Tritium activity

Tritium has also been observed in meteorites and material recovered from sateUites (see also Extraterrestrial materials). The tritium activity in meteorites can be reasonably well explained by the interaction of cosmic-ray particles and meteoritic material. The tritium contents of recovered sateUite materials have not in general agreed with predictions based on cosmic-ray exposure. Eor observations higher than those predicted (Discoverer XVII and sateUites), a theory of exposure to incident tritium flux in solar flares has been proposed. Eor observations lower than predicted (Sputnik 4), the suggested explanation is a diffusive loss of tritium during heating up on reentry. 

To calculate the tritium activity in an analyzed sample, the count rate in the blank sample - the background - first is subtracted from the gross... 

Step 6. Prepare a tritium comparison solution from a tritium standard solution of known tritium activity. Pipette 10 mL of the diluted solution into a 20-mL... 

If the unsaturated zone is composed of relatively fine sediment (silt and fine sands) a quasi-uniform seepage flow can be assumed for the unsaturated zone in humid climate zones over long time spans. Therefore, the transport of infiltration water can be simulated in PHREEQC as a monotonous movement in accordance with the "piston flow model. A constant flow of infiltration water of 0.5 m per year is assumed for the following simulation. Furthermore, it is considered simplistically that the infiltrating precipitation has a tritium activity of 2000 TU (tritium units) over a period of 10 years. Then, it is assumed that the tritium activity decreases to zero again. 

If pure Li is used as the breeder-moderator, -Ti and a number of other materials can be used, as discussed for the Cauldron Blanket Module. However, the tritium activity in Li drops markedly in the absence of Pb, and the blanket temperature will need to be raised to alleviate the tritium removal problem. 

Tritium activity (Ci) Temperature Scavenger ro C-C3H6 CjHs Propene Ethylene... 

This laboratory reports tritium activities with their total expanded uncertainties (Table 3). The biggest contribution is from the furnace recovery which is 5%. Over 70 standard measurements were used for this. The average value for the furnace recovery is 95 5%. A value of 5.6% expanded uncertainty is used for the final calculation in order to estimate the total expended uncertainty. Standard runs are performed after every five sample runs and the acceptable furnace recovery range is between 80 - 100%. If the furnace recoveries are out of... 

Pointurier, F., N. Baglan, and G. Alanic (2004) A method for the determination of low-level organic-bound tritium activities in environmental samples. Applied Radiation and Isotopes. 61,293-298. 

Preliminary indications are that tritium activity may be predicted from the natural lithium concentration alone and no evidence was observed of significant tritium diffusion into or out of steel activated in a Magnox reactor. 

Data for total tritium activity concentrations in Orchard Ledges mud, obtained by independent sampling in the vicinity of the GE Healthcare pic radiopharmaceutical plant at Cardiff, is provided in Table 2. 

Tritium has a half-life of about 12.3 years, which makes it useful for dating objects up to about 100 years old. Tritium dating is sometimes used to verify the dates of aged alcoholic beverages like wines. How old is a bottle of wine if its tritium activity is 12.5 percent as high as that of new wine ... 

Figure 11.11. Example of competitive experiments used by Saunders et al. [89, 97] to measure isotope effects for mixed-isotope exponent determinations. The primary and secondary isotope effects were determined using the starting tritium activities of the bromide substrate, the product styrene, and the solvent ethanol, all at a kno A/n fractional...

At such low concentrations the lithium and boron are exposed homogenously to the neutron flux. Because of the large thermal-neutron cross sections for Ii and °B, these isotopes are depleted significantly during the typical fuel irradiation time of 4 years. Therefore, to calculate the tritium activity (iVX) - in a fuel element after an irradiation time, we rewrite Eq. (2.100), recognizing that the chain-linking term here is 0o instead of X. For the Li reaction of Eq. (8.47),... 

