Tritium Levels Research Articles

Tritium Accounting Stability of a ZrCo Bed with “In-Bed” Gas Flowing Calorimetry

Zirconium-Cobalt (ZrCo) tritium storage bed with “in-bed” gas flowing calorimetry has been developed as a self-assaying system for the Tritium Storage and Delivery System of ITER. The basic tritium accounting characteristics have been investigated and practical data on the accounting stability has been accumulated under gram level tritium storage for more than 8 years. The initial sensitivity of tritium was about 0.05 g and the accuracy (standard deviation of repeat measurements: two sigma) was about 0.15 g at full tritium storage of 25 g. This initial accounting performance has been maintained after tritium storage for more than 8 years by keeping constant accounting conditions at each inventory measurement. Almost no aging effect of tritium was found except accumulation of 3He in the primary ZrCo tritide vessel, which was easily evacuated to keep initial accounting condition before each inventory measurement.

DISTRIBUTION OF TRITIUM IN THE LEACHATES AND METHANE GAS CONDENSATES FROM MUNICIPAL WASTE LANDFILLS IN KOREA

In this paper, the tritium levels in the leachates and methane gas condensates which have occurred at 13 sanitary landfills of municipal solid wastes (MSW) are investigated and reported. During the 6 months investigation period, the mean tritium concentrations of the raw leachates were distributed from 17 to 1,196 TU. They corresponded to several scores or hundreds higher tritium levels than that of the normal environmental level except for two cases. High tritium levels were also detected in the effluents of the leachate treatment facilities. Generally, the tritium existed in the dissolving fraction of the leachate but for some cases about 10% of the total tritium content was present as colloidal particles of over 0.45 μm in size. In general, the relationship between the tritium and other contaminants in the raw leachate was low, but it was relatively high between the tritium and TOC. Thus, it is predicted that the dissolving state of the tritium in the leachates would be affected by the tritium sources of the tipped wastes in a MSW.

Tritium in well waters, streams and atomic lakes in the East Kazakhstan Oblast of theSemipalatinsk Nuclear Test Site

The concentration of tritium has been determined in well waters, streams and atomic lakesin the Sarzhal, Tel’kem, Balapan and Degelen Mountains areas of the Semipalatinsk TestSite. The data show that levels of tritium in domestic well waters within thesettlement of Sarzhal are extremely low at the present time with a median value of4.4 Bq dm−3 (95% confidenceinterval: 4.1–4.7 Bq dm−3). These levels are only marginally above the background tritium content in surface watersglobally. Levels in the atomic craters at Tel’kem 1 and Tel’kem 2 are between one and twoorders of magnitude higher, while the level in Lake Balapan is approximately12 600 Bq dm−3. Significantly, levels in streams and test-tunnel waters sourced in theDegelen Mountains, the site of approximately 215 underground nucleartests, are a further order of magnitude higher, being in the range133 000–235 500 Bq dm−3. No evidence was adduced which indicates that domestic wells in Sarzhal arecontaminated by tritium-rich waters sourced in the Degelen massif, suggesting that thelatter are not connected hydrologically to the near-surface groundwater rechargingthe Sarzhal wells. Annual doses to humans arising from the ingestion of tritiumin these well waters are very low at the present time and are of no radiologicalsignificance.

Environmental tritium in the vicinity of Creys-Malville nuclear power plant

The results of an environmental survey of tritium in the vicinity of Creys-Malville nuclear plant are presented. The plant, which was shut down in 1998, is currently in its initial stage of dismantling. Measurements in the terrestrial environment do not provide any indication that tritium levels are significantly above the regional background. Tritium concentrations in groundwaters and in the river Rhone waters are at their background level too, with values in the range 0.94-1.64 Bq/l. In contrast, the various aquatic compartments of the river (fishes, plants, sediments) show enriched non-exchangeable bound tritium concentrations both upstream and downstream of the power plant, with values up to 14.7, 49 and 1495 Bq/kg (dry weight) respectively. Although fine particles of tritiated compounds entering in the composition of luminous paints have been suspected on several occasions, the nature and the origin of this tritium source, which is not related to the nuclear plant, remain unknown and will require further investigations.

