Measurement of activity concentrations of natural radionuclides in the topsoil of IITA Ibadan by gamma-ray spectrometry.

The activity concentrations of the natural radionuclides in the soils at the International Institute of Tropical Agriculture, (IITA), Idi-Ose, Moniya, Ibadan, Nigeria were investigated using a NaI (Tl) scintillation detector coupled with a Canberra series 10 plus multichannel analyser as the detecting device for gamma scintillation spectroscopy. The whole area was divided into grids and soil samples were collected from the points of intersection of the grids. The average activity concentrations obtained for the three radionuclides (40K, 238U and 232Th) were 180.08 +/- 90.54 Bq kg(-1) for 40K, 8.901 +/- 5.063 Bq kg(-1) for 238U and 11.01 +/- 7.686 Bq kg(-1) for 232Th. The average values of the absorbed dose rate for each radionuclide were found to be 7.33 nGy h(-1) for 232Th, 7.55 nGy h(-1) for 40K and 3.82 nGy h(-1) for 238U. The average (baseline) of the total absorbed dose rate was found to be 18.72 +/- 8.11 nGy h(-1). The baseline average outdoor annual effective dose equivalent at IITA due to the concentrations of the radionuclides was found to be 22.95 +/- 9.94 microSv y(-1). This value is low compared to the world average of 70 microSv y(-1) specified by UNSCEAR for an outdoor effective dose. Hence the probability of occurrence of any of the health effects of radiation is low.     

Background radiation: natural and man-made.

A brief overview and comparison is given of dose rates arising from natural background radiation and the fallout from atmospheric testing of nuclear weapons. Although there are considerable spatial variations in exposure to natural background radiation, it is useful to give estimates of worldwide average overall exposures from the various components of that background. Cosmic-ray secondaries of low linear energy transfer (LET), mainly muons and photons, deliver about 280 microSv a(-1). Cosmic-ray neutrons deliver about another 100 microSv a(-1). These low- and high-LET exposures are relatively uniform to the whole body. The effective dose rate from cosmogenic radionuclides is dominated by the contribution of 12 microSv a(-1) from 14C. This is due to relatively uniform irradiation of all organs and tissues from low-energy beta particles. Primordial radionuclides and their progeny (principally the 238U and 232Th series, and 40K) contribute about 480 microSv a(-1) of effective dose by external irradiation. This is relatively uniform photon irradiation of the whole body. Internally incorporated 40K contributes a further 165 microSv a(-1) of effective dose in adults, mainly from beta particles, but with a significant gamma component. Equivalent doses from 40K are somewhat higher in muscle than other soft tissues, but the distinction is less than a factor of three. Uranium and thorium series radionuclides give rise to an average effective dose rate of around 120 microSv a(-1). This includes a major alpha particle component, and exposures of radiosensitive tissues in lung, liver, kidney and the skeleton are recognised as important contributors to effective dose. Overall, these various sources give a worldwide average effective dose rate of about 1160 microSv a(-1). Exposure to 222Rn, 220Rn and their short-lived progeny has to be considered separately. This is very variable both within and between countries. For 222Rn and its progeny, a worldwide average effective dose rate is about 1105 microSv a(-1). For 220Rn and its progeny, the corresponding value is 91 microSv a(-1). In both cases, the effective dose is mainly due to a particle irradiation of the bronchial tissues of the lungs. Overall, the worldwide average effective dose rate from natural background is about 2400 microSv a(-1) or 2.4 mSv a(-1). For comparison, worldwide average effective dose rates from weapons fallout peaked at 113 microSv a(-1) (about 5% of natural background) in 1963 and have since fallen to about 5.5 microSv a(-1) (about 0.2% of natural background). These values perhaps serve to emphasise that even gross insults to the natural environment from anthropogenic releases of radioactive materials are likely to be of limited significance when set in the context of the ambient radioactive environment within which all organisms, including humans, have developed.     