Enoate reductase exclusively splits off the (4S)-hydrogen atom from NADH. There is no direct hydrogen transfer from NADH to the products. If (45)-[ H]-labelled NADH with a total tritium activity of 4.67.10 decays per minute was dehydrogenated with an excess of enoate, the isolated product showed a tritium content of less than 0.005 % of that of the NADH. Almost all the tritium was in the water. In the absence of an enoate as acceptor, the tritium exchange from (45)-[4- H]-NADH catalysed by enoate reductase is very slow. Depending on the substrate concentration, the isotope effect of the reduction of ( )-2-methyl-2-butenoate with (4S)-[4- H]-NADH varies from 6.8 to 1.3. The presence of NAD" decreases the isotope effect (17). 

Figure 6. Atmospheric concentrations as functions of the radiogenic noble gases Ar, Kr, and Kr and of the man made traces gases CFC-11, CFC-12, and SFe. Concentrations are normalized to the respective atmospheric abundances in 1998. In addition a typical (input) curve of in precipitation is shown. Note, nuclear bomb tests in the atmosphere increased the global tritium inventory by up a factor of 1000. Since then concentrations steadily decreased, but still today tritium activity in young meteoric waters is commonly one order of magnitude larger than the natural background due to cosmic rays production.

The curie (Ci) is a commoniy used unit for measuring nuciear radioactivity 1 curie of radiation is equai to 3.7 X 10 decay events per second (the number of decay events from 1 g radium ini s). A1.7-mL sampie of water containing tritium was injected into a 150-ib person. The totai activity of radiation injected was 86.5 mCi. After some time to aiiow the tritium activity to equaiiy distribute throughout the body, a sampie of biood piasma containing 2.0 mL water at an activity of 3.6 piCi was removed. From these data, caicuiate the mass percent of water in this 150-ib person. 

Water vapor in air is collected on these sorption media at measured flow rates and then removed from the sorbent by distillation. The tritium activity is reported relative to the amount of water. Collection of various gaseous forms of tritium, and radioiodine is discussed in Section 5.3.2. 

Water quality Determination of tritium activity concentration (Liquid scintillation counting method)... 

Radiochemical yields of a tritiated species are usually given as the percentage of the total tritium activity produced which is found in the particular compound. Labeling of the parent can vary from 0-1% to as high as 50%. 

Henchman and Wolfgang (1961) studied optically active 2-butanol in the gas phase and found 94% 3% retention of configuration at the asymmetric carbon atom. The optical activity was related to the activity at the 2-carbon by making use of specificity of the Oppenauer oxidation in determining the tritium activity at the 2-carbon in the alcohol. 

The use of U nitride fuel and boron control rods in LCFR (BREST concept) will cause tritium formation as a result of triple fission on N-14 and B-10 nuclei. Tritium activity may reach 2.6-10 Bq/day, that is rather high value. Because of its penetration into the secondary circuit through SG tube walls, tritium release into the environment is possible. These assessments are thought to be performed not only by calculations but also using experimental studies. 

Ring closure probably occurs through cyclohexadiene , but the elucidation of the exact mechanism of ring closure needs further isotope studies. The initial steps, that is the dissociative adsorption in the dehydrogenation of cyclohexane and in the D/H exchange reactions taking place between cyclohexane and deuterium on metal surfaces, are similar Cyclohexane, cyclohexene and benzene have been found to contain tritium activity when a catalyst covered with tritium has been used in the dehydrocyclization experiments. No hexane —> cyclohexane reaction occurs. 

The effects of increased water-scintillator ratios on THO exchange in air exposed vessels and film tv >es was examined using toluene and a xylene derivative based scintillator. Percent water of the samples was increased from 0.5 percent to 55 percent water which is within the range of sol-gel scintillator capability (Benson 1976). Total volume (scintillator plus water) was maintained constant as was the total tritium activity. All samples were shaken for 30 seconds prior to counting. 

The decreased activity within the film tubes is due to physical diffusion of tritium out of the tube and not changes in efficiency from scintillator permeation of the tube wall (figure 2). Unspiked tubes progressively increase in tritium activity during incubation with spiked tubes. 

Experiments Designed to Determine the Effect of Triton Concentration on the Count Rate. To scintillator solutions of low concentrations of Triton X-100 (3-160mM), containing 7g/l PPO and 0.35g/l DMPOPOP, 0 to 2 Vol % H2O were added. The tritium activity was added in form of 10 yl H—H2O or H— toluene. 

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