Mu Sv Research Articles

Radioactivity, radiogenic heat production and environmental radiation risk of the Basement Complex rocks of Akungba-Akoko, southwestern Nigeria: insights from in situ gamma-ray spectrometry

The Basement Complex rocks of Akungba-Akoko, southwestern Nigeria, typically migmatites (M), biotite gneisses (BGN), granite gneisses (GGN), charnockites (Ch), biotite granites (BG) and pegmatites (P), were assessed using ground gamma-ray spectrometry (GRS). This study aimed at determining rocks’ radionuclides concentration, alterations, radionuclides mobilization, radiogenic heat production (RHP) rate (first report for the area) and environmental radiation risk to humans. The results of this study were integrated with previous data on the petrography and geochemistry of these rocks, for detailed interpretation. The results of average elemental and activity concentrations for Akungba-Akoko rocks, were 2.66%, 3.16 ppm and 13.98 ppm, and 831.35, 39.01 and 56.77 $$Bq{kg}^{-1}$$ for 40K, 238U and 232Th, respectively; with increasing rock order of Ch < M < GGN < BGN < P < BG. High radionuclides concentration in the rocks, with exception of charnockites, were determined by high amount of K-feldspar, plagioclase, biotite and accessory minerals—zircon and monazites. On the other hand, the low radionuclides concentration in the rocks, especially in Ch and M, were aided by the variability of the naturally occurring radioactive elements (NORMs) caused by alterations and mobilization during metamorphism and crystallization processes as suggested by radioelements composite, K/eTh ratio and F-parameter of Efimov analyses. RHP average of 2.03 $$\mu W{m}^{-3}$$ above the crustal average range of 0.8–1.2 $$\mu W{m}^{-3}$$ may have significantly contributed to the heat flux in the studied area; however, the RHP of charnockites are lower than the crustal range. The absorbed dose rate average of 87.98 $$nGy{ h}^{-1}$$ was within the permissible range, and other estimated radiological parameters, namely annual effective doses, hazard indices, gamma activity and activity utilization index, were all far below the permissible limit of 1 $$mSv {y}^{-1}$$ for these rocks. However, the annual gonad dose equivalent (618.874 $$\mu Sv{ y}^{-1}$$ ) and excess life cancer risk (1.511 × 10− 3) were above their permissible limits. Due to the high gamma radiations from the pegmatitic and biotite-rich rocks in the studied area, their high usage should be reduced. Hence, periodic monitoring of the study area is advised.

Practical protective tools for occupational exposure: 1) double focus spectacles for the aged with highly refracted glass lens 2) remodeled barrier for radiation protection.

Two practical protective tools for occupational exposure for neurointerventional radiologists are presented. The first purpose of this study was to investigate the effectiveness of double focus spectacles for the aged with a highly refracted glass lens (special spectacles for the aged) for radiation protection of the crystalline lens of the eye in comparison with other spectacles on the market, based on the measurement of film density which was obtained by exposure of X-ray through those spectacles. As a result of the film densitometry mentioned above, the effectiveness of special spectacles for the aged in radiation protection was nearly equal to the effectiveness of a goggle type shield which is made with a 0.07 mm lead-equivalent plastic lens. The second purpose of this study was to investigate the effectiveness of the protective barrier, which we remodeled for cerebral angiography or neuroendovascular therapy, for radiation exposure, based on the measurement in a simulated study with a head phantom, and on the measurement of radiation exposure in operaters during procedures of clinical cases. In the experimental study radiation exposure in supposed position of the crystalline lens was reduced to about one third and radiation exposure in supposed position of the gonadal glands was reduced to about one seventh, compared to radiation exposure without employing the barrier. The radiation exposure was monitored at the left breast of three radiologists, in 215 cases of cerebral angiography. Employing the barrier in cerebral angiography, average equivalent dose at the left breast measured 1.49mu Sv during 10 min of fluoroscopy. In three kinds of neuroendovascular therapy in 40 cases, radiation exposure in an operator was monitored in the same fashion and the dose was recorded less than the result reported in previous papers in which any protective barrier have not been employed in the procedure (1,2). As a result, the two above mentioned protective tools are considered practical in clinical usage and very effective to reduce radiation exposure in an operator of interventional neuroradiolgy which may sometimes require many hours to complete the therapy under extended fluoroscopic time. 1) The first topic of this report is double focus spectacles for the aged with a highly refracted glass lens (special spectacles for the aged).

Dynamic distribution and dosimetric evaluation of human non-specific immunoglobulin G labelled with 111In or 99Tcm.

