Levels of tritium concentration in the environmental samples around JAERI TOKAI

By the operation of research reactors, tritium-handling facilities, nuclear power plants, and a reprocessing facility around JAERI TOKAI, tritium is released into the environment in compliance with the regulatory standards.To investigate the levels of tritium concentration in environmental samples around JAERI, rain, air (vapor and hydrogen gas), and tissue-free water of pine needles were measured and analyzed from 1984 to 1993. Sampling locations were determined by taking into consideration wind direction, distance from nuclear facilities, and population distribution. The NAKA site (about 6 km west-northwest from the TOKAI site) was also selected as a reference point.Rain and tissue-free water of pine needles were sampled monthly. For air samples, sampling was carried out for two weeks by using the continuous tritium sampler. After the pretreatment of samples, tritium concentrations were measured by a low background liquid scintillation counter (detection limit is 0.8 Bq/l).Annual mean tritium concentrations in rain observed at six points for 10 years was 0.8 to 8.9 Bq/l, which decreased with distance from the nuclear facilities. Tritium concentrations in rain obtained at Chiba City were around 0.8 Bq/l (1987–1988) and those at the NAKA site were 0.8 to 3.8 Bq/l.Annual mean HTO concentrations in air at three points for 10 years were 9.2×10^–2 to 1.1 Bq/m³, although HT concentrations in air, ranging from 1.7×10^–2 to 5.8×10^–2 Bq/m³, were not influenced by the operation of the nuclear facilities.Annual mean tritium concentrations in tissue-free water of pine needles at four points for 10 years were 1.4 to 31 Bq/l. Those at the NAKA site ranging from 1.4 to 6.2 Bq/l were in good agreement with the reported value by Takashima of 0.78 to 3.0 Bq/l at twenty-one locations in Japan.Monthly mean HTO concentrations in air for 10 years showed a good correlation with absolute humidity, while other samples showed no seasonal variation.Higher level tritium concentrations in rain, in air (vapor), and in tissue-free water of pine needles at the TOKAI site were caused by the tritium released from the nuclear facilities.The committed effective dose equivalent to the member of general public, estimated using the maximum tritium concentration in air (1.1 Bq/m³), was 0.23 Sv, which was about 1/4000 of dose limit for general public.     

Determination of a strong organic ligand dissolved in seawater: Thorium-complexing capacity of oceanic dissolved organic matter

Studies have been made of loose water tritium (LWT) distribution and behavior in the soil samples taken from the region within a radius of 2 km to the HWRR stack of CIAE. The analytical results show that the LWT concentrations in most soil samples of the region are in the range from 24.8 Bq/l (3.6 Bq/kg) to 116 Bq/l (16.0 Bq/kg) with an average value of 58.1±24.8 Bq/l (10.3±4.5 Bq/kg). There are two areas with a higher LWT content; the first one (4.61 · 10⁴ m²) is located near HWRR with ahighest LWT concentration of 287 Bq/l (55.8 Bq/kg) and the second one (3.27 ·10⁵ m²) is located near Lab. A with a highest LWT concentration of 2.35 · 10⁴ Bq/l (2.56 · 10³ Bq/kg). It is estimated that the LWT inventories deposited in soil of the two areas are about 1.52 · 10⁹ Bq and 1.42 · 10¹⁰ Bq, respectively. The analytical results have been evaluated by comparing the possible tritium intake of the human body with the annual limit of intake recommended by ICRP, it can be concluded that the operations of all the nuclear facilities releasing tritium in CIAE are safe without causing any notable tritium contamination.     

Radon and tritium measurements in drinking water in a region of central Italy (Umbria)

Summary In the last years the interest in drinking and mineral water radioactivity has grown. Recently national and EU regulations replaced the previous drinking water norms with the aim to strengthen consumers security concerning drinking water quality. Perugia and Urbino Universities carried out a joint study on the radiological characterization of the water destined for human consumption in the Umbria region. The aim of this work was to produce a map of the radon and tritium concentrations in the water of this area as a basis for the implementation of hydrogeological knowledge and to determine a possible related radiological risk for the local population.²²²Rn measurements were performed by liquid scintillation and gamma-spectrometry and³H measurements by liquid scintillation. Up to now, the²²²Rn concentrations ranged 5.9-65.79 Bq/l and³H concentrations are always lower than the detection limit (8.6 Bq/l).     

