ABSTRACT
Under some unexpected conditions, drive rods and control-rod assemblies may not be disconnected. If this situation is not detected, the control rod will be lifted out of the reactor core together with the upper reactor internals. This situation will seriously affect the follow-up work and reduce the economy and safety protection of the nuclear power plant. To ensure safety, the tripping status must be checked after tripping. Follow-up work can be carried out after checking and confirming that all drive rods are in the tripping status. There are many problems for traditional inspection methods, such as misjudgment, low accuracy, and labor consumption. This paper proposes a visual inspection system for the uncoupling state of the control-rod drive rod of the nuclear reactor. The proposed method is based on the fitting model of the ellipse parameter of the drive-rod head and the height of the drive rod. The ellipse of the drive-rod head is firstly accurately detected. Then, a mathematical model between the ellipse parameter and the height of the drive rod is established. The measurement error caused by the swing of the head of the drive rod is eliminated. The accurate measurement of the height difference before and after the tripping of the drive rod is computed. Finally, the status of the uncoupling of the drive rod is judged according to the difference. Many experiments are carried out with our developed system. The experimental results show that the proposed system realizes remote operation, ensures the quality of trip-status inspection, improves work efficiency, and reduces the workload of staff.
Subject(s)
Nuclear Power Plants , Nuclear Reactors , HumansABSTRACT
BACKGROUND & AIMS: N-nicotinamide methyltransferase (NNMT) is emerging as an important enzyme in the regulation of metabolism. NNMT is highly expressed in the liver. However, the exact regulatory mechanism(s) underlying NNMT expression remains unclear and its potential involvement in alcohol-related liver disease (ALD) is completely unknown. METHODS: Both traditional Lieber-De Carli and the NIAAA mouse models of ALD were employed. A small-scale chemical screening assay and a chromatin immunoprecipitation assay were performed. NNMT inhibition was achieved via both genetic (adenoviral short hairpin RNA delivery) and pharmacological approaches. RESULTS: Chronic alcohol consumption induces endoplasmic reticulum (ER) stress and upregulates NNMT expression in the liver. ER stress inducers upregulated NNMT expression in both AML12 hepatocytes and mice. PERK-ATF4 pathway activation is the main contributor to ER stress-mediated NNMT upregulation in the liver. Alcohol consumption fails to upregulate NNMT in liver-specific Atf4 knockout mice. Both adenoviral NNMT knockdown and NNMT inhibitor administration prevented fatty liver development in response to chronic alcohol feeding; this was also associated with the downregulation of an array of genes involved in de novo lipogenesis, including Srebf1, Acaca, Acacb and Fasn. Further investigations revealed that activation of the lipogenic pathway by NNMT was independent of its NAD+-enhancing action; however, increased cellular NAD+, resulting from NNMT inhibition, was associated with marked liver AMPK activation. CONCLUSIONS: ER stress, specifically PERK-ATF4 pathway activation, is mechanistically involved in hepatic NNMT upregulation in response to chronic alcohol exposure. Overexpression of NNMT in the liver plays an important role in the pathogenesis of ALD. LAY SUMMARY: In this study, we show that nicotinamide methyltransferase (NNMT) - the enzyme that catalyzes nicotinamide degradation - is a pathological regulator of alcohol-related fatty liver development. NNMT inhibition protects against alcohol-induced fatty liver development and is associated with suppressed de novo lipogenic activity and enhanced AMPK activation. Thus, our data suggest that NNMT may be a potential therapeutic target for the treatment of alcohol-related liver disease.
