑉𝑖 − respiration intensity of representatives of the 𝑖-th group of the population, m3 / hour. Fig. 1. Population distribution in the zone with a radius of 100 On the basis of Formula 4, we can assume that the equivalent km around the Rostov NPP dose of irradiation of the thyroid gland linearly depends on ℎ𝑖,𝑘 𝑡ℎ𝑟 On the basis of [5], the accident “Disruption of the steam line and 𝑉𝑖 . in the protective shell of the NPP with the design value of leakage The effective dose of internal exposure of the population due in the steam generator from the 1st circuit to the 2nd” was chosen to the oral intake of the k-th radionuclide in the body is calculated as the design basis accident (implementation frequency 5.6·10-5 by measuring its specific activity in the consumed food products. 1/reactor-year), as a beyond design basis accident - Sampling and measurements are carried out at times t1 and t2, “Deenergizing NPPs with a diesel generator failure and BRU-A” where t1 and t2 are the time elapsed since t0 the start of (frequency ϑ=3.8·10-8 1 / reactor-year). consumption of contaminated food (it is assumed that this The share of absorbed internal radiation in the total absorbed moment coincides with the end of radioactive fallout). In the radiation is approximately 98%. Based on this, and also taking study, we neglect this indicator, because We consider the into account the uncertainty of age coefficients when calculating indicators of the effective dose of radiation in the early phase of the effective dose of external exposure, it was proposed to adjust the accident (the first 10 days). the total effective dose by the coefficient for internal exposure The total effective dose for the i-th group of the population ℎ𝑖,𝑘 𝑡ℎ𝑟 ∙ 𝑉𝑖 (formula 4). living in the territory that has been contaminated with a mixture Based on the obtained coefficients, the average total effective of radionuclides is equal to the sum of doses of external exposure annual doses of external and internal exposure (formula 5) of from the radioactive cloud Eext i,a and deposition on the underlying three population groups in each of the ring segments of rumba surface Eexti,s , internal dose due to inhalation of radionuclides are calculated. The calculation results are shown in Table 2 and 𝐸𝑖𝑖𝑛ℎ : Fig. 2. 𝐸𝑖𝑠𝑢𝑚 = Eext ext 𝑖𝑛ℎ i,a + Ei,s + 𝐸𝑖 , мЗв (5) The equivalent dose of the thyroid gland for the i-th group of Table 2. Estimation of average total effective annual doses the population is equal to the sum of doses due to inhalation of of external and internal exposure of three population iodine radionuclides 𝐻𝑖,𝑡ℎ𝑟 𝑖𝑛ℎ , mSv. groups in each of the ring segments of rumba during the most dangerous accident at the Rostov NPP 100 km around Kalinin NPP Distance from NPP, km 𝑬𝟏𝒔𝒖𝒎 , mSv 𝑬𝟐𝒔𝒖𝒎 , mSv 𝑬𝟑𝒔𝒖𝒎 , mSv Distance from NPP, km Total Rumba 3-10 10,52 20,76 26,75 3-5 5-10 10-15 15-20 20-30 30-40 40-50 50-100 people 10-15 1,91 3,77 4,86 North 0 251 170 258 295 241 3 090 26 511 30 816 15-20 1,04 2,06 2,65 Northeast 0 157 88 266 203 189 3 090 26 511 30 504 20-30 0,60 1,18 1,52 East 0 254 177 464 301 287 9 499 52 549 63 531 30-40 0,32 0,63 0,82 Southeast 0 377 296 549 421 407 3 090 38 354 43 494 40-50 0,20 0,40 0,52 South 8 505 325 246 498 370 356 3 090 74 155 87 545 50-100 0,11 0,21 0,27 Southwest 16 158 318 230 598 370 356 52 342 26 511 96 883 West 7 339 336 227 562 370 356 3 090 50 964 63 244 Northwest 0 227 176 379 279 265 3 090 81 242 85 658 Total 32 002 2 245 1 610 3 574 2 609 2 447 80 381 376 797 501 665 Fig. 2. Estimation of average total effective annual doses of external and internal exposure of three population groups in each of the ring segments of rumba during the most dangerous accident at the Rostov NPP To estimate the number of the N_i population in each age Fig. 3. Population distribution in a zone with a radius of 100 km group, data from the 2010 All-Russian Population Census for the around Kalinin NPP Rostov Region were used, according to which the adult Based on [6], the “Medium primary circuit leak” accident population is 85%, schoolchildren (7-12 years old) - 8%, (with a sales frequency of 4.2·10-4 1 / reactor-year) was selected preschool children (1-2 years) - 7%. as the most likely accident at the Kalinin NPP, with the refusal To assess the radiation effects of the