The article estimates the time required to achieve radiation and radiological equivalence between radioactive waste and natural uranium raw materials, assuming that all thermal reactors will be fully replaced by fast reactors by the year 2130. Radiation equivalence will be reached when the carcinogenic risks of radioactive waste and natural raw uranium have the same value according to effective dose technologies. The estimated time required for this radiation equivalence is 250 years. Additionally, radiological equivalence can also be achieved if the carcinogenic risk associated with radioactive waste and raw natural uranium has the same values as those of lifetime attributable risk (LAR) technologies. The estimated potential time for this radiological equivalence is 78 years. Furthermore, the potential time for the burial of radioactive waste is also considered. It is estimated that this event will occur after the year 2208.

The forecast of lifetime radiation risks in exposed cohorts is currently carried out without considering the heterogeneity of cohort members in terms of their degree of polymorbidity. Polymorbidity is characterized by a reduction in the life expectancy of a person in the presence of several chronic diseases. Therefore, considering the polymorbidity factor can significantly affect the estimate of lifetime radiation risk. The purpose of this study is to investigate the effect of the polymorbidity factor of patients on the estimates of lifetime radiation risks of mortality from malignant neoplasms, as well as to compare the impact of polymorbidity factors and uncertainty of radiation doses on these estimates. To calculate the lifetime attributable radiation risk (LAR) per 1 mSv, the radiation risk models recommended by Publication 103 of the International Commission on Radiological Protection were used. The calculations are based on official medical and statistical data of 2021 for the Russian population. The effect of polymorbidity on human lifespan and on LAR estimates was considered using the classic Charlson Comorbidity Index (CCI). To assess the effect of the uncertainty of radiation doses on the LAR value, an example of a lognormal dose distribution with a standard geometric deviation of 2.2 (i.e., with a 90% uncertainty factor of 3.6) was chosen, which is typical for the population living in the areas of the Kaluga and Bryansk regions of Russia contaminated as a result of the Chernobyl accident. Simulation modeling was used to assess the effect of radiation dose uncertainty. It is shown that the variability of estimates of the lifetime radiation risk of mortality from malignant neoplasms due to the polymorbidity factor is comparable to the variability of this radiation risk due to the uncertainty of doses with an 90% uncertainty factor of 3.6. Thus, when calculating radiation risks in persons exposed to radiation, it is necessary to consider the presence or absence of chronic diseases, since this significantly affects the final assessments of radiation risks. Underestimation or overestimation of risk can be from 1.5 times or more.

The Fundamentals of State Policy in the Field of Nuclear and Radiation Safety of the Russian Federation, approved by the President of the Russian Federation, indicate that the goal of state policy in this area is to ensure the protection of the population, considering modern requirements. The IAEA Fundamental Safety Principles emphasize the need to protect both current and future generations from radiation risks. The achievement of these safety goals is ensured by the development in Russia of new nuclear energy system based on a closed nuclear fuel cycle (CNFC) and fast neutron reactors (FNR). One of the objects of the new nuclear energy system is the Experimental Demonstration Energy Complex (EDEC) consisting of the BREST-OD-300 FNR, a reprocessing module and a fuel fabrication/refabrication module, located on the territory of JSC «SHK» in the Tomsk region. This article provides assessments of radiation carcinogenic risks for the population living in the 30-km zone of JSC «SHK» under normal operating conditions and for workers after potential emergency situations at EDEC facilities. The conditions for ensuring the protection of future generations of people are also justified. Radiation risk assessments are obtained directly from the dynamics of equivalent doses in human organs and tissues and modern risk models recommended by ICRP Publication 103. The predicted values of the risks of radiation carcinogenesis for the population and personnel are significantly lower than the current limits of NRB-99/2009 for both normal operation and potential exposure during accidents. It has been shown that transmutation of minor actinides during the development of CNFC based on FNR ensures the safety of future generations of people: it reduces the carcinogenic risk of americium by 213 times, neptunium by 101 times, and curium by 47 times. The effect of radiological equivalence of radioactive waste and natural uranium raw materials is achieved after 99 years of radioactive waste storage. Thus, the priority direction for the development of new nuclear power is the energy sector of the CNFC based on the FNR.

