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The complex behavior of tritium and the probability of increasing tritium concentrations released in the environment were the promotors for the research and development of laboratory methods that enable to accurately determine the various forms of tritium including organically-bound tritium (OBT) for public and regulatory assurance. The measurement of tritium is a key step for dose and risk assessment. The Cernavoda Nuclear Power Plant (NPP) in Romania improved preparation methods and tested environmental matrices for OBT analysis through intercomparison exercises. This paper describes the international Organically-Bound Tritium (OBT) intercomparison exercise, organized by the Cernavoda Nuclear Power Plant (NPP) in 2019-2020, using fruit sample (quince) from Cernavoda town. Evaluation of the results from the participating laboratories was performed using both robust analysis (Algorithm A) method described in the ISO 13528:2015 standard and ANOVA method. The results obtained are encouraging as an increased number of participating laboratories did not change the observed dispersion of the results for activity concentration level around 50 Bq/L of combustion water. The stability of the remaining sample will be checked in time to investigate its use as a reference material for OBT analysis at the environmental levels.

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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.

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Measurements of tritium in its various forms within the environment and especially in organic matter are keys to improving the current understanding of its environmental behavior and distribution. Validated or standardized analytical procedures for tritium determination methods have now been developed for several forms of tritium in environmental samples, yet an analytical lack remains regarding the quantifications of exchangeable and non-exchangeable forms of organically bound tritium (OBT) fractions. The present work therefore aims to provide a means of developing a standardized method for OBT fraction determination by evaluating the robustness and relevance of two methods (intrusive and non-intrusive methods) developed for non-exchangeable OBT quantification on a broad panel of pertinent environmental matrices. The validity and reliability of a non-intrusive method has thus been confirmed through a robust comparative study. Moreover, its relevance for standardization purposes is discussed, while the fundamental weakness of the conventional and most widespread method is highlighted and directly quantified for the first time in relying on many demonstrated biases.

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Over the past several years, it has become increasingly acknowledged that Organically Bound Tritium (OBT) is the most pertinent tritium form for understanding its behavior and distribution within the biosphere. The fate of tritium actually depends on the accessibility and exchangeability of hydrogen atoms for isotopic exchanges in natural organic matter, especially in widespread biomass biomolecules like carbohydrates or proteins. The present work is therefore aimed at providing a means for improving the knowledge of tritium speciation and distribution on environmental matrices by evaluating the impact of molecular structure of various carbohydrate molecules on OBT behavior. We are thus proposing to assess the exchange capacities of hydrogen from a gas-solid isotopic exchange methodology in wheat grains, water-milfoil and apple environmental matrices using starch, cellulose/proteins and simple carbohydrates as their respective main constituents. For wheat grains, a good agreement was obtained between experimental and theoretical values as a result of the predominantly simple molecular structure of starch. For both water-milfoil and apple, the disparities between experimental and theoretical values showed the occurrence of the buried form of tritium, correlated with the 3D molecular complexity of their main constituents. The key role played by these determinant constituents on hydrogen exchange capacity could thus be experimentally demonstrated on several environmental matrices. These distinct hydrogen exchange capacities were then proven to exert an influence on the NE-OBT distribution on environmental matrix constituents, in yielding critical information to better the understanding of tritium distribution and behavior in the environment.

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An original methodology to quantitatively explore exchangeability of hydrogen isotopes in carbohydrate molecules is proposed. To access the speciation of organically bound hydrogen isotopes, isotopic exchanges were carried out under a soft path regime in the vapor phase at 20 °C with set (D,T/H) vapor pressure ratios. When steady states were reached, the fraction of exchangeable hydrogen of microcrystalline cellulose, alpha-cellulose and wheat grains were obtained and ranged from 13 to 31% (versus a theoretical value of 30%). In cellulose, and more specifically in microcrystalline cellulose, the molecular hydrogen bonds as well as the different conformations of the network seemed to decrease the hydroxyl groups of glucose units available for isotopic exchange. On the contrary, the assumed enzymatic hydrolysis of the constitutive molecules of wheat starch into low-molecular weight carbohydrate molecules enhanced the exchangeable pool. An average value of the activity between non-exchangeable organically bound tritium (NE-OBT) and non-exchangeable organically bound hydrogen was calculated for wheat grains, (TH)NE  = 0.55 ±â€¯0.03 Bq.g-1 of hydrogen atoms.

