Tritium Emissions Research Articles

Теоретический анализ качества излучения и относительной биологической эффективности трития

Introduction 1. Tritium and reference radiation 1.1 Tritium isotope and its energy spectrum 1.2 Reference radiation 2. Methods for determining the quality of radiation and RBE 2.1 Radiation quality in microdosimetry 2.2 RBE by the number of DNA double-strand breaks 2.3 RBE by fraction of secondary low-energy electrons 3. Analysis of calculations of radiation quality and tritium RBE 3.1 Estimation of tritium emission quality factors 3.2 Evaluation of the RBE of tritium radiation during its action on DNA 3.3 Estimation of the RBE of tritium from the fraction of secondary low-energy electrons 3.4 Quality factors and RBE of tritium with respect to reference emissions Conclusion

Study on tritium transport characteristics in fluoride-salt-cooled high-temperature advanced reactor

Fluoride-salt-cooled high-temperature reactors (FHRs) are a promising reactor class that combines prominent attributes from the Gen-Ⅳ reactors, raising attractive interests of the international community. However, tritium control has been a major challenge in FHRs because of the neutron reactions of lithium. It's necessary to study the transport characteristics of tritium in the fluoride-salt-cooled high-temperature advanced reactor (FuSTAR) and to provide theoretical support for appropriate tritium control measures and safe operation of the FHRs. In this paper, the inclusive transport characteristics of production, graphite adsorption, diffusion, dissolution, and permeation on tritium in the primary loop are analyzed. The mathematical and physical model of the tritium transport phenomenon is established, and an analysis model of tritium transport characteristics is also developed. Then, the tritium transport characteristics in the FuSTAR primary loop are analyzed. The results show that the tritium in the FuSTAR primary loop mainly exists in the form of Diatomic Tritium (T2), and it's found that Tritium Fluoride (TF) and T2 are adsorbed by graphite after being generated in the core, and this process reaches saturation in about 150 Effective Full Power Days (EFPDs). It also indicates that almost 48% of tritium penetrates the secondary loop through the heat exchanger, and only about 3.8% of tritium is adsorbed on the core graphite. TF makes the corrosion of the heat exchanger and downcomer more serious. Finally, the safety of tritium transport in FuSTAR is conservatively estimated, with a tritium emission dose of 0.1674 mSv/a. This study can provide a theoretical reference for the structural design, tritium recycling, and radiation protection of FHRs.

De Novo Design of a Pt Nanocatalyst on a Conjugated Microporous Polymer-Coated Honeycomb Carrier for Oxidation of Hydrogen Isotopes.

A booming demand for energy highlights the importance of an emergency cleanup system in the nuclear industry or hydrogen-energy sector to reduce the risk of hydrogen explosion and decrease tritium emission. The properties of the catalyst determine the efficiency of hydrogen isotope enrichment and removal in the emergency cleanup system. However, the aggregation behavior of Pt, deactivation effect of water vapor, and isotope effect induce a continuous decrease in the catalytic activity of the Pt catalyst. Herein, a de novo design of a Pt nanocatalyst is proposed for catalytic oxidation of the hydrogen isotope via modification of a conjugated microporous polymer onto honeycomb cordierite as a Pt support. The conjugated microporous polymer creates a microporous and hydrophobic environment to attenuate the deactivation effect of water vapor and shape Pt nanoparticles with a diameter of around 2.4 nm. Thus, the as-prepared catalysts exhibit excellent catalytic performance in the range of 25-65 °C and high space velocity (≤30 000 h-1) and a stable and high catalytic activity during 487 h of continuous and intermittent operation. Importantly, the charge of the Pt nanoparticles is redistributed by the conjugated skeletons, leading to a decreased energy barrier in the rate-limiting step of hydrogen isotope oxidation and a reduced isotope effect.

