Tritium distribution in the 'water-soil-air' system in the Semipalatinsk Test Site

This article presents research findings on 3H in abiotic environmental compartments, specifically, the 'water-soil-air' system. All of the research areas are located within the Semipalatinsk Test Site (STS): the perimeter of the 'Degelen' site, the riverside zone of the Shagan river and the 'background' area-the southeastern part of the STS (SEP). As research progressed, numerical values of 3H and its species were revealed in various environmental compartments. The presence of 3H was registered not only in underground nuclear test locations but also in the 'background' area-SEP. Maximum 3H tritium concentrations in the water were detected at the 'Degelen' site (up to 57000±5000 Bq/kg) and the Shagan riv (up to 61500±6000 Bq/kg), in the air of the 'Degelen' site (up to 56±11 Bq/m3), in the soil of the 'Degelen' site (up to 5170±500 Bq/kg) and the Shagan riv (4100±400 Bq/kg) in the free water, at SEP (up to 1710±170 Bq/kg) in the organic constituent. Based upon all of the findings, 3H was found to be readily distributed in abiotic environmental compartments depending on certain conditions. Research suggests that water plays a key role in 3H migration processes in the natural system of interest. The second most but equally important constituent is soil and microorganisms of plant and animal origin living there. These assumptions are indirectly proven by research findings that show the HTO and HT air concentration dynamics depending on the sampling location.

Tritium and deuterium labelling of a kainate receptor antagonist and evaluation as a radioligand

Kainate receptors play a crucial role in mediating synaptic transmission within the central nervous system. However, the lack of selective pharmacological tool compounds for the GluK3 subunit represents a significant challenge in studying these receptors. Recently presented compound 1 stands out as a potent antagonist of GluK3 receptors, exhibiting nanomolar affinity at GluK3 receptors and strongly inhibiting glutamate-induced currents at homomeric GluK1 and GluK3 receptors in HEK293 cells with Kb values of 65 and 39 nM, respectively. This study presents the synthesis of two potent GluK3-preferring iodine derivatives of compound 1, serving as precursors for radiolabelling. Furthermore, we demonstrate the optimisation of dehalogenation conditions using hydrogen and deuterium, resulting in [2H]-1, and demonstrate the efficient synthesis of the radioligand [3H]-1 with a specific activity of 1.48 TBq/mmol (40.1 Ci/mmol). Radioligand binding studies conducted with [3H]-1 as a radiotracer at GluK1, GluK2, and GluK3 receptors expressed in Sf9 and rat P2 membranes demonstrated its potential applicability for selectively studying native GluK3 receptors in the presence of GluK1 and 2-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor-blocking ligands.

Hydrochemical systematics and isotope (δ18O, δD and 3H) variations of aquifer system of southern Bengal Basin: implications for groundwater pollution

Hydrogeological, hydrochemical and isotopic traits of the groundwater in the Quaternary aquifer system in an urban-periurban locality within and encircling the Kolkata-Howrah twin city in the south Bengal Basin have been synthesised to explain the present- and paleo-hydrological processes, surface and groundwater interaction and mixing dynamics of contamination of groundwater. Rock-weathering, evaporation, ion-exchange and active mineral dissolution are the key processes commanding the groundwater chemistry. Freshwater flushing from the recharge zones had thinned the entrapped sea water which has generated the present-day brackish water by a non-uniform fusion. The best-fit line of the plots of δD and δ18O of groundwater samples displays a slope lower than that of local meteoric water line (LMWL) and global meteoric water line (GMWL) which hints that isotopic constitution of the groundwater of the present area is primarily formed by evaporation before or in the recharging process. A wide range of δ18O values in groundwater suggests that these waters are not blended enough to remove dissimilarities in isotope configuration of recharge water. This also suggests that many groundwaters are a result of mixing of present-day recharge and an older integrant recharged under previously cooler climatic conditions. The groundwater samples are more depleted of oxygen at the shallower level. The depleted samples cluster around the Tolly's nala (canal) where upper aquitard is missing or < 10-m thick. The tritium values range between 0.70 and 15.02 which indicate the occurrence of 'sub-modern', 'a mix of modern and sub-modern water' and 'modern water'. It indicates mingling of isotope-depleted water from the Hugli River by means of Tolly's canal with relatively less-depleted groundwater of Kolkata's late Pleistocene aquifer. The tritium values and Cl/Br ratio of groundwater samples adjoining Tolly's canal and elsewhere refer the direct infiltration of 'modern wastewater and freshwater' which mixes with the 'sub-modern water' in the aquifer system.

Characterization of geological and lithological features in the area proximal to tritium-contaminated groundwater at the Semipalatinsk test site

The article presents the results of a study of groundwater contaminated with tritium in the vicinity of the 'Atomic Lake' - a crater filled with water as a result of a thermonuclear explosion on the territory of the former Semipalatinsk test site. This crater was created as part of an experimental thermonuclear explosion in 1965 with the aim of creating an artificial reservoir in arid areas. The study was carried out to identify the source of groundwater contamination near the crater formed from a thermonuclear test. There were two possible factors of pollution: the influence of contaminated water from the crater on the groundwater of the adjacent area, or groundwater polluting the water in the crater. It was necessary to find out the source of groundwater contamination and its connection with the water in the funnel. For this purpose, a study of the geological and lithological conditions of the territory adjacent to the funnel was carried out, which was carried out using drilling operations and hydrological measurements. Drilling work made it possible to study the depth of distribution of groundwater, hydrological work made it possible to determine the conditions of distribution of groundwater, as well as to take samples of groundwater. The assessment of the degree of groundwater contamination was carried out through water sampling and laboratory analysis. As a result, it was established that the geological and lithological conditions of the area limit the flow of contaminated groundwater to the water in the crater - the 'Atomic Lake'. Despite the fact that the waters in the crater from a thermonuclear explosion and the groundwater of the adjacent territory are contaminated with the radionuclide tritium, they have different sources of contamination and are not interconnected. Radionuclide analysis of groundwater showed that increased concentrations of tritium with a specific activity of up to 95 000 Bq/l are found in groundwater near the river bed. Shagan and this is due to the influence of the flow of groundwater coming from other parts of the landfill.

Biodistribution of Drug/ADA Complexes: The Impact of Immune Complex Formation on Antibody Distribution

The clinical use of therapeutic monoclonal antibodies (mAbs) for the treatment of cancer, inflammation, and other indications has been successfully established. A critical aspect of drug-antibody pharmacokinetics is immunogenicity, which triggers an immune response via an anti-drug antibody (ADA) and forms drug/ADA immune complexes (ICs). As a consequence, there may be a reduced efficacy upon neutralization by ADA or an accelerated drug clearance. It is therefore important to understand immunogenicity in biological therapies. A drug-like immunoglobulin G (IgG) was radiolabeled with tritium, and ICs were formed using polyclonal ADA, directed against the complementary-determining region of the drug-IgG, to investigate in vivo biodistribution in rodents. It was demonstrated that 65% of the radioactive IC dose was excreted within the first 24 h, compared with only 6% in the control group who received non-complexed 3H-drug. Autoradiographic imaging at the early time point indicated a deposition of immune complexes in the liver, lung, and spleen indicated by an increased radioactivity signal. A biodistribution study confirmed the results and revealed further insights regarding excretion and plasma profiles. It is assumed that the immune complexes are readily taken up by the reticuloendothelial system. The ICs are degraded proteolytically, and the released radioactively labeled amino acids are redistributed throughout the body. These are mainly renally excreted as indicated by urine measurements or incorporated into protein synthesis. These biodistribution studies using tritium-labeled immune complexes described in this article underline the importance of understanding the immunogenicity induced by therapeutic proteins and the resulting influence on biological behavior.

