Kazutoshi Fujiwara

Applicability of Chemical Cleaning Process to Steam Generator Secondary Side, (I) Outline of the Investigation and Cleaning Effectiveness

The application of the chemical cleaning process to dissolve and remove scales and sludge by chemicals is being planned at the Japanese pressurized water reactor (PWR) plant in order to maintain a high heat transfer condition and to prevent the steam generator tube degradation. In this paper, fundamental characteristics and cleaning effectiveness of the EPRI process and the KWU process, which are typical cleaning processes, were investigated. Both processes showed a satisfactory cleaning effectiveness for sludges and scales, and the cleaning effectiveness of the standard KWU process was improved by tailoring it to crevice cleaning conditions.

Applicability of Chemical Cleaning Process to Steam Generator Secondary Side, (II)

The application of a chemical cleaning process to dissolve and remove scale and sludge by chemicals is being planned for Japanese pressurized water reactor (PWR) plants in order to maintain a high heat transfer condition and to prevent the SG tubing degradation. In this paper, the effectiveness of the EPRI process and the KWU process to maintain integrity of SG tubing were investigated under accelerated IGSCC conditions. IGSCC susceptibility and propagation ratio of degraded SG tubing with chemical cleaning, were the same as those of tubing not subjected to the chemical cleaning process. Neither the EPRI nor the KWU process adversely affected tubing integrity.

Thermal Decomposition of 3-Methoxypropylamine as an Alternative Amine in PWR Secondary Systems

The secondary coolant of pressurized water reactors is buffered to slightly alkaline pH by ammonia or amines in order to suppress corrosion. 3-Methoxypropylamine (MPA) is one of the promising alternative amines. The thermal decomposition of MPA was studied under two conditions: (i) a dissolved oxygen (DO) concentration of less than 5 ppb at 280°C for 1.5 h and (ii) a DO concentration of 20 ppb at 70°C for 2 h. The initial MPA concentration was 10 ppm. After the tests, concentrations of MPA and carboxylic acids were measured. Approximately 9 to 15% of MPA was decomposed after the tests. Carboxylic acid concentrations were as follows: (i) formate 110 ppb, acetate 260 ppb and propionate 400 ppb at 280°C, and (ii) formate less than 2 ppb, acetate 60 ppb and propionate 1270 ppb at 70°C. The reaction mechanism of MPA decomposition was estimated from the present experimental results. At 280°C, the hydrolysis of the ether bond initiates the decomposition, and the subsequent bond cleavage of C-N and/or C-C occurs. At 70°C, hydrogen abstraction by an oxygen molecule is the initiation reaction. MPA radicals and HO2 or C1 compounds propagate a chain reaction and result in a relatively high yield of propionate.

Applicability of Chemical Cleaning Process to Steam Generator Secondary Side, (III): Effect of Chemical Cleaning on Long Term Integrity of Steam Generator Tube after Chemical Cleaning Process

The application of the chemical cleaning process to dissolve and remove scales and sludge by chemicals is being planned at the Japanese pressurized water reactor (PWR) plant in order to maintain a designed heat transfer condition and to prevent the steam generator (SG) tube degradation. In this paper, the affects of the EPRI process and the KWU process on the long term integrity of SG tubing were investigated under the simulated SG condition using a SG model boiler test facility. No adverse effect of the both chemical cleaning processes on the long term integrity of SG tubing were observed.

