Critical Reflections about Doel3 & Tihange2

Integrity reactor vessels Doel 3 and Tihange 2

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cooling at the time point when the hydrogen concentration is maximum in the future shell has to be estimated. Third, the hydrogen concentration in terms of temperature has to be estimated. At last, the hydrogen concentration in the cracked zone and in the non-cracked zone has to be estimated. The result will be that a significant hydrogen concentration has not occurred.

Figure 20: Position of the metal of the future shell inside the ingot.

1. Localization of the future shell in the ingot. The weight of the ingot is 110 tons and the result- ing shell about 50 tons ( [ 15 ] p17). The steps to manufature the shell are illustrated in paper [ 9 ] . During forging, the top and the bottom has been cut off, leaving a cylinder of 104 tons. Then the cylinder is compressed until its height is 2.5 m and the inner cylinder with 820 mm diameter has been pierced out, leaving a hollow cylinder of 94 tons. After forging, the resulting cylinder will be machined until it leaves a shell of 50 tons. By following back all these manufacturing steps, the position of the metal which will form the future shell is presented in figure 20. The dotted line represents the future shell in the ingot. Zone A will be the flaked zone, zone B will be free of flakes. All the other material will be removed during the manufacturing process. 2. Temperature drop over the ingot during cooling. During cooling, hydrogen will diffuse from the lower temperature zone towards the melt. The process starts with a uniform melt with 1.5 ppm hydrogen. The solidification starts at the ingot wall. The hydrogen concentration increases in the future shell by hydrogen coming from the outer part of the ingot. After some time, solidification has been progressed and reaches the radius which will become the inner wall of the future shell. At that time point, the hydrogen concentration will be maximum. As solidification further progresses, hydrogen will be diffused from the future shell further inward and the hydrogen concentration decreases. During forging, the core enriched with hydrogen will be pierced out. The maximum hydrogen concentration will be taken as the hydrogen concentration responsible for cracking. An estimate of the temperature gradient at the time point the melt core has reached the inner wall radius has been carried out. An ingot of 100 tons needs 24 hours to solidify ( [ 10 ] p13). During that time, it has to dissipate the heat of fusion and a part of the heat capacity of the solid ingot.

R.Boonen & J.Peirs

May 18, 2017