Tritiated stainless steel (nano)particle release following a nuclear dismantling incident scenario: Significant exposure of freshwater ecosystem benthic zone

Nuclear facilities continue to be developed to help meet global energy demands while reducing fossil fuel use. However, an incident during the dismantling of these facilities could accidentally release tritiated particles (e.g. stainless steel) into the environment. Herein, we investigated the environmental dosimetry, fate, and impact of tritiated stainless steel (nano)particles (1 mg.L-1 particles and 1 MBq.L-1 tritium) using indoor freshwater aquatic mesocosms to mimic a pond ecosystem. The tritium (bio)distribution and particle fate and (bio)transformation were monitored in the different environmental compartments over 4 weeks using beta counting and chemical analysis. Impacts on picoplanktonic and picobenthic communities, and the benthic freshwater snail, Anisus vortex, were assessed as indicators of environmental health. Following contamination, some tritium (∼16%) desorbed into the water column while the particles rapidly settled onto the sediment. After 4 weeks, the particles and the majority of the tritium (>80%) had accumulated in the sediment, indicating a high exposure of the benthic ecological niche. Indeed, the benthic grazers presented significant behavioral changes despite low steel uptake (<0.01%). These results provide knowledge on the potential environmental impacts of incidental tritiated (nano)particles, which will allow for improved hazard and risk management.

Synthesis of [3 H]Org24598 using in-house prepared [3 H]MeI

The synthesis of tritium-labelled glycine transporter 1 inhibitor Org24598 is reported. Because of the instability of the Org24598 skeleton under hydrogenation conditions, a synthetic approach using an in-house prepared tritium-labelled alkylating agent ([3 H]MeI, SA = 26.2 Ci/mmol) was employed. Alternative methods of labelling are discussed.

Negligible radiological impact of Indian nuclear power plants on the environment and the public: Findings from a 20-year study

Nuclear power plants, recognized for their extended operational life, minimal greenhouse gas emissions, and high-power density, are deemed as reliable energy sources. Nonetheless, concerns persist regarding the radioactive discharges from these plants and their potential impact on health and the environment. To comprehend the radiological implications of such releases, this study presents, for the first time, an analysis of radiological data from 7 Indian nuclear power plants (NPPs), collected by Indian environmental survey laboratories (ESL) over the past two decades (2000-2020). This dataset encompasses radioactivity concentrations in the atmospheric, aquatic, and terrestrial environments within a 30 km radius of each NPP, as well as the annual cumulative external gamma doses recorded by environmental thermoluminescence dosimeters (TLDs). The analysis yielded several key findings: (i) Radioactivity concentrations around the NPPs were low and comparable to values measured at other nuclear power plant sites worldwide; (ii) Tritium concentrations in receiving water bodies were <1 % of the internationally recommended limit of 10,000 Bq/l; (iii) The estimated total radiation doses to the public were at most 10 % of the stipulated regulatory dose limit of 1000 μSv and consistently decreased over the study period and (iv) Variations in doses among the NPP sites were primarily attributed to legacy technology used in specific reactors. These results indicate efficient and secure reactor operations and the minimal contribution of Indian nuclear power plants to anthropogenic doses in the country. The findings hold potential significance for reinforcing India's commitment to advancing its nuclear power program.

Application of portable liquid scintillation counter for on-field measurement of tritium in aqueous samples during radiation emergency

Screening of aqueous samples for 3H contamination is required to decide suitability of water intended for human consumption during radiation emergency. BARC, Trombay has recently procured Portable Triathler liquid scintillation counter as a screening tool for on-site response to radiation emergency. For this purpose, parameters like, different available scintillators, scintillator to sample ratio and influence of different capacity scintillation vials were optimized for 3H concentration measurement. The study indicated that for 7 mL vials, the optimized scintillator to sample ratio was 4:1 for Optiphase Hisafe II, Ultima Gold Ultra Low Level Tritium, Aqualight AB and Dioxane based scintillators whereas for Ultima Gold AB and Optiphase Hisafe III scintillators it was 3:1. In case of 20 mL vials, the ratio was optimized to 8:1 for all the above mentioned six scintillators. Additionally, the effect of applying counting efficiency using calibration curves generated using distilled water and that obtained using optimized scintillator to sample ratio in various spiked water samples was also studied. Results in 3H concentration (2000-5700 Bq/mL) indicate about ±10% deviation using both the methods for commercially available scintillators. However, in case of Dioxane based scintillator, the deviation was higher (20%). For analysis of 3H concentration ∼200 Bq/mL using commercially available scintillators results in higher deviation of about 21% due to unreliable quench indicating parameter for count rate less than 4000. The study indicated that calibration curves constructed using optimized parameters are universally applicable for determination of 3H concentration in wide variety of water samples.

Temporal variation of tritium concentration in monthly precipitation collected at a Difficult-to-Return Zone in Namie Town, Fukushima Prefecture, Japan

This article discusses tritium concentrations in monthly precipitation in part of the Difficult-to-Return Zone in Namie Town during 2012-2021. The tritium concentrations, which were measured with a low background liquid scintillation counter after carrying out an enrichment procedure, fluctuated seasonally from 0.10 ± 0.02 to 0.85 ± 0.02 Bq L-1. This range of concentrations is concluded to not be unusual based on comparisons with the concentrations at other sites and estimates of the past range of the concentrations. Moreover, no significant variations in observed tritium concentrations were observed due to decommissioning work at the Fukushima Dai-ichi Nuclear Power Plant. These results contribute to understanding the background level of tritium concentration in precipitation before the oceanic discharge of treated water from the Fukushima plant. In addition, this article evaluates the amount of tritium supplied to the ocean by terrestrial rainwater pouring into the Pacific Ocean via Ukedo River, which flows through Namie Town; this information will contribute to the discussion on the impact of the oceanic discharge of treated water.

Thoughts, perceptions and concerns of coastal residents regarding the discharge of tritium-containing treated water from the Fukushima Daiichi Nuclear Power Plant into the Pacific Ocean

BACKGROUND

As a part of the decontamination process after the Fukushima Daiichi Nuclear Power Plant accident of 2011, 1.32 million tonnes of tritium-containing water will be discharged from the power plant into the Pacific Ocean. Although radiobiological impacts of the treated water discharge on the public and the environment were reported to be minimal, Tomioka and Okuma locals expressed unease regarding the long-term recovery of their towns, which are economically dependent on the agricultural, fishery, and tourism sectors. This study presents thoughts, perceptions and concerns of Tomioka and Okuma locals regarding the discharge of FDNPP-treated water containing tritium into the Pacific Ocean to facilitate a more inclusive decision-making process that respects local stakeholder interests.

METHODS

Conducted from November to December 2022, surveys were mailed to current residents and evacuees aged 20 years or older registered with the town councils.

RESULTS

Out of 1268 included responses, 71.5% were from those > 65 years. 65.6% were unemployed, 76.2% routinely visited hospitals, and 85.5% did not live with children. 61% did not want to return to Okuma/Tomioka. Anxiety about radiation-related health effects (38.7%), consuming food produced in Okuma/Tomioka (48.0%) and genetic effects (45.3%) were low. >50% reported poor physical and mental health. 40% were acceptive, 31.4% were unsure, and 29.7% objected to the discharge plans. Multinomial regression analysis revealed that, compared to acceptive responders, those who objected were more likely to be female, unemployed, and have anxiety about radiation-related genetic effects and poor mental health. Unsure responders were similarly more likely to be female, anxious about radiation-related genetic effects and have poor mental health.

CONCLUSION

The poor mental health of the locals, connected to high levels of risk perception and anxiety about the loss of economic opportunities related to the discharge plans, must be addressed. The 30-year discharge process could handicap local industries and hamper post-disaster socioeconomic recovery due to the circulation of false rumours among consumers. These results highlight the need to actively involve residents in the towns' recovery process to address local concerns. The focus should be on the judicious combination of transparent science with the human aspect of recovery and narratives highlighting dialogues between local stakeholders and experts to enable the locals and the general public to make informed decisions about their protection and future.

Estimation of gross α-β and tritium activities in groundwater samples using LSC-TDCR technique in and around the geothermal region of Eastern India

The present study is an attempt to assess the radiogenic quality of groundwater on the basis of gross α, gross β and tritium (3H or H-3) activities in the Bakreswar-Tantloi geothermal region of Chotanagpur Plateau, West Bengal and Jharkhand, India. The aforesaid parameters in groundwater samples were measured using liquid scintillation counting triple to double coincidence ratio (LSC-TDCR) technique. Groundwater samples collected from Bakreswar-Tantloi geothermal region show gross α activities from below the minimum detectable activity (BMDA) to 0.5 ± 0.05 Bq/L, gross β activities from BMDA to 0.2 ± 0.01 Bq/L and H-3 activities from BMDA to 63.42 Bq/L. The average gross α, gross β and H-3 activities are also within the permissible limits prescribed by the World Health Organization (WHO). Though the annual effective doses in some samples were higher than the reference dose level of 0.1 mSv, the overall result suggests that the groundwater in the Bakreswar-Tantloi geothermal region is radiologically safe considering the radionuclides covered in this study.

