Solid State Alpha Detector Research Articles

Removal of Radioactive Gas by Zeolite Filter From Nuclear Power Plants

During the normal operation of nuclear power plants, some radioactive wastes are produced in the form of particles or aerosol gas in the reactor building. Particulate radioactive aerosols can be produced in a wide variety of particle sizes, possibly in combination with non-radioactive aerosols. Emission of corrosion products and fission products that are activated by the effect of nuclear rays generate aerosols from two sources. These; are created by the adsorption of gases generated by radioactive decay and volatile radionuclides formed during the fission process on the present suspended material. The most important volatile radionuclides that form the gaseous radioactive waste produced during the normal operation of nuclear power plants are halogens, noble gases, tritium, and carbon-14. The composition and amount of radioactivity present in the various airborne waste streams depend largely on the reactor type and release path. All gaseous waste from nuclear power plants must be treated before discharging into the atmosphere. In this paper, radioactive radon gas was used to represent the radioactive gases generated from nuclear power plants and natural zeolite was used as adsorbent material for radon removal. A series of experiments were conducted to measure the performance of the filter made in the zeolite. First of all, an approximate particle distribution size in the range of 1 to 3 mm was obtained by grinding natural zeolite. The ground material was then compressed in cylindrical adsorbent moulds of 35 mm diameter and 10 mm height. After the moulds were filled with the material, they were dried by heating to 110 ° C for 24 hours. At the end of the heat treatment, the adsorbent beds were cooled and connected to the test apparatus. RAD7 radon test device was used in the experiments. The RAD7 is a portable instrument that uses a solid-state alpha detector to measure radon gas concentrations in the range of 4.0-750,000 Bq / m3. The sampler of the RAD7 device works by drawing an air sample from an inlet filter into a 0.7 L sample cell covered with an electrical conductor. At the centre of the hemisphere, the cell is a planar silicon detector implanted with an ion to measure radioactivity. As result of the experiments, it shows that the zeolite filter absorbs 85% radioactive radon gas and can be used as an air filter in nuclear power plants.

Radon concentration measurement in water reservoirs for some areas of north Baghdad by RAD7

Radon is a naturally occurring, odorless, colorless, radioactive, tasteless, and noble gas. Radon concentrations have been measured by the usage of alpha spectroscopy (RAD-7). The RAD-7 measuring process is based on detecting alpha particles produced from the disintegration of radon and its products using a solid-state alpha detector (usually silicon), and then converting alpha radiation directly to an electrical signal. The radioactivity of radon gas was measured in forty-two samples from reservoir water for different areas north of Baghdad utilizing a RAD7 detector. This study proved that the high value of radon concentrations was less than the permissible limit as recorded by the World Health Organization.

Radon Concentrations in a Nuclear Reactor Center in Brazil.

Radiation workers are normally exposed to doses resulting from their day-to-day activities. Besides that, background radiation, such as radon, can contribute to the exposure rates. The radionuclide 222Rn is a noble gas belonging to the uranium series, and its indoor concentration in the air depends on the exhalation from surrounding soil and the exhalation from building materials. Radon exhaling from porous building materials containing high uranium concentrations can become a significant exposure factor in areas with limited ventilation. The objective of this study was to evaluate the 222Rn concentrations in the radiochemistry and radiometric laboratories in the nuclear reactor building of the Nuclear Reactor Center (CERPq) located in the Institute of Nuclear and Energy Research (IPEN), São Paulo, Brazil. Measurements were done using a Radon Gas Monitor, model RAD7, equipped with a solid-state alpha detector. A passive method (SSNTD) was also used, consisting of square pieces of C-39 foils (2.5 cm × 2.5 cm) placed within small diffusion chambers. The CR-39 detectors were etched in KOH 30% solution at 80 °C for 5.5 h in a constant-temperature bath. After etching, the detectors were washed, dried, and scanned using a microscope to obtain the track density measurements. The activity concentrations measured with both techniques varied from 52 to 103 Bq m-3 in the studied areas of the CERPq. These values may be compared to the reference level of 100 Bq m-3 established by the World Health Organization to ensure safety environments.

