Internal Radiation Hazard Research Articles

Determination of naturally radioactive elements in chalk sticks by means of gamma spectroscopy

The radiation hazards due to ingestion of chalkboard dust were investigated. Sixteen samples from three different origin fabricates were used. The estimation of radiation hazard indices were based on the evaluation of the concentration activities of the natural radionuclides 238U, 232Th and 40K. The radium equivalent activity, external hazard index, internal hazard index and the annual dose equivalent associated with the radionuclides were calculated and compared with international recommended values to assess the radiation hazard. The values of internal and external radiation hazard indices were found to be less than unity. The annual effective dose rate obtained, E eff, and the annual gonadal dose equivalent (AGDE) are found to be less than the limit of the doses recommended by the International Commission on Radiological Protection for the general public. The analytical results show that besides the main calcium content, some toxic elements, S, Mo and Pb and Ni and Pb, in the Egyptian and imported chalk stocks, respectively, existed.

Radiological hazards of TENORM in the wasted petroleum pipes

Disposal petroleum pipes containing sludge and scale as a technically enhanced natural occurring radioactive material (TENORM) leads to internal and external radiation hazards and then a significant radiation dose to the workers. In order to contribute to a future waste management policy related to the presence of TENORM in the disposal sites of wasted petroleum pipes, scale and sludge as TENORM wastes are collected form these disposal pipes for radiometric analysis. These pipes are imported from onshore oilfields at south Sinai governorate, Egypt. The highest mean 226Ra and 228Ra concentrations of 519 and 50 kBq/kg respectively, were measured in scale samples. Sludge lies within the normal range of radium concentration. The average absorbed dose caused by the exposure to the wasted pipes equal to 4.09 μGy h −1 from sludge and 262 μGy h −1 from scale. This is much higher than the acceptable level of 0.059 μGy h −1. Due to radon inhalation, important radon related parameters are calculated which advantage in internal dose calculation. Fairly good correlation between real radium content and radon exhalation rate for sludge samples is obtained. The hazards from sludge come from its high emanation power for radon which equal to 3.83%. The obtained results demonstrate the need of screening oil residues for their radionuclide content in order to decide about their final disposal.

Assessment of external and internal doses due to farming in high background radiation areas in old tin mining localities in Jos-plateau, Nigeria

Farming on soils situated in high background radiation areas can result to enhanced radiation exposure scenarios and pathways to humans. To assess the likely levels of exposures, farm soil samples were collected from different farmlands in three old tin mining localities (Bitsichi, Bukuru and Ropp) in Jos Plateau Nigeria, known for high radiations. The soil samples were analyzed for the activity concentrations of 226 Ra, 232 Th and 40 K, using gamma-ray spectroscopy. The outdoor annual effective dose rates were calculated using the activity concentrations of the radionuclides and were found to vary from 0.07 mSv to 2.02 mSv across the three localities. Considering dust generation from soil tillage and inadvertent ingestion of soil particles, the likely internal radiation hazards were estimated using conservative dust and soil loading factors. The total average annual effective dose rates due to 226 Ra and 232 Th that could result from dust inhalation and ingestion of soil particles were 16.9 µSv, 8.1 µSv and 8.8 µSv, respectively for Bitsichi, Bukuru and Ropp. Though these values are about 5% the outdoor exposures to the farmers in those farms and greater than 1 µSv y-1 , from the point of view of radiation protection and risk, they are significant. It suffices to say, therefore, that the results of this study will create the possibility of the importance to evaluate the health risk among the farming population and workplace environments which often is not covered by regulations concerning health protection.

Measurement of natural radioactivity and dose rate assessment of terrestrial gamma radiation in the soil of southern Punjab, Pakistan

Activity concentrations of (226)Ra, (232)Th, (40)K and (137)Cs in soil samples collected from the most populous area of southern Punjab of Pakistan have been measured by gamma-ray spectrometry. The measured activity concentrations for these radionuclides are compared with the reported data from different other countries and it is found that measured activity concentrations are comparable with the worldwide measured average values reported by the UNSCEAR. Subsequently assessed radiological effects show that the mean radium equivalent activity (Ra(eq)) is 96.7 +/- 15.2 Bq kg(-1) and air absorbed dose rate (D) is 46.1 +/- 7.3 nGy h(-1). The values of internal and external radiation hazard indices are found to be less than unity. The annual effective radiation dose is calculated to be 0.28 +/- 0.05 mSv, which is well below the limit of 1.0 mSv y(-1) recommended by the International Commission on Radiological Protection, for the general public.

