Tritium Concentrations In Air Research Articles

Dispersion and removal characteristics of tritium originated from nuclear power plants in the atmosphere

The activities of tritium in water-vapor (n = 649) and precipitation (n = 2404) samples were measured from 1998 to 2015 around the Wolsong nuclear power plant (NPP) site where four pressurized heavy water reactors and two pressurized water reactors operated. The activity concentrations of tritium in the water-vapor and precipitation samples were in the ranges of 2.2–2200 Bq/L and 0.3–1090 Bq/L, respectively. The concentrations of tritium in the water-vapor in spring were approximately 7 times higher than those in fall and winter, mainly owing to the wind directions at the power plant location. The annual geometric mean activities of tritium in the water-vapor and precipitation samples varied within 56% and 83% from the average, respectively, depending primarily on the annual discharge amount of tritium to the atmosphere. The activities of tritium in the water-vapor and precipitation samples rapidly decreased away from the power plant. Approximately 0.5–30% of tritium discharged from the NPP site was removed by precipitation to the ground within an area with a radius of 30 km from the NPP site, which linearly depended on the precipitation amount. Our results suggest that the wind direction and precipitation, in addition to the amount of discharge, are important factors that control the tritium concentrations in air near the NPP site.

Tritium Level Evolution in the Environment at Experimental Pilot for Tritium and Deuterium Separation—ICSI

The paper presents the variation of tritium activity concentration in the environment of Experimental Pilot Plant for Tritium and Deuterium Separation (PESTD) over 6 years of observations. The tritium level was established in surface water, air, precipitation, home-grown vegetable, meat and milk. The yearly average tritium concentrations in air were slightly higher than values for the preoperational monitoring program. The values of tritium concentration in surface water and fresh products used for human consumption did not exceed 3 Bq/kg fresh weight. Nuclear activity of PESTD did not have any impact on the environment so far.

Contamination mechanisms of air basin with tritium in venues of underground nuclear explosions at the former Semipalatinsk test site

During the period of testing from 1945 to 1962 at the territory of Semipalatinsk test site (STS) within the Degelen Mountains in tunnels, 209 underground nuclear explosions were produced. Many of the tunnels have seasonal water seepage in the form of streams, through which tritium migrates from the underground nuclear explosion (UNE) venues towards the surface. The issue of tritium contamination occupies a special place in the radioactive contamination of the environment. In this paper we assess the level and distribution of tritium in the atmospheric air of ecosystems with water seepage at tunnels № 176 and № 177, located on “Degelen” site. There has been presented general nature of tritium distribution in the atmosphere relative to surface of a watercourse which has been contaminated with tritium. The basic mechanisms were studied for tritium distribution in the air of studied ecosystems, namely, the distribution of tritium in the systems: water–atmosphere, tunnel air–atmosphere, soil water–atmosphere, vegetation–atmosphere. An analytical calculation of tritium concentration in the atmosphere by the concentration of tritium in water has been performed. There has experimentally obtained the dependence for predictive assessment of tritium concentrations in air as a function of tritium concentration in one of the inlet sources such as water, tunnel air, soil water, vegetation, etc.. The paper also describes the general nature of tritium distribution in the air in the area “Degelen”.

Validation of Real Time Dispersion of Tritium over the Western Mediterranean Basin in Different Assessments

Real time Tritium concentrations in air coming from an ITER-like reactor as source were coupled the European Centre Medium Range Weather Forecast (ECMWF) numerical model with the lagrangian atmospheric dispersion model FLEXPART. This tool ECMWF/FLEXPART was analyzed in normal operating conditions in the Western Mediterranean Basin during 45 days at summer 2010. From comparison with NORMTRI plumes over Western Mediterranean Basin the real time results have demonstrated an overestimation of the corresponding climatologically sequence Tritium concentrations in air outputs, at several distances from the reactor. For these purpose two clouds development patterns were established. The first one was following a cyclonic circulation over the Mediterranean Sea and the second one was based in the cloud delivered over the Interior of the Iberian Peninsula by another stabilized circulation corresponding to a High. One of the important remaining activities defined then, was the tool qualification. The aim of this paper is to present the ECMWF/FLEXPART products confronted with Tritium concentration in air data. For this purpose a database to develop and validate ECMWF/FLEXPART tritium in both assessments has been selected from a NORMTRI run. Similarities and differences, underestimation and overestimation with NORMTRI will allowfor refinement in some features of ECMWF/FLEXPART.

