Dose Commitment Research Articles

Influence of Body Posture on Internal Organ Dosimetry: Radiocesium Exposure Modeling Using Novel Posture-dependent Mesh Computational Phantoms.

Current practice in reference internal dosimetry assumes a fixed upright standing posture is maintained throughout the dose-integration period. Recently, the mesh-type ICRP adult reference computational phantoms were transformed into different body postures (e.g., sitting, squatting) for use in occupational dose reconstruction applications. Here, for the first time, we apply this phantom series to the study of organ dose estimates following radionuclide intake. We consider the specific cases of 137 Cs and 134 Cs ingestion (accidental/occupational intake) with attention to variability in absorbed dose as a function of posture. The ICRP Publication 137 systemic biokinetic model for soluble cesium ingestion was used to compute organ-level time-integrated activity coefficients for reference adults, over a 50-y dose-integration period, for 134 Cs and 137 Cs (and its radioactive progeny 137m Ba). Mean posture time-allocations (h d -1 for standing, sitting, and lying) were taken from published survey data. In accord with modern dosimetry formalisms (e.g., MIRD, ICRP), a posture weighting factor was introduced that accounts for the fraction of time spent within each independent posture. Absorbed dose coefficients were computed using PHITS Monte Carlo simulations. ICRP 103 tissue weighting factors were applied along with the posture weighting factors to obtain committed effective dose per unit intake (Sv Bq -1 ). For 137 Cs ingestion, most organ absorbed dose coefficients were negligibly to marginally higher (< ~3%) for sitting or crouched (lying fetal/semi-fetal) postures maintained over the dose commitment period, relative to the upright standing posture. The committed effective dose coefficients were 1.3 × 10 -8 Sv Bq -1 137 Cs for standing, sitting, or crouched postures; thus, the posture-weighted committed effective dose was not significantly different than the committed effective dose for a maintained upright standing posture. For 134 Cs ingestion, most organ absorbed dose coefficients for the sitting and crouched postures were significantly larger than the standing posture, but the differences were still considered minor (< ~8% for most organs). The committed effective dose coefficients were 1.2 × 10 -8 Sv Bq -1 134 Cs for the standing posture and 1.3 × 10 -8 Sv Bq -1 134 Cs for the sitting or crouched posture. The posture-weighted committed effective dose was 1.3 × 10 -8 Sv Bq -1 134 Cs. Body posture has minor influence on organ-level absorbed dose coefficients and committed effective dose for ingestion of soluble 137 Cs or 134 Cs.

Theoretical comparison of absorbed dose estimation using dose commitment formula and medical internal radiation dose in radioactive iodine-131 therapy

Theoretical comparison of absorbed dose estimation using dose commitment formula and medical internal radiation dose in radioactive iodine-131 therapy

Estimated Lifetime Effective Dose to Hunters and their Families in Sweden after the Chernobyl Accident in 1986 – A Pilot Study

Background/Aim: Hunters and their families, with an over average consumption of food from the forest ecosystem, belong to the most exposed subpopulations in Sweden after the Chernobyl nuclear power plant accident in 1986. Using registry data and results from whole-body measurements algorithms were developed to calculate lifetime effective doses and collective doses to hunters. Methods: Ten hunters and their family members were randomly selected from each of the three counties with the highest fallout in Sweden (Västernorrland, Uppsala, Gävleborg) using the register for hunting weapons from the Police Authority in 1985. Statistics Sweden matched these individuals (n=85), using dwelling coordinates, onto the digital map produced by the Swedish Radiation Safety Authority after aerial measurements of ground deposition of 137Cs (kBq m-2). Internal effective doses were estimated with aggregated transfer factors from ground deposition to in-vivo body concentration for 134Cs and 137Cs in hunters (Bq kg-1). External effective doses were also calculated on these dwelling coordinates for 134Cs, 137Cs and short-lived nuclides, respectively. Annual effective doses for external and internal doses were then cumulated up to a life expectancy of 80 years for men and 84 years for women, respectively. Results: The total lifetime effective doses, from the Chernobyl fallout, to the members of the hunter families in this cohort were on average 8.0 mSv in Västernorrland, 4.5 mSv in Uppsala and 3.9 mSv in Gävleborg. The effective dose to males were about 40% higher than in females. In all counties the internal dose was about 75% of the total lifetime effective dose. The collective dose for all hunters with family members (n=44,000 in total) in these three counties could be approximated at about 250 manSv. Conclusions: This pilot study shows it is possible to use register data to develop algorithms for calculating life-time effective dose commitments for hunters.