This study presents data on the dynamic distribution and dosimetry of 111In- and 99Tcm-labelled human non-specific immunoglobulin G (IgG), two recently developed radiopharmaceuticals for the detection of infection and inflammation. Five healthy volunteers were injected with 20-75 MBq 111In-IgG and seven patients were injected with 740 MBq 99Tcm-hydrazinonicotinamide derivative (HYNIC)-IgG. Blood samples, urine and feces were collected. Whole-body gamma camera imaging studies were performed. The activity in source organs was quantified using the conjugate view counting method and a partial background subtraction technique. Dosimetric calculations were performed using the MIRD technique. For 111In-IgG, the mean biological half-times in the blood were 0.90 and 46 h for the a- and b-phase, respectively. For 99Tcm-HYNIC-IgG, these half times were 0.46 and 45 h. For 111In-IgG, the mean cumulative urinary excretion in the first 48 h was 18% of the injected dose, while excretion in the feces was less than 2% of the injected dose. For 99Tcm-HYNIC-IgG, the whole-body retention was always 100% up to 24 h. The mean absorbed doses in the liver, spleen, kidneys, red marrow and testes from 111In-IgG were 0.8, 0.7, 1.2, 0.3 and 0.4 mGy MBq-1 respectively. The mean absorbed doses for 99Tcm-HYNIC-IgG to these organs were 16, 24, 15, 10 and 22 mu Gy MBq-1 respectively. The mean effective dose was 0.25 mSv MBq-1 and 8.4 mu Sv MBq-1 for 111In-IgG and 99Tcm-HYNIC-IgG respectively. In conclusion, the radiation absorbed doses for both 111In-IgG and 99Tcm-HYNIC-IgG are low and, therefore, these radiopharmaceuticals can be administered safely from a radiation risk perspective.

Measurement of artificial radionuclides in whole diets around the BNF plc reprocessing plant at Sellafield, Cumbria

The Ministry of Agriculture, Fisheries and Food has conducted a duplicate diet study around the BNF reprocessing plant of Sellafield in Cumbria. Samples were collected from adults and children. The results of analyses for a number of artificial radionuclides are reported; dose calculations using actual food intakes have also been made. Samples were obtained in both winter (phase I) and summer (phase II), between which times the Chernobyl accident occurred, making site-specific dose assessment from caesium isotopes difficult in summer samples. Control diets were collected from a coastal area in Lancashire. Average annual doses based on pre-Chernobyl sampling ranged from 2 mu Sv in control children to 14 mu Sv in study adults. This range increased to 9-50 mu Sv in the second phase of the study. Maximum individual doses were 86 mu Sv in phase I and 102 mu Sv in phase II, these being well within the government's target dose for members of the public.

Measured human thyroid 125I activities deriving from waste discharges in the Thames Valley area, UK

Over the period 1984-9 260 excised human thyroids from the five areas along the Thames Valley were measured for 125I. The radioiodine derives from waste discharges via the drinking water. Activity concentration increased 4-fold during this period in those areas deriving drinking water from the River Thames. The maximum recorded thyroid activity was 203 mBq g-1 (dry wt) giving a calculated thyroid dose-equivalent of 7.2 mu Sv y-1 assuming a steady, chronic situation. The total collective annual dose-equivalent to the thyroids of the population in the Thames Valley during 1989 from the uptake of 125I arising from waste disposal was about 6 man-Sv. This cannot be expected to produce any detectable increase in the incidence of thyroid cancer.

Trends in childhood leukaemia in the Nordic countries in relation to fallout from atmospheric nuclear weapons testing.

To obtain further information about the risks of childhood leukaemia after exposure to ionising radiation at low doses and low dose rates before or after birth or to the father's testes shortly before conception. Observational study of trends in incidence of childhood leukaemia in relation to estimated radiation exposures due to fallout from atmospheric nuclear weapons testing during the 1950s and 1960s. Nordic countries. Children aged under 15 years. Incidence rates of leukaemia by age at diagnosis, sex, country, and calendar year of diagnosis or year of birth; exposure category; relation between leukaemia and exposure for children aged 0-14 and 0-4 separately. During the high fallout period the average estimated dose equivalent to the fetal red bone marrow was around 140 mu Sv and the average annual testicular dose 140 mu Sv. There was little evidence of increased incidence of leukaemia among children born in these years. Doses to the red bone marrow of a child after birth were higher, and during the high exposure period children would have been subjected to an additional dose equivalent of around 1500 mu Sv, similar to doses received by children in several parts of central and eastern Europe owing to the Chernobyl accident and about 50% greater than the annual dose equivalent to the red bone marrow of a child from natural radiation. leukaemia incidence and red marrow dose was not related overall, but rates of leukaemia in the high exposure period were slightly higher than in the surrounding medium exposure period (relative risk for ages 0-14: 1.07, 95% confidence interval 1.00 to 1.14; for ages 0-4: 1.11, 1.00 to 1.24). Current predicted risks of childhood leukaemia after exposure to radiation are not greatly underestimated for low dose rate exposures.

