Evaluation of corrosion product transport in the secondary plant of a pressurised water reactor

Abstract

In this study, the total amount of transported iron corrosion products during startup was evaluated. This was done by simultaneous collection of particulate and soluble iron samples using a 0.45 μm nitro-cellulose and a 0.45 μm resin impregnated filters respectively. Samples were collected at predetermined frequencies of 2 hrs, 4 hrs, 8 hrs, 16 hrs, 24 hrs and 48 hrs below 30 % reactor power, followed by 11 days startup basis after which a 7 days sampling period was followed for the entire duration of the fuel cycle. Samples were acid digested followed by determination of total iron concentrations using atomic absorption spectrophotometer (flame). The results were used to estimate iron transport amounts for each sampling period, from which a cumulative curve was constructed, and a regression equation worked out. The startup transport amounts for < 30 % reactor power period defined as time zero and for a defined period of 11 days were determined to be 5.443 kg (+/- 1.709) and 4.08 kg respectively, giving a total startup amount of about 9.84 kg. Based on comparison with other nuclear power plants, it was concluded that 9.84 kg is within the range as reported across industry and as such, the current startup practices with respect to their effect on corrosion product transport are generally of no concern. It was further concluded that, it is important to establish adequate redox chemistry conditions early in the startup period to promote magnetite (Fe3O4) formation to minimize iron transport.