Sources of inflow and nature of redistribution of 90Sr in the salt lakes of the Crimea

At the first time for the period after the Chernobyl NPP accident the nature of the redistribution of the 90Sr concentrations in components of the ecosystems of the salt lakes of the Crimea were identified and described. Concentration of 90Sr in water of the salt lakes depends on the sources of the inflow this radionuclide into aquatic ecosystems and salinity level of lakes water. Until April 2014 the flow of the Dnieper river water through the Northern-Crimean canal was more important factor of contamination of salt lakes of the Crimea by 90Sr, than atmospheric fallout of this radionuclide after the Chernobyl NPP accident. Concentrations of 90Sr in water of the salt lakes of the Crimea exceeded 2.4–156.5 times its concentrations in their bottom sediments. The 90Sr dose commitments to hydrophytes, which were sampled from the salt lakes of the Crimea have not reached values which could impact them during entire the after-accident period.

Estimated lifetime effective dose to hunters and their families in the three most contaminated counties in Sweden after the Chernobyl nuclear power plant accident in 1986 – A pilot study

Hunters and their families were one of the most exposed subpopulations in Sweden after the Chernobyl nuclear power plant accident in 1986. In this pilot study we used existing registries and whole-body measurements to develop algorithms to calculate lifetime effective doses and collective doses to some hunters in Sweden.Ten hunters and their family members were randomly selected from each of the three most contaminated counties in Sweden (Västernorrland, Uppsala, Gävleborg) using the register for hunting weapons from the Police Authority in 1985. Hence, this design can be regarded as a closed cohort only including hunters and their family members living in these three counties at the time of the accident. Statistics Sweden matched these individuals (n = 85) with their dwelling coordinates onto the digital map produced by the Swedish Radiation Safety Authority after aerial measurements of 137Cs (kBq m−2). Internal effective doses were estimated using aggregated transfer factors from ground deposition to in-vivo body concentration for 134Cs and 137Cs in hunters (Bq kg−1). External effective doses were also calculated on the dwelling coordinate for 134Cs, 137Cs and short-lived nuclides in these three counties. Annual effective doses for external and internal doses were then cumulated up to a life expectancy of 80 years for men and 84 years for women, respectively.The total lifetime effective doses to the members of the hunter families in this cohort were on average 8.3 mSv in Västernorrland, 4.7 mSv in Uppsala and 4.1 mSv in Gävleborg. The effective dose to men were about 40% higher than in women. In all counties the internal dose was about 75% of the total lifetime effective dose. The collective dose for all hunters with family members, in total about 44,000 individuals, in these three counties could be approximated at about 256 manSv.This study shows it is possible to use register data to develop algorithms for calculating lifetime effective dose commitments for hunters with relatively accuracy.

Fukushima radionuclides in the NW Pacific, and assessment of doses for Japanese and world population from ingestion of seafood.

Variations of Fukushima-derived radionuclides (90Sr, 134Cs and 137Cs) in seawater and biota offshore Fukushima and in the NW Pacific Ocean were investigated and radiation doses to the Japanese and world population from ingestion of seafood contaminated by Fukushima radionuclides were estimated and compared with those from other sources of anthropogenic and natural radionuclides. The total effective dose commitment from ingestion of radionuclides in fish, shellfish and seaweed caught in coastal waters off Fukushima was estimated to be 0.6 ± 0.4 mSv/y. The individual effective dose commitment from consumption of radioactive-contaminated fish caught in the open Pacific Ocean was estimated to be 0.07 ± 0.05 mSv/y. These doses are comparable or much lower than doses delivered from the consumption of natural 210Po in fish and in shellfish (0.7 mSv/y). The estimated individual doses have been below the levels when any health damage of the Japanese and world population could be expected.

Temporal Trend in the Transfer of Sellafield-Derived 14C into Different Size Fractions of the Carbonate Component of NE Irish Sea Sediment

From 1994 onwards, radiocarbon discharges from the Sellafield nuclear fuel reprocessing plant have been made largely to the northeast Irish Sea. They represent the largest contributor to UK and European populations of the collective dose commitment derived from the entire nuclear industry discharges. Consequently, it is important to understand the long-term fate of 14C in the marine environment. Research undertaken in 2000 suggested that the carbonate component of northeast Irish Sea sediments would increase in 14C activity as mollusk shells, which have become enriched in Sellafield-derived 14C, are broken down by physical processes including wave action and incorporated into intertidal and subtidal sediments. The current study, undertaken in 2011, tested this hypothesis. The results demonstrate significant increases in 14C enrichments found in whole mussel shells compared to those measured in 2000. Additionally, in 2000, there was an enrichment above ambient background within only the largest size fraction (&gt;500 μm) of the intertidal inorganic sediment at Nethertown and Flimby (north of Sellafield). In comparison, the present study has demonstrated 14C enrichments above ambient background in most size fractions at sites up to 40 km north of Sellafield, confirming the hypothesis set out more than a decade ago.

