[en] In a recent paper, selected results of a comprehensive review and evaluation of service water system problems conducted by the Office for Analysis and Evaluation of Operational Data (AEOD) of the US Nuclear Regulatory Commission (NRC) were presented. The results of this review and evaluation indicated that service water system problems have significant safety implications. These system problems are attributable to a great variety of causes and have adverse impacts on a large number of safety-related systems and components. To provide additional feedback of operating experience, this paper presents an overview of the dominant mechanisms leading to service water system degradations and failures. The failures and degradations of service water systems observed in the 276 operating events are grouped into six general categories. The six general categories are (1) fouling due to various mechanisms, (2) single-failure and other design deficiencies, (3) flooding, (4) equipment failures, (5) personnel and procedural errors, and (6) seismic deficiencies

[en] The evaporator recycle streams contain waste in a chemistry and temperature regime that may be outside of the current waste tank corrosion control program, which imposes temperature limits to mitigate caustic stress corrosion cracking (CSCC). A review of the recent service history (1998-2008) of Tanks 30 and 32 showed that these tanks were operated in highly concentrated hydroxide solution at high temperature. Visual inspections, experimental testing, and a review of the tank service history have shown that CSCC has occurred in uncooled/un-stress relieved F-Area tanks. Therefore, for the Type III/IIIA waste tanks the efficacy of the stress relief of welding residual stress is the only corrosion-limiting mechanism. The objective of this experimental program is to test carbon steel small scale welded U-bend specimens and large welded plates (12 x 12 x 1 in.) in a caustic solution with upper bound chemistry (12 M hydroxide and 1 M each of nitrate, nitrite, and aluminate) and temperature (125 C). These conditions simulate worst-case situations in Tanks 30 and 32. Both as-welded and stress-relieved specimens have been tested. No evidence of stress corrosion cracking was found in the U-bend specimens after 21 days of testing. The large plate test is currently in progress, but no cracking has been observed after 9 weeks of immersion. Based on the preliminary results, it appears that the environmental conditions of the tests are unable to develop stress corrosion cracking within the duration of these tests

[en] The Office for Analysis and Evaluation of Operational Data (AEOD) of the U.S. Nuclear Regulatory Commission (NRC) has completed a comprehensive review and evaluation of service water system failures and degradations observed in operating events in light water reactors from 1980 to 1987. The review and evaluation focused on the identification of causes of system failures and degradations, the adequacy of corrective actions implemented and planned, and the safety significance of the operating events. The results of this review and evaluation indicate that service water system failures and degradations have significant safety implications. These system failures and degradations are attributable to a great variety of causes and have adverse impact on a large number of safety-related systems and components that are required to mitigate reactor accidents. Specifically, the causes of failures and degradations include various fouling mechanisms (sediment deposition, biofouling, corrosion and erosion, pipe coating failure, calcium carbonate, foreign material and debris intrusion); single failures and other design deficiencies; flooding; multiple equipment failures; personnel and procedural errors; and seismic deficiencies. Systems and components adversely impacted by a service water system failure or degradation include the component cooling water system, emergency diesel generators, emergency core-cooling system pumps and heat exchangers, the residual heat removal system, containment spray and fan coolers, control room chillers, and reactor building cooling units

[en] A comprehensive review and evaluation of service water system failures and degradations observed in operating events in light water reactors from 1980 to 1987 has been conducted. The review and evaluation focused on the identification of causes of system failures and degradations, the adequacy of corrective actions implemented and planned, and the safety significance of the operating events. The results of this review and evaluation indicate that the service water system failures and degradations have significant safety implications. These system failures and degradations are attributable to a great variety of causes, and have adverse impact on a large number of safety-related systems and components which are required to mitigate reactor accidents. Specifically, the causes of failures and degradations include various fouling mechanisms (sediment deposition, biofouling, corrosion and erosion, pipe coating failure, calcium carbonate, foreign material and debris intrusion); single failures and other design deficiencies; flooding; multiple equipment failures; personnel and procedural errors; and seismic deficiencies. Systems and components adversely impacted by a service water system failure or degradation include the component cooling water system, emergency diesel generators, emergency core cooling system pumps and heat exchangers, the residual heat removal system, containment spray and fan coolers, control room chillers, and reactor building cooling units. 44 refs., 10 figs., 5 tabs

[en] The effects of decoupling a multimass subcomponent from a large structure are examined. An attempt is made to correlate the effects of decoupling with the modal mass of the subcomponent. Two methods are used to study these effects: (1) Determining the effect of the inertia of the subcomponent on the motion of the primary component. This effect is evaluated by studying the change in the spectrum response of the motion input to the substructure and (2) Investigating the effect of decoupling the multimass system on the natural frequencies of the system

[en] Potential safety concerns associated with water-hammer occurrences in operating nuclear power plants are primarily related to the frequency and severity of the water-hammer occurrences, the level of damage incurred due to hydraulic loads, and the safety function of the system involved. These safety concerns were evaluated by the US Nuclear Regulatory Commission (NRC) in the course of resolving Unresolved Safety Issue (USI) A-1, Water Hammer. Since the resolution of USI A-1, an additional 40 water-hammer events have been reported (from 1981 through 1985). This study was initiated by the Office for Analysis and Evaluation of Operational Data to evaluate these recently reported water-hammer events to assess the underlying causes and adequacy of the corrective actions taken to prevent recurrence. The data compiled in this study show that 18 of the reported water-hammer events occurred at boiling water reactors (BWRs) and 22 of the events occurred at pressurized water reactors (PWRs). The results indicate that the BWR systems most susceptible to water hammers continue to be the residual heat removal (RHR) and high-pressure coolant injection systems. Flow into voided (or partially voided) lines and steam-water entrainment continue to be the most frequently cited underlying causes for BWR water-hammer events. The results show that the PWR systems most susceptible to water hammer are the feedwater system and the steam generators

