Concentration Of Tritiated Water Research Articles

Laminated Flow-Cell Detector with Granulated Scintillator for the Detection of Tritiated Water

Nuclear sites require regular measurements of the air, soil, and groundwater to ensure the safety of the surrounding environment from potentially hazardous levels of contamination. Although high-energy beta and gamma emitters can often be detected instantly using fixed dosimeters, the detection of low-energy beta emitters is a difficult challenge, especially in groundwater, as its radiation is easily self-absorbed by the surrounding medium. Therefore, it is common practice to sample groundwater and transfer it to a laboratory for analysis using Liquid Scintillation Counting. This work demonstrates a new detector design for the real-time monitoring of tritiated water, a weak beta emitter. This design utilizes a flow cell filled with a granulated scintillator to maximize the surface area of the sample. The cavity is made from plastic sheets, which allow rapid manufacture using readily available lamination sheets. A column of SiPMs in coincidence counting mode has been implemented to reduce noise and allow future extensions to the flow cell for greater detection rates while allowing the detector to fit within limited spaces such as groundwater monitoring boreholes. Using multiple concentrations of tritiated water, this detector has been validated and calibrated, obtaining a minimum detection activity of 26.356 ± 0.889 Bq/mL for a 1-day counting period.

Efficient processing of tritiated water by using a two-stage Pd membrane reactor with Pt/TiO2 catalyst

Large amounts of tritiated water (HTO) will be produced during the operation of nuclear power plants and fusion devices, which is harmful to the environment and human due to its radioactivity and toxicity. So, the tritium concentration of tritiated water must be reduced to a very low value before discharge. Hydrogen-water isotope exchange reaction (H2 + HTO→H2O + HT) based on palladium membrane reactor has been proposed to process tritiated water. However, a comprehensive study about the influence of operation parameters on the membrane reactor performance is insufficient, which is not conducive to the design of reactor in practical application. Moreover, the commonly used Pt/Al2O3 or Ni/SiO2 catalysts are not active for tritiated water dissociation, so the catalytic activity of these catalysts is not high. In order to process tritiated water more effectively, a two-stage membrane reactor has been designed and established in this work, and Pt/TiO2 catalyst with rich oxygen vacancies is used to catalyze the hydrogen-water isotope exchange reaction for the first time. The membrane reactor performance shows an approximate linear relationship with a new combined parameter S0.5P1.5R/F2 (S is membrane area, F is water flow rate, P is vapor partial pressure, R is swamping ratio), which can be used predict the membrane performance. The isotope exchange reaction activity of Pt/TiO2 is better than that of Pt/Al2O3 due to its good ability for water dissociation and the hydrogen spillover effect. At last, a tritiated water processing experiment by using two-stage membrane reactor with Pt/TiO2 catalyst with rich oxygen vacancies has been carried out. The tritium decontamination factor reaches 40588, which is the highest experimental value so far. The results indicate that the two-stage Pd membrane reactor based on hydrogen-water isotope exchange reaction is an efficient technology for tritiated water processing.

Tritiated water removal method based on hydrate formation using heavy water as co-precipitant

A separation method of tritium has been developed based on co-precipitation of tritiated water on porous heavy water (D2O) based clathrate hydrate. The tritium was semi-continuously removed by a circulating flow of tritium-containing light water through the D2O hydrate media crystallized in advance. The tritium concentration of 4.77 × 105 Bq/kg was reduced to 1.55 × 103 Bq/kg with HFC-134a hydrate at 0.35 MPa for 1 h, while tritiated water treatment at a concentration of 1010 Bq/kg or greater is eligible with the conventional detritiation methods. Near the D2O hydrate surfaces, solid solutions with higher concentrations of tritiated water were deposited on the hydrate substrate than those in the liquid phase. The semi-serialized operation of hydrate based detritiation is capable of high-rate processing as well as energy and resource saving. This method could be a candidate treatment for huge quantities of water with low concentration tritium discharged from nuclear fusion power generation system.

Characterization of atmospheric tritiated water concentration in the vicinity of the fukushima daiichi nuclear power plant

Characterization of atmospheric tritiated water concentration in the vicinity of the fukushima daiichi nuclear power plant

Induction of somatic mutations by low concentrations of tritiated water (HTO): evidence for the possible existence of a dose-rate threshold.

