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Radiation Sources, Exposure, and Health Effects
Published in James H. Saling, Audeen W. Fentiman, Radioactive Waste Management, 2018
James H. Saling, Audeen W. Fentiman
During radioactive decay, an atom is transformed into an isotope of another element. Sometimes that new isotope is stable (not radioactive) and sometimes the new isotope is radioactive. If it is radioactive, it will decay. When one radioactive isotope decays or is transformed into another radioactive isotope which in turn decays, a “decay chain” is formed. A decay chain can contain two or more radioactive isotopes and always ends with a stable isotope.
Nuclei and Radiations
Published in José Guillermo Sánchez León, ® Beyond Mathematics, 2017
The set of all branches produced by the decay of a parent isotope (like Uranium–238) is known as the radioactive decay chain. However, the majority of those disintegrations happen along only one branch. IsotopeData ["isotope", "BranchingRatios"] shows the results after sorting the branches from bigger to smaller in terms of their likelihood of occurrence. When an isotope decays into one or several isotopes, we can choose to keep just one: the one with the highest probability. If we apply this criterium to each daughter isotope, we will end up with a single branch named the main branch. From a practical point of view, in many decay chains it is enough to study the main branch.
Beta-Ray-Bremsstrahlung Contributions to Short-Lived Delayed Photoneutron Groups in Heavy Water Reactors
Published in Nuclear Science and Engineering, 2023
Yanuar Ady Setiawan, Hemantika Sengar, Douglas A. Fynan, Arief Rahman Hakim
An estimate of the bias in the calculated short-lived group yields from fission products without decay scheme data is negative 1% to 10%, reflecting the discussion in Secs. III.B.1 and III.B.2 and Table III. Half-life cut-offs for the groups were somewhat arbitrarily chosen based on legacy group half-lives and to segregate some important long-lived precursors with large individual yields. Fission-product PN yields scaled by χc were assigned by isotope half-life neglecting any decay chain dynamics and shielding by long-lived parent. Interestingly, the original PN study1 explicitly warned of possible decay-chain and parent-feeding influences on measured PN group data, but very few researchers have addressed this issue in PN and direct-delayed neutron studies in the last 30 years when decay chain data have been readily available. Our cursory inspection of decay chains involving PN precursors has found decay-chain dependencies in almost all of the PN groups, including the 100Zr/100Nb, 92Kr/92Rb, 98Sr/98Y, 88Kr/88Rb, 134Te/134I, 138Xe/138Cs, 140Ba/140La, 142Xe/142Cs, and 146Ce/146Pr parent/daughter chains. For simulated PN studies, the cross-section library effect is significant (>10% variation) for the short-lived group yields.
Radiological Characterization with a Fluence Conversion Coefficients–Based Method: A Practical Example of the Preparatory Studies to the Pilot Beam at the CERN Large Hadron Collider
Published in Nuclear Science and Engineering, 2023
Davide Bozzato, Robert Froeschl
where is the Avogadro’s number, is the molar mass of element , is its mass fraction in the considered compound material, is the energy dependent production cross section of radionuclide from element due to particle , and is the fluence energy spectrum of particle . The term in parentheses in Eq. (1) represents the production yield of radionuclide from element . The buildup of radionuclide and the full decay chain leading to isotope are described by the time evolution matrix , which depends on the irradiation history and cooldown time and can be expressed in terms of Bateman’s coefficients.[9]
Simulation of the Nondestructive Assay of 237Np Using Active Neutron Multiplicity Counting
Published in Nuclear Science and Engineering, 2020
Michael Y. Hua, Braden Goddard, Cody Lloyd, Evan C. Leppink, Sara A. Abraham, Jordan D. Noey, Shaun D. Clarke, Sara A. Pozzi
Active interrogation must be used to estimate the mass of an assay sample of Np in hours or less. Passive assays are infeasible due to Np having a low gamma-ray emission rate (2.6 gammas/s/g), low gamma-ray energies (97% of gammas are less than 100 keV), and a spontaneous fission rate of fissions/decay.11 The decay product of Np, which is Pa (half-life of 27 days), is of limited use due to all of the prominent gamma rays consisting of relatively low energy: 300.1 keV (6.6% yield), 311.9 keV (38.5% yield), and 340.5 keV (4.4% yield). Because of the energies, Pa gamma rays are easily shielded by dense, high-atomic-mass materials (including the self-shielding from the Np). The infinite thickness for 340.5-keV gamma rays in Np metal (20.2 g/cm) is 1.025 cm.1 The decay product of Pa is U, which has a half-life of years, thus stopping the decay chain for practical purposes.