Long-term simulations of the 137Cs dispersion from the Fukushima accident in the world ocean

The LAMER calculation code was used for simulation of the distribution of 137Cs released after the Fukushima accident into the Pacific and Indian Oceans. The maximum 137Cs concentration predicted for surface waters of the open NW Pacific Ocean in 2012 (21Bq/m3 at 38°N, 164°E) will be comparable to that observed during the early 1960s after atmospheric nuclear weapons tests. The 137Cs in surface waters of the Pacific Ocean will reach the US coast 4–5y after the accident, however, the levels will be low (<3Bq/m3). All the North Pacific Ocean will be labeled with Fukushima 137Cs 10y after the accident with concentrations below 1Bq/m3. Thirty years after the accident the 137Cs levels in the Pacific and Indian Oceans will be below 0.1Bq/m3, i.e. undetectable on the present global fallout background. The effective dose commitment with ingestion of marine biota found in 2012 in the open NW Pacific Ocean was estimated to be 1.7μSv/y, mostly delivered by 134,137Cs. The estimated dose is by about a factor of 500 lower than the present dose limit for the public.

210Pb and stable lead content in fungi: Its transfer from soil

The uptake and transfer of natural radionuclides, other than 40K, from soil to mushrooms has been somewhat overlooked in the literature. Their contribution to the dose due to the consumption of mushrooms was considered negligible. But the contribution of 210Pb in areas unaffected by any recent radioactive fallout has been found to be significant, up to 35% of the annual dose commitment in Spain. More than 30 species of mushrooms were analyzed, and the 210Pb detected was in the range of 0.75–202 Bq/kg d.w. A slight difference was observed between species with different nutritional mechanisms (saprophytes ≥ mycorrhizae). The 210Pb content was correlated with the stable lead content, but not with its predecessor in the uranium radioactive series, 226Ra. This suggested that 210Pb was taken up from the soil by the same pathway as stable lead. The bioavailability of 210Pb in soil was determined by means of a sequential extraction procedure (NH 4OAc, 1M HCl, 6M HCl, and residue). About 30% of the 210Pb present in the soil was available for transfer to mushrooms, more than other natural radionuclides in the same ecosystem. Lycoperdon perlatum, Hebeloma cylindrosporum, and Amanita curtipes presented the highest values of the available transfer factor, ATF. As reflected in their ATF values, the transfer from soil to mushroom of some natural and anthropogenic radionuclides was in the following order: 228,230,232Th ≈ 40K ≥ 137Cs ≥ 234,238U ≈ 226Ra ≥ 90Sr ≥ 210Pb ≈ 239 + 240 Pu ≈ 241Am.

放射性物質による皮膚汚染時の線量評価

In one of the accidents that might happen in the nuclear power station, there is a contamination accident caused by radioactive corrosion products during a periodic inspection. It is necessary to presume the skin absorbed dose from the adhesion area and the contamination density to forecast the level of the skin hazard by the adhesion of the radioactive substance. However, the data to forecast the local skin dose when the radioactive substance adhered handily is not maintained. In this paper, the absorbed dose in the skin surface neighborhood contaminated by radioactive corrosion products was calculated, and the relation between the adhesion area and the contamination density and the local absorption dose was derived. And, the approximate equation that forecast the integrated dose was derived from these data. As for the absorbed dose rate in depth 70 μm from the skin surface that became the index of the skin hazard, the contribution rate by 59Fe was the highest within 30 days, and the contribution of 60Co rose most after the 30th after the radioactive substance had adhered when the contamination density the adhesion area was the same. The relation between the initial contamination density and days that required it was graphed to reaching to the threshold by the integrated dose when the threshold dose in which the necrosis of the skin was caused was assumed to be 20 Gy. The absorbed dose commitment can be presumed from measurements of the contamination density by using this graph or the approximate equation.

