Long-lived Radionuclides Research Articles

Analysis of loss of cooling accident in VVER-1000/V446 spent fuel pool using RELAP5 and MELCOR codes

Following the Fukushima nuclear disaster, the simulation of accidents in the spent fuel pool has become more noticeable. Despite the low amount of decay heat power, the consequences of the accidents in a spent fuel pool (SFP) can be severe due to the high content of long-lived radionuclides and lack of protection by the pressure vessel.In this study, the loss-of-cooling accident (LOFA) for the VVER-1000/V446 spent fuel pool is simulated by employing RELAP5 and MELCOR 1.8.6 as the best estimate and severe accident analysis codes, respectively. For two cases with different total power levels, decay heat of spent fuels is calculated by ORIGEN-II code. For modeling SFP of a VVER-1000, a qualified nodalizations are considered in both codes. During LOFA in SFP, the key sequences such as heating up of the pool water, boiling and reducing the water level, uncovering the spent fuels, increasing the temperature of the spent fuels, starting oxidation process (generating Hydrogen and extra power), the onset of fuel melting, and finally releasing radionuclides are studied for both cases. The obtained results show a reasonable consistency between the RELAP5 and MELCOR codes, especially before starting the oxidation process.

Дозы облучения населения Беларуси вследствие аварии на Чернобыльской атомной электростанции на 2021-2025 гг.

In accordance with the Laws of the Republic of Belarus «On the social protection of citizens affected by the accident at the Chernobyl NPP» dated January 6, 2009 and «On the legal regime of territories exposed to radioactive contamination due to the accident at the Chernobyl NPP» dated May 26, 2012, the value of the average annual effective dose of exposure to residents is one of the indicators of the radiation situation in settlements contaminated with radionuclides as a result of the Chernobyl accident. The objective: to update the method for assessing the exposure doses to the population in the situation of existing exposure after the Chernobyl accident and, on its basis, to assess the average annual effective exposure dose to residents of settlements of the Republic of Belarus due to the Chernobyl accident for the period 2021-2025. The method for estimating the average annual effective doses due to external and internal irradiation to residents of radioactively contaminated settlements of the Republic of Belarus has been improved taking into account international recommendations in the field of radiation protection, changes in the radiation situation in the long-time period after the Chernobyl accident and the new data on individual dosimetry of internal exposure to the population based on the results of whole-body counter (WBC) measurements. An assessment of the average annual effective exposure doses to the population of the Republic of Belarus residing in the territory of radioactive contamination was carried out, and based on its results, the Catalog of average annual effective exposure doses to residents of 2193 settlements for the period 2021-2025 was compiled. According to the compiled Catalog of average annual effective exposure doses to residents of settlements located on the territory of radioactive contamination of the Republic of Belarus, in 29 settlements out of 2193, the total effective exposure dose can exceed 1 mSv/year, in addition, it is about 1 mSv/year in 5 settlements. In none of the settlements, the average annual effective radiation dose can exceed 5 mSv/year. Valid for the period 2021-2025 Catalog of average annual effective exposure doses to the residents of settlements located on the territory of radioactive contamination of the Republic of Belarus, along with data on the density of contamination of the territories of the Republic of Belarus with long-lived radionuclides, was used to compile the List of settlements and objects located in the zones of radioactive contamination, and to adopt a Resolution of the Council of Ministers of the Republic Belarus on designation of settlements to the corresponding zones of radioactive contamination.

Solar Activity over the Past Million Years according to Data on Long-Lived Radionuclides in Lunar Rocks

Solar Activity over the Past Million Years according to Data on Long-Lived Radionuclides in Lunar Rocks

Influence of tectonic perturbations on the migration of long-lived radionuclides from an underground repository of radioactive waste

