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Collaborating Authors
Results
Effects Of Eta, Ph Change, And Increased Hydrazine Levels On Deposit-Covered Alloy 600 And Brass Corrosion
Barkatt, Aaron (The Catholic University) | Labuda, Ewa (The Catholic University) | Wilder, Donna M. (The Catholic University) | Smialowska, Susan (The Ohio State University) | Rebak, Raul B. (The Ohio State University) | Cherepakhov, Gahna (Consolidated Edison Co. of New York, Inc) | Bums, Reynolds J. (Consolidated Edison Co. of New York, Inc)
ABSTRACT Chemical dissolution tests and electrochemical tests were carried out on Alloy 600 specimens covered with synthetic deposit simulating the tube deposits in the steam generators at Indian Point 2. The tests showed that the introduction of ETA and a moderate increase in pH gave rise to lower corrosion rates, but enhancement of hydrazine levels caused them to rise. In the case of brass, both types of tests showed that raising the pH caused the corrosion rates to increase, but the introduction of ETA led to mild decrease in these rates. INTRODUCTION in recent years many nuclear plants implemented changes in secondary water chemistry in an effort to minimize corrosion in the secondary system and to reduce the extent of transport of iron into steam generators. Until the late 80’s, most plants used ammonia to control the pH of secondary water. Most recently, advanced amines, such as morpholine and ethanolamine (ETA) were introduced. These amines are less volatile than ammonia, and therefore they are more effective in maintaining a high pH at steam generator temperatures. However, it was recognized that the implementation of advanced amine chemistry requires evaluation of its consequences on a site-specific basis, taking into account the materials of construction and the past and present operating conditions in individual plants. The Indian Point 2 Station is a 995-MWe PWR with four Model 44 Westinghouse steam generators. It started operations in 1973. Many of the original components of the secondary system were made out of copper alloys (admiralty brass, cupronickel). Although many of these components were later replaced by stainless steel or titanium components, the low-pressure heaters and one condenser still consist of copper-based materials. In addition, much copper (some of it in oxide form) is still present in deposits and sludge accumulated in the steam generators. accumulation of relatively large amounts of sludge and deposits in the steam generators. Some of the accumulated material is quite hard. The build-up of sludge has required lancing during each refueling outage since the beginning of operations. However, tube corrosion has been limited to mild pitting. No secondary-side SCC has been observed. Through the 1995 outage, only about 9% of the total number of tubes have been plugged. More significantly, less than 6% of the tubes have required plugging since the start of full-power operation. The specific features of the secondary system (presence of copper, sludge build-up, mild corrosion) had to be taken into account during the evaluation of the introduction of ETA into the secondary system at Indian Point 2. In particular, it was necessary to find out whether ETA might cause enhanced dissolution of the brass components or of the accumulated deposits and hard sludge. Dissolution of the latter materials is undesirable, because microstructural examination by SEM/EDX and radiotracer migration studies showed that the deposits and hard sludge form barriers to the migration of corrosive species such as sulfate, chloride, and lead.
- Energy > Power Industry (1.00)
- Materials > Chemicals > Commodity Chemicals > Petrochemicals (0.95)
- Water & Waste Management > Water Management > Water & Sanitation Products (0.93)
- (2 more...)
Evaluation Of Thermal Decomposition Rate Of Carbohydrazide And Its Reducing Effect On Carbon Steel Corrosion
Fujiwara, Kazutoshi (Central Research Institute of Electric Power Industry) | Kawamura, Hirotaka (Central Research Institute of Electric Power Industry) | Hirano, Hideo (Central Research Institute of Electric Power Industry) | Takahashi, Karrjo (Kyushu Electric Power Co,. Inc.) | Maeda, Toshihiko (Kyushu Electric Power Co,. Inc.) | Kolke, Masami (Kyushu Electric Power Co,. Inc.)
