Tritium organically bound

Trivedi, A., Galeriu, D., Richardson, R. B., Dose contribution from metabolized organically bound tritium after acute tritiated water intakes in humans, Health Physics 1997, 73, 579-586. 

In 1979/1980, Sweet Murphy (1984) made a survey of tritium in pine needle litter in the Savannah River locality. Water and HTO were extracted by freeze-drying, and organically bound T was estimated following combustion of the dried needles. The HTO content of the atmospheric water vapour was also measured. Figure 4.5 shows Sweet Murphy s results converted from pCi per ml of water to TU. All three variables declined approximately in proportion to distance from the plant, as would be expected for long-term releases. By extrapolation, T in atmospheric water vapour would fall to background (about 13 TU -Fig. 4.2) at a distance of 100 km. 

The activity had accumulated over a number of years, and the organically bound tritium, having a long biological half-life, accounted for most of the tritium in the pine needle litter. Sweet Murphy found evidence of direct conversions of HT to organically bound tritium in pine needles. The HTO in the needles, and probably most of the HTO in the air in the locality, derived from oxidation of HT in the soil. 

About 300 kg of sewage sludge pellets were collected from the Cardiff East sewage works in late 2004. An initial analysis of the tritium content showed an average concentration of 87 kBq kg of total tritium. Nearly all of the activity was in an organically bound form. 

The trap solution from the lower temperature is defined as containing the aqueous tritium from the sample and that from the higher temperature the organically bound tritium (OBT). 

The size of the lysimeters was sufficient for soil cores to be taken just before the harvesting of crops. Concentrations of tritiated water and OBT were determined at different depths in the soil. The results summarised in Table 3, showed that the organically bound tritium remained largely in the upper layer which represents the depth of tillage. The concentration of aqueous tritium was low and often below detection limits. However, where measurable values were obtained, concentrations were relatively uniform with depth. 

Harms, A.V. and S.M. Jerome (2004) Development of an organically bound tritium standard. Applied Radiation and Isotopes, 61, 389-393. 

Ware, A. and R.W. Allott (1999) Review of methods for the analysis of total tritium and organically bound tritium. National Compliance and Assessment Service Lancaster. 

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. 

Tritium collection. Tritium in air is usually in the form of water vapor and less commonly in the elemental or organic-bound forms. It is generated in nature by cosmic-ray interactions, and at nuclear reactors and tritium-production facilities by ternary fission and neutron activation. Tritium as HT tends to oxidize to water vapor in air. Conversion to and from organic-bound tritium occurs in biota (NCRP 1979). 

Special systems are used to collect separately the tritiated hydrogen gas (HT) and organic-bound tritium from air. A two-component collection train consists of a molecular sieve column, followed by addition of a stream of H2 carrier gas to the sampled air before it passes through a palladium-coated molecular sieve column. The flrst column collects tritiated water and the second column collects the two other forms (Ostlund and Mason 1985). The two columns are treated separately at the laboratory, as discussed in Section 6.2.2, to provide the three forms for separate analyses. 

The other two forms of tritium gas usually are submitted on a palladium-coated molecular sieve collector. Any HT is converted to HTO by palladium-catalyzed oxidation in the collector the water is removed by heating it above its boiling point and condensing the vapor. The sorbent with the remaining organical-bound tritium is mixed with a Hopcalite catalyst and heated to 550°C to oxidize organic gases to water, which is distilled and condensed (Ostlund and Mason 1985). 

For example, HT released from a plant is rapidly oxidized to HTO. Tritium water may be incorporated in organic matter as organically bound tritium (OBT) within tissues. The specific radioactivity of tritium in the form of CH3T in the atmosphere is very high, hut the reason is not understood. C may be released to the atmosphere as CO, CO2, CH4, HCHO, and COS. C02 released becomes incorporated into crops via photosynthesis leading to enhanced levels of C in crops. 

For inhalation of gases and vapours, the AMAD does not apply for this form. FITO — tritiated water OBT — organically bound tritium. 

In the organic molecules we have considered, radioactive tritium atom is directly bound to the carbon atom. The proximity of the obtained values of probabilities for the organic molecules shows that the nature of excitation does not depend on the group of atoms (CH2 or CH3) to which the tritium atom belongs, or on the degree of saturation of molecular bonds, or on the size of the molecule. This allows us to conclude that the character of molecular excitations induced by the / decay of tritium is affected mainly by the atom to which tritium is directly bound. 

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