Abschätzung der effektiven Dosis bei Knochenmineralmessungen mit Photonenabsorptiometrie und Computertomographie

There is still some uncertainty in the assessment and comparison of patient dose which results from bone mineral measurements on the lumbar spine by photon absorptiometry and x-ray computed tomography (CT). In the literature, skin dose values are offered in almost all cases. These are not meaningful, however, as the size of the irradiated volume and the radiation sensitivities of the respective organs are not taken into account. Here, the concept of effective dose has to be applied. An assessment of effective dose resulted in approximately 1 mu Sv for absorptiometry and approximately 30 mu Sv for computed tomography with low kV and mAs values. For lateral lumbar spine films which are often taken in connection with absorptiometry, at least 700 mu Sv have to be added. In CT, additional 30 mu Sv result from the lateral topogram which is required for positioning. The concept of effective dose, the data and assumptions used in its assessment and a comparison to other risk factors, as for example natural background radiation of approximately 2400 mu Sv per year, are discussed in detail.

Terrestrial gamma radiation levels outdoors in Cantabria, Spain

Terrestrial gamma-ray dose rates have been measured outdoors throughout the region of Cantabria, located in the north of Spain. Results obtained are shown in tabular and cartographical form and are related to the nature of the ground and other influencing factors. The mean absorbed dose rate in air outdoors is 35.46 nGy h-1. The mean annual effective dose equivalent, when the duration of outdoor exposure and distribution of the population are considered, is about 32 mu Sv. This dose is in addition to those doses received from other sources of natural radiation, principally from the presence of radon gas indoors.

A Radiological Evaluation of Phosphogypsum

Phosphogypsum is the by-product resulting from phosphoric acid or phosphate fertilizer production. The phosphate are used in these chemical processes contains the naturally occurring radioactive material U and all its subsequent decay products. During processing, the U generally remains in the phosphoric acid product, while the daughter, 226Ra, tends to be concentrated in the phosphogypsum. Phosphogypsum has physical properties that make it useful as a sub-base for roadways, parking lots, and similar construction. A radiological evaluation, to determine exposures to workers mixing this material with a stabilizing agent (portland cement), was performed at a South Louisiana phosphoric acid chemical plant. Measurements of the 226Ra content of the phosphogypsum showed an average of 1.1 +/- 0.3 Bq g-1 (0.7-1.7 Bq g-1). The average measured gross gamma exposure rate on the phosphogypsum pile corresponded to a dose equivalent rate of 0.368 +/- 0.006 mu Sv h-1 (0.32-0.42 mu Sv h-1). Radon daughter concentrations measured on top of the phosphogypsum pile ranged from 0.0006 to 0.001 working levels. An analysis of the airborne 226Ra concentrations showed only background levels.

An investigation of photonuclear reactions in Cerrobend eutectic material with an 18 MV linac

Under normal operating conditions, a patient undergoing radiotherapy will receive a total dose of approximately=5 Gy per treatment in terms of monitor units. Since the overall half-life of the activity is of the order of 49 minutes, and the radiation shielding blocks are usually customized for the patient, there would be no further build-up of activity with daily treatments. This implies a dose equivalent rate of the order of 3 mu Sv h-1 will be received by the hands of radiographers handling the blocks. However the activity can and would be expected to increase with greater accelerator voltages. Even so, it is unlikely that dose equivalent rates will pose a radiation hazard. It is concluded that photonuclear reactions in Cerrobend do not result in significant exposure to radiographers and other staff in a radiation oncology facility (at least for photon beam energies up to 18 MV).