Tritium in the aquatic environment of Ozersk

Introduction. The article presents data on tritium concentrations in various types of aquatic environments (rainfall, snowfall, water from the Irtyash, B. Nanoga, Kyzyltash lakes, and the source of the Techa river, tap water, ice from the refrigerator, and urine) within the city of Ozersk and on the territory immediately adjacent to it in the impact zone of Mayak Production Center in the Southern Urals. Material and methods. For the quantitative determination of tritium in various aqueous media, sampling was carried out from 2002 to 2016. Samples were analyzed by the scintillation method using a single-stage electrolytic enrichment procedure. Results. Almost all aquatic environments in Ozersk in terms of their tritium content exceed the technogenic background established for the Ural region. On average, this excess is by 14, 11, 9, 19, 4, 6, 19 times for rainfall, snowfall, drinking water of residential premises, ice, the water of the Irtyash and B. Nanoga lakes, water from the source of the river Techa accordingly. Elevated concentrations of tritium in the urine of Ozersk people and the adjacent territory were noted in comparison with literature data for other regions of the world. Conclusion. The obtained research results revealed the levels of pollution of the aquatic environment of Ozersk with tritium relative to the level of technogenic background. These works indicate the need to develop a method for cleaning tritium emissions and discharges by nuclear enterprises to reduce the risk to the population.

Search and Measurement of P-Odd Asymmetry in the Emission of Secondary Particles Produced in Reactions of Polarized Thermal and Cold Neutrons with Light Nuclei

Investigation of spatial parity in reactions of polarized neutrons with light nuclei is an important topic in the framework of exploring the fundamental problem of understanding the manifestation of the weak interaction in nuclear reactions and for estimating the parameters of the weak nucleon–nucleon interaction. In this paper, the ongoing experimental program of highly sensitive and high-precision measurements of P‑odd asymmetries in the reactions of polarized thermal and cold neutrons with lithium and boron nuclei is reviewed. Within this program, the coefficients of P-odd asymmetry of reaction products in the reactions induced by cold- and thermal-neutrons on the isotopes of light nuclei 6Li and 10B were measured with record-high sensitivity ~10–8 as $$\alpha _{{P{\text{ - odd}}}}^{{^{{\text{6}}}{\text{Li}}{\text{,exp}}}} = - (8.8 \pm 2.1) \times {{10}^{{ - 8}}}$$ , $$\alpha _{{P{\text{ - odd}}}}^{{^{{10}}{\text{B}},\gamma ,\exp }} = (0.0 \pm {{2.6}_{{{\text{stat}}.}}} \pm {{1.1}_{{{\text{syst}}{\text{.}}}}}) \times {{10}^{{ - 8}}},$$ and $$\alpha _{{P{\text{ - odd}}}}^{{{{\alpha }_{0}} + {{\alpha }_{1}}{{,}^{{10}}}B,\exp }} = - (11.2 \pm 3.4) \times {{10}^{{ - 8}}}$$ . For the first time ever, nonzero values were obtained for two of these asymmetries. Our data for tritium emission in the $$^{6}{\text{Li(}}n,a{{)}^{3}}{\text{H}}$$ reaction and γ emission in the $$^{{10}}{\text{B}}{{(n,a)}^{{74}}}{\text{Li}}^{*} \to \gamma \to {{\,}^{7}}{\kern 1pt} {\text{Li(gr}}{\text{.st}}{\text{.)}}$$ reaction agree with those of other experiments when interpreted within the cluster model, but rule out the so-called “best DDH values” of weak-interaction coupling constants. Interpreting the data on these reactions relying on “first principles” only would be highly desirable.

Tritium Entry Into the Atmosphere with Emissions from NPP-VVER and Population Irradiation Dose Assessment

Tritium emissions from NPP with VVER were estimated based on radiation and technical survey data. It is shown that the population in the NPP-VVER observation zone consumes a significant amount of imported food products, so that equality is not reached between the specific activity of tritium in the water of human tissues and atmospheric water. Taking this into account, an evidenced model is developed for reducing the conservatism in the estimation of the yearly dose from standard tritium emissions from NPP as compared with the currently operative procedures and recommendations. The estimated yearly irradiation dose to the critical group of the population from tritium emissions is as follows at NPP (μSv/yr): 0.09 Balakovo, 0.07 Rostov, 0.06 Novovoronezh, 0.04 Kalinin, and 0.015 Kola. The contribution of tritium emission from the spray-cooling pools at the NPP in Balakovo and Rostov in the yearly population irradiation dose is estimated.