We studied the influence of tectonic perturbations on the transport of potentially mobilized radionuclides in groundwater from a deep-mined repository of solid high-level radioactive waste. The study was carried out by the method of mathematical modeling. Key parameters of the model correspond to the site of a potential federal repository in Russia. The groundwater flow domain is delimited on one side by a water divide (i.e., boundary of the catchment basin) and on the other side by the river bank. 2D simulations of groundwater flow and radionuclide migration are carried out along a vertical cross-section normal to the water divide. The groundwater flows through the rock massif, which encloses the repository, and discharges into the adjacent river. It is supposed that tectonic activity may form a fault which is parallel to the river bank. We analyzed how repository safety depends on the time of the fault emergence and on the distance between the repository and the fault. The results of our simulations suggest that: (1) emergence of a fault due to tectonic perturbations is not inevitably associated with a substantial growth of radionuclides released from the repository to the environment; (2) influence of the fault on the repository safety depends on the distance between the fault and the repository as well as on the time interval between the repository development and the fault emergence; (3) the influence of the fault on the repository safety can depend substantially on local elevations of the relief at the repository site.

ASSESSMENT OF THE EXPECTED INDUCED RADIOACTIVITY IN THE BUNKER WALLS AT THE INRNE-BAS CYCLOTRON FACILITY

The Institute for Nuclear Research and Nuclear Energy at the Bulgarian Academy of Sciences is working on the construction of a cyclotron centre. Оne of the challenges in designing the radiation protection of a cyclotron centre is the preliminary assessment of the expected amounts of radioactive waste that will be generated during the lifetime of the facility. Our aim in this paper is to make an estimation of the expected induced radioactivity in the cyclotron bunker walls after the 20 year operational period of the facility. For this purpose, Monte Carlo simulations with the code FLUKA were performed. The distributions of the specific activity of the generated radionuclides in the concrete walls and of the residual dose rates inside the bunker are obtained. The specific activity of the most important long-lived radionuclides in the concrete walls of the bunker, namely 154Eu, 152Eu, 134Cs, 60Co, 54Mn is estimated. On the basis of these results an optimization of the shielding design is proposed in order to decrease the amount of radioactive waste which will be generated during the facility lifetime.

RADIOLOGICAL ASPECTS OF CYCLOTRON DECOMMISSIONING

In this paper, the radiological and economic issues of dismantling cyclotrons of various types, the accumulation
 of radionuclides in the details of the cyclotron itself, and the activation of the walls of the cyclotron bunker
 due to the capture of secondary neutrons are considered. As a result of (n,γ)-reactions on thermal neutrons, radionuclides
 152Eu, 60Co, 46Sc are formed in the concrete of the cyclotron bunker with a half-life of 2,6 to 14 years
 and an activity of 0,1–11 kBq/kg. The maximum of their distribution usually lies at a depth of 10–15 cm. In the
 details of the cyclotron and the metal infrastructure of the bunker, the main radionuclides are 54Mn, 57Co, 65Zn.
 The analysis of the accumulation of long-lived radionuclides is of great importance for the design of new cyclotron
 facilities in order to ensure radiation safety and storage of radioactive waste and, as a result, to minimize the
 radiation exposure of personnel during the dismantling of the cyclotron.

Dynamics of 137Cs and 90Sr content in the soil cover of agricultural lands in Zhytomyr region

The article examines the results of monitoring radionuclide contamination the soils of Zhytomyr region with 137Cs and 90Sr. We summarized the results of agrochemical certification of agricultural land for the period of research in 2006–2020 years (IX–XI rounds). For field and laboratory research, methods of agrochemical certification of agricultural lands and gamma-surveying of the territory and determination of the specific activity of 137Cs and 90Sr in soil samples were used. It was established that during the 36 years that have passed since the accident, the radiation state of the territory of Zhytomyr region has currently stabilized and is formed mainly under the influence of long-lived radionuclides cesium-137 and strontium-90. During the time that passed after the accident, only due to natural radioactive decay, the activity of the isotopes 137Cs and 90Sr decreased approximately by half. This was facilitated by natural processes and the implementation of measures to prevent the removal of radionuclides beyond the exclusion zone. Turf-podzolic soils, which are most common in the Polissia zone, are characterized by high sorption capacity and weak migration along the 137Cs profile. It was established that the number of agricultural lands contaminated with 137Cs and 90Sr with a density <5.0 Ki/km2 and <0.15 Ki/km2 is 99.9% and 99.5%, respectively, the density of land soil contamination in the section of the surveyed areas with 137Cs pollution varied from 0.07 to 3.41 Ki/km2, and 90Sr from 0.013 to 0.164 Ki/km2, therefore, according to current legislation, the soils are considered conditionally clean. A direct correlation between the indicators of the reaction of the soil solution with 137Cs contamination (r=0.94) and a significant correlation with 90Sr contamination (r=0.69) was revealed. A moderate correlation (r=0.40) was found between the indicators of the density of contamination of agricultural land with radionuclides 137Cs and 90Sr. It is emphasized that the use of the land fund of Zhytomyr region requires constant monitoring of soil fertility and contamination with radionuclides. The implementation of the task is possible under the condition of permanent soil and agrochemical monitoring, which is conducted by carrying out agrochemical certification of agricultural lands.