Age-Dependent Health Risk Assessment for Radon Concentrations from Drinking Water Available in the Iraqi Markets

Radon is occurring naturally, odorless, colorless, radioactive, tasteless, and a noble gas. It is the second most important cause of lung cancer after smoking in many countries. The rate of lung cancers attributable to radon is estimated to range from 3 to 14%. The dose exposure relation is linear, i.e. the risk of lung cancer increases proportionally with increasing radon exposure. So, it is necessary to measure radon concentrations in the drinking water that is of direct contact with human life and health. The study included measurement of radon (222Rn) concentrations in some selected samples of drinking water (bottled water) are available in the Iraqi market. 222Rn concentrations have been measured the usage of alpha spectroscopy (RAD-7). The RAD-7 measuring process is based on detecting alpha particles produced from the disintegration of radon and its products using a solid-state alpha detector (usually silicon), and then converting alpha radiation directly to an electrical signal. The annual effective dose and lifetime cancer risk in six age groups (3 months, 1 year, 5 years, 10 years, 15 years and adult) associated with the exposure due to an annual intake of 222Rn were calculated. Results show that the average value of radon concentrations in drinking water samples was ranged from 28.4±2.7 mBq/L to 283±0.34 mBq/L. Also, it is found the average value of annual effective dose in unit µSv/y for six age groups were 0.48±0.08, 0.62±0.11, 0.18±0.03, 0.22±0.04, 0.37±0.06, and 0.27±0.05, respectively. The average value of lifetime cancer risk in same age groups were (17.99±3.26, 31.13±5.65, 46±8.37, 107.33±19.41, 276.5±50, and 926.33±168)×10-9 respectively. The results of 222Rn concentrations in the present study were found lower than the data of the recommended reference WHO 2008 (500 mBq/L or Bq/m3). Also, the results showed that the annual effective dose from drinking water exhaustion in six age groups were found lower than the permitted limit of (1mSv) suggested by UNSCEAR 2000. As well as, values of lifetime cancer risk were within the accepted level (10-3). Therefore, there are no indications of significant threat from radon concentrations in bottled water brands, and it is safe as far as a health risk is concerned.

Study of radon/thoron exhalation rate, soil-gas radon concentration, and assessment of indoor radon/thoron concentration in Siwalik Himalayas of Jammu & Kashmir

ABSTRACTIn the present study, the soil-gas radon concentration was assessed at different depth intervals, i.e., 15 cm, 30 cm, 60 cm, and 100 cm from the 30 villages of Jammu & Kashmir, India using RAD7, an electrostatic solid state alpha detector. The radon mass exhalation and thoron surface exhalation rate has also been measured in the selected 18 soil samples out of 30 of different grain sizes (i.e., 1 mm, 300 µm, 150 µm). The active radon and thoron concentrations were also assessed in the 20 villages. Both the exhalation rates and active radon/thoron concentration were measured using SMART Rn Duo, a portable radon monitor. The average values of soil-gas radon concentration were 210 ± 84 Bq m−3, 1261 ± 963 Bq m−3, 4210 ± 1994 Bq m−3, and 671 ± 305 Bq m−3 at the depth intervals of 15 cm, 30 cm, 60 cm, and 100 cm, respectively. The exhalation rate of radon and thoron from soil was found to decrease with the increase of grain size, as smaller soil particles make relatively more contribution to radon and thoron exhalations from the ground surface than larger soil particles. The measured Pearson's correlation coefficient was obtained as statistically significant between different quantities under two-tailed test.

Assessment of Radiation Dose from Exposure to Radon in Drinking Water from Western Haryana, India

The radon concentration has been determined in 95 groundwater samples collected from 28 villages/towns in the Hisar district of Haryana, India. The measurements were performed by RAD7, an electronic solid-state alpha detector manufactured by Durridge Company Inc. The measured mean radon concentration in water samples ranged between 1.4 ± 0.3 and 13.3 ± 4.1 Bq l−1. The mean radon concentrations from three locations exceeded the maximum contamination level (MCL) of 11 Bq l−1 recommended by United States Environmental Protection Agency. The annual effective dose for ingestion and inhalation was also evaluated in this research. The total annual effective dose due to ingestion and inhalation of radon in drinking water ranged from 13.7 to 130.3 µSv year−1.