An Evaluation of the Global Effects of Tritium Emissions from Nuclear Fusion Power

Tritium, like all hydrogen isotopes, is difficult to confine and easily diffuses through most materials. As currently planned, fusion power plants will process and handle large quantities of deuterium and tritium as fuel, and therefore, will become sources of tritium input into the environment. Tritium releases from a worldwide distribution of tritium sources (fusion or fission) will lead to higher tritium levels overall and have global impact. This report investigates the hydrologic partitioning of yearly tritium releases assuming 1 g/yr loss per 500 MW of nuclear power generation for varying scales of power generation. On large scales, it is found that the worldwide average levels of tritium could exceed some public health goals and regulatory guidelines. Tritium concentrations at such levels may also have other impacts on the environment through increased ion-pair generation.

Calculation of Particle Emissions and Fusion Cross Sections After 8B(t,*), 9B(t,*), and 10B(t,*) Reactions by Monte Carlo Simulations

Boron nuclide and tritium projectile interactions are considerable in terms of nuclear energy systems. This study aims to investigate the realization of the nuclear fusion reactions of the bombardment of boron nuclei with tritium. In addition, the 8B(t,*), 9B(t,*), and 10B(t,*) reactions have focused on the use of the resulting product particles in nuclear technology applications, particularly in nuclear medicine applications, in terms of energy and number. Tritium-induced reactions from boron isotopes (8B, 9B, and 10B) at 50 and 100 MeV were modeled by the GEANT4 and EMPIRE Monte Carlo codes. Gamma, alpha, tritium, deuteron, proton, and neutron emission spectra (GEANT4-10.3) were obtained, and cross sections per energy (EMPIRE-3.2-MALTA) were calculated. Fusion cross sections and 6Li and 7Li production cross sections, which are critical in thermonuclear fusion reactors as basic fusion reactions, are discussed based on the 8B(t,*), 9B(t,*), and 10B(t,*) reactions.

Analysis on the emission of tritium from Qinshan nuclear power base of china in recent ten years

The emissions of tritium in airborne and liquid effluent from Qinshan nuclear power base in the period from 2007 to 2016 are counted, and compared with the global average emission level. The results show that the tritium emissions from the Qinshan nuclear power base in the past ten years have met the Chinese national standard limits. Compared with the global average emission data and the US commercial pressurized water reactor nuclear power plant emission data, the tritium emissions of PWR units are at the same level. Emissions from heavy water reactors of the Qinshan nuclear power base are lower than global average emissions (about 10% of the global average) and lower than the Canadian average emission level.

Preliminary environmental radiation considerations for CFETR

Since Chinese fusion engineering test reactor (CFETR) stepped into the engineering design phase, it was significant to discuss the environmental radiation issues considering both Chinese radiation safety regulations and lessons learned from international thermonuclear experimental reactor (ITER) being constructed in France. In this study, firstly, the legal and regulatory framework of nuclear safety in China and ITER licensing process lessons were reviewed. Secondly, public dose limit was proposed for CFETR. Thirdly, safety limit and radioactive source terms were discussed and proposed for CFETR. Fourthly, public radiation dose was estimated, tritium emission limit was proposed under normal operation from the perspectives of tritium emission limit for nuclear power plants (NPPs) in China and reverse value based on public dose limit. Finally, potential consequences of environmental radiation were discussed under accidental conditions. Nuclear emergency countermeasures including no evacuation criteria needed or not were proposed. The preliminary environmental radiation considerations were proposed for CFETR: 1) It had better invite the experts from Chinese national nuclear safety administration (NNSA) to participate in the engineering design, which can make the related persons understand the fusion safety characteristics as early as possible, so as to further speed the licensing process; 2) 0.1 mSv/a was proposed as the public dose limit of CFETR under normal operation; 3) The same ITER safety limit was proposed to be set for CFETR from the consideration of both comparable size of vacuum vessel (VV) and hydrogen/dust explosion; 4) A tritium emission limit of 5–33 g/a was proposed for CFETR; 5) The “no off-site emergency response” was suggested as one of the safety goals during the design of CFETR, however, “off-site emergency measures” were still proposed to be deployed during the operation of CFETR. It was expected the environmental radiation considerations could provide a reference to speed the construction of CFETR on the premise of environment friendly and public safety.