411. Trapping of Adenovirus Vectors in Blood

In an attempt to circumvent the limitations of Adenovirus (Ad) vectors derived from group C serotype Ad5 we recently developed vectors based on group B serotype Ad11. These vectors are benefited by the low prevalence of Ad11-neutralizing antibodies in humans, and the CD46-dependent tropism of Ad11. CD46 is expressed at high levels in cell types including hematopoietic stem cells, dendritic cells and metastatic tumor cells. Following systemic intravenous delivery of an Ad5 vector, a chimeric Ad5 vector possessing the CD46 interacting Ad11 fiber (Ad5/11), and an Ad11 vector to CD46 transgenic mice we discovered that the kinetics of vector clearance from blood are different. Using real time quantitative PCR to detect viral genomes we found that the number of Ad11 vector genomes in mouse serum at 3 minutes post tail vein injection was 2 orders of magnitude lower than for Ad5 and Ad5/11 vectors, but at 15 and 120 minutes post injection the number of vector genomes was comparable between Ad5, Ad5/11 and Ad11. To investigate the differences between the numbers of vector genomes in serum at 3 minutes post injection the association of vector genomes with blood cells was also monitored by real time quantitative PCR at all time points. The number of vector genomes associated with blood cells was more than one order of magnitude higher for Ad11 than Ad5 or Ad5/11 at all time points tested with the highest difference seen at 3 minutes post injection (|[sim]|2 orders of magnitude higher). To study which type of blood cells associate with Ad11 vectors, CD46 transgenic mice were injected in the tail vein with 3H-[thymidine] labeled Ad vector. Individual cell types were separated from blood collected at 3 minutes post injection and the highest levels of tritium labeled Ad11 were associated with the platelet fraction. Subsequent analyses revealed that Ad5, Ad5/11 and Ad11 vectors associate with platelets within minutes after intravenous injection but that Ad11 vectors associate at higher levels. Electron microscopic analysis of platelets isolated 3 minutes after injection of Ad5, Ad5/11 or Ad11 vectors revealed that Ad particles were associated with the platelet surface and structures of the surface-connected canalicular system. We also noticed that Ad11 vectors associate with mononuclear cells more efficiently than Ad5/11 vectors. When taken together, the observations that Ad11 associates with platelets and mononuclear cells more efficiently than Ad5/11 suggests that capsid proteins other than fiber may mediate blood cell interactions. We are currently investigating the mechanism(s) by which Ad capsids and blood cells interact. The roles of the serotype specific (Ad5 or Ad11) capsid proteins hexon, penton and fiber in Ad/blood cell interactions will be presented. Our aim is to develop new Ad vectors that are not trapped in blood upon systemic intravascular administration.

Tritium along the French coast of the English Channel

Within the scope of a joint IRSN/EDF research program, it is possible to present a first status of free water tritium and organically bound tritium levels in the French coastal marine environment, from Concarneau to Gravelines. Seasonal sampling was conducted over two years, 2001 and 2002. The matrices selected for this specific survey include water, seaweed, molluscs, crustaceans and fish. The background concentration, estimated from the results obtained at two sites, Concarneau and Roscoff, remote from industrial sources, is close to the detection limit of 1,2 Bq.l -1 . Along the Channel coast and the entrance of the North Sea, tritium is released in seawater by four nuclear power plants (14 reactors) and mainly by the reprocessing plant of La Hague. The concentrations measured are in good agreement with activities calculated with the hydrodynamic model of dispersion TRANSMER. The results confirm a dilution factor of two between the north Cotentin area and the Straits of Dover for soluble radionuclides. The concentrations are in the range of 2 to 20 Bq.l -1 for free and organically bound tritium in biota. Although isotopic fractionation is theoretically expected to be slight, the available results indicate a ratio between tritium bound to organic matter and tritium in free water greater than one.

Mass Transfer Behavior of Tritium from Air to Water through the Water Surface

It is anticipated that a certain amount of tritiated water exists in the atmosphere of tritium handling facilities, and it is recognized that the hazardous potential of tritiated water is rather high. Then, it is important to grasp the behavior of tritiated water for preserving of the radiation safety. The mass transfer behavior of tritium from air to water through the water surface was discussed in this study. The evaporation rate of water and the condensation rate of water were experimentally examined from measurement of change of the weight of distilled water. The tritium transfer rate from the tritiated water in air to the distilled water was also experimentally examined by using a liquid scintillation counter. Experimental results about change of tritium level in a small beaker placed in the atmosphere with tritiated water showed that diffusion of tritium in water and gas flow in the atmosphere gives considerable effect on tritium transfer. The estimation method of the tritium transfer made in this study was applied to explain the data at The Japan Atomic Power Company second power station at Tsuruga and good agreement was obtained.