Tritium contents in drinking and surface seawaters before the nuclear power plant planned in Sinop (Türkiye) and their radiological risks on human population

This study aims to determine the background levels of tritium radioisotope in drinking and seawater samples of Sinop province before the nuclear power plant was established in Sinop. In this context, a total of 174 water samples were collected, these are as follows: nine drinking water samples from the Sinop center and districts and 165 seawater samples from the seacoast from Samsun to Kastamonu. Tritium concentrations in the collected water samples were measured by the liquid scintillation counter. The minimum detectable activity for the method used was found to be 1.48 Bq/L. The tritium concentrations of the seawater and drinking water samples were found in the range of Collapse

Key Words Collapse

MESH Headings

• Adult
• Child
• Infant
• Humans
• Tritium
• Nuclear Power Plants
• Drinking Water
• Turkey

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Grants Collapse

Affiliation(s)

Serdar Dizman Department of Physics, Faculty of Arts and Sciences, Recep Tayyip Erdogan University, Rize 53100, Türkiye E-mail:
Feyza Zeynep Aşık Institute of Graduate Studies, Recep Tayyip Erdogan University, Rize 53100, Türkiye
Ali Erdem Özçelik Department of Landscape and Architecture (Geomatics Engineer), Faculty of Engineering and Architecture, Recep Tayyip Erdogan University, Rize 53100, Türkiye
Recep Keser Department of Basic Sciences, Faculty of Engineering, Samsun University, Samsun 55100, Türkiye
Filiz Korkmaz Görür Department of Physics, Faculty of Arts and Science, Bolu Abant İzzet Baysal University, Bolu 14100, Türkiye

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Effective methods for monitoring internal contamination among workers handling radioactive materials in various fields

This study aimed to develop effective methods for monitoring internal contamination among workers handling radioactive materials in various fields. A total of 160 workers from nuclear power plants, medical institutions, military units, and educational/research institutions were included in the study. The monitoring methods included urinalysis and whole-body counting (WBC) using a mobile radio bioassay laboratory (MRL). Gamma-emitting radionuclides were monitored using the MRL WBC system, and a separate pretreatment procedure was used for tritium measurement in urine samples. Gross beta-screening was performed using a liquid scintillation counting system. The results were evaluated on the basis of the established screening criteria and compared with the dose limits. Additionally, tritium concentrations in the bodies of workers in the vicinity of a heavy-water reactor was analysed to assess the association between tritium concentration and occupation. The results showed a wide distribution of tritium concentrations. Workers involved in fuel and maintenance tasks demonstrated the maximum exposure. Workers in medical facilities showed low levels of internal contamination, which was primarily related to tasks involving radioactive isotopes. Military personnel involved in equipment repair showed significant tritium contamination due to damage during repairs. Workers in educational and research institutions in general had low levels of internal contamination.

[3H]UR-JG102-A Radiolabeled Cyclic Peptide with High Affinity and Excellent Selectivity for the Neuropeptide Y Y4 Receptor

The family of human neuropeptide Y receptors (YRs) comprises four subtypes (Y1R, Y2R, Y4R, and Y5R) that are involved in the regulation of numerous physiological processes. Until now, Y4R binding studies have been predominantly performed in hypotonic sodium-free buffers using 125I-labeled derivatives of the endogenous YR agonists pancreatic polypeptide or peptide YY. A few tritium-labeled Y4R ligands have been reported; however, when used in buffers containing sodium at a physiological concentration, their Y4R affinities are insufficient. Based on the cyclic hexapeptide UR-AK86C, we developed a new tritium-labeled Y4R radioligand ([3H]UR-JG102, [3H]20). In sodium-free buffer, [3H]20 exhibits a very low Y4R dissociation constant (Kd 0.012 nM). In sodium-containing buffer (137 mM Na+), the Y4R affinity is lower (Kd 0.11 nM) but still considerably higher compared to previously reported tritiated Y4R ligands. Therefore, [3H]20 represents a useful tool compound for the determination of Y4R binding affinities under physiological-like conditions.

Tritium: Its relevance, sources and impacts on non-human biota

Tritium (³H) is a radioactive isotope of hydrogen that is abundantly released from nuclear industries. It is extremely mobile in the environment and in all biological systems, representing an increasing concern for the health of both humans and non-human biota (NHB). The present review examines the sources and characteristics of tritium in the environment, and evaluates available information pertaining to its biological effects at different levels of biological organisation in NHB. Despite an increasing number of publications in the tritium radiobiology field, there exists a significant disparity between data available for the different taxonomic groups and species, and observations are heavily biased towards marine bivalves, fish and mammals (rodents). Further limitations relate to the scarcity of information in the field relative to the laboratory, and lack of studies that employ forms of tritium other than tritiated water (HTO). Within these constraints, different responses to HTO exposure, from molecular to behavioural, have been reported during early life stages, but the potential transgenerational effects are unclear. The application of rapidly developing "omics" techniques could help to fill these knowledge gaps and further elucidate the relationships between molecular and organismal level responses through the development of radiation specific adverse outcome pathways (AOPs). The use of a greater diversity of keystone species and exposures to multiple stressors, elucidating other novel effects (e.g., by-stander, germ-line, transgenerational and epigenetic effects) offers opportunities to improve environmental risk assessments for the radionuclide. These could be combined with artificial intelligence (AI) including machine learning (ML) and ecosystem-based approaches.

Assessing the ecological risk of tritium and Carbon-14 discharge on cyanobacteria through metabolic profiling

The ecological risk posed by tritium (T) and carbon-14 (C-14) discharge from nuclear accidents has gained attention. This study evaluated the toxic impact of T and C-14 (at a concentration of 37 kBq/L for 15 days) on the cyanobacteria (Synechococcus elongatus). The results showed that the assimilation efficiency of cyanobacteria was significantly higher for C-14 than T, and the intracellular C-14 activity reached 30.62-40.58 kBq/kg. T and C-14 exposure had no significant effect on cell proliferation but impacted photosynthesis and respiration. T exposure increased the content of Ca, Mg, Na, P, K, and Mn, while C-14 exposure primarily affected trace element absorption in cyanobacteria. 31, 27, and 58 different metabolites (DEMs) were identified under T, C-14, and combined exposure conditions. These DEMs were enriched in the amino acid biosynthesis pathway, and nitrogen assimilation was one of the crucial pathways affected by T and C-14 exposure. The absorption of mineral elements by cyanobacteria was influenced by the variation in metabolites in the ABC transporter pathway caused by T and C-14 exposure. Our findings provide insights into the metabolic response of cyanobacteria to T and C-14 exposure and will help to guide the ecological risk evaluation of nuclear accidents.

Feasibility Study to Byproduce Medical Radioisotopes in a Fusion Reactor

Currently, international nuclear fission reactors producing medical isotopes face the problem of shutdown and maintenance, decommissioning, or dismantling, while the production capacity of domestic research reactors for medical radioisotopes is inadequate, and the supply capacity for medical radioisotopes faces major challenges in the future. Fusion reactors are characterized by high neutron energy, high flux density, and the absence of highly radioactive fission fragments. Additionally, compared to fission reactors, the reactivity of the fusion reactor core is not significantly affected by the target material. By building a preliminary model of the China Fusion Engineering Test Reactor (CFETR), a Monte Carlo simulation was performed for particle transport between different target materials at a fusion power of 2 GW. The yields (specific activity) of six medical radioisotopes (¹⁴C, ⁸⁹Sr, ³²P, ⁶⁴Cu, ⁶⁷Cu, and ⁹⁹Mo) with various irradiation positions, different target materials, and different irradiation times were studied, and compared with those of other high-flux engineering test reactors (HFETR) and the China Experimental Fast Reactor (CEFR). The results show that this approach not only provides competitive medical isotope yield, but also contributes to the performance of the fusion reactor itself, e.g., tritium self-sustainability and shielding performance.