Safety and Tritium Applied Research Facility Annual Atmospheric Tritium Emissions

The Safety and Tritium Applied Research (STAR) facility provides the capabilities and infrastructure to support tritium research activities important to fusion research and development. Atmospheric tritium emissions are an expected byproduct of STAR laboratory operations and are monitored in accordance with federal regulations. This paper describes the STAR facility Stack Tritium Monitoring System, presents and discusses the annual STAR facility tritium emissions from 2004 to 2017, and briefly describes ongoing efforts to reduce atmospheric tritium emissions from the facility stack. Modeling calculations indicate that STAR facility atmospheric tritium emissions do not pose any health threat to the maximum exposed individual member of the public.

Direct tritium emissions to the ocean from the Fukushima Dai-ichi nuclear accident

In this work we report tritium concentrations determined in seawater samples collected offshore of Fukushima in the northwestern Pacific Ocean, immediately after the Fukushima Dai-ichi Nuclear Power Plant (F1-NPP) accident. We found surface seawater to have high concentrations of tritium (3H) and cesium-137 (137Cs) with respect to the concentrations expected for the investigated region. Tritium concentrations were up to six times the pre-accident level. However, these concentrations were found to be relatively low compared to those of 137Cs and 129I. This is most likely because of the very low production ratio of tritium to 137Cs in the F1-NPP, and the inherently high background concentration of tritium in these environmental waters (mainly ascribed to global fallout from nuclear weapons tests conducted during the 1960s). The tritium distribution in surface seawater showed higher concentrations close to the shore and lower concentrations offshore. Higher tritium concentration areas had spread both northward and southward from the F1-NPP along the coast, indicating that large amounts of tritium were carried by coastal currents. A positive correlation was found to exist between 3H and 137Cs concentrations in the seawater. The calculated 3H/137Cs ratio was similar to the production ratio of these isotopes reported for the broken reactors in the F1-NPP, which indicates that both radionuclides might have originated from the F1-NPP. Direct emission of tritium to the ocean from the F1-NPP was estimated to be approximately 0.05 PBq immediately after the accident, which is much smaller than the total inventory in the environment.

Water Detritiation System for ITER—Evaluation of Design Parameters

The Water Detritiation System (WDS) designed for ITER is based on the combined electrolysis and catalytic exchange(CECE) process to ensure the emission of tritium to the environment is maintained below very strict limits. The CECE process is one of the processes for tritium removal that CNL (Canadian Nuclear Laboratories, formerly Atomic Energy of Canada Ltd.) has studied, developed and successfully demonstrated. In this work, CNL evaluated ITER’s design conditions of the exchange column and the electrolyser – the two key components of the CECE process (and the ITER WDS system) – to assess the effectiveness of tritium removal and investigate options to improve it. The evaluation was done using CNL’s CECE process simulation according to a protocol set out by ITER. Initially, calibration (benchmarking) of CNL’s hydrogen-water exchange column model was performed with a standard data set for a specified column to determine modeling parameters that resulted in a good match with the tritium concentration data. The model was then applied (with the same parameters) to the current WDS design. Some optimized conditions for the CECE process that could improve performance of the WDS to meet its design criteria were determined. The details of some of these assessments are presented here with particular attention to the WDS case where the feed water contains high levels of deuterium.

