Neutron radiation level indication

Health Physics Laboratory. The health physics laboratory is located at the entrance to the radiation sources controlled area (Figure 2). From this laboratory the access to the radiation sources area is monitored and controlled. The health physics laboratory is equipped with portable beta, gamma, and neutron survey meters of various designs and ranges to facilitate the area monitoring, air monitors for airborne contamination, and anticontamination equipment. It is equipped with monitors and alarms for the area radiation detectors, pool water level indicators, and access doors. It also has ready access to the counting equipment of the radiochemistry laboratory. 

Ageing effects may be detected by a change in measurable parameters. For example, increase in temperature or pressure may be an indication of die accumulation of corrosion products in the tube of a heat-exchanger and instrument drift may be an indication of electronic component degradation. Parameters should be measured periodically in a consistent manner and the readings should be compared and assessed. Physical parameters, such as temperature, pressure, flow rate, control rod drop times, radiation level (e.g. neutron and gamma), water quality, are indicators of the state of a system, structure or component. 

Sometimes the radiation level detector (especially when the more sensitive neutron back-scatter devices are used) will falsely indicate that the water level in the coke drum has risen to the correct level. Apparently, the level detector is fooled by the increasing density of steam as the coke cools. 

The Li resonances were observed by Johnson et the peaks in both total cross section and reaction cross section are shown in Fig. 15. A similar peak is found in the total cross section of Li" (Stelson and Preston ). The inelastic scattering of neutrons by Li" has been studied by Freeman et al., who detected radiation from the 478 keV level. The shape of the excitation curve just above threshold depends on the orbital momenta of the ingoing and outgoing neutron waves and in this case indicates a strong s-wave contribution to the reaction. This type of reaction would be expected to show resonances of the compound nucleus as for other inelastic processes, and evidence for this is given by Kiehn and Goodman for scattering from Al . ... 

Spin dependence of level density. In the previous section we have shown that the radiation widths in a given nucleus should be independent of the spin of the levels. In making this deduction it was assumed that the density of levels with spin / was (2 / +1) times the density of levels with zero angular momentum. However, this is not the only condition for the spin independence of the radiation widths the radiation widths will also be independent of spin if the densities of all levels at a given energy are the same regardless of spin and provided that 7 1. A crucial test is provided by a study of the radiation widths of the levels produced by slow neutron capture by nuclei with spin In this case the levels have spins 0 or 1 and a constant radiation width independent of spin can be produced only by the condition coj= 2j- -i)coQ, This seems to be confirmed by measurements of the radiation widths of the Ag resonances which indicate that the radiation widths are the same to an accuracy of 10% whether the spins are 0 or 1. To some extent this is corroborated by the fact that the majority of the resonances for which the spins have been determined (in either isotope) have spin 1. 

---