DOSE TO THE PUBLIC FROM TRITIUM RELEASED TO THE ATMOSPHERE FROM THE LIVERMORE SITE OF LAWRENCE LIVERMORE NATIONAL LABORATORY, 1953 THROUGH 2005

Throughout 53 years of operations, an estimated 29,300 TBq of tritium were released to the atmosphere at the Livermore site of Lawrence Livermore National Laboratory (LLNL); about 75% of this was released as tritium gas primarily in two accidental releases. A tritium dose reconstruction was undertaken to chronicle both the annual doses to the public for each year of operations and the doses from seven accidental releases. Although LLNL has always reported releases and calculated doses in compliance with regulatory requirements, annual doses were not calculated prior to 1973, and the only dose reported from an accidental release was that in 1970. Annual doses (means and 95% confidence intervals) for 1953 through 2005 to the most exposed members of the public were calculated using the same equilibrium dose model and assumptions. From 1973 through 2005, predicted tritium concentrations in air were compared with observed mean annual concentrations at one location, and predicted doses were compared with those reported by LLNL. A mean dose with 95% confidence interval was also calculated for each accidental release using an equation derived from extensive experience with a dynamic process-oriented model. Predicted air concentrations were overestimated, on average, by a factor of 1.6, 70% of the doses reported by LLNL in annual compliance documents fell within the predicted confidence intervals, and all predicted doses from routine and accidental releases were well below regulatory limits. The highest annual mean dose to an adult was 34 microSv in 1957; the highest dose from an accidental release was 330 microSv in 1954.

Development of Dose Assessment Code for Accidental Tritium Releases-ACUTRI-

A computer code named ACUTRI has been developed to assess tritium doses due to inhalation to the general public. The ACUTRI code can calculate the radiological impact of tritium gas (HT) and tritiated water (HTO) released accidentally to the atmosphere. The models in this code consist of a tritium transfer model including the oxidation of HT to HTO and the reemission of HTO from soil to the atmosphere and a dose calculation model. The atmospheric dispersion of the primary HT and HTO plumes and secondary HTO plume, which is reemitted from soil to the atmosphere, is calculated by using the Gaussian plume model. In this calculation, it is possible to analyze the meteorological data statistically, in the same way as a conventional dose assessment method according to the meteorological guideline of the Nuclear Safety Commission of Japan. Tritium concentrations in air and their resultant doses were calculated using the ACUTRI code under several conditions. In order to validate the model, calculations were compared with experimental results.

TEST OF CAP88-PC???S PREDICTED CONCENTRATIONS OF TRITIUM IN AIR AT LAWRENCE LIVERMORE NATIONAL LABORATORY

Based on annual tritium release rates from the five sources of tritium at Lawrence Livermore National Laboratory and the Tritium Research Laboratory at Sandia National Laboratory, the regulatory dispersion and dose model, CAP88-PC, was used to predict tritium concentrations in air at perimeter and offsite air surveillance monitoring locations for 1986 through 2001. These predictions were compared with mean annual measured concentrations, based on biweekly sampling. Deterministic predictions were compared with deterministic observations using predicted-to-observed ratios. In addition, the uncertainty on observations and predictions was assessed: when the uncertainty bounds of the observations overlapped with the uncertainty bounds of the predictions, the predictions were assumed to agree with the observations with high probability. Deterministically, 54% of all predictions were higher than the observations, and 96% fell within a factor of three. Accounting for uncertainty, 75% of all predictions agreed with the observations; 87% of the predictions either matched or exceeded the observations. Predictions equaled or exceeded observations at those sampling locations towards which the wind blows most frequently, except those in the hills. Under-predictions were seen at locations towards which the wind blows infrequently when released tritium was from elevated sources. When a high fraction of tritium was from area (diffuse) sources, predictions matched observations.

ETDOSE: A Code to Simulate Tritium Transfer in the Environment and to Evaluate Dose

ABSTRACTETDOSE is a simple computer code for calculating distribution patterns of tritium in the environment for acute and chronic releases of HT and HTO. It calculates tritium concentrations in air, soil, plant free water and plant organic material, and estimates dose impacts from inhalation of air and ingestion of food. ETDOSE includes two different models for calculating HTO re-emission from the soil surface for a chronic tritium release. These two models were tested in the IAEA’s model validation program BIOMASS (BIOsphere Modeling and ASSessment methods)1.

