In-pile PWR loop coolant chemistry studies in support of dose reduction

In a project supported by the Electric Power Research Institute and the Empire State Electric Energy Research Corporation, an in-pile loop capable of close simulation of PWR primary coolant system conditions has been constructed and operated at MIT to evaluate chemistry control strategies which can reduce radioactive corrosion product deposition, and hence radiation doses to maintenance personnel. Seven one-month-long runs have been completed, in which LiOH and H3BO3 additions were varied to evaluate the effect of pH. Runs at pH 300degC = 6.5, 7.0, 7.2 and 7.5 were carried out. End-of-run corrosion product and radionuclide deposits were assayed as a function of position. The results are in accord with a solubility-controlled mechanism for transition metal transport, showing a substantially higher activity deposition at low pH (6.5), and a weak minimum between pH 7.0 and 7.5. (author)