Question

Radiolytic decomposition of water on the coolant side of zirconium cladding is generating a pressure of H2 of 10-4 bar with thus a similar surface concentration of H2. Hydrogen, H2, is thus diffusing into the zirconium, which can in fact contain a considerable amount of dissolved hydrogen. Using the data and assumptions below, and other information you may need to gather from other sources, and assuming
 The cladding is uniformly at 400 degrees C
 PWR reactor pressure is 1800 psi
 The cladding is pure Zr
 The cladding is 1 mm in thickness
 There is a sink for hydrogen at the inner clad thus the H2 pressure is negligible
 The diffusion coefficient is described by
ln D = ln A – Ea/RT
where
D = diffusion coefficient
A = pre-exponential factor (7.9 x 10-3 cm2/s)
Ea = activation energy for diffusion (44900 J/mol)
R = ideal gas law constant
T = absolute temperature
a. Compute the flux of hydrogen into the cladding at steady state
b. Sketch the concentration profile across the cladding
c. More realistically, zirconium can react with hydrogen to form zirconium hydride, ZrH2. Determine whether we will see hydride formation in the cladding.

Answer 1