A nuclear chain reaction occurs when one single nuclear reaction causes an average of one or more subsequent nuclear reactions, thus leading to the possibility of a self-propagating series of these reactions. The specific nuclear reaction may be the fission of heavy isotopes (e.g., uranium-235, 235U). The nuclear chain reaction releases several million times more energy per reaction than any chemical reaction.
https://en.wikipedia.org/wiki/Nuclear_chain_reaction
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The lead-cooled fast reactor is a nuclear reactor design that features a fast neutron spectrum and molten lead or lead-bismuth eutectic coolant. Molten lead or lead-bismuth eutectic can be used as the primary coolant because lead and bismuth have low neutron absorption and relatively low melting points. Neutrons are slowed less by interaction with these heavy nuclei (thus not being neutron moderators) and therefore, help make this type of reactor a fast-neutron reactor. The coolant does, however, serve as a neutron reflector, returning some escaping neutrons to the core. Fuel designs being explored for this reactor scheme include fertile uranium as a metal, metal oxide or metal nitride.[1] Smaller capacity lead-cooled fast reactors (such as SSTAR) can be cooled by natural convection, while larger designs (such as ELSY[2]) use forced circulation in normal power operation, but with natural circulation emergency cooling. The reactor outlet coolant temperature is typically in the range of 500 to 600 °C, possibly ranging over 800 °C with advanced materials for later designs. Temperatures higher than 800 °C are high enough to support thermochemical production of hydrogen through the sulfur-iodine cycle.
https://en.wikipedia.org/wiki/Lead-cooled_fast_reactor
09-27-2021-1747 - radioactive elements such as plutonium is complicated by the fact that solutions of this element can undergo disproportionation[11] and as a result many different oxidation states can coexist at once.
radioactive elements such as plutonium is complicated by the fact that solutions of this element can undergo disproportionation[11] and as a result many different oxidation states can coexist at once.
https://en.wikipedia.org/wiki/Radiochemistry
Radiochemistry includes the study of both natural and man-made radioisotopes.
Main decay modes[edit]
All radioisotopes are unstable isotopes of elements—undergo nuclear decay and emit some form of radiation. The radiation emitted can be of several types including alpha, beta, gamma radiation, proton and neutron emission along with neutrino and antiparticle emission decay pathways.
1. α (alpha) radiation—the emission of an alpha particle (which contains 2 protons and 2 neutrons) from an atomic nucleus. When this occurs, the atom's atomic mass will decrease by 4 units and atomic number will decrease by 2.
2. β (beta) radiation—the transmutation of a neutron into an electron and a proton. After this happens, the electron is emitted from the nucleus into the electron cloud.
3. γ (gamma) radiation—the emission of electromagnetic energy (such as gamma rays) from the nucleus of an atom. This usually occurs during alpha or beta radioactive decay.
These three types of radiation can be distinguished by their difference in penetrating power.
Alpha can be stopped quite easily by a few centimetres in air or a piece of paper and is equivalent to a helium nucleus. Beta can be cut off by an aluminium sheet just a few millimetres thick and are electrons. Gamma is the most penetrating of the three and is a massless chargeless high energy photon. Gamma radiation requires an appreciable amount of heavy metal radiation shielding (usually lead or barium-based) to reduce its intensity.
hemical form of the actinides[edit]
The environmental chemistry of some radioactive elements such as plutonium is complicated by the fact that solutions of this element can undergo disproportionation[11] and as a result many different oxidation states can coexist at once. Some work has been done on the identification of the oxidation state and coordination number of plutonium and the other actinides under different conditions.[2] This includes work on both solutions of relatively simple complexes[12][13] and work on colloids[14] Two of the key matrixes are soil/rocks and concrete, in these systems the chemical properties of plutonium have been studied using methods such as EXAFS and XANES.[15][3][4]
Movement of colloids[edit]
While binding of a metal to the surfaces of the soil particles can prevent its movement through a layer of soil, it is possible for the particles of soil which bear the radioactive metal can migrate as colloidal particles through soil. This has been shown to occur using soil particles labeled with 134Cs, these have been shown to be able to move through cracks in the soil.[16]
Action of microorganisms[edit]
The action of micro-organisms can fix uranium; Thermoanaerobacter can use chromium(VI), iron(III), cobalt(III), manganese(IV) and uranium(VI) as electron acceptors while acetate, glucose, hydrogen, lactate, pyruvate, succinate, and xylose can act as electron donors for the metabolism of the bacteria.
https://en.wikipedia.org/wiki/Radiochemistry
09-27-2021-1746 - recognised a small spike at an energy of 803 kilo-electron volts (keV) as the gamma ray signal from polonium-210
Scientists at AWE were involved in testing for radioactive poison after the poisoning of Alexander Litvinenko. No gamma rays were detected; however, the BBC reported that a scientist at AWE, who had worked on Britain's early atomic bomb programme decades before, recognised a small spike at an energy of 803 kilo-electron volts (keV) as the gamma ray signal from polonium-210, a critical component of early nuclear bombs, which led to the correct diagnosis. Further tests using spectroscopy designed to detect alpha radiation confirmed the result.[11]
https://en.wikipedia.org/wiki/Atomic_Weapons_Establishment
https://en.wikipedia.org/wiki/Convair_XF-92
https://en.wikipedia.org/wiki/Lead-cooled_fast_reactor
https://en.wikipedia.org/wiki/Angle_of_attack
https://en.wikipedia.org/wiki/Point-defence
Monday, September 27, 2021
09-27-2021-1739 - modulated neutron initiator
A modulated neutron initiator is a neutron source capable of producing a burst of neutrons on activation. It is a crucial part of some nuclear weapons, as its role is to "kick-start" the chain reaction at the optimal moment when the configuration is prompt critical. It is also known as an internal neutron initiator. The initiator is typically placed in the center of the plutonium pit, and is activated by impact of the converging shock wave.
One of the key elements in the proper operation of a nuclear weapon is initiation of the fission chain reaction at the proper time. To obtain a significant nuclear yield, sufficient neutrons must be present within the supercritical core at the right time. If the chain reaction starts too soon ("predetonation"), the result will be only a 'fizzle yield', well below the design specification, therefore low spontaneous neutron emission of the pit material is crucial. If it occurs too late, the core will have begun to expand and disassemble into a less-dense state, leading to a lowered yield (less of the core material undergoes fission) or no yield at all (the core is no longer a critical mass).
For boosted fission weapons, the size of the centrally placed initiator is critical and has to be as small as possible. The use of an external neutron source allows more flexibility, such as variable yields.
https://en.wikipedia.org/wiki/Modulated_neutron_initiator
The two graphite-moderated reactors, referred to at the time as "piles", had been built as part of the British post-war atomic bomb project. Windscale Pile No. 1 was operational in October 1950 followed by Pile No. 2 in June 1951.[4]
https://en.wikipedia.org/wiki/Windscale_fire
https://en.wikipedia.org/wiki/Chernobyl_disaster
https://en.wikipedia.org/wiki/Scaling_(geometry)
https://en.wikipedia.org/wiki/Reflection_(mathematics)
https://en.wikipedia.org/wiki/Norm_(mathematics)#Zero_norm
https://en.wikipedia.org/wiki/Uncorrelatedness_(probability_theory)
https://en.wikipedia.org/wiki/Quaternions_and_spatial_rotation#Quaternion-derived_rotation_matrix
https://en.wikipedia.org/wiki/Reflection_symmetry
https://en.wikipedia.org/wiki/Graphite-moderated_reactor
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