A New Hydrogen Processing Development System

The design of many of the process systems at the Savannah River Site (SRS) Tritium Facilities were developed at the Savannah River National Laboratory (SRNL) in the 1980’s and early 1990’s for Cold War production requirements. Most of the process systems developed used cold (non-radioactive) test systems to reduce the cost of developing pilot and full-scale test systems. The metal hydride (MH) based process technologies developed for the Replacement Tritium Facility (RTF) allowed tritium process equipment to be confined in tritium stripped glovebox systems which greatly reduced tritium emissions to the public. Facility start-up in 1994 was considered state-of-the art technology for the world’s largest metal hydride based tritium process facility. The end of the Cold War reduced production requirements, but increased maintenance is needed for the 20 year old process systems. The Hydrogen Processing Development System (HPDS) is a new, non-radiological R&D system to be built for testing and demonstrating improved process systems for SRS Tritium Facilities. Experience gained from facility operations and new concepts from fusion fuel cycle development programs will be used to develop improved processes and restore base capabilities of the SRS Tritium Facilities. The HPDS will be designed to test systems such as a Revised Unloading Purification System (RUPS), an optimized advanced storage and isotope separation (OASIS) System, a Reduced Area Confinement and WAter Processing (RACWAP) System, and some components of a separate breeding and extraction program. New processes would retain the desirable features of the current/existing technologies while creating “right-sized” and flexible advanced or hybrid system to meet current and future tritium processing needs. Testing in the HPDS will reduce the cost and risk of deploying new technologies into the SRS tritium production process.

Canadian inter-laboratory organically bound tritium (OBT) analysis exercise

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.

Replacement of Tritiated Water from Irradiated Fuel Storage Bay

Recently, AECL developed a novel method to reduce tritium emissions (to groundwater) and personnel doses at the NRU (National Research Universal) reactor irradiated fuel storage bay (also known as rod or spent fuel bay) through a water swap process. The light water in the fuel bay had built up tritium that had been transferred from the heavy water moderator through normal fuel transfers. A demonstration of the method was done that involved Computational Fluid Dynamics (CFD) modeling of the swap process and a test program that showed excellent agreement with model prediction for the effective removal of almost all the tritium with a minimal water volume. Building on the successful demonstration, AECL fabricated, installed, commissioned and operated a full-scale system to perform a water swap. This paper describes the results of the successful full-scale water swap operation, which achieved a tritium removal efficiency of ~96%

Estimating cancer risk in relation to tritium exposure from routine operation of a nuclear-generating station in Pickering, Ontario

Evidence suggests that current levels of tritium emissions from CANDU reactors in Canada are not related to adverse health effects. However, these studies lack tritium-specific dose data and have small numbers of cases. The purpose of our study was to determine whether tritium emitted from a nuclear-generating station during routine operation is associated with risk of cancer in Pickering, Ontario. A retrospective cohort was formed through linkage of Pickering and north Oshawa residents (1985) to incident cancer cases (1985-2005). We examined all sites combined, leukemia, lung, thyroid and childhood cancers (6-19 years) for males and females as well as female breast cancer. Tritium estimates were based on an atmospheric dispersion model, incorporating characteristics of annual tritium emissions and meteorology. Tritium concentration estimates were assigned to each cohort member based on exact location of residence. Person-years analysis was used to determine whether observed cancer cases were higher than expected. Cox proportional hazards regression was used to determine whether tritium was associated with radiation-sensitive cancers in Pickering. Person-years analysis showed female childhood cancer cases to be significantly higher than expected (standardized incidence ratio [SIR] = 1.99, 95% confidence interval [CI]: 1.08-3.38). The issue of multiple comparisons is the most likely explanation for this finding. Cox models revealed that female lung cancer was significantly higher in Pickering versus north Oshawa (HR = 2.34, 95% CI: 1.23-4.46) and that tritium was not associated with increased risk. The improved methodology used in this study adds to our understanding of cancer risks associated with low-dose tritium exposure. Tritium estimates were not associated with increased risk of radiationsensitive cancers in Pickering.