A General Survey of Radon Concentration in Water from Rivers in Gauteng, South Africa Using a Solid-State α-Detector

In view of the geological setup and the long-standing mining history of the Gauteng Province, South Africa, it is expected that the mine dumps around the gold mines could contribute to a significant radium (226Ra) concentration in water in Gauteng Province. Radium decays to its daughter radioisotope radon (222Rn) which is a potential source of radiation exposure to the general public. Radon-222 easily escapes from surface of mineral grains and it becomes dissolved in ground water, rivers and dams which are ultimately used by the public. The research study was carried out to determine the effective dose (mSv) to the general public from radioactive (222Rn) in the water from 25 rivers and tributaries in the surrounding areas of Krugersdorp, Johannesburg, Pretoria and Vaal regions. Water samples were collected from the rivers and analysed in the laboratory at Necsa in Pretoria. An α - spectrometry analysis using a solid-state alpha detector (RAD-7) was optimized to measure (222Rn) in the water by counting α - particles emitted by 218Po and 214Po in secular equilibrium with their parent, (222Rn). The measured (222Rn) concentrations ranged from 1.4 × 10-1 to 3.56 Bq.l-1 with an average of 1.43 ± 4.3 × 10-1 Bq.l- 1. The average annual effective dose was found to be 4 × 10-3 μSv. The study showed that 222Ra concentration in river water from Gauteng is lower than international acceptable limits cited in the United States Environmental Protection Agency and the World Health Organisation of 1.11 × 10-1 Bq.l-1 and 1.0 × 10-2 Bq.l-1 respectively. The average effective dose is negligible (about 0.32%) as compared to the worldwide average annual effective dose from inhaled 222Rn of 1.26 mSv. Hence, the effective dose of 4 × 10-3 μSv does not pose any health threat to the general public that use water from Gauteng Rivers.

Chapter 15 Diffuse soil emanations of radon and hazard implications at Furnas Volcano, São Miguel Island (Azores)

Abstract Furnas Caldera Volcanic Complex, São Miguel Island (Azores), last erupted in 1630 and is famous for its intense hydrothermal activity (i.e. fumarolic fields, thermal springs, cold CO 2 -rich mineral waters and diffuse CO 2 soil emanations), which directly affect the villages of Furnas and Ribeira Quente. Here we report the first systematic investigations and mapping of soil radon ( 222 Rn) emanations in the Furnas Volcanic Complex, and we examine their potential health risks for local inhabitants. 222 Rn in volcanic soils (60 cm depth) was repeatedly measured between 2005 and 2010 using a portable solid-state alpha detector (RAD7, Durridge Company Inc.). Results reveal a local background of 8000 Bq m −3 and several areas with anomalously high 222 Rn activity (up to c. 400 000 Bq m −3 ), which coincide with advective or convective gas transport through volcanic structures and active fault zones. High 222 Rn radioactivity in Furnas and Ribeira Quente villages represents a risk to the population. Continuous monitoring performed during November and December 2005 in a house in Furnas shows indoor 222 Rn reaching 13 273 Bq m −3 , two orders of magnitude greater than the reference level (150 Bq m −3 ), when the ventilation efficiency is reduced.

Estimation of annual effective dose due to Radon level in indoor air and soil gas in Hamirpur district of Himachal Pradesh

Indoor air and soil gas radon measurements are simultaneously performed in Hamirpur district of Himachal Pradesh using RAD7, a solid state alpha detector. The study is performed for the estimation of radon level and annual effective dose for indoor air. Different locations are selected and it is found that the variation of radon concentration in indoor air and soil gas in Hamirpur region ranges from 35Bqm−3 to 956Bqm−3 and 35 to 2280Bqm−3 having mean values 189.43Bqm−3 and 462.56Bqm−3 respectively. From indoor air, the total annual effective dose is calculated and it varies from 0.88mSvy−1 to 24.09mSvy−1 with mean value of 4.77mSvy−1. In general, it is found that the annual effective dose limit was within the recommended reference level (3mSvy−1to 10mSvy−1) of the world organisations. A good correlation between radon concentration in air and soil gas is observed.