Tritium is a low energy beta emitter and is discharged into the aquatic environment primarily in the form of tritiated water (HTO) from nuclear power plants or from nuclear fuel reprocessing plants. Although the biological effects of HTO exposures at significant doses or dose rates have been extensively studied, there are few reports concerning the biological effects of HTO exposures at very low dose rates. In the present study using a hyper-sensitive assay system, we investigated the dose rate effect of HTO on the induction of mutations. Confluent cell populations were exposed to HTO for a total dose of 0.2 Gy at dose rates between 4.9 mGy/day and 192 mGy/day by incubating cells in medium containing HTO. HTO-induced mutant frequencies and mutation spectra were then investigated. A significant inflection point for both the mutant frequency and mutation spectra was found between 11 mGy/day and 21.6 mGy/day. Mutation spectra analysis revealed that a mechanistic change in the nature of the mutation events occurred around 11 mGy/day. The present observations and published experimental results from oral administrations of HTO to mice suggest that a threshold dose-rate for HTO exposures might exist between 11 mGy/day and 21.6 mGy/day where the nature of the mutation events induced by HTO becomes similar to those seen in spontaneous events.

An In-Vitro Analysis of Peri-Implant Mucosal Seal Following Photofunctionalization of Zirconia Abutment Materials

The presence of epithelial and connective tissue attachment at the peri-implant–soft tissue region has been demonstrated to provide a biological barrier of the alveolar bone from the oral environment. This barrier can be improved via surface modification of implant abutment materials. The effect of photofunctionalization on creating a bioactive surface for the enhancement of the epithelial and connective tissue attachment of zirconia implant abutment’s peri-implant mucosal interface using organotypic model has not been investigated. Therefore, this study aimed to evaluate the soft tissue seal around peri-implant mucosa and to understand the effect of photofunctionalization on the abutment materials. Three types of abutment materials were used in this study; yttria-stabilized zirconia (YSZ), alumina-toughened zirconia, and grade 2 commercially pure titanium (CPTi) which were divided into nontreated (N-Tx) and photofunctionalized group (UV-Tx). The three-dimensional peri-implant mucosal model was constructed using primary human gingival keratinocytes and fibroblasts co-cultured on the acellular dermal membrane. The biological seal was determined through the concentration of tritiated water permeating the material–soft tissue interface. The biological seal formed by the soft tissue in the N-Tx group was significantly reduced compared to the UV-treated group (p < 0.001), with YSZ exhibiting the lowest permeability among all materials. Photofunctionalization of implant abutment materials improved the biological seal of the surrounding soft tissue peri-implant interface.

Spatial and temporal variation of tritium concentrations during a dam flushing operation

Tritium is a radionuclide commonly observed worldwide in riverine systems. In the Rhône River downstream the Lake Geneva (Switzerland and France), its occurrence is also related to its use for its luminescent properties in watchmaking paints. In fact, tritium is regularly observed at anomalous levels in this river and extreme events such as flushing operations might conduct to its transport downstream. In the Rhône River, characterized by 21 dams downstream the Geneva Lake, such operations are regularly organized to remove the sediments and limit problematic consequences such as siltation and increased flooding hazards. The consequences of dam flushing operations on tritium concentrations were thus investigated. Samples of Suspended Particulate Matter (SPM) and water were collected in the Rhone River downstream of Geneva in June 2012, during a planned flushing operation of three upstream reservoirs (Verbois, Chancy-Pougny and Génissiat). The concentrations of tritiated water (HTO) and organically bound Tritium (OBT) were measured and compared to reference concentrations. The flushing operations had no impact on the HTO concentration while the increases observed were related to the authorized releases of HTO from a nuclear power plant located downstream the dams. High increases of OBT concentrations in SPM were observed at two stations (Creys-Malville and Jons) without clear spatial or temporal trends. These anomalous peaks could be explained by the heterogeneous spatial distribution of technogenic tritium leading to large variations of tritium concentrations within the samples even though collected in areas close to each other. The results highlight the need to investigate the amount of such technogenic tritium currently stored in the upstream Rhone River as it might be significant.

Preliminary research on method of tree ring’s NE-OBT measurement using AMS

The non-exchangeable organically bound tritium (NE-OBT) concentration in the cellulose of tree rings can accurately reflects the tritiated water concentration in the local environment and often contains the only historical record of tritium exposure. However, there is few study about NE-OBT measurement using AMS around the world, especially in China. Furthermore, in order to measure tritium in tree rings exactly, it is necessary to solve several key problems during sample preparation. In this study, the optimized sample preparations procedure are investigated. The purity of cellulose extracted by improved sodium hypochlorite pretreatment method is about 83.9%, considerably higher than the 64.8% conventional methods. Pure TiH2 samples reaching requirements of AMS measurement have been made. The isotope fractionation is stabilized during sample preparation. Preliminary results of sample analysis using a compact AMS with 200 kV accelerator are presented. Currently, the minimum T/H ratio that can be accurately measured is only about 10−12, limited by hydrogen contents in samples and instrument conditions. Further works will be done in order to achieve lower detection limits and better accuracy.