Validation Test for CAP88 Predictions of Tritium Dispersion at Los Alamos National Laboratory

Gaussian plume models, such as CAP88, are used regularly for estimating downwind concentrations from stack emissions. At many facilities, the U.S. Environmental Protection Agency (U.S. EPA) requires that CAP88 be used to demonstrate compliance with air quality regulations for public protection from emissions of radionuclides. Gaussian plume models have the advantage of being relatively simple and their use pragmatic; however, these models are based on simplifying assumptions and generally they are not capable of incorporating dynamic meteorological conditions or complex topography. These limitations encourage validation tests to understand the capabilities and limitations of the model for the specific application. Los Alamos National Laboratory (LANL) has complex topography but is required to use CAP88 for compliance with the Clean Air Act Subpart H. The purpose of this study was to test the accuracy of the CAP88 predictions against ambient air measurements using released tritium as a tracer. Stack emissions of tritium from two LANL stacks were measured and the dispersion modeled with CAP88 using local meteorology. Ambient air measurements of tritium were made at various distances and directions from the stacks. Model predictions and ambient air measurements were compared over the course of a full year's data. Comparative results were consistent with other studies and showed the CAP88 predictions of downwind tritium concentrations were on average about three times higher than those measured, and the accuracy of the model predictions were generally more consistent for annual averages than for bi-weekly data.

Relation between the tritium in continuous atmospheric release and the tritium contents of fruits and tubers

Concentrations of organically bound tritium (OBT) and tissue-free water tritium (TFWT, also referred to as HTO) in fruits and tubers were measured at a garden plot in the vicinity of the source of chronic airborne tritium emissions during the 2008, 2010, and 2011 growing seasons. A continuous record of HTO concentration in the air moisture was reconstructed from the continuous record of Ar-41 ambient gamma radiation, as well as from frequent measurements of air HTO by active samplers at the garden plot and Ar-41 and air HTO monitoring data from the same sector. Performed measurements were used for testing the modified Specific Activity (SA) model based on the assumption that the average air HTO during the pod-filling period provides an appropriate basis for estimating the levels of OBT present in pods, fruits and tubers. It is established that the relationship between the OBT of fruits and tubers and the average air HTO from a 15–20 day wide window centred at the peak of the pod-filling period is consistent throughout the three analysed years, and could be expressed by the fruit or tuber's OBT to air-HTO ratio of 0.93 ± 0.21. For all three years, the concentration of HTO in fruits and tubers was found to be related to levels of HTO in the air, as averaged within a 3-day pre-harvest window. The variability in the ratio of plant HTO to air HTO appears to be three times greater than that for the OBT of the fruits and tubers. It is concluded that the OBT of fruits and tubers adequately follows an empirical relationship based on the average level of air HTO from the pod-filling window, and therefore is clearly in line with the modified SA approach.

Tritium Emissions from a Detritiation Facility

Tritium is produced in heavy-water reactors through neutron capture by the deuterium atom. Annual production of tritium in a CANDU reactor is typically 52-74 TBq/MW(e). Some CANDU reactor operators have implemented detritiation technology to reduce both tritium emissions and dose to workers and the public from reactor operations. However, tritium removal facilities also have the potential to emit both elemental tritium and tritiated water vapor during operation. Authorized releases to the environment, in Canada, are governed by Derived Release Limits (DRLs). DRLs represent an estimate of a release that could result in a dose of 1 mSv to an exposed member of the public. For the Darlington Nuclear Generating Station, the DRLs for airborne elemental tritium and tritiated water emissions are ∼15.6 PBq/week and ∼825 TBq/week respectively. The actual tritium emissions from Darlington Tritium Removal Facility (DTRF) are below 0.1% of the DRL for elemental tritium and below 0.2% of the DRL for tritiated water vapor. As part of an ongoing effort to further reduce tritium emissions from the DTRF, we have undertaken a review and assessment of the systems design, operating performance, and tritium control methods in effect at the DTRF on tritium emissions. This paper discusses the results of this study.