Assessment of radionuclide concentration in three crustaceans species of the bay of Bengal

The natural (226 Ra, 228 Th, 232 Th and 40 K) and anthropogenic (137 Cs) radionuclides concentrations in three crustaceans species (Penaeus monodon , Metapenaeus monoceros and Panulirus versicolor ), collected from the bay of Bengal, were determined with an aim of assessing any internal radiation hazard due to consumption of the shell fishes and establishing a database for radioactivity levels of the species. Very low level of radioactivity was observed in all the species. The average activity of 226 Ra observed in P. monodon was 1.21 ± 0.27 Bq kg–1 fw; in M. monoceros was 0.70 ± 0.08 Bq kg–1 fw, and in Panulirus versicolor was 1.04 ± 0.09 Bq kg–1 fw. The activity of 232 Th observed in these species was 1.30 ± 0.37, 0.76 ± 0.34 and 1.32 ± 0.70 Bq kg–1 fw, and 228 Th was 0.55 ± 0.26, 0.31 ± 0.14 and 0.74 ± 0.22 Bq kg–1 fw, respectively. The average activity of 40 K observed in these species was 12.56 ± 1.18, 6.38 ± 1.02 and 10.07 ± 1.52 Bq kg–1 fw, respectively. The activity of radiocaesium (137 Cs) was below detection limit. The results indicate that the natural and artificial radionuclides observed in three crustaceans species are safe for human health. A significant relationship was observed between 226 Ra and 232 Th in both the P. monodon (r = 0.839, p ≤ 0.05, df = 4) and the Panulirus versicolor (r = 0.906, p ≤ 0.05, df = 4).

Natural radioactivity in some building materials of Xi’an, China

Eight kinds of building materials collected from Xi’an, China were analyzed for the natural radioactivity of 226 Ra , 232 Th and 40 K using γ -ray spectroscopy. The concentrations of 226 Ra , 232 Th and 40 K in the selected building materials ranges from 19.5 to 68.3 Bq kg - 1 , 13.4 to 51.7 Bq kg - 1 and 63.2 to 713.9 Bq kg - 1 , respectively. The measured activity concentrations for these natural radionuclides were compared with the reported data of other countries and with the world average activity of soil. The radium equivalent activities ( Ra eq ), external hazard index ( H ex ) and the internal radiation hazard index ( H in ) associated with the natural radionuclides were calculated. The Ra eq values of all building materials are lower than the limit of 370 Bq kg - 1 , equivalent to a γ -dose of 1.5 mSv yr - 1 . The values of H ex and H in are less than unity.

Natural radioactivity in some building materials and by-products of Shaanxi, China

The concentration of 226Ra, 232Th and 40K has been determined by γ-ray spectrometry. The measured activity in the selected building materials and by-products of coal fired power plants ranges from 21.5 to 91.3 Bq·kg−1, 15.4 to 63.2 Bq·kg−1 and 83.2 to 683.9 Bq·kg−1 for 226Ra, 232Th and 40K, respectively. The results were compared with the reported data of other countries and with the world average activity of soil. The radium equivalent activities values of all building materials are lower than the limit of 370 Bq·kg−1, equivalent to a γ-dose of 1.5 mSv·y−1. The values of the external hazard index and the internal radiation hazard index are less than unity.