Occurrence of HTO and NE-OBT in soil in the vicinity of the Qinshan Nuclear Power Plant

In this study, concentrations of tritiated water (HTO) and non-exchangeable organically bound tritium (NE-OBT) and the NE-OBT/HTO ratios were determined in soil around Qinshan Nuclear Power Plant (NPP), Zhejiang, China, and their vertical profile and spatial distribution were investigated. Results showed variations in both the HTO and NE-OBT concentrations in the vertical profile. The HTO concentrations generally decreased firstly and then increased with the increasing depths, but the trend was not significant. The NE-OBT concentrations in the surface soils (0–5 cm) were considerably lower than those in the deep soils (5–25 cm) at all the sites. The NE-OBT/HTO ratios also show a variable vertical profile, initially increasing and then decreasing with increasing soil depth. Both the HTO and NE-OBT concentrations decreased with the increasing distance to the HWRs in deep soil layers (5–25 cm), revealing that the released tritium from the NPP affected the spatial distribution.

Recent activities on water detritiation technology in JAEA

Japan Atomic Energy Agency has developed the water detritiation technology for CECE process considering the escalation in quantity and tritium concentration of tritiated water to be processed toward realization of the Japanese fusion DEMO plant. A commercial ion exchange perfluoro-membrane for concentrated tritiated water electrolyzer is durable against irradiation up to 1500kGy in view of mechanical strength and ion exchange capacity. Concerning hydrophobic catalyst for LPCE column, a new method of manufacturing catalysts involving hydrophobic processing with an inorganic substance base has been developed. The catalyst created with this method has achieved the highest exchange efficiency, equivalent to 1.3 times the previously most powerful efficiency.

Determination of Tritiated Water Activity Using EPR Spectrometry

In this paper, the possibility for determination of the tritiated water activity using Electron Paramagnetic Resonance (EPR) spectrometry was analyzed. The method relies on estimation of hydroxyl radicals resulted from self-radiolytical processes using EPR spectrometers. The mechanisms of inducing of free radical by self radiolysis of tritiated water, the accumulation time of hydroxyl radicals and the corroboration of signals amplitude with the tritiated water concentration have been studied.

HTO Contamination on Polymeric Materials

We have tested typical polymeric materials related to the water detritiation system to evaluate their contamination by tritiated moisture and water. The polymeric samples were exposed to 740-1110 Bq/cm3-gas of tritiated moisture with a 1kPa of H2O pressure at a temperature ranged 288 to 298K for various times up to 70 weeks. The other polymeric samples were immersed directly in 70000 Bq/cm3-liquid of tritiated water at a temperature ranged 288 to 298K for various times up to 52 weeks. After the test samples were exposed, the concentrations of tritiated water absorbed in the sample were evaluated by static leaching method. The exposure time to HTO moisture affected negligibly the concentrations of HTO absorbed in the samples. The immersion time in liquid HTO in contrast affected strongly the concentrations of HTO absorbed in the samples, due to penetration of HTO. Appropriate polymeric materials were clarified in the light of HTO contamination.

Sensitivity of a specially designed calorimeter for absolute evaluation of tritium concentration in water

Applicability of a specially designed high-sensitivity conduction calorimeter has been examined to determine the absolute amount of tritium in tritiated water. A given concentration of tritiated water was prepared for examinations. Prior to measurements by the calorimeter, the concentration of tritium was measured by a liquid scintillation counter, and it was determined as 46.0 ± 0.5 MBq/cm 3. This tritiated water, 20 cm 3, was loaded into a sample cell of the calorimeter. The concentration of tritium determined by the calorimeter was 45.2 ± 2.0 MBq/cm 3, and it agreed with that by the liquid scintillation counter within a few percent. In addition, detection limit of the present calorimeter was evaluated to be 40 MBq, considering the standard deviation of background level measured without tritiated water. It was concluded, therefore, that the present calorimeter can be utilized as a standard device for determination of the absolute amount of tritium in tritiated water.

