**1. Introduction**

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Tritium is an isotope of hydrogen which emit beta particles in energy range of 5 – 18,6 keV, and has relatively long half life of 12.3 years. In the environment, tiritum is originated both from the nature and human activities. Naturally, tritium is produced in the atmosphere by interaction of cosmic rays with the nuclei of atoms present in the air, and estimated to contribute the annual effective dose equivalent about 0.01 μSv (United Nation, 1988). The other natural sources of tritium are nuclear reactions in earth's crust and environmental materials.

The sources of tritium in the environment relating to human activities, includes atmospheric nuclear testing, continuous tritium release from nuclear reactor under normal operation or accident, and incidental release from consumer products such as paint, watch materials, and other fluoresence goods (Glastone & Jordan, 1980; Puhankainen & Heikkinen, 2007). The food, drink and the use of such products can cause tritium contamination to the human body (Konig, 1990) and contribute the internal radiation doses to the tissues since tritium is distributed to the whole body (Trivedi et al., 2000).

As tritium in the environment possibly contaminates human, the measurement of tritium content in environmental materials as well as in human body samples is needed to be conducted to evaluate the tritium β radiation doses probably received by the body. Unfortunately, β radiation from tritium is not so simple to be determined without sample preparation for separating tritium from the sample bulk. Since tritium is a hydrogen isotope, it is possible to take tritium out from the samples as tritiated water molecule lead to an easy measurement using liquid scintillation counting (LSC) method.

Distillation technique has been choosen as a simplest technique to be used in tritium separation from the environmental samples. Some distillation techniques have been developed to take the tritium out from various environmental material including air, water, soil, plants, and biological materials such as human urine.

This chapter describes the developed distillation technique applied in environmental tritium analysis. The performance of the developed distillation techniques in tritium separation from the environmental samples are discussed based on the experimental test.

The Separation of Tritium Radionuclide from

**1.2.2 Sample measurement for tritium** 

environmental tritium analysis.

**2.1 Separation of tritium from air** 

et al, 1995).

Environmental Samples by Distillation Technique 269

The tritium in the environmental and human body samples are measured using liquid scintillation technique after it is prepared according to its chemical form. In this technique the tritium in the water molecule form is mixed with a liquid detector called scintillator to detect the emitted β particle, and then measured using Liquid Scintillation Counter device. In this measurement, β particle from tritium interact with the molecule of the liquid detector and produce photon emission which then is detected by a photo multiplier tube in the device. In order to obtain good measurement result it is important to prepare the environmental sample in the form of clear and colorless liquid (Rusconi et al., 2006; Hariharan & Mishra, 2000). Therefore, the sample distillation is an important step in the

Two mL of liquid from prepared environmental sample is added to 13 mL scintillator (as liquid detector) in a 20 mL scintillation vial. The mixture is shaked vigorously and kept in the dark and cool storage for 24 hours to obtain the stable mixture. The tritium content in

The measurement of tritium in the atmosphere is begun with air sampling where the solid absorbent such as silica gel and molecular sieve generally used to collect air sample. The silica gel is an oxide silicate having bee nest like structure, porous, and has very wide surface (Patton et al, 1995). Each gram of silica gel has great affinity toward water molecule, so it is very effective for water absorption. Generally, the silica gel contains blue cobalt salt as an indicator of water content that can exhibit color change from blue to pink after absorbing water or water vapor. The disadvantage of silica gel use in atmospheric tritium sampling is the bond of tritiated water to silica gel grain that is take place in the surface of the grain causing an easy evaporation if it is used in high temperature environment (Patton

The other solid absorbent can be used for atmospheric tritium sampling is molecular sieve that made of aluminosilicate (zeolite). The aluminosilicate is a chelat compound that can absorb the chemical substances both organic and inorganic as well as water molecule to the cavity of its molecular structure (Iida et al., 1995). The cavity of molecular sieve structure

The sampling apparatus for tritiated water vapor collection is composed of a sucking pump, a quartz tube of 0.80 m length and 0.05 m diameter, and a water bubler bottle installed at the end of the circuit to confirm the air flow (Figure 1). The atmospheric air is drawn by the pump with low flow rate of about 15 L/h and flown to the tube packed with the silica gel or molecular sieve pelet. Sampling is conducted for about 15 h, the time when the 50 g packed

The tritium water vapor absorbed in the solid absorbent is then recovered by developed distillation technique using an apparatus shown in Figure 2. The distillation apparatus is composed of nitrogen gas source, a tube furnace, and a condensation system. The condensation system consists of two condensation tubes that placed in a serial arrangement

have various sizes such as 3Å (MS3A), 4Å (MS4A), 5Å (MS5A) and 10Å (MS13X).

absorbent has been saturated absorbing the tritiated water vapor.

the environmental samples is measured using LSC for 1 hour.

**2. Separation of tritium from the environmental samples** 

#### **1.1 Environmental tritium**

The majority of tritium in the environment, both naturally and anthropogenic, is present in the form of water molecule (named HTO), while the others are gas (named HT and CH3T) and organic molecules. As an isotope of hydrogen, tritium can easily enter various environmental materials containing hydrogen. In the environmental component tritium is bonded to water molecule, called free-water tritium (FWT) and also to the organic compound as organically bound tritium (OBT).

Tritium in the environmental material is possible to contaminate human body through the food chain. The drinking water, food, inhaled air, and skin absorption are the main sources of tritium for human body contamination. Tritium is uniformly distributed in the body liquid 2 until 4 hours after its inhalation, ingestion or absorption through the skin (Taylor, 2003). At the same time, some percents of tritium atoms reversibly replaced H in OH, NH and SH bonds of organic molecules in the body, while about 1% of the activity is incorporated into stable CH bonds. The physical and chemical properties of tritium are almost the same as that of hydrogen.

