Source Range Channel

The BF3 proportional counter is used to monitor low power levels in a nuclear reactor. It is used in the "startup" or "source range" channels. Proportional counters cannot be used at high power levels because they are pulse-type detectors. Typically, it takes 10 to 20 microseconds for each pulse to go from 10% of its peak, to its peak, and back to 10%. If another neutron interacts in the chamber during this time, the two pulses are superimposed. The voltage output would never drop to zero between the two pulses, and the chamber would draw a steady current as electrons are being produced. 

Figure 35 shows a typical source range channel in functional form. 

Because of the unique conditions that exist during initial fuel loading, temporary neutron detectors may be used in the reactor pressure vessel to provide additional reactivity monitoring. Credit for the use of temporary detectors may be taken in meeting Tech-Specs requirements on the number of operable source range channels. 

Source range, Log N, and Picoammeter channels console power supplies. 

What one of the following types of nuclear detector is utilized with the start-up channel (source range) ... 

At 1 59 a,m the No. 1 AFW pump suction transferred spuriously from the condensate storage tank to the service water system (malfunction number 10). This action was not significant, but it had occurred before and had not been corrected. Similarly, a source range nuclear instrument became inoperable after the reactor trip (malfunction number 11) and the operators initiated emergency boration pursuant to procedures. (Note One channel had been inoperable prior to the event.) The source range instrumentation had malfunctioned previously and apparently had not been properly repaired. Also, the control room ventilation system tripped into its emergency recirculation mode (malfunction number 12), which had also occurred prior to this event. 

Li+ (0.77) < Na+ (1.0) < K+ (1.48) < Rb+ (1.55) < Cs+ (1.56). While indeed the order is the same, the significant point is that the range of discrimination has been expanded by almost an order of magnitude. The concern then becomes the mechanism whereby the Gramicidin channel effects this enhancement of selectivity. An important source of selectivity that must be considered is the relative solvation energy of water... 

We consider the problem of liquid and gas flow in micro-channels under the conditions of small Knudsen and Mach numbers that correspond to the continuum model. Data from the literature on pressure drop in micro-channels of circular, rectangular, triangular and trapezoidal cross-sections are analyzed, whereas the hydraulic diameter ranges from 1.01 to 4,010 pm. The Reynolds number at the transition from laminar to turbulent flow is considered. Attention is paid to a comparison between predictions of the conventional theory and experimental data, obtained during the last decade, as well as to a discussion of possible sources of unexpected effects which were revealed by a number of previous investigations. 

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