Distribution of natural radioactivity in rocks from Ikogosi-Ekiti, Southwestern Nigeria and its radiological implications

The natural radioactivity in some rock samples in Ikogosi-Ekiti, Southwestern Nigeria, has been measured using a very sensitive gamma spectroscopic system consisting of a 76 mm x 76 mm NaI(TI) scintillation detector system coupled to a versatile Canberra Series 10 plus multichannel analyzer. The average concentrations of natural radioisotopes 238U, 232Th, and 40K are 57.9 +/- 28.1 Bq kg-1, 81.6 +/- 23.8 Bq kg(-1) and 1203.1 +/- 687.2 Bq kg(-1), respectively. These average values give rise to a mean absorbed dose rate of 0.128 +/- 0.051, microGy h(-1) at a height of 1.0 m and an effective dose equivalent of 156.90 microSv (y-1). The results indicate no radiological anomaly. The data presented here will serve as a baseline survey for primordial radionuclide concentrations in rocks of the area.     

An assessment of natural radioactivity of soils and its external radiological impact in southwestern Nigeria

Soil samples collected from five states in the southwestern part of Nigeria have been analyzed for activity concentration of gamma-ray emitters. The States were Oyo, Lagos, Ondo, Ogun, and Osun. Activity concentration measurement was carried out using a co-axial type high purity germanium (HPGe) detector. Spectral analyses were performed using spectrometry software. The activity concentration measured ranged from 0.03 +/- 0.2 Bq kg(-1) for 137Cs to 1,358.6 +/- 28.5 Bq kg(-1) for (40)K. (40)K accounted for most of the activity. The calculated absorbed dose rates in air at 1.0 m above the ground ranged from 6 to 303 nGy h(-1) with a mean and standard deviation of 60.5 nGy h(-1) and 63.2 nGy h(-1), respectively. Estimated annual outdoor effective dose equivalent varied from 8 to 370 mSv y(-1). The calculated collective dose equivalent values for the five states ranged from 87,000 person-Sv to 600,000 person-Sv. The estimated annual outdoor effective values were considerably higher than the world soil average value of 70 microSv y(-1) reported by the International Commission on Radiological Protection.     

210Po and 210Pb inhalation by cigarette smoking in Italy

210Po and its precursor 210Pb in cigarette smoke contribute a significant radiation dose to the lungs of smokers. In this work, the concentration of 210Po was determined in 17 of the most frequently smoked cigarette brands in Italy. Samples of tobacco, fresh filters, ash, and post-smoking filters were analyzed; 210Po was determined by alpha spectrometry after its spontaneous deposition on a silver disk. To verify the radioactive equilibrium between 210Po and 210Pb, lead was determined in one tobacco sample by counting the beta activity of its decay product 210Bi with a gas flow proportional detector after separation. The results of the present study show 210Po concentrations ranged from 6.84 to 17.49 mBq per cigarette. Based on these results, smokers who smoke 20 cigarettes per day inhale, on average, 79.53 +/- 28.65 mBq d(-1) of 210Po and 210Pb each. The mean value of the annual committed effective dose for Italian smokers, calculated by applying the dose conversion factor for adults of 4.3 microSv Bq(-1) for 210Po and 5.6 microSv Bq(-1) for 210Pb, was estimated to be 124.8 and 162.6 microSv y(-1) for 210Po and 210Pb, respectively. The lung dose from inhalation of cigarette smoke is much higher than the lung dose from inhalation of atmospheric 210Po and 210Pb.     

222Rn concentration in ground waters of coastal Karnataka and Kaiga of south west coast of India.

