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Key Factors in Bolted Joint Failure
Published in Randy Riddell, Practical Root Cause Failure Analysis, 2022
Bolt torque execution is very important. For bolt circle applications an even tightening around a bolt circle, such as a star pattern. Ramp up the bolt torque for each pass, such as 30%, 60% and a final 100% of the final target torque. On a rotating bolted element, rotate after each torque pass to even out the bolt preload.
In-Canal Assay of High Specific Activity 60Co at the Advanced Test Reactor
Published in Nuclear Technology, 2022
Michael A. Reichenberger, Jagoda M. Urban-Klaehn, Jason V. Brookman, Joshua L. Peterson-Droogh, Jorge Navarro, Richard H. Howard
The sensitivity factor was then applied to the measured response from the irradiation targets. However, differences between the standard and target geometries must also be considered. The most significant difference comes from the self-attenuation experienced in the source because of heterogeneities in the material. For example, a standard capsule may be constructed of solid cobalt, encapsulated in an aluminum container. However, it is more likely that the standard is composed of many small cobalt pellets that are inside a container. The effective density of the standard in this case, which was also the cast at the ATR, will be less than the density of solid cobalt. This difference was accounted for in Monte Carlo particle transport models by assuming that the material is still homogeneous but that the density is equal to the actual mass of cobalt in the radiation standard divided by the volume that is taken up by the material. Another important difference in self-attenuation comes from variations in the standard and target designs. It is unlikely that the standard will have exactly the same dimensions as the target. At the ATR, the irradiation targets are longer, have a smaller diameter, and have cobalt pellets stacked in 17 axial channels located on a bolt circle that is coaxially oriented with the target housing tube.17 The differences in the radiation standard and the irradiation target designs are depicted in Fig. 2. These differences in geometry mean that on a per-photon basis, there is a greater likelihood that the emitted photon deposits energy in the detector if it originated in the irradiation target than if it originated in the standard.
Design Studies for the Optimization of 238Pu Production in NpO2 Targets Irradiated at the High Flux Isotope Reactor
Published in Nuclear Technology, 2020
Charles R. Daily, Joel L. McDuffee
The radial centerlines of all seven pins depicted in Fig. 6 lie on a bolt circle radius (BCR) of 1.45 cm from the radial centerline of the VXF. The five-pin configurations were analyzed with all five pins lying on a BCR between ~1.12 and 1.35 cm. The seven-pin configurations were analyzed for BCRs between ~1.12 and 1.45 cm. By moving the targets farther away from or closer to the VXF liner, the amount of hydrogenous material (i.e., the H2O coolant) between the inner surface of the VXF liner and the outer surfaces of the target cladding tubes is altered, thus changing the neutron spectrum incident on the outer surfaces of the pellets in the various targets.
The square root rule – a case study of a scaling factor for machines with dynamic similitude
Published in Mechanics Based Design of Structures and Machines, 2020
Robert E. Farrell, Jiradech Kongthon
It can be seen by inspection of Eq. (17) that if a and b are both multiplied by the square root rule factor, the hoop stress remains the same. While the principal stress is the hoop stress, there is an axial stress superimposed but it is relatively small. The highest stress is normally a hoop stress in the bore at the front of the barrel. However, there is an end cap that is bolted to the end of the barrel and if the bolt circle is too close to the bore, cyclic stressing has caused fatigue cracks to be initiated at a bolt hole where the hoop stress is about 2.5 times the nominal value at that location.