Currently, the International Commission on Radiological Protection (ICRP) is discussing the practical application of a new radiation risk metric, called radiological detriment (RD). The concept of RD was first introduced by the ICRP in Publication 22 more than 30 years ago. At the same time, it was important to assess both the risk of radiation induced cancer development and the quality of the future life of patients. Of great interest is the comparison of RD and the lifetime attributable risk (LAR), which is currently widely used in assessing radiation safety. In this study, а comparison of RD and LAR estimates was made for the population living near the fabrication/refabrication module (FRM) of the Pilot Demonstration Energy Complex, that is currently under construction in the city of Seversk, Tomsk region. It is shown that during normal operation of the FRM and after a beyond design basis accident, the RD value is approximately 20% higher than the LAR value. Thus, the LAR value of mortality for residents of the city of Seversk during normal operation of the FRM is 40 times lower than the negligible risk level according to NRB-99/2009 (10Е-6 year-1), while the RD value remains 32 times lower than the negligible level. The simultaneous estimation of the RD and LAR values performed for the first time shows the possibility of their effective use for assessing the level of radiological protection of the population and workers.

The potential biological hazard (PBH) of radionuclides from the decay chains of Curium (Cm) isotopes in the pore water of sandy rocks has been investigated. The effect of the Pu isotopes from the Cm fraction after reprocessing spent nuclear fuel (SNF) and storage during 70 years on the PBH has been estimated. The effects of radionuclides toxicity and malignant neoplasms development in people were estimated as lifetime attributable radiation risk of cancer caused by oral consumption of radionuclides. It was found that, according to the fraction isolated from SNF with isotopes, Cm decreases by 10 times after the removal of Pu isotopes with a 0.1% residue in radioactive waste. It is shown that the processing of Cm with the release of Pu allows to reduce the time of occurrence of the radiation-migration balance with uranium raw materials for nuclear fuel, as well as to reduce the amount and danger of radioactive waste for deep burial.

The investigation is aimed at the analysis of the statistical dose-effect relationship between malignant neoplasms incidence rate in Russian clean-up workers (liquidators) participated in mitigation of the Chernobyl nuclear power plant accident (the Chernobyl NPP accident) consequences and radiation doses. The impact of radiation on the non-cancer diseases development in the Chernobyl liquidators was estimated as well. Radiation risks of different cancer cases were estimated considering the impact of the multimorbidity factor. The monitoring data accumulated in the National Radiation Epidemiological Register from 1986 over 2022 were used for analysis. During that period 9,755 cancer cases were detected among 69,520 male liquidators. The average personal external gamma radiation dose to liquidators, accumulated during the work period was 0.13 Gy, the maximum exposure dose was 1.4 Gy. The study used general data mining approaches that did not use hypotheses of the probabilistic laws of random variable distributions that determine the dependence of cancer diseases on radiation dose. A group of liquidators with personal doses of less than 0.15 Gy was selected as a control group. It was found that the non-cancer diseases in liquidators could both increase and decrease the radiation risk of malignant neoplasms morbidity, however, the relative changes in radiation risk do not exceed 2%. The results obtained demonstrate the stability of radiation risks estimates of cancer incidence obtained earlier in the Russian cohort of liquidators without taking into account the factor of multimorbidity.