Superheaded drop bubble neutron dosimeter performance in a work environment

Bubble dosimeters offer a unique combination of sensitivity, immediate results, and dose-equivalent response, but their use has been limited by temperature and vibration. To determine their practicality, the authors simulated a large operation in an air-conditioned radiation work environment. One hundred and twenty devices of three types were tested. The batch homogeneity and reproducibility were about 20 %, and the lower limit of detection was about 10 mu Sv (1 mrem). The dose equivalent indicated by bubble dosimeters agreed with remmeters and spectrometers more closely than did the dose indicated by conventional dosimeters. >

A feasibility study for the simultaneous measurement of carbon, hydrogen and oxygen using pulsed 14.4 MeV neutrons

A Philips continuous mode 14.4 MeV neutron generator has been modified to pulsed operation at a repetition frequency of 1 kHz. The torso section of a Bush phantom containing a tissue-equivalent solution, located 5 cm above a 15 cm diameter*12.5 cm NaI(Tl) detector, was irradiated with a 3 cm*10 cm neutron beam. The detection of the induced gamma emission from the phantom in four sampling intervals during the pulsing cycle has permitted the separation of prompt events due to inelastic scattering of fast neutrons, prompt radiative capture and delayed emission. The reproducibility of 25 measurements of the major soft tissue elements carbon, hydrogen and oxygen was +or-9.3, +or-2.0 and +or-8.3% for a measured collimated dose of 0.17 mSv per measurement. If a 1 m section of the human body were similarly irradiated, the dose average would be less than 10 mu Sv.

Individual and population doses in Manitoba from chiropractic x-ray procedures

Manitoba (population of 1.0 million) has a total of 37 chiropractors who perform X-rays on behalf of the 100 practising chiropractors. In 1987 these specialists performed approximately 33300 spinal X-ray studies. Of the three main types of studies done, cervical spine examinations contribute the lowest patient does (average HE of 26 mu Sv) while thoracic and lumbar spine examinations show a considerably higher patient dose (HE in the range 240-410 mu Sv). The average patient HE was determined to be 220 mu Sv. Lumbar spine examinations account for 45% of all chiropractic X-ray examinations, and contribute 84% of the collective dose. Cervical spine examinations also account for 45% of chiropractic X-ray examinations, but contribute only 5% of the collective dose with thoracic spine examinations contributing the 11% balance of the collective dose. Patients undergoing chiropractic procedures involving exposure to X-rays account for about 3.6% of all diagnostic X-ray procedures in this province. The per caput dose contribution from chiropractic practice was calculated to be 7.3 mu Sv which is estimated to be about 1.2% of the total population dose from diagnostic procedures employing ionising radiation.

In vivo measurements of bone lead-a comparison of two X-ray fluorescence techniques used at three different bone sites

In vivo bone lead measurements have been made on a group of about 120 people, most of whom were lead exposed workers. Two different X-ray fluorescence (XRF) techniques were used to make measurements at three bone sites. Finger lead was measured using 57Co sources, and lead measurements were made in both tibia and calcaneus with a technique based on 109Cd sources. The results of the bone lead measurements correlated strongly with each other and with the index of cumulative exposure, thus confirming the value and reliability of these in vivo measurements as a tool in the study of chronic lead exposure. Measurement precision, +or-1 standard deviation, was highest for tibia +or-7.4 mu g (g bone mineral)-1, +or-16.6 mu g (g bone mineral)-1 for the calcaneus and lowest for phalangeal lead +or-25.0 mu g (g bone mineral)-1. Maximum absorbed doses to the skin were comparable for all three measurements (1-3 mGy). The mean whole body dose equivalents were all low, but that for the finger measurement, 0.1 mu Sv, was significantly less than for the calcaneus and tibia measurements 3-5 mu Sv.

Radiation doses and detriment from chest X-ray examinations

Radiation dose distributions for chest X-ray examination have been measured in a Rando phantom for three views (AP, PA and lateral) as a function of kVp. On the basis of these data, the relationship between the surface dose energy imparted and the effective dose equivalent have been determined. The mean energy imparted in typical chest examination (PA+lateral views at 100 kVp) is 1.7 mJ and the corresponding value of the effective dose equivalent, HE, is 42 mu Sv. The measured radiation doses associated with chest X-rays were compared with the predictions of Monte Carlo calculations. The average difference between Monte Carlo and measured data for the HE was only about 16%. Demographic features (age/sex) of patients undergoing chest X-rays were investigated, and a population irradiation factor (PIF) introduced to estimate the radiation detriment to this population. The probability of expressed radiation-induced detriment to the patient population from chest X-ray examinations was computed to be about one half of that expected for a normal adult (working) population receiving the same dose. The radiation risk associate with chest X-ray examinations for this population was estimated to be less than 0.3 fatal cancers plus serious genetic disorders in the first two generation per million patient examinations.

