China
Africa
Explore chapters and articles related to this topic
Radioactivity
Published in W. P. M. Mayles, A. E. Nahum, J.-C. Rosenwald, Handbook of Radiotherapy Physics, 2021
If T1 >> T2, a secular* equilibrium is obtained, and the activities of the parent and daughter radionuclides become equal after several half-lives of the daughter (Figure 2.7b).
Radionuclide Generators
Published in Garimella V. S. Rayudu, Lelio G. Colombetti, Radiotracers for Medical Applications, 2019
This equation is the one most widely used in the study of parent-daughter relationships. It can be simplified in different ways depending on the type of equilibrium reached. In secular equilibrium (the half-life of the parent is much longer than that of the daughter) and if the initial activity of the daughter is zero, Equation 7 can be simplified to
Fundamental Concepts and Quantities
Published in Shaheen A. Dewji, Nolan E. Hertel, Advanced Radiation Protection Dosimetry, 2019
If the daughter’s half-life is less than the parent’s, but not in the extreme, as in secular equilibrium, the daughter will eventually establish transient equilibrium and decay at the same rate as it is produced by the parent. The decay equation for transient equilibrium is found from Equation (2.83) under the assumption that for times sufficiently large is negligible compared to and becomes
Radiological risk assessment of the Hunters Point Naval Shipyard (HPNS)
Published in Critical Reviews in Toxicology, 2022
Dennis J. Paustenbach, Robert D. Gibbons
The cancer slope factors for morbidity selected in the dose model for this risk assessment are those of the DC_PAK version 3.02 (Oak Ridge, TN, USA) software data package in RESRAD-ONSITE (International Commission on Radiological Protection [ICRP] 2008). The slope factors in DC_PAK 3.02 are adopted from the USEPA’s Federal Guidance Report No. 13 and the model uses updated nuclear decay and ingrowth data from ICRP Publication 107 and external dose rate coefficients for surficial soils from the USEPA’s Federal Guidance Report No. 12 (Eckerman and Ryman 1993; Eckerman et al. 1999; ICRP 2008). To account for cancer risk contributions from short-lived progenies, the slope factors of short-lived progenies were added to that of the parent nuclide. The RESRAD-ONSITE model characterized the cancer risk by calculating the amounts of external exposure and intake and applying the slope factors corresponding to the applicable ROC. It was assumed that the decay products were in secular equilibrium with their parent radionuclide at the point of exposure.
Radionuclide concentrations in medicinal florae and committed effective dose through Ayurvedic medicines
Published in International Journal of Radiation Biology, 2020
S. Monica, Panakal John Jojo, Mayeen Uddin Khandaker
Fifty-two medicinal plant parts, used as main ingredients in the most important Ayurvedic medicines were procured in the dried form (water content ranged from 8% to 13% by weight) of roots, stem, seeds, flowers and fruits from local herbalists in Kollam district, Kerala. Percentage of water content was determined from the difference in weight of the sample collected and the oven dried ones. The selection of the medicines and the details of their ingredients were gathered in consultation with Ayurvedic medical practitioners in the Kollam district of Kerala state in India. Category wise pictures of the medicinal plant parts analyzed are shown in Figure 1. All the collected medicinal plant samples were prepared through a standard protocol prior to analysis by gamma-ray spectrometry of natural samples. Initially, samples were dried in a hot air oven at 110 °C to remove the water content and were then made into fine powder through mechanical grinding. The samples in powder form were sieved through a 100 mesh sieve to obtain a uniform and homogenous sample matrix. The powdered samples were transferred into cylindrical containers of specific size and were hermetically sealed. The sealed containers were shelved for three months to achieve secular equilibrium between the short-lived daughter products in the uranium series and those in the thorium series (Tahir and Alaamer 2009; Tettey-Larbi et al. 2013).
Radioactivity in building materials and assessment of risk of human exposure in the East Khasi Hills District, Meghalaya, India
Published in Egyptian Journal of Basic and Applied Sciences, 2020
In the present work, a total number of 53 samples of 7 different kinds of building materials were collected directly from quarry sites and construction sites of different villages of East Khasi Hills District (Figure 1) depending upon their availability. The commonly used building materials selected for our study were gravel (G), sand (S), sand stone (SS), cement brick (CB), tiles (T), redbrick (RB) and cement (C). The samples like gravel, sand, sand stone and cement brick were obtained from the quarries located in the District itself. Other raw materials like tiles and cement were procured from various dealers of the District. The collected samples were kept and sealed in plastic polythene bags, labeled with different code numbers for various types of samples. After transporting to the laboratory, the samples were first dried in an oven at 110°C for 24 hours to ensure that moisture was completely removed. After drying, the samples were crushed to a fine powder of size 74 µm. The dried samples were weighed and stored in an air-tight cylindrical plastic containers (12.5 cm height and 8.2 cm diameter). The containers were then sealed tightly using tape around its screw neck to prevent the escape of radon gasses. The samples were kept for 1 month before spectral analysis was carried out in order to attain a secular equilibrium between 226Ra, 228Th and their daughter products [17].