Measurement of 222RN concentration in drinking water in Sakarya, Turkey

In this paper, the first measurement of (222)Rn concentrations in drinking water from wells, springs and bottled waters in the city of Sakarya, Turkey was presented. The measurements were performed using RAD 7, a solid-state alpha detector, with RAD H2O (radon in water) accessory manufactured by Durridge Company, Inc. The measured activity concentrations ranged from 1.98 to 20.80 Bq l(-1) with an average value of 9.05 Bq l(-1) for well water, from 0.75 to 59.65 Bq l(-1) with an average value of 13.78 Bq l(-1) for spring water and from 0.75 to 22.8 Bq l(-1) with an average value of 5.41 Bq l(-1) for bottled water. Although these results indicated relatively high (222)Rn concentrations compared with that from other parts of the Turkey, they are still below the World Health Organization recommended level of 100 Bq l(-1) for radon. Using the measured activities of (222)Rn, the age-dependent associated committed effective doses due to the ingestion of (222)Rn as a consequence of direct consumption of drinking water were calculated. The committed effective doses from (222)Rn were estimated to range from 2.59 to 205.97 µSv y(-1), from 1.55 to 123.28 µSv y(-1) and from 1.31 to 104.48 µSv y(-1) for age groups 1-2, 8-12 and >17 y, respectively.

Gamma versus alpha sensors for Rn-222 long-term monitoring in geological environments

Abstract The behavior of alpha silicon diodes, gamma crystal scintillators and ionization chamber detectors employed for long-term radon monitoring in geological media was studied and a comparison of the efficiency and sensitivity, the capability to resolve signal to noise, background, stability, and reliability of their long-term measurements is presented. An understanding of the qualities of monitoring techniques is necessary for determining suitability to the characteristics of the individual monitoring site and what exactly they will measure: radon in an air cavity, in porous media or in water. The experimental layout was located inside the Amram Mountain research tunnel near Elat (Gulf of Aqaba), within a closed room in the tunnel core. This enabled monitoring natural temporal radon variations under fairly stable internal conditions, at a high-resolution sampling rate of once every several minutes. In an interval of several days, all the sensors responded simultaneously to the same eventual radon variations. An ionization chamber device, the AlphaGUARD designed with a long-time stable calibration factor and an inherent QA-System, was used as reference calibration of the different radon detectors. The results indicate that the higher sensitivity of 2–4 orders of magnitude exhibited by gamma sensors even with narrow dimensions (1 × 3 BGO detector) are preferred for long-term radon monitoring in comparison to the solid-state alpha detectors and ionization chambers.

A simple technique for studying the dependence of radon and thoron exhalation rate from building materials on absolute humidity

Indoor radon and thoron concentrations were dominated with their exhalation rate from building materials. Thus, the evaluation of exhalation rate with highly precise is important. This paper presented a new technique to measure the dependence radon/thoron exhalation rate, from building materials used in Japan, on absolute humidity. The measurement technique consisted of a solid state alpha detector equipped a ventilation-type chamber and humidity control system in a flow through method. The exhalation rate of dried samples (Indian red granite and Japanese gray granite) was measured at various absolute humidity levels in the range of 1–20 g cm−3. It was found that exhalation rate increased exponential with increasing of absolute humidity for both samples. Furthermore, the dependence of radon emanation coefficient on building material’s temperature was also studied using an accumulation chamber equipped with scintillation cell alpha detector. The emanation coefficient of dry sample increased proportionally with increasing the material’s temperature with a correlation factor of 0.88.

Estimation of mean annual effective dose through radon concentration in the water and indoor air of Islamabad and Murree

Different samples of water, indoor air and soil gas have been collected from Islamabad (33 degrees 38'N, 73 degrees 09'E, altitude of 1760 ft.), the capital of Pakistan and Murree (33 degrees 53'N, 73 degrees 23'E, altitude of 7323 ft.), lying on a geological fault line and are analysed for the estimation of mean effective dose through radon concentrations by using RAD-7, a solid state alpha-detector. The variation of radon concentration in water, indoor air and soil gas in Islamabad region ranges from 25.90-158.40 kBq m(-3), 43.26-97.04 Bq m(-3) and 17.34-72.52 kBq m(-3), having mean values 88.63 kBq m(-3), 70.67 Bq m(-3) and 45.08 kBq m(-3)(,) respectively. It ranges from 1.64-10.20 kBq m(-3), 18.48-42.08 Bq m(-3) and 0.61-3.89 kBq m(-3) with mean values 4.38 kBq m(-3), 28.63 Bq m(-3) and 1.70 kBq m(-3)(,) respectively in Murree and its surroundings. The total mean annual effective doses from water and indoor air of Islamabad and Murree regions are 2.023 and 0.733 mSv a(-1), respectively. These doses are within the recommended limits of the world organisations.