Cerebrospinal fluid absorption disorder of arachnoid villi in a canine model of hydrocephalus

Hydrocephalus results from inadequate passage of cerebrospinal fluid (CSF) from its point of production within the cerebral ventricles to its point of absorption into systemic circulation. The objective of this study was to investigate the disorders of CSF absorption by arachnoid villi during the different phases of hydrocephalus. Silicone oil was injected into the fourth ventricle of 15 canines as an experimental group. Saline solution (0.9% NaCl) was injected in another nine canines as a control group. In order to block CSF transport through the cribriform plate, an external ethmoidectomy was performed in five dogs from experimental group and three dogs from control group at three days (acute stage), two weeks (sub-acute stage), and 12 weeks (chronic stage) respectively. Tritiated water was injected into the canines' cortical subarachnoid space and blood levels were measured at intervals of 1 h, 4 h, 8 h, 16 h and 48 h respectively. Time-concentration curve of tritiated water was drafted. The area under the curve (AUC) was calculated for variance analysis and t-testing. In the chronic group, the tritiated water concentration rose slowly to a peak at 16 h. It was significantly lower than other groups at 1h, 4h, 8h and 16 h, but was higher than other groups at 48 h. Analysis of the AUC showed significant differences among all the groups (P<0.01). There were no significant differences in the AUC between control groups, the acute group, and the sub-acute group (P>0.05); however, the AUC of the chronic group was significantly lower than other groups (P<0.05). The CSF absorption ability of arachnoid villi is significantly damaged in a long-term state of hydrocephalus.

Tritium in the urine in Finnish people

Tritium in urine was analysed from 227 randomly selected Finnish adults. The people were 18 to 65 of age. Urine samples were collected over night. The mean activity concentration of tritiated water in urine was 2.5 Bq l(-1) and the maximum activity concentration 18.3 Bq l(-1). The minimum detectable activity varied from 1.5 to 2.3 Bq l(-1). Because organically bound tritium is approximately 10% of the total tritium, its concentration was below the detection limit and could be ignored. The mean effective dose for Finnish people from tritium was 2.4 x 10(-3) microSv y(-1).

高温熱処理したシリカゲルおよび多孔質ガラスを吸着剤に用いたトリチウム水の濃縮

1100℃までの温度範囲で熱処理を行ったシリカゲル及び多孔質ガラスを吸着剤に用いて, トリチウム水の吸着濃縮を行った。トリチウム水は通常の水に比べ強く吸着していることがわかった。トリチウム分配係数は, 多孔質ガラスでは熱処理温度の上昇と共に低下する傾向が見られたのに対し, シリカゲルでは逆に, 900℃以上で急激に上昇し, 1100℃熱処理では1.38と高い値を示した。熱処理後のシリカゲルには孤立型シラノール基が形成されていることがわかった。孤立型シラノール基に吸着したヒドロキシル基あるいは水分子は互いに水素結合することが困難であるため, トリチウムの質量効果が大きく現れたものと推察された。

03/02604 Potential and cost-effectiveness of CO 2 reductions through energy measures in Swedish pulp and paper mills : Möllersten, K. et al. Energy, 2003, 28, (7), 691–710

At the Tritium Process Laboratory (TPL) in Japan Atomic Energy Research Institute (JAERI), Caisson assembly for tritium safety study (CATS) with 12 m3 of large airtight vessel (Caisson) was fabricated for confirmation and enhancement of fusion reactor safety to estimate the tritium behavior in the case, where the tritium leak accident should happen. One of the principal objectives of the present studies is the establishment of simulation method to predict the tritium behavior after the tritium leak accident should happen in a ventilated room. As for the understanding of initial tritium behavior until the tritium concentration become steady, the precise estimation of local flow rate in a room and time-dependent release behavior from the leak point are essential to predict the tritium behavior by simulation code. The three-dimensional eddy flow model considering, tritium-related phenomena was adopted to estimate the local flow rate in the 50 m3/h ventilated Caisson. The time-dependent tritium release behavior from the sample container was calculated by residence time distribution function. The calculated tritium concentrations were in good agreement with the experimental observations. The primary removal tritium behavior was also investigated by another code. Tritium gas concentrations decreased logarithmically to the time by ventilation. These observations were understandable by the reason that the flow in the ventilated Caisson was regarded as the perfectly mixing flow. The concentrations of tritiated water measured, and indications of tritium concentration by tritium monitors became gradually flat. This phenomena called ‘tritium soaking effect’ was found to be reasonably explained by considering the contribution of the exhaustion velocity by ventilation system, and the adsorption and desorption reaction rate of tritiated water on the wall material which is SUS 304. The calculated tritium concentrations were in good agreement with the experimental observations. The effectiveness of these codes was thus proved.