Detection of 210Po on filter papers 16 years after use for the collection of short-lived radon progeny in a room

Radon gas was allowed to accumulate in its radium source and then injected into a 36 m 3 test room, resulting in an initial radon concentration of 15 kBq m –3. Filter papers were used to collect the short-lived radon progeny and thus to measure the Potential Alpha Energy Concentration (PAEC) in-situ in the year 1984 at different times and conditions according to the experimental design. The radon progeny collected on the filter papers were studied as a function of aerosol particle concentration ranging from 10 2–10 5 particles cm –3 in three different experiments. The highest aerosol particle concentration was generated by indoor cigarette smoking. Those filters were stored after the experiment, and were used after 16 years to study the activity of the radon long-lived alpha emitter progeny, 210Po (T 1/2=138 days). This isotope is separated from the short-lived progeny by 210Pb beta emitter with 22.3 years half-life. After 16 years’ storage of these filters, each filter paper was sandwiched and wrapped between two CR-39 nuclear track detectors, to put the detectors in contact with the surfaces of different filters, for 337 days. Correlation between the PAEC measured using filter papers in the year 1984 and the activity of long-lived alpha emitter 210Po on the same filter papers measured in the year 2000 were studied. The results of the 210Po activity showed a very good correlation of 0.92 with the PAEC 16 years ago. The results also depict that the PAEC and 210Po activity in indoor air increased with the increase of aerosol particle concentration, which shows the attachment of short-lived radon progeny with the aerosol particles. The experiment proves that indoor cigarette smoking is a major source of aerosol particles carrying radon progeny and, thus, indoor cigarette smoking is an additional source of internal radiation hazard to the occupants whether smoker or non-smoker.

Radiological Safety Experience in the Fabrication of Alloy Plate Fuels Bearing233U/Pu

The first incidence of [sup 233]U-bearing fuel fabrication in India was the production of aluminum-clad Al-[sup 233]U alloy fuel for the Kamini research reactor. The reactor physics experiments for this fuel are now being carried out in the Purnima III critical assembly, where Al-Pu alloy plate fuels will also be used. Both types of fuels were fabricated in the radiometallurgy laboratories of Bhabha Atomic Research Centre. The hazard potential of each step, evaluated from the site-specific radiological field data, is summarized. The parameters analyzed for this purpose include external and internal radiation hazards, contamination hazards, age of fuel material (i.e., time after separation), and experimental thermoluminescent detector exposure data. Gamma spectrometric data of the finished fuel plates were also analyzed for their utility in checking the material inventory. The collective dose equivalent from the fabrication operations for 12 subassemblies (9 bearing [sup 233]U and 3 bearing plutonium) was 67 mSv, arising from external exposures only. The internal exposure was nil. Fabrication of fuel plates constituted [gt]60% of the total exposure. Fabrication of fuel subassemblies and quality control inspection at all the stages accounted for the remaining radiation exposure. Handling of [sup 233]U/Pu-bearing fuels is likely to increase in the yearsmore » ahead in India. In this context, analysis of radiological field data has yielded useful guidelines for future work.« less

Health physics practices in laboratories using 3 H- and 14 C-labeled tracers.

AbstractTritium and14C are often considered relatively safe radionuclides to handle because their permissible body‐burdens are orders of magnitude greater than those for most radionuclides. This is reflected in the U.S. Atomic Energy Commission regulations that do not require a license for the use of amounts up to 1000 μCi of3H and 100 μCi of14C. Although many tracer studies are performed with much smaller quantities, poor control of even these small amounts can result in contamination, causing an internal radiation hazard or the loss of valuable experimental data. This paper discusses the methods of handling radioactive materials that minimize the risks of contamination, and it emphasizes the needs for proper storage, secondary containers, monitoring air and surfaces, and analysis of bioassay samples for measuring body burdens. The user's responsibilities for licensing, waste disposal and transportation are also included. The authors' experience at a laboratory handling both tracer and curie amounts of14C and3H required for labeling and synthesizing compounds and methods of accident prevention and decontamination are described.

Some factors contributing to the internal radiation hazard in the radium luminising industry.

Some factors contributing to the internal radiation hazard in the radium luminising industry.