VERTICAL DISTRIBUTION OF RADIONUCLIDES IN SOILS OF SEMIPALATINSK TEST SITE

The article addresses the pattern of vertical distribution of the major long-lived man-made radionuclides 137Cs, 241Am, 90Sr and 239+240Pu in soils of the Semipalatinsk Test Site. Areas of different contamination with radionuclides are discussed – places of aboveground nuclear and fusion tests conducted at the ‘Experimental Field’ site, the fallout in the form of plumes within the Semipalatinsk Test Site, areas of radiological warfare agent tests at the ‘4А’ site, areas of meadow ecosystems associated with radioactively contaminated water streams from test adits of the ‘Degelen’ testing site, conventionally ‘background’ areas of the test site, in which no nuclear or fusion tests were conducted. In the course of research, differences were revealed in the vertical distribution of radionuclides of interest in soils of the above areas. Differences are attributed to the pattern of how contamination with radionuclides is formed and to abiotic and biotic factors such as physical and chemical soil properties, moistening conditions, human activity and others. Based upon findings, recommendations were developed, aimed at the optimization of research into the vertical distribution of radionuclides in the soil cover of the former Semipalatinsk test Site. In particular, it was found that when undertaking such research, it was sufficient to confine oneself to dividing a territory by the soil type and restrict the research depth to 30 cm.

The Alzheimer's disease 5xFAD mouse model is best suited to investigate pretargeted imaging approaches beyond the blood-brain barrier.

Alzheimer's disease (AD) is the most common neurodegenerative disease, with an increasing prevalence. Currently, there is no ideal diagnostic molecular imaging agent for diagnosing AD. Antibodies (Abs) have been proposed to close this gap as they can bind selectively and with high affinity to amyloid β (Aβ)-one of the molecular hallmarks of AD. Abs can even be designed to selectively bind Aβ oligomers or isoforms, which are difficult to target with small imaging agents. Conventionally, Abs must be labeled with long-lived radionuclides which typically results in in high radiation burden to healthy tissue. Pretargeted imaging could solve this challenge as it allows for the use of short-lived radionuclides. To develop pretargeted imaging tools that can enter the brain, AD mouse models are useful as they allow testing of the imaging approach in a relevant animal model that could predict its clinical applicability. Several mouse models for AD have been developed with different characteristics. Commonly used models are: 5xFAD, APP/PS1 and tg-ArcSwe transgenic mice. In this study, we aimed to identify which of these models were best suited to investigate pretargeted imaging approaches beyond the blood brain barrier. We evaluated this by pretargeted autoradiography using the Aβ-targeting antibody 3D6 and an 111In-labeled Tz. Evaluation criteria were target-to-background ratios and accessibility. APP/PS1 mice showed Aβ accumulation in high and low binding brain regions and is as such less suitable for pretargeted purposes. 5xFAD and tg-ArcSwe mice showed similar uptake in high binding regions whereas low uptake in low binding regions and are better suited to evaluate pretargeted imaging approaches. 5xFAD mice are advantaged over tg-ArcSwe mice as pathology can be traced early (6 months compared to 18 months of age) and as 5xFAD mice are commercially available.

Pipeline Impact of Radiolabeled Compounds in Drug Discovery and Development.

