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Water chemistry data acquisition, processing and evaluation systems have been applied in major Japanese PWRs and BWRs to prepare for reliable and quick data accumulation with saving in manpower in plant chemical laboratories and to establish smooth and reliable information transfer from chemists to plant operators and supervisors. The following features of the systems were noted.(1) X-ray fluorescence analyses and ion chromatography were widely applied in automatic chemical analysis procedures. (2) Water chemistry data were stored in PC base-data storage systems along with other major plant data to evaluate reliabilities of the data themselves and to prepare for official documents. (3) Clear data displays were effectively applied to support quick response to instances of fuel leakage and long-term analysis for better understanding of the plant's own water chemistry responses. (4) Evaluation of SG tubing integrity is successfully carried out by estimating crevice pH based on ion chromatographic data. (5) Application of in-situ high temperature water chemistry sensors is still restricted in laboratories. Only ECP monitoring has been applied for BWR hydrogen water chemistry. Plant diagnosis systems have been applied in only restricted areas and so serve limited purposes due to the lower benefit against cost.

The new decontamination process, T-OZON was applied to the decontamination of PLR pump impellers and bearings with casing covers. As the results, it was confirmed T-OZON was effective to reduce dose rate and secondary waste. The results make the further applications of T-OZON process on the decontamination for equipment disposal and system decontamination for primary coolant loops.

The properties of metal corrosion, such as the corrosion rate and corrosion expansion rate, are key factors for assessing the long term performance of the subsurface disposal system. In this study, transient changes in pH were first simulated using a finite difference computer code. In the second step, the consumption times of the residual oxygen in the facility after the backfill were calculated. Finally, the supply of dissolved oxygen in the groundwater to the engineered barrier and the corrosion amount resulting from it were estimated. A high pH of around 12?5 would persist at least for 105 years inside the low permeability layer (LPL). In addition, the results suggest that the rate of oxygen supply in the form of dissolved oxygen in the groundwater was very small due to the restriction of mass transport by the LPL and the low diffusivity layer. Thus, the environment in which aerobic corrosion extremely limited was found to be of long duration. This strongly suggests that, for assessing the long term performance of the engineered barrier system, anaerobic corrosion will have to be evaluated carefully.