One of the most important problems in the large-scale development of nuclear energy is the management and disposal of radioactive waste (RW). The potential biological hazard of RW for human health considerably exceeds the health hazard from uranium feedstock. Due to the natural processes of radioactive decay, the potential biological hazard of RW decreases over time. However, long-term storage and disposal of long-lived RW leads to an increase in the health and environmental hazard of nuclear energy. Recently, to reduce the hazard effects, the novel ap-proach based on the principle that hazard of RW should not exceed the hazard of natural urani-um raw materials has been used. This principle is called as "radiation equivalence" if the hazards levels are assessed by the radiation dose magnitude, and "radiological equivalence" is used if the hazards are assessed by the magnitudes of lifetime radiation risks of malignant neoplasms development. Earlier papers have already given point estimates of the time to reach “radiation” or “radiological” equivalence when analyzing a scenario based on a closed nuclear fuel cycle. This article proposes a method for estimating the uncertainties in the time to achieve radiation and ra-diological equivalence. The results of these estimates are presented for a model scenario for the development of nuclear power, in which thermal neutron reactors are gradually being replaced by fast neutron reactors by 2100. The numerical simulation method is used. Modern radiation risk models proposed by the International Commission on Radiological Protection (ICRP) and the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) are applied. The determination of equivalent radiation doses to organs and tissues was based on dose factors for radioactive substances provided for wide use by the US Environmental Protection Agency (EPA). If we assume that the maximum relative error of the initial values of the potential biologi-cal hazard of RW is about 246%, then the 95% confidence limit for achieving radiological equiva-lence was less than 340 years. The results of the study of the scenario for the development of nuclear energy in Russia, calculations show that since the integrity of containers with RW is main-tained for 1000 years, the safety of RW for future generations will be ensured.

The statistical relationship between radiation dose to the cohort of workers (liquidators), participated in mitigation of effects of the Chernobyl accident are considered in the paper. The follow-up data collected from 1992 to 2021 and accumulated in the National Radiation and Epidemiological Register (NRER) were used for analysis. The cohort of liquidators consisted of 67,304 males. The average radiation dose in the cohort was 0.13 Gy, and the average age at radiation exposure was 34 years. During the follow-up period 10,790 atherosclerosis cases (ICD-10, code 170) were detected for the first time. To identify statistical relationship between radiation dose and atherosclerosis incidence, general “data mining” approaches were used, that do not use hypotheses about the probabilistic laws of random variable distributions, that determine the relationship between radiation dose and atherosclerosis incidence. A group of liquidators with accumulated during the period of work individual radiation doses below 0.15 Gy was selected as the reference group. The maximum radiation dose in the studied cohort was 1.4 Gy. Statistically significant relationship between radiation doses and atherosclerosis incidence (ICD-10, code 170) were found: relative radiation risk RR=1.05 at 95% lower confidence bound 1.027. The relative risks (RR) for individual diagnoses are: RR=1.22 (95% CI lower bound – 1.20) for ICD-10 – I70.0 (aortic atherosclerosis); RR=1.03 (95% CI lower bound – 1.01); for ICD-10 – I70.2 (limb artery atherosclerosis); RR=1.06 (95% CI lower bound – 1.04) for ICD-10 – I70.9 (generalized and unspecified atherosclerosis). The RR increases with the age at diagnosis. The results obtained can be the basis for the design of radiation-epidemiological studies for the detailed quantitative study of the detected dose-effect relationships.

