Neutron continued prompt

The product nuclei as initially formed are highly unstable isotopes and emit delayed neutrons as well as electrons and gamma photons while settling down into their stable configurations, which ate usually isotopes of different elements from those first formed. The neutrons, both prompt and delayed, continue the reaction by encountering other fissionable nuclei... 

INAA and thermal neutron capture prompt y-ray activation analysis (PGAA) were used to this end. Unopened units were shown to have stable dry weight bases and stable mass fractions. The concentrations measured in this study for Al, As, B, Br, Ca, Cl, Co, Cu, Fe, K, Mg, Mn, Mo, Na, Rb, S, Se, and Zn were in very good agreement with the certified or consensus values, which justifies their continued use for QC purposes. 

Two elemental analyzer systems have been developed, the "Continuous On-line Nuclear Assay of Coal", CONAC, (Science Application, Inc., Palo Alto, CA) and "The Elemental Analyzer" (MDH Industries, Inc., Monrovia, CA). Both of these units are based upon the measurement of prompt gamma rays that are emitted from a nucleus following the capture of a neutron. This technique is commonly known as prompt neutron activation analysis, PNAA. 

If it is assumed that a "start-up accident" occurs in which rods are -withdrawn continuously at a rate equivalent to Ak/k 0.1% per second, the neutron level will rise only a factor of 100 in several minutes. However, at the end of this time the reactor will be supercritical, on a rising period oif approximately 10 sec, and in a few more seconds will have a period of approximately 1 sec. Under these conditions the reactor will have passed prompt... 

Prompt fission neutrons are emitted with the continuous energy spectrum shown in Figure 2.7. The spectrum spans an energy range of approximately 10 MeV, from less than 1 10 MeV. The average prompt neutron energy is about 2 MeV. 

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