Meta-Study of Particulate Detection Losses on Radioactive Air Sample Filters

Several mathematical relationships between air sample filter mass loading and the correlated analytical self-absorption factor were developed using data from other published research in this meta-study. Gross-alpha and -beta applications are addressed for this research. As filter media becomes loaded with particulate matter, there is potential for measurement losses due to self-absorption by mass loading. Components contributing to absorption include particulate dust, radioactive particulates, and filter material. Standards indicate a correction factor should be used when the penetration of radioactive material into the collection media or self-absorption of radiation by the material collected would reduce the detection rate by more than 5%. Previously, losses due to self-absorption have been reported up to 100% over a range up to ~10 mg⋅cm-2 mass loading. These absorption losses then can be used to determine a correction factor for sample results. For low mass loadings (e.g., ≤0.1 mg⋅cm-2) corrections factors in the 0.85 - 1 range have been recommended and used, while at higher mass loadings nearer to 10 mg⋅cm-2 correction factors closer to 0 (representing near 100% losses) are used. Based on data from published studies, the different methods for relating percent loss due to self-absorption to mass loading include linear, exponential, quadratic, and trinomial derived functions. Where applicable, both forced zero and non-forced zero results were evaluated. From the derived functions evaluated, the trinomial function provided the best fit. Once the sample filter mass loading is known, the trinomial function can be applied to estimate losses and the corresponding self-absorption factor. When applied to routine operating conditions for radiological facility stacks monitored at the Pacific Northwest National Laboratory for an average sample filter mass loading of 0.09 ± 0.12 (2σ) mg⋅cm-2 (excluding negative values and outliers) and a range from 0 - 0.24 mg⋅cm-2, the estimated trinomial function nominal self-absorption losses are less than 5% at 0.09 mg⋅cm-2 and less than 10% at 0.24 mg⋅cm-2. The trinomial function is one method that may be used to adjust the activity results of an air sample when the sample-specific mass loading is determined. The application of no correction factor when the ANSI/HPS N13.1-2021 guidance of a 5% threshold for loss is not reached with typical stack sample mass loadings may be reasonable in high-efficiency particulate air filtered systems. For simplicity, it would be conservative in assigning the self-absorption correction factor at the 5% threshold (i.e., 0.95) for general uses but in cases of heavy mass loading to calculate the factor.

Assessment of Radiation Hazard from External and Internal Exposures at Adham and Surroundings in KSA

Twenty-eight environmental samples (eight well water, sixteen granitic rocks and four soils) were collected from different parts of Adham governorate (Adham, Haqal and Al-Jaizah), to assess the radiological hazard and cancer risk from different perspectives. Adham is situated in a valley between two granitic mountain chains, where much of water supply for drinking, house use and irrigation comes from wells collecting water rains. The activity concentrations of naturally occurring 40K, 226Ra and 232Th and radionuclides were measured by gamma-ray spectrometry for all samples using RGK-1, RGU-1 and RGTh-1, IAEA reference standards issued by the International Atomic Energy Agency, for detector efficiency calibration. The measured values were utilized to evaluate the internal and external exposures both outdoors and indoors. Different standard room models were adopted for this respect to evaluate the indoor gamma-rays exposure from construction materials as well as internal exposure to radon gas emanating from them. Radon concentration indoors, exceeded the upper reference level in dwellings set at 300 Bq/m3 by the world health organization, in many scenarios. The mean value of the total excess lifetime cancer risk (due to external exposure from gamma-rays) was 2.29 × 10-3, above the world average value of 1.45 × 10-3. Furthermore, the measured radon concentrations in all water samples exceeded the EPA (Environmental Protection Agency) 11.1 Bq·L-1 standard for drinking water, ranging from 12 to 38 Bq·L-1 with a mean value of 27 Bq·L-1. The total annual effective dose (due to inhalation and ingestion) from radon in water, ranged from 58 to 192 μSv/y (for adults) exceeding the international permissible limit of 100 μSv/y, in seven out of eight samples. According to obtained results, the internal exposure from radon in directly used water from wells, might be the major reason of any suspected radiological health hazard especially in Haqal. The second reason might be the internal exposure from indoor radon gas inhalation in poorly ventilated dwellings.

Activity Concentrations and Associated Gamma Doses of 238U and 235U in Jordan

In this study, sixteen soil and vegetable samples from Tafila district were collected and analyzed from eight locations. Measurements of specific activity of natural gamma emitter radionuclides, 23SU and 235U, in these samples using gamma spectrometry, with the help of Genie 2000 software. Measurements were used to calculate the soil-vegetable transfer factor, and then the external radiation dose and internal radiation dose due to radioactivity of the ingested food. The specific activity of238U and 235U in soil were found to vary from （in Bq/kg）： 26-575 and 1.4-35.5, respectively. The specific activity of 238U and 235U in vegetables were found to vary from （in Bq/kg）： 0.019 to 0.632 and 0.0013-0.0375, respectively. The calculated transfer factor of Z3SU and Z35U range from 5.9 × 10^-4to 14.6 × 10^-4 for 238U and 4.9 × 10^-4 to 16.1 × 10^-4 for 235U. External absorbed dose rates were calculated to be in the range from 12.42 to 266.00 nGy/h. The annual effective dose was found to vary from 28.94 to 619.78 μSv/y. The annual internal effective dose due to 23SU and 23SU for fresh weights ofvegetablesl were found to vary from 0.9 × 10^-3 to 35.1 × 10^-3 μSv/y for 238U and 0.61 × 10^-4 to 17.62 × 10^-4 μSv/y for 235U.

Radiological Hazard Assessment of Raw Granites from Ranyah, KSA

The assessment of radiological hazard due to external and internal indoor exposure was investigated for 26 raw granites collected from different granite quarries in Ranyah (KSA). The activity concentrations of 226Ra, 232Th and 40K were measured by high-resolution gamma spectrometry. Four granites were classified as “anomalous” due to their relatively high radioactivity. The averages and ranges of their activity concentrations were 667 (305 - 1120), 320 (161 - 491) and 586 (282 - 893) Bq·kg-1, respectively. The corresponding ones for all remaining 22 granites were 45 (18 - 77), 39 (16 - 73) and 1178 (954 - 1531) Bq·kg-1, respectively. In accordance with new European Basic Safety Standards (BSS) directives requiring a uniform reference level for indoor external exposure to gamma rays of 1 mSv·y-1, all 22 granites may be used as bulk or ornamental building materials without any restrictions. Three anomalous granites should be subjected to control to be used as bulk materials. One anomalous granite was categorized as hazardous having an activity concentration index higher than 6. All four anomalous granites exceeded the level of newly adopted reference level of 300 Bq·m-3 for radon indoor exposure in case of poor ventilation. Two of them exceeded even for adequate ventilation. ·