Impact of tritium discharged from a research reactor on concentrations in environmental water samples

The distribution of environmental tritium concentrations in several samples taken near the Kyoto University Research Reactor (KURR) was studied. The KURR Institute (KURRI) supports three major sources of tritium: a D 20 (heavy water) facility and a Cold Neutron Source (CNS) facility in the KURR containment, and a tritium target fabricated in an accelerator in the critical assembly building. This report focuses on estimating the rate of release of tritium from these sources into the environment, and grasping the relation between the rate and the concentrations in samples of water such as precipitation , air moisture and surface water taken near the release point. The concentrations of tritiated water (HTO) in the stack exhaust condensate were in the range 0.8-3 kBq dm3 though those in air in the buildings that support the HTO sources ranged from 5 Bq dm3 to 2 kBq dm3. The HTO concentrations in the air decreased by ca. 1/500 within 300m of the KURR stack, which is five times the current global level about 5 km off-site. Assessing the degree of attenuation of HTO concentrations in the field is informative for estimating the chronic impact of contaminants in the environment.

A metabolic derivation of tritium transfer coefficients in animal products

Tritium is a potentially important environmental contaminant originating from the nuclear industry, and its behaviour in the environment is controlled by that of hydrogen. Animal food products represent a potentially important source of tritium in the human diet and a number of transfer coefficient values for tritium transfer to a limited number of animal products are available. In this paper we present an approach for the derivation of tritium transfer coefficients which is based on the metabolism of hydrogen in animals. The derived transfer coefficients separately account for transfer to and from free (i.e. water) and organically bound tritium. A novel aspect of the approach is that tritium transfer can be predicted for any animal product for which the required metabolic input parameters are available. The predicted transfer coefficients are compared to available independent data. Agreement is good (R2=0.97) with the exception of the transfer coefficient for transfer from tritiated water to organically bound tritium in ruminants. This may be attributable to the particular characteristics of ruminant digestion. We show that tritium transfer coefficients will vary in response to the metabolic status of an animal (e.g. stage of lactation, diet digestibility etc.) and that the use of a single transfer coefficient from diet to animal product is inappropriate. It is possible to derive concentration ratio values from the estimated transfer coefficients which relate the concentration of tritiated water and organically bound tritium in an animal product to their respective concentrations in the animals diet. These concentration ratios are shown to be less subject to metabolic variation and may be more useful radioecological parameters than transfer coefficients. For tritiated water the concentration ratio shows little variation between animal products ranging from 0.59 to 0.82. In the case of organically bound tritium the concentration ratios vary between animal products from 0.15 (goat milk) to 0.67 (eggs).

Simulation study of intentional tritium release experiments in the caisson assembly for tritium safety at the TPL/JAERI

At the Tritium Process Laboratory (TPL) in Japan Atomic Energy Research Institute (JAERI), Caisson assembly for tritium safety study (CATS) with 12 m 3 of large airtight vessel (Caisson) was fabricated for confirmation and enhancement of fusion reactor safety to estimate the tritium behavior in the case, where the tritium leak accident should happen. One of the principal objectives of the present studies is the establishment of simulation method to predict the tritium behavior after the tritium leak accident should happen in a ventilated room. As for the understanding of initial tritium behavior until the tritium concentration become steady, the precise estimation of local flow rate in a room and time-dependent release behavior from the leak point are essential to predict the tritium behavior by simulation code. The three-dimensional eddy flow model considering, tritium-related phenomena was adopted to estimate the local flow rate in the 50 m 3/h ventilated Caisson. The time-dependent tritium release behavior from the sample container was calculated by residence time distribution function. The calculated tritium concentrations were in good agreement with the experimental observations. The primary removal tritium behavior was also investigated by another code. Tritium gas concentrations decreased logarithmically to the time by ventilation. These observations were understandable by the reason that the flow in the ventilated Caisson was regarded as the perfectly mixing flow. The concentrations of tritiated water measured, and indications of tritium concentration by tritium monitors became gradually flat. This phenomena called ‘tritium soaking effect’ was found to be reasonably explained by considering the contribution of the exhaustion velocity by ventilation system, and the adsorption and desorption reaction rate of tritiated water on the wall material which is SUS 304. The calculated tritium concentrations were in good agreement with the experimental observations. The effectiveness of these codes was thus proved.