The long-lived radionuclides tritium and carbon-14 have been used for many years in pharmaceutical research and development for making key efficacy and toxicological decisions. Early discovery utilizes radiolabels for compound selection through radioligand binding assays and autoradiography. In preclinical safety evaluation, the use of labeled compounds for adsorption, distribution, metabolism, and excretion studies is often preferred for the added detection sensitivity. As the drug substance proceeds to the clinic, human metabolism studies are reliant on the use of labeled materials to fulfill required regulatory applications.

ACTIVITY CONCENTRATIONS OF RADIOCAESIUM, 90SR AND 129I IN AGRICULTURAL CROPS COLLECTED FROM FUKUSHIMA AND REFERENCE AREAS IN JAPAN, AND INTERNAL RADIATION DOSES

Abstract Significant quantities of radionuclides were released into the environment due to the 2011 TEPCO’s FDNPS accident. Radiocaesium is the most important radionuclide for assessment of radiation dose, and small amounts of 90Sr and very long-lived radionuclide of 129I were also released into the environment. Spinach, potato and brown rice were collected from Fukushima, neighboring prefectures and reference areas of negligible deposition in 2018 and 2019. The activity concentration of 137Cs in crops in Hamadori (coastal side) was relatively higher than other areas. The activity concentration of 90Sr in the crops showed a similar range among four areas in Fukushima, and they were similar level of those collected throughout Japan. The activity concentration of 129I in the crops collected from Hamadori was higher than other Fukushima areas. However, the activity ratio of 129I/137Cs was lower by five to seven orders of magnitude. Internal radiation doses of radiocaesium for adult males from ingestion of local crops collected from Hamadori were 0.0046 mSv, and that of 129I were 0.00000045 mSv in 2019.

Water mass composition in Fram Strait determined from the combination of 129I and 236U: Changes between 2016, 2018, and 2019

Changes in the provenance and composition of waters exported from the Arctic Ocean have the potential to impact large-scale ocean circulation processes in the sub-polar North Atlantic. The main conveyor of waters from the Arctic Ocean to lower latitudes is the East Greenland Current (EGC), flowing southward through Fram Strait. It is therefore crucial to determine and monitor the composition of the EGC, a mixture of polar waters of different origins. Here we present a pilot study on the potential of the long-lived anthropogenic radionuclides 129I and 236U as tracers of the EGC water mass composition, based on a time series of 236U and 129I concentrations measured across Fram Strait in the years 2016, 2018, and 2019. The overall spatial distribution of 236U and 129I was similar among the three sampling years, but a decrease in concentration was observed in the upper water column of the EGC. The observed changes could only partly be attributed to the transient nature of the radionuclide signals, but instead pointed to changes in the EGC water mass composition. To investigate these changes, 236U and 129I were first combined in a mixing model featuring the endmembers expected in the upper EGC. We distinguished between Pacific Water (PAC), Atlantic Water advected from the Arctic Ocean (ATL), and Atlantic Water recirculating in Fram Strait (RAC). In 236U-129I tracer space, PAC and RAC showed similar tracer signatures, but were well distinguished from ATL. From 2016 to 2018/19, a decrease in the ATL fraction was evident for the upper EGC. Secondly, the respective combination of 236U and 129I with salinity showed differences in absolute water mass fractions, but similar temporal trends. Both suggested an increase in PAC of about 20% for the uppermost layer of the EGC (samples with potential densities below 26.5) and an increase in RAC of about 10−20 % for denser samples. 129I and 236U, in combination with salinity, were shown to be suitable tracers to investigate water mass composition in Fram Strait, with the advantage that they can distinguish Atlantic Water advected from the Arctic Ocean from that recirculating in Fram Strait.

Immuno-PET Imaging of TNF-α in Colitis Using 89Zr-DFO-infliximab.