accident on the various of the ECCS high and low pressure" (with a frequency ϑ = groups of the population in 8 points in the 100 km zone around 1.47·10-6 1 / reactor-year). the Rostov NPP, the following calculations were made: The share of absorbed internal irradiation in the total - collective dose 𝐸𝑖𝑐𝑜𝑙 , man · Sv / year; absorbed irradiation is approximately 97%. Proceeding from this, - late deaths, 𝑁𝑖𝑑𝑡ℎ ; and also taking into account the uncertainty of age coefficients - collective risk of late death, 𝑅𝑖𝑑𝑡ℎ . when calculating the effective external dose, it was proposed to 𝐸𝑖𝑐𝑜𝑙 = 𝑁𝑖 ∙ 𝐸𝑖𝑠𝑢𝑚 (6) adjust the total effective dose by the coefficient for internal For the most complete assessment of the harm that can be exposure ℎ𝑖,𝑘 𝑡ℎ𝑟 ∙ 𝑉𝑖 (Formula 4). caused to health as a result of radiation in small doses, the Calculating the coefficient ℎ𝑖,𝑘 𝑡ℎ𝑟 ∙ 𝑉𝑖 we get (Fig. 4): damage is determined by quantifying both the effects of irradiation of individual organs and tissues of the body, differing in radiosensitivity to ionizing radiation, and of the organism as a whole. In accordance with the linear non-threshold theory of dose risk dependence of stochastic effects generally accepted in the world, the magnitude of the risk is proportional to the radiation dose and is related to the dose through the linear radiation risk coefficients. 𝑁𝑖𝑑𝑡ℎ = 𝑘 ∙ 𝐸𝑖𝑐𝑜𝑙 (7) 𝑅𝑖𝑑𝑡ℎ = 𝜗 ∙ 𝑁𝑖𝑑𝑡ℎ (8) where 𝜗 = 3.8 · 10-8 1/ reactor-year. The economic damage 𝐺𝑖 as a result of harm to the health of Fig. 4. Coefficient 𝒉𝒌𝒊, 𝒕𝒉𝒓 ∙ 𝑽𝒊 for Rostov and Kalinin NPP the population, which can manifest itself in the form of stochastic Or the ratio relative to the indicators for the adult population effects (radiogenic cancer and hereditary diseases), is estimated (Fig. 5): by the formula: 𝐺𝑖 = 𝑧 ∙ 𝐸𝑖𝑐𝑜𝑙 (9) where z is the monetary equivalent of the loss of one person- year of life of the population, is assumed to be equal to 0.3 million rubles / person-Sv. Radiation Risk Assessments at Kalinin NPP Kalinin NPP is located on the southern shore of Lake Udomlya and near the city of the same name. The town of Udomlya is located north of the Tver region, 120 km from the Fig. 5. The indicators for the adult population for Rostov and city of Tver. The Kalinin NPP has four power units with VVER- Kalinin NPP 1000 type reactors. The 1st and 2nd power units were launched Using these coefficients, we calculate the average total in 1984 and 1986, the 3rd and 4th power units in 2004 and 2012, effective annual doses of external and internal exposure respectively. The potential radiative forcing of radioactive (Formula 5) of three population groups in each of the ring substances is estimated on the basis of population data by points segments of rumba. and the distance from Kalinin NPP from 3 to 30 km, and the To estimate the number of the N_i population in each age average density of the population living at a distance of 30-100 group, data from the 2010 All-Russian Population Census for the km is estimated (Table 3 and Fig 3). Tver Region were used, according to which the adult population Table 3. Population distribution in a zone with a radius of is 85%, schoolchildren (7-12 years old) - 8%, preschoolers (1-2 power plants during beyond design basis accidents with the years) - 7%. release of sources of thermal neutrons with low flux density». To assess the radiation effects of the accident on various groups of the population, the following calculations were 10. References: performed at 8 points in the 100 km zone around the Kalinin 1. On approval of a typical safety data sheet of a hazardous NPP: collective dose 𝐸𝑖𝑐𝑜𝑙 , man · Sv / year; the number of late object: [Order of the Emergencies Ministry of Russia No. deaths, 𝑁𝑖𝑑𝑡ℎ ; collective risk of late death, 𝑅𝑖𝑑𝑡ℎ . 506 of November 4, 2004]. - M., 2004. - 1 p. The economic damage 𝐺𝑖 as a result of harm to the health of 2. Safety data sheet of the critical (dangerous) object of the population, which can manifest itself in the form of stochastic Rosatom: [order of the Ministry of Emergency Situations of effects (radiogenic cancer and hereditary diseases), is estimated Russia No. 506 of November 4, 2004]. - M., 2006. - 9 p. by the formula (9). 