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INL reports findings on unusual quantum behavior of plutonium
Scientists at Idaho National Laboratory have discovered that plutonium hexaboride (PuB6) displays a type of unusual quantum property called a topological Kondo insulating state. Materials with this property are neither typical electricity conductors nor regular insulators. Rather, they have exterior surfaces that strongly conduct electricity and interiors that block electricity.
Young A. Choi, Madeline Anne Feltus
Nuclear Technology | Volume 111 | Number 1 | July 1995 | Pages 115-121
Technical Note | Reactor Operation | doi.org/10.13182/NT95-A35150
Articles are hosted by Taylor and Francis Online.
Reliability-centered maintenance (RCM) methods are applied to boiling water reactor plant-specific emergency core cooling system probabilistic risk assessment (PRA) fault trees. The RCM is a technique that is system functionbased, for improving a preventive maintenance (PM) program, which is applied on a component basis. Many PM programs are based on time-directed maintenance tasks, while RCM methods focus on component condition-directed maintenance tasks. Stroke time test data for motor-operated valves (MOVs) are used to address three aspects concerning RCM: (a) to determine if MOV stroke time testing (as required by Section XI of the American Society of Mechanical Engineers Code) was useful as a condition-directed PM task; (b) to determine and compare the plant-specific MOV failure data from a broad RCM philosophy time period compared with a PM period and, also, compared with generic industry MOV failure data; and (c) to determine the effects and impact of the plant-specific MOV failure data on core damage frequency (CDF) and system unavailabilities for these emergency systems. The MOV stroke time test data from four emergency core cooling systems [i.e., highpressure coolant injection (HPCI), reactor core isolation cooling (RCIC), low-pressure core spray (LPCS), and residual heat removal/low-pressure coolant injection (RHR/ LPCI)] were gathered from Philadelphia Electric Company’s Peach Bottom Atomic Power Station Units 2 and 3 between 1980 and 1992. The analyses showed that MOV stroke time testing was not a predictor for eminent failure and should be considered as a go/no-go test. The failure data from the broad RCM philosophy showed an improvement compared with the PMperiod failure rates in the emergency core cooling system MOVs. Also, the plant-specific MOV failure rates for both maintenance philosophies were shown to be lower than the generic industry estimates. A significant decrease in CDF was found when comparing the plant-specific data with the generic data. Only a small difference in CDF was found between plant-specific RCM data compared with PM data, which can be attributed to the few number of essential MOVs modeled in the HPCI, RCIC, RHR/LPCI, and LPCS PRA fault trees.