Environmental radioactivity in Romania Danube river area during 1986–1990

This paper presents the results of radioactivity studies of environmental factors such as surface water, sediment, aquatic vegetation and soil. The concentrations of¹³⁷Cs,⁹⁰Sr,³H, U, Ca, and Mg in water samples were determined by radiochemical and chemical methods. Gamma-spectrometric analyses were performed for all the samples. The analysis showed a decrease in concentrations of¹³⁷Cs in water, aquatic vegetation and sediment, but a constant level of¹³⁷Cs activity in soil (0–5 cm depth). The average concentrations of⁹⁰Sr,³H, U, Ca and Mg were about 7 mBq/l, 11 Bq/l, 0.6 g/l 60 mg/l and 11 mg/l, respectively.     

Determination of technetium-99 from the aspect of environmental radioactivity

A radioanalytical procedure has been developed for the determination of⁹⁹Tc in environmental samples. The procedure consists of precipitation, solvent extraction, ion exchange, electrodeposition and radiation measurement. Rhenium was used as a non-isotopic carrier of⁹⁹Tc. On the basis of 3σ counting error, the detection limits were 4.9·10^?5 Bq/l, 7.4·10^?3 Bq/kg wet and 7.4·10^?2 Bq/kg dry for water, biota and soil samples, respectively. Sea water, seaweeds (brown algae) and soils were collected to evaluate the present levels of⁹⁹Tc in Japan. The level of⁹⁹Tc in sea water was ca. 1·10^?4 Bq/l around Japan. Among the seaweeds (brown algae), Ishige okamurai showed the highest concentration of 5.8·10^?2 Bq/kg wet tissue and the highest concentration factor of 583. The level of⁹⁹Tc in the organic rich surface soil was ca. 1 Bq/kg dry soil in Fukuoka.     

Airborne and waterborne radon concentrations in areas with use of groundwater supplies

Summary A preliminary survey of airborne and waterborne radon concentrations was given for an area where groundwater is used as a source of public water supply. The average of the waterborne radon concentrations was 77 Bq/l for 36 samples and that of airborne radon concentrations was 18 Bq/m³for ten houses. It is concluded that the exposure dose due to radon-in-water is likely to be much smaller than the total dose from natural radiation.     

Physical and chemical investigation of water and sediment of the Keban Dam Lake, Turkey:

Summary The gross alpha- gross beta-activity, ¹³⁷Cs and ⁹⁰Sr in the water and sediment samples taken from the Keban Dam Lake, Uluova Region, was investigated in 2003 and 2004. We have found that in spring the concentration of ¹³⁷Cs in the surface water and deep sediment changed between 0.001-0.01 Bq/l (0.4-2.5 Bq^.kg^-1) that of ⁹⁰Sr between 0.0001-0.009 Bq/l (0.1-9 Bq^.kg^-1) and in autumn the values were 0.0001-0.009 Bq/l (0.4-8 Bq^.kg^-1) for ¹³⁷Cs and 0.0002-0.005 Bq/l (0.6-4 Bq^.kg^-1) for ⁹⁰Sr, respectively. The results were presented in form of iso-curves.     

Estimation of underground water radon danger in Bakreswar and Tantloi Geothermal Region,India

The main aim of the study is to present an evaluation of radon concentration in underground water of Bakreswar and Tantloi geothermal region which is mainly used for drinking purposes of the local people. Water samples were collected from tube-wells at 173 different locations. The radon (²²²Rn) concentration level was observed to fluctuate widely between 3.3 and 803.8 Bq/l with an average of 106.8 Bq/l. Nearly 42% of the samples had radon concentration above the safe limit of 100 Bq/l recommended by World Health Organisation (WHO) and European Union Commission (EU). Considering the WHO and International Commission on Radiological Protection recommended water consumption rate for adults (730 l/year) the corresponding total annual effective dose of the samples were estimated to assess the probable health risk. Total annual effective dose of the samples were varied between 16.72 and 4079.47 µSv/year with an average value of 541.92 µSv/year. About 95% samples exceed the WHO and EU Commission proposed safe limit of 100 µSv/year.     

Determination of U, Pu, Am and Cm in water coolant of nuclear power plants using membranes impregnated with hydrated manganese dioxide

Methods have been developed for the rapid determination of the total activity of α-emitting radionuclides in water coolant. The samples with a volume of 0.05–2.5 dm³ are filtered at a flow rate of 2–2.5 dm³/h through a system of membranes. The first membrane is a mechanical filter for the separation of suspensions, the second one is impregnated with manganese dioxide which is intended for the deposition of actinoids in an ionic state. The detection limit for a 2.5 l sample measured with a low-background alpha-radiometer is equal to 0.037 Bq. The measurement error does not exceed 30% at a confidence level of 0.95 over a determined concentration range from 0.037 to 3.7·10⁵ Bq/l.     

