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Requirements and Preparation for Passing the American Board of Health Physics Certification Examinations
Published in Kenneth L. Miller, of Radiation Protection Programs, 2020
Criticality accidents are possible whenever sufficient quantities of fissile materials are handled. Criticality accidents may be fatal but they are rare; the last fatal criticality accident in the U.S. took place at Woods River Junction in 1964; there was an injury-free criticality accident at INEL in 1978. Prevention of criticality accidents is not normally a part of a health physicist’s job, but it is worthwhile to understand the principles. Knief’s textbook98 is an excellent introduction to the subject. For the examination, a health physicist should understand the need for prompt warning and evacuation and other aspects of emergency preparedness. Preparations for a criticality accident include nuclear accident dosimeters, provisions for medical support, and decontamination facilities. For the examination it is important to be prepared to calculate doses, both from direct neutron and gamma radiation and from radionuclides released to the atmosphere. Regulatory Guide 3.34 may be helpful.99
Cooling during Fuel Removal and Processing
Published in Geoffrey F. Hewitt, John G. Collier, Introduction to Nuclear Power, 2018
Geoffrey F. Hewitt, John G. Collier
In a nuclear reactor, the fissile material is gradually used up and converted to energy and fission products. During the nuclear reaction there are changes in the microstructure of the fuel due to the release of fission products, which either combine with the fuel or are released inside the fuel can. These changes have two effects: (1) a gradual deformation of the fuel and in some cases the can and (2) the release of fission products (such as xenon and iodine), which are themselves strong absorbers of neutrons, leading to a reduction in neutron population and a less efficient nuclear reaction. For these reasons, the fuel element must be removed from the reactor after a period of time and before all the fissile material is used up. Typically this period will be between 3 and 5 years for thermal reactors and 1 year to 18 months for fast reactors. For thermal reactors, 60 to 75% of the original fissile material is used up at the time of fuel removal. For the fast reactor, the utilization is much less, of the order of 25%. The fraction utilized is often referred to as the burn-up.
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Published in Philip A. Laplante, Comprehensive Dictionary of Electrical Engineering, 2018
NuBus an open bus specification developed at MIT and used by several companies. It is a general-purpose backplane bus, designed for interconnecting processors, memory, and I/O devices. nuclear fuel fissile material, including natural uranium, enriched uranium, and and some plutonium prepared for use in a nuclear reactor. nuclear fuel management the process of managing the degree of enrichment, the timing of insertion into the core, and the placement and possible relocation of fuel within the core during the lifetime of the fuel. nuclear magnetic resonance the phenomenon in which the resonant frequency of nuclear spin is proportional to the frequency of an applied magnetic field. See magnetic resonance imaging. nuclear power plant a thermal electric power plant in which the heat for steam turbines is produced by nuclear fission. nuclear reaction a reaction which causes changes in the nucleus of an atom, thus changing elements to another element or isotope, usually with the release of energy. nuclear reactor (1) an apparatus designed to facilitate, contain, and control a nuclear chain reaction.
A Preliminary Proposal for a Hybrid Lattice Confinement Fusion–Fission Reactor for Mobile Nuclear Power Plants
Published in Fusion Science and Technology, 2022
Luciano Ondir Freire, Delvonei Alves de Andrade
Given its relative neutron abundance, the reactor may run on natural uranium and possibly breed fissile atoms from fertile materials. Except for 37Cl and 2H, it does not need large expenses on isotopic enrichment, like current reactor designs. Given its compactness, the quantity of isotopically enriched material is low compared to the CANDU design, yet it may use natural uranium. As the reactor does not need fuel element construction and enrichment, its cost is further lowered, even if fuel is not the major cost driver.
Evaluation of Discharged Fuel in Preproposed Breed-and-Burn Reactors from Proliferation, Decay Heat, and Radiotoxicity Aspects
Published in Nuclear Science and Engineering, 2020
Kazuki Kuwagaki, Jun Nishiyama, Toru Obara
Breed-and-burn (B&B) reactors are a special type of fast reactor. In such reactors, neutrons are provided to feed fuel consisting of natural or depleted uranium (fertile material), thus breeding fissile material. After a sufficient breeding level is achieved, the fuel can provide neutrons to the newly loaded feed fuel. Perpetuation of this breeding and neutron-providing process makes it possible to operate a B&B core with only a natural or depleted uranium feed fuel, except for the external fissile source required at initial startup.