ABSTRACT Hydrazine as an oxygen scavenger has been widely used for the feed water treatment of PWR secondary side and fossil power plants in the world. However, there is some concern over health and safety issues related to use of hydrazine. Carbohydrazide is listed up as one of alternative oxygen scavengers. In this study, laboratory tests were performed to examine the thermal decomposition rate of carbohydmzide and its reducing effect on carbon steel corrosion in comparison with hydrazine. Test results revealed that carbohydrazide was stable below 373K. The thermal decomposition ratios of carbohydrazide were less than 50% after 20 minutes exposure in the range of 373K to 428K. Its thermal decomposition rate constant was derived from experimental test data. The measurement of dissolved oxygen concentration also showed that carbohydrazide possessed a fairly good oxygen scavenger property. Judging from test results mentioned above, it was concluded that carbohydmzide is applicable as an alternative oxygen scavenger for feedwater treatment in PWR and fossil power plant. INTRODUCTION It is well known that hydrazine possesses excellent reducing action and oxygen scavenging property. Hydrazine as an oxygen scavenger has been widely used for the feedwater treatment of PWR secondary side and fossil power plants in the world. Recently, PWRS have operated with All Volatile Treatment (AVT) employing high hydrazine content water chemistry. It is reported that the use of hydrazine as a scavenger of trace quantities of dissolved oxygen reduce the corrosion of balance-of-plant materials in the recommended pH range in PWRs. High hydrazine water chemistry is expected to yield a reduction in the corrosion product transport to the steam generators. However, there is some concern over health and safety issues related to use of hydrazine. Carbohydrazide is listed up as one of safety substitute of hydrazine. Carbohydrazide has replaced hydmzine in 20% of the United States electric utility industry. Moreover, it is reported that the reducing action and oxygen scavenging property of carbohydrazide is comparable with that of hydrazine, and that in particular, at low temperature, its oxygen scavenging property is superior to that of hydrazine. In USA, some good results concerning the corrosion restriction effect of carbohydrazide has been reported .On the other hand, the result of electrochemical measurements at Kewanuee Nuclear Power Plant shows carbohydrazide has no deleterious effect. However, the fundamental property of carbohydrazide, such as thermal decomposition rate, reducing action and oxygen scavenging property, has not been adequately clarified. In this study, the thermal decomposition rate of carbohydrazide was determined by using the autoclave apparatus, absorption spectrophotometry and so on. The effect of carbohydmzide on the lowering of dissolved oxygen concentration and the corrosion of carbon steel is also mentioned by comparing with the reducing effect of hydrazine. EXPERIMENTAL PROCEDURES Chemical component of scavenger and pretreatment of test specimen The ELIMIN-OX consisting of diluted carbohydrazide ((N2H)2CO), the trade name of chemical agent patented by Nalco Chemical Company, was used as an oxygen scavenger. 60% hydrated hydmzine is also used as an oxygen scavenger.
- Water & Waste Management > Water Management (1.00)
- Materials > Chemicals (1.00)
- Energy > Oil & Gas > Upstream (1.00)
- Energy > Power Industry > Utilities > Nuclear (0.68)
ABSTRACT Previous tests showed type 316 stainless compression fittings can crack when exposed to NACE TMO177 solution at elevated temperatures for 30 days. Following up this finding, one-month, three-month and twelve month tests have been conducted on type 316 compression fittings and instrumentation tubing in order to assess their suitability for sour service. Loops were constructed, containing a total of over three hundred fittings from four manufacturers and filled with sour fluids comprising high chloride content solutions. They were pressurised to 50 bara (5MPa) with CO2 and H2S partial pressures in the range 0-0.8 bara (8kPa) and maintained at temperatures in the range 60- 120ºC . The tests showed that even in mildly sour conditions, at elevated service temperatures cracking can occur and that the threshold H2S partial pressure decreases with increasing temperature. INTRODUCTION Compression fittings are widely used in pressure and vacuum systems in a number of industries including chemical processing, nuclear power and oil and gas production. Of the fitting designs available, those based on twin ferrule arrangement are most popular in the oil and gas industry. Fittings typically are double ended, when used to join tubes (of the same or different size) or have a tube end and a specialised fitting for connecting to pressure gauges, manifolds etc. In making up a joint the nut is tightened, which causes the front ferrule and then the rear ferrule to bite, skive or swage into the tube this is how the pressure rating is achieved. The tube end deforms and barrels out ahead of the front ferrule, to an extent governed by its wall thickness. Sealing can occur at a number of locations, depending on the design (the various manufacturers claim unique design aspects) and the quality of workmanship. If the tube is cut neatly end the joint made up carefully, sealing can be achieved between the cut end of the tube and the internal shoulder in the fitting. However, at least two leading manufacturers consider that the internal process fluid will contact the tip and front face of the front ferrule. In order to function, certain components including the front ferrule must be harder than the tubing. In the 316 austenitic stainless steel system it is recommended that the tubing be fully annealed (80 HRB max). The ferrules are much harder, typically in the range 30-47 HRC. Prior to 1990 NACE MRO175 did not address the issue of compression fittings. Type 316 stainless steel was listed with a hardness limitation of 22 HRC for sour service. In the North Sea, as reservoir souring occurred, a number of operators with facilities designed for sweet service recognised that upgrading was required. Among these facilities was the Ninian field. Since 316 compression Wings had components with hardness well in excess of the 22 HRC, an attempt was made to clarify the meaning of MRO175, resulting in the addition of paragraph 8.4.1.1. Simultaneously, work undertaken by Cortest demonstrated that such fittings are susceptible to cracking in severe.
- North America > United States (0.68)
- Europe > United Kingdom > North Sea > Northern North Sea (0.24)
- Europe > United Kingdom > North Sea > Northern North Sea > East Shetland Basin > Block 3/8 > Ninian Field > Brent Group Formation (0.99)
- Europe > United Kingdom > North Sea > Northern North Sea > East Shetland Basin > Block 3/3 > Ninian Field > Brent Group Formation (0.99)