Assessing OBT formation and enrichment: ROS signaling is involved in the radiation hormesis induced by tritium exposure in algae

Tritium is the main component of radioactive wastewater from nuclear power plants and can be migrated into organisms to form organically bound tritium (OBT), which may pose a potential risk to aquatic ecosystem. Hence, it is essential to monitor OBT conversion in the presence of tritium exposure. In this study, the effects of pretreatment methods such as digestion on the recovery of tritium were discussed. It was found that microwave digestion pretreatment could improve the recovery of tritium by up to 90 % and allow OBT measurement with a small sample size equivalent to about 60 mg (dry weight). In addition, the efficiency of OBT transformation was different among biological samples, and the radiation hormesis phenomenon was induced by tritium exposure (3.7 × 10⁶ Bq/L) in microalgae Chlorella vulgaris（C. vulgaris）. The tritium exposure may induce radiation hormesis through the reactive oxygen species (ROS) signaling pathway, thus improving the photosynthetic capacity and metabolism level of C. vulgaris. Furthermore, enhancement of photorespiration metabolism and the antioxidation system may be important means for C. vulgaris to balance damage by tritium radiation. This study provides insights for further investigating OBT behavior, and will contribute to understanding the equilibrium damage mechanism of algae exposed to tritium.

Evaluating potential groundwater recharge in the unsteady state for deep-rooted afforestation in deep loess deposits

Groundwater recharge reduces due to high transpiration from shallow-rooted to deep-rooted afforestation. However, reaching a steady state in recharge process is challenging and no methods are available for assessing potential groundwater recharge under unsteady state. Hence, this study developed a new method to quantify groundwater recharge in the unsteady state by (1) calculating the water age (A₂) at maximum root depth (D₂) for deep-rooted afforestation using the chloride accumulative age method; (2) determining the soil depth (D₁) corresponding to A₂ under shallow-rooted vegetation using the multi-year average pore water velocity multiplied by A₂; (3) calculating the reduction in groundwater recharge (∆R) from shallow- to deep-rooted afforestation as the depth difference multiplied by the average water content between D₁ and D₂, divided by stand age. The average groundwater recharge for deep-rooted afforestation is equal to the average annual groundwater recharge under shallow-rooted vegetation minus ∆R. Soil cores with >25 m soil profiles below four land-use types of Hippophae rhamnoides Linn. (H. rhamnoides), Platycladus orientalis (L.) Franco (P. orientalis), Robinia pseudoacacia L. (R. pseudoacacia), and grassland were collected to measure soil water content, root distribution, and chloride and tritium contents. The results revealed that: (1) maximum root depths were 11.0 ± 0.5, 20.2 ± 1.2, and 22.6 ± 0.8 m, with soil water deficits of 373.48, 823.65, and 1847.92 mm under H. rhamnoides, P. orientalis, and R. pseudoacacia, respectively; (2) groundwater recharge following land-use change has not reached a steady state; (3) an average annual groundwater recharge was 89.12 mm yr^-1 under grassland, amounting to 16 % of the average annual precipitation; deep-rooted afforestation did not significantly differ, with 83.55, 84.91, and 85.65 mm yr^-1 under H. rhamnoides, P. orientalis, and R. pseudoacacia, respectively. This study contributes to a rational assessment of groundwater resources under unsteady state during land-use change.

Shallow Quaternary groundwater in the Lake Chad basin is resilient to climate change but requires sustainable management strategy: Results of isotopic investigation

Within the Lake Chad Basin, the unconfined Quaternary aquifer offers permanent and easy access to water resources. This transboundary regional aquifer is shared by Chad, Niger, Nigeria and Cameroon and extends over ~500,000 km². Climatic conditions and repeated droughts as well as the intensification of agriculture in the region have multiple negative impacts on the aquifer such as changes in groundwater level and its quality. Being a strategic water resource for the whole Chadian region, the groundwater potential of the Quaternary aquifer must be better characterized and understood to evaluate its resilience to climate change and anthropogenic impact. Stable isotopes and tritium of the water molecule were used to estimate water origin and residence time at the regional scale and to elucidate the interconnections between the different hydrological and hydrogeological components. Results show active recharge processes to the Quaternary aquifer as well as dynamic connections with surface waters (both river courses and wetlands) but also indicate less dynamic behavior of the Quaternary groundwater resource in some areas of the region. Based on the isotopic investigations, the Quaternary aquifer in the Chad basin was found to be resilient to climate change but its hydrogeological specificities (dependence to surface water from the upstream basins and transboundary nature of its structure) can make it prone to inadequate management strategies.

Deciphering natural and anthropogenic nitrate and recharge sources in arid region groundwater

Recently, the subsoils of ephemeral stream (arroyos) floodplains in the northern Chihuahuan Desert were discovered to contain large naturally occurring NO₃^- reservoirs (floodplain: ~38,000 kg NO₃-N/ha; background: ~60 kg NO₃-N/ha). These reservoirs may be mobilized through land use change or natural stream channel migration which makes differentiating between anthropogenic and natural groundwater NO₃^- sources challenging. In this study, the fate and sources of NO₃^- were investigated in an area with multiple NO₃^- sources such as accidental sewer line releases and sewage lagoons as well as natural reservoirs of subsoil NO₃^-. To differentiate sources, this study used a large suite of geochemical tools including δ¹⁵N[NO₃], δ¹⁸O[NO₃], δ¹⁵N[N₂], δ¹³C[DIC], ¹⁴C, tritium (³H), dissolved gas concentrations, major ion chemistry, and contaminants of emerging concern (CEC) including artificial sweeteners. NO₃^- at sites with the highest concentrations (25 to 229 mg/L NO₃-N) were determined to be largely sourced from naturally occurring subsoil NO₃^- based on δ¹⁵N[NO₃] (<8 ‰) and mass ratios of Cl^-/Br^- (〈100) and NO₃^-/Cl^- (>1.5). Anthropogenic NO₃^- was deciphered using mass ratios of Cl^-/Br^- (>120) and NO₃^-/Cl^- (<1), δ¹⁵N[NO₃] (>8 ‰), and CEC detections. Nitrogen isotope analyses indicated that denitrification is fairly limited in the field area. CEC were detected at 67 % of sites including ³H dead sites (<1 pCi/L) with low percent modern carbon-14 (PMC; <30 %). Local supply wells are ³H dead with low PMC; as ³H does not re-equilibrate and ¹⁴C is very slow to re-equilibrate during recirculation through infrastructure, sites with low PMC, ³H < 1 pCi/L, and CEC detections were interpreted as locations with substantial anthropogenic groundwater recharge. Neotame was used to identify locations of very recent (<15 years before present) or ongoing wastewater influxes to the aquifer. This work shows the important influence of naturally occurring subsoil NO₃^- reservoirs on groundwater in arid regions and the major contribution of artificial recharge.

Isolation and Characterization of 1-Hydroxy-2,6,6-trimethyl-4-oxo-2-cyclohexene-1-acetic Acid, a Metabolite in Bacterial Transformation of Abscisic Acid

We report the discovery of a new abscisic acid (ABA) metabolite, found in the course of a mass spectrometric study of ABA metabolism by the rhizosphere bacterium Rhodococcus sp. P1Y. Analogue of (+)-ABA, enriched in tritium in the cyclohexene moiety, was fed in bacterial cells, and extracts containing radioactive metabolites were purified and analyzed to determine their structure. We obtained mass spectral fragmentation patterns and nuclear magnetic resonance spectra of a new metabolite of ABA identified as 1-hydroxy-2,6,6-trimethyl-4-oxo-2-cyclohexene-1-acetic acid, which we named rhodococcal acid (RA) and characterized using several other techniques. This metabolite is the second bacterial ABA degradation product in addition to dehydrovomifoliol that we described earlier. Taken together, these data reveal an unknown ABA catabolic pathway that begins with side chain disassembly, as opposed to the conversion of the cyclohexene moiety in plants. The role of ABA-utilizing bacteria in interactions with other microorganisms and plants is also discussed.

