Oldbury vessel

The percentage difference is still within 5-8%. A further comparison is given in Fig. 5.21 which is based on the monitoring of the vessel s performance for a period of 10 years. 

At a pressure of 4.665 MN/m (I.TSPgd), a wider and deeper plastic zone appeared (mark 6) in the top cap. It is interesting to note that the top haunch plastic zone has also been increased. In addition, a minor plastic zone has been predicted by FE at the bottom cap haunch. Moreover, at the upper part of the side wall a wider radial crack has occurred and this crack has also been confirmed by the model tests. 

Reports suggest that a horizontal-cum-radial crack has appeared above the circulator penetration, but the published data have not confirmed it. In the 

Carrying on in the same way, many failure zones have been developed at additional incremental pressures. As shown in Fig. 5.13 at Pg, ultimate = 1197 MN/m (4.5Fgd), both model tests and FE results are in agreement. The vessel top cap and top comer have been separated. 

This failure mechanism is different from that predicted for the Dungeness B vessel, although they both have an identical shape and reactor system layout but with different prestressing system and gas design pressure. 

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Fig. 5.18 Horizontal deflection of wall (ultimate pressure) - Oldbury vessel...

Fig. 5.20 Presure-deflection curye of Oldbury vessel [418 experimental]...

Equation (5.42a) can be used directly for the HTGCR and Hartlepool vessels. For the Dungeness B and Oldbury vessels, equation (5.42a) is reduced to... 

In the Oldbury vessel a slight variation to the above equations is necessary for computing forces and moments. As stated in both the top and bottom caps of the Oldbury vessel the tendons are arranged horizontally in layers which form a square mesh in plan view. As shown in Figs. 5.55 and 5.56 both top and bottom caps are divided into slices. Equations are modified to include the term... 

Brown A. H. The Oldbury vessels. Conference PCPV. Paper 1 Group A, March (1967). Paper I Group A, (1967). (b) Harris A. J. and Hay J. D. Rupture design of the Oldbury vessels. Conference PCPV. Paper No. 29, Group F, 1967. 

A computer program has been developed to determine these movements under constructional and operational conditions. A separate computer program is written to plot these movements using an plotter associated with IBM 7500. Finally, the theoretical model is tested against short-term partial experimental results obtained from Dungeness, Oldhury and Hartlepool vessels. The results for the Oldbury vessel are given in the text. 

Fig. AIC.l (a),(b) Finite element idealisation of Oldbury vessel 20-node element, complete bay with spring locations...

Movement parameters for the Oldbury vessel, obtained from the theoretical model and from site measurements, are plotted in Fig. AIC.2 and AIC.3 for critical locations of this vessel. 

However, the Oldbury contractors carried out optimisation studies on the UK Hinkley B and Hunterston B power stations. Slight changes in the vessel parameters were inevitable. This time true helices were adopted for the prestressing tendons rather than the barrelised type adopted for the Oldbury... 

Typical layouts of the Dungeness B, Oldbury and HTGCR vessels are given in Figs. 5.1, 5.2 and 5.3, respectively. Figures 5.4, 5.5, 5.6 and 5.7 show the finite element mesh layout of the Dungeness B, Oldbury, Hartlepool and HTGCR vessels, respectively. 

The experimental tests have been carried out on two pressure vessel models, namely that of Dungeness B and Oldbury, both cylindrical with top and bottom flat caps, with different prestressing systems, indicate different modes of failure. These will be the reference models of the limit state analysis which has been developed in the text and which will be finally provided by using 3D hybrid finite element analysis under increasing gas load pressure. The Oldbury will be given a detailed assessment later on in the text. 

The linear, non-linear and cracking analyses mentioned earlier are useful to predict the operational and overload behaviours of the vessels. Four vessels, namely the Dungeness B, Oldbury, Hartepool and Fort St. Vrain have been analysed. Figures 5.13, 5.14, 5.15, 5.16, 5.17, 5.18, 5.19 and 5.20 give a summary of the load displacement relations, modes of cracking and failure and the safety margins. Cracks predicted by the finite element and limit state... 

Fig. 5.13 Oldbury prestressed concrete reactor pressure vessel...

Fig. 5.21 Hoop and axial strains at wall mid-height - Oldbury reactor vessel (conditions at ultimate pressure) (----, finite (five-parameter) —O—, experimental)...

In this case Pm-P(s, the second term on the left-hand side of equation ( is zero for the Oldbury and the Dungeness B vessels. The value of T, the radial component of force from the circumferential tendons or bands, is given by... 

However, principal stresses and consequently the eraeks they cause, may appear in a number of different positions depending upon the relative magnitudes of loads, moments and shear carried by the seetion. Significant differences oecur among isolated cap tests and full model tests. Reported ultimate load tests for Oldbury and Bungeness B vessels eonsider each vessel to be initially broken up into an open-ended cylinder and two end slabs. The mechanisms of this initial break-up, however, appear to be in disagreement with each other. For the Oldbury analysis, the slab was separated from the barrel by a plastic hinge at the junction of the slab and barrel. 

Fig. AIC.2 Absolute movements of Oldbury reactor vessel where...

Figure 11.7. Oldbury under construction. This was the first station to use pre-siressed concrete for the pressure vessel rather than steel.

Oldbury introduced a new concept into the gas-cooled stations. Instead of a steel pressure vessel, pre-stressed concrete would be used instead. This was cheaper, simpler, quicker to build, and, as much as anything, safer. Steel pressure vessels can fail catastrophically, but a reinforced concrete dome will not. 

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