Groundwater (open well and bore well) samples from various locations of coastal Karnataka and Kaiga have been investigated for their 222Rn concentrations by emanometry method. The concentration of 222Rn in open well water was found to vary in the range 0.14-25.4 Bq L(-1) with a median value of 3.74 Bq L(-1) and that in bore well water in the range of 0.22-197.0 Bq L(-1) with a median value of 5.75 Bq L(-1). From the measured concentrations the effective doses for the population of the region were estimated. The effective dose was found to vary from 0.09 microSv y(-1) to 204.2 microSv y(-1) for open well water consumers and from 0.2 microSv y(-1) to 1586.9 microSv y(-1) for bore well water consumers. The results of the present study are also compared with the literature values and discussed.     

Exposure to high background radiation level in the tin mining area of Jos Plateau, Nigeria.

The present work deals with the radioactivity of samples of tin tailings collected from a mining site in Jos, Nigeria. The activity concentrations of the samples were measured using a gamma-ray spectrometer with a hyper-pure germanium detector. In situ dose rates at the site were also measured using a precalibrated survey meter. Potassium-40 was not detected in any of the studied samples. The activity concentrations of (238)U and (232)Th ranged from 17.1 x 10(2) to 16.6 x 10(3) Bq kg(-1) and from 52.9 x 10(2) to 47.5 x 10(3) Bq kg(-1), with mean values of 72.2 x 10(2) and 16.8 x 10(3) Bq kg(-1), respectively. The absorbed dose rates were between 4.0 and 36.3 microGy h(-1), with a mean value of 13.5 microGy h(-1), which is much higher than the world average of 0.06 microGy h(-1) for soil. The calculated effective dose rates varied between 2.8 and 25.4 microSv h(-1), with a mean value of 9.4 microSv h(-1), whereas the effective dose rates obtained for the in situ measurement varied between 6.0 and 28.0 microSv h(-1). The annual gonadal dose equivalent was calculated as 92.4 mSv. This is much higher than the world average dose equivalent rate to individuals from soil (0.30 mSv y(-1)).     

Disaggregation of collective dose--a worked example based on future discharges from the Sellafield nuclear fuel reprocessing site, UK.

Collective dose has long been advocated as an important measure of the detriment associated with practices that involve the use of radioactivity. Application of collective dose in the context of worker protection is relatively straightforward, whereas its application in the context of discharges to the environment can yield radically different conclusions depending upon the population groups and integration times that are considered. The computer program PC-CREAM98 has been used to provide an indicative disaggregation into individual dose bands of the collective dose due to potential future radioactive discharges from the nuclear fuel reprocessing site at Sellafield in the UK. Two alternative discharge scenarios are considered, which represent a 'stop reprocessing early, minimum discharge' scenario and a 'reprocessing beyond current contracts' scenario. For aerial discharges, collective dose at individual effective dose rates exceeding 0.015 microSv y(-1) is only incurred within the UK, and at effective dose rates exceeding 1.5 microSv y(-1) is only incurred within about 20 km of Sellafield. The geographical distribution of collective dose from liquid discharges is harder to assess, but it appears that collective dose incurred outside the UK is at levels of individual effective dose rate below 1.5 microSv y(-1), with the majority being incurred at rates of 0.002 microSv y(-1) or less. In multi-attribute utility analyses, the view taken on the radiological detriment to be attributed to the two discharge scenarios will depend critically on the weight or monetary value ascribed to collective doses incurred within the differing bands of individual dose rate.     

Effective dose to the public from 226Ra in drinking water supplies of Iran

One of the most important and prevalent isotopes of radium (Ra) in the human food chain, and especially in drinking water, is 226Ra. To determine the contribution of this radionuclide to the annual effective dose to the public in Iran, a national program for determination of this radionuclide was established. Over 500 water samples from different surface and ground water supplies including wells, rivers and springs, as well as hot springs and sea water from the Caspian Sea and Persian Gulf have been analyzed. An emanation method with a minimum detection limit of less than 2 mBq L(-1) was developed and applied in this study. Unweighted mean concentrations of 3.3 mBq L(-1) and 8.0 mBq L(-1) were determined in surface and ground drinking water supplies, respectively. Based on such values, mean unweighted annual intakes of 226Ra were found to be 0.85 Bq for an infant, 1.97 Bq for a child, and 2.82 Bq for an adult, which correspond to mean unweighted annual effective doses of 0.17 microSv y(-1), 0.39 microSv y(-1), and 0.56 microSv y(-1), respectively. The mean 226Ra concentrations in hot springs were higher with a maximum of 146.5 Bq L(-1) measured in the Ab-e-Siah hot spring in Ramsar, a town on the coast of the Caspian Sea in Iran.     

