Tritium water standard

Dissolved compounds. In an ideal situation the one-time investigation should address the entire list of drinking water standards. In any case, the analyzed ions should include the major ions (Na, K, Ca, Mg, Cl, HC03, S04, N03, Br) dissolved oxygen, C02, and methane isotopic composition (e.g., deuterium, lsO, 13C) and age indicators (e.g., tritium, 14C, 36C1 and 4He the last should be included for waters that are estimated to be old). 

Tritiated-water standards have been distributed by the National Bureau of Standard (NBS), USA, and IAEA, meeting the demands from laboratories measuring the natural tritium. 

All tritium measurements were performed using a 1220 liquid scintillation counter (Wallac Quantulus ). 8ml of aqueous sample were mixed with 12ml Gold Star (Meridian) scintillation cocktail in a 22ml polythene vial. The counter was routinely calibrated for using a traceable tritiated water standard. In this paper, all uncertainties are quoted at the 90% confidence level except for RO water. 

These constituents include beta activity and concentrations of Sr, tritium, nitrate, and sulfate. Beta and Sr activities exceeded drinking water standards in the same 10 wells. Tritium activities were greater than the standard in eight wells, and nitrate was exceeded in one well. Sulfate was higher than secondary drinking water standards in seven wells (DOE-RL 1991). 

The EPA s proposed drinking water standards for beta and photon emitters are limited to exposure of 4 mRem EDE/year (EDE, effective dose equivalent). Levels of strontium and tritium are determined by this method. The strontium method [15] covers the measurement of total strontium, including °Sr and Sr. Interferences from calcium and other radionuclides are removed by one or more precipitations of the strontium carrier as strontium nitrate. Barium and radium are removed as chromate. The daughter of °Sr is removed by a hydroxide precipitation step, and the separated combined Sr and Sr are counted for beta-particle activity. Tritium is determined by liquid scintillation counting after distillation [16]. 

When specifically labelled compounds are required, direct chemical synthesis may be necessary. The standard techniques of preparative chemistry are used, suitably modified for small-scale work with radioactive materials. The starting material is tritium gas which can be obtained at greater than 98% isotopic abundance. Tritiated water can be made either by catalytic oxidation over palladium or by reduction of a metal oxide ... 

Beezhold and Stout [68] studied the effect of using mixed standards on the determination of PCBs. Mixtures of Arochlors 1254 and 1260 were used as comparison standards and gas chromatograms of these mixtures were compared with those obtained from a hexane extract of the sample after clean-up on a Florasil column. Polychlorinated biphenyls were separated from DDT and its analogues on a silica gel column activated for 17h and with 2% (w/w) of water added. The extracts were analysed on a silanised glass column packed with 5% DC-200 and 7.5% QF-1 on Gas Chrom Q (80-100 mesh) operated at 195°C with nitrogen as carrier gas (50-60mL min-1) and a tritium detector. 

An aliquot of the distilled and condensed tritium-containing water sample is prepared for LS counting by adding it to an LS cocktail in a counting vial. Also counted in the same batch are two other vials with scintillation cocktail, one with a standard tritium solution, and the other with a blank water solution. 

The sample is purified by distillation to separate the tritium-containing water from both non-radioactive and radioactive impurities. Various substances can cause scintillations by means other than radionuclide emission - by chemical fluorescence or luminescence - or interfere with ( quench ) detection of scintillations due to radionuclides. Even after purification, both processes are inevitable, but to a limited extent. Luminescence due to visible light will decay when the sample is stored in a darkened region of the LS system before the sample is counted. The degree of quenching, notably due to water in the sample, is determined instrumentally by reference to comparison sources and recorded, so that any deviation from the quenching observed for the tritium standard can be taken into account. 

A water sample is brought into a laboratory for tritium analysis. Three separate fractions of 250 mL each are removed from the 1-gallon container, distilled separately. A 10 mL portion is taken for counting as was done in this experiment. The results were 130 Bq/L, 52 Bq/L and 110 Bq/L. Calculate the average and standard deviation of the mean. What might contribute to the spread in the results Explain. 

The data are expressed as TR (Tritium Ratio 1 TR corresponds to a H/H ratio of 10 or to an activity concentration of 0.118 Bq/kg water). The data are expressed as percent modem carbon (pmc 100 pmc corresponds to 95% of the NBS oxalic acid standard or to an activity concentration of 0.226 Bq/g C). The and data are expressed as deviations(8-values) relative to SMOW (Standard Mean Ocean Water). The data are expressed as deviations relative to PDB (Pee Dee Belemnite) standard. The data are expressed as /qo deviations relative to CDT (Canion Diablo Troilite) standard. 

D19.04 D4107-91 Standard Test Method for Tritium in Drinking Water... 

The tritium analysis case was further evaluated in accordance with Method IV by preparing a tap mter saiq>le (from well water) with a tritium standard so the resulting concentration was equal to the required LLD (lE-5 iCi/mL). The sanq>le has been analyzed a total of twenty-six times under the standard protocol with the following results s 1.06jK0.06B-5 pCi/mL. Bach sample... 