Development of Pipe Wall Thinning Evaluation Method and Prediction Tool

Flow accelerated corrosion (FAC) and liquid droplet impingement erosion (LDI) are the main pipe wall thinning phenomena in piping system of power plants in Japan. Authors have promoted the development of prediction method to evaluate local thinning trend by FAC/LDI. To apply the method to pipe wall thinning management in power plants, it is required to be transformed into practical tools for easy usage. In Japan, discussion is being made to considerate the introduction of prediction tools into wall thinning management based on wall thickness measurement at present.Authors have simplified their FAC/LDI models to predict wall thinning trend one-dimensionally along piping layout, and applied to actual thinning data of power plants. With PWR’s FAC data and BWR’s LDI data, maximum thinning rate for each pipe elements were roughly predictable with considerable accuracy. Especially for high thinning rate data, which is important in plant management, the model was able to evaluate within the factor of 2. By installing this model, prediction software “FALSET” was developed, equipped with practical functions for the management. With the further verification and improvement of each function, there are prospects for this software to be utilized as a management tool in power plants.Copyright

Applicability of Chemical Cleaning Process to Steam Generator Secondary Side, (IV): Comprehensive Applicability Evaluation of Chemical Cleaning and Its Effect on Integrity of Other Structural Materials Other than Steam Generator Tubes

The application of chemical cleaning for dissolving and removing scale and sludge is being planned in the Japanese pressurized water reactor (PWR) plant in order to maintain high heat transfer performance and to prevent steam generator (SG) tube degradation. In this paper, the effectiveness of the Electric Power Research Institute (EPRI) and German Kraftwerk Union (KWU) processes on the integrity of structural materials other than SG tubes and the comprehensive applicability of chemical cleaning are discussed. The integrity of structural materials such as carbon steel, low-alloy steel and stainless steel was maintained after the EPRI and KWU processes. KWU chemical cleaning tailored for crevice cleaning has been studied to improve its cleaning effectiveness in crevices and to control the corrosion depth of structural materials less than the criterion for corrosion depth.

Corrosion behaviour of aluminium under simulated environmental conditions of low-level waste

ABSTRACT In Japan, low-level radioactive waste including aluminium alloys is generated from nuclear power plants. It is well known that aluminium reacts with both alkaline cement and water, generating hydrogen gas. For the safe management of radioactive waste disposal facilities, it is necessary to evaluate corrosion and hydrogen generation behaviours of aluminium corresponding to changing environmental conditions. In the present study, the corrosion behaviour of aluminium in alkaline solutions at 15 °C was evaluated. This paper is part of a supplement on the 6th International Workshop on Long-Term Prediction of Corrosion Damage in Nuclear Waste Systems.

1509 A Consideration of Schmidt Number in Flow Accelerated Corrosion

○ 金沢 知之(新潟大院) 伊藤 晃宏(新潟大院) 正 山縣 貴幸(新潟大) 正 藤澤 延行(新潟大) 正 藤原 和俊(電中研) 正 稲田 文夫(電中研) Tomoyuki KANAZAWA, Graduate School of Science Technology, Niigata University Akihiro ITO, Graduate School of Science Technology, Niigata University Takayuki YAMAGATA, Visualization Research Center, Niigata University Nobuyuki FUJISAWA, Visualization Research Center, Niigata University Kazutoshi FUJIWARA, Central Research Institute of Electric Power Industry Fumio INADA, Central Research Institute of Electric Power Industry

An in Situ Raman Spectroscopy System for Long-term Corrosion Experiments in High Temperature Water up to 673 K

A Raman spectroscopy system has been developed, in order to identify metal oxides formed on the surfaces of metals and steels in high temperature water up to 673 K. A supercritical water loop system including a Raman cell was installed. The design of the loop system is up to 673 K and 40 MPa. The Raman cell has a diamond window without window-to-metal packing. Raman spectrum of alumina plate was measured at room temperature, at 523 K and at 673 K under pressure of 25 MPa. A long-term measurement was also performed at 523 K and 25 MPa for 117.5 h. In all cases intense Raman peaks attributed to alumina were observed. Raman spectrum of anatase particles in suspension was measured at 673 K and 25 MPa. The results show that the Raman spectroscopy system developed in the present study works well not only for plate sample but also for suspension. Raman spectra observed for titanium plate in high temperature water of 673 K and 25 MPa show growth of several Raman peaks with time up to 257 h. The peaks disappeared after cooled down to room temperature. The experimental results have demonstrated importance of in situ Raman spectroscopy.