Disaggregation and valuation of collective dose and global circulation dose.

This study is an extension of earlier work (Jones et al 2004 J. Radiol. Prot. 24 13-27) using an adaptation of the PC-CREAM computer model (Mayall et al 1997 NRPB-SR296 (EUR 17791 EN) (Chilton: NRPB)) applied to future discharge scenarios for the nuclear fuel reprocessing plant at Sellafield, Cumbria, UK. This work showed that, of the total 3700 person-Sv collective dose delivered to the world population over 500 years integration from a particular scenario (SF3), 95% is at levels of individual dose below 0.015 microSv y(-1). The collective dose delivered at individual dose rates below 0.015 microSv y(-1) reflects the contribution from globally circulating radionuclides, namely (3)H, (14)C, (85)Kr and (129)I. The methodology used in the earlier work could not break down the dose from globally circulating radionuclides into bands of individual dose; the principal aim of this study is to achieve such a breakdown. The results confirm that the global circulation dose is received in the very lowest bands i.e. all below 0.015 microSv y(-1) for atmospheric discharges, and all below 0.0015 microSv y(-1) for discharges to the sea in the SF3 scenario. If account is taken of the argument that the monetary value of the detriment associated with collective dose should reduce with decreasing levels of individual dose or risk (Jackson et al 2004 J. Radiol. Prot. 24 41-59; NRPB 1993 Doc. NRPB 4 (2) 75-80) then it can be shown that the value of the detriment associated with discharges in the SF3 scenario would be substantially reduced compared with that derived from current conventional assumptions.     

Estimates of embryonic and fetal doses from 239Pu.

Previously reported studies on the transfer of 238Pu from the maternal circulation to the developing embryo and fetus in rats and guinea pigs have provided data for developing dosimetric models. The highest concentrations of 238Pu were measured in the yolk sac. In late gestation, preferential uptake of 238Pu in liver and bone was observed. The data obtained, together with other published information, have been used to estimate in utero doses to hemopoietic tissues, taking account of transfer to the blastocyst/egg cylinder, yolk sac, liver, and bone marrow. From animal data, the concentration ratios relative to maternal liver for these tissues were taken to be 0.1, 2, 0.01, and 0.02, respectively, and were applied to periods of human gestation of 0-2.5 wk, 2.5-6 wk, 6-12 wk, and 12-38 wk, respectively. Doses to fetal tissues from 239Pu were calculated for chronic ingestion by the mother for a total of 1.8 kBq 239Pu during the year of pregnancy, giving a committed effective dose to the mother of 1 mSv. On this basis, the total in utero dose to hemopoietic tissue was about 2 microSv compared with red bone marrow doses of 34 microSv to the mother for the year. The yolk sac and bone marrow dominated in utero doses. The total dose to hemopoietic tissue in the offspring to age 70 y, taking into account the activity present at birth and including in utero doses, was estimated as 24 microSv compared with a maternal dose to red bone marrow of 2.5 mSv. An acute maternal intake of 1.8 kBq by ingestion during the period of yolk sac hemopoiesis would result in the highest in utero dose, estimated at about 36 microSv. However, activity at birth would be lower, giving only a small additional dose.     