3. Methodology for assessing risk indicators for managing the Comparison of the obtained damage indicators with those safety of critical (hazardous) facilities of ROSATOM: calculated without taking into account the age composition of the [Methodology: Approved by the First Deputy Director population confirms that the adjustment for the age composition General of the State Atomic Energy Corporation gives an order of magnitude higher indicators of the risk of ROSATOM for the nuclear weapons complex on March 29, exposure of the population. The emergency exposure of the 2016]. - M., 2016. - 253 p. population, taking into account the adjustment, is below the 4. Rapid assessment of radiation doses to the public in case of levels that are subject to radiation safety requirements. radioactive contamination of the territory by air: Nevertheless, the results obtained make it possible to argue that [Guidelines MU 2.6.1.2153-06: approved by the Chief State the age composition of the population must be taken into account Sanitary Doctor of the Russian Federation on 04.12.2006]. when developing measures to reduce the risk and mitigate the - M., 2007. - 90 p. consequences for the population and, in particular, for the most 5. Kabanov, L.P., Berberova, M.A., and others. Risk sensitive age groups (1-12 years old). assessment of a reference nuclear power plant with a VVER (operating unit of a nuclear power plant with a VVER - 7. Results 1000): a report on research and development reg. № According to the results of the study, the author achieved the 1821OT10 // International Nuclear Safety Center - M., following results: 2010. - 132 p. 1. Review of existing approaches to assessment of 6. Zhukov, I.V., Berberova, M.A., and others. Developing a population radiation risk and risk indicators; list of safety management measures and assessing risk 2. Identification of the degree of influence of age indicators for Stage 2 of the Kalinin NPP with a WWER- composition on the calculation of radiation doses of the 1000 reactor (V-320): a research report on reg. No. population at different irradiation routes (external and 2339OT12 // International Nuclear Safety Center - M., internal); 2012. - 109 p. 3. Modification of the formula for calculating the annual 7. Procedural Guidelines for Risk Assessment of Hazardous effective dose of radiation of the population in the ring Industrial Facilities. Series 27. Issue 16. – M.: Closed Joint- segment of the Rumba taking into account the age Stock Company “Scientific and Technical Center for composition; Industrial Safety Research”, 2016. - 56 p. 4. Calculation of the annual effective dose of different age 8. SanPiN 2.6.1.2523-09. Radiation safety standards (NRB- groups for Rostov and Kalinin NPP with VVER-1000 99/2009). Approved by the Resolution of the Chief State Tapa reactors; Sanitary Doctor of the Russian Federation // No.47 of 5. Calculation of physical and economic indicators of 07.07.2009. - M., 2009. - 75 p. damage of different age groups of the population for 9. Recommendations of the International Commission on Rostov and Kalinin NPP. Radiation Protection from 2007: [ICRP Publication 103: approved March 2007]. - Moscow: Proceedings of the 8. Conclusions ICRP, 2009. 344 p. According to the results of calculations, indicators of radiation and economic risks from accidents for Rostov and Kalinin NPPs are within the limits allowed by the requirements [8] and [9]. Nevertheless, there is a significant deviation in the positive direction for all indicators in the calculation, taking into account the age composition. This determines the need to take into account the results obtained to assess the radiation risk. The study makes a significant contribution to the development of methods for assessing the radiation risk of nuclear power plants and can serve as an incentive to further study the influence of external factors such as population composition, geographical features, anthropogenic environmental change, etc. on risk assessment. Refined estimates of physical and economic indicators will significantly reduce planning errors in developing measures to reduce the risk and mitigate the consequences of accidents at nuclear power plants. 9. Thanks The study was carried out within the framework of grant 19- 07-00455 «Development of models, algorithms and software for solving the problems of safety and risk assessment at nuclear