Simultaneous determination of 222Rn and 220Rn exhalation rates from building materials used in Central Italy with accumulation chambers and a continuous solid state alpha detector: Influence of particle size, humidity and precursors concentration

A method to determine simultaneously the rates of 222Rn and 220Rn released from building materials quarried in Central Italy is presented. The method makes use of a continuous monitor equipped with a solid state alpha detector, in-line connected to a small accumulation chamber. The effects of chamber leakage and back diffusion on 222Rn free exhalation rate is evaluated. The influence of available exhalation surface, humidity content and precursors concentration on radon and thoron exhalation rates is investigated.

A Transuranic Aerosol Measurement System: Preliminary Results

We have completed the design, fabrication, and assembly of a computer-based prototype system for the measurement of transuranic aerosols in the workplace and environment. This system (called WOTAMS for Workplace Transuranic Aerosol Measurement System) incorporates two detectors: (1) an in-line solid-state alpha detector that sends out an alarm the moment a transuranic release occurs, and (2) an in-vacuum detector that increases off-line-analysis sensitivity. The in-line sensitivity of the system is better than 5.0 MPC-h, and the in-vacuum sensitivity exceeds 0.5 MPC-h.

Circuit analysis of the Harwell solid state alpha detectors

The Harwell SRD range of alpha particle detectors are p-n junction devices. The junction lies close to the surface of a silicon wafer and the junction area includes not only one face of the wafer but also the edge and a narrow rim on the opposite face. An equivalent circuit has been devised for the SRD diode; a simple distributed network of resistors and capacitors. It is not only consistent with the physical structure of the diode but also accounts adequately for the electrical characteristics. If the network is represented by a single resistance in series with a single capacitance, both of these quantities are noticeably frequency dependent above about 50 kHz.

The NBS 14 MeV Absolute Neutron Beam Facility

A 14 MeV absolute neutron beam has been established at the NBS 3 MV positive-ion Van de Graaff Accelerator Laboratory. The T(d,n)? reaction is used for the production of the 14.1 MeV neutron flux with a source strength of 108 n/sec. The neutron flux is absolutely determined by the measurement of the associated alpha particle rate in a silicon surface barrier detector positioned at 84 degrees with respect to the beam axis. The facility may be used to measure the absolute response of active neutron monitoring devices with high accuracy. The neutron background contributions may be eliminated in the calibration measurements by utilizing the coincidence between the device and the solid state alpha detector. This method allows a neutron flux in a cone of 2 degree half angle to be placed at 90 degrees with respect to the beam axis.

Determination of237Np in urine by reversed-phase partition chromatography

A sensitive, rapid and selective method for the determination of237Np in urine is described. Neptunium(IV) is isolated by batch-extraction with a slurry of Microthene-710 (microporous polyethylene) supporting a cyclohexane solution of tri-n-octylphosphine oxide, the slurry is transferred into a column and neptunium eluted by oxidation to Np(V) with a mixture of HCl+Cl2. After electroplating on a stainless steel disc, neptunium is counted with a solid-state alpha-detector. The final recovery is 83.2%; the decontamination factors are sufficiently high and the sensitivity limit is suitable for radiotoxicological purposes.

Sources and prevention of recoil contamination of solid-state alpha detectors

Sources and prevention of recoil contamination of solid-state alpha detectors

Low Level Alpha Counting with Solid State Detectors

Two instruments are described that utilize the high discrimination of solid state alpha detectors against beta and gamma radiation. An alpha particle survey meter was developed with a 6 cm/sup 2/ sensitive area. It will detect alpha particles in the presence of a 50 r/hr gamma ray field. A low level alpha counter was built with a background of less than 0.00l count per minute. It is useful for measurement of alpha emission from bio-assay samples. (auth)