Measurements of occupational exposure for a technologist performing 18F FDG PET scans

Radiation doses to one PET technologist performing 100 18F FDG (18F fluorodeoxyglucose) imaging procedures were measured in a clinical setting using two types of thermoluminescent dosimeter (TLD) badges, one finger-ring TLD and one electronic pocket dosimeter (EPD). 18F FDG was handled either with unshielded or with viewing window tungsten shielded syringes. The resulting doses using unshielded syringes were 13.8 +/- 0.8 microSv/370 MBq and 14.3 +/- 0.4 microSv/370 MBq, measured with TLD 100 and with TLD 700H/600H, respectively. For the same series of measurements, the doses obtained using shielded syringes were 10.7 +/- 0.4 microSv/370 MBq and 7.2 +/- 2.1 microSv/370 MBq with TLD700H/600H and with EPD, respectively. The dose to the right hand from shielded syringes was 69.3 +/- 5.5 microSv/370 MBq. All these values are within the ICRP recommended dose limits. Extrapolated to 725 examinations per year, the resulting effective dose measured with TLD would be 10 mSv with unshielded and 7.5 mSv with shielded syringes, respectively (25% dose reduction). The doses measured by TLD were consistently higher than those measured by EPD, suggesting that EPD measurements might underestimate occupational doses.     

Radioactivity concentrations and dose assessment for soil samples around nuclear power plant IV in Taiwan

Activity concentrations and distributions of natural and man-made radionuclides in soil samples collected around nuclear power plant IV, Taiwan, were investigated for five years to assess the environmental radioactivity and characterisation of radiological hazard prior to commercial operation. The activity concentrations of radionuclides were determined via gamma-ray spectrometry using an HPGe detector. Data obtained show that the average concentrations of the (238)U and (232)Th series, and (40)K, were within world median ranges in the UNSCEAR report. The (137)Cs ranged from 2.46 +/- 0.55 to 12.13 +/- 1.31 Bq kg(-1). The terrestrial absorbed dose rate estimated by soil activity and directly measured with a thermoluminescence dosemeter (excluding cosmic rays), and the annual effective doses, were 45.63, 57.34 nGy h(-1) and 57.19 microSv, respectively. Experimental results were compared with international recommended values. Since the soil in this area is an important building material, the mean radium equivalent activity, external and inhalation hazard indices and the representative level index using various models given in the literature for the study area were 98.18 Bq kg(-1), 0.27, 0.34 and 0.73, respectively, which were below the recommended limits. Analytical results demonstrate that no radiological anomaly exists. The baseline data will prove useful and important in estimating the collective dose near the new nuclear power plant under construction in Taiwan.     

Age-dependent dose assessment of 226Ra from bottled water intake

Water may present a source of prolonged exposure to naturally occurring radionuclides. One of the most frequently occurring radionuclides in natural mineral and spring waters is 226Ra and its decay products. The contribution of drinking water to the total exposure is very small, at about 5% of the average effective dose attributable annually to natural background radiation, but that exposure contributes to the risk of adverse health consequences. In this study the mean values of 226Ra concentration determined in natural mineral and spring bottled waters range from 6 to 412 mBq L(-1), which is in accord with Croatian legislation. 226Ra effective doses per year from spring water consumption range up to 86 microSv, while 226Ra effective doses per year from mineral water consumption show much higher values. The highest 226Ra effective doses per year from mineral waters consumption, which are up to seven times higher than the dose recommended by WHO (100 microSv), were found in infants and teens. Based on this study, drinking of certain brands of bottled mineral water is not recommended for these age groups because assessed 226Ra effective doses per year exceed the recommended limits. From other research it is known that testosterone appears in elevated concentration during these life periods and affects bone calcification. Therefore, testosterone could affect the retention of 226Ra into the bone. To make more precise conclusions further research is necessary. Adults and especially elderly people are much less susceptible to the presence of 226Ra. According to the results obtained in this study, 226Ra effective doses per year assessed for these age groups were considerably lower (i.e., 10 microSv).     

Naturally occurring radioactive material from the aluminium industry--a case study: the Egyptian Aluminium Company, Nag Hammady, Egypt.