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Organically bound tritium (OBT) has become of increasing interest within the last decade, with a focus on its behaviour and also its analysis, which are both important to assess tritium distribution in the environment and dose consequences. After the first OBT International Workshop which was held in France in May 2012, an international working group was created. The expected benefits are the following: remove or reduce uncertainty in OBT analysis results, provide better OBT model validation data and better public dose results, increase the number of potential measuring OBT laboratories, validate all of the stages of the procedures based on a larger population and more statistically significant results, and investigate the feasibility of CRM's and RM's production. In this framework, three OBT exercises were organised; the 1st one on potatoes was conducted in 2013 by the Canadian National Laboratories (former AECL) with about 20 participating labs from around the world, the 2nd one on a sediment was organised in 2014 by GAU Radioanalytical (University of Southampton) on a sediment with again about 20 participating labs and the third one on wheat was organised in 2015 by the Commissariat à l'énergie atomique (CEA) with about 25 participating labs.

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Tritium emissions are one of the main concerns with regard to CANDU reactors and Canadian nuclear facilities. After the Fukushima accident, the Canadian Nuclear Regulatory Commission suggested that models used in risk assessment of Canadian nuclear facilities be firmly based on measured data. Procedures for measurement of tritium as HTO (tritiated water) are well established, but there are no standard methods and certified reference materials for measurement of organically bound tritium (OBT) in environmental samples. This paper describes and discusses an inter-laboratory comparison study in which OBT in three different dried environmental samples (fish, Swiss chard and potato) was measured to evaluate OBT analysis methods currently used by CANDU Owners Group (COG) members. The variations in the measured OBT activity concentrations between all laboratories were less than approximately 20%, with a total uncertainty between 11 and 17%. Based on the results using the dried samples, the current OBT analysis methods for combustion, distillation and counting are generally acceptable. However, a complete consensus OBT analysis methodology with respect to freeze-drying, rinsing, combustion, distillation and counting is required. Also, an exercise using low-level tritium samples (less than 100 Bq/L or 20 Bq/kg-fresh) would be useful in the near future to more fully evaluate the current OBT analysis methods.

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It has become increasingly recognized that organically bound tritium (OBT) is the more significant tritium fraction with respect to understanding tritium behaviour in the environment. There are many different terms associated with OBT; such as total OBT, exchangeable OBT, non-exchangeable OBT, soluble OBT, insoluble OBT, tritiated organics, and buried tritium, etc. A simple classification is required to clarify understanding within the tritium research community. Unlike for tritiated water (HTO), the environmental quantification and behaviour of OBT are not well known. Tritiated water cannot bio-accumulate in the environment. However, it is not clear whether or not this is the case for OBT. Even though OBT can be detected in terrestrial biological materials, aquatic biological materials and soil samples, its behaviour is still in question. In order to evaluate the radiation dose from OBT accurately, further study will be required to understand OBT measurements and determine OBT fate in the environment. The relationship between OBT speciation and the OBT/HTO ratio in environmental samples will be useful in this regard, providing information on the previous tritium exposure conditions in the environment and the current tritium dynamics.

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In the past decades limited amounts of tritium were handled on the CEA site of Bruyères le Châtel with authorised atmospheric releases. A small fraction of the tritium released entered into environmental samples under three forms: (i) as part of free water (TFWT - Tissue Free Water Tritium), or associated with organic matter in two ways; either (ii) bound to the oxygen and nitrogen atoms of the material as exchangeable organically bound tritium (E-OBT), or (iii) bound to carbon atoms as non exchangeable organically bound tritium (NE-OBT). The first two components provide only a picture of atmospheric tritium concentrations at the sampling time as they are in equilibrium with atmospheric moisture and soil humidity. Unlike these exchangeable forms, however, NE-OBT is tightly bound to the organic matter and provides an integrated record of atmospheric tritium during the growing phase of the vegetation. We mapped NE-OBT in tree leaf samples in an area of about 25×30km(2) around the centre of the CEA site and compared the results with those obtained during a previous sampling exercise in 1989. At this time, the activity levels were almost ten times higher than those observed presently in a similar area almost 20 years later which is consistent with the decrease of atmospheric releases issued from the centre. As the activity levels are now close to environmental background specific attention was also paid to the analytical procedure to ensure reliable low level NE-OBT detection.