Damages of DNA in tritiated water

Tritium is a radioisotope of hydrogen emitting low energy β-rays in disintegration to ³He. DNA molecules are damaged mainly by β-ray irradiation, and additional damages can be induced by break of chemical bond by nuclear transmutation to inert ³He. Deep knowledges of the mechanisms underlying DNA damages lead to better understanding of biological effects of tritium. This chapter reviews recent experimental and computer simulation activities on quantitative evaluation of damage rates by β-ray irradiation and nuclear transmutation. The rate of DNA double-strand breaks in tritiated water has been examined using a single molecule observation method. The effects of β-ray irradiation were not noticeable at the level of tritium concentration of ∼kBq/cm³, while the irradiation effects were clear at tritium concentrations of ∼MBq/cm³. The factors affecting on the DSB rate are discussed. A new image processing method for the automatic measurement of DNA length using OpenCV and deep learning is also introduced. The effects of tritium transmutation on hydrogen bonds acting between the two main strands of DNA have been examined using molecular dynamics simulations. The study showed that the collapsing of DNA structure by the transmutation can be quantitatively evaluated using the root mean square deviation of atomic positions.

Influence of climate on groundwater fluoride in different climatic domains in a hard rock terrain of Sri Lanka: implications to community health

Health risks associated with excessive intake of fluoride through drinking water are one of the geoenvironmental health problems observed in many parts of the world, mainly in countries of the humid tropical belt, including Sri Lanka. Fluoride-related health problems are widespread in the dry climatic region compared to the wet climatic zone of Sri Lanka. The potential health risks of fluoride for communities in a river basin which drains through two climatic zones, viz. wet and dry zones, were investigated in this study. Sixty-three groundwater samples were collected from wells in the Walawe river basin during pre- and post-monsoon periods. From collected samples, ten selected samples were analyzed for their tritium (³H) levels to find out the approximate resident time of groundwater. In the river basin, the dry zone segment is characterized by elevated levels of fluoride (> 1.0 mg/L) in groundwater. Groundwater fluoride in the region was primarily of geogenic origin. The tritium values showed older groundwater contained higher fluoride levels, showing a increased dissolution of fluoride-bearing minerals. The hazard quotient (HQ_fluoride) showed that about 45% of pre- and 55% of post-monsoon groundwater samples in the dry zone area were unsuitable for drinking purposes for school children who are vulnerable to non-carcinogenic risks and dental fluorosis. This study emphasizes the need for continuous water quality monitoring and mitigation measures to ensure the health of residents.

STUDY OF BIOLOGICAL EFFECTS OF TRITIUM IN MICE

The mutation, apoptosis and chromosomal aberration induced by tritiated water (HTO) in spleen T lymphocytes of mice were investigated and compared with those by acute or chronic 137Cs gamma irradiation. p53 wild-type (p53+/+) and null (p53-/-) mice were exposed to tritium (3H) beta rays via a single injection of HTO. 137Cs gamma irradiation was carried out at dose-rate of 0.86Gy min-1 (acute) and at a low dose-rate (0.71-0.09 mGy min-1) that mimicked internal exposure (gamma simulation-irradiation). Each dose of irradiation was 3Gy. When compared on the basis of the induced TCR variant fractions in p53-/- mice at 3Gy, 3H beta rays appeared to be more mutagenic than chronic gamma ray reference. On the other hand, both of the frequency chromosomal aberration was not different significantly between HTO injected and 137Cs gamma irradiated mice.

DOSE AND DOSE-RATE DEPENDENCE OF DSB-TYPE MUTANTS INDUCED BY X-RAYS OR TRITIUM BETA-RAYS: AN APPROACH USING A HYPERSENSITIVE SYSTEM

To evaluate biological effects triggered by low levels of radiation, we established a uniquely sensitive experimental system to detect somatic mutations. By using the system, we found that mutant frequencies induced by X-rays were statistically significant at doses over 0.15 Gy, and a linear dose relationship with the mutant frequency was observed at doses over 0.15 Gy. The mutation spectra analysis revealed that mutation events generated by X-ray doses below 0.1 Gy were similar to those observed in unirradiated controls. In addition, a significant inflection point for both, the mutant frequency and the mutation spectra, was found at dose-rates around 11 mGy/day when cells were cultured in medium containing tritiated water. Because induced radiation-type events presented a clear dose/dose-rate dependency above the critical dose or the inflection point, these observations suggest that mutation events generated by radiation could change at a threshold dose-rate or a critical dose.

PERFORMANCE EVALUATION OF COMMERCIAL SCINTILLATION COCKTAILS FOR LOW-LEVEL TRITIUM COUNTING BY HIGH-CAPACITY LIQUID SCINTILLATION COUNTER

Low-background liquid scintillation counter is one of the popular measuring instruments used to investigate tritium radioactivity in environmental media. These instruments require the liquid sample and organic solvent to be mixed for tritium measurement. In the European Union, the registration, evaluation, authorization and restriction of chemicals regulation was established to control the use of chemical substances of very high concern. It is important to find continuously available alternative reagents. In this paper, a performance evaluation was conducted using four scintillation cocktails according to Japanese conventional procedure; although one of them, Gold Star LT2, contains nonylphenol ethoxylate, it will continue to be available for research and development. From the evaluation results it was confirmed that Gold Star LT2 would be a satisfactory alternative scintillator, which is similar performance of Ultima Gold LLT.

ASSESSMENT OF THE COMMITTED EFFECTIVE DOSE EQUIVALENT AND ITS UNCERTAINTY FROM INCIDENTAL INTERNAL TRITIUM EXPOSURE

The objective of the study was to estimate the committed effective dose equivalent from internal tritium exposure and its uncertainty in case of tritium incident at Mayak PA. According to worker's self-report, he had been exposed as a result of pouring "heavy" water over himself while performing technological operation in September 2019. Two-component exponential model of tritiated water (HTO) excretion including fast and slow phases was used to describe HTO content in the body. The individual's specific value of tritium biological half-life in the fast phase was 8.9 days, which is close to the average value of 10 days in the ICRP model. The slow-phase HTO excretion fraction is two orders of magnitude lower than the corresponding value in the ICRP model. The calculated committed effective dose equivalent (CEDE) due to tritium intake (7.4 mSv) depended mostly on fast-phase excretion. The uncertainty factor calculated as ratio of the 97.5% quantile and the mean value was equal to 1.14. The contribution of the slow-phase excretion to the CEDE due to internal exposure was as low as from 0.1 to 0.2% of total CEDE. This demonstrates that after the case of a single intake of tritium, which we studied, the CEDE is determined mostly by the excretion in the fast phase. The metabolized organically bound tritium dose fraction was in the range from 0.3 to 2.0%. The use of all the results of the measurement of HTO activity concentration in urine made it possible to obtain a lower estimate of the uncertainty of the CEDE of internal exposure in comparison with the use of only the first measurement result.

Chemical and isotopic composition of CO2-rich magnesium-sodium-bicarbonate-sulphate-type mineral waters from volcanoclastic aquifer in Rogaška Slatina, Slovenia

Bottled natural mineral waters from an andesitic aquifer in Slovenia are enriched in magnesium (1.1 g/l), sulphate (2.2 g/l) and dissolved inorganic carbon (204 g/l). We analysed major ions, trace elements, tritium activity, ¹⁴C, δ¹⁸O_H2O, δ²H_H2O, δ¹³C_DIC, gas composition and noble gases in six wells. In addition, ⁸⁷Sr/^/86Sr, δ³⁴S_SO4 and δ¹¹B were analysed here for the first time. Stable isotopes with δ¹⁸O = -11.97 to -10.30‰ and δ²H = -77.3 to -63.8 confirm meteoric origin. CO₂ degassing is evident at three wells, causing the oxygen shift of about -1.3‰. Tritium activity was detectable only in the shallowest well, where the freshwater component was dated to the 1960s. δ¹³C_DIC in five waters is -1.78 to + 1.33‰, typical of carbonate dissolution. Radiocarbon is low, 1.03-5.16 pMC. Chemical correction with bicarbonate concentration and δ¹³C correction methods gave best mean residence times, slightly longer than previously published. Sulphate has δ³⁴S 26.6-28.9‰ and δ¹⁸O 8.9-11.1‰ due to dissolution of evaporites in carbonate rocks. Boron at concentrations of 1.2-6.1 mg/l has two origins: δ¹¹B = 11.3-16.4‰ from hydrothermal alteration and δ¹¹B = 26.6-31.7‰ from carbonate dissolution. Strontium at concentrations of 0.5-22.0 mg/l has ⁸⁷Sr/^/86Sr, indicating three sources: 0.7106 for Miocene clastic rocks, 0.7082 for Triassic carbonates and 0.7070 for Lower Oligocene andesitic rocks. CO₂ represents the majority of the dissolved (> 98.84 vol%) and separated gas (> 95.23 vol%). Methane is only found in two wells with a max. of 0.30 vol%. All waters show excess helium and 16-97% of mantle-derived helium. Since all show subsurface degassing, the paleo-infiltration temperature could not be calculated.