Characteristics of the tritium distribution in the Danube basin region in Yugoslavia

The investigated water samples were collected from rivers, underground waters and precipitations at different locations near Belgrade during the period 1976–1979. By preconcentration and scintillation counting, the individually and monthly collected samples were analyzed for³H contents. It has been found that the³H-concentration in monthly river water samples (Danube, Sava, Tisa) varies from 39 to 196 TU with a maximum in summer, between 0–192 TU in the underground water depending on the sampling depth and distance from river Sava and Danube, while values of 26 to 153 TU have been detected in the monthly precipitation samples attaining a maximum during the break-through of arctic and polar continental air masses. The results were used to calculate the³H quantity deposited per m² (Bq/m²) of surface, due to precipitations and the flow per second (Bq/s) in the investigated locations in rivers. The interrelation between rivers, underground waters and precipitations is discussed. The³H-distributions obtained are correlated with the water level in rivers and with the precipitation quantities and are interpreted in light of the relevant meteorological parameters and other related phenomena.     

Simultaneous determination of trace level bromate and chlorinated haloacetic acids in bottled drinking water by ion chromatography

A convenient and sensitive method for the simultaneous determination of trace level of bromate and chlorinated haloacetic acids in bottled drinking water with ion chromatography is presented. With a high capacity anion-exchange column and 11.5 mmol/l Na₂CO₃ eluent, all the 16 analytes could be separated in one injection within 31 min. By employing a microwave based evaporation technique, the bottled drinking water sample could be concentrated tenfold in 10 min. The recoveries of the compounds ranged from 90.6 to 107.2%. With a 500 μl large volume injection and high performance anion Atlas electrolytic suppressor, the detection limits were 0.06, 0.08, 0.06, 0.14 and 0.85 μg/l for BrO₃⁻, ClO₃⁻, monoacetic acid, dichloroacetic acid and trichloroacetic acid, respectively.     

Liquid scintillation spectrometry of beta-emitters in marine samples

Liquid scintillation spectrometry has become the most widespread method for quantitative analysis of low level -emitters in environmental samples. This technique has been applied in the measurements of ²⁴¹Pu, ³H and ⁹⁰Sr in seawater and sediment samples. ²⁴¹Pu can be measured by direct analysis of an electrodeposited source using - discrimination or by extraction of electrodeposited plutonium into a liquid form compatible with scintillation cocktail. Sediment from Mururoa and Fangataufa atolls showed activities ranging from 18 to 44 Bq/kg. A sediment profile sampled around Bikini Atoll in 1997 showed ²⁴¹Pu activities ranging from 0.3 to 30 Bq/kg. ³H activities in pore water sediment from Mururoa and Fangataufa atolls were of the order of 10³ Bq/m³ which demonstrated its underground origin. ⁹⁰Sr was measured in the presence of ⁹⁰Y. The counting efficiency was 92.41.5% and the background 0.027±0.001 s^-1. The average chemical recovery for ⁹⁰Sr was 673%.     

Distribution characteristics of <Superscript>14</Superscript>C and <Superscript>3</Superscript>H in spent resins from the Canada deuterium uranium-pressurized heavy water reactors (CANDU-PHWRs) of Korea

It is regarded that the spent resins from the water purification systems of moderator (MOD) and the primary coolant of the Canada deuterium uranium-pressurized heavy water reactor (CANDU-PHWR) are a unique waste, owing to their high ¹⁴C and gamma-emitting nuclides. In this work, ¹⁴C and ³H contents, anion and cation fractions and the predominant gamma-emitting nuclides of the spent resins from 4 units of CANDUPHWRs, were investigated. Also the chemical species of ¹⁴C of the spent resins were determined. For a simultaneous separation of ¹⁴C and ³H from the spent resins, the wet oxidation-16 wt% H₂SO₄ stripping process was utilized. The ¹⁴C and ³H activity concentration range of the spent resins of the nuclear power plant (NPP), 4 units of all CANDU-PHWR types, was 2.48E5 Bq/g ∼5.33E6 Bq/g, 1.29E5 Bq/g and ∼2.33E5 Bq/g, respectively. Among the analyzed spent resins, the highest ¹⁴C and ³H activity concentration was detected in units 4 and 3, respectively. It was found that more than 92% of the ¹⁴C activity concentration was retained on the anion resin and the predominant chemical species was inorganic ¹⁴C. It was revealed that the anion resin fraction of the spent resins from unit 1 and unit 2, was about 40% and that of unit 3 and unit 4 was around 60%. More than 80% of the total gamma-radioactivity concentration was associated with the cation fraction of the spent resin. The predominant gamma-emitting nuclide of the spent resin for unit 2 was ¹³⁷Cs, a fission product, and that for unit 4 was ⁶⁰Co, a corrosion product.     