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The design, setup and performance of a mass spectrometric system for the analysis of low to very low-level tritium in environmental samples are described. The tritium concentration is measured indirectly by the (3)He ingrowth from radioactive decay after complete initial degassing of the sample. The analytical system is fully computer-controlled and consists in a commercial helium isotope mass spectrometer coupled with a high vacuum inlet system. A detection limit of 0.15 Bq/kg is routinely obtainable for sample sizes of 20g of water equivalent and an accumulation time of three months. Larger samples (and/or longer accumulation time) can be used to obtain lower detection limits. In addition to the benefit of a lower detection limit, another advantage of this non-destructive method lies in the simplicity of the analytical procedure which strongly limits the risk of contamination. An inter-comparison was successfully performed with the conventional beta counting technique on lyophilized grass samples, in a range of tritium concentrations of environmental interest. It shows that the (3)He mass spectrometry method yields results that are fully consistent with the conventional liquid scintillation technique over a wide range of tritium concentrations.

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The authors discuss some of the difficulties encountered when analyzing organically bound tritium (OBT) and describe a sensitive method for low-level OBT determination in biological samples. The methodology, which combines suitable sample treatment, a combustion apparatus for large-sized samples and low-background liquid scintillation counting, provides exclusively carbon-bound tritium measurement. Two key points of this methodology are described and illustrated. The first one is the stage of removal of the exchangeable organic tritium. The efficiency of this stage, carried out by mixing powdered dry samples with tritium-free water, is evaluated. The second key point is the set of precautions taken at any stage of the treatment to avoid contamination of the samples by ambient atmospheric moisture. The detection limit of the method is about 0.5 Bq kg(-1) of dry material. Low-level applications of this methodology are given with estimation of the OBT/HTO ratios.

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The applicability of inductively coupled plasma-mass spectrometry (ICP-MS) for determining actinides in urine was investigated. Performances of ICP-MS including detection limit and analysis time were studied and compared with alpha spectrometry performances. In the field of individual monitoring of workers, the comparison chart obtained in this study can be used as a guide for medical laboratories to select the most adequate procedure to be carried out depending on the case in question (the radioisotope to be measured, the required sensitivity, and the desired response time).

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In the present work, a double-focusing sector field inductively coupled plasma-mass spectrometer was optimised for ultra trace and isotopic analyses of actinide long-lived isotopes in low concentration solutions of the fgml(-1) to the ngml(-1) range. Sensitivities of about 3GHz/(microgml(-1)), with as low a background as 0.1cps, were obtained for U using a conventional concentric pneumatic nebuliser. Detection limits are below the fg range for 239Pu and 240Pu. With natural U, a precision lower than 0.5% RSD is currently obtained for 235U/238U isotopic ratio at the 200pgml(-1) level.

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A rapid procedure--dilution of urine+ICP-MS measurement--for the determination of uranium in urine was validated. Large ranges of concentration and isotopic composition were studied on urine samples excreted by occupationally exposed workers. The results were consistent with those obtained by fluorimetry and by alpha spectrometry after a purification procedure, two currently used techniques. However, the proposed procedure is limited for determination of the minor isotope 234U. Thus for worker monitoring, the conversion of 234U mass concentration into activity concentration can lead to an erroneous value of the effective dose, in particular for a contamination at very low level with highly enriched uranium. A solution to avoid this hazard is to perform a chemical purification prior to ICP-MS measurement to lower uncertainty and detection limit for 234U.

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The absolute mobility of NpO2+ and its equivalent ionic conductivity were extrapolated at 25 degrees C and at infinite dilution using a set of experimental data obtained at various ionic strengths. The separation was carried out by capillary electrophoresis (CE) at various concentrations of creatinine at a pH of 5. The detection of NpO2+ was performed by inductively coupled plasma mass spectrometry coupled on-line with CE. The following values have been found: mu0NpO2+ (25 degrees C) = (2.94 +/- 0.07) x 10(-4) cm2 V(-1) s(-1) and lambda0NpO2+ (x 10(4), 25 degrees C) = 28.3 +/- 0.7 m2 S mol(-1).

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In this paper, the authors describe a sensitive method for low-level non-exchangeable OBT determination. This methodology combines suitable sample treatment, a combustion apparatus for large-sized samples and low-background liquid scintillation spectrometry, along with precautions that substantially reduce the risks of sample contamination. Great care must be taken in the measurement of non-exchangeable OBT at environmental levels. Many authors have discussed the opportunities for cross-contamination between samples and contamination by exchange with the laboratory atmosphere. The authors also describe an application of the methodology to a large-scale sampling and measurement campaign, aimed at the determination of the environmental non-exchangeable OBT background level in tree leaves and ferns collected on the site and in the vicinity of a research centre located in the south-west of France, not far from Bordeaux. This study constitutes a "zero level" for the non-exchangeable OBT activity, as, to our knowledge, there is no tritium source within or in the surroundings of the sampled area capable of producing non-exchangeable OBT activities above the natural levels. Our analyses showed that non-exchangeable OBT activities in the collected samples were very low, ranging from below the detection limit (ca 0.7 Bq kg(-1) of dry material) to ca 2 Bq kg(-1) of dry material. These values are similar to the natural tritium background measured in water samples. No discrepancies can be shown between fern samples and oak tree leaf samples or between samples collected inside and outside the research site.

