Influence of preliminary thermomechanical load on the integrity of the vessel of Ukrainian nuclear reactors in case of accidents of "large" and "small" leak

In works of extending lifetime of WWER-type reactors, it is necessary to obtain the brittle fracture resistance (BF) of the reactor pressure vessel (RPV). Implementation calculations for brittle fracture resistance is regulated by the technical PNAE of Ukraine. The objective of these calculations is to prevent catastrophic brittle destruction of the reactor pressure vessel, pipelines and pressure vessels from the existence crack-like defects for all operating regimes, including emergency situations (ES). The paper considers the most dangerous postulated emergency situation in operation is "large" and "small" leak in the RPV NPP. Calculations with Warm Pre-Stressing effect (WPS) of the RPV for the most dangerous scenarios have been presented, and an assessment of the brittle strength of RPV NPP is taking into account with WPS. The results of studies with factor of brittle strength safety are also presented without taking into account the Warm Pre-Stressing, comparing with the existing method for accounting this type of load.

Pressure Activated Sealant to Restore Tubing Integrity – Case Study of Well Tn-X in Mahakam

Pressure activated sealant is used to repair tubing leak and restore tubing integrity without the need to install downhole devices which yield additional restriction inside tubing and reduce tubing ID. Leak on tubing was detected in early production phase from the continuous increase of A annulus pressure. The leak point was indicated from Production Logging Tool (PLT) at 183 m suspected from tubing thread connection, with annulus pressure buildup rate 435 psi/24 hrs. Pressure activated sealant was selected as the means to cure the leak. Retrievable plug was set below the leak point and sealant was pumped on top of plug, followed by inhibited water. Then pressure was applied at surface to squeeze and activate the sealant. The remaining fluid inside tubing remained liquid, allowing the plug to be retrieved. A total of 59 L sealant mixture and 750 L of inhibited water was pumped to the well. Hesitation pressure was performed to activate the sealant, and got indication of chemical sealing at 1000 psi. The tubing was then pressure tested to 5000 psi and pressure was holding in 1 hour, indicating positive isolation has been established between tubing-annulus. From continuous annulus pressure monitoring, pressure in A annulus has been stable at ~40 psi for the last 8 months after sealant injection has been performed. Pressure activated sealant is proven as a reliable method to cure small leak in tubing. Since the sealant will only be hardened inside the leaking point, there will be no additional restriction in the tubing, thus Internal Diameter (ID) reduction will not be a concern for future well intervention operations. Pressure activated sealant could become one of the alternatives to cure tubing leaks, especially in the cases where tubing ID reduction is not favored.

Acoustic Emission-Based Small Leak Detection of Propulsion System Pipeline of Sounding Rocket

For pipes connected by pipe joints, leaks in the pipeline system are likely to occur at the pipe joints as opposed to the tube itself. Thus, early detection is critical to ensure the safety of the pipeline system. Based on acoustic emission (AE) techniques, this paper presents an experimental research on small leak detection in gas distribution pipelines due to loosening of the pipe joint connection. Firstly, the acoustic characteristics of leak signals are studied; then, features of signals are extracted. Finally, a classifier based on the support vector machine (SVM) technology is established, and the qualified features are selected to detect the leak. It is verified that the main frequency of the AE small leak signal due to the failure of the pipe joint is focused in the range of 33–45 kHz, and the algorithms based on SVM with kernel functions all can reach a better estimation accuracy of 98% using the feature “envelope area” or the feature set {standard deviation (STD), root mean square (RMS), energy, average frequency}.

Management of severe haemolytic anaemia due to residual small mitral paravalvular leak post-percutaneous closure: a case report

Background Haemolytic anaemia is a complication of paravalvular leak (PVL). The correlation between the size of the leak and the severity of haemolysis is unclear. Small leaks can cause severe haemolysis, whereas significant leaks may cause no haemolysis. Case summary We report the case of a 40-year-old male who underwent mechanical mitral and aortic valve replacement 20 years ago. In the last 3 years, the procedure was repeated three times due to infective endocarditis. He presented with severe shortness of breath. A transoesophageal echocardiogram with three-dimensional surgical view showed that both discs of the mechanical mitral valve opened sufficiently but a severe PVL had occurred at the 9–12 o’clock position. The location of the mitral valve was abnormal, the sewing ring was inserted high at the mid-interatrial septum. The mechanical aortic valve functioned well. Closure of the transcutaneous PVL was accomplished with two percutaneously implanted devices, leaving a small leak in between. After closure, he developed haemolytic anaemia (haemoglobin: 6 g/dL, lactate dehydrogenase: 1896 units/L, reticulocyte count: 4.6%). He then received 16 units of packed red blood cells. He developed acute kidney injury and was started on haemodialysis. We then installed two additional devices to completely close the mild residual leak and another device to resolve the bidirectional transseptal defect. After 2 days, his renal function returned to normal and anaemia improved (haemoglobin: 9.1 g/dL). Discussion Mild residual paravalvular leak can cause severe haemolytic anaemia that is correctable via percutaneous closure of the leak.

Interdependence of flow and pipe characteristics in transient induced contamination intrusion: numerical analysis

Contaminant intrusion in pipelines during transients is a remarkable mechanism, which leads to a decline in the quality of the contained water. The negative pressure of water hammer pressure waves is the trigger for the suction of pollution from the surrounding leak area, and hence deteriorating water quality. The volume of contamination intruded into the pipeline is investigated using mathematical and numerical modeling of the phenomenon. To elucidate this phenomenon in real pipe systems, the intrusion amount is estimated for 72 different scenarios including: two lengths of pipeline (i.e. short and long), three different leak locations, three different fluid velocities in the pipe, two leak diameters and two pipeline materials (elastic and viscoelastic). The results showed that the amount of intrusion in viscoelastic pipes was clearly less than that in elastic pipes, especially in long pipelines. The critical zone of high intrusion risk is identified close to the downstream valve for small leak sizes, nevertheless, it is difficult to estimate this zone in the case of large leaks due to significant interactions between nodal components (valve, leak, reservoir).