Metabolism of Zinc-65 in Man

In view of the importance of zinc in many enzyme systems, and of the fact that zinc is an essential trace element in the human body, a study of the excretion, retention, and tissue distribution of Zn65 in man was performed. Zinc-65 is also a neutron-induced radionuclide and is, therefore, potentially an internal radiation hazard. The dose from Zn65 is a function of the y-particle distribution and turnover in the body. The tissue distribution and excretion of Zn65 have been investigated in animals (1, 2), and more recently these studies have been extended to man (3, 4). In the present investigation the blood levels, excretions, and tissue distribution of Zn65 in man were also related to the retention of Zn65 in the body as determined by the whole-body counting technique.

DIFFERENCES IN THE DISTRIBUTION OF ZIRCONIUM-95 AND NIOBIUM-95 IN THE RAT.

ZIRCONIUM-95, one of the γ-ray emitting isotopes in fall-out, has a physical half-life of 65 days. It decays to niobium-95 which emits γ-rays and has a physical half-life of 35 days. Therefore, both these isotopes contribute to the total radiation hazard of fall-out. During the first year, these two isotopes share no less than 20 per cent of the total activity of fission products aged from a few days to one year1. A knowledge of the metabolism of the parent isotope (zirconium-95) in relation to that of the daughter (niobium-95) is essential in order to estimate the total internal radiation hazard due to 95Zr–95Nb because the parent and the daughter decay at different rates. Further, the photopeak energies of zirconium-95 (0.72 MeV) and niobium-95 (0.764 MeV) are so close to one another that it is not possible to resolve and identify the individual photopeaks of the parent and daughter isotopes by γ-scintillation spectrometry1. Therefore, we have determined the physical decay patterns of 95Zr–95Nb accumulated by rat tissues to determine whether some tissues show preference for zirconium-95, while others concentrate niobium-95 in four days after intraperitoneal administration of 95Zr–95Nb in transient equilibrium (Fig. 1).

Maximum Permissible Activity (MPA) for Fission Products in Air and Water

When mixed fission products are present in air and water, the maximum permissible activity (MPA) is dependent on the relative activtty of the individual isotopes. This, in turn, is dependent on the age of the products. The MPA can be determined most accurately from measurements of the isotopic concentrations; however, the separation of mixed fission products into their constituent activities is extremely complicated and costly. In order to provide a simple method of evaluating the internal radiation hazard, MPA's for an ideal mixture of fission products vs. its age were calculated and plotted. The resulting curves show that the MPA's change appreciably with time. Between 1 day and 3 years for 40 hr per week occupational exposure, they decrease from 2.7 x 10/ sup -//sup 7/ to 1.2 x 10/sup -//sup 9/ mu c/cm/sup 3/ (microcuries per cubic centimeter) for air, and from 1.6 x 10/sup -//sup 3/ to 1.7 x 10/sup -//sup 5/ mu c/cm/sup 3/ for water. From the curves a first approximatton of the MPA-s and therefore the allowable fission product activity in air and water, can be obtained. In order to use the curves, one needs to know only the disintegration rate per unit volume andmore » the approximate age of the products. (auth)« less

Health hazards associated with rolling normal and enriched uranium-evaluation and control.

Industrial health surveys have been made over a period of 5 years during rolling operations with normal uranium at LASL and at two off-site plants. The results indicated that personnel participating in this work were not exposed to above-tolerance levels of external or internal radiation hazards. The external radiation hazards were evaluated by means of personnel film badges. The internal hazards from alpha active particles were measured by means of air and urine samples. The exposure at LASL during normal uranium rolling (with adequate ventilation) never exceeded 10% of tolerance. During hot rolling (primary) operations at an off-site plant, with inadequate or no ventilation, personnel were exposed to levels of air-borne contamination above daily tolerance levels for short periods of time. During warm rolling (secondary) operations with normal uranium at a second off-site plant, exposures were less than 10% of daily tolerance levels. Industrial health surveys have been made during enriched uranium rolling operations at LASL. These rolling operations were performed in a workroom with ventilation designed for normal uranium operations. Results of air sampling indicate personnel were exposed to air concentrations above tolerance for short periods of time. Results of urine analysis showed the average exposures never exceeded 20%more » of tolerance. Hot rolllng from salt baths presents the greatest hazards. Hazards during warm rolling from oil baths are minimal. Recommendations are given for the control of health hazards.« less