RADIOLOGICAL EFFLUENTS RELEASED BY U.S. COMMERCIAL NUCLEAR POWER PLANTS FROM 1995–2005

Commercial nuclear power plants release gaseous and liquid radiological effluents into the environment as by-products of electrical generation. In the U.S. these releases are monitored by the Nuclear Regulatory Commission (U.S. NRC) and Environmental Protection Agency (U.S. EPA). Traditionally these releases have always been well below the regulatory limits. However, the tracking and analysis of nuclear power radiological effluents was stopped in 1994 by several government agencies. The purpose of this study was to compile the entire U.S. industry effluent data, identify trends, and calculate average population dose commitments since that time. Data were taken from radioactive material release reports submitted by each nuclear power plant. Industry trends were identified using the Mann-Kendall non-parametric test. Total collective effective and population doses were estimated using UNSCEAR and U.S. NRC methodologies. Overall, industry releases have been level over the study time period. Public doses continue to be well below 1% of the regulatory limits.

Investigations on the activity concentrations of 238U, 226RA, 228RA, 210PB and 40K in Jordan phosphogypsum and fertilizers

The activity concentrations of naturally occurring radionuclides ((238)U, (226)Ra, (228)Ra, (210)Pb and (40)K) in Jordanian phosphate ore, fertilizer material and phosphogypsum piles were investigated. The results show the partitioning of radionuclides in fertilizer products and phosphogypsum piles. The outcome of this study will enrich the Jordanian radiological map database, and will be useful for an estimation of the radiological impact of this industrial complex on the immediate environment. The activity concentration of (210)Pb was found to vary from 95 +/- 8 to 129 +/- 8 Bq kg(-1) with a mean value of 111 +/- 14 Bq kg(-1) in fertilizer samples, and from 364 +/- 8 to 428 +/- 10 Bq kg(-1) with a mean value of 391 +/- 30 Bq kg(-1) in phosphogypsum samples; while in phosphate wet rock samples, it was found to vary between 621 +/- 9 and 637 +/- 10 Bq kg(-1), with a mean value of 628 +/- 7 Bq kg(-1). The activity concentration of (226)Ra in fertilizer samples (between 31 +/- 4 and 42 +/- 5 Bq kg(-1) with a mean value of 37 +/- 6 Bq kg(-1)) was found to be much smaller than the activity concentration of (226)Ra in phosphogypsum samples (between 302 +/- 8 and 442 +/- 8 Bq kg(-1) with a mean value of 376 +/- 62 Bq kg(-1)). In contrast, the activity concentration of (238)U in fertilizer samples (between 1011 +/- 13 and 1061 +/- 14 Bq kg(-1) with a mean value of 1033 +/- 22 Bq kg(-1)) was found to be much higher than the activity concentration of (238)U in phosphogypsum samples (between 14 +/- 5 and 37 +/- 7 Bq kg(-1) with a mean value of 22 +/- 11 Bq kg(-1)). This indicates that (210)Pb and (226)Ra show similar behaviour, and are concentrated in phosphogypsum piles. In addition, both isotopes enhanced the activity concentration in phosphogypsum piles, while (238)U enhanced the activity concentration in the fertilizer. Due to the radioactivity released from the phosphate rock processing plants into the environment, the highest collective dose commitment for the lungs was found to be 1.02 person nGy t(-1). Lung tissue also shows the highest effect due the presence of (226)Ra in the radioactive cloud (0.087 person nGy t(-1)).

Radiation exposure and evolutionary perspectives with special references to neutral theory

The truncated natural dose commitment for various periods since the assumed appearance of some of our ancestors may be calculated to have been much higher than for the present period. Background radiation has been a universal component of our environment. Radiation-adaptive response and, possibly, hormesis may be claimed to be an evolutionary expectation. It may also support the cause of the neutral theory, which states that the molecular polymorphism observed in natural populations is due to neutral mutation under drift equilibrium. In the wake of the findings of the Human Genome Project, the neutral theory is worth revisiting, since mutations are selectively neutral and long-term heterozygosity reflects only the population history and mutation rate. The neutral theory considers that genes and proteins are very well adapted because of the past natural selection brought about by the pressure of the radiation environment that facilitated its drift.