Tumor necrosis factor-alpha (TNF-α) neutralization has become increasingly important in the treatment of inflammatory bowel diseases (IBD). A series of monoclonal antibodies were approved in the clinic for anti-TNF-α therapy. However, a comprehensive assessment of TNF-α levels throughout the colon, which facilitates the diagnosis of IBD and predicts anti-TNF-α efficacy, remains challenging. Here, we radiolabeled infliximab with long-lived radionuclides 89Zr for immuno-positron emission tomography (PET) imaging of TNF-α in vivo. The increased TNF-α level was detected in the inflammatory colon of the dextran sodium sulfate-induced colitis mice. The immuno-PET imaging of 89Zr-desferrioxamine-infliximab reveals a high uptake (7.1 ± 0.3%ID/g) in the inflammatory colon, which is significantly higher than in the healthy control and blocked groups. The colon-to-muscle ratio reached more than 10 and was maintained at a high level for 10 h after injection. The ex vivo biodistribution study also verified the superior uptake in the inflammatory colon. This study provides an in vivo immune-PET approach to molecular imaging of the pro-inflammatory cytokine TNF-α. It is promising in diagnosing and predicting efficacy in both IBD and other autoimmune diseases.

Rapid determination of thorium in urine by quadrupole inductively coupled plasma mass spectrometry (Q-ICP-MS).

Inductively coupled plasma mass spectrometry (ICP-MS) has proven to be an excellent analytical technique with high sensitivity for detecting low levels of long-lived radionuclides, such as thorium. However, the high-sensitivity technique increases the memory effect of thorium. This study developed a rapid, high-throughput, simple method for measuring thorium in urine using quadrupole inductively coupled plasma mass spectrometry (Q-ICP-MS). Replacing the commonly used hazardous hydrofluoric acid with a rinse solution of 0.025 mol/L oxalic acid and 5% (v/v) nitric acid eliminated the memory effect of thorium. 233U was used as internal standard in this study. The limit of detection (LOD) for thorium in this study is 0.77 ng/L, which is comparable to those of reported methods using more sophisticated and expensive sector field inductively coupled plasma mass spectrometry (SF-ICP-MS). This proposed method can determine thorium concentrations in urine in both occupationally exposed workers and populations that live in areas with high background levels of thorium.

The Sedimentation Rate in the Crimean Hypersaline Lake Aktashskoye Estimated Using the Post-Chernobyl Artificial Radionuclide 90Sr as a Radiotracer

Artificial 90Sr is one of the most important long-lived radionuclides of global radioactive fallout from the atmosphere after the testing of nuclear weapons and the accident at the Chernobyl Nuclear Power Plant in 1986. In addition to fallout from the atmosphere, secondary radioactive contamination of Crimea was mainly from the Dnieper River and the North Crimean Canal, which occurred until 2014. 90Sr was used as the optimal radiotracer for estimating the rate of sedimentation in the Crimean hypersaline lake. Its vertical distribution in the bottom sediments was assessed. In the core of the bottom sediments, the detectable activity of 90Sr in layers 0–1.5 cm and 16.7–21.9 cm was absent, and it was determined again in the layer of 15.5 cm, which was associated with atmospheric fallout of the radionuclide after the Chernobyl NPP accident. There were well-isolated peaks of specific activity in layers at a depth of 4.6 and 13.3–14.3 cm. The calculated rate of sedimentation varied within 0.5–1.5 cm year−1: the minimum rate corresponded to the period 1971–2017, and the highest rate corresponded to the period 1954–1971.

Development of a new flowsheet for partitioning of long-lived radionuclides from high-level wastes: the “CRAMEX” process

Development of a new flowsheet for partitioning of long-lived radionuclides from high-level wastes: the “CRAMEX” process

Structural stability of REE-PO4 (REE = Sm,Tb) under swift heavy ion irradiation

Rare earth element (REE) phosphates are an attractive host matrix for long-lived radionuclides from nuclear waste because of the radiation tolerance exhibited by naturally occurring REE phosphate specimens. Here we show that SmPO4 (monazite structure) and TbPO4 (xenotime structure) exhibit a similar amorphization response to swift heavy ion irradiation despite different starting structures. SmPO4 and TbPO4 were irradiated with 1.1 GeV Au ions and analyzed using synchrotron-based X-ray diffraction (XRD), Raman spectroscopy, and transmission electron microscopy (TEM). The radiation response of the phosphates was evaluated by extracting the amorphous fraction at each irradiation fluence, and a single-impact model was used to determine the amorphous cross section and track diameter. Amorphization within individual ion tracks was confirmed using head-on TEM imaging, and the amorphous track size agreed with the value deduced by XRD analysis. Raman measurements were performed to qualitatively confirm the ion-induced crystalline-to-amorphous transformation which proceeds similarly for both phosphates.