The biological half times of tritiated water (HTO) are 10 days (97%) and 40 days (3%), whereas for OBT are 10 days (50%) and 40 days (50%) (ICRP, 1997 & Taylor, 2003). A major part (>90%) of an OBT intake is oxidized and excreted as HTO, this tritium is called the exchangeable tritium fraction. The nonexchangeably bound tritium fraction is normally released only as a result of enzymatic breakdown of the molecules containing this carbontritium bound. The HTO is excreted in urine, feces, sweat, and breath in which about a half is excreted via urine.

The tritium toxicity in the human body is contributed by β particle emitted by tritium bonded in biochemical structure of the cells that leads to genetic mutation and oncogenic effect of the long live cells. Such as it was described previously, the existence of tritium in the environment possibly lead to the internally radiation effect to human body. Therefore, the existence of tritium in the environment should be monitored. The environmental tritium monitoring generally is carried out by taking environmental materials samples, such as air, water, soil, and plants for measurement using liquid scintillation technique.

#### **1.2 Tritium analysis of environmental samples**

### **1.2.1 Sample preparation**

The tritium concentration in the water fraction as well as in the organic fraction of the sample is measured in the form of water molecule. Hence the sample preparation is needed in order to isolate the tritium from the samples bulk and convert to liquid form to be possible for LSC measurement. Distillation is one suitable technique to be applied in that purpose.

The sample is heated and the vapor is condensed to obtain the liquid form of free water tritium. In the case of OBT the sample needs to be combusted and the vapor released is condensed at low temperature (Tjahaja et al., 2004). Some modifications in distillation technique have been developed to facilitate the tritium samples preparation such as described in the following sections.

### **1.2.2 Sample measurement for tritium**

268 Distillation – Advances from Modeling to Applications

The majority of tritium in the environment, both naturally and anthropogenic, is present in the form of water molecule (named HTO), while the others are gas (named HT and CH3T) and organic molecules. As an isotope of hydrogen, tritium can easily enter various environmental materials containing hydrogen. In the environmental component tritium is bonded to water molecule, called free-water tritium (FWT) and also to the organic

Tritium in the environmental material is possible to contaminate human body through the food chain. The drinking water, food, inhaled air, and skin absorption are the main sources of tritium for human body contamination. Tritium is uniformly distributed in the body liquid 2 until 4 hours after its inhalation, ingestion or absorption through the skin (Taylor, 2003). At the same time, some percents of tritium atoms reversibly replaced H in OH, NH and SH bonds of organic molecules in the body, while about 1% of the activity is incorporated into stable CH bonds. The physical and chemical properties of tritium are

The biological half times of tritiated water (HTO) are 10 days (97%) and 40 days (3%), whereas for OBT are 10 days (50%) and 40 days (50%) (ICRP, 1997 & Taylor, 2003). A major part (>90%) of an OBT intake is oxidized and excreted as HTO, this tritium is called the exchangeable tritium fraction. The nonexchangeably bound tritium fraction is normally released only as a result of enzymatic breakdown of the molecules containing this carbontritium bound. The HTO is excreted in urine, feces, sweat, and breath in which about a half

The tritium toxicity in the human body is contributed by β particle emitted by tritium bonded in biochemical structure of the cells that leads to genetic mutation and oncogenic effect of the long live cells. Such as it was described previously, the existence of tritium in the environment possibly lead to the internally radiation effect to human body. Therefore, the existence of tritium in the environment should be monitored. The environmental tritium monitoring generally is carried out by taking environmental materials samples, such as air,

The tritium concentration in the water fraction as well as in the organic fraction of the sample is measured in the form of water molecule. Hence the sample preparation is needed in order to isolate the tritium from the samples bulk and convert to liquid form to be possible for LSC measurement. Distillation is one suitable technique to be applied in that

The sample is heated and the vapor is condensed to obtain the liquid form of free water tritium. In the case of OBT the sample needs to be combusted and the vapor released is condensed at low temperature (Tjahaja et al., 2004). Some modifications in distillation technique have been developed to facilitate the tritium samples preparation such as

water, soil, and plants for measurement using liquid scintillation technique.

**1.2 Tritium analysis of environmental samples** 

**1.1 Environmental tritium** 

compound as organically bound tritium (OBT).

almost the same as that of hydrogen.

is excreted via urine.

**1.2.1 Sample preparation** 

described in the following sections.

purpose.

The tritium in the environmental and human body samples are measured using liquid scintillation technique after it is prepared according to its chemical form. In this technique the tritium in the water molecule form is mixed with a liquid detector called scintillator to detect the emitted β particle, and then measured using Liquid Scintillation Counter device. In this measurement, β particle from tritium interact with the molecule of the liquid detector and produce photon emission which then is detected by a photo multiplier tube in the device. In order to obtain good measurement result it is important to prepare the environmental sample in the form of clear and colorless liquid (Rusconi et al., 2006; Hariharan & Mishra, 2000). Therefore, the sample distillation is an important step in the environmental tritium analysis.

Two mL of liquid from prepared environmental sample is added to 13 mL scintillator (as liquid detector) in a 20 mL scintillation vial. The mixture is shaked vigorously and kept in the dark and cool storage for 24 hours to obtain the stable mixture. The tritium content in the environmental samples is measured using LSC for 1 hour.