CONCENTRATION AND VERTICAL DISTRIBUTION OF 137CS IN THE UNDISTURBED SOIL OF SOUTHWESTERN NIGERIA

The results of measurements of 137Cs in soil profiles that were sampled in undisturbed soil in Ondo, Ekiti, and Oyo states in the southwestern area of Nigeria are presented in this paper. Samples were collected from nine soil profiles. The vertical distributions of 137Cs in the soil profiles have been determined. Cesium concentration ranged from 0.31 +/- 0.10 Bq kg(-1) in the 0-2 cm depth to a maximum of 1.25 +/- 0.21 Bq kg(-1) in the 6-8 cm depth at some sites and from 3.16 +/- 0.16 Bq kg(-1) in 0-5 cm depth to below detection limit (BDL) at 20-25 cm at another site. 137Cs total deposition in 0-10 cm depth was found to be greatest at Ikogosi site with a value of 90.30 Bq m(-2). The results generally showed that more than 40 y after the first nuclear weapon tests, 137Cs still remains within the 25 cm upper layer of soil in the region with a migration velocity of 0.17-0.18 cm y(-1). The mean value of effective dose commitment due to the presence of cesium in soil in the entire region was found to be 10.77 microSv.

Measurement of the Concentration of Radon Gas in the Toirano's Caves (Liguria)

The radioactive gas radon, intermediate term of the decay series of uranium and thorium, is the main contamination source of underground places and may be a risk for high concentration and long exposure time. European and Italian law requires radon concentration to be measured in workplaces and, if the "action level" of 500 Bq/m3 is reached, proper actions must be made in order to decrease the dose commitment. Considering natural showcaves or artificial cavities open to public, the exposition of the visitors is frequently small, due to the short residence time, but accompanying people, remaining underground for long time, may be subject to appreciable dose and the radon concentration should therefore be monitored. The high humidity in natural caves may impair the use of some measuring devices. Therefore, different detection methods were compared (ZnS scintillation counters, E-PERM electret ionisation chambers, cellulose nitrate alpha-track dosimeters) to select the best procedure for long-term investigation. The LR-115 (Kodak) alpha-track dosimeters were insensitive to humidity and permitted to monitor a great number of places at the same time. Measurements have been carried out in the speleological and archaeological site of the Toirano's Caves (Savona, Liguria, Italy) and several points were monitored for two years. Radon concentration strongly depends on the site and changes during the year, due to the difference between internal and external temperature. The maximum dose commitment during the visitors tour, considering the average yearly value of radon concentration, was found to be between 1.5 and 4 microSv. It was found that no risk exists for visitors, but the evaluation of the dose absorbed by the guides and their classification according to the radiation protection law requires a complete monitoring of the average yearly concentration of radon and of the total time spent by each worker into the cave.

The time-dependent effect of the biological component of 137Cs soil contamination

Abstract In investigations of the long-term development of the population dose in the highly contaminated regions of the Commonwealth of Independence States it was found that the external dose has not decreased as strongly as expected since 1992. Further investigations have shown that, contrary to expectations, no linear correlation can be observed between soil contamination and measured area dose rate. As a contribution towards clarifying these issues, the area dose rate and the soil contamination including the plant fraction were investigated in the Korma district, Belarus. It was found that it is necessary to cover and average over larger areas in order to determine from ground contamination the long-term development of the external dose commitment. This means that for this purpose the introduction of an “effective” surface contamination (sum of mineral and organic contamination components) is necessary. The phenomena observed are described in a model, which permits an analytical calculation of the contamination profile in soil taking migration and transfer effects into account. The differences observed between the measured soil contamination and the resulting external doses or the directly measured dose rate can be explained by the proposed model. Moreover, their long-term development can be calculated. The results show that a time decade after the accident the biological part of the “effective” soil contamination becomes dominant and cannot be neglected.

Estimate of the dose-increment due to outdoor exposure to gamma rays from uranium progeny deposited on the soil around a coal-fired power plant in Ajka Town, Hungary.