[en] The growing interest in the physics of fluidic flow in nanoscale channels, as well as the possibility for high sensitive detection of ions and single molecules is driving the development of nanofluidic channels. The enrichment of charged analytes due to electric field-controlled flow and surface charge/dipole interactions along the channel can lead to enhancement of sensitivity and limits-of-detection in sensor instruments. Nuclear material processing, waste remediation, and nuclear non-proliferation applications can greatly benefit from this capability. Atomic force microscopy (AFM) provides a low-cost alternative for the machining of disposable nanochannels. The small AFM tip diameter (< 10 nm) can provide for features at scales restricted in conventional optical and electron-beam lithography. This work presents preliminary results on the fabrication of nano/microfluidic channels on polymer films deposited on quartz substrates by AFM lithography.

[en] In Hong Kong, electricity is supplied by two private utilities: Hongkong Electric and CLP Power (CLP). Both are regulated under the Scheme of Control (SOC). The SOC is a formal, long-term regulatory contract of 15 years, signed between a private firm and the Hong Kong Government. Under the SOC, the two electric utilities are subject to both rate-of-return control and price control. The current scheme will expire by 2008. In this paper, we propose a gradual and cautious approach to the introduction of market reform into the electricity industry in Hong Kong. For regulated markets, the government should consider replacing the SOC with performance-based regulation for wire businesses and the non-contestable market. For competitive markets, the government should consider introducing competitive tendering for new sources in the generation market and liberalising the supply market in phases

[en] An experimental investigation of the effects of vapor environments on the corrosion of aluminum spent nuclear fuel (A1 SNF) has been performed. Aluminum cladding alloys and aluminum-uranium fuel alloys have been exposed to environments of air/water vapor/ionizing radiation and characterized for applications to degradation mode analysis for interim dry and repository storage systems. Models have been developed to allow predictions of the corrosion response under conditions of unlimited corrodant species. Threshold levels of water vapor under which corrosion does not occur have been identified through tests under conditions of limited corrodant species. Coupons of aluminum 1100, 5052, and 6061, the US equivalent of cladding alloys used to manufacture foreign research reactor fuels, and several aluminum-uranium alloys (aluminum-10, 18, and 33 wt% uranium) were exposed to various controlled vapor environments in air within the following ranges of conditions: Temperature -- 80 to 200 C; Relative Humidity -- 0 to 100% using atmospheric condensate water and using added nitric acid to simulate radiolysis effects; and Gamma Radiation -- none and 1.8 x 10⁶ R/hr. The results of this work are part of the body of information needed for understanding the degradation of the A1 SNF waste form in a direct disposal system in the federal repository. It will provide the basis for data input to the ongoing performance assessment and criticality safety analyses. Additional testing of uranium-aluminum fuel materials at uranium contents typical of high enriched and low enriched fuels is being initiated to provide the data needed for the development of empirical models

[en] The evaporator recycle streams of nuclear waste tanks may contain waste in a chemistry and temperature regime that exceeds the current corrosion control program, which imposes temperature limits to mitigate caustic stress corrosion cracking (CSCC). A review of the recent service history found that two of these A537 carbon steel tanks were operated in highly concentrated hydroxide solution at high temperature. Visual inspections, experimental testing, and a review of the tank service history have shown that CSCC has occurred in uncooled/un-stress relieved tanks of similar construction. Therefore, it appears that the efficacy of stress relief of welding residual stress is the primary corrosion-limiting mechanism. The objective of this experimental program is to test A537 carbon steel small scale welded U-bend specimens and large welded plates (30.48 x 30.38 x 2.54 cm) in a caustic solution with upper bound chemistry (12 M hydroxide and 1 M each of nitrate, nitrite, and aluminate) and temperature (125 C). These conditions simulate worst-case situations in these nuclear waste tanks. Both as-welded and stress-relieved specimens have been tested. No evidence of stress corrosion cracking was found in the U-bend specimens after 21 days of testing. The large plate test was completed after 12 weeks of immersion in a similar solution at 125 C except that the aluminate concentration was reduced to 0.3 M. Visual inspection of the plate revealed that stress corrosion cracking had not initiated from the machined crack tips in the weld or in the heat affected zone. NDE ultrasonic testing also confirmed subsurface cracking did not occur. Based on these results, it can be concluded that the environmental condition of these tests was unable to develop stress corrosion cracking within the test periods for the small welded U-bends and for the large plates, which were welded with an identical procedure as used in the construction of the actual nuclear waste tanks in the 1960s. The absence of evidence of stress corrosion cracking and general corrosion in the laboratory-scaled specimens indicate that this type of nuclear waste tank is not susceptible to highly caustic solutions up to 12 M hydroxide at 125 C when sufficient nitrite inhibitor is present.