This paper assesses the time to radiation (radiotoxicity) and radiological (radiation risk) equivalence between natural uranium and radioactive waste of thermal and fast reactors at an increasing content of Np, Am, and Cm in radioactive waste. We calculate radiation risk by adapting models of the ICRP and other international organizations for the Russian Federation, taking into account background epidemiological indicators including cancer incidence, cancer mortality, and overall mortality. The radiation risk of internal exposure considers both the time after radionuclide intake and equivalent dose dynamics in human organs and tissues. To determine the time to radiological equivalence, we estimate the lifetime attributable risk of a single intake of natural uranium radionuclides and radioactive waste. An increase in the Np, Am, and Cm content of radioactive waste within 0.1-0.4% causes no effect on the radiological equivalence time, equal to similar to 100 years. However, a further increase from 0.5-0.8% prolongs the time to 300 years. A problem for optimizing the time to radiological equivalence is posed providing for waste storage costs and content of Np, Am, and Cm in long-lived radioactive waste.

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.

An assessment of the potential biological hazard of radioactive waste in deep disposals after reprocessing of spent nuclear fuel of thermal and fast reactors in two-component nuclear power has been carried out. It is shown that when 0.1% of fissile materials, minor actinides and particular fractions of fission products are transferred to radioactive waste with the same contribution to the generated electricity of thermal and fast reactors the time of radiation-migration equivalence occurs after 140 years, and with a 75% contribution of fast reactors after 350 years, with a conservative assumption about the consumption of uranium raw materials only by thermal reactors. The estimation of the uncertainty of the calculation showed that for a sandy soil with a 50% contribution to the generation of electricity from thermal reactors, the time of radiation-migration equivalence varies between the lower and upper quartiles from 60 to 400 years. At the same time, 70% of the results are in the range of up to 200 years, and 90% – up to 400 years.

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.

Radiation doses to aquatic biota exposed to Siberian Chemical Plant (SCP, Tomsk) radioactive discharges, and Pilot-demonstration energy complex (PDEC) forecasting radiation doses from designed radioactive discharges were estimated. Doses to the biota in the habitat in the existing radiation situation were assessed with the use of measurements of water and bottom sediments samples collected during environmental monitoring of airborne radioactivity in 2017. Designed radioactivity discharges were assumed from normally operated PDEC modules for fabrication and refabrication and fuel reprocessing and reactor BREST-OD-300. It was found that the esti-mated highest radiation doses to biota were: for freshwater mammals – 24 μGy/day, it is 40 times below the reference levels; for fish – 7 μGy/day, it is 140 times below reference levels; for aquatic plants and mollusks – 1.2 μGy/day, it is about 10000 times below the reference levels. Anticipated radiation doses to the aquatic biota exposed to radiation discharged by PDEC were formed in the Lake Chernoe (Black Lake). The highest doses to fresh water mammals, fish and birds are 0.3 μGy/day, for aquatic plants and mollusks – 0.05 μGy/day. The main contributor to anticipated radiation doses to aquatic biota and birds is tritium, 3H.

Abstract The paper is concerned with the issue of achieving the radiological equivalence (the equivalence of radiation risks) of radioactive waste of nuclear reactors and corresponding mass of natural uranium, taking into account the different migration ability of radionuclides in geological formations and soil. This migration radiological equivalence is being investigated for the deep burial of radioactive waste in the case of the development of a two-component nuclear power system with the concurrent use of thermal neutron reactors and fast neutron reactors. Calculations were performed of radiation doses and radiation risks of cancer death arising from consumption of drinking water from a well above a disposal site. The radiation risk relating to a two-component nuclear power system is lower than that from natural uranium; i.e., after reaching the radiological equivalence (100 y of storage) over the timescale of 109 y, the principle of migration radiological equivalence is satisfied. It would take 106 y after radioactive waste disposal to reach the migration radiological equivalence if only thermal reactors were operated. As regards consumption of well drinking water, the radiation risk does not exceed 10−5 y−1 for a two-component nuclear power system, while being 10−3 y−1 (socially unacceptable level) for a power system using only thermal reactors. Radionuclides 241Am, 239Pu, and 240Pu in drinking water make the main contribution to the doses and radiation risks of people for 104 y after the disposal of radioactive waste.