Tritium content as indicator of environmental character on Taiwan Island

Environmental characters have been established by tritium contents in well water, coastal seawater and reservoir water collected from various places around Taiwan island. Tritium concentrations of samples were detected by a liquid scintillation analyzer TRI-CARB-LSC 2550 TR mode, with a low level standard quench curve. After samples were concentrated by electrolysis, tritium concentration was detected in optimum conditions of LLLSA. An electrolytic enrichment technique was also developed with a eurrent density of 100 mA/cm² and 0.4–0.6% (Na₂O₂) electrolyte in concentrated samples. Data observed show a lower tritium concentration for coastal seawater than for wells in the same area. The tritium concentration ratio of well and coastal seawater on the western side of Taiwan is 4.000 and on the eastern side 5.801. Tritium content of reservoir water is related to the logarithm of effective volume capacity.     

Determination of radon-222 in a natural thermal water spring shortly before and after the July 9, 1997 earthquake (Ms=6.8) in the State of Sucre, Venezuela

The original purpose of this investigation started in 1996 was to study the radiological impact on the local population of the village of Chichiviriche de La Costa. But, soon after the major earthquake (Ms=6.8) in the state of Sucre on July 9, 1997, the objective was changed to study the fluctuation of radon (²²²Rn) to see if it could be correlated to seismic activity and/or if the amonlous change just before the earthquake can be considered a precusor for it. Measurements of²²²Rn by simply de-gassing about 250 ml of natural thermal water employing a Pylon AB-5 radiation monitor and counting the radiation after it reached equilibrium were performed. The values for four sampling periods in the first half of 1996 were about 17 Bq/l of²²²Rn, a month before the earthquake they were less than 15 Bq/l and increased about 70% to 25 Bq/l two days before the seismic event. In about two weeks, they returned to about 18 Bq/l. But, surprisingly, they have gradually increased to about 35 Bq/l, before leveling off at about 27 Bq/l.     

Distribution of 14C and 3H in low level radioactive wastes generated by wet waste streams from pressurized water reactors

Summary It is impossible to detect ¹⁴C and ³H by direct methods such as γ-spectroscopy because they are pure b-emitters and thus they are classified as hard to measure nuclides (HTM). In this paper the analysis results of ¹⁴C and ³H in the low level radioactive wastes (LLWs), including spent ion exchange resin, evaporated bottom and sludge are presented. The LLWs were generated by three nuclear power plants (NPPs), in Korea all with pressurized water type reactors (PWRs). A simultaneous separation procedure for ¹⁴C and ³H in LLWs was established by wet oxidation-acid stripping. A liquid scintillation analyzer was used for the measurement of ¹⁴C and ³H. It was found that the recovery of ¹⁴C and ³H was 82-99 and 78-103%, respectively, by wet oxidation-acid stripping with diluted standard solutions. At the lowest injection of ¹⁴C and ³H, i.e., at 1.44 Bq for ¹⁴C and 1.22 Bq for ³H, the minimum detectable activity (MDA) of ¹⁴C and ³H was calculated as 0.88 and 0.78 Bq/g, respectively, for the minimum allowable sample weight, using wet oxidation and 16 wt% H₂SO₄ acid. By the wet oxidation-16 wt% H₂SO₄ stripping method no interfering nuclides were detected in the trapping solution of ¹⁴CO₂ and the distillate of ³H. The activity concentration range of ¹⁴C in the analyzed samples, i.e., spent ion exchange resin, evaporated bottom and sludge, was 0.17-110,000, 8.4-1380 and 0.1-10,006 Bq/g, respectively, and that of ³H in the same was from no detectable to 769, 134-14,383 and 0.7-4820 Bq/g, respectively.     