Response of the Christchurch groundwater system to exploitation: Carbon-14 and tritium study revisited

The Christchurch groundwater system is an exceptional water resource with very high drinking water quality supplying all the water requirements of the city. The groundwater system has changed over the years because of rising groundwater abstraction due to increasing population and development. The present (2017) data revealed slightly older ¹⁴C ages and increasingly steep west-east age gradients compared to the earlier work from 1976 to 2006, showing continued upflow of deep water into the exploited aquifers which is much older on the east (coastal) side than on the west (inland) side. In addition, the ³H ages for wells on the west side of the system are often much younger than their ¹⁴C ages showing that there is input of young shallow water to the wells in addition to the deep water input. Application of a binary model identifies the ages and amounts of the two components, showing that the young component is becoming younger although smaller as a proportion of the flow, and the old component from depth is becoming larger. Newly completed wells near the Waimakariri River have allowed identification of the young component, which is almost entirely composed of very young Waimakariri River seepage at all depths and therefore has very little chemical loading. Instead any chemical input (e.g. chloride, nitrate) to the Christchurch aquifers is being brought in by the old deep component which on the western side of the Christchurch system is derived from rainfall recharge on the developing Ashley-Waimakariri Plains area (plus river seepage). Chemical traces of this deep input from the northwest are at present very subtle, although more appreciable signals are seen in some wells further to the north of Christchurch. In the future, slowly increasing chemical input to the Christchurch aquifers on the west side of the system is to be expected as abstraction increases.

Quantitative prediction of dynamic HTO migration behavior in the soil and non-negligible evapotranspiration effect

Tritium is mainly produced from nuclear facilities apart from nuclear tests. After being released to the environment, tritium would cause water & food contamination due to its radioactivity and mobility. This study investigated dynamic characteristics of tritiated water (HTO) migration in the soil and evapotranspiration effect based on realistic environmental conditions. The influences of soil types and time-varying environmental factors such as precipitation and evapotranspiration on tritium migration behaviors were specially discussed under normal continuous and accidental short-term release conditions. Radiation dose caused by dynamic tritium evapotranspiration was evaluated. The results show that tritium migration velocity in the soil is much higher than other particles such as cesium due to negligible adsorption of tritium by the soil. Tritium migration in the soil from up to down is attributed to precipitation. On the contrary, evapotranspiration factor would carry tritium movement along the opposite direction. A considerable fraction approximately 55% of tritium deposited in the soil would be reemitted into the air from bare soil and plant leaves due to evapotranspiration effect. Subsequently, the radiation dose caused by second plume due to evapotranspiration effect might be higher than the first plume due to direct release from the nuclear facility under routine discharge.

Experimental measurements of the bacterial oxidation of HT in soils: Impact over a zone influenced by an industrial release of tritium in HT form

Tritium is a radionuclide released to the atmosphere by nuclear industries in various forms, mainly HTO and to a lesser extent HT. However, some nuclear sites may emit predominantly HT in the atmosphere. The HT is oxidized to HTO essentially in the top cm of soils, and that the formed HTO is then possibly released into the atmosphere. HTO is an assimilable form by plants. Therefore, it is important to understand the environmental behaviour of HT. In this work, we adapt the bacterial oxidation model of HT in soils of Ota et al. (2007) by laboratory experiments on soils typical of western France, and we have in particular adapted the frequency factor A and the Michaelis-Menten enzymatic reaction parameter (Km) on the basis of an Arrhenius equation in function of the porosity of the soil. We then applied this model to the environment near the reprocessing plant of Orano la Hague (France), which emits a significant amount of HT. Based on the adapted model, and knowing the atmospheric variations of HTO and HT over the period 2013-2016, we estimated that the mean HTO activity in soil due to atmospheric HT reached 0.6 Bq.L^-1 (with a peak value of 5 Bq.L^-1) while the mean value with all sources taken into account is 6.2 Bq.L^-1. Then, in an environment such as that surrounding the Orano La Hague plant, where near-field atmospheric HT activity is very high, the bacterial oxydation contribution to produce HTO in the soil can be considered as approximately 10%. The flux to the atmosphere from these source representing approximately. 1.5 Bq.m^-2.d^-1. If we consider an area of 2 km around the plant (i.e. 13 km²), we estimate 218 Bq.s^-1 of HTO was released by the soil, representing less than 0.1% of the direct atmospheric release of HTO around the site. From this work, it appears clear that this secondary source term from the soil is insignificant at this specific site.

Cerebral and extracerebral distribution of radioactivity associated with oxytocin in rabbits after intranasal administration: Comparison of TTA-121, a newly developed oxytocin formulation, with Syntocinon

Autism spectrum disorder (ASD) is a neurodevelopmental disorder associated with deficits in social interactions/communication. Despite the large number of ASD patients, there is no drug approved to treat its core symptoms. Recently, Syntocinon (oxytocin nasal spray) has been reported to have a therapeutic effect on ASD. However, the disadvantage of Syntocinon for ASD treatment is that 6 puffs/administration are required to achieve the effective pharmacological dose. Furthermore, there are no published reports evaluating the cerebral distribution profile of oxytocin after intranasal administration. TTA-121 is a newly developed intranasal oxytocin formulation with high bioavailability produced by optimizing the physicochemical properties. In this study, we prepared the same formula as Syntocinon as the control formulation (CF), and the cerebral and extracerebral distribution of oxytocin in rabbits after single intranasal administration of ³H-labeled oxytocin formulations—[³H]TTA-121 and [³H]CF were examined and compared. The area under the concentration-time curve to the time of the last quantifiable concentration (AUC_t) in the whole brain was 3.6-fold higher in the [³H]TTA-121 group than in the [³H]CF group, indicating increased delivery of radioactivity to the brain by TTA-121 than by CF. Since the distribution profiles showed no notable differences in radioactivity between the olfactory bulb and trigeminal nerve, intranasally-administered oxytocin was probably transferred to the brain via both pathways. The results also showed an increase in radioactivity in the prefrontal area and the precuneus, which are probable sites of pharmacological action as shown in clinical studies using functional magnetic resonance imaging (fMRI), confirming that intranasally-administered oxytocin could reach these tissues.

High-Resolution Tritium Profile in an Ice Core from Camp Century, Greenland

We measure ³H in an ice core from Camp Century. The temporal distribution of ³H concentration in the ice core corresponds generally well with the historical record of explosive yields of atmospheric nuclear weapons tests. Maximum ³H values observed in 1962-1963 are comparable to those in ice core or precipitation in many other locations in the Northern Hemisphere. There is no indication that significant ³H contamination was locally released into the air during the operation of the Camp Century reactor. It is, however, somewhat surprising that several prominent ³H peaks are still observed after 1980. We suggest that these are associated with airborne ³H releases from the civil nuclear industry. A wavelet analysis during 1970-2017 indicates the primary frequency of variability in the ³H record is annual ³H peaks. These annual peaks can be combined with the ³H spikes from global fallout of known nuclear weapons tests to benchmark and evaluate theoretical ice core dating scales back to the 1950s. A positive correlation is observed between annual ³H average concentration and variability of Arctic Oscillation (AO). This highlights the value of ³H as a potential tracer for air masses and airborne pollutants in the Arctic.

