Booster rods

For a natural uranium reactor, where the possible excess reactivity is limited by the low value, it may not be possible to overcome the peak in the transient, and it will then be necessary to wait for some time after the peak is reached before the reactor can be started up again. One way of avoiding such a situation, employed in the CANDU heavy water reactor, is the use of booster rods of enriched uranium which can be inserted into the core to provide a temporary increase in reactivity. For any reactor with a limited capacity for xenon override, it is desirable to restart after an unscheduled reactor trip as soon as possible, before the xenon transient has had a chance to build up. The re-establishment of the xenon burn-out due to restoring the operational flux level then allows the equilibrium xenon concentration to be regained without any large change in the reactivity having taken place. 

An additional facility, used both for adjusting the flux shape for optimum peak-to-average ratio and to overcome the xenon transient following a trip from power, consists of 18 adjuster rods which may be inserted vertically between the calandria tubes. Cobalt is used as the absorber in the adjuster rods because of the commercial value of the radioisotope produced by irradiation. An alternative method of overcoming the xenon transient, which has been adopted for the subsequent Bruce generating station, is the use of booster rods containing enriched fuel. 

A feature of Gentilly is the use of enriched uranium booster rods to add reactivity during startup, in order to compensate for the negative reactivity effect of power increase. It was found that the insertion of the booster rods could result in a local reactivity imbalance which was amplified by the positive power coefficient. The result was the initiation of a side-to-side flux tilt, occurring in a time of the order of minutes, which, if uncorrected, could cause overrating of the fuel. To prevent this, the flux and power distributions... 

Holland et al (Ref 11) reported that when single crysts of PETN were initiated by means of a chge of Comp B, the velocity started at 5560m/sec and then suddenly changed to 10450 while accompanied by observable radiation in the interior of the crystal. Then a final, apparently steady vel was established at 8280 m/sec. The "dark waves" observed in deton of single crysts of PETN arose at the periphery of the deton wave and preceded failures of the deton process. In a typical experiment a rod of PETN of diam 0.252 inch and 0.438 inch long was wrapped with brass foil for a distance of 0.287 inch from the boostered end. The foil seemed to prevent the occurrence of dark waves in the 1st part of the stick, but.when the deton wave passed the foil, it was choked off by dark waves (See also Ref 13, p 202)... 

A powdered sample is put into a polyethylene tube, then into the steel tube. A booster is placed on the upper surface of the sample, and the mass of sample is recorded. A wooder rod 6.8mm in diameter is inserted into the hole on the booster to enable the insertion a detonator, and the cover is tighted by hand. A detonator is inserted into the hole of the booster from the hole in the cover, and the tube is placed horizontally in the sand at a depth of 60cm. 

In processing of liquid systems, such as dewatering of slurries and pasty materials, piezoelectric or magnetostrictive generators are used. The active part of such a generator (called a driver) generates and transmits mechanical vibrations via a solid rod (a booster) to the metal profile (a horn). This horn serves as an amplitude transformer to amplify the displacement of the driver and to match the transducer impedance with the impedance of the material to be processed (Figure 13.7). The mechanical vibrations from the horn are further coupled to the material processed either directly (the horn is inserted into a liquid or pasty material) or indirectly via a membrane. 

This mode of core cooling was adequate until about 6 00 p.m., when loss of control air prevented further manual control of the remaining (4 out of 11) operable pressure-relief valves. The valves closed, and pressure in the vessel started building up again. As pressure increased above 2.4 MPa (350 psi), the condensate booster pumps could no longer inject water into the vessel and thus only the control-rod-drive-system pump was adding water. 

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