Tritium levels in Chinese cabbage and radish plants acutely exposed to HTO vapor at different growth stages

To simulate an acute exposure of Chinese cabbage and radish plants to airborne HTO, the potted plants were exposed to HTO vapor under semi-outdoor conditions for 1 h at different times from the early to late growth stages. The plants were grown outdoors and the plant tritium was measured at the end of an exposure ( h 0) and at harvest. The leaf tissue free water tritium (TFWT) concentrations at h 0 were considerably lower than estimated equilibrium concentrations. In the leaves of Chinese cabbage, the exposure at the earlier growth stage generally ended with a higher TFWT concentration. Such a tendency was not apparent either in the leaves or roots of radish. On the other hand, the earlier stage exposure gave rise to lower TFWT concentrations at the harvest of both crops. For the OBT (organically bound tritium), however, the same occurred only in the Chinese cabbage leaves. During the period between the exposure and harvest, the TFWT concentrations reduced by factors of up to 1.1 × 10 6 for the Chinese cabbage leaves and 1.3 × 10 4 for the radish roots. Based on the activity ratios of OBT to TFWT at harvest, it is estimated that OBT mostly contributes much more to the ingestion dose than TFWT does.

Rodents as receptor species at a tritium disposal site

New methods are being employed on the Department of Energy's Savannah River Site to deal with the disposal of tritium, including the irrigation of a hardwood/pine forest with tritiated water from an intercepted contaminant plume to reduce concentrations of tritium outcropping into Fourmile Branch, a tributary of the Savannah River. The use of this system has proven to be an effective means of tritium disposal. To evaluate the impact of this activity on terrestrial biota, rodent species were captured on the tritium disposal site and a control site during two trapping seasons in order to assess tritium exposure resulting from the forest irrigation. Control site mice had background levels of tritium, 0.02 Bq/mL, with disposal site mice having significantly higher tritium concentrations, mean = 34.86 Bq/mL. Whole body tritium concentrations of the mice captured at the disposal site were positively correlated with tritium application and negatively correlated with precipitation at the site.

Recharge mechanism and hydrochemistry evaluation of groundwater in the Nuaimeh area, Jordan, using environmental isotope techniques

The relationship between the stable isotopic and chemical composition of precipitation and groundwater was studied in the Nuaimeh area of the Ajloun Highlands in Jordan. The isotopic composition values of precipitation and groundwater are almost identical. The spatial variation of stable isotopes in precipitation is mainly due to the effect of seasonal temperature, altitude and amount. The groundwater reveals identical variation in isotopic composition to the precipitation due to direct recharge and the karstic nature of the outcropping Turonian aquifer. Tritium levels in wells are high and their content is similar to the weighted mean value of tritium content in precipitation, indicating local recharge and low residence time. The 14C activity in the tritiated groundwater is found to be about half of the 14C activity of precipitation in the region. A geochemical evolution through dissolution of carbonate by water–carbonate rock interactions reduced the atmospheric 14C activity from 114 to 61 pmc in the groundwater. A 14C of around 61 pmc and 7.6 TU values are considered the initial concentration for the recharge in the shallow carbonate aquifer in the Yarmouk Basin. The large fluctuation of water level in observation wells during the rainy season indicates the sensitivity and direct response of the aquifer to the recharge. The chemical composition of the groundwater (Ca2+–HCO3−) gives emphasis to the short duration of water–rock interaction and indicates dissolution of the carbonate aquifer. The elevated concentrations of Cl− and NO3− in groundwater are attributed to anthropogenic sources.

Evidence for nuclear emissions during acoustic cavitation revisited

This paper extends the experimental and numerical results presented previously and addresses the major criticisms raised. In addition, the most recent results are discussed. In acoustic cavitation experiments with chilled (ɛ0 °C) deuterated acetone (C3D6O), the production of tritium and 2.45 MeV neutrons [which are characteristic of deuterium-deuterium (D-D) fusion] was observed during vapour bubble implosions in an acoustic pressure field. Similar experiments with deuterated acetone at room temperature (ɛ20 °C) and control experiments with normal acetone (C3H6O), at both 0 and 20 °C, showed no statistically significant increases in either tritium level or neutron emissions. Numerical simulations of the processes that account for the shock waves generated in the liquid and within the collapsing bubbles supported these experimental observations and showed that high densities and temperatures (° 108 K) may be achieved during bubble cloud implosions, yielding the conditions required for D-D nuclear fusion reactions. The present paper treats the bubble fusion experiments and theoretical results in greater detail than was possible in the previous publications, contains some refinements, addresses some important questions raised by reviewers and critics and discusses possible applications of this interesting phenomenon.

Ground water discharge and nitrate flux to the Gulf of Mexico.