89Zr]Zr-PSMA-617 PET/CT in biochemical recurrence of prostate cancer: first clinical experience from a pilot study including biodistribution and dose estimates

PurposeProstate-specific membrane antigen (PSMA)-targeted PET/CT has become increasingly important in the management of prostate cancer, especially in localization of biochemical recurrence (BCR). PSMA-targeted PET/CT imaging with long-lived radionuclides as 89Zr (T1/2 = 78.4 h) may improve diagnostics by allowing data acquisition on later time points. In this study, we present our first clinical experience including preliminary biodistribution and dosimetry data of [89Zr]Zr-PSMA-617 PET/CT in patients with BCR of prostate cancer.MethodsSeven patients with BCR of prostate cancer who revealed no (n = 4) or undetermined (n = 3) findings on [68Ga]Ga-PSMA-11 PET/CT imaging were referred to [89Zr]Zr-PSMA-617 PET/CT. PET/CT imaging was performed 1 h, 24 h, 48 h, and 72 h post injection (p.i.) of 111 ± 11 MBq [89Zr]Zr-PSMA-617 (mean ± standard deviation). Normal organ distribution and dosimetry were determined. Lesions visually considered as suggestive of prostate cancer were quantitatively analyzed.ResultsIntense physiological uptake was observed in the salivary and lacrimal glands, liver, spleen, kidneys, intestine and urinary tract. The parotid gland received the highest absorbed dose (0.601 ± 0.185 mGy/MBq), followed by the kidneys (0.517 ± 0.125 mGy/MBq). The estimated overall effective dose for the administration of 111 MBq was 10.1 mSv (0.0913 ± 0.0118 mSv/MBq). In 6 patients, and in particular in 3 of 4 patients with negative [68Ga]Ga-PSMA-11 PET/CT, at least one prostate cancer lesion was detected in [89Zr]Zr-PSMA-617 PET/CT imaging at later time points. The majority of tumor lesions were first visible at 24 h p.i. with continuously increasing tumor-to-background ratio over time. All tumor lesions were detectable at 48 h and 72 h p.i.Conclusion[89Zr]Zr-PSMA-617 PET/CT imaging is a promising new diagnostic tool with acceptable radiation exposure for patients with prostate cancer especially when [68Ga]Ga-PSMA-11 PET/CT imaging fails detecting recurrent disease. The long half-life of 89Zr enables late time point imaging (up to 72 h in our study) with increased tracer uptake in tumor lesions and higher tumor-to-background ratios allowing identification of lesions non-visible on [68Ga]Ga-PSMA-11 PET/CT imaging.

Europium radionuclides in samarium-153-Ethylene Diamine Tetramethylene phosphonic acid (153Sm-EDTMP) radiopharmaceutical waste

153Sm-EDTMP is widely used as a palliative radiopharmaceutical for treatment of metastatic bone pain. It is produced by neutron activation of enriched 152Sm targets in a nuclear reactor. The long-lived europium radionuclides are co-produced along with production of 153Sm and it give rise to radioactive waste in 153Sm-EDTMP production. The gamma radiation dose rate was found significant on the radioactive waste generated during the production of 153Sm-EDTMP. Residual activity in six waste samples generated in different batches of 153Sm-EDTMP production were analysed for percentage contributions of 152,154,155Eu using gamma-ray spectrometry. 154Eu was a major contributor with around 62%, and the other radioisotopes, viz. 152Eu &155Eu contribution were ∼29% & ∼9% respectively. The activity concentration of these long-lived europium radionuclides in samarium radiopharmaceutical production waste may be utilised for the dose rate estimation, and vice versa.

Review of Instant Release Fractions of Long-lived Radionuclides in CANDU and PWR Spent Nuclear Fuels Under the Geological Disposal Conditions

Review of Instant Release Fractions of Long-lived Radionuclides in CANDU and PWR Spent Nuclear Fuels Under the Geological Disposal Conditions