An experimental study to link water chemistry with corrosion product deposits in-reactor

A wide range of water chemistries have been used in a series of experiments in a water loop in the NRX reactor at Chalk River, Ontario to expand our understanding of corrosion product deposition and release in-core, in both boiling and non-boiling water. The water chemistry was varied by changing the pH additive (LiOH, NH4OH),the pH, the dissolved hydrogen concentration, and the particulate concentration. As well, unique designs of fuel strings explored the effects of water velocity, surface heat flux, and reactor and fuel pellet radiations on deposition and release of corrosion products. Heavy deposits (up to 40 g Fe/m2) were formed by crystal growth. In the absence of crystal growth only light deposits (<0.1 g Fe/m2) were formed by particle deposition and indicate release by dissolution. Results of the tests are consistent with published data for the effects of pH and temperature on the solubility of magnetite, the major corrosion product in the deposits. (author)