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Since the reactor pressure vessel (RPV) lower head failure determines the subsequent ex-vessel accident progression, it is a key issue to understanding the accident progression of the Fukushima Daiichi Nuclear Power Station (1F). The RPV failure is largely affected by thermal loads on the vessel wall, and thus, it is inevitable that the thermal behavior of the molten metallic pool with the co-existence of solid oxide fuel debris must be understood. In past decades, numerous experiments have been conducted to investigate homogeneous molten pool behavior. Few experiments, however, address the melting and heat transfer process of the debris bed consisting of materials with different melting temperatures. The LIVE-J2 experiment aims to provide experimental data on a solid-liquid mixture pool in a simulated RPV lower head under various conditions. The experiment was performed in the LIVE-3D facility at the Karlsruhe Institute of Technology. The LIVE-J2 experiment started from the end state of the previous LIVE-J1 experiment where a eutectic binary mixture of KNO3-NaNO3 (nitrate) was solidified and filled the gap of the ceramic beads inside the LIVE-vessel. The information obtained in the LIVE-J2 experiment includes transient and steady-state melting temperature and vessel wall temperature distributions. The extensive measurements of the melting temperature indicate the heat transfer regimes in a solid-liquid mixture pool. The test results showed that the conductive heat transfer is dominant during steady state along the vessel wall boundary and that convective heat transfer takes place inside the mixture pool. After the addition of liquid nitrate on top of the mixture pool, different behavior was observed in each layer. In the upper pure-liquid nitrate layer, convective heat transfer was well developed, resulting in a homogeneous temperature, while within the lower solid/liquid debris mixture zone a large temperature gradient was observed, suggesting that conductive heat transfer was dominant. Besides the experimental performance, the test case was numerically simulated using Ansys Fluent. The simulation results generally agree with the measured experimental data. The flow regime and transient melt evolution were able to be estimated by the calculated velocity field and the crust thickness, respectively. [ABSTRACT FROM AUTHOR]

Core melt solidification phenomena in the lower plenum of pressurized reactor vessel during external reactor vessel cooling is investigated in late in-vessel phase experiment tests under different external cooling conditions and melt pouring positions. The melt solidification behavior, which has not yet been given sufficient attention, is an important issue since it influences not only the transient but also the steady state of melt pool thermal hydraulics. A noneutectic melt (80 mol % KN[O.sub.3]-20 mol % NAN[O.sub.3]) was used to simulate the core melt. It has been found out that when the vessel is cooled with water during the whole test period (water cooling), the cooling is more effective than the case that the vessel lower head is first cooled with air and flooded by water (air/water cooling). Water cooling at the beginning leads to faster buildup of crust layer on the vessel inner wall and lower crust thermal conductivity compared with air/water cooling. In comparison with the air/water cooling, the water cooling also achieves shorter time period of crust growth. During the solidification period in all tests, the constitutional supercooling condition is fulfilled. Pouring position near the vessel wall results in considerable asymmetry, in the heat flux distribution through the vessel wall. [DOI: 10.1115/1.400108l] Keywords: core melt, in-vessel, crust, solidification, lower head, heat flux, IVR, PWR, PRV

Background: Analysis of ventricular late potentials (LP) with signal-averaged ECG (SAECG) using three bipolar, orthogonal X,Y, Z leads is a validated method of risk-stratification in patients prone to ventricular tachycardia. The aim of this study was to validate a ECG system, which allows LP analysis using X,Y, Z leads mathematically derived from the standard 12-lead ECG.Methods and Results: In 36 patients (age 56 +/- 12 years, coronary artery disease 71%, LVEF 46 +/- 14%) with known or suspected ventricular tachyarrhythmia, two consecutive SAECGs were recorded, one with mathematically derived and another one with true X,Y, Z leads. Time domain measurements with these different lead systems were compared using linear regression analysis and "Bland-Altman" plots. Correlation was good (r = 0.92) for the filtered QRS complex duration, but poor for the terminal QRS amplitude (RMS) and duration (LAS) criteria (r = 0.66 and 0.61, respectively; P < 0.0001). Defining LPS as present if at least two of the three time domain criteria were abnormal, the result matched in 28 (78%), but differed in 8 (22%) patients.Conclusion: SAECG using X,Y, Z leads mathematically derived from the standard 12-lead ECG compared to true bipolar X,Y, Z leads show a close correlation in filtered QRS duration, but can differ considerably in the other time domain measurements, resulting in different interpretation of LP analysis in 22%. Therefore, SAECG registration should currently be performed with true X,Y, Z leads, until the accuracy of other approaches is validated. [ABSTRACT FROM AUTHOR]

Questions Under Study: Many patients with atrial fibrillation (AF), risk factors for stroke and no obvious contraindications do not receive oral anticoagulation. Estimations of the increased rate of stroke due to neglected anticoagulation, particularly in an elderly, non-selected population, are unknown., Methods: Consecutive patients with paroxysmal or permanent atrial fibrillation admitted to the medical or surgical department of our hospital for any reason were studied. Risk factors for stroke and contraindications for anticoagulation were recorded. Estimations of the increased rate of cerebrovascular events due to neglected anticoagulation were based on data of a large meta-analysis. Patients were further stratified into different age and risk groups., Results: 484 patients with a mean age of 75 (12) years were studied, 45% were female. 237 patients had no oral anticoagulation at hospital discharge, despite guideline recommendations. Contraindications for anticoagulation were found in 85 (36%) of these patients, resulting in 152 patients with neglected anticoagulation (31% of all patients with AF). We estimated that, if all those patients would have been treated according to guidelines, 7.4 strokes per year could be prevented in the study population. The estimated rate of preventable events was 4.9%/year (7.4/152)., Conclusions: With better adherence to guidelines for oral anticoagulation in patients with atrial fibrillation and risk factors for stroke, a significant number of strokes could be prevented.

Objective: To assess the feasibility and longterm outcome of cardiac resynchronization therapy (CRT) in patients with impaired left ventricular function (LVEF <35%), left bundle branch block (QRS >120 ms) and dyspnoea NYHA 0 III at a single centre., Methods and Results: Forty-seven patients were referred for implantation of a CRT device. In only 4 patients (9%) the device could not be implanted due to technical problems during the procedure. In the remaining 43 patients (65 +/- 10 years; 7 female) a CRT device was implanted. Follow-up time was 12 +/- 10 months. Twenty-one patients had dilated cardiomyopathy (DCM) and 22 patients had coronary artery disease (CAD). NYHA functional class improved from 3.0 +/- 1.4 to 2.5 +/- 0.7 (p <0.0001), accompanied by an improvement of LVEF [median 20% (range 15-25) vs 32% (range 20-40); p <0.0001]. A significant reduction of hospitalisation time for heart failure was found when the year before and the year after device implantation [18 days (range 5-27) vs 1 day (range 0-3); p <0.0001] were compared. Twelve (28%) patients, 9 with CAD, and 3 with DCM died. Two CAD patients and all patients with DCM who died had a combined CRT device with implantable cardioverter/defibrillator., Conclusion: In patients with severely impaired LVEF and wide QRS due to LBBB, CRT is feasible and safe. It improved dyspnoea and LVEF and reduced hospitalisation stays for heart failure during long-term follow-up.