High-Temperature Gas-Cooled Reactor Vessel HTGCR

2 High-Temperature Gas-Cooled Reactor Vessel (HTGCR) 

The vessel is then taken to elasto-plastic and cracking conditions. As discussed later on, the relationships between gas load, prestressing strains, and deflections and cracks with and without the influence of creep have been established. These results (Fig. 5.29) show that where the influence of creep is not considered, the load-carrying capacity is overestimated by as much as 25%. With creep, considerable changes were discovered in the cracking pattern of the vessel and the overstress conditions in local areas (standpipes and boiler/circu-lator penetrations). 

Ahmad has idealised the same vessel, as shown in Fig. 5.30. He has used the vessel bonded and unbonded and produced deformations (Figs. 5.30, 5.31, 5.32 and 5.33) for normal operation and for 40 years of creep. He has also produced a graph (Fig. 5.34) showing deformation for this vessel at various pressures. He has included creep in his analysis. This vessel has also been considered for elasto-plastic and cracking effects by Bangash. The deformation of the vessel at the cracking stage under the influence of creep and with the steel liner anchored to concrete is shown in Fig. 5.35. 

The stress trajectories at normal operation and at 2.5 times design pressures can be obtained in the same manner as for vessels discussed previously. The vessel design pressure GD here is 5.68 MN/m. At a pressure of 7.48 MN/m (1.315Pgd). this vessel s behaviour (Fig. 5.36) is identical to that of the Hartlepool vessel. The only change is the plastic zone developed around the gas inlet duct under mark 6. 

At a pressure of 9.28 MN/m (1.635Pgd) the behaviour of this vessel (Fig. 5.37) in most zones is identical to that of the Hartlepool vessel [423, papers H3/5, H5/3] and others. When the pressure was raised to 6 MN/m the only difference is in the position of cracks (marks 11, 12 and 13) at the top haunch and the extent of the plastic zones (marks 7,14,20,21 and 22). The crack sizes have not been predicted in the top cap. The bottom cap has been affected only at the bottom haunch. Both FE and M are in agreement in most areas, as shown in Fig. 5.37. Raising the pressure to 11.08 MN/m (1.95Pgd) there is a significant difference in the behaviour of this vessel (Fig. 5.38). 

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