The activity concentrations and the gamma-absorbed dose rates of the terrestrial naturally occurring radionuclides (226)Ra and (232)Th were determined in samples of bauxite, alumina and aluminium dross tailings industrial waste (used to produce two types of alums) using high purity germanium (HPGe) gamma ray spectrometry. The bauxite and alumina are imported by Egyptalum (The Egyptian Aluminium Company, Nag Hammady, Egypt) from Guinea and India. The activity concentrations in the bauxite range from 29 +/- 1 to 112 +/- 6 Bq kg(-1) for (226)Ra, and 151 +/- 8 to 525 +/- 12 Bq kg(-1) for (232)Th, with mean values of 62 +/- 8 and 378 +/- 50 Bq kg(-1), respectively. With respect to alumina and tail, the mean values are 5.7 +/- 1.1 and 8.4 +/- 0.8 Bq kg(-1) for (226)Ra and 7.2 +/- 1.6 and 10.7 +/- 1.2 Bq kg(-1) for (232)Th. Potassium-40 was not detected in any of the studied samples. The measured activity concentrations of (226)Ra and (232)Th in bauxite are higher than the world average while in alumina and tail they are lower. As a measure of radiation hazard to the occupational workers and members of the public, the Ra equivalent activities and external gamma dose rates due to natural radionuclides at 1 m above the ground surface were calculated. The external gamma-radiation doses received by the Egyptalum workers are 97, 409, 8.5 and 12.7 microSv y(-1) for the Guinean and Indian bauxite, the alumina and tail, respectively, which is well below the recommended allowed dose of 1 mSv y(-1) for non-exposed workers.     

A survey of background radiation dose rates and radioactivity in Tanzania.

Potential terrestrial sources of naturally occurring elevated radiation levels have been identified in Tanzania. Thus, efforts are currently being undertaken to create a natural radiation database, in the form of a radiation level map of natural radioactivity, to be used to assess the associated radiation risk to public and workers. Background radiation dose rate was determined with thermoluminescent dosimeters for 7 y (1993-1999) in five stations. The average background radiation dose rates for these stations were as follows: Tropical Pesticides Research Institute (TPRI) (102 +/- 7 nGy h(-1)), Same (98 +/- 2 nGy h(-1)), Namanga (98 +/- 5 nGy h(-1)), University of Dar Es Salaam (99 +/- 2 nGy h(-1)), and Kilimanjaro Christian Medical Center (121 +/- 3 nGy h(-1)). These stations were found convenient from an economic point of view since the project has no funds to cover wider and/or more remote areas in Tanzania. For the sake of comparison, similar measurements were made for the same period at Minjingu phosphate mine. The mine was one of the suspected areas with elevated levels of natural radioactivity. The radiation dose rate measured in this mine was about fourteen times higher (1,415 +/- 28 nGy h(-1)) than the average value obtained in northern Tanzania (98 nGy h(-1)). The high average activity levels of phosphate (5760 +/- 107 Bq kg(-1) for 261Ra, 497 +/- 5 Bq kg(-1) for 228Ra, 350 +/- 6 Bq kg(-1) for 228Th, and 280 +/- 5 Bq kg(-1) for 40K) and radiation dose rate recorded show that Minjingu phosphate mine has higher values than the highest radioactivity in phosphate compiled by the United Nations Scientific Committee on the Effect of Atomic Radiation. In view of these findings, a comprehensive risk-management strategy for reduction of radiation risk to the public and mine workers should be put in place. Efforts are currently being made to seek support to improve the background radiation database for subsequent assessment of radiation risk to miners and the societies in the vicinity of these mines in Tanzania.     

