Neutron continued delayed

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... 

Directly following the shutdown of the system and for a period of approximately thirty minutes thereafter, there are fissions continuing in the active portion of the reactor due to the release of delayed neutrons. Some of the... 

The first consequence of the above results is that the equations satisfied by the expected values N and C are exactly those which arise by considering N and C to be ordinary continuous functions of time and by considering all processes to occur at average rates. Other consequences concern the fluctuations. It is seen, for example, that equilibrium values exist for all quantities in the case of a subcritical reactor, Ic < I, or kp Icd < 1. For no delayed neutrons, these are... 

Assay by continuous uniform motion of components has several advantages over the incremental mode. It provides a detailed profile as well as an integral assay of fissionable isotopes for safeguards purposes. It also minimizes errors due to delayed neutrons, especially those due to transport of precursors in fissionable components. 

The high-density iimer pyrolytic carbon (IPyC) layer protects the kernel and buffer from chemical attack by chlorine compounds, which are generated as byproducts during deposition of the silicon carbide (SiC) layer. The IPyC layer also provides a surface for deposition of the SiC layer and delays transport of radionuclides to the SiC layer. The IPyC layer shrinks with the accumulation of fast neutron fluence, which helps to maintain the SiC layer in compression, provided the bond between the IPyC and SiC layers remains strong and continuous during irradiation. 

Thermal-hydraulics design of the clad failure detection system. This system is used to detect possible clad failures in the fuel subassemblies while the plant is operating. Clad failure causes a release of fission products emitting delayed neutrons, that are transported to the hot plenum and to the detectors. In SPXl the detector itself is placed outside the hot plenum with a continuous poped sampling system for analysis of the primary sodium was set up other systems in which neutron detectors are placed near the intermediate heat exchanger inlets and enabled activity to be measured directly, have been studied. In both cases thermal-hydraulics studies were necessary to measure the hydraulic transfer functions between the various core... 

The size and composition of the reactor are chosen to be such that the system would be supercritical in the absence of the control rods. The fuel is loaded with the control rods inserted and, on the completion of loading, the control rods are slowly raised, increasing the thermal utilization until criticality is attained. If the control rods are then withdrawn by a further small amount, increasing to a value slightly above unity, the system will be supercritical and the neutron density in the reactor, and hence the fission rate, will increase continuously. Once the desired power level has been attained, the rods are readjusted to restore the system to the critical condition, and the power will remain steady at the chosen level. As has been mentioned earlier, the only reason why the rate of power increase can be held to a practicable value is the existence of delayed neutrons the dynamics of reactor control will be discussed in detail in Chapter 3. 

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