Ground water samples (37 to 186 m depth) from Baldwin County, Alabama, are used to define the hydrogeology of Gulf coastal aquifers and calculate the subsurface discharge of nutrients to the Gulf of Mexico. The ground water flow and nitrate flux have been determined by linking ground water concentrations to 3H/3He and 4He age dates. The middle aquifer (A2) is an active flow system characterized by postnuclear tritium levels, moderate vertical velocities, and high nitrate concentrations. Ground water discharge could be an unaccounted source for nutrients in the coastal oceans. The aquifers annually discharge 1.1 +/- 0.01 x 10(8) moles of nitrate to the Gulf of Mexico, or 50% and 0.8% of the annual contributions from the Mobile-Alabama River System and the Mississippi River System, respectively. In southern Baldwin County, south of Loxley, increasing reliance on ground water in the deeper A3 aquifer requires accurate estimates of safe ground water withdrawal. This aquifer, partially confined by Pliocene clay above and Pensacola Clay below, is tritium dead and contains elevated 4He concentrations with no nitrate and estimated ground water ages from 100 to 7000 years. The isotopic composition and concentration of natural gas diffusing from the Pensacola Clay into the A3 aquifer aids in defining the deep ground water discharge. The highest 4He and CH4 concentrations are found only in the deepest sample (Gulf State Park), indicating that ground water flow into the Gulf of Mexico suppresses the natural gas plume. Using the shape of the CH4-He plume and the accumulation of 4He rate (2.2 +/- 0.8 microcc/kg/1000 years), we estimate the natural submarine discharge and the replenishment rate for the A3 aquifer.

Low-level measurements of tritium in water

Using a liquid scintillation counter, an experimental procedure for measuring low-level activity concentrations of tritium in environmental water has been developed by our laboratory, using the electrolytic tritium enrichment. Additionally, some quality tests were applied in order to assure the goodness of the method. Well-known water samples collected in the Tagus River (West of Spain) and the Danube River (Bulgaria), both affected by nuclear plant releases, were analysed and results were compared to previous data. The analytical procedure was applied to drinking water samples from the public water supply of Seville and mineral waters from different springs in Spain in order to characterize its origin. Due to the very low levels of tritium in the analysed samples, some results were reported as lower than the minimum detectable activity concentration (MDA). However, the count rate of these measurements was over the background count rate of LS counter in all the cases. For that reason, an exhaustive discussion about the meaning of the MDA, using an experimental essay, was made in order to establish a rigorous criterion that leads to a reliable value in the case of low-level measurements.

If long fallow cropping is leaky then shallow groundwaters on the Liverpool Plains should be of recent origin

Previous groundwater studies have indicated that up to 195 000 ha of the Liverpool Plains catchment, south of Gunnedah, New South Wales, Australia, are at risk from shallow saline watertables. Replacement of hydraulically stable, native perennial grasslands with more ‘leaky’ annual cropping systems since the 1950s, particularly long fallow wheat–sorghum rotations, has been held responsible for an apparent increased frequency of shallow watertables and saline discharge. If so, then it follows that shallow groundwater in the alluvium will be recent (less than about 30 years old) and the solution to the problem is a straightforward reduction in deep drainage under farming systems via increased evapotranspiration. However, in this study, we have found levels of bomb pulse tritium in shallow groundwaters that indicate that about half of the shallow groundwaters in the Mooki subcatchment pre-date current agricultural practices. A hypothesis for this unexpected outcome suggests that the problem is complex and that solutions need to be site-specific.

Reconstructing tritium exposure using tree rings at Lawrence Berkeley National Laboratory, California.

Annual tritium exposures were reconstructed using tree cores from Pinus jeffreyi and Eucalyptus globulus near a tritiated water vapor release stack. Both tritium (3H) and carbon-14 (14C) from the wood were measured from milligram samples using accelerator mass spectrometry. Because the annual nature of the eucalyptus tree rings was in doubt, 14C measurements provided growth rates used to estimate the age for 3H determinations. A 30-yr comparison of organically bound tritium (OBT) levels to reported 3H release data is achieved using OBT measurements from three trees nearthe stack. The annual average 3H, determined from atmospheric water vapor monitoring stations, is comparable to the OBT in proximal trees. For situations without adequate historical monitoring data, this measurement-based historical assessment provides the only independent means of assessing exposure as compared to fate and transport models that require prior knowledge of environmental conditions and 3H discharge patterns.

