Effects of process-generated hydrogen on RPV walls

Chapter 5 Hydrogen production in PWR 5.1 Introduction As the different sources of hydrogen in a PWR are explained above, a quantitative approach will be used to determine the amount of hydrogen formed in the reactor. This is done for each of the sources and will be combined afterwards to find the total hydrogen production rate in the PWR reactor pressure vessel. 5.2 Dissolved H 2 in primary water The dissolved H is an easy source of hydrogen in the system. The concentration of H in the primary water is held constant to avoid oxidizing conditions in the PWR primary system (see Section 4.2). It was found that the typical hydrogen gas concentration in the primary water is kept constant at 25 – 50 STP cm 3 /kg. Using Henry’s law the equilibrium partial pressure of H 2 in the reactor can be found. Back in 1989 Fernandez-Prini and Crovetto [55] have done a lot of research on the solubility of hydrogen gas in water at high temperature. Data of different research groups were compared and combined to find a model for the Henry constant of hydrogen gas in water as a function of temperature. It was found that the following empirical equation corresponds to the Henry constant for hydrogen gas in light water: [55] ln h H H 2 / GPa(mole fraction H 2 ) -1 i = A + B · T − 1 + C · T − 2 + D · T − 3 + E · T − 4 − T c − T T ln T c − T T c (5.1) with A = − 38 . 4512

B = + 53 . 4846 · 10 3 K C = − 27 . 4317 · 10 6 K 2 D = + 6 . 3522 · 10 9 K 3 E = − 559 . 0 · 10 9 K 4

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