Objective To systematically review and perform a meta-analysis of radiation associated risks of cardiovascular disease in all groups exposed to radiation with individual radiation dose estimates. Design Systematic review and meta-analysis. Main outcome measures Excess relative risk per unit dose (Gy), estimated by restricted maximum likelihood methods. Data sources PubMed and Medline, Embase, Scopus, Web of Science Core collection databases. Eligibility criteria for selecting studies Databases were searched on 6 October 2022, with no limits on date of publication or language. Animal studies and studies without an abstract were excluded. Results The meta-analysis yielded 93 relevant studies. Relative risk per Gy increased for all cardiovascular disease (excess relative risk per Gy of 0.11 (95% confidence interval 0.08 to 0.14)) and for the four major subtypes of cardiovascular disease (ischaemic heart disease, other heart disease, cerebrovascular disease, all other cardiovascular disease). However, interstudy heterogeneity was noted (P<0.05 for all endpoints except for other heart disease), possibly resulting from interstudy variation in unmeasured confounders or effect modifiers, which is markedly reduced if attention is restricted to higher quality studies or those at moderate doses (<0.5 Gy) or low dose rates (<5 mGy/h). For ischaemic heart disease and all cardiovascular disease, risks were larger per unit dose for lower dose (inverse dose effect) and for fractionated exposures (inverse dose fractionation effect). Population based excess absolute risks are estimated for a number of national populations (Canada, England and Wales, France, Germany, Japan, USA) and range from 2.33% per Gy (95% confidence interval 1.69% to 2.98%) for England and Wales to 3.66% per Gy (2.65% to 4.68%) for Germany, largely reflecting the underlying rates of cardiovascular disease mortality in these populations. Estimated risk of mortality from cardiovascular disease are generally dominated by cerebrovascular disease (around 0.94-1.26% per Gy), with the next largest contribution from ischaemic heart disease (around 0.30-1.20% per Gy). Conclusions Results provide evidence supporting a causal association between radiation exposure and cardiovascular disease at high dose, and to a lesser extent at low dose, with some indications of differences in risk between acute and chronic exposures, which require further investigation. The observed heterogeneity complicates a causal interpretation of these findings, although this heterogeneity is much reduced if only higher quality studies or those at moderate doses or low dose rates are considered. Studies are needed to assess in more detail modifications of radiation effect by lifestyle and medical risk factors. Systematic review registration PROSPERO CRD42020202036

In the past decade the lawful use of radiation risks of non-cancer diseases estimates to solve ra-diation safety problems has become more significant. The highest statistical power of low dose (less than 0.2 Gy) radiation risks research is possible in the cohort of the Chernobyl clean-up workers (liquidators) registered and been under medical monitoring in the system of the National Radiation Epidemiological Register (NRER) since 1986. The liquidators total number exceeds 130 thousand people. Because of the large-scale annual collection of health data, carried out in the NRER system, verification of the diseases diagnoses and medically certified causes of death, a natural question of radiation risk estimates compatibility with consideration to probable errors in a disease diagnosis and cause-of-death reporting on death certificates arises. The work is aimed at estimating the radiation risk of mortality from diseases of the circulatory system and diseases of the digestive organs in the Russian cohort of liquidators, with account of possible errors in the disease diagnosis and certified causes of death. The size of the cohort considered for mortality analysis was 91,013 people, the average age at the Chernobyl zone entry was 33.6 years, average radiation dose was 0.133 Gy. In this study, the method of maximizing the partial likelihood function was used to assess radiation risks, with consideration of individual radiation doses to liquidators and the assessment of background mortality using the Breslow method. The specificity of the diagnosis of the primary causes of death in the NRER system significantly exceeds the level of 0.99. Considering the specificity index of 0.99, the estimates of radiation risk coefficients ERR/Gy for mortality from diseases of the circulatory system and diseases of the digestive system in the cohort of Russian liquidators do not differ from the estimates obtained in the assumption that there are no first kind errors (false positive diagnosis) in the diagnoses of the primary causes of death in the NRER database. The results obtained confirm the high stability and validity of the assessments of radiation risks of mortality from diseases of the circulatory system and diseases of the digestive system, obtained earlier from the data on liquidators registered in the NRER.