Environmental tritium around a new CANDU nuclear power plant

In the routine operation of a nuclear power plant radioactive wastes are generated. Excepting 3 H and 14 C, the quantities of radionuclides released during normal operation of CANDU 6, are smaller than emissions of other NPP. The tritium inventory and the tritium releases for classical and future (improved) CANDU 6 were theoretically evaluated and compared with the published data of CANDU 6 reactors with more than 10 years of operation. The tritium releases increases with time and no equilibrium is reached in the 30 years.The environmental tritium level before and after the start of the Romanian CANDU 6 reactor was determined by analysis of different samples: air, water, soil, and vegetation. During the pre-operational period, the tritium concentration was low and almost uniform (~3 Bq/L), as for an area without local contamination sources other than common atmospheric fallout. In the first years of the reactor activity, the tritium concentration in environment was low, but more variable than pre-operation period. In the vicinity of the reactor, the tritium concentration in air, soil and spontaneous vegetation was till two orders of magnitude higher than the values measured during the pre-operational level. The dose estimation for the maximum exposed individual, consuming local products, is 1.6 µSv/y.

Deposition of tritiated water vapour to water surface in an outdoor field.

Deposition of tritiated water vapour in the atmosphere to a water surface was studied in an outdoor field, where elevated concentrations of tritiated water vapour existed in the atmosphere over twelve days. Exchange velocities of tritiated water vapour between air and water were evaluated from tritium concentrations in air and water obtained in the field experiment. It was found that the average of outdoor exchange velocities was about three times greater than that observed in a nuclear reactor room previously. Relationships between the outdoor exchange velocities and meteorological conditions were analysed to derive a multiple correlation equation. The wind speed was strongly correlated with the exchange velocity and the air temperature appeared to have an enhancing effect on the velocity. These observations were supported by a follow-up experiment conducted on a laboratory scale.

Predicting Detritiation-Dryer Performance at Low Activities

A simple method of predicting the tritium concentration in air leaving an atmospheric-detritiation dryer (ADD) was developed and compared to experimental data. The prediction method was developed for use with closed-loop regenerated, thermal-swing dryers by extending the constant-pattern method for analyzing desiccant dehumidifiers. Tests were carried out at tritium activities up to 3 500 GBq/kg. For ADDs filled with commercial, zeolite desiccants, it was found that the prediction method provided a reasonable worst-case estimate of the tritium concentration (Bq/m3) exiting a dryer during adsorption.

The Vegetation-to-air Concentration Ratio in a Specific Activity Atmospheric Tritium Model

Specific activity models are frequently used to estimate the concentration of tritium oxide in vegetation. In such models, a single value represents the ratio (R) of the specific activity of tritium oxide in vegetation to the specific activity of atmospheric tritium oxide. Federal agencies such as the Nuclear Regulatory Commission and the Environmental Protection Agency have not established a consensus default for R. Literature on this topic suggests that a site-specific distribution of R should be developed when feasible. In this study, a distribution of R is established for the Savannah River Site. Environmental tritium concentrations in air and vegetation measured on and around the Savannah River Site over a 9-y period form the basis for the analysis. For dose assessments of chronic atmospheric tritium releases at the Savannah River Site, R is best parameterized by a normal distribution with a mean of 0.54 and one standard deviation of 0.10. The Nuclear Regulatory Commission default for R is approximately equal to the Savannah River Site site-specific estimate. Based on the results, the default value for R recognized by the Environmental Protection Agency overestimates tritium concentrations in vegetation and, therefore, doses from foodstuff consumption pathways at humid sites. For the Savannah River Site, the magnitude of the error is on the order of a factor of 2. This consideration may be important if an estimated dose approaches an as-low-as-reasonably-achievable or regulatory threshold. Conversely, without the benefit of site-specific data, ingestion doses may be underestimated in regions with dry climates.

Tritium Measurement and Monitoring in Experimental and Process Systems with Ionization Chambers

Historically, ionization chambers have been used successfully to measure low-level tritium concentrations in air for radiation protection purposes. Problems have been encountered in applying this t...