Tritiated water (O.lSyc in 50X ) was added to vials and film tubes containing various scintillation solutions. The vials and tubes were then tightly capped and heat sealed, respectively, and placed in a standard cardboard 20 ml vial tray which in turn was placed in a ventilated fume hood. The samples were removed in groups of not more than 30 and counted to 0.5% error and returned to the hood. The half-time for THO loss was determined from the standard decay equation. The quadruplicate samples were not corrected for tritium decay. 

The measurement of low-level tritium concentrations in discrete environmental water samples has been routinely accomplished by applying standard liquid scintillation counting techniques directly to a small aliquot of the original sanple or to a portion of the sample which has been pretreated. Two of the more common sample preparation methods are simple distillation at atmospheric pressure and electrolytic enrichment with a subsequent increase in the tritium content of the sample. 

As indicated in the reaction sequences of equation 1, fractionation of the tritium does occur between the calciiom hydroxide and acetylene formed as products of the initial reaction of the water sample with the calcium carbide. However, the isotopic effect was found by Hohndorf and Oro (14) to be constant at 31.4 1.2 percent, thus indicating that the isotope fraction is independent of chemical yield for the reaction. For the system under consideration, the production of a constant volume of benzene was not attainable due to the restrictions of varying sample size, changes in the efficiency of trimerization due to catalyst depletion from previous samples, and the potential for varying rate of reaction of the water-carbide system. This fact, coupled with the lack of adequately documented tritiated benzene standards, led to the adoption of a system calibration rather than a yield determination for each sample in conjunction with a separate instrument calibration. 

The new liquid scintillation counting method is a double isotope, external standard count procedure which eliminates the background by measuring tritium free water samples and applying a difference methods. The computer program developed for this method calculates from the count rates measured in two channels (tritium and carbon-14 channels) and the external standard count rates the concentration of tritium in the samples together with the associated statistical error. 

The most delicate part of the method developed to measure environmental tritium levels is the elimination of the background. A difference method has been applied for this purpose using "dead water" samples, i.e. tritium free water samples obtained from National Bureau of Standards. 

The environmental and dead water samples exhibit quenching characteristics falling into the range of 0.5 - 0.6 quenched standards (Packard Instrument Co.) for tritium and carbon-14. During each cycle an efficiency calibration using the quenched standards is made. A cycle consists of counting the 15 sample vials, 2 or more vials of dead water, and the 4 quenched standards (two carbon-14 and two tritium standards). The selected count period is 20 minutes. 

The errors associated with estimating the efficiencies in each channel are much smaller than the errors associated with the count rates in each channel. Therefore, the errors of the efficiencies are neglected. It is assumed that the tritium content of the dead water is zero (National Bureau of Standards certifies that it is less than. 6 pCi/1). 

Tritium in water samples is determined with a liquid scintillation spectrometer because of its low maximum S-particle energy (18 keV). Water samples are distilled to remove nonvolatile components whose presence could lead to extinction during the scintillation detection and could also be radioactive. The sample is distilled to dryness in order that the tritium present can be transferred quantitatively into the distillate. A portion of the distillate is mixed with the liquid scintillator, and the radioactivity is measured by a liquid scintillation spectrometer. A standard tritium sample and a sample for measuring the background are prepared in a similar way. 

H] T-2 toxin was prepared by the Wilzbach method (New England Nuclear, Boston, MA). The crude product was dissolved in acetone water (1 1) and allowed to stand for several hours. All labile tritium was removed with a rotary evaporator. The residue was dissolved in benzene and was applied to a column of silica gel 60 (14.5 X 1.5 cm, 70-230 mesh, BDH Chemicals, Toronto, Ont.) which was developed with 100 ml benzene followed by 300 ml benzene acetone (3 1). Five ml fractions were collected and a small portion of each was applied to a TLC silica gel GF plate (Fisher Scientific Co., Toronto, Ont.) which was developed in benzene acetone (63 37). Fractions containing T-2 toxin were identified by comparison with known standards. The toxin was then recrystallized by the method of Bamburg et al. (1968). Specific activity of [%] T-2 toxin was determined to be 0.172 mCi/mg with the concentration of T-2 toxin measured by gas chromatography (Mirocha et al., 1976). The in vitro method of Chi et al. (1978) was used to test for possible % exchange under acidic conditions similar to those of the stomach. 

Samples of pasture, milk and other foodstuffs and water should be collected and measurements should be made to assess the exposure of the population and for the purposes of the implementation of interventions such as the restriction of foodstuffs. Milk is especially important in the event of a reactor accident or criticality accident because of the associated releases of radioiodines. Recommended intervention levels for radionuclides in foodstuffs are provided in the Basic Safety Standards [2], If it is suspected that releases of tritium have occurred, measurements of tritium in pasture vegetation should be made. 

Comparison of commercially available rosette samplers (Table 1-2, Fig. 1-5) shows that different constructions follow almost the same principle. A circular protective frame accommodates 3-36 samplers which commonly can be used as serial samplers in hydrocasts. In addition to their usage in basic hydrochemical studies, standard rosette samplers (e.g., 12 L Niskin samplers see Table 1-2) are also suitable for the collection of oceanographic tracers such as fluorocarbon compounds, helium-3, tritium or even carbon-14 (except for studies in the deep waters of the Pacific and Indian Oceans, where large special samplers of > 250 L volume are needed see Table 1-2 and Oiapter 13). 

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