The Russian Government approved the Energy Strategy of the Russian Federation (Government Decree No.1523-r of June 9, 2020). The Strategy envisages the use of both thermal (TR) and fast (FR) reactors. The Strategy points out that the problems of nuclear power are associated with po-tential high expenses for irradiated fuel and radioactive wastes management. The previously de-signed model of the Russian nuclear energy development suggested that fast reactors only would operate at NPPs after 2010. Radiological equivalence, expressed as the equivalence of lifetime radiation risks to the public from radioactive wastes and from primary uranium ore, was shown to be achieved after 100-year storage. The burnup of 241Am, 237Np и 242Сm in closed nu-clear fuel cycle with fast reactors is a key part in the achievability of radiation risks equivalence. Scenarios of the Russian nuclear energy development through to 2100 with account of uncertain-ty factors in the measurement of contribution of fast and thermal reactors to the electric energy production are considered in the paper. The following three scenarios were developed: uncer-tainty is replaced by FRs; uncertainty is replaced by TRs; 50 per cent of FRs and 50 per cent of TRs replace uncertainty. If the energy is produced by fast reactors only (scenario 1) radiological equivalence was found to be achieved in 412 years. In two other scenarios radiological equiva-lence will be achieved after more than 1000 years. Contribution of main dose-forming radionu-clides and relevant ratios of potential biological hazards is included in models regardless of whether uncertainty in nuclear energy development is taking or not taking into account. Results of the study of conditions for radiological equivalence achievement should be used for amending Strategic plan of Russian nuclear power development through to 2100 that meets requirements of radiation ecology and radiation protection of the public.

The paper presents results of research on radiological protection of the public during normal op-eration of Pilot-demonstration energy complex (PDEC) and in increased total power of reactor plants in the Industrial power complex (IPC) based on the current national radiation safety stand-ards (NRB-99/2009), UNSCEAR conclusions and ICRP recommendations. To evaluate radiologi-cal protection of the public the concepts of radiological detriment (RD) and the level of radiation protection (LRP) were used. The concepts were also used to examine the compliance of the BREST-OD-300, fabrication/refabrication module, processing module, BR-1200 and BN-1200 re-actors, collectively called nuclear objects, with safety standards. RD and LRP were estimated with the use of data of the Russian national cancer statistics and cancer statistics of the regions, wherein nuclear objects are planned to be placed – Tomsk, Sverdlovsk, Chelyabinsk. For the public residing nearby the nuclear objects the estimated LRP and RD meet NRB-99/2009 re-quirements concerning the restriction of radiation risk at the level of 10Е-5 from potential irradiation during a year. For the public of the critical group (girls younger than 5 years of age), residing nearby the PDEC and the nuclear objects the negligible risk of 10Е-6 can be achievable if annual radiation doses of 3H, for BREST-OD-300, reduce by 80%, and of annual doses of Cs-137, for the processing module reduce by 75%. The negligible risk for the public can be achieved if annual radiation doses of H-3 for BREST-OD-300 reduce by 10% and annual radiation doses of Cs-137 for processing module reduce by 5%. Projected radiation risk value for the public residing nearby BN-1200 and BR-1200 or nearby the IPC with two BR-1200 facilities will be much lower than the level of the negligible risk of 10Е-6. The RD calculated with ICRP methodology, serves as confirmation of the need to improve efficiency in cancer care in Tomsk region in order the regional RD to be at the national level. Because the high level of radiological protection of the public during the normal operation of the fabrication/refabrication module, its further operation when establishing IPC based on BR-1200 is feasible.