Maintenance of the JET active gas handling system

The JET active gas handling system (AGHS) has been in operation in conjunction with the JET machine since Spring 1997. The tritium levels within the vessel have remained sufficiently high, 6.2 g at the end of the DTE1 experiment and currently 1.5 g, such that the AGHS has been required to operate continuously to detritiate gases liberated during D–D operations and to maintain discharges to the environment to ALARP. Maintaining the system to ensure continued operation has been a key factor in guaranteeing the continued availability of the essential sub-systems. The operational history of the JET AGHS has been previously documented in a number of papers [R. Lässer, et al. Proc. of the 19th SOFT Conf. 1 (1996) 227; R. Lässer, et al., Fusion Eng. Des. 46 (1999) 307; P.D. Brennan, et al., 18th Symp. on Fusion Eng., 1999]. Operational downtime is minimised through well-engineered sub-systems that use high integrity components. Outage, contamination and operator dosage are minimised through pre-planned and prepared maintenance operations. The reliability of sub-system critical condition fault detection is demonstrated through routine testing of hard-wired alarms and interlocks.

Blood tritium level as an estimate of soft tissue dose

To test the blood tritium level as an estimate of free water tritium (FWT) and organically bound tritium (OBT) in human soft tissues, a tritiated amino acid mixture (TAA) and tritiated water (HTO) were injected or orally administered to mice. Relatively high tritium retention in the blood was found after TAA injection. This observation was explained by a low rate of clearance of non-volatile tritium components. The dose estimated for the soft tissues after TAA injection was larger than that estimated on the basis of tritium concentration in urine by a factor of 1.8-2.3. In both HTO and TAA injections, the blood tritium level gave a conservative estimate of the dose to soft tissues including active bone marrow. The accumulated dose to soft tissues after oral administration tended to be lower than that for intraperitoneal injection.

Uncertainty assessment of environmental tritium measurements in water

The method most widely used nowadays to measure environmental tritium levels in water is electrolytic enrichment followed by liquid scintillation spectrometry. Although these techniques have been in use for many years, there is a gap in systematic analysis of the sources of uncertainty associated with this particular application. The paper presents a comprehensive assessment of the individual uncertainty components of the entire analytical process, starting from sample preparation to radioactivity measurement. Examples of the complete uncertainty budget for typical tritium levels in the analysed water samples are included. The relative importance of individual uncertainty components is given and possible ways of improving the overall quality of analyses are discussed.

Tritium distribution in JT-60U W-shaped divertor

Detailed tritium profiles on the JAERI Tokamak-60U (JT-60U) W-shaped divertor and the first wall tiles were examined by a tritium imaging plate technique (TIPT) and full combustion method. The highest tritium level (60 kBq/cm 2) was observed at the dome top tiles. The tritium level of the divertor target was lower (2 kBq/cm 2). The result of the triton deposition simulation using orbit following Monte-Carlo code was consistent with the tritium distribution obtained by TIPT and full combustion method. These results indicate that the tritium distribution of the JT-60U W-shaped divertor reflects mainly the distribution of the energetic triton impinging on the wall. According to the simulation, the tritium atoms produced by D–D nuclear reaction in JT-60U are not loosing completely their initial energy of 1 MeV and around 1/3 of them are implanted into the wall.

The use of isotopes to identify landfill gas effects on groundwater.

An evaluation of the source of volatile organic compounds in groundwater samples was performed at a landfill in southern California. The 3H (tritium) content of the water in leachate and water from the gas-collection system (condensed water and entrained water droplets) and the delta 13C and 14C content of the inorganic carbon in landfill gas CO2, leachate, and gas-collection system water were used to characterize the dissolved inorganic carbon (DIC) inside the landfill, while the same parameters were monitored in groundwater samples from affected monitoring wells and an unaffected well. Tritium levels from leachate and gas-collection system condensate ranged from approximately 2000 TU to over 4000 TU, orders of magnitude higher than unaffected groundwater. The average 14C content of DIC in the landfill pore-water samples was 121 pMC and the 14C content of unaffected groundwater DIC was 93 pMC, while the 14C content of the dissolved inorganic carbon in groundwater with VOC detections ranged from 105 to 119 pMC. The delta 13C of DIC in pore water was consistently above 0 per thousand and the delta 13C of unaffected groundwater DIC was -20.3 per thousand, while the delta 13C of DIC in affected groundwater samples was increased from -17.3 to -13.2 per thousand. The increases in both delta 13C and 14C in landfill gas-impacted groundwater DIC generally correlated with the number of volatile organic compounds detected and their concentrations. Based on the tritium and DIC 14C levels in leachate and water from the gas-collection system compared to those of unaffected water, significant increases in the tritium content of the water would be expected to accompany VOC detections and increases in delta 13C and 14C caused by landfill water. The results rule out landfill water as the VOC source, leaving landfill gas as the source. The identities and concentrations of the specific VOCs in affected groundwater samples varied among wells as well as between two leachate samples, ruling out the use of a VOC "fingerprint" for leachate or landfill gas to be compared to groundwater VOC concentrations.