New insights into the accessibility of native cellulose to environmental contaminants toward tritium behavior prediction

Tritium speciation and behavior in the environment directly rely on accessible OH groups of organic molecules and their hydrogen exchangeability properties. As one of the most widespread biomolecule, cellulose role in reducing the exchange capacity of the hydrogen atom has been previously highlighted experimentally in various environmental matrices. In this paper, a robust and reliable T/H gas-solid isotopic exchange procedure has been implemented to assess the OH group accessibility of native celluloses with an increasing degree of crystallinity. A linear relationship was found between hydroxyl reactivity and the crystallinity index (CrI) of native celluloses, as determined by the analysis of their crystalline structure from XRD characterization. The application of the obtained linear experimental model to cellulosic materials was then evaluated and an acceptable minimum value of 12% for the CrI parameter on environmental matrices could thus be established. The authors have therefore proposed an environmental matrices relevant and efficient analytical process in order to determine the accessibility of native cellulose hydroxyl groups to tritium in the environment from a single and quick sample characterization procedure.

The status and trends in radioactive contamination of groundwater at a LLW-ILW storage facility site near Sosnovy Bor (Leningrad region, Russia)

The article presents results of field studies at a site of radioactive waste storage and disposal facilities (the so-called LD RosRAO site, Sosnovy Bor, Leningrad region, Russia). The objective of the study is to overview the history and occurrence of groundwater contamination to answer the question whether the radioactive plume is historical (formed due to accidents, which happened at the beginning of the operations with the radioactive waste) or the release of radioactive solutions to groundwater is still occurring. The main method used to study the evolution of radioactive contamination is to analyze long-term observations of tritium, total alpha, and total beta activities in groundwater samples. The role of the hydrogeological conditions of the site, such as flow parameters, groundwater flow pattern, inter-aquifer downward groundwater leakage, and water-table fluctuations, in the evolution of contamination plumes has also been analyzed. In the field investigations, the integrity of the storage buildings to potential leaks was confirmed by different indirect methods. It was concluded that there is currently no significant release of radioactive components into groundwater at the LD RosRAO site and that the present conditions correspond to the stage of rehabilitation of the groundwater environment.

Development of a Fission Neutron Spectrum from a D-T Neutron Generator by Spectrum Subtraction Technique

ABSTRACT

Californium-252 (252Cf) is considered essential by the National Institute of Standards and Technology for the calibration of neutron instrumentation and dosimetry. Californium-252 has a relatively short half-life of 2.645 y; consequently, it must be replaced frequently to produce an adequate neutron flux for calibration. The user community is currently looking for a replacement for 252Cf. The patented technology described herein has a high probability of being that replacement. A preferred method to replace 252Cf would use an affordable and easily maintained neutron source that generates neutrons in an energy spectrum as close to that of 252Cf as possible. Deuterium-tritium (D-T) neutron generators are both affordable and easily maintained, which makes them highly attractive for replacing 252Cf. The patented technology discussed in this paper simulates the 252Cf fission spectrum through a D-T neutron generator by using spectral subtraction. The primary spectrum is built using principally (n,xn) and (n,n') reactions in a variety of materials. In conjunction with the primary spectrum, an engineered background spectrum is generated using a second set of materials. This engineered background spectrum corrects for differences between the primary and desired spectra. This subtraction technique generates a spectrum very similar to 252Cf while maintaining a reasonable flux. Further, by choosing different scattering materials, any fission spectrum can be matched, including the thermal and epithermal components. This flexibility expands the potential use of this technology beyond simulating 252Cf to any desired neutron spectrum below 14 MeV.

Transport and dispersion of tritium from the radioactive water of the Fukushima Daiichi nuclear plant

Japan recently announced plans to discharge over 1.2 million tons of radioactive water from the Fukushima Daiichi Nuclear Power Plant (FDNPP) into the Pacific Ocean. The contaminated water can poses a threat to marine ecosystems and human health. To estimate the impact of the plan, here, we developed a three-dimensional global model to track the transport and dispersion of tritium released from the radioactive water of the FDNPP. The pollution scenarios for four release durations (1 month, 1 year, 5 years, and 10 years) were simulated. The simulation results showed that for the release in short-duration scenarios (1 month and 1 year), the peak plume with high tritium concentration shifted with the currents and finally reached the northeastern Pacific. For the long-duration scenarios (5 years and 10 years), the peak plume of the contaminated water was confined to coastal regions east of Japan.

Tritium in environmental objects in the area affected by FSUE Mayak Production Association in 2014-15

Comparison of tritium volume activity (VA) rates in objects of environment in the Mayak Production Association (Mayak PA) affected area in the period from 2014 to 2015 with tritium VA rates in the same or similar objects of environment measured in the period from 2001 to 2013. Water samples from environmental objects-precipitations, ponds, wells-were the material for this research. Tritium VA in various environmental objects was measured using liquid scintillation method. The results were processed using parametric and nonparametric methods of statistical analysis. In samples collected in 2014-15 from open reservoirs located in Mayak PA affected area tritium VA was 1.4 times lower than the level of tritium VA in water samples from the same reservoirs collected in 2001-03. There was no statistically significant difference between tritium VA in water samples from the same open reservoirs collected in periods 2009-12 and 2014-15. Tritium VA in the water sample from production reservoir R-2 (lake Kyzyltash) in 2015 made 11 200 Bq l^-1that was 1.7 times higher than average rate in 2007-09. In water samples collected in 2014 from 11 wells and boreholes located in the affected area of Mayak PA tritium VA made in average 22 ± 5 Bq l^-1. No statistically significant difference was detected in water samples taken from boreholes in 2005-06 and in 2014. Comparison of median values revealed a statistically significant 3.2 times decrease of tritium VA in samples of daily precipitations in Ozyorsk in the time interval between 2007 and 2014. In single samples of daily precipitation in 2007, 2014 and 2015 tritium VA in Ozyorsk made 1020, 145 and 3500 Bq l^-1respectively that in respect exceeded the median values 29 times in 2007, 13 times in 2014 and 160 times in 2015. This could indicate irregular tritium air emissions from Mayak PA that provides ground for necessity of tritium VA monitoring not only in daily precipitation but also in air vapor condensate. Decrease of tritium VA in water samples from open reservoirs from the period of 2001-03 to 2014-15 as well as decrease of the levels of tritium VA in samples of daily precipitation from 2007 to 2014 could be an evidence of possible decrease of tritium atmospheric emission from Mayak PA.

Effects of gamma ionizing radiation exposure on Danio rerio embryo-larval stages - comparison with tritium exposure

The objective was to investigate the effects of ionizing radiation induced in zebrafish early life stages by coupling responses obtained at the molecular (genotoxicity, ROS production, gene expression) and phenotypic (tissue alteration, embryo-larval development) levels. Here we present results obtained after exposure of 3 hpf larvae to 10 days of gamma irradiation at 3.3 × 10¹, 1.3 × 10² and 1.2 × 10³ µGy/h, close to and higher than the benchmark for protection of ecosystems towards ionizing radiations of 10¹ µGy/h. Dose rates used in these studies were chosen to be in the 'derived consideration reference level' (DCRL) for gamma irradiation where deleterious effects can appear in freshwater fish. Also, these dose rates were similar to the ones already tested on tritium (beta ionizing radiation) in our previous work, in order to compare both types of ionizing radiation. Results showed that gamma irradiation did not induce any effect on survival and hatching. No effect was observed on DNA damages, but ROS production was increased. Muscle damages were observed for all tested dose rates, similarly to previous results obtained with tritium (beta ionizing radiation) at similar dose rates. Some molecular responses therefore appeared to be relevant for the study of gamma ionizing radiation effects in zebrafish.

Tritium concentrations and consequent doses in bottled natural and mineral waters sold in Turkey and Azerbaijan

In this study, tritium levels in commercially sold bottled natural and mineral waters in Turkey and Azerbaijan were determined. Tritium measurements were performed using Liquid Scintillation Counter (PerkinElmer TriCarb 2910 TR). 16 natural and 11 mineral samples from Turkey and 7 natural and 8 mineral samples from Azerbaijan, for a total of 42 commercially sold water samples were analyzed. The Minimum Detectable Activity (MDA) value for the method used was found as 1.69 Bq L^-1. In total, 7 of the natural water samples and 8 of the mineral water samples were found to be below the MDA value. The average activity concentrations in natural and mineral water samples were found as 2.23 ± 0.90 Bq L^-1 and 2.51 ± 0.90 Bq L^-1 for Turkey and 2.69 ± 0.91 Bq L^-1 and 2.43 ± 0.89 Bq L^-1 for Azerbaijan, respectively. In addition, annual effective dose rates and lifetime cancer risk values for the water samples were calculated. These radiological parameters were compared with the values recommended by international organizations. The results demonstrated that consumption by humans of the studied waters would not constitute any health risks in terms of tritium.