After receiving the notification of the license granting and its registration in the license register it has become topical the preparation of the final version of the project documentation to guarantee the safety of the public residing in the proximity of the operating Pilot-demonstration energy complex (PDEC), which includes a reactor unit BREST-OD-300, reprocessing module and a fuel fabrication/refabrication module. Currently International Commission on Radiological Protection (ICRP, Publication 103) recommends for estimating radiological protection of the public to use carcinogenic risks estimates for individual organs and tissues, with account of equivalent doses and modern models of «dose-effect» relationship instead of the use of committed effective doses. The article demonstrates the 5-7 times spread of lifetime carcinogenic radiation risk values from exposure to different radionuclides, while the committed effective dose from intakes of the same radionuclides do not differ. The distinguishing characteristic of updated ICRP recommendations is consideration of gender and age of the exposed population when assessing radiation-related carcinogenic risks. The article presents estimates of lifetime attributable risk for critical groups of the public residing in the proximity of the PDEC; the risk was calculated with the use of estimates of annual air emissions from normally operated PDEC. Tritium (H-3) and cesium (Cs-137) emissions limit values have been calculated, the radionuclides ensure the normal functioning of the complex in a negligible radiation risk range for the population (Radiation Safety Standards (RSS-99/2009)).

Economic and radiological advantages of the closed nuclear fuel cycle with fast neutron reactors in view of radiological equivalence, i.e. the equalization of carcinogenicity of radioactive waste and the natural uranium ore materials are considered in the paper. Potential cancer risks of the spent nuclear fuel (SNF) from the WWER-1000 reactor and radioactive waste from the BR-1200 reactor generating 1 GW of electric power per year have been estimated. It is assumed that the SNF from WWER-1000 reactor will be sent to 10 or 30-year storage. In the closed nuclear fuel cycle radioactive wastes, the products of SNF reprocessing, consisting of 0.1% of Sr, Cs, Tc, I, U, Np, Pu, Am, Cm of their content in SNF and all other radionuclides are disposed. Over a period of 10,000 years, the total radiation detriment from SNF from the WWER-1000 reactor is more than 132 times higher than the radiation detriment from radioactive waste from the BR-1200 reactor. The time of radiological equivalence achievement was evaluated. It is assumed that if WWER-1000 and BR-1000 generate 1 GW of electricity per year, radiological equivalence of carcinogenicity of radioactive waste (BR-1200 reactor) and natural uranium ore material will be achieved in 100 years of radioactive waste storage. The equivalence of carcinogenicity of SNF storage and natural uranium ore materials will be achieved after 15,600 years storage. When disposing of spent fuel from a WWER-1000 reactor without achieving radiological equivalence, socio-economic losses due to excess mortality from cancer are estimated at 129 billion rubles/GW year.

В журнале «Ядерная и радиационная безопасность» (№ 4 (106), 2022 г.) опубликована статья «К вопросу о достижимости радиационной (радиологической) эквивалентности радиоактивных отходов и природного урана». В работе рассмотрены теоретические и практические положения принципа радиологической эквивалентности. Отмечено, что статья публикуется в порядке дискуссии и редакция журнала будет признательна авторам с альтернативным мнением по данному вопросу. В настоящей статье указаны основные замечания по ранее опубликованной в журнале статьи (№ 4 (106), 2022 г.), в которой приводятся необоснованные ограничения по использованию принципа радиологической эквивалентности. The article “Achievability of radiation (radiological) equivalence of radioactive waste and natural uranium” was published in the Nuclear and Radiation Safety Journal (Nо. 4 (106), 2022). The paper considers the theoretical and practical provisions of the principle of radiological equivalence. It is noted that the article is published in the order of discussion and the editors of the journal will be grateful to the authors with an alternative opinion on this issue. This article contains the main comments on a previously published article in the journal (Nо. 4 (106), 2022), which provides unreasonable restrictions on the use of the principle of radiological equivalence.