Brown coal unusually rich in uranium is burnt in a coal-fired power plant that lies inside the confines of a small industrial town named Ajka, Hungary, and has been operational since 1943. The 238U (226Ra) activity discharged to the atmosphere per unit electrical energy produced was about 330-400 GBq (GW y)(-1), which is 66-80 times more than that was estimated by UNSCEAR (1988) as a characteristic value for old type coal-fired power plants [5 GBq (GW y)(-1)]. The objective of this study was the experimentally established assessment of the artificial increment in the dose from external exposure to gamma rays of terrestrial radionuclides outdoors. Soil samples were collected in and near Ajka from 81 locations. The samples were investigated by Ge(Li) gamma spectrometry. Considerably elevated concentrations of uranium and its progeny have been measured in most of the samples that were collected near to the plant. Concentrations of 238U and 226Ra in the top (0-5 cm depth) layer of undisturbed soil at public areas inside town were 4.7 times higher, on average, than those in the uncontaminated deeper layers. Dose rate in air (air kerma) from external exposure to terrestrial gamma rays outdoors at a height of 1 m and effective doses were estimated from the measured activity concentrations using some relevant literature data. The estimated artificial increment in the dose rate in air was, on average, 32.8, 10.3, and 102.1 nGy h(-1) at public areas, vegetable gardens, and backyards, respectively. The mean artificial increment in the annual per caput effective dose from external exposure to terrestrial radionuclides outdoors is 21.8 microSv y(-1). The collective dose commitment per unit energy generated from outdoor exposure to the deposited uranium progeny is about 8.0-9.1 person Sv (GW y)(-1), which is 67-76 times more than that evaluated by UNSCEAR (1988) for a typical "old" coal-fired power plant [0.12 person Sv (GW y)(-1)]. Ajka is a suitable place for studying the dosimetric consequences of the utilization of coal for energy production experimentally.

Ecological standardization of permissible radionuclide pollutions of fresh water ecosystems on the basis of theory and models of radiocapacity

In the case of radionuclide releases and into the environment it is important to assess the maximum admissible values of income of radionuclides into an ecosystem, where there are no yet noticeable biological changes as the result of ionising radiation. The natural boundary for estimation of maximum permissible of radionuclides into ecosystems is the dose commitment or the annual absorbed dose rate. G. Polikarpov and V. Tsytsugina have proposed a scale of dose commitments to ecosystems consisting of four basic dose limits. From the given scale it follows that the real dose limit for release and accidental disposal of radionuclides in ecosystems and their components is the dose rate that exceeds 0.4 Gy y 1 for terrestrial animals and 4 Gy y1 for hydrobionts and terrestrial plants. At such dose rates it is possible to expect a development of evident ecological effects in ecosystems. Dose commitments from a, P', y-radiation are not difficult to assess for the radionuclides composition of the Kyshtum and the Chernobyl releases. According to our assessments the calculated total dose of 0.4 Gy y' to 4 Gy y' (as given by Amiro, (4)) correspond to respective concentration of l37 Cs of about 100 and 1000 kBq l'(kg') in ecosystem or in its elements (terrestrial plants and hydrobionts). The total dose 4 Gy y' corresponds to 137 Cs concentration of about 1000 kBq r'(kg'') for a fresh water ecosystem. The maximum permissible releases of radionuclides into the ecosystems could be assessed on the basis of the above mentioned models and equations, using an assessment of maximum permissible concentration of radionuclides in the components of the ecosystem.

Estimates of Collective Doses from a Hypothetical Accident of a Nuclear Submarine

The collective dose to the Japanese population has been estimated from a hypothetical accident of a nuclear submarine if it sinks in an offshore region around Japan. A computer code system DSOCEAN has been used for assessing the collective dose due to radionuclides released to the ocean from a sunken nuclear submarine. The estimated collective effective dose commitment from all of the radionuclides released after the break of the fuel pellets is estimated to be 2.5 x104 man-Sv. The contribution of 241Am to the total collective effective dose commitment is the highest, followed by 137Cs, 238Pu, 240Pu, 239Pu and 241 Pu. The maximum of the estimated collective effective dose by the annual intake of marine products after radionuclide releases for one year is approximately 0.3% of the annual average dose by the natural radiation that is reported by UNSCEAR.

Radiological impact from atmospheric releases of 238U and 226Ra from phosphate rock processing plants

Phosphate rocks are used extensively, mainly as a source of phosphorus for fertilizers and secondarily for phosphoric acid and other speciality chemicals. Phosphates are typically enriched in uranium and are thus one of the sources of technologically enhanced natural radiation (TENR) which increases exposure to man from natural radionuclides. Emissions from phosphate rock processing plants in gaseous and particulate form contain radionuclides, such as 238U and 226Ra, which are discharged into the environment causing radiation exposures to the population. About 10 MBq each of 238U and 226Ra are discharged into the environment each year from SICNG, a phosphate rock processing plant in Thessaloniki area, Northern Greece. The collective dose commitment to lung tissue resulting from atmospheric releases was estimated to be ∼2×10 −9 person Gy t −1 for 238U and ∼0.1×10 −9 person Gy t −1 for 226Ra, i.e. about 2 times higher than that estimated in the UNSCEAR reports issued in 1982, 1988, and 1993.