Проблема оптимального выделения америция из ОЯТ БРЕСТ-ОД-300 на трансмутацию для обеспечения радиационной эквивалентности РАО и природного урана Иванов В.К. 1,2,3, Адамов Е.О. 3 , Спирин Е.В. 3 , Соломатин В.М. 3 , Чекин С.Ю. 1,2, Меняйло А.Н.1,2 1 МРНЦ им.А.Ф.Цыба -филиал «НМИЦ радиологии» Минздрава России, Обнинск; 2 ООО «НПК «Мединфо», Обнинск; 3 АО «Прорыв», Москва Замкнутый топливный цикл с применением быстрых реакторов позволяет решать проблему сокращения радиоактивных отходов (РАО) более эффективно, чем традиционный открытый цикл с тепловыми реакторами.Количественные параметры выделения радионуклидов из облучённого ядерного топлива (ОЯТ) определяются принципом радиологической эквивалентности (РЭ) образующихся РАО и исходной массы природного урана, использовавшегося для изготовления ядерного топлива.Время достижения такой РЭ не должно превышать 300 лет, что может быть достигнуто выделением Am из ОЯТ и его сжиганием в быстром реакторе.С увеличением содержания Am в РАО расходы на переработку ОЯТ уменьшаются, но увеличивается время достижения РЭ и, соответственно, растут расходы на контролируемое хранение РАО.Поэтому суммарные расходы на переработку ОЯТ и дальнейшее контролируемое хранение РАО могут иметь минимум при определённом содержании Am в РАО.В данной работе показана принципиальная возможность определения оптимального содержания Am в РАО, при котором сумма расходов на очистку ОЯТ от Am и на дальнейшее контролируемое хранение РАО достигает минимума.Оптимальное содержание Am в РАО зависит от способа оценки времени достижения РЭ, соотношения расходов на очистку ОЯТ и хранение РАО, а также от процедуры дисконтирования расходов на хранение РАО.При определении времени достижения РЭ РАО и природного урана по равенству соответствующих пожизненных атрибутивных рисков (LAR) оптимальный остаток Am в РАО оказывается существенно больше, чем при использовании для этого ожидаемых эффективных доз (ОЭД), а суммарные расходы на очистку ОЯТ и хранение РАО -меньше.В рассмотренных примерах оптимальный остаток Am в РАО составил 1-2% при использовании величины LAR для определения РЭ, против 0,5% Am при использовании ОЭД.Минимальные суммарные расходы в первом случае были в 1,5 раза меньше.Для уточнения этих оценок требуются дальнейшие ис

The article presents analysis of safety of long-lived high level radioactive waste (RW) disposed for permanent storage in a deep geological repository. According to the study protocol it is necessary to estimate the human and environmental health safety of RW, generated in different nuclear fuel cy-cles, during their long-term stay in the repository. To estimate biological effects, RW composition from thermal reactors in open nuclear fuel cycle (“TR”) and from simultaneously operated thermal and fast reactors in closed nuclear cycle (“TR+FR”) in different time after their disposal have been evaluated. It is suggested that RW to be safe to humans and the environment if committed effective doses from RW components including minor actinides and fission products and from natural urani-um are equivalent (radiation equivalence) or lifetime attributable risks of cancer mortality from RW and natural uranium are equivalent (radiological equivalence). For this purpose it is important to evaluate the time of achievement of radiation or radiological equivalence. To evaluate health effect of RW containing radio-nuclides on the public and the environment their migration activity has been evaluated with the use of distribution coefficient and retardation factor. Probable annual effective doses to the public from exposure to the radionuclides released from the repository to the biosphere at different time after the RW disposal have been estimated. Radiation doses to the public following the consumption of water from the well installed on the repository, and lifetime attributable risk (LAR) of cancer mortality associated with the exposure to radionuclides contained in “TR” and ”TR+FR” generated waste have been evaluated. It turned out that LARs of cancer mortality from “TR+FR” radionuclides is lower than LAR from natural uranium, it means that radiological migration equivalence after its achievement will exists until the repository conditions allow, about 1 billion years. We have found that LARs from “TR+FR” waste is about 100 times lower than the negligible level, 10-6, established in the Russian National Radiation Safety Standards (NRB-99/2009). Estimat-ed LAR of cancer mortality from “TR”-generated waste is 360 times higher than LAR from “TR+FR”-generated waste. As evaluated for the waste from TR radiological equivalence will be achieved not earlier than 1 million years after permanent disposal. If RW is generated in the closed cycle estimat-ed LAR value from consumption of well water does not exceed 10-5 year-1, if RW is generated in open fuel cycle, the LAR value is 10-3 year-1, this is socially unacceptable risk. In the first 10 thousand years after the disposal the major dose- and risk-forming radionuclides in the well water will be 241Am, 239Pu и 240Pu. Estimates of radiation detriment from ”TR” generated waste put to the perma-nent deep geological disposal are given in the article.

Радиотоксичность долгоживущих высокоактивных отходов быстрых реакторов в сценариях обращения с облучённым ядерным топливом для достижения радиационной и радиологической эквивалентности с природным ураном