According to GLOBOCAN 2020 Statistics based on estimates for 36 cancers incidence and mortality in 185 countries produced by the International Agency for Research on Cancer (IARC) in 2020, the total number of cancer cases increased by 19.3 million new cases and the number of cancer deaths increased by 10 million new cancer deaths. According to statistics, 1 of 5 people develops cancer during their life, and one of 8 men and one of 11 women die from the disease. The cancer burden to 2040 is expected to increase by 28.4 million cases. The dynamics of incidence and mortality from malignant neoplasms in the Russia is registered by the P. Hertsen Moscow Oncology Research Institute (MORI), branch of the National Medical Research Radiolog-ical Centre of the Ministry of Health of the Russian Federation. The data received in 2019 and 2010 were compared. The increase in cancer incidence over 10 years was 24%. However, thyroid cancer incidence surpasses other cancers incidence by 58%. The following main risk factors for potential regional induction of thyroid cancer are: the environmental situation in regions of Russia, the effects of the Chernobyl accident, and health effects of population exposed to radiation, approved with modern medical equipment. Based on epidemiological studies, it has been numerically proven that the above listed main risk factors are responsible for the significant increase in thyroid cancer incidence in Russia.

The paper presents for the first-time comparison of radiation safety for the population between spent nuclear fuel (SNF) irradiated in water-water power reactor with thermal neutrons (WWER-1000) and radioactive wastes (RW) from lead cooled fast neutrons reactor (BREST-1200). The re-actors generate equal amount of electric power 1 GW per year. Composition and radiation param-eters of long-lived radiation wastes sent to disposal is reviewed. Potential biological hazards from SNF and RW for about 10,000-years disposal were estimated as effective doses (Sv). To assess potential radiation-induced carcinogenic risk as estimates of lifetime attributable risk (LAR) new ICRP methodology was used. New ICRP methodology was used as the basis for the computer code for the program “Radiological protection of the population” (ROZA-N) developed by the Proryv Project of the Rosatom State Corporation. The project was registered at the Unified Register of Russian Software in 2021 (registration number 2442). It was found that potential radiation-induced carcinogenic risk for the population associated with WWER-1000 reactor SNF was 132 times high-er than the risk associated with BREST-1200 reactor RW. Radiological equivalence of carcinogenic risks associated with SNF WWER-1000 and natural uranium material was proven to be achieved in about 15,600 years (significantly more than 10,000 years), the radiological equivalence of risks associated with RW BREST-1200, on the other hand, to be achieved only in 120 years.

The current recommendations of the International Commission on Radiological Protection (ICRP) are based on the classification of exposure situations as: planned, emergency and existing exposure situations. In planned situations, annual risk limits are set to limit human exposure. However, in emergency exposure situations or in existing exposure situations, permanent (annual) source control is not always possible, so the radiation protection strategy by monitoring the individual annual risk limit cannot always be practically implemented either. The purpose of this work is to assess the radiation safety of the population currently residing (at the beginning of 2022) in six districts of the Bryansk region: contaminated with radionuclides as a result of the Chernobyl accident: in Gordeevsky, Zlynkovsky, Klimovsky, Klintsovsky, Krasnogorsky and Novozybkovsky districts. Assessment of the current state of radiation safety of the population is based on calculations of the radiation detriment from chronic exposure due to living in contaminated areas, considering uncertainties of the reconstructed exposure doses and the parameters of mathematical risk models for the population. Radiation damage is calculated according to the modern ICRP methodology. Based on the general principle of conservative assessment of safety, the calculated upper 95% confidence limits (95% CL) of radiation detriment are compared with the corresponding lifetime radiation detriment limit, 3.510-3, determined by the Russian radiation safety standards (NRB-99/2009) under normal exposure conditions for the nominal period 70 years of life for the public. The radiation safety of the population of the Klimovsky district corresponds to the normal conditions of exposure from technogenic sources of ionizing radiation. Among the population of the remaining five contaminated districts of the Bryansk region, critical groups have been identified, the radiation detriment for which exceeds the limit 3.510-3 for normal conditions of public exposure in planned situations. The results of this work can be used in the preparation of recommendations for health authorities to improve medical monitoring of exposed citizens living in territories contaminated with radionuclides, as well as in the development of regulatory documents for the provision of targeted medical care to people from high radiation risk groups with the use of personalized medicine methods.