Tritium labelling to study humic substance-nanodiamond composites

Nanodiamonds produced by the detonation method are used as lubricants, polishing compositions, polymer composites, etc. To reveal how nanodiamonds differ in terms of surface properties and interact with natural organic matter, we used tritium-labelled humic substances to quantitively describe their adsorption onto the nanodiamond surface. It was shown that the adsorption of humic substances onto nanodiamonds resulted in fractionation of humic substances that was strongly dependent on the zeta potential of nanodiamonds in water but did not significantly affect the uptake of nanodiamonds by wheat seedlings. The uptake of nanodiamond particles by plants was determined by the functional composition of the particle surface.

Chronic oral methylphenidate treatment in adolescent rats promotes dose-dependent effects on NMDA receptor binding

AIM

Examine the effects of chronic oral Methylphenidate (MP) treatment on the N-Methyl-D-aspartic acid (NMDA) glutamate receptor binding in the rat brain using a previously established drinking paradigm that has been shown to deliver MP with similar pharmacokinetic profile as observed clinically.

MAIN METHODS

Briefly, rats were divided into three treatment groups of water, low dose MP (LD; 4/10 mg/kg), or high dose MP (HD; 30/60 mg/kg). Following a 3-month treatment period, some rats were sacrificed while others went through an additional 1-month abstinence period before they were sacrificed. In vitro autoradiography (ARG) was carried out using [3H] MK801 to examine NMDA receptor binding in the brain.

KEY FINDINGS

The dose-dependent effects of MP following 13 weeks of treatment on [3H] MK-801 binding were seen across the brain in the following regions: prelimbic, insular, secondary motor, primary motor, retrosplenial, rhinal, piriform, auditory, visual, dorsolateral striatum, nucleus accumbens core, hippocampus, amygdala, and thalamic regions. No differences were observed in [3H] MK-801 binding levels in animals that underwent the same treatment followed by a 4 week abstinence.

SIGNIFICANCE

These results demonstrate that chronic MP treatment altered NMDA receptor expression throughout the brain, which in turn may impact an individual's drug-seeking behavior, fear memory formation and overall activity. However, these effects of chronic MP were eliminated following cessation of treatment.

Guidelines for analysis of low-frequency antigen-specific T cell results: Dye-based proliferation assay vs 3H-thymidine incorporation

It is generally recognized that dysregulation of the immune system plays a critical role in many diseases, including autoimmune diseases and cancer. T cells play a crucial role in maintaining self-tolerance, while loss of immune tolerance and T cell activation can lead to severe inflammation and tissue damage. T cell responses have a key role in the effectiveness of vaccination strategies and immunomodulating therapies. Immunomonitoring methods have the ability to elucidate immunological processes, monitor the development of disease and assess therapeutic effects. In this respect, it is of particular interest to evaluate antigen (Ag)-specific T cells by determining their frequency, type and functionality in cellular assays. Nevertheless, Ag-specific T cells are detected infrequently in most diseases using current techniques. Many efforts have been made to develop more sensitive, reproducible, and reliable methods for Ag-specific T cell detection. It has been found that analysis of cellular proliferation can be a useful tool to determine the presence and frequency of Ag-specific T cell and to provides insight into modulation of the T cell response by a specific antigen or therapy. However, the selection of a cut-off value for a positive response and therefore a more accurate interpretation of the data, continues to be a major concern. Here, we provide guidelines to select a proper cut-off for monitoring of Ag-specific CD4⁺ T cell responses. In vitro Ag-stimulation has been assessed with two methods; a dye-based proliferation assay and ³H-thymidine-based assay. Two cut-off approaches are compared; mean and variance of control wells, and the stimulation index. By evaluating the proliferative response to the in vitro Ag-stimulation using these two methods, we demonstrate the importance of taking into consideration the variability of the control wells to distinguish a positive from a false positive response.

Tritium Atom Exchange May Be Responsible for Activity Decrease in Plastic Liquid Scintillation Vials

Detection and measurement of low-energy beta particles is commonly achieved by liquid scintillation counting, in particular for low-level tritium samples. When samples are contained in plastic scintillation vials for long-term storage, the tritium activity in the vials has been found to decrease faster than expected from its natural radioactive decay. Different explanations for this observation have attributed some of these tritium activity losses to diffusion of the sample, degradation of the LSC cocktail, and the potential long-term changes in quenching effects of the LSC cocktail. An alternative explanation may also be that the tritium organically binds to the carbon chains in the plastic bottle through direct H and H atom exchange. A study was designed and performed to test this latter hypothesis of H and H atom exchange in plastic. Deionized water was introduced in a plastic vial that previously contained tritiated water to assess any increase in tritium activity from the reverse atom exchange between the vial material and the deionized water. A greater loss in activity concentration is observed in plastic vials compared to glass vials as a function of storage time for the tritiated water. Furthermore, the tritium activity concentration in the deionized water increased when storage occurred in plastic vials, an effect that is not observed for storage in glass vials. The study results indicate that hydrogen atom exchange may possibly take place in plastic vials.

Using a coupled dispersion model to estimate depletion of a tritium oxide plume by a forest

Tritium processing facilities may release tritium oxide (HTO) to the atmosphere which poses potential health risks to exposed co-located workers and to offsite individuals. Most radiological consequence analyses determine HTO dose by applying Gaussian plume models to simulate the transport of HTO. Within these models, deposition velocity is used to assess the sum of all deposition processes acting on the plume. While this may account for vegetative and soil uptake or respiration processes, it may currently lack inclusion of the complex interactions within heterogeneous forested environments. In this complex morphology, dispersion patterns are significantly altered by changing flow regimes above and below the forest canopy and by the transfer of plume material across the canopy boundary. To determine the effects of a heterogeneous forest canopy on an airborne HTO plume, a Gaussian plume model coupled with an advection-diffusion plume model was applied to estimate transport in the free atmosphere above the forest and within the forest canopy and understory. During 2012, wind speed and wind direction measurements taken at 5 heights, ranging from 2-m to 28-m, on an instrumented meteorological tower located in a loblolly pine forest at the Department of Energy (DOE) Savannah River Site (SRS), near Aiken, SC. From these measurements, model predictions were made over a full spectrum of meteorological conditions. Deposition and resuspension velocities were calculated based on the model-predicted flux of plume material across the top of the forest canopy. Additionally, net deposition velocity of the plume material was calculated as the difference between the deposition and resuspension velocities. The 1st and 5th percentile net deposition velocities were estimated to be 0.7 cm s^-1 and 1.2 cm s^-1, respectively.

Search for tritium in air in a room equipped with 14 MeV neutron generator with tritiated targets

Eight documented tritiated targets were stored, as well as some very old targets with unknown activity, in a room equipped with an ING-114 14 MeV fast neutron generator. When the neutron generator was running, the tritiated targets were irradiated with a deuterium beam. The aim of this work is to determine the tritium content in the room's atmosphere, as well as the radiation exposure of workers in the room. In this study, isotopic exchange was assumed. This means that tritium from the targets diffused into the air, where it reacted immediately with oxygen particles to form vapour. These vapour molecules diffused into open vessels containing deionized water (50 ml in 120 ml plastic containers). Fifty vessels were arranged along the length (every 0.50 m) and width (every 1 m) of the room. Additionally, there were three vessels placed in the room for shorter periods (5, 7, and 12 days) together with a vessel that was exposed to the tritium for the full duration of the experiment (18 days) to determine the saturation curve. Based on the measured tritium contents, a map of the spatial distribution of tritium in the room was created. The results were used to calculate the radiation dose for a person working in the room and showed no significant contribution to the approved average annual dose for workers.