External doses to humans from 137Cs in soil

Calculations of absorbed doses in organs of the human body and the total effective dose due to Cs in soil as a source of external exposure are presented in this work. Calculations were done using the MCNP-4B software package. The assumption was made that photons with an energy of 662 keV are emitted in a cylindrical volumetric source in soil up to the depth of 20 cm. Depth distributions of Cs at 19 locations around Kragujevac (a city in central Serbia) were measured by a HPGe detector. An ORNL phantom of an adult human standing on the soil above the center of a cylindrical radioactive source was used to calculate the conversion coefficients, i.e., absorbed doses in an organ per unit specific activity. The conversion coefficients in organs are given as a function of the source depth in soil. The largest absorbed dose was found in skin. The annual effective dose in humans was estimated from these calculations and the measured activity depth profile of Cs in soil. The average effective dose was found to be 3.17 microSv y. This value was rather small in comparison with other sources of natural ionizing radiation. One may conclude that Cs was a negligible source of external exposure in the area around the city.     

Assessment of natural radioactivity and radon exhalation rate in Sannur cave, eastern desert of Egypt.

Activity concentrations of 238U, 232Th and 40K in rocks and soil samples collected from Sannur cave, Beni Suef governorate, eastern desert of Egypt, were determined using the high-resolution gamma spectrometry technique. The results show that the concentrations of the naturally occurring radionuclides are the following: 238U ranged from 8.51 +/- 1.23 to 20.66 +/- 2.12 Bq kg(-1), 232Th ranged from 7.69 +/- 1.02 to 22.73 +/- 1.60 Bq kg(-1) and 40K ranged from 185.74 +/- 0.42 to 2084.70 +/- 23.30 Bq kg(-1). The radium equivalent activity (Raeq), the absorbed dose rate (D), and the external hazard index (Hex) were also calculated and compared to the international recommended values. The radon concentration and radon exhalation rate from the rock and soil samples were measured using the Can technique. The average value of annual effective dose for cave workers is 1.98 mSv y(-1), while for visitors it is 2.4 microSv per visit. The radon exhalation rate varies from 0.21 +/- 0.03 to 1.28 +/- 0.02 Bq m(-2) h(-1). A positive correlation has been observed between uranium content and radon exhalation rate.     

Fission track estimation of uranium concentrations in drinking water from Azad Kashmir, Pakistan

The analysis of uranium in water samples can be very helpful for providing guidelines to the general public regarding necessary remedial measures. A fission-track technique has been applied for the estimation of the uranium concentration in drinking water collected from natural springs of Muzaffarabad and hilly areas of Reshian, Azad Kashmir. The technique involved simultaneous irradiation with thermal neutrons of a sample and a standard in contact with a track detector, and the counting of the fission tracks in the detector from the (n, f) nuclear reaction. Uranium concentrations of the samples were determined by comparing fission-track density with that of a standard of known uranium concentration. Uranium concentration in water samples from the Muzaffarabad and Reshian area varied from 0.03 +/- 0.01 microgL(-1) to 6.67 +/- 0.14 microgL(-1) with an average of 1.36 +/- 0.05 microgL(-1). The observed concentrations of uranium in drinking water were found to be less than the Maximum Acceptable Concentration levels of 9-30 microgL(-1). Thus, the observed values are within safe limits as far as uranium related health hazards are concerned.     

Neutron field measurements at the Aladdin Synchrotron Light Source

The neutron field near the inflector of the 800-MeV electron storage ring was studied. Photon-induced neutrons are produced by 100-MeV electrons bombarding the inflector during injection into the synchrotron ring. Neutrons were measured with moderating detectors made of 15 X 15 X 20 cm Lucite blocks and Au activation foils. Detector response was established with a Pu-Be neutron source and a 25.4-cm polyethylene sphere and Au foil detector. The neutron yield was 0.97 +/- 0.14 X 10(12) kJ-1. For 1.38 W of electron pulse power, the dose equivalent rate 1 m aside and 1 m above the inflector was 4.35 +/- 0.47 mu Sv s-1 and 3.13 +/- 0.23 mu Sv s-1, respectively. A measured dose equivalent transmission curve for polyethylene yielded an attenuation coefficient of 15.7 m-1.