Purpose: Investigation of the influence of the possible uncertainty of exposure doses of Russian participants in the liquidation of the consequences of the Chernobyl accident on the assessment of radiation risks of the incidence of solid cancer in this cohort. Material and methods: Epidemiological and dosimetric data on a cohort of Russian participants in the liquidation of the consequences of the accident at the Chernobyl NPP, registered in the National Radiation and Epidemiological Register (NRER), are used as initial data for assessing radiation risks. The assessment of radiation risks is carried out by the statistical method of maximum likelihood in the framework of a linear non-threshold model of excess relative risk. Uncertainties in the liquidator’s exposure dose in the adopted risk assessment method are considered in the form of two error models. Dose estimates based on data from individual dosimeters are characterized by a classical model of measurement errors. In the case of estimates of unknown individual doses from group dosimetry data or group route doses, the Berkson assignment error model is used. Results: A method for assessing radiation risks has been developed, accounting for the uncertainty in dose estimates, based on the observed likelihood function. When taking into account the uncertainty of estimates of individual doses in the cohort of Russian liquidators, the estimate of the coefficient of the excess relative rate per dose unit (ERR/Gy) for the incidence of solid malignancies decreases by 7%, compared with the estimate obtained directly from the doses registered in the NRER database. The ERR/Gy estimate derived from the doses recorded in the NRER database was 0.69 with a 95% confidence interval (CI) of 0.37–1.04. The estimate of ERR/Gy, obtained accounting for the uncertainty in estimates of individual doses of liquidators, was 0.64 at 95% CI (0.33–0.98). This estimate bias is not significant, since it is within 95% CI for both ERR/Gy estimates, the statistical range of which is of the order of magnitude of the estimates themselves. Conclusions: Considering the uncertainty of individual dose estimates in the cohort of Russian liquidators, the estimate of the excess relative rate per dose unit (ERR/Gy) for the incidence of solid cancer does not statistically significantly differ from the estimate obtained directly from the doses registered in the NRER database. The bias in the estimate of the radiation risk coefficient observed, due to the dose uncertainty introduced into the calculation, is due to the statistical properties of the traditional radiation risk models used for radiation epidemiology. The results obtained confirm the high stability and validity of the radiation risk assessments obtained earlier from the doses registered in the NRER for the Russian cohort of Chernobyl liquidators. Further research will allow generalization of the developed method for assessing radiation risks, accounting for the uncertainty of dose estimates, based on the observed likelihood function, to other types of radiation epidemiological risk studies, including case-control and case-cohort studies.

Purpose: The paper deals with the occurrence of prostate cancer and mean survival time following a diagnosis of the disease among Chernobyl clean-up workers. Material and methods: Clinical and dosimetry data accumulated at the National Radiation and Epidemiological Registry (NRER) during the period from 1996 over 2018 were used for the study. The study cohort consisted of 69,698 men. During the follow-up 742 prostate cancer cases were detected, all patients had radiation dose records, the disease stage was established in 628 patients. To assess radiation risk maximum likelihood approach was used. Mean survival time was evaluated with the use of the relationship between a disease prevalence and newly detected disease cases intensity in a stationary population (diseases intensity is equal to intensity of mortality from all causes). Results: Excess relative risk of prostate cancer induction per 1 Gy was 0.74 (95 % CI: ‒0.31; 2.15) and it was statistically insignificant. Standardized incidence ratios between clean-up workers and male population of Russia within 95 % confidence limits do not differ from 1.0. Mean survival time after the disease diagnosis within the period from 1996 over 2018 was 3.5±1.3 years. The relationship between a survival time and a disease stage was estimated. Survival time for cases with 1–3 stages 3.3±2.9, 3.6±2.3, 4.3±2.7 years respectively. The less survival time for cases with stage 4 was 1.5±0.8 years. Mean mortality rate, i.e. the ratio of the number of clean-up workers died from prostate cancer to the total number of clean-up workers with diagnosed prostate cancer was 36.8 %, for stages 1–4 it was 20, 16, 37, 74 % respectively. Mean survival time in the groups with doses less than and higher than 150 mGy was 3.4±1.4 and 3.7±1.7, respectively. Presented data confirm the null hypothesis that there is no difference in survival times (p=0.20). Conclusion: Increase in prostate cancer incidence becomes the social problem not only in Russia but in other countries as well. The paper presents results of comprehensive radiation epidemiological analysis of prostate cancer incidence in cleanup workers, who constitute the representative sample of the Russian male population. The dose ‒ prostate cancer incidence relationship for the follow-up period from 1996 over 2018 is not statistically significant, although the value of excess relative risk per dose unit is positive. It is not unthinkable that the absence of statistical significance is caused due to limited length of the follow-up period. But at the same time, the fact that observed the standardized incidence ratio is 1.0 and characteristics of two groups with doses ≥150 mGy are similar, speaks of the lack of a significant radiation effect. The obtained results of the analysis confirm our view of the necessity to continue the study.