Tritium inventory in portland cement exposed to trttiated water vapor

Interactions between penetrating tritiated water and hydrogen species originally present in cement materials were evaluated to estimate the tritium inventory in cement materials exposed to tritiated water vapor. Approximately 80% of the penetrated tritiated water was found to be contained in free liquid water. Tritiated water was considered to interact with cement materials by means of exchange reactions between tritium and hydrogen atoms. The concentration of tritium interacting with materials was considered to be proportional to the tritium concentration in air. The tritium inventory in cement materials was thus dependent on the porosity of the material.

A tritium-in-air monitor with compensation and additional recording of alpha -, beta -, and gamma -backgrounds

The development of a computer-controlled tritium-in-air monitoring using flow-through air proportional counters as the detector is described. Combining automatic compensation for beta - and gamma -backgrounds with alpha -background discrimination, the monitor can detect tritium activity separately from other radioactive gases. The computer calculates and prints out not only tritium concentration in air but also dose equivalent rate by external gamma -rays and/or activity concentrations of other radioactive gases than tritium in real time. Since the monitor has a wide range of 0.005-5000 Bq/cm/sup 3/ (6 decades) and a short response time of several minutes, it can be used effectively to monitor tritium in air in fission and fusion reactor environments.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

HTO Reemission from Soil after HT Deposition and Dose Consequences of HT Releases

With respect to inhalation doses the reemission of HTO from the area source established in soil after HT releases is the most important process. In two field experiments performed in France and Canada reemission was studied by successive evaluations of tritium contents in soil and corresponding air samples. It was found that the reemission rate is essentially dependent upon the specific activities in air and soil. Evaporation conditions support reemission, while dew formation and rainfall as well as HTO diffusion into deeper soil layers have the opposite effect. Dose consequences of a HT release were evaluated from time-integrated tritium concentrations in air and breathing rates as well as by analyses of urine samples of the experimenter.

Development of a Tritium Dispersion Code

This paper describes the development and verification of a computer code designed to calculate the radiation dose to man following acute or chronic atmospheric releases of tritium gas and oxide from a point source. The Ontario Hydro Tritium Dispersion Code calculates tritium concentrations in air, soil, and vegetation and doses to man resulting from inhalation/immersion and ingestion of food, milk meat and water. The deposition of HT to soil, conversion of HT to HTO by soil enzymes and resuspension of HTO to air have been incorporated into the terrestrial compartment model and are unique features of the code. Sensitivity analysis has identified the HT deposition velocity and the equivalent water depth of the vegetation compartment as two parameters which have a strong influence on dose calculations. Tritium concentrations in vegetation and soil calculated by the code were in reasonable agreement with experimental results. The radiological significance of including the mechanisms of HT to HTO conversion and resuspension of HTO to air is illustrated.

Precautions in the measurement of tritium concentrations in air when using flow-through ion chambers

Instruments with flow-through ion chambers are frequently used to measure the concentration of tritium gas in air. However, these simple instruments can give erroneous results because of: cigarette smoke, aerosols, ions, ambient gamma-ray field changes, moisture and condensation, absorption and memory effects, clogged filters, fission product gases, radon, and incorrect instrument calibration. The causes of these errors are explained and chart recordings are presented showing some of them in action. Most problems can be avoided using the proper instrument design and safeguards described and by adequate calibration techniques. A tritium monitor should be checked and calibrated with tritium gas, not gamma-rays or ions. The most accurate calibration is obtained when the instrument operates in a closed loop so that the tritium concentration is constant, a steady meter reading being obtained independent of air flow rate and instrumental time constants.

Tritium Concentrations in Air and in Urine of Workers Resulted from Tritium Handling

Tritium content in air and urine of workers was measured during and after the handling of about 30Ci tritium.Tritium content in environmental samples such as air and air-condensed water collected by a cold trap method was determined using a tritium monitor or a liquid scintillation counter. Internal radiation dose was estimated for workers by the analysis of their urine.The tritium concentration in air was about 10-9μCi/cm3 at the beginning of work, whereas the maximum value was observed during the working period as 2.6×10-4μCi/cm3 in hood, 1.3×10-6μCi/cm3 in laboratory and 1.8×10-7μCi/cm3 in corridor. The daily urinary excretion of tritium was represented approximately by a single exponential function with the effective half-lives of 14 days and 12 days for two workers, and their internal radiation dose was estimated as 12 mrem and 7.1 mrem respectively.