Distribution of 99Tc and 129I in the vicinity of underground nuclear tests at the Nevada Test Site

⁹⁹Tc and ¹²⁹I are important contributors to risk assessment due to their long half-lives and high mobility as aqueous anionic species. We analyzed ⁹⁹Tc and ¹²⁹I in groundwater samples in and near 11 underground nuclear tests and in melt glass and rock samples retrieved from the Chancellor test cavity, Nevada Test Site. The ¹²⁹I/¹²⁷I ratio ranges from 10⁻³ to 10⁻⁶ in cavity water and 10⁻⁴ to 10⁻⁹ in satellite wells. The ⁹⁹Tc concentration ranges from 3 to 10⁻⁴ Bq/l in cavity waters and from 0.3 to 10⁻⁴ Bq/l in satellite wells. Downstream migration is apparent for both radionuclides. However, it is affected by both retardation and initial distribution. In-situ ⁹⁹Tc and ¹²⁹I K _d s calculated using rubble and water concentrations are 3 to 22 ml/g and 0 to 0.12 ml/g, respectively, and are suggestive of mildly reducing conditions. ¹²⁹I distribution in the melt glass, rubble and groundwater of the Chancellor test cavity is 28%, 24% and 48%, respectively, for ⁹⁹Tc, it is 65%, 35% and 0.3%, respectively. Our partitioning estimates differ from those of underground tests in French Polynesia, implying that fission product distribution may vary from test to test. Factors that may influence this distribution include geologic conditions (e.g., lithology, water and CO₂ content) and the cooling history of the test cavity.     

A new method for the determination of plutonium and americium using high pressure microwave digestion and alpha-spectrometry or ICP-SMS

Plutonium and americium are radionuclides particularly difficult to measure in environmental samples because they are α-emitters and therefore necessitate a careful separation before any measurement, either using radiometric methods or ICP-SMS. Recent developments in extraction chromatography resins such as Eichrom^® TRU and TEVA have resolved many of the analytical problems but drawbacks such as low recovery and spectral interferences still occasionally occur. Here, we report on the use of the new Eichrom^® DGA resin in association with TEVA resin and high pressure microwave acid leaching for the sequential determination of plutonium and americium in environmental samples. The method results in average recoveries of 83 ± 15% for plutonium and 73 ± 22% for americium (n = 60), and a less than 10% deviation from reference values of four IAEA reference materials and three samples from intercomparisons exercises. The method is also suitable for measuring ²³⁹Pu in water samples at the μBq/l level, if ICP-SMS is used for the measurement.     

An improved method for technetium determination in environmental samples

Summary The recent developments of extraction chromatography and ICP-MS made easier the determination of ⁹⁹Tc in environmental samples. However, in the non-contaminated area, a pre-concentration procedure is necessary, because usually a large amount of sample is used for analysis. In this study, the ferrous ion (Fe²⁺) added as a reductant can make chemical yield from 50 to 80%, when larger than 100 liter water samples or 500 g soil samples are analyzed. The extraction chromatography with TEVA resin (EIChrom) and the measurement by ICP-MS have been developed using ^95mTc and ¹⁰³Ru as yield tracers. Detection limits of 3σ are 0.054 mBq/kg for 500 g soil and 0.032 µBq/lfor 500 l water. A pond named Hinotani, Mie Prefecture in the central part of Japan, was selected to be investigated as a natural system in a non-contaminated area. Surface soil near this pond, pond water and sediment were collected and analyzed for ⁹⁹Tc. In a high fall-out area, Okuetsu, Fukui Prefecture forest soil was collected and analyzed. The ⁹⁹Tc in the surface (0-5 cm) was 10.5±0.8 mBq/kg. The ⁹⁹Tc in Hinotani surface (0-5 cm) soil were 0.77±0.06 mBq/kg less than in Okuetsu. Technetium-99 has been determined in pond water, sediment (0-5 cm) and shrimps in the Hinotani pond, 0.25±0.02 mBq/l, 3.3±0.3 mBq/kg, 1.5±0.2 mBq/kg, respectively.     

Determination of tritium in water using electrolytic enrichment: methodology improvements

The quality control of the method for tritium (³H) determination in water after electrolytic concentration by liquid scintillation counting measurements was improved considering more parameters in the uncertainty budget, besides the control charts to evaluate the electrolytic enrichment factor, the enrichment parameter and blank samples. The quality control upgrade of the method and the participation in proficiency tests allow its optimization. This methodology was applied to the determination of ³H activity concentrations in waters from different origins: surface, rain and drinking waters.