Abstract The radiological hazard of spent nuclear fuel and radioactive waste slows down further development of nuclear energy systems. The authors evaluate timescales required to reduce the radiological hazard of accumulated waste to the reference level of natural uranium that had been consumed by the nuclear energy system. The estimate of this time scale depends on the radiological hazard metric used in the calculations. In this study, two metrics are compared: (1) the committed effective dose based on ICRP Publication 72 and (2) the lifetime radiation risk calculated with use of organ doses and recent radiation risk models recommended by ICRP. The effective dose of the waste reaches the reference level 300 y after the accumulation of waste, while lifetime attributable risk of waste converges to natural uranium in 100 y. Thus, the lifetime attributable risk (LAR) metric is more appropriate to estimate the time requirements for radioactive waste storage and disposal. The effective dose metric significantly overestimates this timescale as it is not intended for quantifying radiation-related risks.

The main problem of the large-scale development of nuclear energy in the world is the safe dis-posal of accumulated radioactive waste (RW). The hazard of RW at the time of their formation to human health far exceeds the hazard of the source natural uranium ore, after the use of which these wastes were formed. Due to the natural processes of radioactive decay, the hazard of radi-oactive waste decreases over time. The hazard of waste can also be reduced by artificial trans-mutation or incineration of the radionuclides that make up RW composition. For uranium nuclear fuel cycles, the natural reference level of RW hazard is the hazard level of the uranium ore, upon reaching which decisions can be made on the final disposal of RW. The article presents a meth-od for estimating the time of achieving radiological equivalence of the mass of accumulated RW of nuclear energy and the source mass of natural uranium raw materials used in this case. A de-scription of the software module "Radiological support of protection – radioactive waste" (PM ROZA-RAO), which implements this method, is also presented. Radiological equivalence herein refers to the equality of the corresponding radiation risks for the population. The methodology used is determined by the current recommendations of the International Commission on Radio-logical Protection (ICRP) and the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) on the calculation of human radiation risks from internal exposure based on equivalent doses in organs and tissues. The determination of equivalent doses to organs and tissues was based on dose coefficients of radioactive substances provided for widespread use by the United States Environmental Protection Agency (EPA). Calculations by means of the PM ROZA-RAO showed that within the framework of the most likely scenario for the development of two-component nuclear energy system in Russia, for radioactive waste accumulated by 2100, the time of onset of radiological equivalence is less than 100 years (98.8 years). With the help of the developed software module, for the first time in the nuclear industry, the parameters of the processing of exposed nuclear fuel (the composition and activity of radionuclides for controlled storage, combustion and transmutation) and the management of RW can be determined, minimizing the potential radiation risks of the population, which corresponds to the best practice of developed countries in the field of radiation protection.