Some critical issues when applying electrochemical noise (EN) in field corrosion detection of nuclear materials are solved. In this work, a portable EN measurement system for field test is established by using Compact RIO modular instrument and zero resistance ammeter (ZRA) module. The electrode system for EN measurement is built by using platinum wire or stainless steels coated with thermal sprayed ceramic coatings as counter electrode. Two EN sensors are developed based on the electrode system mentioned above, and field corrosion detection is successfully achieved. The corrosion of stainless steel pipeline surface in nuclear power plant and internal-surface corrosion of continuous blowdown piping are successfully evaluated by the established new EN measurement system. 相似文献
The failure of T12 re-heater tubes that had been in service only for 3000 h was investigated. The wall thickness of the tubes was visibly reduced by heavy oxidation corrosion on the outer and inner walls. The original pearlite substrate completely decomposed. Uniform oxide scale appearance on the inner wall shows obvious vapor oxidation corrosion characteristics. Corrosion originated in the grain boundary, and selective oxidation occurred due to ion diffusion in the substrate. The layered oxide scale formed on the inner wall is related to the different diffusion rates for different cations. Exposure to high temperature corrosive flux accelerated the corrosion on the outer wall. The microstructure degradation and corrosion characteristics of the tubes indicate that the tubes failed primarily because of overheating, as evidenced by calculations. 相似文献
Unit testing is widely used in software development. One important activity in unit testing is automatic test data generation. Constraint-based test data generation is a technique for automatic generation of test data, which uses symbolic execution to generate constraints. Unit testing only tests functions instead of the whole program, where individual functions typically have preconditions imposed on their inputs. Conventional symbolic execution cannot detect these preconditions, let alone converting these preconditions into constraints. To overcome these limitations, we propose a novel unit test data generation approach using rule-directed symbolic execution for dealing with functions with missing input preconditions. Rule-directed symbolic execution uses predefined rules to detect preconditions in the individual function, and generates constraints for inputs based on preconditions. We introduce implicit constraints to represent preconditions, and unify implicit constraints and program constraints into integrated constraints. Test data generated based on integrated constraints can explore previously unreachable code and help developers find more functional faults and logical faults. We have implemented our approach in a tool called CTS-IC, and applied it to real-world projects. The experimental results show that rule-directed symbolic execution can find preconditions (implicit constraints) automatically from an individual function. Moreover, the unit test data generated by our approach achieves higher coverage than similar tools and efficiently mitigates missing input preconditions problems in unit testing for individual functions.
In this work, the passivation degradation of Alloy 800 on nucleate boiling surface was studied by using polarisation curve, electrochemical impedance spectroscopy and secondary ion mass spectrometry. Experimental results indicated that boiling bubble would significantly degrade the passive film, as indicated by a decreased pitting potential and increased passive current density. Under boiling condition, the mass transfer of electrolyte is accelerated and the temperature of Alloy 800 was increased, as a result, the cathodic reaction and the dissolution rate of the passive film were increased. The passive film was Cr-depleted but Ni- and Fe-enriched, and the decreased Cr content in the passive film led to a degraded passive film. 相似文献