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Thorium is naturally occurring in various ores used for industrial purposes and has numerous applications. This paper sets out to investigate urine analysis as a suitable monitoring approach for workers potentially exposed to thorium. Due to its biokinetic behavior and its low solubility, urinary concentrations are generally very low, requiring therefore high sensitivity analytical methods. An analytical procedure has been developed for detecting 232Th concentrations of below 1 mBq L(-1) quickly and easily. Due to the long half-life (1.41 x 10(10) y) of 232Th, the potential of a procedure based on urine sample dilution and ICP-MS (inductively coupled plasma-mass spectrometry) measurement was investigated first. Two dilution factors were chosen: 100, which is more suitable for long-term measurement trials, and 20, which increases sensitivity. It has been shown that a 100-fold dilution can be used to measure concentrations of below 1 mBq L(-1), whereas a 20-fold one can be used to reach concentrations of below 0.06 mBq L(-1). Then, on the basis of the limitation of the procedure based on urine dilution, the suitable field of application for the different procedures (100-fold and 20-fold dilution and also a chemical purification followed by an ICP-MS measurement) was determined in relation to monitoring objectives.

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The determination of actinides concentration level in excreta, mainly urine is currently carried out to monitor people potentially exposed to alpha emitters. To measure actinides in such samples, specific analytical protocols have been set up. The chemical purification uses different chromatographic columns to selectively separate the actinides and each fraction, after electroplating, is measured by alpha spectrometry. To reach 1 mBq l(-1) of U, Pu or Am using these protocols, 6 days equally distributed between the chemical purification and the measurement are necessary. The protocol proposed here is based on a single extractant, the 1,3,5-trimethoxy-2,4,6-tricarboxy-p-tert-butylcalix[6]arene, used to selectively separate U, Pu and Am from the urinary matrix prior to be measured. Using this analytical protocol, U and Pu are quantitatively and selectively recovered in two different acidic backextraction solutions whereas Am is quantitatively and selectively recovered in the organic phase. Furthermore, the purification stage is considerably shortened. The uranium and plutonium amounts are measured in aqueous phases using alpha spectrometry or inductively coupled plasma-mass spectrometry, whereas Am is measured in the organic phase using alpha liquid scintillation (photon/electron-rejecting alpha liquid scintillation).

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The uranium concentration in human urine spiked with natural uranium and rat urine containing metabolized depleted uranium was determined by ICP-MS. The use of ICP-MS was investigated without any chemical treatment or after the different stages of a purification protocol currently carried out for routine monitoring. In the case of spiked urine, the measured uranium concentrations were consistent with those certified by an intercomparison network in radiotoxicological analysis (PROCORAD) and with those obtained by alpha spectrometry in the case of the urine containing metabolized uranium. The quantitative information which could be obtained in the different protocols investigated shows the extent to which ICP-MS provides greater flexibility for setting up appropriate monitoring approaches in radiation protection routines and accidental situations. This is due to the combination of high sensitivity and the accuracy with which traces of uranium in urine can be determined in a shorter time period. Moreover, it has been shown that ICP-MS measurement can be used to quantify the 235U isotope, which is useful for characterizing the nature of the uranium compound, but difficult to perform using alpha spectrometry.

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The gamma-subunit of the high molecular weight form of mouse submaxillary gland nerve growth factor is known to be electrophoretically heterogeneous. The protein is a mixture of molecules containing either two or three chains, attached covalently by disulfide bonds, that arise from one or two endoproteolytic cleavages. Analysis of the amino acid composition and partial sequence of the resultant fragments has defined the location of the two cleavage sites. Further heterogeneity is generated by partial removal of the carboxyl-terminal basic residues located at the internal cleavage sites, presumably by an endogenous exopeptidase(s) with carboxypeptidase B specificity. Permutations of these endo- and exoproteolytic cleavages generate six possible microheterogeneous forms, which can account for the five major bands observed on electrophoresis at pH 7.05 and the three principal forms seen on isoelectric focusing.

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