A method for the assessment of X-ray doses from laser plasma sources

A method for assessing ionising radiation doses from laser plasma sources is presented. Results of an example used to demonstrate the method indicate that, under the assumptions of the analysis, the directional dose equivalent at 0.07 mm depth (H'(0.07)) for photon energies Ep greater than or equal to 10 keV is 75 mu Sv J-1 of laser energy, assessed at 1 m (dry air) from a plasma source. The highest component of this dose equivalent ( approximately 12 mu Sv J-1 keV-1) results from photons of energy around 10 keV. For the same example, the directional dose equivalent at 10 mm depth (H'(10)) for Ep>or=10 keV is 20 mu Sv J-1; the highest component of which ( approximately 1.3 mu Sv J-1) resulting from photons of energy between 15 and 20 keV. Further examples given in this study predict the reduction in the dose equivalents when additional attenuating media are used between the source and an exposed person.

Neutron dosimetry employing soft errors in dynamic random access memories

A programme of work on soft errors of 64 K and 256 K DRAMs has begun in these laboratories, studying the error rates and modelling them. A feasibility study is being carried out of neutron dosimetry employing soft errors in 256 K DRAM. Thermal neutrons from a neutron howitzer and albedo neutrons from 252Cf neutrons scattered off a water phantom produced 'soft errors', through the action of alpha particles and tritons, generated by the (n, alpha ) reaction in 6LiF converters. The energy dependence of the soft error rate (SER) was studied by degrading 5.5. MeV alpha particles after passage through plastic absorbers. The dependence of SER on the operating bias of DRAM was also studied. For the study of thermal neutron sensitivity, the thickness of the 6LiF converter was optimised. A calibration curve of soft errors against dose equivalent was plotted, the dose equivalent having been calculated from thermal neutron flux measurements. A dose equivalent of 25 mu Sv corresponds to a soft error of about 1. There are potential advantages of a DRAM as a digital neutron dosemeter.

Measured human thyroid radioactivities in Britain arising from the Chernobyl disaster

131I activities in thyroids taken at necropsy from more than 160 adults from 7 areas in Britain who died during the 9 weeks following the Chernobyl incident were measured. Peak mean specific activities in these areas varied from 2.5-5 Bq g-1 dry weight (i.e. by a factor of only 2) in spite of the reported enhanced deposition of radioactivity in N and W Britain. It is suggested that this reflects diets deriving from a wide area, including the pooling of milk. Activities decayed with effective half-lives 11-16 days, which is longer than expected if milk were the only main source. Mean thyroid doses in the areas fell within the range of 44-74 mu Sv with probably most adults in Britain receiving between 15-150 mu Sv and very few more than 200 mu Sv.

A preliminary assessment of individual doses in the environs of Berkeley, Gloucestershire, following the Chernobyl nuclear reactor accident

A preliminary assessment has been made of the individual doses to critical group members of the public in the environs of Berkeley, Gloucestershire, arising from fallout resulting from the Chernobyl nuclear reactor accident. The assessment was based on measurements of airborne radionuclide concentrations, ground deposition and nuclide concentrations in rainwater, tapwater, grass, milk and green vegetables. The committed effective dose-equivalent was found to be 200 mu Sv for an adult, and 500 mu Sv for a 1 year old child; the 10 year old child receiving a dose intermediate between these two values. The estimate accounts only for the nuclides measured and the specific exposure routes considered namely ingestion of milk and vegetables, inhalation and external exposure. However, it is believed that the inclusion of a range of other nuclides of potential significance, which may have been present but not measured, and potential intakes from additional routes is unlikely to increase the above estimates by more than a factor of 2.

The Collective Dose Equivalent Due to the Naturally Occurring Radionuclides in Building Materials in the German Democratic Republic. Part 1

The 226Ra, 232Th and 40K concentrations of building materials have been investigated by gamma spectrometry. The results demonstrate that 90% of bricks and concrete have 226Ra concentrations less than 85 mBq g-1 or less than 50 mBq g-1, respectively. In some waste products of mining and industry especially, the 226Ra concentrations are high compared to those of common building materials. Based on the results, the mean gamma dose equivalent to individuals and the collective dose equivalent have been calculated using the computer code ZYLIA-3. The mean indoor gamma dose equivalent to individuals is 510 mu Sv y-1 and the collective dose equivalent 8.5 X 10(3) man-Sv y-1. The outdoor values range from 60 to 81 mu Sv y-1 and 1.0 X 10(3) to 1.4 X 10(3) man-Sv y-1, respectively.